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    • 专利摘要:
    A method of attacking sulfuric acid from a phosphate source comprising calcium or not calcium for a predetermined period of time between 20 and 180 minutes under conditions according to which the sulfate molar ratio originating from sulfuric acid as well as 'optionally the calcium phosphate source present in the phosphate source is between 0.6 and 0.8, and the P2O5 content in the attack tank is less than 6%.
    公开号:BE1025894B1
    申请号:E20185563
    申请日:2018-08-10
    公开日:2020-02-21
    发明作者:Alexandre Wavreille；Livio Lederer；Léon Ninane
    申请人:Prayon Tech；
    IPC主号:
    专利说明:

    "PROCESS OF ACID ATTACK OF A PHOSPHATE SOURCE"
    The present invention relates
    - a method of acid attack on a phosphate source comprising calcium and
    - a method of acid attack on a phosphate source comprising no calcium for the production of a purified phosphate-based compound.
    By phosphate source not comprising calcium is understood a calcium content linked or not to the phosphate ion, hydrogen phosphate and / or dihydrogen phosphate of less than 10% by weight, preferably less than 5% by weight, preferably 1% by weight, more preferably 0.1%, and even more preferably 0.05% by weight or less relative to the total weight of the dry matter of the phosphate source (dry 105 ° C).
    Sources of phosphates not containing bound calcium can be, for example, iron, aluminum phosphate, lithium phosphate, zinc phosphate, magnesium, or mixed phosphates. In this embodiment, calcium is added to the phosphate source to obtain a SO 4 / Ca molar ratio of between 0.6 and 0.8 in the attack tank.
    Acid attacks from a phosphate source comprising calcium are well known in the art.
    A conventional process of this type consists in reacting the phosphate rock with sulfuric acid under conditions giving rise to a crystallization of calcium sulfate dihydrate or gypsum (CaSO 4 .2H 2 O). The gypsum slurry obtained in a first reactor can then be subjected, in a second reactor, to a maturation allowing a magnification of the sulphate grains formed, and this to increase the
    2018/5563
    BE2018 / 5563 filterability. The matured slurry is then filtered to obtain a phosphoric acid having a free P 2 O 5 content of the order of 25 to 35% by weight.
    Also known are processes for producing phosphoric acid by attack with sulfuric acid giving, at higher temperatures and concentrations of P 2 O 5 and / or SO 3 , a slurry of calcium sulphate in the form of hemihydrate ( CaSO 4. % H 2 O) or anhydrite. These methods generally give a concentrated phosphoric acid and a well filterable sulfate, but the P 2 O 5 extraction yield of these methods is lower than the conventional method. In certain cases, there is also, after this attack, a conversion of the calcium sulfate hemihydrate obtained into calcium sulfate dihydrate (Ullman's Encyclopedia of Industrial Chemistry, 2008, pages 8 and 9).
    A method is then known in which the phosphate rock is again subjected to the attack conditions of the conventional method so as to obtain a first slurry in which the gypsum formed has a grain size allowing good filtration. Part of this first slurry is then removed and subjected to conditions under which the gypsum is converted into hemihydrate, thereby forming a second slurry. The rest of the first slurry is then mixed with the second and the whole is filtered (see WO 2005/118470).
    A major problem in the production of phosphoric acid lies in the depletion of P 2 O 5- rich phosphate ore deposits. These deposits have been exploited. It is now necessary to turn to ores whose P2O5 concentration is considered to be poor, for example P2O5 contents of 25% by weight or less relative to the phosphate rock, and in certain cases 20% or less.
    A process for exploiting such ores and extracting a high quality phosphoric acid from production has been described in international patent application WO2011 / 067321. Conditions
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    BE2018 / 5563 of attack of this process provide for a substantially stoichiometric reaction between the sulfuric acid introduced and the calcium contained in the phosphate rock, while the content of free P 2 O 5 in the crystallization slurry is kept high between 38 and 50% by weight and the temperature between 70 and 90 ° C. Surprisingly, these conditions give rise to very fine crystals of stable dihydrate. This slurry is then subjected to an increase in temperature during which the grains of dihydrate dissolve and release the unattacked or co-crystallized P 2 O 5 , while crystallization of calcium sulfate hemihydrate is well filterable and a phosphoric acid produced. very low in free SO 3 . It should be noted that these ores poor in P 2 O 5 frequently also present increasingly higher content of impurities. The content of impurities is commonly expressed by the ratio (Al 2 O 3 + Fe 2 O 3 + MgO) / P 2 O 5 X 100, also noted MER (Minor Element Ratio). The so-called conventional phosphates are characterized by a MER ratio of approximately 5 to 8.
    Beyond 10, the content of impurities is so important that it begins to negatively influence the crystallization of calcium sulphate in the form of gypsum during the attack of the ore by sulfuric acid. At these impurity contents, the production of phosphoric acid becomes problematic, in particular because of the difficulties of crystallization of calcium sulphate dihydrate and of filtration thereof. This therefore has a major drawback in all the processes where filtration takes place directly after the attack on the phosphate rock.
    In a process as described in patent application WO2011 / 067321, crystallization in gypsum is also affected by impurities, but since this gypsum is not intended to be filtered, this is not of consequence.
    Document WO2012 / 163425 aims to develop a process for the production of phosphoric acid by attacking poor quality phosphate rock using sulfuric acid which
    2018/5563
    BE2018 / 5563 makes it possible to obtain a quality phosphoric acid for production and a good yield of extraction of P 2 O 5 from rock. This process must also be able to be easily applied in an existing conventional installation and therefore not require costly and economically untenable conversions. According to this document, the method comprises, during the attack, adding a source of fluorine to the first slurry in a content of 1% to 5% by weight of F relative to the P 2 O 5 contained in the phosphate rock . The attack conditions are such that they provide for a substantially stoichiometric reaction between the sulfuric acid introduced and the calcium contained in the phosphate rock, mainly in the form of carbonate and calcium phosphate. The acidic aqueous phase of this first slurry resulting from the attack contains little or no free sulfuric acid and its free Ρ 2 Ο 5 content is quite high.
    As can be seen, the difficulty in producing phosphoric acid from phosphate rock is always to have a sufficient attack yield, an acceptable quality of acid as well as a more or less easily recoverable calcium sulphate. and in this context, it is generally accepted that the attack of phosphate rock by concentrated sulfuric acid must be carried out at stoichiometry in order to produce a crude phosphoric acid and to ensure a rate of extraction of P 2 O 5 sufficient and economically profitable.
    In the case of the production of phosphoric acid carried out by an attack on rocks phosphated by sulfuric acid at stoichiometry, the reaction is written:
    (I) Ca 3 (PO4) 2 + 3 H2SO4 + 3 CaSO4.2H2O + 2 H3PO4
    In which the SO 4 / Ca molar ratio = 3/3, ie = 1
    It is also known from this phosphoric acid thus produced to add a calcium base to produce a food grade bicalcium phosphate (DCP) (for humans or animals) or for any other application.
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    BE2018 / 5563
    Thus, from document GB-938468, the production of monocalcium phosphate (MCP) or bicalcium phosphate (DCP) is known from phosphate rocks or from natural ore with hydrochloric acid.
    Document WO 2015/082468 also describes an attack with hydrochloric acid of phosphate rocks.
    Unfortunately, these hydrochloric acid attack methods require the presence of a DCP washing step to remove the chloride ions which cannot, for example, be found in certain grades of technical DCP. The hydrochloric acid processes generate residual calcium chloride in which part of the impurities in the raw material will accumulate. This solution requires additional purification treatments in order to be used. In addition, the presence of hydrochloric acid in the attack tank causes corrosion problems in the installations as soon as the temperature is greater than or equal to 60 ° C.
