• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to the extraction of lime from the fly ash and the residues from purification of the combustion gases, which as a result are transformed into an inert waste. A first stage includes carbonation with CO2 in water, obtaining (a solution with (Ca (CO3 H)2), soluble salts and heavy metals) and ashes from which iron oxides are extracted magnetically with complex heavy metals. A second stage, decarbonation, in which CaCO3 precipitate is obtained and a saline solution is processed in an E.D.R, resulting in heavy metal hydroxides and treated water. CO2 and process water are recovered and reused. The CaCO3 is valued for reuse in the purification of combustion gases. It is possible to obtain ashes with a very low leachable profile, which fall into the classification of inert waste. There is a residue of heavy and ferrous metals as a manageable waste. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2698149A1
    申请号:ES201830973
    申请日:2018-10-08
    公开日:2019-01-31
    发明作者:García Raúl Hernando；Carballeira Pablo Rodríguez
    申请人:Hernando Garcia Raul；Rodriguez Carballeira Pablo；
    IPC主号:
    专利说明:

    [0001] Lime recovery system of fly ash containing residues of combustion gas cleaning, achieving the inertization of these.
    [0002]
    [0003]
    [0004]
    [0005] SECTOR OF THE TECHNIQUE
    [0006]
    [0007] The present invention "CARBODESC", refers to a lime recovery system of fly ash and residues from combustion gas cleaning. Mainly from those coming from the incineration of RSU and that supposes the stabilization and reduction of the leaching to a very low profile that confers character of inerts. It is applicable in all types of MSW incinerators, power generation plants (combined cycles, thermal, coal), sinter plants and companies with coke ovens or blast furnaces and therefore guarantees the total inertization of the waste.
    [0008]
    [0009] BACKGROUND OF THE INVENTION
    [0010]
    [0011] Currently, different techniques related to the treatment of fly ash from MSW incinerators are applied. For some years now, the encapsulation or fixation to hydraulic binders (solidification and vitrification) has been working as the processes included in documents EP-A-0 362 125 and W092 / 15536 but without definitively eliminating heavy metals or soluble salts .
    [0012]
    [0013] There is a patent filed in document ES 467853 which shows the use of a rotary kiln in which the unburned fuel part in the fly ash is combusted, forming a flux which, when cooled, is added to the slag. It is a conclusion of an encapsulation method that does not try to extract the contaminants, but isolate them.
    [0014]
    [0015] Some patents try to solve problems related to the generation of smoke or ash from the incineration of urban solid waste. Thus in the patent 4397/77 April 6, 1977 in Switzerland, there is talk of a system of treatment but not of extraction of the contaminants in them present.
    [0016] Another patent with European application number 01928248.2 of 03.05.2001 "Process of purification of combustion gases when coming into contact with carbonic materials". In DE-A-3 717 506 describes the leaching of waste constituted by fly ash, whose waste water is brought to evaporation by precipitating the heavy metals. This technique is not effective alone because there are large fractions of heavy metals attached to unburned organic matter and insoluble salts. None of them results in inert ashes.
    [0017]
    [0018] In the patent of national origin P-201431832 being the same one of ownership of the one requesting the invention in progress, a similar process is approached to the motive of invention, but that unlike it has as its first object the total inertization of the ashes, extracting all the heavy metals and soluble salts that contain these and which also involves recovering part of the lime. This process is too broad since it consists of three stages, a first stage that involves a phase of carbonation and decarbonation that involves the extraction of a very small fraction of lime due to the low partial pressure of the C02 used, it recovers only about 7 gr of lime as CaCOj / L of solution. A second stage that involves the reaction of royal water with the ash treated in the first part and whose purpose is to extract all the heavy metals it contains by transforming them into chlorides, a third stage in which the solution containing the chlorides of Heavy metals are treated in an EDR to separate the metals from the water. It does not result from an effective application due to the small amount of lime recovered, which causes an excessive and unaffordable waste of royal water to be used to extract the heavy metals since a lot of alkaline neutralization must be used to neutralize the alkalinity due to lime. without extracting and that generates a greater added residue. In addition, it does not include anything other than treatment for the urban solid waste incineration sector.
