Improved tin production

专利摘要:
A method is disclosed for separating, by fractional crystallization (300), a molten crude tin mixture (8) containing lead and silver into a first silver-enriched liquid draw-off product (9) at the liquid end of the crystallization step and a first tin enriched product (10) at the crystal end of the crystallization step with the first silver-enriched liquid draw-off product on a dry weight basis 6.0-30.0 weight% lead, 70.0-91 weight% tin, 95.0-99 , 0 weight% lead and tin together, 0.75-5.00 weight% silver, and ≥0.24 weight% antimony. Furthermore, a metal composition (9) is disclosed containing 6.0-30.0 wt.% Lead, 70.0-91 wt.% Tin, 95.0-15 99.0 wt.% Lead and tin together, 0.75 -5.00 wt% silver, and ≥0.24 wt% antimony.
公开号:BE1027001B1
申请号:E20205056
申请日:2020-01-30
公开日:2020-08-24
发明作者:Koen Govaerts；Pelle Lemmens；Jan Dirk A Goris；Visscher Yves De；Charles Geenen；Kris Mannaerts；Bert Coletti
申请人:Metallo Belgium；
IPC主号:

专利说明:

, Ç BE2020 / 5056 Improved tin production
FIELD OF THE INVENTION The present invention relates to the recovery of silver in the production of tin (Sn), optionally in combination with the production of copper (Cu) and lead (Pb), from primary sources and / or secondary base materials. More specifically, the present invention relates to the separation of silver from a molten crude tin mixture by fractional crystallization.
BACKGROUND OF THE INVENTION Silver is undesirable as a tin metal impurity. Significant presence of silver in tin metal deteriorates the mechanical properties of tin metal. The presence of silver in tin used in the tin plating of steel also creates the risk of galvanic corrosion, which would corrode the wall of the tin container from the inside to the outside surface. This is a major problem for cans for use in the food industry. Other end uses of tin can also be sensitive to impurities, as well as require a high purity tin quality. This applies, for example, to the preparation of high-quality lead-free solder, in the manufacture of semiconductor compounds such as tin nitride, antimony telluride, tin arsenide and superconducting alloys. Silver is also a metal with significant market value, usually much higher than the market value of the most common non-ferrous metals, such as copper and lead, and even tin. Silver can be found in small quantities in the commercially available base materials of other non-ferrous metals, such as copper, lead and / or tin, and in particular in secondary base materials for these metals.
However, the concentrations of silver in the nonferrous metals-containing streams in the pyrometallurgical refining steps in copper and / or lead production are very low, usually far too low to justify their separate recovery. Applicants have found that when tin is present in the pyrometallurgical refining of copper and / or lead and the recovery of enriched tin streams is part of the same process, silver metal may tend to follow the main trajectory of the tin metal through the process, and can be found in the tin-containing process streams, including solder streams based on a mixture of Pb and Sn. However, the concentrations of silver in those pyrometallurgical tin-containing streams are still relatively low. However, when the process involves the recovery of a high purity tin metal product, the levels of silver easily become so high that they are undesirable in the high purity tin product.
This has created a need for the recovery of silver from streams containing tin containing relatively low levels of silver, such as lead / tin mixtures often referred to as "solder" streams.
Patents CN205710871 (U) and CN105970003 (A) describe a process for recovering silver from crude solder containing Sn / Pb / Ag (62-78%, 20-38%, 0.2-2.0 wt. -%). The molten solder is contacted with molten zinc to form two metal-metal compounds with high melting points: Ag »Zns (665 ° C) and / or Ag» Zns (636 ° C). Those solid metal-metal compounds can be easily separated as a zinc-silver alloy from the molten solder having a melting temperature of 185-190 ° C in a crystallizer type device, by setting a temperature profile in the range of 410-430 ° C which gradually decreases to 220-200 ° C in the six or eight temperature zones of the appliance. The disadvantage of that method is that the silver is obtained in a chemically bound form as part of the metal-metal compounds, which makes its recovery difficult.
The use of fractional crystallization in the processing of tin-containing molten metal streams is also known.
Patent CN 103667744 describes a 2-step fractional batch crystallization process for upgrading a tin of purity 99.9 +% to a tin of purity 99.99 +%. The first step removes, on the high temperature side, a tin alloy containing up to 99.88% by weight tin enriched in arsenic, copper, iron and antimony from a eutectic alloy contained in the 6 zone crystallizer.
The second step, using a different temperature profile in the same equipment, removes, on the lower temperature side, an eutectic alloy containing up to 99.91 wt.% Tin enriched in lead, indium and bismuth from the target tin of purity. 99.99 +%. Only about half of the amount of 99.9 +% purity tin as a starting material ultimately becomes the high-quality tin product of 99.99 +% purity. The disadvantages of this process are therefore the large amount of low purity tin alloys as by-products, the complexity of the process, and the need to run the process in batch mode.
The by-products are still very dilute with respect to all elements other than tin, and thus do not represent an interesting source for their recovery.
The presence of silver in this process is extremely low, ie at most 5 ppm by weight in the starting materials, and at most 21 ppm by weight in the by-product obtained from step 2. CN 103667744 is clearly not directed to the recovery of the small amounts of silver in the starting materials.
Patent CN 102534249 B discloses a process that removes, by fractional crystallization, a significant amount of the tin present in a raw tin base material having a high content of silver, which further contains about 8% lead and about 1% by weight silver .
The aim of the process is to reduce the volume of the metal mixture before the mixture is fed to the electrolytic precious metals recovery, and the volume is said to be reduced in the range of 10-30% of the starting volume before the crystallization step.
The crystallizer is filled with the crude tin and the temperatures in the 4 zones or stages are maintained within specific ranges, increasing from zone 1 (about 235 ° C) to zone 4 (about 650 ° C). The crude tin is continuously fed to the crystallizer and the solder by-product is continuously withdrawn. The refined tin that is produced collects as crystals in the hot end of the crystallizer and contains at least 99.96 weight percent tin, less than 0.03 weight percent lead, and less than 100 ppm by weight silver. The solder produced by the crystallizer contains 20-30 wt.% Lead and 2.5-4.6 wt.% Silver, the remainder being tin, and is intended to be sent to the downstream electrolysis step for the electrolytic recovery. of precious metals. The method reduces the amount of material to be processed by the downstream electrolysis step to only 10-30% as compared to the same method without the intervening crystallization step. The disadvantage of the method of CN 102534249 B is that it achieves a concentration factor of only at most 4 for the concentration of silver from the feed to the bleed by-product. This can make the method suitable for processing a base material in which the content of silver is already considerable (about 1% by weight). This method leaves something to be desired for more dilute feedstocks. Another drawback is that the amount of bleed current produced is still high, up to about V4 to 1/3 of the amount of feedstock fed to the crystallizer. Thus, there remains a need for a process for the recovery of silver from tin-containing molten metal streams that is capable of starting with a base stock that is quite dilute in silver content, but at the same time capable of recovering the silver. supply in a by-product stream sufficiently rich in silver to be labeled as a base material suitable for recovering the silver from it. It is an object of the present invention to obviate or at least alleviate the above-described problem, and / or to provide improvements in general. SUMMARY OF THE INVENTION
According to the invention there is provided a metal composition and a method as defined in any of the appended claims.
In one embodiment, the present invention provides a metal composition comprising, on a dry weight basis: ° at least 6.0% by weight and at most 30.0% by weight of lead, ° at least 70.0% by weight and at least not more than 91% by weight of tin, ° at least 95.0% by weight and not more than 99.0% by weight of lead and tin together, ° at least 0.75% by weight and not more than 5.00% by weight of silver, and ° at least 0.24% by weight of antimony.
Applicants have found that the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention described below, is a surprisingly suitable base material for the recovery of silver. by means of an electrolysis step in which the cathode collects most of the Sn and Pb, and if desired also some of the Sb, from the anode cast from the metal composition, and the silver is collected as part of the anode glue. A suitable technique for that electro-refining step is to use an electrolyte based on hexafluorosilicic acid (H2SiFe), fluoroboric acid and / or phenyl sulfonic acid; a temperature of about 35-40 ° C; a current density in the range of 100-200 A / m °, and a spacing between electrodes of about 100 mm.
Applicants have found that during the electrolysis of anodes cast from the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid bleed product from the crystallizer of the process of the present invention, the anode slime forming is better. sticks to the anode, and it is possible that much less of the anode adhesive, or even none of it, gets dispersed in the electrolyte. This represents a significant advantage in the recovery of the anode silica from this electrolysis step. After a period of use in the electrolytic cell, the anode can be pulled out of the electrolysis bath and the anode glue can be scraped off the anode. The cleaned anode can then be re-placed in the electrolytic cell for further service, or it can be recycled as a "spent anode" to the upstream anode casting step.
This method of anode slime recovery is much easier than the conventional method in which anode slime disperses in the electrolyte, eventually collects in the bottom of the cell, and must be recovered as part of a filter cake obtained from a sedimentation and / or filtration step that is part of the electrolyte cycle, or in a circulating pump over the electrolytic cell. The conventional method also uses flocculants and other chemicals to promote and enhance the sedimentation and / or filtration steps, which, however, may affect the electrolysis step and / or end up in the anode adhesive product.
Without wishing to be bound by this theory, Applicants believe that the advantage of the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, is the electrolysis formed anode glue sticks to the anode is due to the minimal presence of antimony in the metal composition, as prescribed, possibly enhanced by bismuth, which is suspected of contributing to the same effect. Applicants believe that this effect can be obtained without any problems if the antimony concentration in the metal composition of the present invention is not too high, ie less than 5% by weight, a condition inherently satisfied because of the lower limits for tin plus lead together, and for silver.
Applicants have found that also the relative presence of tin and lead brings an advantage to the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention. In the two-phase diagram of Pb versus Sn, the composition is on the inside of the eutectic composition, where the melting temperatures are lower than on the lead side of the binary diagram. This entails the advantage that the melting temperature and / or the viscosity of the metal composition according to the present invention is lower. This provides advantages in casting the anodes from the metal composition of the present invention, because the lower viscosity brings the advantage of better filling of the mold, and the lower melting temperature brings the advantage of a higher dimensional stability of the mold. the cast anodes, such as less risk of warping or other forms of deformation during the cooling of the anode after casting.
Applicants have further found that the high amount of tin relative to antimony, as inherently dictated by the prescribed conditions for the metal composition of the present invention, is preferably obtained as the first silver-enriched liquid bleed product from the crystallizer of the process of the present invention. the present invention contributes to a stable operation of the electrolysis step as described, because the ion content of the electrolyte remains more constant over time.
In one embodiment, the present invention provides a process for the fractional crystallization of a molten crude tin mixture containing lead and silver into a first silver-enriched liquid tap product at the liquid end of the crystallization step and a first tin-enriched product at the crystal end of the crystallization step, wherein the first silver-enriched liquid tap product comprises, on a dry weight basis: ° at least 6.0% by weight and not more than 30.0% by weight of lead, ° at least 70.0% by weight and at most 91 % by weight of tin, ° at least 95.0% by weight and at most 99.0% by weight of lead and tin together, ° at least 0.75% by weight and not more than 5.00% by weight of silver, and ° at least 0.24% by weight of antimony.
In one embodiment, the method of the present invention produces the metal composition of the present invention, characterized in that the crude tin mixture comprises at least 0.1% by weight and at most 7.0% by weight of lead. In one embodiment, the present invention provides a process for the fractional crystallization of a molten crude tin mixture containing silver into a first silver-enriched liquid draw-off product at the liquid end of the crystallization step and a first tin-enriched product at the crystal end of the crystallization step, characterized in that the crude tin mixture comprises at least 0.1% by weight and at most 7.0% by weight of lead.
Applicants have found that the presence of lead in the range as indicated brings significant benefits to the process of the present invention and to at least some of the products it produces.
One advantage is that a minimal presence of lead, as indicated, in the feed to the fractional crystallization is a process stimulus for the fractional crystallization step and ultimately enables this step.
A mixture of 38.1 wt.% Pb and 61.9 wt.% Sn has a melting temperature of only 183 ° C, ie lower than the melting temperatures of pure lead (327.5 ° C) and of pure tin (232 ° C ). The 38.1 / 61.9 percent mixture is referred to as a eutectic composition. When a molten binary mixture of tin and lead with a composition different from the eutectic composition is cooled, crystals are formed which have a composition even more different from the eutectic composition, leaving a liquid phase with a composition closer to the eutectic composition. eutectic composition. The applicants have found that this phenomenon makes it possible to separate a mixture of lead and tin, by fractional crystallization, into, on the crystal side, a product enriched in Sn or Pb, and on the liquid side, a product with a composition closer to the eutectic composition. The minimal presence of lead in the starting material thus makes it possible by fractional crystallization to separate a tin product of higher purity at the crystal end from a liquid product containing more lead than the starting material.
Applicants have further found that, with a lead / tin mixture containing more tin than the eutectic composition of tin with lead, and if that mixture further contains relatively small amounts of silver, the silver tends to converge in a fractional crystallization of the mixture. with most of the lead in the liquid phase, and that tin crystals can be obtained with a much lower content of silver and lead.
Applicants have found that the lead acts as a carrier for the silver.
Applicants have further found that, in such a fractional crystallization process, the concentration of the silver can be increased from a lower content in the feed mixture to a higher content in the liquid crystallizer product.
Applicants have further found that when the amount of lead in the feed to the fractional crystallization step is maintained below the upper limit as indicated, the increase in the concentration of silver from feed stream to liquid crystallizer product can be significantly improved.
Applicants have found that this allows the processing of feedstocks containing relatively low concentrations of silver, and yet, at the same time, obtaining a limited volume product stream significantly enriched in silver such that that stream becomes suitable for further processing with for the purpose of recovering the silver.
Applicants have further found that when the lead content of the first silver enriched liquid interception product is kept in line with the upper limit as indicated, and the tin content in the same product stream is kept in line with the lower limit as indicated in the part of the fractional crystallization process, fewer steps are required to achieve the desired separation and enrichment of silver from feed stream to bleed product.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a flow chart of a larger general method comprising a preferred embodiment of the method of the present invention.
DETAILED DESCRIPTION The present invention will be described below in specific embodiments and with possible reference to specific drawings; however, it is not limited thereto, but is determined solely by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some elements may be enlarged for illustrative purposes and not drawn to scale. The dimensions and relative dimensions do not necessarily correspond to actual practical embodiments of the invention.
Furthermore, the terms first, second, third, and the like, are used in the specification and claims to distinguish between similar elements, and not necessarily to describe a sequential or chronological order. The terms are interchangeable in appropriate circumstances, and the embodiments of the invention may function in sequences other than those described or illustrated herein.
Furthermore, the terms top, bottom, top, bottom, and the like are used in the description and claims for descriptive purposes, and not necessarily to describe relative positions. The terms so used are interchangeable in appropriate circumstances, and the embodiments of the invention described herein may function in orientations other than those described or illustrated herein.
The term "comprising", as used in the claims, is not to be construed as being limited to the means enumerated in its context. He does not exclude other elements or steps. The term should be interpreted as the required presence of the stated properties, numbers, steps or components, but does not exclude the presence or addition of one or more other properties, numbers, steps or components, or groups thereof.
Thus, the scope of the expression “an item comprising means A and B” need not be limited to an item composed only of components A and B.