    There is also known a method of attacking phosphate rocks using sulfuric acid from document US3161466. In the process described in this document, a first sulfuric attack is carried out in an attack tank to obtain a pasty slurry, which can be left for maturation or else be transferred to a second tank or it will undergo an additional attack to the 'acid. This process is based on a sequential pH control, the incremental pH increases being used to selectively precipitate the various impurities present in the liquid phase (liquor). The liquor contains MCP and phosphoric acid in high quantities.
    Unfortunately, this described method is restrictive in that it requires rigorous pH controls at each stage given the selective precipitation taught, but also uneconomical in view of the numerous stages involved and therefore of the time required to treat the phosphate rock.
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    BE2018 / 5563
    Finally, another method is described in document GB793801.
    In this document, the method described comprises an attack with concentrated sulfuric acid of 14 to 62% of phosphate rocks in a substoichiometric manner. The aim of the process described is the recovery of the rare earths included in the phosphate rock. Therefore, one of the critical steps is the complete dissolution of the phosphate rock to form a liquid phase from which the contained rare earths will be extracted. The process therefore includes adding reactive silica to maintain the rare earths in solution and requires an attack time of approximately 24 hours. The P 2 O 5 contents relative to the calcium (P 2 O 5 / Ca) disclosed range from 10/1 to 4/1.
    As can be seen, this process is time consuming and involves a considerable cost of treating the phosphate rock, due to the fact that the process is probably made profitable by the extraction of rare earths which have a high market value. However, in an approach aimed at producing a material based on purified phosphate, the economic profitability of this process is to be questioned.
    The invention aims to overcome the drawbacks of the state of the art by providing an economically profitable process around an optimum between the energy cost, production cost, resistance of the materials used in the production devices and the flexibility of the raw materials.
    In fact, one of the objects of the present invention is to provide a process making it possible to treat rocks concentrated in phosphatic material as much as rocks little concentrated in phosphatic material and secondary sources of phosphate.
    To solve this problem, there is provided according to the invention a method of acid attack on a phosphate source comprising calcium for the production of a purified phosphate-based compound as indicated at the beginning comprising the steps of
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    BE2018 / 5563
    a) an acid attack using sulfuric acid from said phosphate source, for a predetermined period of time between 20 and 180 minutes with the formation of a first suspension containing a first solid material and a first liquid phase in which the first solid material is in suspension, said first solid material comprising at least calcium sulphate and impurities, said first liquid phase comprising phosphoric acid and dissolved monocalcium phosphate, said attack being carried out under conditions at entry according to which the sulphate molar ratio originating from sulfuric acid as well as possibly from the calcium phosphate source is between 0.6 and 0.8, and the P 2 O 5 content is less than 6%,
    b) a first filtration of said first boil with separation of said first solid material from said first liquid phase,
    c) recovery from said first liquid phase of a purified phosphate-based compound.
    Advantageously, said P 2 O 5 content is a P 2 O 5 content dissolved in said first liquid phase.
    The SO 4 / Ca molar ratio defines the amount of acid necessary to attack the phosphate source containing Ca at the inlet of the reagents.
    Advantageously, said acid attack takes place in 1, 2 or more attack tanks. As can be seen, the method according to the present invention is an attack method under strongly sub-stoichiometric conditions, the sulphate molar ratio coming from sulfuric acid as well as possibly from the calcium phosphate source (SO 4 / Ca) present in the phosphate source being between 0.6 and 0.8
    2018/5563
    BE2018 / 5563 has multiple advantages. First, the consumption of sulfuric acid is reduced and a multitude of phosphate sources can be treated by the process according to the present invention in order to produce different purified phosphate-based compounds. In fact, the method according to the present invention makes it possible to obtain a liquid phase containing phosphoric acid and monocalcium phosphate from which bicalcium phosphate can also be obtained, thereby offering great flexibility. Indeed, this dicalcium phosphate can be attacked to produce a relatively pure phosphoric acid as well as its derivatives. In addition, the attack time is relatively short, decreasing in this way by the joint action of flexibility regarding the source of phosphate and the multiplicity of products obtained, production costs. Maintenance costs can also be reduced thanks to the low aggressiveness of the reaction medium.
    To reach the sulfate molar ratio from sulfuric acid as well as possibly from the phosphate to calcium source, the calcium content is mainly based on the calcium content present in the phosphate source, but it is however possible to add more if necessary.
    Advantageously, the method according to the invention comprising the steps of:
    - an acid attack in 1, 2, or more attack tanks using sulfuric acid from said phosphate source for a predetermined period of time between 20 and 180 minutes with the formation of a first suspension containing a first solid material and a first liquid phase in which the first solid material is in suspension, said first solid material comprising at least calcium sulphate and impurities, said first liquid phase comprising phosphoric acid and dissolved monocalcium phosphate, said attack being performed under entry conditions whereby the molar ratio
    2018/5563
    BE2018 / 5563 sulfate from sulfuric acid and possibly from the calcium phosphate source present in the phosphate source is between 0.6 and 0.8 and the P 2 O 5 content in the tank (s) attack is less than 6%,
    a first filtration of said first boil with separation of said first solid material from said first liquid phase, and
    - Recovery from said first liquid phase of a purified phosphate-based compound.
    The SO 4 / Ca molar ratio defines the amount of acid required to attack the phosphate source containing Ca at the entry of the reagents into the attack tank (s).
    Advantageously, the method according to the invention comprising the steps of:
    - an acid attack in 1, 2, or more attack tanks using sulfuric acid from said phosphate source for a predetermined period of time between 20 and 180 minutes with the formation of a first suspension containing a first solid material and a first liquid phase in which the first solid material is in suspension, said first solid material comprising at least calcium sulphate and impurities, said first liquid phase comprising phosphoric acid and dissolved monocalcium phosphate, said attack being carried out under entry conditions according to which the sulphate molar ratio originating from sulfuric acid as well as possibly from the calcium phosphate source is between 0.6 and 0.8 and the P 2 O 5 content in the attack tank (s) is less than 6%,
    a first filtration of said first boil with separation of said first solid material from said first liquid phase, and
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    BE2018 / 5563
    - Recovery from said first liquid phase of a purified phosphate-based compound.
    The SO 4 / Ca molar ratio defines the amount of acid required to attack the phosphate source containing Ca at the entry of the reagents into the attack tank (s).
    Advantageously, said step a) of acid attack comprises:
    - an acid attack in an attack tank, or
    - an acid attack in a first attack tank with addition of sulfuric acid and transfer of said first suspension formed or being formed in the first attack tank to a second attack tank without addition of acid sulfuric, or
    - an acid attack in two successive attack tanks with the addition of sulfuric acid in the 2 tanks, or
    - an acid attack in three attack tanks, or
    - an acid attack in a first attack tank with addition of sulfuric acid and transfer of said first suspension formed or being formed in the first tank to a second and a third attack tank without addition of acid sulfuric, or
    an acid attack in a first attack tank and a second attack tank with or without addition of sulfuric acid and transfer of said first suspension formed or being formed in the first attack tank and in the second attack tank to a third attack tank without adding sulfuric acid.
    In a particular embodiment, the method according to the invention comprising the steps of:
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    BE2018 / 5563
    - an acid attack in an attack tank using sulfuric acid from said phosphate source for a predetermined period of time between 20 and 180 minutes with the formation of a first suspension containing a first solid material and a first liquid phase in which the first solid material is in suspension, said first solid material comprising at least calcium sulphate and impurities, said first liquid phase comprising phosphoric acid and dissolved monocalcium phosphate, said attack being carried out under conditions at the entry according to which the sulphate molar ratio coming from sulfuric acid as well as possibly from the source of phosphate to calcium present in the source of phosphate is between 0.6 and 0.8 and the P 2 O content 5 in the attack tank is less than 6%,
    a first filtration of said first boil with separation of said first solid material from said first liquid phase, and
    - Recovery from said first liquid phase of a purified phosphate-based compound.
    The SO 4 / Ca molar ratio defines the amount of acid required to attack the source of phosphate containing Ca at the entry of the reagents into the attack tank.