    [0019]
    [0020] EXPLANATION OF THE INVENTION
    [0021]
    [0022] With the procedure object of the "CARBODESC" patent, the lime in the ash containing the residues of the flue gas cleaning is extracted and can be reused, reducing the leaching of pollutants from the treated ashes and constituting a risk for health and the environment. He proposes an invention that allows a solution Nevando to practice the technique that concerns us. The incineration of municipal solid waste, power generation plants, coke ovens and blast furnaces, and sinter plants, generate in their process fly ash and residues of combustion gas cleaning being retained by physical means such as bag filters , electro filters, etc. These ashes are classified as very dangerous and as such must be managed as hazardous waste, causing high costs and risk to the environment.
    [0023]
    [0024] They consist basically of oxides, sulfides, carbonates, chlorides, fluorides, silicates, ... metals of variable composition and concentration (figure.1). However, most metals are present as oxides, chlorides, sulfates and carbonates. Between 20-25% of the fly ash and 30-40% of the waste coming from the dry and semi-dry treatments are formed by water-soluble salts, so that fly ash and waste have a high degree of leaching, therefore, it is necessary to stabilize it before it is deposited on the ground.
    [0025]
    [0026] Among the main polluting components of these ashes are calcium salts, chlorides and heavy metals.
    [0027]
    [0028] The process focuses on the extraction of lime, soluble salts and heavy metals. The latter are attached to the solid particles or as products of the reaction of heavy metals with oxidants forming chlorides, sulfates or oxides.
    [0029]
    [0030] This process does not alter the usual productive system of the companies that generate this waste, but it is a complementary activity to the main one carried out by the company.
    [0031]
    [0032] The invention relates mainly to the soiubilization of the lime compounds present in them and their transformation into lime bicarbonates in order to extract them from the solution and precipitate them as calcium carbonates. Within the process, two options for the reuse of reclaimed lime are proposed, the first one is the reuse of the combustion gases directly as CaC03 and the other the reconversion of CaC03 to CaO with high reactivity. calcination. Both for use as limestone slurry or injectable quick lime in the scrubbers (figure 2), for the purification of the combustion gases of the aforementioned productive sectors.
    [0033] In a first phase of the treatment called "Carbonation", the ash and residues are treated in a solution of demineralized water from the recovery of this in the process of reversible electrodialysis (EDR), in relation 1: 4, ash / water, at a constant temperature of 25 ° C in a stirred reactor (figure 3). C02 (g) is injected at a proportional partial pressure, sufficient to dissolve the necessary amount of C02 that reacts with the lime to form calcium bicarbonate (figure 3). For the results of the analytical shown (figure 5), we have worked with a residue with a limestone proportion of 35%, at a proportional partial pressure of 45 bar. It dissolves 266 Kg of C02 for 4 m3 of water and one ton of waste, being able to react with the lime to get 604 Kg of CaCO3 or 338 Kg of CaO. 96% of the lime present in the residue is recovered. Depending on the lime present in the waste and the one to be extracted, we work with the partial pressure required for C02.
    [0034]
    [0035] The liquid-air interface in the reactor is very small, initially performing a vacuum so that the partial pressure is only that of C02. When the gas dissolves in the water it begins to react with it and with the lime at a proportional partial pressure of 45 bar, for in this case recovering 35% of lime present in 1 Tn of ash producing a carbonation through the solution. The lime is transformed into calcium bicarbonate at saturation of pH 6. This phase results in ash with very low leaching range (figure 5), noting that the values obtained are well below those required by European legislation to consider the possibility of taking them to landfill of non-hazardous.
    [0036]
    [0037] The choice of C02 against the use of mineral acids is because it is an inert and safe product, which does not need handling. The neutralization curve of water with C02 is smooth, unlike that of strong acids. The C02 allows a fine adjustment of the pH to 1/10 of a unit without the risk of over-acidification. No extraneous ions are added to the water (S04 =, CI, etc.), so no secondary saline substances are produced.
    [0038]
    [0039] The C02 when in contact with water forms carbonic acid H2C03 that acidifies the water reducing its pH. The carbon dioxide yields protons to the medium (H +) that will neutralize the bases present: hydroxides and carbonates mainly of lime since in carbonation with C02 the exchange complex has more affinity for divalent cations than for monovalent cations, that is, it will be greater for Ca + 2.
    [0040]
    [0041]
    [0042]
    [0043]
    [0044] The H + will neutralize the oxides, hydroxides and calcium carbonates, transforming them into soluble bicarbonates.