It means that in the context of the present invention, A and B are the only relevant components.
Accordingly, the terms "comprise" or "include" also include the more restrictive terms "consist essentially of" and "consist of". Accordingly, when “comprise” or “contents” is replaced by “consist of”, these terms represent the basis of preferred, but constrained embodiments, which are also provided as part of the contents of this document relating to the present invention.
Unless otherwise specified, all value ranges listed in this document include the range up to and including the indicated endpoints, and the values of the ingredients or components of the compositions are expressed in weight percent, or weight%, of each ingredient in the composition.
Terms such as "weight percent", "weight%", "weight%" "percent by weight," "% by weight", "ppm by weight", "ppm by weight", "ppm by weight", "weight. ppm ”or“ ppm ”and variations thereof, as used in this document, refer to the concentration of a substance as the weight of that substance divided by the total weight of the composition and multiplied by 100 or 1000000 as appropriate unless otherwise stated.
It should be understood that the terms "percent", "%," used herein are intended to be synonyms of "percent by weight," "percent by weight" etc.
It should further be noted that, in the present description and the appended claims, the singular forms “a”, “the” and “it” may also refer to plural matters, unless the contents clearly indicate otherwise.
For example, reference to a composition comprising "a compound" includes a composition having two or more compounds.
It should also be noted that the term "or" is generally used in the sense that includes "and / or" unless the content clearly indicates otherwise.
Furthermore, each compound used here can be interchangeably discussed by its chemical formula, chemical name, abbreviation, etc.
Most of the metal streams in the process of the present invention contain a high proportion of lead, often in combination with a significant amount of tin. Such currents have a relatively low melting point and have been used for centuries to attach one solid to another solid, through a process often referred to as “soldering”. Such currents are therefore often referred to as so-called "solder" currents or "solder", and that term is also used in this document to designate such currents.
Among the target metals recovered by the present invention, Sn and Pb are considered to be "the brazing metals". These metals are distinguished from other metals, especially copper and nickel, in that mixtures containing large amounts of these metals generally have a much lower melting point than mixtures containing large amounts of copper and / or nickel. Such compounds were used millennia ago to form a permanent bond between two pieces of metal by first melting the “solder”, then applying and solidifying. To this end, the solder had to have a lower melting temperature than the metal of the pieces that were connected by it. In the context of the present invention, by a solder product or a solder metal composition, two terms used interchangeably herein, are meant metal compositions in which the combination of the solder metals, i.e. the content of Pb plus Sn, makes up the majority of the composition, ie at least 50% by weight and preferably at least 65% by weight. The solder product may further contain minor amounts of the other target metals copper and / or nickel, and non-target metals such as Sb, As, Bi, Zn, Al and / or Fe, and / or elements such as Si.
Unless otherwise noted, amounts of metals and oxides in this document are expressed in accordance with current pyrometallurgic practice.
The presence of each metal is generally expressed as its total presence, regardless of whether the metal is present in its elemental form (oxidation state = 0) or in a chemically bound form, usually in an oxidized form (oxidation state> 0). For the metals which can be relatively easily reduced to their elemental form, and which can exist as molten metal in the pyrometallurgical process, it is quite common to express their presence in terms of their elemental metal form, even when the composition of a slag or scratch is indicated, where the majority of such metals may in fact be present in an oxidized and / or chemically bound form.
Therefore, in the composition of the metal mixture as feed to step (a), the content of Fe, Zn, Pb, Cu, Sb, Bi is expressed as elemental metals.
Less noble metals are more difficult to reduce under nonferrous pyrometallurgical conditions and are mostly in an oxidized form.
These metals are usually expressed in terms of their most common oxide form.
Therefore, in slag or scratch compositions, the content of Si, Ca, Al, Na is usually expressed as SiO2, CaO, Al2O3, Na2O, respectively.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises at least 6.5% by weight of lead, preferably at least 7 , 0 wt%, more preferably at least 8.0 wt%, even more preferably at least 9.0 wt%, preferably at least 10.0 wt%, more preferably at least 11.0 wt%, even more preferably at least 12.0 wt%, preferably at least 13.0 wt%, more preferably at least 14.0 wt%, even more preferably at least 15.0 wt -% lead.
Lead is a stimulating element in the upstream process by which the metal composition of the present invention is produced, because the ability to recover silver from a raw tin stream by fractional crystallization is based on the existence of lower melting eutectic composition in the binary phase system lead -tin.
Applicants prefer to keep the content of lead in the metal composition of the present invention above the lower limit as indicated, because a higher content of lead in the tapping product of the fractional crystallization step in which the metal composition of the present invention is produced, relative to the lead content in the feed to the fractional crystallization step, a higher concentration factor of the silver entails from feed stream to bleed product in the crystallization step. A higher concentration factor has the advantage of being able to process feedstocks that are more dilute in silver for the same quality of tapping product, and / or produce a tapping product that is more concentrated in silver for a feedstock of the same content of silver.
More lead in the metal composition of the present invention also makes the composition more suitable for the recovery of the lead, tin and antimony in the stream by electrolysis in combination with pyrometallurgy. More lead also means more lead in the cathodes produced in the electrolysis step discussed above. When those cathodes are subjected to a vacuum distillation step to separate the lead and antimony from the tin, and to produce a high purity tin precursor from which a high purity high purity tin product can be readily derived by chemical refining, the lead functions as a carrier for the antimony. The lead promotes the removal of antimony from the tin, and thus a higher level of lead is desired in the metal composition of the present invention.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises at most 27.5% by weight, preferably at most 25, 0 wt%, more preferably at most 22.50 wt%, preferably at most 20.0 wt%, more preferably at most 17.5 wt%, even more preferably at most 15.0 wt. % lead.
The lead content, in combination with the tin content, is preferably such that the metal composition, which is preferably obtained as the first silver-enriched liquid tapping product from the crystallizer of the process of the present invention, falls on the correct side of the eutectic composition in the binary Pb / Sn phase diagram, such that the tin is carried to a higher concentration in the crystal product exiting the crystallization step at the hot end, and the majority of the lead ends up in the bleed product that the crystallization step at the cold end end, and whose composition is closer to the eutectic composition as compared to the feed composition.
Applicants have found that adhering to the upper limit on lead as indicated also reduces the risk of crystals growing on the vanes of the screw in the crystallizer, because the composition of the current stays further away from the eutectic composition.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises at least 72.5% by weight, preferably at least 75, 0 wt%, more preferably at least 77.5 wt%, even more preferably at least 80.0 wt%, preferably at least 81.0 wt%, more preferably at least 82.0 wt %, even more preferably at least 83.0% by weight, preferably at least 84.0% by weight, more preferably at least 85.0% by weight, even more preferably at least 87.5% by weight % tin.
Tin is also a stimulating element in the upstream process to produce the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, because of its ability to recover silver. recovery from a crude tin stream by fractional crystallization is based on the existence of lower melting eutectic composition in the lead-tin binary phase system. The tin content, in combination with the lead content, is preferably such that the metal composition, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the method of the present invention, falls on the correct side of the eutectic composition in the binary Pb / Sn phase diagram, such that the tin is carried to a higher concentration in the crystal product exiting the crystallization step at the hot end, and the majority of the lead ends up in the bleed product that the crystallization step at the cold end end, and whose composition is closer to the eutectic composition as compared to the feed composition. Applicants have found that this arrangement ensures that silver from the feed to the crystallizer is carried to a higher concentration in the tapping product, and that consequently silver is recovered by separating silver from the tn-enriched product being produced. by the crystallizer.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises up to 90% by weight of tin, preferably up to 89.0 wt%, more preferably at most 88.0 wt%, even more preferably at most 87.0 wt%, preferably at most 86.0 wt%, more preferably at most 85.0 wt. %, even more preferably at most 84.5 wt%, preferably at most 84.0 wt%, more preferably at most 83.0 wt%, even more preferably at most 82.0 wt% tin. Applicants have found that respecting the upper limit of tin has the advantage of leaving more room for lead in the composition. Since more lead brings the advantage that a higher concentration factor for silver can be achieved in the upstream crystallizer step, the lower content of tn entails the advantage of a potentially higher content of silver in the metal composition of the present invention, which is preference is obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, combined with a lower content of silver in the tin-enriched product obtained at the crystal end of the upstream crystallization step, which together means that more of the silver present ends up in the intended product, from which it can be upgraded to a commercial grade silver product. This brings the advantage that for the same amount of metal composition more high quality silver can be recovered, or that for the same amount of silver that can be recovered from the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid tapping product. from the crystallizer of the method of the present invention, a smaller volume of the metal composition should be processed, and less Sn / Pb by-product should be processed after the downstream separation of most of the tin and lead from the silver.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises at least 95.25% by weight of lead and tin together, preferably at least 95.5 wt%, more preferably at least 95.75 wt%, even more preferably at least 96.00 wt%, preferably at least 96.25 wt%, preferably at least 96 , 5% by weight, more preferably at least 96.75% by weight, even more preferably at least 97.00% by weight of tin and lead together. A higher content of Sn + Pb entails the advantage that the metal composition according to the present invention can contain fewer undesirable elements. Applicants have found that in addition to the lead and tin, and the silver as target metal for recovery, an amount of antimony and a limited amount of arsenic may also be acceptable, but that a number of other elements are preferably kept at the level of trace amounts. Such an element is, for example, iron (Fe), because that element can be detrimental to the operation of the electrolysis step in which an anode glue rich in silver can be recovered while most of the tin and lead can be caused to deposit in a cathode byproduct. The mechanism by which iron can influence electrolysis is described in detail in WO 2019/219821 A1. Other elements, such as nickel, can also be an additional load in electrolysis, and higher levels of copper can also require additional measures in the downstream processing of the metal composition of the present invention and / or derivatives thereof. For example, applicants prefer that the copper content be limited in the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, as it is believed that copper counteracts the beneficial effect resulting from the presence of antimony and / or bismuth. The higher lead and tin content thus contributes to all these benefits.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises not more than 98.75% by weight of lead and tin together, preferably at most 98.50 wt%, more preferably at most 98.25 wt%, even more preferably at most 98.00 wt%, preferably at most 97.75 wt%, more preferably at most 97.50 wt%, even more preferably at most 97.25 wt%, preferably at most 97.00 wt%, more preferably at most 96.75 wt%, even more preferably at most 96 , 50% by weight of lead and tin together. Maintaining the content of lead and tin together below the upper limit as indicated has the advantage that there is more room in the composition for the presence of the target metal silver, ie for its economic value, and for the elements antimony and bismuth, which are desirable for their positive effects, as described above. Preferably, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, does not contain metals other than lead, tin, silver, bismuth and antimony in concentrations greater than trace levels. For copper 0.5% by weight still counts as trace metal, and it is usually an unintended consequence of the metal composition of the present invention being a by-product of copper refining. For the other metals, the trace content is preferably at most 0.2% by weight for each. More preferably, the contents of elements other than lead, tin, silver, bismuth, antimony, copper, arsenic and indium are at most 0.05% by weight for each.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises at least 0.90 weight% silver, preferably at least 1 0.00% by weight, more preferably at least 1.25% by weight, even more preferably at least 1.50% by weight, preferably at least 1.60% by weight, preferably at least 1.70 % by weight, more preferably at least 1.75% by weight, even more preferably at least 2.00% by weight silver. Silver is the target metal in the first silver-enriched liquid draw-off product from the crystallizer, which may also be the metal composition of the present invention. It is the element with the higher market value compared to the other metals discussed in this context in this document. A higher content of silver brings the advantage of a higher economic interest in the metal composition.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises up to 4.50 wt% silver, preferably up to 4 0.00 wt%, more preferably at most 3.50 wt%, even more preferably at most 3.00 wt%, preferably at most 2.75 wt%, more preferably at most 2.50 wt %, even more preferably at most 2.25 wt%, preferably at most 2.00 wt%, more preferably at most 1.75 wt%, even more preferably at most 1.50 wt% silver.
Applicants prefer to respect this upper limit for silver, as this leaves room for respecting the lower limit for lead and tin together described above, thus enabling the ability to achieve the associated effects.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the method of the present invention, comprises at least 0.25% by weight of antimony, preferably at least 0 , 30 wt%, more preferably at least 0.35 wt%, even more preferably at least 0.40 wt%, preferably at least 0.45 wt% of, preferably at least 0.50 % by weight, more preferably at least 0.55% by weight, even more preferably at least 0.60% by weight of antimony.
The advantages provided by antimony in the metal composition of the present invention have been discussed above in this document.
A higher antimony content enhances those effects.
An additional advantage is that the cathodes obtained in the downstream electrolysis step performed on the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the method of the present invention, are without problems. can be introduced into a process for the recovery of high purity high quality tin product together with a high quality hard lead product, because the high quality hard lead product allows for a significant content of antimony, and because the antimony is greatly contributing to the desired properties of the high quality hard lead product, in compared to higher purity high quality soft lead products.
Applicants have found that, in order to further increase the content of antimony in the anodes to be cast from the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention. present invention, this can be obtained without difficulty by introducing a small amount of Pb / Sb concentrate, such as, for example, a small amount of the high quality hard lead product obtained downstream of the process of the present invention. Applicants have found that the most preferred antimony (along with bismuth) content for excellent electrolysis performance can be easily obtained in the anodes cast into the metal composition of the present invention. Applicants prefer that the content of antimony plus bismuth in those anodes is at least 1.0% by weight, and optionally at most 1.5% by weight.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises up to 4.00% by weight or even up to 3.50% by weight. wt% antimony, preferably at most 3.00 wt%, more preferably at most 2.50 wt%, even more preferably at most 2.00 wt%, preferably at most 1.75 wt. %, more preferably at most 1.50 wt%, even more preferably at most 1.25 wt%, preferably at most 1.00 wt%, more preferably at most 0.75 wt% antimony. This brings the advantage in the downstream electrolysis step that antimony does not dissolve in the electrolyte but remains in the anode adhesive and contributes to stronger adhesion of the anode adhesive to the anodes, such that the anode adhesive is recoverable by simply removing the used anode. scrape. Another advantage of a smaller amount of antimony is that the anode glue is more concentrated in terms of the target metal silver, and thus more suitable for upgrading the silver to a high quality commercial grade silver product. In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, is a molten liquid.