    In one embodiment the source of phosphate does not include calcium. By phosphate source not comprising calcium is understood a calcium content of 10% by weight or less, preferably 5% by weight or less, preferably 1% by weight or less, more preferably 0.1% or less , and even more preferably less than 0.05% relative to the total weight of the dry matter of the phosphate source (dry 105 ° C.).
    Sources of phosphates not containing calcium can be of mineral or organic origins such as for example the ashes of anaerobic digestates of organic waste, such as for example
    2018/5563
    BE2018 / 5563 slurry, sludge from wastewater treatment plants, compost, manure, residues from the metallurgical, chemical industry including phosphate chemistry, food industry, sludge from wastewater treatment plants, guano, slurry, manure, green waste. They can also be in the form of iron phosphate, aluminum, lead, zinc, magnesium. In this embodiment, calcium is added to the phosphate source in an amount to obtain a SO 4 / Ca molar ratio of between 0.6 and 0.8.
    It has indeed appeared surprisingly that the combination of strongly sub-stoichiometric conditions (low quantity of sulfuric acid available to attack the phosphate source) with a short attack time allows the production of purified phosphate-based compound easily. recoverable and economically profitable, all while the P 2 O 5 concentration in the attack tank (s) is low but nevertheless of sufficient purity to enter into various subsequent productions, in particular, without however being limited thereto, in the production of FAD on an industrial scale and food grade. Consequently, in the process according to the present invention, the extraction of P 2 O 5 from numerous sources of phosphate is at the optimum, whether the sources of phosphate are concentrated in phosphate or not. This means that once this process is implemented on a production site, the industrialist can then use conventional rocks concentrated in calcium phosphate, but also rocks less concentrated in calcium phosphate or any secondary product containing phosphate. calcium.
    By the use of sulphate molar ratio coming from sulfuric acid as well as possibly from the source of phosphate to calcium present in the phosphate source of between 0.6 and 0.8, the ratio of solid matter to phase liquid is low i.e. the density of suspension is low. The sulphate present in the attack tank (s) comes mainly from the rock but it can also come from the phosphate source as well as possibly from the dilution water. Indeed, the
    2018/5563
    BE2018 / 5563 solid content in the attack tank (s) is typically less than 16%, preferably between 4% and 15%, thus providing a suspension instead of a slurry and the presence of a low solid content , typically counterintuitive in a phosphate source treatment process in which the attack time is short, the sulfuric acid is diluted and in which a filtration step is necessary.
    In the process according to the present invention, the reaction is sub-stoichiometric, depending on the reaction
    Ca 3 (PO 4 ) 2 + 2 H 2 SO 4 + H 2 O + 2 CaSO 4 .2H 2 O + Ca (H 2 PO 4 ) 2 with a theoretical SO 4 / Ca molar ratio around 0.66.
    By implementing a sulphate molar ratio coming from sulfuric acid as well as possibly from the calcium phosphate source present in the phosphate source between 0.6 and 0.8 as close as possible to the theoretical ratio SO 4 / Ca, the attack conditions make it possible to remain mainly under the precipitation curve of calcium with the phosphate ion and therefore to produce MCP soluble in the acidic liquid phase, where the extraction yield of P 2 O 5 has been measured at over 90%.
    In a particular embodiment, the sulphate molar ratio originating from sulfuric acid as well as possibly from the calcium phosphate source of between 0.6 and 0.8 can be obtained by adding calcium to the system if the source of phosphate does not contain calcium.
    By the terms "acid attack using a mineral acid, preferably sulfuric acid from a phosphate source for a predetermined period of time" is meant that the predetermined period of time is the average residence time in one or more attack tanks, whether during a batch or continuous attack, possibly with a recycling phase, as indicated below.
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    BE2018 / 5563
    In the process according to the present invention, the first solid material comprises unattacked calcium phosphate as well as calcium sulfate (calcium sulfate hemihydrate, anhydrite, or gypsum) and impurities. Calcium sulphate being mainly present in the form of gypsum (calcium sulphate di-hydrate)
    By the terms "monocalcium phosphate" is meant a compound of formula Ca (H 2 PO 4 ) 2 (MCP) comprising several English names such as monocalcium phosphate, monobasic calcium phosphate, calcium biphosphate, calcium acid phosphate, acid calcium phosphate, mono basic calcium phosphate, calcium dihydrogen phosphate.
    Advantageously, the predetermined period of time is less than 120 minutes, preferably less than 90 minutes, more preferably less than 60 minutes, in particular less than 45 minutes and more particularly approximately equal to 30 minutes.
    As can be seen, the predetermined period of time during which the acid attack occurs can be greatly reduced to reach attack times as short as 60 minutes, in particular 45 minutes, or even 30 minutes.
    In a particular embodiment, the P 2 O 5 content in the attack tank (s) is less than 5%, preferably between 0.5 and 4% P 2 O 5 Preferably between 1.5 and 3%.
    In fact, in the process according to the present invention, the P 2 O 5 content is low in the attack medium, but the latter is ultimately sufficiently pure, against all expectations so that it can then be used as compounds. purified based on phosphate.
    In another preferred embodiment of the method according to the present invention, said attack is carried out at ambient temperature.
    In a preferred variant of the process according to the present invention, said attack is carried out at a temperature in the tank (s)
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    BE2018 / 5563 of attack less than or equal to 90 ° C, preferably less than or equal to 80 ° C, preferably less than or equal to 75 ° C, more preferably less than or equal to 60 ° C, preferably greater at 40 ° C.
    Indeed, according to the present invention, it has been identified that it is possible to treat the rock by an acid attack at a generally low temperature, certainly between 40 and 60 ° C., which avoids any heat input and still allows lower production costs from an energy cost perspective, while using dilute sulfuric acid, also reducing SO 3 residues in the purified phosphate compound
    Advantageously, the sulfuric acid is a dilute sulfuric acid, in particular before addition in the attack tank or tanks, which reduces the costs of treatment of phosphate sources and this as much for sources concentrated in phosphate or not while reducing the SO 3 content in the liquid phase.
    Advantageously, in the process according to the present invention, said dilute sulfuric acid has an H 2 SO 4 concentration of less than 14% by weight, preferably less than or equal to 13%, preferably less than or equal to 10% by weight , more particularly between 0.5 and 9% by weight, preferably between 3 and 7% and more preferably around 5% by weight, relative to the total weight of the dilute sulfuric acid.
    In a variant, the sulfuric acid is a concentrated sulfuric acid, in particular it will be diluted in the attack tank or tanks, the dilution water being either, drinking water, river water , sea water, recycling water or water from FAD production.
    As mentioned previously, the sulphate molar ratio originating from sulfuric acid as well as possibly from the phosphate to calcium source present in the phosphate source is between 0.6 and 0.8, which is sufficiently low to approach l 'optimum of
    2018/5563
    BE2018 / 5563 theoretical report and maintain the MCP and phosphoric acid in the liquid phase. The challenge is to have the solubility of calcium sulfate without precipitating calcium phosphate. Consequently, when advantageously, the sulfuric acid is diluted and has an H 2 SO 4 concentration of less than 14%, preferably less than or equal to 10%, or even between 0.5 and 9% by weight, by compared to the total weight of dilute sulfuric acid, the optimum is reached, together with the short predetermined duration of the acid attack, by reducing the risk of precipitating calcium with the phosphate ions in solution and thus promoting the formation of MCP and phosphoric acid in the attack tank (s) in the liquid phase and not in precipitated form because the reaction medium in the attack tank (s) is sufficiently diluted to avoid precipitation of calcium phosphate salts. Only calcium sulphate, preferably gypsum, precipitates in amounts less than conventional methods of attacking phosphate sources. Therefore, in the process according to the present invention, it is possible to use a low value recovered or recycled acid.