    [0045] CaC03 + C02 H20 -► Ca (HC03) 2
    [0046] 2C02 CaO H20 -> Ca (HC03) 2
    [0047] 2C02 Ca (0H) 2 ^ Ca (HC03) 2
    [0048]
    [0049] Working with the example at 45 bar, the partial pressure of the gas in the liquid tends to equalize with the pressure of the gas in the head of the liquid. reactor. When both are balanced, it will be understood that carbonation is complete. The regulation of the process is done by controlling the pH of the solution (it starts decreasing it from initial pH values that start very basic, pH 12, to the process reference value (pH 6) being automatically adjusted by injecting C02 or not)
    [0050]
    [0051] Calcium carbonate will not be soluble in water unless it drops below 8.3. The pH point at which the presence of carbonates is minimal and that of maximum bicarbonate is pH 6. This pH value was chosen because it is the most optimal from the point of view of lime extraction and because it stabilizes the mobility of the heavy metals in the ashes. Working at pH lower than 5.4, there are greater amounts of heavy metals desorbed from the ashes due to the protonation of some functional groups. The ash behaves like a positively charged matrix, so the surface charges become positive competing the protons ( H +) with the cations, for example (Pb2 +) and then exerting a repulsive force between them, mobilizing the metal cations. On the contrary, all C02 is as C02 (g) free and not as bicarbonates, preventing the extraction of lime.
    [0052]
    [0053] When carrying out the carbonation process and working with acidic pH (pH 6), the suitability is found between the correspondence of lime obtained, the mobilization of heavy metals and soluble salts, as well as a minimum leaching of pollutants in the treated ashes. Metals experience a series of reactions between the phase liquid and solid. The heavy metals that have not been extracted to the aqueous solution are adsorbed in the fly ash and leach minimally. These are heavy metals complexed or chelated by organic compounds, or those incorporated in the matrix of the ash. If there is no chemical decomposition of the ash or mineral alteration they will not be available.
    [0054]
    [0055] The aqueous solution resulting from carbonation contains heavy metals that were previously in ionic form in the ash solution in water, or as ions in organic and inorganic exchange complexes, or that were precipitated or coprecipitated. By lowering the pH and acidifying it has been possible to extract the ash through the aqueous phase to the decarbonator.
    [0056]
    [0057] Dissolved all the lime in the form of bicarbonates and stop the agitation decant the ashes into the reactor, maintaining the working pressure. Subsequently, the solution is transferred taking advantage of the pressure difference between the carbonator and that of a second reactor, decarbonator (Figure 4). In this, we work with a slight vacuum (0.5 bar) which causes that as the solution enters the reactor, a first degassing occurs when the partial pressure drops and 0O2 (g) is released. Once all the solution has been transferred, a forced aeration is carried out with an air flow rate of 15 L / min at 6 bar, forming air bubbles that will cause the release of the remaining C02. This causes an increase in pH that causes a decrease in the concentration of Ca (C03H) 2 without changing the alkalinity. It leads us to the saturation of the lime, beginning to precipitate CaCO3 from a pH of 6.5 to 8.5. In this way, CaC03 precipitate is obtained with a 95% richness and a particle size between 3.5 and 5 pm. Along with this lime, also precipitate small amounts of lead and zinc, which in the decarbonator as it increases the pH these cations are hydrolyzed forming precipitates of lead monohydroxide (PbOH +). At pH above 8, they will precipitate as white Pb (OH) 2. And by reaction with the chlorides of the solution will form lead (II) chlorides a white crystalline precipitate (PbCI2). Zinc also reacts with the chlorides giving a white precipitate (ZnCl2).
    [0058]
    [0059] Released C02 is separated from the air by liquefying it by increasing pressure and cooling it by reconditioning it to be used again in the carbonation process. The carbonate now precipitated, is extracted by means of a drum filter that works in a vacuum. Subsequently, it is passed through a filter press and dry to be reused as CaC03, or to be calcined converted to CaO. It is susceptible to be reused of any of the two species in the processes of purification of combustion fumes of the aforementioned industrial sectors.
    [0060]
    [0061] The remaining salt solution, once the lime has been extracted in the decarbonation phase, contains a very important amount of chlorides, phosphates, soluble salts, and heavy metals (figure 6). It is treated in an EDR process, in which the metals are separated. heavy in the form of hydroxides and a reusable water is obtained in the carbonation process.