This brings the advantage that the composition does not have to be remelted before it can be cast into anodes for the electrolysis step described above in this document, in which Sn / Pb cathodes can be formed and the silver recovered. in a higher concentration as part of anode adhesives that are formed in the electrolytic cell.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises at least 0.05 weight percent and at most 0.5 weight percent % arsenic, preferably at least 0.06% by weight, more preferably at least 0.07% by weight, even more preferably at least 0.08% by weight, preferably at least 0.09% by weight of, preferably at least 0.10% by weight, more preferably at least 0.11% by weight, even more preferably at least 0.12% by weight arsenic, and optionally at most 0.45% by weight arsenic , preferably at most 0.40 wt%, more preferably at most 0.35 wt%, even more preferably at most 0.30 wt%, preferably at most 0.25 wt%, with more preferably at most 0.200% by weight, even more preferably at most 0.175% by weight, preferably at most 0 , 150% by weight, more preferably at most 0.125% by weight, arsenic.
Applicants have found that limited levels of arsenic are acceptable in further processing of the metal composition of the present invention.
Allowing arsenic in the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, relaxes and broadens the acceptability criteria for the upstream processes from which the metal composition is obtained .
In the downstream electrolysis of anodes cast with the metal composition of the present invention, optionally with an amount of added Pb / Sb concentrate as outlined above, most of the arsenic will tend to remain with the anode adhesive and from the process. be removed as part of it.
Applicants prefer that the arsenic remains below the specified upper limit because it causes less dilution of the silver in the anode adhesive and makes the anode adhesive more suitable for upgrading the silver contained therein to a high quality, commercial grade silver product.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the method of the present invention, further comprises at least 0.05% by weight and at most 0.6 wt% of copper, preferably at least 0.07 wt%, more preferably at least 0.10 wt%, even more preferably at least 0.12 wt%, preferably at least 0.15 wt % of copper, preferably at least 0.20% by weight, more preferably at least 0.25% by weight, even more preferably at least 0.30% by weight of copper, and optionally at most 0.55 weight% of copper, preferably at most 0.50 weight%, more preferably at most 0.48 weight%, even more preferably at most 0.45 weight%, preferably at most 0.40 weight %, more preferably at most 0.350% by weight, even more preferably at most 0.325% by weight at preferably at most 0.300% by weight, more preferably at most 0.250% by weight of copper.
Allowing copper in the metal composition of the present invention, which is preferably obtained as the first silver enriched liquid draw-off product from the crystallizer of the process of the present invention, entails the advantage that the upstream process producing the composition , can pick up feed streams containing copper, such as by-products from copper refining.
The upstream process producing the metal composition of the present invention is preferably part of a general process involving the production of refined copper, refined tin and refined lead, and the metal composition of the present invention is preferably a by-product of such process for the recovery of silver, which is fed into the global process. Applicants, however, prefer to limit the presence of copper in the metal composition of the present invention because the copper increases the load in the downstream process steps. Thus, it is believed that too high a presence of copper negates the above described advantages of the presence of antimony (and bismuth) in the metal composition of the present invention. If the copper content upstream of the metal composition of the present invention is above the prescribed upper limit, some of the copper can be removed by the addition of sulfur, creating a scratch containing copper sulfides that can be easily scraped off and recycled into an upstream pyrometallurgical process step, and which can leave a composition which meets all the prescribed conditions for the metal composition of the present invention.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the method of the present invention, comprises at least 0.0030 weight percent and at most 0.0500 weight percent % nickel, preferably at least 0.0050% by weight, more preferably at least 0.0075% by weight, even more preferably at least 0.0100% by weight, preferably at least 0.0125% by weight of, preferably at least 0.0150 wt.%, more preferably at least 0.0175 wt.%, even more preferably at least 0.0200 wt.% nickel, and optionally at most 0.0450 wt.% nickel , preferably at most 0.0400 wt%, more preferably at most 0.0350 wt%, even more preferably at most 0.0325 wt%, preferably at most 0.0300 wt%, with more preferably at most 0.0275 wt%, even more preferably at most 0.0250 wt ts%, preferably at most 0.0225 wt.%, more preferably at most 0.0200 wt.% nickel. Applicants prefer to allow a limited amount of nickel in the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, because it requires the process which the composition produces allows to include feeds containing nickel, such as by-products from copper refining and / or nickel refining.
The presence of nickel is preferably limited so as not to create too great a load in the downstream processing of the metal composition, such as the electrolysis step, where the nickel will tend to dissolve in the electrolyte but not be deposited on the electrolyte. cathode.
This can lead to an accumulation of nickel in the electrolyte, which may need to be contained by providing an electrolyte draw-off stream from the electrolysis step, as described in WO 2019/219821 A1. In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises at least 0.0010 wt.% And at most 0.40 wt. % of bismuth, preferably at least 0.0020% by weight, more preferably at least 0.0030% by weight, even more preferably at least 0.0040% by weight, preferably at least 0.0060% by weight %, preferably at least 0.0070% by weight, more preferably at least 0.0085% by weight, even more preferably at least 0.0100% by weight of bismuth, and optionally at most 0.30% by weight % of bismuth, preferably at most 0.200% by weight, more preferably at most 0.150% by weight, even more preferably at most 0.1000% by weight, preferably at most 0.0750% by weight, more preferably at most 0.0500 weight%, even more preferably at most 0.0400 % by weight, preferably at most 0.0300% by weight, more preferably at most 0.0250% by weight of bismuth.
Applicants have found that limited amounts of bismuth are acceptable, that is, the upstream process can include feeds containing bismuth.
Applicants have further found that bismuth is also desirable in the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, as it is believed to contribute to the advantageous effect of antimony when the metal composition of the present invention is used as feed for the electrolysis step as described above. Applicants prefer to respect the indicated upper limit because the bismuth remains in the anode glue, and thus less bismuth brings the advantage of anode glue which is more concentrated in the target metal silver, making this anode glue more suitable for upgrading the silver contained therein to a high quality commercial grade silver product.
Applicants have also found that bismuth can get into the high performance tin product derived from the metal composition, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, in which limited levels are acceptable. In addition, the small amount of bismuth present in the final tin product has the advantage of lowering the temperature at which a phenomenon called "tin plague" may occur.
Tin pest is an autocatalytic conversion at sufficiently low temperatures from the white beta form of continuous solid tin to the gray alpha tin powder, which can give the white tin surface a dull gray appearance and possibly, due to the autocatalytic nature of the conversion, even lead to physical disintegration of the tin metal article into a gray powder.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises at most 1.0 wt% iron, preferably at most 0 1 wt%, more preferably at most 0.01 wt%, even more preferably at most 0.0050 wt%, even more preferably at most 0.0010 wt% iron.
Applicants have found that limiting the iron content as indicated provides a significant benefit when the metal composition of the present invention, which is preferably obtained as the first silver enriched liquid draw-off product from the crystallizer of the process of the present invention, is used for casting anodes as a feedstock for the electrolysis step discussed above. Applicants have found that iron dissolved in the electrolyte of such a step results in significant energy inefficiencies by preventing some of the electrical current through the cell from contributing to the transfer of cations from lead and tin from anode to cathode. Without wishing to be bound by this theory, Applicants believe that iron cations in the electrolyte are readily able to change valence, possibly through the half reaction Fe '-> Fe * + e taking place at the anode, and after the Fe ** - cation has passed to the cathode, the reverse half reaction Fe + e -> Fe ”at the cathode, after which the Fe * cation is able to return to the anode. This mechanism could explain the observation that, with significant amounts of iron in the electrolyte, some of the electrical current can pass through the cell without contributing to lead and / or tin cation transfer.
Applicants have also found that an additional, but non-contributing electric current is required to maintain the same cathode productivity due to the iron in the anodes, and thus also in the electrolyte. The increased current increases the voltage across the cell, as well as increases more quickly, leading to increased levels of contaminants in the cathode and causing the maximum allowable level to be reached more quickly. The higher current also generates more heat in the cell, and possibly hot spots, causing other problems. It also drives the current density higher for the same productivity, increasing its contribution to cathode contamination. More details on the problems caused by the presence of iron are described in WO 2019/219821 A1.
When iron from the anode dissolves into the electrolyte, it increases the density and viscosity of the electrolyte, which affects the mechanisms of mass and heat transfer in the electrolytic cell, for example the movement of the target cations on the way to the cathode . A high level of Fe in the anode, and thus also in the electrolyte, increases the resistance that must be overcome by those target cations on the way to the cathode.
Therefore, the metal composition of the present invention should contain iron at a level below the prescribed upper limit.
In one embodiment, the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention, comprises at least 0.0005% by weight of gold, preferably at least 0.0010 wt%, more preferably at least 0.0020 wt%, even more preferably at least 0.0030 wt%, preferably at least 0.0040 wt% of gold, more preferably at least 0.0050 wt%, even more preferably at least 0.0060 wt%, even more preferably at least 0.0070 wt%, preferably at least 0.0080 wt% of, more preferably at least at least 0.0085 wt%, even more preferably at least 0.0090 wt%, even more preferably at least 0.0100 wt% of gold, and optionally at most 0.0500 wt%, preferably at most 0.0250% by weight, more preferably at most 0.0200% by weight, with even more preferably at most 0.0175% by weight of gold. Applicants have found that gold present in small amounts in the pyrometallurgical processing of nonferrous metals can concentrate in the bleed stream of a fractional crystallization step as described as part of the process of the present invention, and therefore may be present in the metal composition of the present invention, which is preferably obtained as the first silver-enriched liquid draw-off product from the crystallizer of the process of the present invention. Gold is a precious metal and can be recovered along with silver and other precious metals optionally present in the composition, particularly as part of the anode glue formed in the electrolysis step in which the composition can be processed as feedstock.
In one embodiment of the method of the present invention, the amount of lead in the crude tin mixture as feed to the crystallization step is at least 0.15% by weight, preferably at least 0.20% by weight, more preferably at least 0. 30 wt%, even more preferably at least 0.40 wt%, even more preferably at least 0.50 wt%, preferably at least 0.60 wt%, more preferably at least 0, 70% by weight, even more preferably at least 0.80% by weight, preferably at least 0.90% by weight, and more preferably at least 1.00% by weight. The lead stimulates the fractional crystallization step, and acts as a solvent for the silver that the step aims to remove from the main raw tin stream. The silver tends to lag most of the lead and enter the bleed stream, and the composition of the bleed stream approaches the eutectic composition of 38.1 wt% / 61.9 wt% Pb / Sn. Respecting this lower limit for the presence of Pb promotes the feasibility of the fractional crystallization step, for example by ensuring that there is sufficient liquid phase present in the crystallizer steps where good and intimate contact between liquid and crystals is desired to obtain a efficient and / or effective separation.
In one embodiment of the method of the present invention, the amount of tin in the raw tin mixture as feed to the crystallization step is at least 65% by weight, preferably at least 70% by weight, more preferably at least 80% by weight, with even more preferably at least 90% by weight, preferably at least 92% by weight, and more preferably at least 92.0% by weight. Respecting this lower limit ensures that the crystallizer functions on the correct side of the eutectic composition between lead and tin. This ensures that a draw-off stream is obtained with a composition that approximates the eutectic composition and that most of the lead, and therefore also of the silver, is found in the draw-off product from the crystallization step and not at the crystal end.
In one embodiment of the method of the present invention, the crude tin mixture comprises at most 6.5% by weight of Pb, preferably at most 6.0% by weight, more preferably at most 5.5% by weight. even more preferably at most 5.25% by weight, preferably at most 5.00% by weight, more preferably at most 4.90% by weight. even more preferably at most 4.80% by weight, preferably at most 4.00% by weight, more preferably at most 3.00% by weight. even more preferably at most 2.00 weight% Pb, preferably at most 1.50 weight% Pb. With lower amounts of lead in the crude tin mixture as feed to the crystallizer step, Applicants have found that the volume of tapped by-product can be kept lower and the concentration of silver in the tapping stream can be kept higher. This has the advantage that silver can be recovered from more dilute feedstocks, while at the same time producing a bleed stream sufficiently rich in silver to permit effective and efficient recovery of the silver therefrom. The lower volume and higher silver content of the bleed stream are also beneficial to the efficiency and effectiveness of the process steps for recovering the silver from the bleed stream.
In one embodiment of the method of the present invention, the concentration of lead in the crude tin mixture is at least 3.0 times the concentration of silver in the crude tin mixture, preferably at least 4.0, more preferably at least 5.0 , even more preferably at least 6.0, and even more preferably at least 7.0 times the concentration of silver in the crude tin mixture. Applicants have found that respecting this lower limit for the ratio of lead to silver concentration prevents the tap composition from approaching a eutectic composition in the lead / tin / silver ternary diagram.
In one embodiment of the method of the present invention, the crude tin mixture comprises at least 10 ppm by weight of silver (Ag), preferably at least 20 ppm by weight, more preferably at least 25 ppm by weight, even more preferably at least 30 ppm by weight, even more preferably at least 50 ppm by weight, preferably at least 100 ppm by weight, more preferably at least 200 ppm by weight, even more preferably at least 300 ppm by weight, even more preferably more preferably at least 500 ppm by weight, preferably at least 750 ppm by weight, more preferably at least 1000 ppm by weight, even more preferably at least 1100 ppm by weight, even more preferably at least 1200 ppm by weight of silver, and optionally at most 0.85% by weight of silver, preferably at most 0.80% by weight, more preferably at most 0.75% by weight, even more preferably at most 0.70% by weight , even more preferably at most 0 , 65 wt%, preferably at most 0.60 wt%, more preferably at most 0.55 wt%, even more preferably at most 0.50 wt%, even more preferably at most 0 , 45 wt%, preferably at most 0.40 wt%, more preferably at most 0.35 wt%, even more preferably at most 0.30 wt%, even more preferably at most 0 , 25% by weight, preferably at most 0.20% by weight, more preferably at most 0.175% by weight or at most 1750 ppm by weight, even more preferably at most 1600 ppm by weight, even more preferably not more than 1500 ppm by weight. A higher content of silver in the crude tin mixture as feed to the crystallization step has the advantage that more silver is available to be recovered, and that the crystallizer drain stream can contain more silver, and thus not only a higher economic value but also that the recovery of silver from it can be made more efficient and effective.
Respecting the upper limit for the content of silver entails the advantage that the tapping composition has a lower risk of approximating the eutectic composition in the ternary diagram for Pb / Sn / Ag.
The upper limit on the silver in the crude tin mixture also entails the advantage that it allows a significant increase in concentration from feed stream to crystallizer bleed stream, such that the process is capable of incorporating feed materials with a lower content of silver, i.e. which can be very dilute in terms of Ag.
In one embodiment of the method of the present invention, the crude tin mixture comprises at least 0.1% by weight of antimony (Sb), preferably at least 0.2% by weight, more preferably at least 0.5% by weight, even more preferably at least 1.0% by weight, preferably at least 1.2% by weight, more preferably at least 1.5% by weight, even more preferably at least 2.0% by weight of antimony, and optionally at most 6.0% by weight of antimony, preferably at most 5.0% by weight, more preferably at most 4.0% by weight of antimony.
This brings the advantage that the process of the present invention, as well as the upstream processes producing the crude tin mixture as feedstock for the crystallization step, have a wider flexibility for incorporating raw materials.
Applicants have further found that most of the antimony tends to lag behind the tin in the crystallization step, and the presence of antimony has the advantage of increasing the melting point of the crystals formed thereby increasing the separations. in the crystallizer and provides a clearer separation between the Pb / Ag in the bleed stream and the Sn / Sb in the crystals.
In one embodiment of the method of the present invention, the first tin-enriched product comprises at least 0.05% by weight of lead, preferably at least 0.10% by weight, more preferably at least 0.15% by weight, even more preferably, at least 0.20 weight% lead.
This has the advantage that this stream is more suitable as a feedstock for a distillation step in which lead and antimony can be removed from the main stream by evaporation, and in which the more volatile lead promotes the evaporation of antimony by diluting the vapor phase in the distillation step. .