    In the process according to the present invention, the sulfuric acid may be a dilute sulfuric acid recycled from existing streams from the phosphate industry, metallurgy, chemistry, etc. The liquid phase recovered for example after the production of DCP by precipitation can be recycled to dilute the attacking sulfuric acid solution. Preferably, the attacking sulfuric acid is stored in a storage tank. The attacking sulfuric acid can therefore come from recycling of other stages or can be obtained by dilution of concentrated acid, such as for example concentrated sulfuric acid at 98% or less, which can be diluted with water. or with the liquid phase recovered for example after the production of DCP by precipitation (second liquid phase). Preferably, the dilution of sulfuric acid will be carried out online during the supply of the attack tank (s).
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    More particularly, in the process according to the present invention, said sulphate molar ratio originating from sulfuric acid as well as possibly from the phosphate to calcium source present in the phosphate source is between 0.68 and 0.78, preferably between 0.7 and 0.75 at the entrance.
    More particularly, in the process according to the present invention, said sulphate molar ratio originating from sulfuric acid as well as possibly from the calcium phosphate source is between 0.68 and 0.78, preferably between 0.7 and 0.75 at the entrance.
    Preferably, the method according to the present invention comprises adding a base to said first suspension, before filtration.
    The addition of the base to the first suspension makes it possible to precipitate the calcium fluoride before filtration (pre-neutralization), which can prove to be advantageous depending on the desired final compounds and their use. If the added base is a calcium base, such as quicklime or slaked lime, powdery or in the form of milk of lime, or even limestone, the formation of gypsum before filtration is favored, which reduces the content of residual SO 3 in the liquid phase.
    In a variant, the method according to the invention comprises, before said step of recovering from said first liquid phase of said purified phosphate-based compound, an addition of a base to said first liquid phase after filtration with formation of a second suspension comprising a second solid matter in suspension in a second liquid phase and filtration of said second suspension to separate said second solid matter in suspension from said second liquid phase, said purified phosphate-based compound being thus recovered from said second liquid phase , from the first liquid phase
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    BE2018 / 5563 depleted in said second solid material, mainly calcium fluoride.
    In this embodiment, if a base was added before filtration, the calcium fluoride was removed during filtration and is present in the first solid matter, regardless of whether the purified phosphate compound is desired get either DCP or MCP and phosphoric acid. DCP production involves adding a calcium base to MCP (neutralization), which would also cause precipitation of calcium fluoride if it has not been removed beforehand.
    If no base was also added before the filtration of the first suspension, the first solid matter contains mainly calcium sulphate (calcium sulphate hemihydrate, anhydrite or gypsum), impurities and phosphate not attacked, while fluorine is still in the first liquid phase.
    When the addition of base is carried out in a controlled manner to the first liquid phase substantially depleted in first solid material, but still containing fluorine, it is then possible to selectively remove the calcium fluoride. In such a case, different stages can be envisaged later.
    If said purified phosphate-based compound thus recovered from said second liquid phase which it is desired to produce is MCP and / or phosphoric acid, the second liquid phase is recovered and then treated for this purpose.
    If said purified phosphate-based compound thus recovered from said second liquid phase which it is desired to produce is DCP, the second liquid phase is treated by subsequent addition of calcium base, such as quicklime or slaked lime, powdery or in the form milk of lime, or limestone. In this case, a third suspension is formed following the addition of calcium base to the second liquid phase which is
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    BE2018 / 5563 depleted in fluoride, which is then filtered to recover the third solid phase containing DCP.
    Of course, when the DCP may contain fluorine or when the phosphate source used does not contain fluorine, the second suspension is formed by adding a calcium base, such as quicklime or slaked lime, powdery or in the form of milk lime, or limestone in the first liquid phase, which will then be filtered to separate on the one hand the second solid matter which contains the DCP and on the other hand the second liquid phase which forms waste water, which can be recycled for the formation of the sulfuric acid solution for the acid attack of the phosphate source or for the dilution of the attack tank (s). In this case, the controlled addition of a base to selectively precipitate the fluoride is not necessary.
    In a particularly preferred embodiment, a base is added before filtration of the first solid material to precipitate the fluorides and remove them from the first liquid phase with calcium sulfate and unattacked calcium phosphate. The first liquid phase is then further treated by adding a calcium base, such as quicklime or slaked lime, powdery or in the form of lime milk, or even limestone to form a second suspension containing DCP precipitated as the second. solid matter, which will then be recovered from the second suspension by filtration, centrifugation, decantation or any other means of solid-liquid separation.
    Whether the DCP is formed from the first liquid phase or from the second liquid phase, a stoichiometric amount of calcium base, as mentioned above, is added to the first liquid phase or to the second liquid phase, for example in a neutralization reactor for precipitating the DCP, preferably with pH control up to a value between 5 and 6.
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    BE2018 / 5563
    A preferred way of precipitating the DCP is to add finely ground limestone to the first liquid phase or to the second liquid phase to neutralize the liquid phase which contains MCP and phosphoric acid. The neutralization preferably has a residence time of at least 30 minutes in order to allow the neutralization reaction and the evolution of CO 2 which takes place to end. In a preferred embodiment, to obtain the pH between 5 and 6, milk of lime is further added to ensure complete precipitation of the DCP and in this way extract all of the P 2 O 5 in the residual liquid.
    More particularly, in the method according to the present invention, said first solid material separated from said first liquid phase is recycled in whole or in part by introduction into the first suspension.
    Indeed, it may be advantageous to increase the content of solid matter in the first suspension, either in the attack tank or tanks, or in the filtration device to help the filtration of this or to be able to treat the phosphate of residual calcium found in the first solid.
    The first suspension containing calcium sulfate and optionally calcium fluoride is preferably recovered by any liquid / solid separation means such as a filtration device, such as a rotary filter manufactured by the applicant, centrifugation, decantation, hydrocycloning or a band filter to separate the first solid from the first liquid phase. The first liquid phase is a dilute solution of P2O5 containing a slight excess of sulfate, for example between 0.05 to 0.6%, preferably between 0.1 and 0.25%.
    During filtration, a washing with water can be carried out on the filtration device in order to displace the interstitial water from the cake and to recover the traces of P 2 O 5 remaining in the calcium sulphate cake. Calcium sulfate is washed and separated. However, before doing this
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    BE2018 / 5563 operation, a recycling of calcium sulphate in the attack tank (s) can be provided in order to improve the conditions of attack of the phosphate source and thus improve the precipitation of the calcium sulphate forming the first solid material so to facilitate the filtration thereof.
    Recycling can be provided either by recycling part of the washed calcium sulphate to the attack tank (s) and thus increasing the density of the calcium sulphate suspension significantly above 10% by weight relative to the total weight of the suspension.
    Recycling can alternatively be provided by installing a thickener of the first suspension prior to separation, part of the thickened suspension can then be removed and returned to the attack tank (s).
    Such recycling makes it possible to increase the density of solid material in the suspension in the attack tank (s) and facilitates the elimination of the supersaturation of calcium sulfate from the medium in the attack tank (s); this makes it possible to avoid the uncontrolled germination of this suspension and makes it possible to obtain calcium sulphate particles which are better crystallized in the first suspension. This recycling also makes it possible to avoid reactions blocking the reaction of attack of the ore by sulfuric acid.
    In a variant within the meaning of the present invention, said second solid material separated from said second liquid phase is recycled by introduction into the first suspension or into the second suspension. Preferably when said second solid material is calcium fluoride, it will not be recycled.
    Indeed, in certain cases, if the filtration proves to be complicated due to the low solid content, it may be advantageous to be able to increase the solid content by introducing the second solid in the first suspension or in the second suspension, for example to add seeds promoting crystallization.
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    In fact, when DCP is produced, the suspension which contains it is filtered or centrifuged in order to separate the DCP from the liquid phase. As the liquid phase is practically water, there is no need to wash the separate DCP cake and the liquid phase can advantageously be recycled in the sulfuric acid tank, in line or in situ in the or the attack tanks. In some cases, when the purification of the first liquid phase is well conducted, the amount of impurities is reduced, which precisely promotes the implementation of this recycling of the liquid phase recovered after isolation of the DCP.