    [0062]
    [0063] The ashes that result after carbonation are washed in the same reactor and are separated magnetically (figure.7) from them hydrated ferric oxides that formed complexes with heavy metals such as lead and zinc at acidic pH (6), these being managed as a final residue together with the heavy metal hydroxides from the EDR After this, the ashes are dried and conditioned resulting in an inert waste which can be managed as inert waste or being included as a stabilizing material in construction processes together with concretes.
    [0064]
    [0065] In the phase of E.D.R the percentage of reduction of soluble salts superior to 95%, achieving conductivities in the treated waters of between 1 - 50 fiS / cm.
    [0066]
    [0067] The (figure 5), shows analytical of the treated ashes, highlighting the minimum percentages leachable from the ashes after being treated. On the other hand, in (Figure 8) we see the result of the analytical for the percentage of lime recovered as CaO 53.7%. As what we have really extracted is lime in the form of calcium carbonate (CaC03) we must convert it to the latter by multiplying by 1.78, obtaining 95.6% of CaC03.
    [0068]
    [0069] Some treated ashes are exposed, free of 88% of calcium compounds and a considerable reduction of soluble salts and heavy metals. The largest percentage of compounds that will make up the ashes will now be carbon-based compounds, silica and harmless materials, making them totally inert and benefiting from changing the classification of hazardous to non-hazardous waste, and can be included as a supplement in asphalts, cements, etc.
    [0070] BRIEF DESCRIPTION OF THE DRAWINGS
    [0071]
    [0072] "To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, an assembly of drawings is included as an integral part of said description, in which, with an illustrative and non-limiting character, it has been represented the next:
    [0073] Figure 1.- Shows the gross characterization of fly ash and combustion residues in this case of MSW incineration.
    [0074] Figure 2.- Shows a scheme of the possibility of reusing recovered and reused lime as CaCO3 (calcite slurry) or as CaO (live lime slurry) in the process of purifying the combustion gases from the process.
    [0075] Figure 3.- Shows a perspective view of the Carbonator Reactor.
    [0076] Figure 4.- Shows a perspective view of the Decarbonator Reactor.
    [0077] Figure 5.- Shows the result of the ashes analytics after undergoing the CARBODESC process.
    [0078] Figure 6 .- Shows the result of the analytical saline solution resulting from decarbonation.
    [0079] Figure 7.- Shows a scheme of the magnetic separation of ferric oxides complexes hydrated with heavy metals.
    [0080] Figure 8.- Shows an analytical of the percentage of lime recovered as CaO and the conversion factor to multiply to transform it to CaCO3.
    [0081] Figure 9.- Shows a general outline of the CARBODESC process.
    [0082]
    [0083] PREFERRED EMBODIMENT OF THE INVENTION
    [0084]
    [0085] The present invention is for installation in the land adjacent to the incineration plants of RSU, electrical generation and sintering of metals. It consists of two reactors, one for carbonation that works at a proportional partial pressure (45 bar for the example) and a constant temperature of 25 ° C and with a regulation of the C02 injection by pH 6 control. Another reactor for decarbonation that works in depression (0.5 bar) at a constant temperature of 25 ° C, and to which a flow is injected of 15 l / min of air at 6 bar to favor degassing of C02. The pressure is regulated with the extraction of gases, and the process is controlled by pH increase and visually by precipitation of CaCO3. Both reactors work at 1500 and 1000 rpm respectively. They have pipes and mouths of entry and exit of products. We can see it in the figures (3 and 4). From a stack of membranes for the E.D.R and the equipment for conditioning the ashes and C02. The ashes are transported from the storage silos of the plants by pneumatic transport to the treatment facilities. The process requires the construction of a plant attached to the plants in which these waste is generated, or the construction of a single plant to treat the volume of several plants.
    权利要求:
    Claims (6)
    [1]
    1. Updated procedure "CARBODESC" for the acid treatment of fly ash and residues from the cleaning of the gases from the incineration of MSW with recovery of lime present in them, which entails the following stages:
    - Carbonation by injection of C02 with a proportional partial pressure capable of dissolving the amount of CO 2 necessary to react with the present lime and thus be able to extract it from an aqueous solution of ash with a solid-liquid ratio 1: 4, and brought to pH 6 until saturation. One obtains a saline solution containing calcium bicarbonate, soluble salts (mainly chlorides and phosphates) and heavy metals. On the other, hydrated ferric oxides that have complexed some heavy metals and that are separated from the ashes treated by magnetic filters. And finally, the aforementioned ashes with a range of leaching after treatment, very low, within values required by legislation for landfill of non-hazardous. - Decarbonation of the solution containing Calcium Bicarbonate, soluble salts and heavy metals, by degassing first by depressurization and then by forced aeration. Precipitated CaC03 and a soluble salt solution with heavy metals are obtained.