The lead thus acts as a kind of carrier for the antimony.
Applicants have found, as will be shown elsewhere in this document, that the lead, in combination with the antimony and after the downstream distillation step, provides a top product suitable for deriving a high quality hard lead product.
In one embodiment of the method of the present invention, the first tin-enriched product is produced in a continuous mode. This brings the advantage that the quality of the first tin-enriched product is more constant and stable over time, and that the downstream steps in which that product is further processed can be carried out more effectively and efficiently.
In one embodiment of the method of the present invention, the entire fractional crystallization step is performed in continuous mode. This entails the advantage that the quality of the products from the fractional crystallization step is more constant and more stable over time, such that the further processing of those products can be carried out more efficiently and efficiently.
In one embodiment of the process of the present invention, the first silver-enriched liquid draw-off product is partially and / or temporarily recycled to the feed of the fractional crystallization step. This has the advantage that the silver enrichment factor, i.e. the concentration ratio of the silver concentration in the net bleed product removed from the process to the concentration of silver in the fresh feed to the process, is further increased. This entails the advantages already outlined in that (i) base stocks that are more dilute in silver are made acceptable for the process of the present invention, and (ii) further processing of the bleed stream is made more efficient and effective.
In one embodiment of the method of the present invention, the fractional crystallization step comprises at least 4 crystallizer steps, preferably at least 8, more preferably at least 10, even more preferably at least 12, even more preferably at least 16, at preferably at least 20, more preferably at least 24 crystallizer stages. This has the advantage that the crystallizer is able to establish a clearer separation between the Pb / Ag in the bleed stream and the Sn / Sb in the crystals. This brings the added benefit of higher silver enrichment between feed and tapping composition, with the associated advantages discussed elsewhere in this document.
In one embodiment of the method of the present invention, the crystallizer used in the fractional crystallization step includes a feed stage for receiving the feed to the crystallizer, and the crystallizer further includes at least one crystallizer stage, and preferably at least 2 stages, between the feed stage and each of the crystallizer product outlets.
This brings the advantage that the compositions of both products differ more from the feed composition.
It brings the added benefit of higher operating flexibility.
An additional advantage is that it facilitates the control of the temperature profile in the course of the crystallization step, which leads to an even clearer separation.
In one embodiment of the method of the present invention, the temperature profile across the steps of the fractional crystallization step is in the range of 180-270 ° C.
Applicants have found that this temperature range is sufficient to achieve the desired separation between the Pb / Ag in the bleed stream and the Sn and optionally Sb in the crystal end product of the crystallization step.
Preferably the minimum temperature in the crystallizer is at least 183 ° C, more preferably at least 185 ° C, even more preferably at least 187 ° C, even more preferably at least 190 ° C, preferably at least 193 ° C C, more preferably at least 196 ° C.
Optionally, the maximum temperature in the crystallizer is at most 265 ° C, preferably at most 260 ° C, and more preferably at most 255 ° C.
These temperature guidelines bring the advantage of smaller temperature differences throughout the crystallizer, such that less heating and / or cooling has to be provided.
In one embodiment of the method according to the present invention, the temperature difference between two adjacent steps in the fractional crystallization step, none of which is a feed step or a final step, is at most 20 ° C, preferably at most 15 ° C, with more preferably at most 10 ° C.
This entails the advantage that less cooling and / or heating has to be provided, such that less heat exchange surface has to be provided, while at the same time the quality of the separation is improved.
In one embodiment of the process of the present invention, the fractional crystallization step is performed in at least 2 crystallizers in series, with the product being fed from the crystal end of the upstream crystallizer to the downstream crystallizer, or completely to the feed stage of the downstream crystallizer, or only a first portion thereof is supplied to the feed stage of the downstream crystallizer and a second portion thereof is fed to a second stage of the downstream crystallizer which is a different stage from the feed stage, said second stage being selected from the stages occurring are located between the feed stage and the final stage at the crystal end of the downstream crystallizer, the second stage being preferably separated from the feed stage by at least one and preferably two or three intermediate stages. Applicants have found this arrangement to be very convenient and able to achieve better separation. In addition, this arrangement provides additional flexibility in choosing where intermediate and / or recirculation flows are directed.
In one embodiment of the process of the present invention, the product from the liquid end of the downstream crystallizer is at least partially, and preferably completely, at least temporarily recycled to the upstream crystallizer, optionally to the feed stage but preferably to a second stage which is selected from the stages located between the feed stage and the final stage at the crystal end of the upstream crystallizer, the second stage preferably being separated from the final stage by at least one and preferably two or three intermediate stages. This has the advantage that less lead can accumulate in the downstream crystallizer by possibly entraining lead returned to the upstream crystallizer with the recirculation of bleed product from the downstream crystallizer and wetting the crystal product from the upstream crystallizer. is fed to the downstream crystallizer. In one embodiment of the method of the present invention, the crude tin mixture further comprises at least 1 ppm by weight of at least one metal selected from copper, iron, bismuth, nickel, zinc, gold, indium and arsenic. The presence of traces of copper and iron are a strong indication that the crude tin mixture was obtained as a by-product of copper production by a pyrometallurgical process. Accepting small amounts of the listed metals provides raw material flexibility for the upstream processes that provide the crude tin mixture as a base material for the crystallization step. Applicants have found that many of the listed metals exhibit a tendency to at least partially end up in the bleed stream, and sometimes even concentrate in the bleed stream, and thereby be at least partially removed from the main inflow, thus more readily producing a high quality tin product of high purity can be derived.
In one embodiment of the method of the present invention, the crude tin mixture comprises at least 99.0% by weight together of tin, lead, antimony and silver, preferably at least 99.1% by weight, more preferably at least 99. 2% by weight, even more preferably at least 99.3% by weight, even more preferably at least 99.4% by weight, preferably at least 99.5% by weight, more preferably at least 99, 6% by weight, even more preferably at least 99.7% by weight together of tin, lead, antimony and silver. This has the advantage that the crude tin mixture contains less of other materials, which could potentially impose a burden on the further processing of the crystallizer products and / or form a contamination in at least one of the high-value products that can be used therefrom. being distracted.
In one embodiment of the method of the present invention, the crude tin mixture is obtained at least in part as the first bottoms product from a first distillation step in which lead (Pb) is removed from a molten solder mixture by evaporation,
whereby a first concentrated lead stream is obtained as the top product. Applicants have found that the feed to the crystallizer can be very conveniently obtained as a bottom product of a vacuum distillation of a solder mix, from which the distillation removes most of the lead by evaporation. Applicants prefer to perform this first distillation step as described in the patent WO 2018/060202 A1. In one embodiment of the process of the present invention, a suitable fresh feed is also added as an additional feed to the crystallizer step.
In one embodiment of the process of the present invention, at least one product from the liquid end of at least one crystallizer in the fractional crystallization step is at least partially recycled to the feed of the first distillation step, preferably the liquid draw-off stream from the crystallizer that is most upstream of the flow of tin through the fractional crystallization step. Applicants have found that this provides an additional power to reduce the presence of lead in the fractional crystallization step such that the amount of net bleed stream to be removed from the silver recovery process and the concentration of silver can be reduced. in it can be further increased. In addition, this recycle broadens the acceptable base materials to materials with a lower content of silver.
In one embodiment of the method of the present invention, the first bottoms product from the first distillation step comprises at least 0.1% by weight of lead, preferably at least 0.15% by weight or even at least 0.20% by weight, with more preferably at least 0.30 wt%, even more preferably at least 0.40 wt%, even more preferably at least 0.50 wt%, preferably at least 0.60 wt%, with more preferably at least 0.70 wt%, even more preferably at least 0.80 wt%, preferably at least 0.90 wt%, and more preferably at least 1.00 wt%. This entails the advantage that the first bottoms product is even more suitable as feed material for the fractional crystallization step, and meets the desired properties described elsewhere for the feed material to the fractional crystallization step. In one embodiment of the method of the present invention, the first silver-enriched liquid draw-off product is subjected to a fourth distillation step in which lead is removed by evaporation to a fourth lead concentrate stream as a distillation overhead product, thereby producing a fourth distillate bottoms product. Applicants have found that the first silver-enriched liquid tap product can be further concentrated without difficulty by removing most of the lead contained therein by vacuum distillation. Applicants have found that this vacuum distillation can be performed in batch mode without any problems, which is useful when the volume of supply is limited. Applicants have further found that the top condensate from this fourth vacuum distillation can be imparted with a suitable quality, comparable to the first concentrated lead stream obtained in the first distillation step, and can be mixed therewith and further processed together with it to form a obtain a high quality soft lead product as outlined elsewhere in this document. Applicants have found that due to this fourth distillation step, the concentration of silver in the fourth bottoms product can be significantly higher than the content of silver in the feed to the fourth distillation step.
In one embodiment of the process of the present invention, the fourth distillation bottoms product is subjected to a fractional crystallization step that yields a second silver-enriched bleed product at the liquid end and a second tin-enriched product at the crystal end. Applicants find it convenient to reduce not only the lead but also the tin content in the silver-containing stream before it is subjected to further processing for the recovery of the silver. Applicants have found that an additional crystallization step is highly appropriate because it is capable of removing most of the tin in the second tin-enriched product at the crystal end, while leaving a much smaller volume of second silver-enriched tap-off product to proceed further. are processed for the recovery of silver. The second tin-enriched product may still contain a small amount of lead, and is suitable for admixture into the crude tin mixture as a feed to the fractional crystallization step leading to the first tin-enriched product.
In one embodiment of the method of the present invention, the first silver-enriched liquid tap product or the second silver-enriched liquid tap product is used as a feed to be cast into at least one anode that is subjected to an electro-refining step to obtain a cathode product which is rich in lead plus tin, and an anode glue which is rich in silver, the anode glue preferably adhering to the used anode and being removed therefrom by mechanical means. Applicants have found this step to be very useful for obtaining a current into which the silver enters in a more concentrated form, i.e. the anode slime obtained from this electro-refining step, which easily contains about weight% silver, and can be labeled as a high-quality silver-containing product. Applicants note that the methods for this electro-refining step are known in the art, such as using an electrolyte based on hexafluorosilicic acid (HzSiFe), fluoroboric acid and / or phenyl sulfonic acid; a temperature of about 35-40 ° C; a current density in the range of 140-200 A / m : and a spacing between electrodes of about 100 mm. Applicants further note that the electrolysis step is particularly advantageous when the anode glue is caused to stick to the used anode such that the used anode can be pulled out of the bath and the anode glue removed from the used anode by mechanical means. , such as by scraping.
In one embodiment of the method of the present invention, the at least one anode used in the electro-refining step to obtain a cathode product rich in lead plus tin comprises at least 0.5% by weight of antimony, preferably at least 1, 0 wt% and more preferably at least 1.5 wt% antimony. Applicants have found that this presence of antimony has the advantage that the anode glue will stick to the anode instead of being dispersed in the electrolyte. This facilitates the recovery of the anode adhesive. Applicants have found that the preferred antimony content can be obtained without any problems by, if there is not enough antimony present in the stream intended to be cast into anodes, adding an appropriate amount of Pb / Sb concentrate, such as an amount of the high quality hard lead product obtained as one of the high value end products of the global process comprising the process of the present invention as described.
In one embodiment of the method of the present invention, the molten solder mixture fed to the first distillation stage is obtained by pretreating a crude solder composition containing at least 90% by weight of tin and lead together. Applicants have found such crude brazing compositions to be readily available, for example as a by-product of the pyrometallurgical recovery of copper, such as from secondary feedstocks. Applicants prefer to carry out this pretreatment as described in WO 2018/060202 A1.
In one embodiment of the method of the present invention, the crude solder composition comprises at least 0.16% by weight and optionally at most 10% by weight of the total chromium (Cr), manganese (Mn), vanadium (V), titanium (Ti), tungsten (W), copper (Cu), nickel (Ni), iron (Fe), aluminum (Al) and / or zinc (Zn), the pretreatment comprising the step of cooling the crude solder composition to a temperature of not more than 825 ° C to produce a bath containing a first supernatant scratch that floats by gravity on a first liquid molten metal phase. This step has the advantage of removing much of the copper that may be present in the crude solder composition.
In one embodiment, the method of the present invention further comprises the step of adding a compound selected from an alkali metal and / or an alkaline earth metal, or a chemical compound comprising an alkali metal and / or an alkaline earth metal, to the first liquid molten metal phase to form a bath containing a second supernatant scratch that floats by gravity on a second liquid molten metal phase, and removing the second supernatant scratch from the second liquid molten metal phase to obtain the molten solder mixture. This step entails the advantage of removing most of the zinc that may be present in the crude solder composition.
In one embodiment, the method of the present invention further comprises the step of removing the first supernatant scratch from the first liquid molten metal phase.
This scratch can be easily recycled to a suitable pyrometallurgical process step upstream, such that its metal values can be recovered.
In one embodiment of the method of the present invention, at least one product from the liquid end of at least one crystallizer in the fractional crystallization step is at least partially recycled to the raw solder pretreatment step feed. This brings the advantage that the concentration of copper in the process of the present invention, which may have increased due to the leakage of copper in the feed of the first distillation step and may have penetrated into the fractional crystallization step, is reduced again because the copper in the recirculation is allowed to exit the process with the first and / or the second supernatant scratch separated in the rough solder pretreatment step.
In one embodiment of the method of the present invention, the method of obtaining the crude solder composition comprises a metal melting step and at least one of the first and / or the second supernatant scratch is recycled to the melting-out step, preferably with both of the scratches being recycled. recycled to the melting out step. This has the advantage that the intended metal values, such as Cu, Ni and / or Zn, but also entrained Sn, Pb, Sb and / or Ag, can be recovered and upgraded to a suitable high-quality product.
In one embodiment of the method of the present invention, the molten solder mixture supplied to the first distillation step comprises, on a dry weight basis: ° more lead than tin, ° not more than 0.1% of the total chromium (Cr), manganese (Mn), vanadium (V), titanium (Ti) and tungsten (W), ° maximum 0.1% aluminum (AI) ° maximum 0.1% nickel (Ni) ° maximum 0.1% iron ( Fe), and ° not more than 0.1% zinc (Zn).
This brings the advantages of (i) facilitating the pretreatment process because the main solder stream has a high liquid density, which helps to obtain a clear separation between any supernatant scratch and the liquid phase below it, and (ii) that the first distillation step is able to function flawlessly, ie
with little risk of solid metal-metal compounds forming during distillation, which would deposit on the inside of the equipment and hinder the flow of fluids from the distillation equipment.
In one embodiment of the method of the present invention, the molten solder mixture fed to the first distillation step comprises, on a dry weight basis: at least 1 ppm by weight and at most 5000 ppm by weight of copper.