    Preferably, said source of phosphate is defined as any phosphate material of organic or mineral origin which contains less than 45% by weight of P 2 O 5 relative to the total weight of the dry matter (dry 105 ° C); preferably less than or equal to 40%, preferably less than or equal to 30%, preferably less than or equal to 20%, preferably less than or equal to 10%. In this phosphate source, the calcium may or may not be linked to the phosphate, hydrogen phosphate and / or dihydrogen phosphate ion. Said source can be chosen from the group consisting of conventional phosphate rock, phosphate rock with a low P 2 O 5 content , ashes of different mineral or organic origins such as the anaerobic digestates of organic waste, such as for example slurry, sludge from sewage treatment plants, compost, manure, residues from the metallurgical, chemical industry including phosphate chemistry, food industry, sludge from sewage treatment plants, guano, bone ash, slurry, manure, green waste
    In another embodiment, the phosphate sources contain little or no calcium. For example, the calcium content of the phosphate source in this mode is 5% by weight, preferably 1% by weight, more preferably 0.1% by weight or less relative to the total weight of the dry matter ( dry 105 ° C). These sources of phosphates include iron phosphate, Al phosphate or organic phosphate. In this
    2018/5563
    BE2018 / 5563 mode, calcium can be added in the form of lime, milk of lime, calcium carbonate, calcium chloride and possibly phosphate rock containing calcium. The sulphate molar ratio originating from sulfuric acid as well as possibly from the source of phosphate to added calcium is between 0.6 and 0.8.
    As a general rule, if there is a Ca deficit, calcium can be added in the form of lime, whitewash, calcium carbonate, calcium chloride and possibly calcium-containing phosphate rock.
    By the terms "conventional phosphate rock" is meant within the meaning of the present invention, a rock which has a typical P 2 O 5 analysis greater than 25%, it may or may not be benefited, that is to say that 'it undergoes one or more physico-chemical treatments (grinding, screening, washing, flotation) which make it possible to increase the titer (P2O5) of the rock or not.
    By the terms “phosphate rock with a low P 2 O 5 content ”, is meant within the meaning of the present invention, a rock which has a typical P 2 O 5 analysis of less than 25%, preferably 20%.
    By the terms "ash, sludge from sewage treatment plants, bone ash, slurry and any raw material with a phosphate content less than or equal to 40% by weight of P 2 O 5 relative to the total weight "raw material" means sources of secondary phosphates, which are generally difficult to recover, such as, for example, ash from sludge from sewage treatment plants, vegetable matter (wood, wheat bran,) ash from clos d rendering, by-products from the incineration of waste or biomass to produce energy.
    More particularly, in the process according to the present invention, said purified phosphate-based compound is a monocalcium phosphate MCP, a bicalcium phosphate DCP, more particularly a bicalcium phosphate DCP of food grade (human food or
    2018/5563
    BE2018 / 5563 animal), a phosphoric acid and its derivatives, such as for example derived directly from said first liquid phase or a phosphoric acid produced from said DCP.
    By the terms “bicalcium phosphate (DCP)”, is meant a bicalcium phosphate (DCP) (in English dibasic calcium phosphate or dicalcium phosphate) of formula CaHPO 4 which can be in anhydrous form (DCPA), or dihydrate (DCPD).
    By the terms "food grade bicalcium phosphate (FAD)" is meant any FAD intended for animal feed (in particular the area of Feed Grade and Pet Food), intended for human food and for the dental and oral care industry.
    In a preferred embodiment of the method according to the present invention, said second liquid phase is recycled by introduction into said attack tank (s).
    Other embodiments of the process according to the invention are indicated in the appended claims.
    A subject of the invention is also a bicalcium phosphate DCP in anhydrous form, or dihydrate having a chloride content less than or equal to 0.025% by weight relative to the total weight of said bicalcium phosphate, and / or a fluoride content less than or equal to 2% by weight relative to the total weight of said bicalcium phosphate, and / or an Na 2 0 content less than or equal to 0.15% by weight, relative to the total weight of said bicalcium phosphate.
    More particularly, the present invention relates to a bicalcium phosphate DCP in anhydrous form, or dihydrate having a chloride content less than or equal to 0.02% by weight relative to the total weight of said bicalcium phosphate, and a lower fluoride content or equal to 1% by weight relative to the total weight of said bicalcium phosphate, more particularly, as an additive for animal feed.
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    Alternatively, the present invention relates to a bicalcium phosphate DCP in anhydrous form, or dihydrate having a chloride content less than or equal to 0.02% by weight relative to the total weight of said bicalcium phosphate, more particularly as an ingredient in fertilizers or still as a source of phosphate to attack in the production of phosphoric acid.
    Other embodiments of the dicalcium phosphate according to the invention are indicated in the appended claims.
    The present invention also relates to a use of the bicalcium phosphate DCP in anhydrous form, or dihydrate having a chloride content less than or equal to 0.02% by weight relative to the total weight of said bicalcium phosphate, and a lower fluoride content or equal to 1% by weight relative to the total weight of said bicalcium phosphate according to the present invention, in animal feed, in particular for feed grade (cattle, poultry, aquaculture, pig breeding) and domestic animals.
    The present invention also relates to a use of the bicalcium phosphate DCP in anhydrous form, or dihydrate having a chloride content less than or equal to 0.02% by weight relative to the total weight of said bicalcium phosphate, more particularly as an ingredient according to invention, in a fertilizer or as a phosphate source for the production of phosphoric acid.
    The present invention also relates to a bicalcium phosphate DCP in anhydrous form, or dihydrate obtained by the process according to the present invention.
    Advantageously, the bicalcium phosphate DCP in anhydrous form, or dihydrate obtained by the process according to the invention has a chloride content less than or equal to 0.025% by weight relative to the total weight of said bicalcium phosphate, and / or a lower fluoride content or equal to 2% by weight relative to the total weight of said phosphate
    2018/5563
    BE2018 / 5563 bicalcium, and / or an Na 2 0 content less than or equal to 0.15% by weight, relative to the total weight of said bicalcium phosphate.
    More particularly, the bicalcium phosphate DCP in anhydrous form, or dihydrate obtained by the process according to the invention has a chloride content less than or equal to 0.02% by weight relative to the total weight of said bicalcium phosphate.
    Advantageously, the bicalcium phosphate DCP in anhydrous form, or dihydrate obtained by the process according to the present invention has a fluoride content less than or equal to 1% by weight relative to the total weight of said bicalcium phosphate.
    Other characteristics, details and advantages of the invention will emerge from the description given below, without implied limitation and with reference to the examples.
    The method according to the present invention has a series of advantages allowing the implementation of a competitive method. Indeed, it allows the use of dilute sulfuric acid whose concentration is for example less than 14%, preferably between 0.5 and 10%, in particular between 1 and 7%, more particularly between 2 and 5% , more specifically between 3 and 4% by weight relative to the total weight of the dilute sulfuric acid, or alternatively a sulfuric acid for recycling, which reduces the cost of the raw materials. It allows, but is not limited to, attacking various sources of phosphates, such as rocks with a low P 2 O 5 content or secondary sources of phosphorus.
    The fact of working in sub-stoichiometry within the meaning of the present invention with an SO 4 / Ca ratio between for example 0.68 and 0.8 allows a saving of 20 to 25% in H 2 SO 4 and an extraction yield. advantageously greater than 85%, preferably greater than 90%.
    The attack time is relatively low, which can be as low as 90 minutes or less, such as between 30 and 60 minutes.
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    The attack temperature is also relatively low compared to a conventional attack process such as for example between 40 ° C and 60 ° C compared to conventional temperatures between 75 and 95 ° C, which allows energy savings.