    - Reuse of the precipitated CaC03 as calcite slurry or its transformation by calcination to CaO to be reused as lime slurry, both in the combustion gas purification processes.
    - The saline solution is treated by reversible electrodialysis. A 95% concentrate of heavy metal hydroxides is obtained, and water with characteristics at the level of demineralized water.
    [2]
    2. A method according to claim 1, characterized in that it consists of extraction of lime from fly ash and waste gas cleaning from the treatment of acid gases from the combustion of RSU, by carbonation by injection of C02 at a proportional partial pressure of C02 (g) of 45 bar, which oscillates in function of the demand for lime to extract. In 1: 4 solution of ashes in demineralized water (according to claim 6) at 25 ° C in a stirred reactor. Work up to saturation up to pH 6. On the one hand, a solution of 95% of the lime present in the ashes is obtained in the form of calcium bicarbonate together with soluble salts and heavy metals. On the other hand some ashes with a very low leachable profile (inert ash).
    [3]
    3. A process according to claim 1 consisting of a process whereby the saline solution containing the dissolved calcium bicarbonate, soluble salts and heavy metals with a proportional partial pressure of 45 bar (according to claim 2) is taken to a decarbonator reactor that It works at 0.5 bar of regulated pressure and consists of a stirring system. In it, the solution is degassed first by depression (-45.5 bar) and then by forced aeration, and on the one hand the lime in solution is precipitated as CaC03, with 95% purity and a particle size between 3.5 and 5 pm . And on the other hand a saline solution composed mainly of chlorides, phosphates and other soluble salts, with pH 8.5 and temperature of 25 ° C.
    [4]
    4. A method according to claim 1 which consists in a process by which the hydrated ferric oxides carrying complex metals (according to claim 1) are extracted from the ash after carbonation, by magnetic separation. They are managed as final waste (according to claim 6).
    [5]
    5. A method according to claim 1, characterized in that the method determines the option of using the CaCOj obtained directly as calcite slurry in the gas cleaning processes, or transforming them to high reactivity CaO in a calcining oven to be reused as slurry. of quicklime in the purifying process of gases.
    [6]
    6. A method according to claim 1 containing the method of separating heavy metals from the solution (according to claim 3) by the application of reversible electrodialysis (E.D.R). From it, water similar to the demineralized characteristics to be reused in the carbonation process is obtained (according to claim 2). And a 95% heavy metal hydroxide concentrate that, together with the heavy metals adsorbed by the ferric oxides hydrated (according to claim 4), represent 3% by weight of the total of the ashes to be treated.
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    同族专利:
    公开号 | 公开日
    ES2698149B2|2019-06-10|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    FR2754747A1|1996-10-21|1998-04-24|Andre Accetta|Treatment of solid waste from incineration of domestic wastes|
    TW201602055A|2014-07-01|2016-01-16|國立聯合大學|Series treatment method favoring the reuse of MSWI fly ash|CN112108109A|2020-09-29|2020-12-22|华中科技大学|Preparation method of kaolin-based composite heavy metal additive and product thereof|
    CN112121755A|2020-09-29|2020-12-25|华中科技大学|Preparation method of alumina carrier calcium ferrite microcrystal heavy metal curing agent and product|
    CN112156750A|2020-09-30|2021-01-01|华中科技大学|Preparation method of fly ash carrier heavy metal adsorbent for pulverized coal and product thereof|
    CN110183126B|2019-06-06|2022-02-18|长沙紫宸科技开发有限公司|Method for preparing carbonate cementing material by taking limestone as raw material|
    法律状态:
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    优先权:
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    ES201830973A|ES2698149B2|2018-10-08|2018-10-08|Lime recovery system for fly ash containing waste from combustion gas cleaning, achieving the inertization of these|ES201830973A| ES2698149B2|2018-10-08|2018-10-08|Lime recovery system for fly ash containing waste from combustion gas cleaning, achieving the inertization of these|
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