The inventors have further found that the potentially harmful metals, and in particular copper, do not need to be completely removed from the braze mix to make the braze mix suitable for vacuum distillation. For example, the inventors have found that the problems identified can be reduced to a practical and economically acceptable level when small amounts of copper remain in the solder feed to the first distillation stage. This finding has the advantage that solder streams can be processed that occur as the by-product of the recovery of copper from primary and / or secondary base materials, in particular from secondary base materials, and more importantly from raw materials that are end-of-life materials. use cycle.
In one embodiment of the present invention, the molten solder mixture fed to the first distillation step comprises at least 0.0001 weight% sulfur (S). Applicants have also found that it is not necessary to reduce sulfur levels to very low levels, such as below the 1 ppm by weight detection limit. On the contrary: the presence of sulfur in the metal mixture has an advantageous technical effect.
Applicants have found that sulfur binds with copper quite readily to form a copper sulfide (such as CuS), and that the copper sulfide is easily separated by gravity from the liquid metal mixture containing the two major components in the process, i.e., tin and lead. The presence of sulfur is therefore able to aid in the removal of Cu in any process step that aims to separate Cu, or separate Cu, in a supernatant scratch.
The presence of sulfur in the metal mixture of the present invention is therefore a strong indication that the metal mixture of the present invention has been produced as a by-product of a copper production process. Therefore, the feedstock for the first distillation step may contain measurable amounts of copper as impurity, such as the content indicated here. The copper content of such effluents can be reduced by several possible process steps, of which the binding of Cu to S is only one. When treated with S for the removal of Cu, there is a very high probability that measurable traces of S remain in the metal mixture. The presence of S in the metal mixture of the present invention therefore provides a strong relationship with the production of the metal mixture as a by-product of copper production,
preferably with a step comprising treatment with sulfur or a suitable S-containing compound.
Applicants have further found that the presence of sulfur in the feed to the first distillation stage is not harmful, provided that there is also an amount of copper present as indicated. The presence of S can contribute in subsequent cleaning steps to the removal of Cu from the less noble metal streams on their way to an industrially acceptable quality. The S in the metal mixture of the present invention is therefore a desirable presence, with advantages manifested downstream.
In one embodiment of the process of the present invention, the fourth concentrated lead stream obtained as an overhead product from the fourth distillation step is combined with the first concentrated lead stream to obtain a fifth concentrated lead stream. Applicants have found that the fourth concentrated lead stream, which is recovered from the processing of the liquid draw-off stream from the fractional crystallization step, can be easily combined with the first concentrated lead stream obtained as the top stream from the first distillation step, and without much additional effort. lead to a higher yield of high-quality soft lead product.
In one embodiment, the method of the present invention further comprises the step of removing at least one contaminant selected from the metals arsenic, tin and antimony from a concentrated lead stream selected from the first concentrated lead stream, the fourth concentrated lead stream, and the fifth concentrated lead stream to obtain a purified high quality soft lead product. Applicants have found that any of the listed concentrated lead streams is highly suitable for obtaining high quality soft lead products that meet requirements with a limited number of chemical refining steps, a limited consumption of chemicals and a limited burden for reprocessing by-products. for important end uses for such products. Applicants have found that, by means known in the art, a high performance soft lead product can be derived from any of the first, fourth and fifth concentrated lead streams by removing arsenic, tin and / or antimony. Preferably, Applicants perform this soft lead refining step as described in copending patent application EP 19154606.8.
In one embodiment of the present invention, the at least one contaminant is removed by treating the concentrated lead stream at a temperature of less than 600 ° C with a first base and a first oxidant, resulting in the formation of a third supernatant scratch which contains a metalate compound of the relevant contaminant metal, followed by separating the scratch from the purified soft lead stream or the purified soft lead product.
In this soft lead refinery, the crude Pb feed stream is preferably contacted with a combination of NaOH and NaNOs. The chemical process envisaged with these chemicals can be represented by the following reactions: 5 Pb + 6 NaOH + 4 NaNO: 3 -> 5 Na2PbO3 + 2 Ns + 3 H: O (1) 5 Na2PbO3 + 4 As + 2 NaOH -> 4 NasAsO4 + 5 Pb + H2O (IN) Na2PbOs3 + Sn -> Na2SnO3 + Pb (II) 5 NazPbO; + 3 H2O + 4 Sb -> 4 NaSbO3 + 6 NaOH + 5 Pb (IV) Crucial to this chemical process is the formation of the intermediate sodium plumbate (Na: PbOs) by reaction (|). This plumbate intermediate is capable of reacting with the impurities As, Sn and Sb according to the respective reactions (II) to (IV) and each time entraps them in the respective sodium metalate compound, while releasing the Pb again. The sodium metalate compounds formed are sodium arsenate, sodium stannate and sodium antimonate, respectively.
The respective sodium metalate compounds collect in a supernatant phase, commonly referred to as the "scratch" or sometimes also "slag". Those terms are often used interchangeably, although the term "slag" is generally used for a liquid phase, while
"Scratch" usually means a phase with a less fluid, firmer consistency. The term "slag" is more common in the context of the production of nonferrous metals with a high melting point, such as copper, and thus usually refers to a fluid, which often mainly comprises metal oxides. The term "scratch" is more commonly used in the context of lower melting point non-ferrous metals such as Sn, Pb, Zn, Al, which are often in solid or dust form. However, the boundary between these two terms in terms of consistency is not always clear.
The scratch from the soft lead refining step can be skimmed off, and can be further processed to recover at least some of its components.
In one embodiment of the method of the present invention, the third supernatant scratch comprises at most 1.0% by weight of chlorine, and preferably at most 1.0% by weight of total halogens.
Applicants have found that the stated low content of chlorine and / or other halogens in the third supernatant scratch makes the third supernatant scratch more suitable to be introduced in an upstream pyrometallurgical process step, preferably in a process step in which at least one of the sodium metalates of Sn, Sb and As can be reduced to the respective metal Sn, Sb or As, with the Pb also preferably ending up in its elemental form.
The third supernatant scratch is more acceptable in a pyrometallurgical process step due to its limited chlorine and / or halogen content. The low chlorine content of the third supernatant scratch reduces the risk of valuable metals being entrained in the exhaust gas of a pyrometallurgical process step in which an exhaust gas is produced, and thus also reduces the risk of sticky solid deposits forming on cooling devices, filters and others. pieces of equipment in the exhaust gas treatment equipment associated with such a pyrometallurgical process step.
In one embodiment of the method of the present invention, the third supernatant scratch is recycled to a process step upstream of the first vacuum distillation step. This entails the advantage that the metal values, in particular any entrained lead, can be easily recovered as part of one of the intended high-quality products of the method according to the present invention. Much of the lead entrained in the third supernatant scratch may preferentially become part of the high performance soft lead product or, if necessary, may be made to enter the third concentrated lead stream described elsewhere in this document , and become part of the high performance hard lead product.
The advantage of this scratch recycle capability is that it allows for a general process of much lower complexity, especially when compared to the highly complex wet chemical recovery ranges described in U.S. Patent No. 1,674,642.
The ability of the third supernatant scratch to be recycled to a pyrometallurgical process step makes it possible to simultaneously, in a single process step, remove more than one impurity from the first concentrated lead stream, in this case As, Sb and Sn together. This represents a significant improvement over the many complex lead refining steps described in the art.
In one embodiment of the process of the present invention, the first tin-enriched product is subjected to a second distillation step which, by evaporation, separates predominantly lead and antimony from the first tin-enriched product, producing a second concentrated lead stream as the top product and a second bottom product is produced.
In one embodiment of the method of the present invention, a fresh feed containing lead is added to the feed of the second distillation step. Applicants have found that an amount of lead is desired in the feed to the second distillation step because more lead dilutes the vapor phase in the distillation step. This has the advantage that the evaporation of antimony is promoted in the second distillation step, thereby improving the quality of the separation that can be obtained in the second distillation step. The lead dilutes the vapor phase in the distillation step and thus acts as a kind of carrier for the antimony. As a result, the lead promotes the removal of antimony from the main tin stream and thereby contributes to the ultimate obtaining of a high purity, high quality tin product.
In one embodiment of the process of the present invention, the second concentrated lead stream is subjected to a third distillation step that separates predominantly lead and antimony from the second concentrated lead stream by evaporation, thereby producing a third concentrated lead stream as an overhead product and a third bottoms product being produced. Applicants have found that the second concentrated lead stream as the top stream of the second distillation step provides an extremely suitable basis for obtaining a high quality hard lead product, because the tin entrained in this stream can be easily removed from most of the lead and antimony by another distillation step. The third distillation step can focus entirely on the selective evaporation of antimony, and lead, if any, from the feedstock to the third concentrated lead stream as its overhead stream.
In one embodiment of the method of the present invention, a fresh feed containing lead is added to the feed of the third distillation step. Applicants have found that some amount of lead is also desirable in the feed to the third distillation stage, because the lead promotes the evaporation of antimony. This has the advantage that the evaporation of antimony is promoted in the third distillation step, thereby improving the quality of the separation that can be obtained in the third distillation step. The lead dilutes the vapor phase in the distillation step and thus acts as a kind of carrier for the antimony.
As a result, the lead promotes the recovery of most of the antimony in the third concentrated lead stream and thereby contributes to the efficient production of the high quality hard lead product.
For example, the second concentrated lead stream may contain about 40/40/20 weight% Pb / Sn / Sb.
Applicants have found that this feed composition can be further improved.
Applicants prefer to dilute the feedstock for the third distillation step by adding lead-containing fresh feed to about 10-12 weight% Sb and / or 18-10 weight% Sn.
Applicants have found that this produces more vapor phase in the third distillation step, and also lowers the melting point of the feed.
This allows better removal of Sb to the third concentrated lead stream as top stream, from the Sn remaining in the third bottoms product.
The additional advantage is that if the third bottoms product is recycled to a location upstream of the second distillation stage, the better separation in the third distillation stage reduces the amount of antimony circulating over the second and third distillation stages.
In one embodiment of the method according to the present invention, the third bottoms product is at least partially and preferably completely recycled to the feed of the second distillation step and / or to the feed of the fractional crystallization step.
Applicants have found that the third bottoms product has an extremely suitable composition to be recycled to at least one of the indicated locations upstream in the process of the present invention, due to its high purity in terms of valuable metals and low content of unintended metals in the third bottoms.
This has the advantage that the valuable metals can be recovered in the designated high-quality products without high process costs.
Applicants prefer to make the selection of the process site for recycling the third bottoms product dependent on the silver content of the stream, because the fractional crystallization step is able to remove silver and thereby reduce the accumulation of silver in the stream. process beyond acceptable levels.
In one embodiment, the method of the present invention further comprises the step of removing at least one contaminant selected from the metals arsenic and tin from the third concentrated lead stream, thereby producing a purified hard lead stream as a hard lead product. Applicants have found that the third concentrated lead stream can be further refined by means known in the art to obtain a purified hard lead stream as the hard lead product.
In one embodiment of the method of the present invention, the at least one impurity is removed from the third concentrated lead stream by treating the third concentrated lead stream at a temperature of less than 600 ° C with a second base and a second oxidant, resulting in until the formation of a fourth supernatant scratch containing a metalate compound of the affected contaminant metal, followed by separating the fourth supernatant scratch from the purified hard lead stream.
The third concentrated lead stream is preferably contacted with a combination of NaOH and NaNOs. The chemical process aimed at with these chemicals can be represented by the following reactions: 5 Pb + 6 NaOH + 4 NaNO: 3 -> 5 Na2PbO3 + 2 Ns + 3 H: O (1) 5 Nas2PbOs + 4 As + 2 NaOH -> 4 NasAsO4 + 5 Pb + H: O (I) Na2PbOs3 + Sn -> Na2SnO3 + Pb (II) Crucial to this chemical process is the formation of the intermediate sodium plumbate (Na: PbOs) by reaction (|). This plumbate as intermediate is capable of reacting with the impurities As and / or Sn according to the respective reactions (II) to (III) and each time entraps them in the respective sodium metalate compound, while releasing the Pb again. The sodium metalate compounds formed are sodium arsenate and sodium stannate, respectively.
The respective sodium metalate compounds collect in a supernatant phase, commonly referred to as the "scratch" or sometimes also "slag".
The fourth supernatant scratch can be skimmed, and processed further, preferably in an upstream process step, to recover at least some of its components.
In one embodiment of the method of the present invention, the fourth supernatant scratch comprises at most 1.0% by weight of chlorine, and preferably at most 1.0% by weight of total halogens.
Applicants have found that the stated low content of chlorine and / or other halogens in the fourth supernatant scratch makes the scratch more suitable for introduction into an upstream pyrometallurgical process step, preferably to a process step in which at least one of the sodium metalates of Sn and As can be reduced to the respective metal Sn or As, preferably also getting the Pb in its elemental form.
The fourth supernatant scratch is more acceptable in a pyrometallurgical process step due to its limited chlorine and / or halogen content. The low chlorine content of the scratch reduces the risk of valuable metals being entrained in the exhaust gas of a pyrometallurgical process step in which an exhaust gas is produced, and thus also reduces the risk of sticky solid deposits forming on cooling devices, filters and other pieces of equipment in the exhaust gas treatment equipment associated with such a pyrometallurgical process step.
In one embodiment of the method of the present invention, the fourth supernatant scratch is recycled to a process step upstream of the first vacuum distillation step. This entails the advantage that the metal values, in particular any entrained lead, can be easily recovered as part of one of the intended high-value products of the method according to the present invention. Much of the lead entrained in the fourth supernatant scratch may preferably become part of the high performance soft lead product or, if necessary, be recycled to the third concentrated lead stream to become part of the high performance hard lead product. The advantage of this scratch recycle capability is that it allows for a general process of much lower complexity, especially when compared to the highly complex wet chemical recovery ranges described in U.S. Patent No. 1,674,642.
The suitability of the fourth supernatant scratch to be recycled to a pyrometallurgical process step makes it possible to simultaneously remove, in a single process step, more than one impurity from the first concentrated lead stream, in this case As and Sn together. This represents a significant improvement over the many complex lead refining steps described in the art.
In one embodiment of the method of the present invention, the third concentrated lead stream comprises at least 0.50 wt.% And at most 15.0 wt.% Antimony. The presence of antimony in the range as indicated has the advantage of improving the properties of the high performance hard lead product derived from the third concentrated lead stream in view of the end uses where hard lead is preferred over soft lead.
In one embodiment of the process of the present invention, the second bottoms product is further refined to obtain a high purity high quality tin product. Applicants have found the second bottoms product to be highly suitable for further refining to obtain a high purity tin product of excellent economic value.
In one embodiment of the method of the present invention the second bottoms product is treated with aluminum metal, preferably in stoichiometric excess to the amount of antimony present, preferably in combination with mixing and cooling the reacting mixture to less than 400 ° C followed by separating the scratch containing Al / Sb / As formed by the treatment.
Applicants have found that the aluminum readily forms solid metal-metal compounds with trace impurities in the tin stream, especially with antimony.