    The P 2 O 5 content in the liquid phase in the first suspension is preferably between 1 and 5%, in particular between 1.5 and 3.5%, or even 2 to 3% by weight relative to the total weight of the first liquid phase.
    The process according to the present invention also makes it possible to obtain a purification rate of more than 50%, preferably more than 60% by weight of As, Al, U, Th, Na relative to the original weight of these elements contained in the phosphate source.
    More particularly, the present invention relates, without however being limited thereto to a DCP, for example obtained by the process according to the present invention having chloride and fluoride contents which make possible the applications in the human or animal food, know a chloride content of less than 0.025%, which can range up to contents as low as 1 ppm and fluoride content of less than 2%, which can range up to contents of as low as 0.1% by weight total of the DCP.
    Preferably, the DCP has low contents of residual SO 3 due to attack with very dilute sulfuric acid. The Na 2 0 content is also less than 0.15% by weight relative to the total weight of the DCP in certain embodiments.
    In an advantageous DCP product, the MgO content is also less than 1% by weight relative to the total weight of DCP.
    More particularly, an advantageous DCP according to the present invention has an Sr content of less than 100 ppm; preferably less than 50 ppm, more particularly less than 10 ppm, more specifically less than 1 ppm relative to the DCP.
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    The DCP according to the present invention also has a Th content typically less than 5 ppm relative to the DCP.
    Similarly, the content of Mn in the DCP according to the present invention is less than 10 ppm relative to the DCP.
    Typically, the Mo content in the DCP according to the present invention is less than 2 ppm relative to the DCP.
    Finally, the DCP according to the present invention preferably has a U 3 O 8 content of less than 32 ppm.
    Additionally object is a composition of bicalcium phosphate
    DCP including
    a) a CaO content greater than or equal to 40% by weight relative to the total weight of said bicalcium phosphate
    b) a chloride content less than or equal to 0.020% by weight relative to the total weight of said bicalcium phosphate
    c) a fluoride content of less than or equal to 2% by weight relative to the total weight of said bicalcium phosphate,
    d) an Na20 content less than or equal to 0.15% by weight relative to the total weight of said bicalcium phosphate
    As can be seen, the DCP according to the present invention has the qualities required for use in human or animal food as well as in technical applications.
    Examples Example 1.- attack of a phosphate source on a laboratory scale
    100 g of phosphate source (phosphate rock) containing
    30.5 g P 2 O 5 , 49.5% CaO equivalent, 3.95% fluorine, 0.308% equivalent
    Fe 2 O 3 , 0.547% of Al 2 O 3 equivalent and 0.303% of MgO equivalent, by weight relative to the weight of the phosphate source is brought into contact with sulfuric acid diluted to a concentration of 2% for an attack time
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    BE2018 / 5563 30 minutes, an attack temperature of 60 ° C and depending on the molar ratio
    SO 4 / Ca 0.8. The SO4 / Ca molar ratio defines the amount of acid required to attack the source of phosphate containing Ca at the inlet of the attack tank.
    Once all the additions have been made, the mixture is left to stir for half an hour before filtration.
    The suspension obtained is then filtered under vacuum on a büchner filter. The different quantities obtained are noted and the calcium sulphate and liquid phase products are analyzed.
    In the laboratory protocol, this is a batch process, without washing. However, the washing was extrapolated and the amount of P 2 O 5 in the impregnation liquid of the filter cake was calculated.
    The attack yield is calculated according to the following calculation:
    (Mass of P 2 O 5 in the filtrate + mass of P 2 O 5 in the impregnation liquid of the filter cake) / (total mass of P 2 O 5 in the phosphate source). The P 2 O 5 content in the impregnation liquid corresponds to P 2 O 5 which will be recoverable by washing the cake in an industrial process.
    The amount of dilute sulfuric acid added is 3499 g for an SO 4 content of 70.2 g. The SO 4 / Ca ratio is 0.8, due to the calcium content of the phosphate source.
    The liquid phase recovered has a volume of 3.09 liters for a mass of 3125 g, a pH of 2.1. The P 2 O 5 content in the liquid phase is 0.83% and the SO 3 content is 0.16% by weight relative to the weight of the liquid phase. The mass of P 2 O 5 in the impregnation liquid is 1.2 g.
    The CaO / P 2 O 5 molar ratio in the first solution is
    0.58, while the residual CaO content in the liquid phase is 0.19% by weight relative to the weight of the liquid phase.
    The P2O5 attack yield is 89%. As can be seen, despite the use of poorly concentrated sulfuric acid at 2% and
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    BE2018 / 5563 under sub-stoichiometric attack conditions for a total attack time of only 30 minutes, the attack yield of P 2 O 5 is significantly high.
    Example 2: attack of a phosphate source on a laboratory scale
    150 g of phosphate source (rock) containing 15.8 g of P 2 O 5 ,
    27.6% CaO equivalent, 2.2% fluorine, 2.37% Fe 2 O 3 equivalent, 2.88% Al 2 O 3 equivalent and 0.416% MgO equivalent, by weight per relative to the weight of the phosphate source is brought into contact with sulfuric acid diluted to a concentration of 5% for an attack time of 30 minutes, an attack temperature of 40 ° C. and according to the SO 4 ratio / Ca of 0.8 according to the protocol of Example 1:
    The amount of dilute sulfuric acid added is 1131 g for an SO 4 content of 61.0 g. The SO 4 / Ca ratio is 0.8, due to the calcium content of the phosphate source.
    The liquid phase recovered has a volume of 0.955 liters for a mass of 976 g, a pH of 1.8. The P 2 O 5 content in the liquid phase is 1.97% and the SO3 content is 0.27% by weight relative to the weight of the liquid phase. The mass of P 2 O 5 in the impregnation liquid is 3.24 g.
    The CaO / P 2 O 5 molar ratio in the first solution is
    0.43, while the residual CaO content in the liquid phase is 0.33% by weight relative to the weight of the liquid phase.
    The attack yield of P 2 O 5 is 95%. As can be seen, despite the use of low concentration sulfuric acid at 5% and a phosphate source containing very few phosphates, under sub-stoichiometric attack conditions for a total attack time of only 30 minutes, the attack yield of P 2 O 5 is significantly high.
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    Example 3.- attack of a phosphate source on a laboratory scale
    100 g of phosphate source (phosphate rock) containing
    30.5 g P 2 O 5 , 49.5% CaO equivalent, 3.95% fluorine, 0.308% equivalent
    Fe 2 O 3 , 0.547% of Al 2 O 3 equivalent and 0.303% of MgO equivalent, by weight relative to the weight of the phosphate source is brought into contact with sulfuric acid diluted to a concentration of 5% for an attack time of 30 minutes, an attack temperature of 60 ° C. and according to the SO 4 / Ca ratio of 0.8 according to the protocol of Example 1.
    The amount of dilute sulfuric acid added is 1398 g for an SO 4 content of 70.1 g. The SO 4 / Ca ratio is 0.8, due to the calcium content of the phosphate source.
    The liquid phase recovered has a volume of 1.13 liters for a mass of 1161 g, a pH of 2.2. The P 2 O 5 content in the liquid phase is 2% and the SO 3 content is 0.20% by weight relative to the weight of the liquid phase. The mass of P 2 O 5 in the impregnation liquid is 2.6 g.
    The CaO / P 2 O 5 molar ratio in the first solution is
    0.38, while the residual CaO content in the liquid phase is 0.30% by weight relative to the weight of the liquid phase.
    The P 2 O 5 attack yield is 85%. As can be seen, despite the use of low concentration sulfuric acid at 5% and sub-stoichiometric attack conditions for a total attack time of only 30 minutes, the attack yield of P 2 O 5 is significantly high.
    Comparative Example 1.- attack on a phosphate source on a laboratory scale
    100 g of phosphate source (phosphate rock) containing
    30.5 g P 2 O 5 , 49.5% CaO equivalent, 3.95% fluorine, 0.308% equivalent
    Fe2O3, 0.547% Al2O3 equivalent and 0.303% MgO equivalent, by weight per
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    BE2018 / 5563 relative to the weight of the phosphate source is brought into contact with sulfuric acid diluted to a concentration of 5% for an attack time of 30 minutes, an attack temperature of 60 ° C. but this time according to the SO 4 / Ca molar ratio of 1 according to the protocol of Example 1.
    The amount of dilute sulfuric acid added is 1747 g for an SO 4 content of 87.2 g. The SO 4 / Ca ratio is 1, due to the calcium content of the phosphate source.
    The liquid phase recovered has a volume of 1.4 liters for a mass of 1429 g, a pH of 2.1. The P 2 O 5 content in the liquid phase is 1.63% and the SO 3 content is 0.61% by weight relative to the weight of the liquid phase. The mass of P2O5 in the impregnation liquid is 3.5 g.
    The CaO / P 2 O 5 molar ratio in the first solution is 0.26, while the residual CaO content in the liquid phase is 0.17% by weight relative to the weight of the liquid phase.
    The P2O5 attack yield is 88%. As can be seen, in the comparative example under stoichiometric conditions, the specific consumption of sulfuric acid is greater for an attack yield of the same order. The consumption of calcium source necessary for neutralization will also be greater.
    Example 4.- Substoichiometric attack on phosphate rock on a pilot scale
    The pilot includes 3 agitated and thermostatically controlled tanks using double envelopes heated by oil. The tanks follow each other by overflow, the first two have a capacity of 20 liters and the third has a capacity of 30 liters and only serves as a buffer before filtration.
    liters of water are poured into the first tank and are heated to working temperature. The phosphate source as well as the dilute sulfuric acid are fed into the first reactor with
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    BE2018 / 5563 flow rates corresponding to the desired attack conditions (molar ratio SO 4 / CaO, attack time, concentration H 2 SO 4 for attack on the phosphate source, P 2 O 5 content in the attack tank ).
    The suspension produced overflows into the second reactor. The second reactor is intended to carry out neutralization before filtration. Neutralization before filtration is not carried out systematically.
    The suspension finally overflows into the third reactor which is used to supply the filtration cell.
    A quantity of suspension is filtered every 30 minutes.
    Two kinds of filtration are carried out alternately:
    - Filtration for recycling in the attack reactor:
    the filter cake is not washed and is recycled to the first (attack) reactor to increase the level of solids in the reaction medium. The liquid phase (filtrate) is poured into a drum and is kept for the neutralization and DCP production stage. This filtration step is certainly not required on an industrial scale. It can of course be carried out, but is not necessary. On a pilot scale, it is advantageous to carry out this step since it is preferable to increase the solid content in the attack reactor.
    - The calcium sulphate production filtration: here, the calcium sulphate cake is washed with a predetermined quantity of water to recover the P 2 O 5 contained in the impregnation liquid. The liquid phase and the washing filtrate are poured into the filtrate recovery tank. The calcium sulphate is discharged to be evacuated.
    The installation is in steady state, samples of calcium sulphate and liquid phase (filtrates) are taken for analysis and the various products are also analyzed.
    The yield is calculated as follows: the mass of P 2 O 5 in the liquid phase (g / h) / mass of P 2 O 5 in the phosphate source (g / h).
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    A source of rock phosphate containing 30.3% by weight of P 2 O 5 , 47.6% of CaO equivalent, 3.68% of fluorine, 0.144% of Fe 2 O 3 equivalent, 0.18 % of Al 2 O 3 equivalent and 0.542% of MgO equivalent, by weight relative to the weight of the phosphate source is added to the attack tank in the presence of sulfuric acid diluted to 10% by weight relative to the weight of the diluted acid, according to a SO 4 / Ca molar ratio of 0.8. The attack temperature is 60 ° C and the duration of the attack is approximately 1 hour. The pH in the attack tank is 2.04. The rock flow rate is 2.67 kg / h and the acid flow rate is 17.5 liters / h. The P 2 O 5 content in the attack suspension is 4.5% by weight relative to the total weight of the suspension.
    During filtration, the flow rate of liquid phase recovered is
    16.13 kg / h.
    The attack yield is 93%.
    As can be seen, the tests carried out in the laboratory are confirmed in a pilot, the attack yield of the phosphate rock in the presence of a dilute sulfuric acid and under conditions of low P 2 O 5 content in the tank. attack (<6%) and short attack time is particularly high when sub-stoichiometric conditions are operated
    EXAMPLE 5 Pilot Sub-Stoichiometric Attack of Phosphated Rock
    The driver used is that of example 4.-, the same process as in example 4.- is implemented there.
    The same source of phosphate as in Example 4.- is added to the attack tank in the presence of sulfuric acid diluted to 5% by weight relative to the weight of the diluted acid, according to a molar ratio SO 4 / Ca 0.7, due to the calcium content of the phosphate source. The attack temperature is 60 ° C and the duration of the attack is approximately 1 hour. The pH in the attack tank is 2.5. The rock flow is 3 kg / h and the flow
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    BE2018 / 5563 of acid is 35.6 liters / h. The P 2 O 5 content in the attack suspension is 2.32% by weight relative to the total weight of the suspension.
    On filtration, the flow rate of liquid phase recovered is 35.44 kg / h.
    The attack yield is 94%.
    As can be seen, compared with Example 4.-, despite the presence of a sulfuric acid twice as diluted, the yield of P 2 O 5 is even higher.
    EXAMPLE 6 Pilot Sub-Stoichiometric Attack of Phosphated Rock
    The pilot used is that of Example 4.-, the same process as in Example 4.- is implemented there, except for the fact that in the second reactor, namely the neutralization reactor before filtration, the pH was adjusted to 2.48 by adding lime milk Ca (OH) 2 .
    A source of rock phosphate containing 34.9% by weight of P 2 O 5 , 49.8% CaO equivalent, 3.78% fluorine, 0.136% Fe 2 O 3 equivalent, 0.386% d equivalent Al 2 O 3 and 0.156% equivalent MgO by weight relative to the weight of the phosphate source is added to the attack tank in the presence of sulfuric acid diluted to 5% by weight relative to the weight of the diluted acid, according to an SO 4 / Ca ratio of 0.8, due to the calcium content of the phosphate source. The attack temperature is 60 ° C and the duration of the attack is approximately 1 hour. The pH in the attack tank is 2. The rock flow rate is 2.6 kg / h and the acid flow rate is 35.7 liters / h. The P 2 O 5 content in the attack suspension is 2.10% by weight relative to the total weight of the suspension.
    On filtration, the flow rate of liquid phase recovered is 38.22 kg / h.
    The attack yield is 92%.
    Example 7.- Substoichiometric attack on phosphate rock on a pilot scale
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    The driver used is that of example 4.-, the same process as in example 4.- is implemented there.
    A source of phosphate in the form of rock containing 24.90% by weight of P 2 O 5 , 40.5% of CaO equivalent, 2.54% of fluorine, 3.97% of equivalent Fe 2 O 3 , 1 , 13% Al 2 O 3 equivalent and 1.88% MgO equivalent, by weight relative to the weight of the phosphate source, is added to the attack tank in the presence of sulfuric acid diluted to 5% in weight relative to the weight of the diluted acid, according to an SO 4 / Ca ratio of 0.8, due to the calcium content of the phosphate source. The attack temperature is 60 ° C and the duration of the attack is approximately 1 hour. The pH in the attack tank is 1.95. The rock flow rate is 3.19 kg / h and the acid flow rate is 34.5 liters / h. The P 2 O 5 content in the attack suspension is 1.82% by weight relative to the total weight of the suspension.
    On filtration, the flow rate of liquid phase recovered is 37.91 kg / h.
    The attack yield is 90%.
    Example 8: Production of DCP from phosphate rock on a pilot scale
    For the production of DCP, the pilot used to carry out the attack on the rock is used decoupled from this first attack. The equipment is therefore used sequentially.