Applicants prefer to use a stoichiometric excess of aluminum because it is more effective in removing antimony and removes any remaining aluminum with little trouble, as described later in this document.
Mixing and cooling stimulates the reaction and aids the separation of the formed solids from the molten tin.
Applicants prefer to cool to a temperature of about 250 ° C as they have found that this provides a better balance between the reaction kinetics, which is promoted by high temperatures, and improved separation, which is promoted by lower temperatures. .
The formed scratch, containing Al / Sb / As, can be skimmed and recycled to an upstream pyrometallurgical process step.
Applicants prefer to collect the scratch containing Al / Sb / As in steel drums that are closed and sealed to avoid contact of the scratch with water, which could lead to the formation of the highly toxic arsine gases and / or stibine.
The aluminum is preferably added in granular form, which provides a large surface area without causing dust problems.
Applicants prefer to add the granules to a bath without vigorous mixing, preferably static, to prevent wet granules from exploding from the sudden contact with the hot liquid tin.
In an embodiment of the method according to the present invention, the second bottom product, after the treatment with aluminum and preferably also after the removal of the scratch containing Al / Sb / As, is treated with a third base, which is preferably selected from NaOH,
Ca (OH) 3 and NasCO3 and combinations thereof, more preferably NaOH, followed by separation of the scratch containing base formed by the treatment. Applicants prefer to skim off the scratch containing Al / Sb / As before the addition of the third base in order to require less of that base. Applicants prefer to use NaOH as the third base because it forms a sodium aluminate scratch that is more acceptable for recycling to an upstream pyrometallurgical process step. Applicants prefer to perform this treatment iteratively, in successively repeated steps, and based on an analysis of the aluminum content in the tin stream, in order to save on the consumption of chemicals. The contemplated chemistry can generate hydrogen gas, so Applicants prefer to throw a quantity of sulfur grains onto the reacting liquid such that the sulfur ignites at the high process temperatures and burns the hydrogen that may have evolved from the reaction. The scratch can be stiffened by adding silicon dioxide, preferably in the form of sand.
In one embodiment of the method of the present invention, after the treatment with the third base, the second bottom product is treated with sulfur, followed by the separation of the scratch containing S formed by the treatment. The sulfur reacts with the sodium and forms a Na2S scratch. At the end of this treatment, Applicants prefer to intensify the stirring speed to attract more oxygen from the ambient air, oxidizing the sulfur remaining after the reaction, and the sulfur oxides that are formed can easily escape from the liquid end product.
In one embodiment of the method according to the present invention, at least part of the method is electronically monitored and / or controlled, preferably by a computer program. Applicants have found that electronically controlling steps of the method of the present invention, preferably by a computer program, brings the benefit of much better processing, with results that are much more predictable and closer to the goals of the method. For example, on the basis of temperature measurements, if desired also measurements of pressure and / or level, and / or in combination with the results of chemical analyzes of samples taken from process flows and / or analytical results obtained online, the control equipment in terms of the supply or removal of electrical energy, the supply of heat or a cooling medium, control of a flow and / or a pressure. Applicants have found that monitoring or controlling in this manner is particularly advantageous in steps performed in continuous mode, but that it may also be advantageous in steps performed in batch mode or semi-batch mode. In addition, the monitoring results obtained during or after performing steps in the method according to the present invention can preferably also be used to monitor and / or control other steps as part of the method according to the present invention, and / or of processes used upstream or downstream of the process of the present invention, as part of a general process in which the process of the present invention is only one part. Preferably, the entire process is electronically monitored as a whole, more preferably by at least one computer program. Preferably, the method as a whole is electronically controlled as much as possible. Applicants prefer that the computer control also provides for data and instructions to be passed from one computer or computer program to at least one other computer or computer program or module of the same computer program, for monitoring and / or controlling other processes including, but not limited to, the methods described in this document.
EXAMPLE The following example shows in more detail how the method of the present invention can be carried out and how the intended effect is obtained. The example also shows how the method of the invention can be part of a larger global process that yields more high-quality products. The enclosed Figure 1 shows a flow chart of the method steps and their sequence as performed in this example. The compositions reported in the example are expressed in units of weight, and were the result of analyzes of samples taken daily, the results being averaged over an operating time of 73 days. In Figure 1, the numbers refer to the following elements of the claims:
1. Crude solder composition as feed to the pretreatment step 100
2. NaOH added in the pretreatment step 100
3. Sulfur added in the pretreatment step 100
4. First supernatant scratch from pretreatment step 100
5. Second supernatant scratch from pretreatment step 100
6. Molten braze mix obtained from pretreatment step 100
7. First concentrated lead stream as top stream from vacuum distillation step 200
8. First bottoms from the first vacuum distillation step 200
9. First silver-enriched liquid bleed product from the liquid end of crystallization step 300
10. First tin-enriched product from crystallization step 300
11. Fresh feedstock added to second vacuum distillation step 400
12. Second concentrated lead stream as overhead product from second vacuum distillation step 400
13. Second bottoms from second vacuum distillation step 400
14. Aluminum nuggets to tin refining step 500
15. Third base added in tin refining step 500
16. Sulfur added in tin refining step 500
17. Scratch containing Al / Sb / As from tin refining step 500
18. Scratch containing base from tin refining step 500
19. Scratch containing sulfur from tin refining step 500
20. High purity tin product from tin refining step 500
21. Third concentrated lead stream overhead from third vacuum distillation step 600
22. Third bottoms, from third vacuum distillation step 600
23. Copper added to soft lead refining step 700
24. First base added in soft lead refining step 700
25. First oxidant added in soft lead refining step 700
26. Third supernatant scratch formed in soft lead refining step 700
27. Purified soft lead stream or purified soft lead product from soft lead refining step 700
28. Purified hard lead stream or product from hard lead refining step 800
29. Remains of top product 21 from previous campaigns
30. Second base added in hard lead refining step 800
31. Second oxidant added in hard lead refining step 800
32. Fourth supernatant scratch formed in hard lead refining step 800
33. Fresh feedstock added to crude solder 100 pretreatment step
34. Fresh feedstock added to third vacuum distillation step 600
35. Fresh feedstock added to fractional crystallization step 300
36. Fresh Feed Adds to First Vacuum Distillation Step 200 100 Pretreatment Step 200 First Vacuum Distillation Step 300 Fractional Crystallization Step 400 Second Vacuum Distillation Step 500 Tin Refining Step 600 Third Vacuum Distillation Step 700 Soft Lead Refining Step 800 Hard Lead Refining Step For the analysis of a molten metal stream, a sample of molten metal is taken into a cast metal stream. refrigerated to solidify. One surface of the solid sample is prepared by passing the sample once, or preferably several times, through a Herzog HAF / 2 grinder until a clean and flat surface is obtained. The clean and flat surface of the sample is then analyzed by means of an optical emission spectroscopy (OES) device with breakdown spark of the Spectrolab M type from Spectro Analytical Instruments (US), which is also available from Ametek (DE ), where the parameters, crystals, detectors and tube can be readily selected and adjusted to obtain the most suitable operation for the desired accuracy and / or detection limit. The analysis provides results for several metals in the sample, including copper, bismuth, lead, tin, antimony, silver, iron, zinc, indium, arsenic, nickel, cadmium and even the element sulfur, and that, for most of those metals, up to a detection limit of about 1 ppm by weight. For the analysis of a scratch, the inventors preferably use a well-calibrated X-ray fluorescence technique (XRF technique), preferably using the XRF spectrometer of the PANalytical Axios type from PANalytical B.V. (NL). This technique is also preferred over the above-mentioned OES for analyzing samples of metals containing significant amounts of impurities, such as stream 6 and streams upstream thereof, in the flow chart in the attached Figure 1. Also in this technique the details can be easily selected. and adapted to optimize the results in terms of the most appropriate accuracy and / or limit of detection for the purpose of the analysis.
The crude solder stock 1 was obtained from the refining of materials containing copper, lead and tin in a copper smelting furnace (not shown) which produces as an intermediate material a "black copper" containing about 85% by weight Cu. This black copper was then subjected in a copper refinery to a series of pyrometallurgical refining steps (not shown) that produce a high purity copper product on the one hand and a number of slag binder products on the other. In the course of the refining process, the crude brazing raw material 1 is recovered from some of those refining slags. Purification of that crude solder was accomplished through a series of pretreatment steps 100 to remove a significant amount of the metal impurities present that would otherwise be in danger of being harmful in the downstream vacuum distillation steps.
The target impurities of the purification steps are mainly Cu, Fe, Ni and / or Zn, and the purpose of the purification of the crude solder to acceptable levels is that the solder can be further processed smoothly and without problems using vacuum distillation .
The crude solder 1 was available from the upstream refining processes at a temperature of about 835 ° C.
In a first step of the purification process sequence 100, the solder was cooled to 334 ° C, which occurred in two steps.
In the first cooling step, the crude solder was cooled to about 500 ° C and a first scratch was removed from the surface of the molten liquid metal.
In the second cooling step, the crude solder was further cooled to 334 ° C and a second scratch was removed from the surface of the molten liquid metal. The cooling step resulted in the formation of a total scratch containing most of the copper present in the crude solder, which was removed as by-product (not shown) and recycled in one of the upstream pyrometallurgical process steps.
The total flow rate and the concentrations of target metals in the remaining brazing intermediate (flow 1) are shown in Table 1. The copper content in the braze was reduced to an average of 3.0000 weight% by this series of cooling steps and scratch removals. The concentrations of Fe and Zn in the solder were also significantly reduced.
Any scratch phases formed during the cooling process were removed (not shown) and recycled upstream in the process to the melting out step so that the valuable metals contained therein could be valorized as much as possible.
Table 1: The crude solder after the cooling step Weight% Crude solder 1 Bi | 0.0163 3.0000 0.0007 0.0015 Pb | 69.5000 0.8305 26.7414 0.0028 0.0290 0.0010 0.0515 0.0010 0.0125 0.0025 0.0007 100.1914 In a second part of the purification process sequence 100 solid sodium hydroxide (stream 2) was added to the solder intermediate of Table 1. In this treatment step, zinc was bound by the sodium hydroxide, presumably to form Na2ZnO2, and formed a separate phase that separated from the solder as a first supernatant solid scratch and became removed as stream 4. As a result, the content of zinc in the solder stream 6 was further reduced.
The amount of sodium hydroxide was adjusted so that the concentration of Zn in the solder was reduced to 13 ppm by weight (Table 2). The scratch formed in this step was also recycled (stream 4) to the upstream smelting step, where zinc can be fumigated and recovered as zinc oxide dust.
In the next part of the purification process sequence 100, after the addition of sodium hydroxide and the removal of the first supernatant solid scratch phase 4, an amount of elemental sulfur was also added (stream 3), which represented about 130% stoichiometry relative to the amount of copper present in the metal phase, to further reduce the copper content of the solder.
The elemental sulfur used was a granulated form of sulfur available from Zaklady Chemiczne Siarkopol in Tarnobrzeg (PL). The sulfur 3 reacted mainly with copper to form copper sulfides, which turned into a second supernatant scratch.
That second supernatant scratch was then removed as stream 5 and recycled to a suitable upstream process step.
After the addition of sulfur in step 100, an additional amount of sodium hydroxide (stream 2) was added to chemically bind any remaining traces of sulfur, and form another scratch.
After some time for the reaction to take place, a handful of granular sulfur 3 was sprinkled / spread over the surface of the bath.
The sulfur caught fire and burned any hydrogen that might have evolved from the liquid as a byproduct of the reaction.
Then, a small amount of white sand was scattered / spread over the bath to dry / stiffen the scratch before removing it from the process (stream not shown in the drawing) and recycling it to an upstream process step.
The purified solder thus obtained (stream 6, the flow rate and composition of which are indicated in Table 2) contained only 38 ppm Cu and was further processed as the molten solder mixture obtained from pretreatment step 100 by vacuum distillation in step 200. The second supernatant scratch 5 was reprocessed in the upstream refining process so that the valuable metals contained therein could be valorized.
Table 2: Purified solder for vacuum distillation Weight% Molten solder mixture -6
Bi | 0.0326
0.0038
0.0004
0.0009
Pb | 73.1206
0.8012
25.8694
0.0013
0.0500
0.0871
0.0015
0.0020
0.0202
0.0053
0.0010
99.9973 The molten solder mixture 6 was further processed by vacuum distillation (step 200), at an average temperature of 982 ° C and an average absolute pressure of 0.012 mbar (1.2 Pa). The vacuum distillation step yielded two product streams.
On the one hand, as top stream 7, a first concentrated lead stream was obtained which mainly contained lead, and on the other hand, as the first bottom product 8 of the first distillation step 200, we obtained a product stream containing mainly tin.
The flow rates and compositions of these second distillation product streams 7 and 8 are indicated in Table 3.
Table 3: Product flows from the first vacuum distillation 200 7 8 Bi | 0.0425 0.0014 0.0000 0.0122 0.0000 0.0015 0.0000 0.0028 Pb | 99.5375 1.0055 0.2233 1.9800 0.1006 96.3129 0.0018 0.0001 0.0031 0.1400 0.0746 0.0700 0.0000 0.0043 0.0024 0.0000 0. 0057 0.0460 0.0071 0.0000 0.0014 0.0000 100.0000 99.5767 The first vacuum distillation step 200 was performed in continuous mode, and was able to continue to function for a period of approximately three (3) years without observing any blocking or plugging of the distillation equipment due to the formation of metal-metal or intermetallic compounds.
The first concentrated lead stream 7 became available from the distillation equipment at a temperature of about 562 ° C. The temperature of stream 7 was controlled to about 450 ° C with stirring before the stream was further refined. Successive volumes of 100-120 tons of stream 7 were collected in a reservoir. Those volumes were subjected in batches to the soft lead refining process 700. A sample was taken from each batch and analyzed for the presence of As, Sn and Sb to determine the amounts of solid sodium hydroxide (stream 24) and solid sodium nitrate (stream 25) that were required. to react with the As, Sn and Sb present in the metal phase, and those amounts were added as the first base and first oxidant. The sampling and analysis was repeated over time for the reaction to take place and after removing the third supernatant scratch 26 formed by the reaction. If the result was not satisfactory, the method step was repeated. For the total volume of soft lead produced during the 73 day operating period, 29.3 tons of sodium hydroxide (401 kg / day) and 15.5 tons of sodium nitrate (212 kg / day) were used in the process to remove most of the the mean 46 kg / day As, 62 kg / day Sn and 138 kg / day Sb, in total mean 246 kg / day of the 3 elements together, present in the feed to step 700 with stream 7. This refining step constituted in each batch a third supernatant scratch phase containing most of the As, Sn and Sb present in the first concentrated lead stream 7 and removed as by-product (stream 26). The third supernatant scratch phase was sampled and analyzed for the presence of chlorine using the method according to the standard DIN EN 14582. The analysis showed that approximately 129 ppm by weight of chlorine was present. The high quality soft lead product 27 was then poured into molds and allowed to solidify and cool to lead ingots.
In most of the batches, a small amount of copper 23 was added in the feed to step 700 to produce an amount of Cu-containing soft lead. The small amount of copper present improves the mechanical properties of the soft lead, making the soft lead more suitable for being rolled into lead film for the construction industry or for plating surfaces with lead. Some batches containing above average levels of Bi were also separately stored as Bi-rich soft lead, which is acceptable in certain end uses and has the advantage of making Bi-containing basestocks more acceptable for the process of the present invention and / or for the upstream processes that provide feedstock for it. This soft lead refining was performed in batches in the same equipment as the hard lead refining discussed later. The transition between the cargoes of soft lead and hard lead produces a quantity of quality intermediate material, which is traded as “unrefined soft lead”. The average daily production rates (spread over the production period of 73 days discussed here) and compositions of the various soft lead end product streams 27 are indicated in Table 4. Table 4: Composition of the soft lead end products 27 (weight%) Soft lead | Unrefined With Cu Bi-rich products 27 soft lead labeled Soft lead Soft lead
Bi) 0.0905 0.0319 0.0568
0.0001 0.0428 0.0008