    The pilot used is that of Example 4. In this example, the liquid phase recovered from the filtration of Example 7 is treated to precipitate the DCP by neutralization in the following manner:
    Quick lime (or limestone) is added to the nominal flow rate in the reactor into which the liquid phase recovered from Example 7 is also introduced, the pH is regularly checked.
    When the pH is 5.5 / 6, the filtrate feed pump is started. The pH is checked regularly and the flow
    2018/5563
    BE2018 / 5563 limestone or lime supply is suitable for maintaining a pH between 5.5 and 6.
    Filtration is carried out every half hour from the buffer reactor. Once in two, the filter cake containing calcium sulphate is recycled to the first etching reactor to increase the level of solids in the reaction medium.
    The production cake containing the precipitated DCP is recovered and the mother liquors are stored in a barrel. Samples of the products (DCP and mother liquors) are taken for analysis.
    The temperature for neutralization is 60 ° C. The pH in the first tank is 4.4 while it rises to 5.55 in the second tank. The quicklime flow rate is 1.05 kg / h.
    The DCP precipitation yield is calculated by the formula (P 2 O 5 content in DCP / P 2 O 5 content initially present in the MCP and acid solution) P 2 O 5 balance of the operation is 92%.
    Comparative example 2.- Substoichiometric attack on phosphate rock on a pilot scale
    The driver used is that of example 4.-, the same process as in example 4.- is implemented there.
    The same source of phosphate as in Example 4.- is added to the attack tank in the presence of sulfuric acid at 20% by weight relative to the weight of the acid, according to an SO 4 / Ca ratio of 0 , 8, due to the calcium content of the phosphate source. The attack temperature is 60 ° C and the duration of the attack is approximately 1 hour. The pH in the attack tank is 1.73. The rock flow rate is 5 kg / h and the acid flow rate is 15.6 liters / h. The P 2 O 5 content in the attack suspension is 7.10% by weight relative to the total weight of the suspension.
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    On filtration, the flow rate of liquid phase recovered is 13.3 kg / h.
    The attack yield is 65%.
    As can be seen, compared with Example 4.-, the presence of a more concentrated sulfuric acid and a P 2 O 5 content greater than 6% causes the yield to drop to 65%.
    It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made without departing from the scope of the appended claims.
    权利要求:
    Claims (15)
    [1]
    "CLAIMS"
    1. A method of acid attack on a phosphate source comprising calcium for the production of a purified phosphate-based compound comprising the steps of
    a) an acid attack using sulfuric acid from said phosphate source, for a predetermined period of time between 20 and 180 minutes with the formation of a first suspension containing a first solid material and a first liquid phase in which the first solid material is in suspension, said first solid material comprising at least calcium sulphate and impurities, said first liquid phase comprising phosphoric acid and dissolved monocalcium phosphate, said attack being carried out under conditions at entry according to which the sulphate molar ratio originating from sulfuric acid as well as possibly from the calcium phosphate source is between 0.6 and 0.8, and the P 2 O 5 content is less than 6%,
    b) a first filtration of said first boil with separation of said first solid material from said first liquid phase,
    c) recovery from said first liquid phase of a purified phosphate-based compound.
    [2]
    2. The method of claim 1, wherein said acid attack takes place in 1, 2 or more attack tanks.
    [3]
    3. The method of claim 1 or claim 2, wherein the predetermined period of time is less than 120 minutes.
    2018/5563
    [4]
    4. Method according to claim 2 or claim 3, BE2018 / 5563 wherein the content of P 2 O 5 in the liquid phase in the attack tank (s) is less than 5%.
    [5]
    5. Method according to any one of claims 2 to
    4, in which said attack is carried out at a temperature in the attack tank or tanks less than or equal to 90 ° C.
    [6]
    6. Method according to any one of claims 2 to
    5, in which the sulfuric acid is a dilute sulfuric acid, in particular before addition to the attack tank or tanks.
    [7]
    7. The method of claim 6, wherein said dilute sulfuric acid has a concentration of H 2 SO 4 less than or equal to 13% by weight.
    [8]
    8. Method according to any one of the preceding claims, in which the said sulphate molar ratio originating from sulfuric acid as well as possibly from the phosphate to calcium source present in the phosphate source is between 0.68 and 0, 78.
    [9]
    9. Method according to any one of the preceding claims, further comprising, an addition of a base to said first suspension, before filtration.
    [10]
    10. Method according to any one of claims 1 to
    9, further comprising, before said step of recovering from said first liquid phase of said purified phosphate-based compound, an addition of a base to said first liquid phase after filtration with the formation of a second suspension comprising a second material solid in suspension in a second liquid phase and filtration of said second suspension to separate said second solid matter in suspension from said second liquid phase, said purified phosphate-based compound being thus recovered from said second liquid phase, originating from the first phase liquid depleted in said second solid material.
    [11]
    11. Method according to any one of the preceding claims, in which said first solid material separated from said
    2018/5563
    RF2H18 / 55A3 first liquid phase is recycled by introduction into the first DE2U | O / 55 ° 3 suspension.
    [12]
    12. Method according to any one of the preceding claims, in which said source of calcium-containing phosphate is chosen from the group consisting of conventional phosphate rock, phosphate rock of low P 2 O 5 content , ash, sludge from wastewater treatment plants, bone ash, pig manure, chicken manure, ash from wastewater treatment plant sludge, sludge from wastewater treatment plant, and any raw material with a phosphate content less than 30% by weight of P 2 O 5 relative to the total weight of the raw material.
    [13]
    13. Method according to any one of the preceding claims, in which said purified phosphate-based compound is a monocalcium phosphate MCP, a bicalcium phosphate DCP, more particularly a bicalcium phosphate DCP of food grade, a phosphoric acid, such as for example from directly from said first liquid phase or a phosphoric acid produced from said DCP.
    [14]
    14. Method according to any one of claims 10 to
    13, in which the said second liquid phase is recycled by introduction into the said attack tank (s).
    [15]
    15. DCP bicalcium phosphate composition comprising
    a) a CaO content greater than or equal to 40% by weight relative to the total weight of said bicalcium phosphate
    b) A chloride content less than or equal to 0.020% by weight relative to the total weight of said bicalcium phosphate
    c) a fluoride content of less than or equal to 2% by weight relative to the total weight of said bicalcium phosphate,
    d) an Na 2 O content of less than or equal to 0.15% by weight relative to the total weight of said bicalcium phosphate.
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    公开号 | 公开日
    MA49829B1|2021-12-31|
    CA3072408A1|2019-02-14|
    BE1025894A1|2019-08-01|
    EA202090239A1|2020-05-12|
    UY37841A|2019-03-29|
    MA49829A|2021-05-12|
    CN110997560A|2020-04-10|
    AR112732A1|2019-12-04|
    ZA202000723B|2021-08-25|
    US20200165133A1|2020-05-28|
    LT3665124T|2021-12-27|
    DK3665124T3|2022-01-03|
    JOP20200027A1|2019-02-11|
    WO2019030403A1|2019-02-14|
    AU2018312948A1|2020-02-27|
    EP3665124B1|2021-09-29|
    IL272456D0|2020-03-31|
    BR112020002477A2|2020-07-28|
    KR20200040266A|2020-04-17|
    EP3665124A1|2020-06-17|
    PE20201139A1|2020-10-26|
    JP2020530431A|2020-10-22|
    PL3665124T3|2022-01-31|
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    法律状态:
    2020-04-09| FG| Patent granted|Effective date: 20200221 |
    2021-01-15| PD| Change of ownership|Owner name: PRAYON S.A.; BE Free format text: DETAILS ASSIGNMENT: CHANGE OF OWNER(S), FUSION; FORMER OWNER NAME: PRAYON TECHNOLOGIES Effective date: 20201030 |
    优先权:
    申请号 | 申请日 | 专利标题
    BE201705554|2017-08-11|
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