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
Pb | 99.6306 99.9026 99.9240
0.2279 0.0000 0.0000
0.0208 0.0006 0.0004
0.0001 0.0001 0.0001
0.0032 0.0034 0.0025
0.0259 0.0002 0.0002
0.0002 0.0000 0.0000
0.0007 0.0001 0.0001
0.0006 0.0003 0.0003
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
99.7727 99.9820 99.9852 The first bottoms product 8 from first vacuum distillation step 200 was mixed with the third bottoms product 22 from the downstream third vacuum distillation step 600 and the mixture was fed to the fourth zone of a first crystallizer with 12 temperature zones.
The crystallizer was a cylindrical vessel, slightly tilted from a fully horizontal position, and included an internal rotating screw to move the formed crystals from the bottom end to the top end of the cylindrical vessel.
The temperature zones were numbered 0 to 11 from the bottom end to the top end.
A temperature profile was established within the crystallizer using appropriate heating and cooling means.
The temperature of zone 3, into which the feed entered, was controlled maintained at about 210 ° C.
The temperature increased in steps from zone 3 to zone 11 (230-250 ° C), up the crystallizer, where the crystals rich in tin are removed from the device.
The temperature decreased slightly in the downward direction in the crystallizer from zone 3 to zone 0 (199 ° C), but rose again in zone 0, to about 220 ° C, to ensure that the temperature in that zone was always above the liquidus line in the phase diagram, such that solids build-up on the propeller blades was prevented, which could otherwise result in necessary technician intervention and temporary shutdown of the equipment.
Before the feed stream was supplied to the crystallizer, the stream was passed through a buffer vessel, with a delay of several hours from production, where mixing compensated for any temperature changes that might have occurred upstream such that the temperature of the feed entering the crystallizer entering zone 3 is fairly constant and any changes take place very slowly. In addition, the temperature of the feed to zone 3 was kept slightly higher than the temperature in zone 3 of the crystallizer to prevent the formation of solids in the feed system. By entering zone 3 of the crystallizer, the feed stream is cooled and enters the range where a stream of this composition separates into a solid phase of small crystals enriched in tin, in equilibrium with a liquid phase that is leaner in tin but richer in lead and precious metals. The increase in the temperature of the liquid moving down in the crystallizer from zone 1 to 0 brought the advantage of preventing the solids build-up on the outside of the blades of the screw in the lower part of the cylindrical container, leaving enough space under the vanes of the screw to allow fluid to flow from the top end of the cylindrical container to the bottom end.
The crystallizer was tilted such that the liquid phase in the vessel was readily able to move from the top end to the bottom end of the device under the force of gravity. The rotating screw in the crystallizer moved the crystals in the opposite direction through the continuous liquid phase contained in the crystallizer. The liquid level in the crystallizer was kept below the crystals overflow point to minimize liquid entrainment with the first tin-enriched product, but high enough to promote heat transfer from the vessel wall to the contents of the vessel. the barrel.
The crystals arriving at the top end were enriched in tin, and substantially all of the lead and precious metals from the feed was recovered in the liquid first bleed stream exiting the crystallizer at the bottom end.
The first bleed stream further contained tin in a significant amount, but at a concentration below the level of tin in the crystallizer feed.
The Sn crystals were removed from the top end of the first crystallizer and introduced into the fourth zone (again zone 3) of a second crystallizer which also had 12 temperature zones numbered from 0 to 11. The second crystallizer was also used. applied a temperature profile, similar to that in the first crystallizer, which caused further separation of a second liquid draw-off stream from the first tin-enriched crystals before those crystals exited the second crystallizer at the top end (stream 10). The antimony entering with the crystallizer feed mainly follows the path of the main inflow.
The bleed stream from the second crystallizer was recycled to the first crystallizer where it was mixed with the feed.
When the concentration of Pb was considered too high, the second crystallizer bleed stream was temporarily recycled to the upstream vacuum first distillation stage 200 feed to maintain a higher Ag concentration factor from vacuum distillation bottoms stream 8 to net first silver enriched liquid bleed product 9. Also As the concentration of Cu increased in the crystallizer streams, and thus also in the take-off stream of the second crystallizer, this take-off stream was - at least temporarily - preferably recycled to a process step further upstream than the feed to the first crystallizer, at Preferably to feed the first step of the purification process sequence 100, to be mixed with the crude solder composition 1.
The first silver-enriched liquid bleed product exited the first crystallizer as a Sn / Pb alloy by-product containing most of the Ag present in the crystallizer feed.
The flow rates and compositions of the outlet product streams 9 and 10 of the assembly of 2 crystallizers in step 300 are shown in Table 5. It was found that enrichment of Sb was also occurring in the first tin-enriched crystal phase exiting the second crystallizer, but some Sb was also recovered in the first silver-enriched liquid tap product.
The silver-enriched liquid draw-off product 9 of Table 5 represents the net draw-off volume and composition.
Temporarily, and depending on its composition, a recycle of the silver-enriched liquid bleed product was performed from the lower end of the first crystallizer to the feed of the first crystallizer, to further increase the Ag concentration factor of the crystallizer feed (flows 8 + 22) to the net first silver-enriched liquid draw-off product 9. Table 5: Product flows of the crystallizer assembly Weight% | First to | First silver enriched | tin enriched liquid product interception product 10 9
Bi | 0.0079 0.0010
0.2900 0.0014
0.0012 0.0016
0.0215 0.0023
Pb | 16.5000 0.2387
0.4020 2.1000
79.5000 97.0536
0.0042 0.0000
2.8000 0.0100
0.1144 0.0680
0.0001 0.0000
0.1039 0.0411
0.0000 0.0000
0.0000 0.0000
0.0129 0.0034
99.7581 99.5211
The net first silver-enriched liquid draw-off product 9 from the first crystallizer was transferred to a downstream purification step (not shown) to recover all the noble metals as well as the Sn and Pb.
To this end, the silver-enriched liquid tap product was poured into anodes and subjected to an electrolysis step to produce cathodes containing pure Pb and Sn, and the other metals remained in the anode adhesives.
Typical conditions of this electrolysis step are: an electrolyte based on hexafluorosilicic acid (H2SiFe), fluoroboric acid and / or phenyl sulfonic acid; a temperature of about 40 ° C; a current density of 140-200 A / m °; spacing between the electrodes of about 100 mm.
Antimony can be added to the anode composition, typically up to a concentration of about 1.5% by weight. This has the advantage that the anode adhesives remain attached to the anodes and are not dispersed in the electrolyte.
In order to avoid a complete passivation of the anode, which would lead to an inhibition of the electrolysis, periodically and consecutively a portion of the anodes can be removed from the bath, their anode adhesives removed, for example mechanically, and then the cleaned anodes then can be placed back in the cell.
The anodes can also be designed so that the cleaned anodes have become so thin that it is more efficient and / or effective to melt them into new anodes.
These anode adhesives (on average about 180 kg / day) were recovered, for example by filtration, from the entrained electrolyte, and these anode adhesives contained about 20% by weight of silver and also a much smaller concentration of gold, along with most of the other metals that were present in the first silver-enriched liquid tap product, including antimony and optional platinum group metals (PGMs). The anode adhesives were further processed to recover the silver and other precious metals.
The filtrate was recycled to the electrolytic cell.
The first tin-enriched crystals from the second crystallizer were further processed through the second vacuum distillation step 400, performed at an average temperature of 1049 ° C and an average absolute pressure of 0.005 mbar (0.5 Pa). Over the 73 day run period, an amount of 157.6 tons of lead-containing feedstocks 11, averaging about 2.2 tons per day, was gradually added to the first tin-enriched crystals to keep the solidification point of the top product from step 400 low.
The flow rate and composition of stream 11 are shown in Table 6. Table 6: Added feedstock in feed to the second vacuum distillation Weight% | Pb-containing feed materials 11 [Bi | 0.0299 0.0161 0.0018 0.0003 Pb | 588711 0.0006 41.0558 0.0001 0.0036 0.0015 0.0000 0.0017 0.0002 0.0000 0.0001 99.9827
The second vacuum distillation step 400 yielded two product streams.
On the one hand, we obtained as top product 12 a product stream that mainly contained most of the lead, antimony and silver from the feed, plus a small amount of tin, and on the other hand, as the second bottom product 13, we obtained a product stream that mainly contained tin with only trace amounts of other ingredients.
The flow rates and compositions of these two distillation product streams 12 and 13 are shown in Table 7.
Table 7: Product flows from the second vacuum distillation Weight% | Top current | Soil flow 12 13 Bi | 0.0189 0.0004 0.0000 0.0028 0.0000 0.0019 0.0000 0.0025 Pb | 37.8602 0.0011 13.0000 0.3800 47.7097 99.4584 0.0000 0.0000 0.0560 0.0029 0.3900 0.0178 0.0000 0.0036 0.0000 0.0000 0, 3050 0.0006 0.0001 0.0000 0.0000 0.0000 99.3400 99.8719 The second vacuum distillation stage 400 was run in continuous mode, and was able to continue to function for a period of approximately three (3) years without observing any blockage or plugging of the distillation equipment due to the formation of metal-metal or intermetallic compounds.
The second bottoms 13 from step 400 was further refined in batches in three consecutive steps, which are shown together in the flow chart as tin refining step 500. The first tin refining step consisted of cooling the second bottoms 13 and adding an amount of aluminum nuggets (stream 14). ) to the second bottoms, which had an average temperature of 430 ° C, with stirring, to react with Sb and As and remove those elements to a level that met prevailing international industrial standards.
The amount of Al to be added was based on an analysis of the second bottoms 13, and included an additional amount above the stoichiometric requirement.
After the reaction, the composition was re-analyzed, and if the result was unsatisfactory,
in particular the content of Sb, an additional amount of Al was introduced to trigger a second reaction step.
In total an amount of about 4.3 kg Al per tonne of second bottom product 13 was used on average.
About 30 minutes after the last addition, heating and stirring were stopped and the liquid molten metal composition was allowed to cool.
During cooling, to an average temperature of about 250 ° C, a layer of scratch containing Al / Sb / As was formed, and that scratch was periodically removed from the surface of the molten liquid metal.
The scratch was collected and stored in dry, closed and double-walled steel drums to avoid contact with water or moisture, which could lead to the formation of stibine and / or arsine.
Devates were removed as by-product (stream 17) and recycled to an upstream pyrometallurgical process step,
where they were placed unopened in a liquid bath of molten metal and / or slag, avoiding any risk of contact with moisture.
After the temperature of the tin product was raised again to about 330 ° C, the molten liquid metal was subjected to a second tin refining step, in which solid sodium hydroxide (stream 15) was added as the third base.
In that treatment step, aluminum was bound by the sodium hydroxide, presumably to form Na3AlO3, and formed a separate phase that separated as a supernatant solid scratch from the molten liquid metal and was removed as stream 18. After a period of time every To allow the reaction to take place, a handful of granular sulfur was scattered / spread over the surface of the bath.
The sulfur caught fire and burned any hydrogen that could possibly have evolved from the molten liquid metal as a byproduct of the reaction.
As a result, the content of aluminum in the second bottom product 13 was further reduced.
The amount of sodium hydroxide to be added was adjusted so that the concentration of aluminum in the second bottoms product decreased to less than the detection limit of 1 ppm by weight (Table 8). The scratch formed in this step was also recycled (stream 18) to an upstream pyrometallurgical process step.
In the third and final tin refining step, an amount of elemental sulfur (stream 16) was added to further reduce the copper content of the molten liquid metal and to remove any residual sodium hydroxide from the second tin refining step. The elemental sulfur used was a granulated form of sulfur available from Zaklady Chemiczne Siarkopol in Tarnobrzeg (PL). The sulfur 16 reacted mainly with copper to form copper sulfides and with sodium hydroxide to form Na2SO2, which transitioned to a new supernatant scratch phase. After the addition of sulfur, the stirrer was run for about 10 minutes to oxidize any remaining traces of sulfur and form a new scratch. The scratch was removed from the molten liquid metal as stream 19. The high purity Sn product thus obtained (stream 20, the flow rate and composition of which are indicated in Table 8) contained only 14 ppm Cu and was clumped into lumps. of 22 kg cast, stacked, weighed and tied. The scratch containing sulfur 19 was reprocessed in an upstream pyrometallurgical process step.
Table 8: High purity Sn final product Weight% | High purity Sn Bi | 0.0001 0.0014 0.0004 0.0000 Pb | 0.0008 0.0160 99.9758 0.0000 0.0030 0.0006 0.0001 0.0000 0.0006 0.0000 0.0000 0.0001 99.9989
The overhead product 12 from the second vacuum distillation step 400 was further processed in the third vacuum distillation step 600, performed at an average temperature of 1000 ° C and an average absolute pressure of 0.033 mbar (3.3 Pa). The third vacuum distillation step 600 yielded two product streams.
On the one hand, we obtained as top product 21 a product stream containing mainly lead and antimony, and on the other hand, as the third bottom product 22, we obtained a product stream containing mainly tin and part of the antimony, plus most of the precious metals present in the distillation feed.
The flow rates and compositions of these two distillation product streams 21 and 22 are shown in Table 9. Table 9: Product streams of the third vacuum distillation Weight% | Top current | Soil flow 21 22 Bi | 0.0474 0.0011 0.0000 0.0265 0.0000 0.0004 0.0000 0.0075 Pb | 90.1133 0.7827 9.1014 2.1363 0.5379 96.8647 0.0002 0.0001 0.0100 0.0950 0.4700 0.0730 0.0019 0.0000 0.1860 0.0297 0, 0022 0.0000 0.0013 0.0000 0.0000 0.0000 100.4716 100.0170 The third vacuum distillation step 600 was run in continuous mode, and was able to continue to function for a period of approximately three (3) years without observing any blockage or plugging of the distillation equipment due to the formation of metal-metal or intermetallic compounds.
The third bottoms 22 was recycled to the first crystallizer from upstream step 300, where it was mixed with first bottoms 8 from step 200, to recover the valuable metals contained therein.
The overhead product 21 was further refined in step 800, in batches, in the same equipment used during the soft lead refining step 700 of the first concentrated lead stream as overhead stream 7 from the first vacuum distillation step 200. During the 73 day run, an additional 810 was added. , 2 tons of top product from the third vacuum distillation left over from previous campaigns (stream 29), averaging about 11.1 tons / day, mixed with stream 21 and co-refined. The refining of this hard lead was done in batches in volumes of 100-120 tons total feed. During the 73 days of operation discussed in this example, approximately 9 days were devoted to refining 1159 tons of hard lead, versus approximately 129 tons / day, and the equipment was used for 43 days to refine 4400 tons of the soft lead products as described above average at about 102 tons / day.
The hard lead molten liquid metal feed stream for hard lead refining step 800 was first heated to about 450 ° C with agitation. A sample was taken and analyzed for the presence of As and Sn to determine the amounts of solid sodium hydroxide (stream 30) and solid sodium nitrate (stream 31) that were considered necessary to remove the As and Sn from the molten liquid metal phase, and those amounts were added as the second base and the second oxidant. Over the 73 day operation period considered for this example, a total of 15.2 tons of sodium hydroxide (average 208 kg / day) plus 7.6 tons of sodium nitrate (average 104 kg / day) was added in this refining step for the removing most of the average 26 kg / day As and 32 kg / day Sn that entered step 800 with flows 21 and 29 together. Almost all of the 1502 kg / day of Sb present in the feed streams to hard lead refining step 800 remained in the purified hard lead product 28. This hard lead refining step formed a total fourth supernatant scratch phase containing most of the As and Sn present in the top products 21 and 29 and removed as by-product (stream 32). The fourth supernatant scratch phase was sampled and analyzed for the presence of chlorine using the method according to DIN EN 14582. The analysis showed that approximately 130 ppm by weight of chlorine was present.
The flow rate and composition of the purified running end product stream 28 are indicated in Table 10. Table 10: Composition of the end running hard product Weight% | Hard lead 28 Bi | 0.0550 0.0000 0.0000 0.0000 Pb | 914680 8.9900 0.0192 0.0001 0.0112 0.0025 0.0002 0.0005 0.0005 0.0000 0.0000 100.5472
Thus, this hard lead refining step in step 800 only aimed to remove a total of an average of 58 kg / day of impurities, which is significantly less than the removal intended by step 700.
In addition, the concentrations of As and Sn in the feed to step 800 were also higher than those in the feed to step 700. Step 800 therefore achieves its goals much more easily than step 700. Relative to the total amount (As + Sn + Sb) entering the respective lead refining steps 700 and 800, step 800 consumes significantly less chemicals and also produces significantly less supernatant scratch than step 700, which also has the advantage of putting a less heavy burden on recirculating the supernatant scratch in the upstream pyrometallurgical process.
It was also observed that in step 800 As and Sn could be successfully removed to very low levels, while hardly any Sb needed to be removed.
Having now fully described the present invention, it will be apparent to those skilled in the art that the invention can be practiced with a wide range of parameters within the scope of the claims, without departing from the scope of the invention as defined by the claims.

权利要求:
Claims (61)
[1]
A method of separating, by fractional crystallization (300), a molten crude tin mixture (8) containing lead and silver into a first silver-enriched liquid tap product (9) at the liquid end of the crystallization step and a first tin-enriched product (10) at the crystal end of the crystallization step, wherein the first silver-enriched liquid tapping product (9) comprises, on a dry weight basis: ° at least 6.0% by weight and not more than 30.0% by weight of lead, ° at not less than 70.0% by weight and not more than 91% by weight of tin, ° at least 95.0% by weight and not more than 99.0% by weight of lead and tin together, ° at least 0.75% by weight and at least at most 5.00 wt.% silver, and ° at least 0.24 wt.% antimony.
[2]
The method of claim 1 wherein the crude tin mixture (8) comprises at least 0.1% by weight and at most 7.0% by weight lead.
[3]
The method of claim 1 or 2 wherein the crude tin mixture (8) comprises at most 6.5% by weight Pb.
[4]
The method of any of the preceding claims, wherein the concentration of lead in the crude tin mixture (8) is at least 3.0 times the concentration of silver in the crude tin mixture (8).
[5]
The method of any one of the preceding claims, wherein the crude tin mixture (8) comprises at least 10 ppm by weight of silver (Ag) and optionally at most 0.85% by weight silver.
[6]
The method according to any of the preceding claims, wherein the crude tin mixture (8) comprises at least 0.1% by weight of antimony (Sb).
[7]
The method of any one of the preceding claims, wherein the first tin-enriched product (10) comprises at least 0.05 wt% lead.
[8]
The method of any one of the preceding claims, wherein the first tin-enriched product (10) is produced in a continuous mode.
[9]
The method of any one of the preceding claims, wherein the full fractional crystallization step (300) is performed in a continuous mode.
[10]
The method of any one of the preceding claims, wherein the first silver-enriched liquid bleed product (9) is partially and / or temporarily recycled to the feed of the fractional crystallization step (300).
[11]
The method of any one of the preceding claims, wherein the fractional crystallization step (300) includes at least 4 crystallizer steps.
[12]
The method of any preceding claim wherein the crystallizer used in the fractional crystallization step (300) comprises a feed stage for receiving the feed to the crystallizer and wherein the crystallizer further comprises at least one crystallizer stage, and preferably at least 2 stages, between the feed stage and each of the product outlets of the crystallizer.
[13]
The method of any one of the preceding claims wherein the temperature profile through the steps of the fractional crystallization step (300) is in the range of 180-270 ° C.
[14]
The method of any one of the preceding claims, wherein the temperature difference between two adjacent steps in the fractional crystallization step (300), none of which is a feed step or a final step, is at most 20 ° C.
[15]
The method of any one of the preceding claims wherein the fractional crystallization step (300) is performed in at least 2 crystallizers in series, the product being fed from the crystal end of the upstream crystallizer to the downstream crystallizer, either completely to the feed stage of the downstream crystallizer, either only a first portion thereof is fed to the feed stage of the downstream crystallizer and a second portion thereof is fed to a second stage of the downstream crystallizer which is a different stage from the feed stage, where that second stage is selected from the stages located between the feed stage and the final stage at the crystal end of the downstream crystallizer, the second stage preferably being separated from the supply stage by at least one and preferably two or three intermediate stages.
[16]
The method of the preceding claim wherein the product from the liquid end of the downstream crystallizer is at least partially, and preferably completely, at least temporarily recycled to the upstream crystallizer optionally to the feed stage but preferably to a second stage selected from the stages located between the feed stage and the final stage at the crystal end of the upstream crystallizer, the second stage being preferably separated from the final stage by at least one, and preferably two or three intermediate stages.
[17]
The method of any one of the preceding claims wherein the crude tin mixture (8) further comprises at least 1 ppm by weight of at least one metal selected from copper, iron, bismuth, nickel, zinc, gold, indium and arsenic.
[18]
The method of any one of the preceding claims, wherein the raw tin mixture (8) comprises at least 99.0% by weight together of tin, lead, antimony and silver.
[19]
The method of any one of the preceding claims wherein the crude tin mixture (8) is at least partially obtained as the first bottoms product from a first distillation step (200) in which lead (Pb) is removed from a molten solder mixture (6) by evaporation to obtain as top product a first concentrated lead stream (7).
[20]
The method of the preceding claim wherein at least one product (9) from the liquid end of at least one crystallizer in the fractional crystallization step (300) is at least partially recycled to the feed of the first distillation step
(200).
[21]
The method of any of claims 19-20, wherein the first bottoms (8) of the first distillation step (200) comprises at least 0.1 wt% lead.
[22]
The method of any one of the preceding claims, wherein the first silver-enriched liquid draw-off product (9) is subjected to a fourth distillation step in which lead is removed by evaporation to a fourth concentrated lead stream as distillation overhead, producing a fourth distillation bottoms product .
[23]
The method of the preceding claim, wherein the fourth distillation bottoms product is subjected to a fractional crystallization step yielding a second silver enriched bleed product at the liquid end and a second tin enriched product at the crystal end.
[24]
The method of any one of the preceding claims, wherein the first silver-enriched liquid tap product (9) or the second silver-enriched liquid tap product is used as feedstock to be cast into at least one anode that is subjected to a electro-refining step to obtain a cathode product rich in lead plus tin, and an anode glue rich in silver, the anode glue preferably adhering to the used anode and removed therefrom by mechanical means.
[25]
The method of the preceding claim, wherein the at least one anode comprises at least 0.5% by weight of antimony.
[26]
The method of any one of claims 19-25, wherein the molten solder mixture (6) is obtained by pretreating (100) a crude solder composition (1) containing at least 90% by weight of tin and lead together.
[27]
The method of the preceding claim, wherein the crude solder composition (1) contains at least 0.16% by weight and optionally at most 10% by weight of the total of chromium (Cr), manganese (Mn), vanadium (V), titanium (Ti), tungsten (W), copper (Cu), nickel (Ni), iron (Fe), aluminum (Al) and / or zinc (Zn), and wherein the pretreatment (100) comprises the step of cooling of the crude solder composition (1) to a temperature of not more than 825 ° C to produce a bath containing a first supernatant scratch (4) that floats by gravity on a first liquid molten metal phase.
[28]
The method according to the preceding claim further comprising the step of adding a compound (2) selected from an alkali metal and / or an alkaline earth metal, or a chemical compound comprising an alkali metal and / or an alkaline earth metal, to the first liquid molten metal phase to form a bath containing a second supernatant scratch (5) which floats by gravity on a second liquid molten metal phase, and removing the second supernatant scratch (5) from the second liquid molten metal phase to remove the molten solder mixture (6).
[29]
The method of any of claims 27-28 further comprising the step of removing the first supernatant scratch (4) from the first liquid molten metal phase.
[30]
The method of any one of claims 26-29 wherein at least one product (9) from the liquid end of at least one crystallizer in the fractional crystallization step (300) is at least partially recycled to the feed of the pretreatment step of crude solder (100).
[31]
The method according to any of claims 26-30, wherein the method for obtaining the crude solder composition (1) comprises a metal melting step and wherein at least one of the first supernatant scratch (4) and / or the second supernatant scratch (5) is recycled to the melting step.
[32]
The method of any one of claims 19-31 wherein the molten solder mix (6) fed to the first distillation step (200) comprises, on a dry weight basis:
° more lead than tin, ° no more than 0.1% of the total of chromium (Cr), manganese (Mn), vanadium (V), titanium (Ti) and tungsten (W), ° no more than 0.1% aluminum (AI) ° not more than 0.1% nickel (Ni) ° not more than 0.1% iron (Fe), and ° not more than 0.1% zinc (Zn).
[33]
The method of any of claims 19-32, wherein the molten solder mix (6) fed to the first distillation step (200) comprises, on a dry weight basis, at least 1 ppm by weight and at most 5000 ppm by weight to copper.
[34]
The method of any of claims 19-33, wherein the fourth concentrated lead stream is combined with the first concentrated lead stream (7) to obtain a fifth concentrated lead stream.
[35]
The method of any of claims 19-34 further comprising the step of removing at least one contaminant selected from the metals arsenic, tin and antimony from a concentrated lead stream selected from the first concentrated lead stream (7), the fourth concentrated lead stream and the fifth concentrated lead stream to obtain a purified soft lead product (27).
[36]
The method of the preceding claim wherein the at least one contaminant is removed by treating the concentrated lead stream at a temperature of less than 600 ° C with a first base (24) and a first oxidant (25) resulting in the formation of a third supernatant scratch (26) containing a metalate compound of the respective contaminant metal, followed by separating the scratch (26) from the purified soft lead stream (27).
[37]
The method of the preceding claim wherein the third supernatant scratch (26) is at most
1.0 wt% chlorine, and preferably up to 1.0 wt% total halogens.
[38]
The method of any of claims 36-37, wherein the third supernatant scratch (26) is recycled to a process step upstream of the first vacuum distillation step (200).
[39]
The method of any one of the preceding claims, wherein the first tin-enriched product (10) is subjected to a second distillation step (400) that mainly separates lead and antimony from the first tin-enriched product (10) by evaporation. producing a second concentrated lead stream (12) as the top product and producing a second bottom product (13).
[40]
The method of the preceding claim, wherein a fresh feed containing lead (11) is added to the feed of the second distillation step (400).
[41]
The method of any of claims 39-40 wherein the second concentrated lead stream (12) is subjected to a third distillation step (600) that separates predominantly lead and antimony from the second concentrated lead stream (12) by evaporation, wherein as a top product a third concentrated lead stream (21) is produced and a third bottoms product (22) is produced.
[42]
The method of the preceding claim wherein a fresh feed containing lead (34) is added to the feed of the third distillation step (600).
[43]
The method of any of claims 41-42 wherein the third bottoms product (22) is at least partially and preferably completely recycled to the feed of the second distillation step (400) and / or to the feed of the fractional crystallization step (300).
[44]
The method of any one of claims 41-43 further comprising the step (800) of removing at least one contaminant selected from the metals arsenic and tin from the third concentrated lead stream (21), resulting in a purified hard lead stream is produced as a hard lead product (28).
[45]
The method of the preceding claim wherein the at least one impurity is removed by treating the third concentrated lead stream (21) at a temperature of less than 600 ° C with a second base (30) and a second oxidant (31) , resulting in the formation of a fourth supernatant scratch (32) containing a metalate compound of the affected contaminant metal, followed by separating the fourth supernatant scratch (32) from the purified hard lead stream (28).
[46]
The method of the preceding claim, wherein the fourth supernatant scratch (32) comprises at most 1.0% by weight of chlorine, and preferably at most 1.0% by weight of total halogens.
[47]
The method of any of claims 45-46, wherein the fourth supernatant scratch (32) is recycled to a process step upstream of the first vacuum distillation step (200).
[48]
The method of any of claims 41-47, wherein the third concentrated lead stream (21) comprises at least 0.50 wt.% And at most 15.0 wt.% Antimony.
[49]
The method of any of claims 39-48 wherein the second bottoms product (13) is further refined to obtain a high purity high quality tin product (20).
[50]
The method of the preceding claim wherein the second bottoms (13) is treated with aluminum metal (14), preferably in stoichiometric excess to the amount of antimony present, preferably in combination with mixing and cooling the reacting mixture to less than 400 ° C, followed by separating the scratch containing Al / Sb / As (17) formed by the treatment.
[51]
51. The method according to the preceding claim wherein the second bottom product (13), after the treatment with aluminum and preferably also after the removal of the scratch containing Al / Sb / As (17), is treated with a third base (15 ), which is preferably selected from NaOH, Ca (OH) 3 and NasCO3 and combinations thereof, more preferably NaOH, followed by separating the scratch containing base (18) formed by the treatment.
[52]
The method of the preceding claim, wherein the second bottoms (13), after the treatment with the third base (15), is treated with sulfur (16), followed by separating the scratch containing S (19) that is formed by the treatment.
[53]
The method of any of the preceding claims, wherein at least part of the method is electronically monitored and / or controlled.
[54]
54. Metal composition (9) comprising, on a dry weight basis: ° not less than 6.0% by weight and not more than 30.0% by weight of lead, ° at least 70.0% by weight and not more than 91% by weight % tin, ° at least 95.0% by weight and not more than 99.0% by weight of lead and tin together, ° at least 0.75% by weight and not more than 5.00% by weight of silver, and ° at least 0.24 wt% antimony.
[55]
The metal composition (9) of claim 54 which is a molten liquid.
[56]
56. The metal composition (9) of claim 54 or 55 further comprising at least 0.05 weight% arsenic.
[57]
The metal composition (9) according to any one of claims 54-56, further comprising at least 0.05% by weight of copper.
[58]
The metal composition (9) according to any of claims 54-57, further comprising at least 0.0030 weight% nickel.
[59]
The metal composition (9) according to any of claims 54-58, further comprising at most 0.40% by weight of bismuth.
[60]
The metal composition (9) according to any of claims 54-59 further comprising at most 1.0 wt% iron.
[61]
The metal composition (9) of any of claims 54-60 further comprising at least 0.0005% by weight of gold.

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同族专利:

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TW202035716A|2020-10-01|

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BE1027001A1|2020-08-21|

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US20220074020A1|2022-03-10|

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WO2020157167A2|2020-08-06|

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EP3935198A2|2022-01-12|

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CN113316654A|2021-08-27|

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PE20212094A1|2021-11-04|

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WO2020157167A3|2020-09-10|

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SG11202107713XA|2021-08-30|

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CA3126626A1|2020-08-06|

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法律状态:
2020-10-12| FG| Patent granted|Effective date: 20200824 |

优先权:

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申请号 | 申请日 | 专利标题

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EP19154610|2019-01-30|

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