CN112850745B - Method for recycling waste incineration fly ash - Google Patents
Method for recycling waste incineration fly ash Download PDFInfo
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- CN112850745B CN112850745B CN202011592743.4A CN202011592743A CN112850745B CN 112850745 B CN112850745 B CN 112850745B CN 202011592743 A CN202011592743 A CN 202011592743A CN 112850745 B CN112850745 B CN 112850745B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/16—Halides of ammonium
- C01C1/164—Ammonium chloride
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/24—Sulfates of ammonium
- C01C1/244—Preparation by double decomposition of ammonium salts with sulfates
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/06—Preparation of sulfates by double decomposition
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D7/00—Carbonates of sodium, potassium or alkali metals in general
- C01D7/02—Preparation by double decomposition
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- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05C—NITROGENOUS FERTILISERS
- C05C3/00—Fertilisers containing other salts of ammonia or ammonia itself, e.g. gas liquor
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- C05—FERTILISERS; MANUFACTURE THEREOF
- C05D—INORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C; FERTILISERS PRODUCING CARBON DIOXIDE
- C05D1/00—Fertilisers containing potassium
- C05D1/02—Manufacture from potassium chloride or sulfate or double or mixed salts thereof
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- C01P2006/80—Compositional purity
Abstract
The invention discloses a method for recycling waste incineration fly ash, which is characterized by comprising the following steps: the method comprises the following steps: s1, adopting NaHCO3 as a reactant to remove acidic gas from the waste incineration flue gas by a dry method, washing the generated fly ash containing but not limited to sodium salt S2, separating water insoluble substances, dissolving soluble salt to form a salt solution S3, performing salt separation crystallization, and respectively extracting and crystallizing sodium salt in the fly ash solution; s4, reacting the sodium salt in the step S3 to generate sodium bicarbonate through a chemical reaction; and S5, returning the sodium bicarbonate generated in the step S4 to the dry deacidification process, and purifying the incineration flue gas as a reactant.
Description
Technical Field
The invention relates to the field of environmental protection, in particular to a method for recycling waste incineration fly ash.
Background
Flue gas generated in the waste incineration process contains a large amount of harmful components such as acid gas, heavy metal, dioxin and the like, and before being discharged, the flue gas needs to be subjected to purification treatment such as deacidification and the like. Deacidifying the flue gas, and generating fly ash accounting for 3-5% of the total amount of the waste incineration after the flue gas is purified, wherein the fly ash contains harmful components such as heavy metal, dioxin and the like, and is defined as hazardous solid waste (HW 18). The total quantity of the fly ash from the waste incineration in 2020 is counted to reach 1000 million tons, most of the existing treatment processes adopt a chelating and curing landfill method for disposal, not only can occupy a large amount of land resources, but also the chelating landfill has the risk of secondary pollution, so that the recycling and harmless utilization of the fly ash from the waste incineration have important significance.
The dry flue gas deacidification process using sodium bicarbonate (baking soda) as a reactant is mature and applied in Europe and America for more than 20 years, has good purification effect, and can realize ultralow emission. The dry method flue gas purification can be used in coal power plants and waste incineration plants, and can also be widely used in industrial furnaces in industries such as glass, cement, metallurgy and the like. The flue gas can be discharged in ultralow level by adopting baking soda dry flue gas purification, and the cyclic resource utilization of the waste incineration fly ash is realized.
The basic principle of the sodium bicarbonate for flue gas purification is that the sodium bicarbonate is used as a reactant for flue gas purification, and acid gases in the flue gas are removed through chemical reaction. The process directly sprays the sodium bicarbonate fine powder into the high-temperature flue gas. Sodium bicarbonate is decomposed at high temperature to produce sodium carbonate Na2CO3、H2O and CO2. Newly produced sodium carbonate Na2CO3Has high reaction activity at the moment of generation, and can efficiently react with acidic substances in the smoke. SO (SO)XThe removal rate of the catalyst reaches more than 95 percent, the removal rate of HCl can reach more than 99 percent, and the main chemical reaction equation is as follows:
2NaHCO3 == Na2CO3 + CO2 + H2O
Na2CO3 + SO2 + 0.5O2 == Na2SO4 + CO2
Na2CO3 + 2HCl == 2NaCl + CO2 + H2O
Na2CO3 + 2HF == 2NaF+ CO2 + H2O
……
however, in China, due to the cost factor, the flue gas purification process of the lime slurry semi-dry method is adopted in the waste incineration industry, and the generated fly ash is buried after chelation and solidification.
The fly ash produced in the dry deacidification process by using the baking soda comprises the following main components:
disclosure of Invention
The invention aims to provide a method for recycling waste incineration fly ash, which is used for purifying flue gas generated by waste incineration by using sodium bicarbonate to deacidify in a dry method, and completely recycling the generated fly ash. Not only realizes the complete zero landfill of the fly ash, but also reduces the comprehensive cost of the fly ash disposal because different components are utilized, and realizes sustainable economic operation.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for recycling waste incineration fly ash is characterized by comprising the following steps: the method comprises the following steps:
s1, adopting NaHCO3The fly ash generated by dry-method removal of acid gas from waste incineration flue gas as a reactant contains but is not limited to sodium salt;
s2, washing the fly ash with water, separating water-insoluble substances, and dissolving soluble salts to form salt solutions;
s3, salt separation and crystallization, namely, respectively extracting and crystallizing sodium salt in the fly ash solution;
s4, reacting the sodium salt in the step S3 to generate sodium bicarbonate through a chemical reaction;
and S5, returning the sodium bicarbonate generated in the step S4 to the dry deacidification process, and purifying the incineration flue gas as a reactant.
As a preferred technical scheme, the sodium salt comprises sodium chloride and sodium sulfate.
As a preferred technical scheme, NaHCO is adopted3And (4) performing dry method on the waste incineration flue gas as a reactant to remove acid gas, wherein the generated fly ash also comprises potassium salt, and in the step S3, performing salt separation crystallization to extract potassium salt for crystallization.
As a preferred technical scheme, the potassium salt is potassium chloride and/or potassium sulfate.
In a preferred embodiment, the water-insoluble material separated in step S2 is used as a building material for recycling treatment.
As a preferred solution, the potassium salt is converted to potassium chloride and/or potassium sulfate by a chemical reaction.
As a preferable technical solution, in the step S4, during the reaction of the sodium salt to generate sodium bicarbonate, ammonium salt is generated as a byproduct.
As a preferred embodiment, the sodium sulfate refers to sodium sulfate containing crystal water and/or sodium sulfate containing no crystal water.
As a preferable technical solution, in the step S2, the salt solution generated by water washing is purified and refined before salt separation crystallization, and the process is as follows: and adding a sulfide precipitator to precipitate and remove heavy metal ions in the salt solution.
As a preferable technical solution, in the step S2, the salt solution generated by water washing is purified and refined before salt separation crystallization, and the process is as follows: acid is added to neutralize the carbonate ions.
As a preferred technical solution, in the step S3, the sodium salt is separated from the salt solution by salt separation crystallization, which specifically includes the following steps:
s301: separating sodium sulfate crystals from the salt solution by adopting a low-temperature freezing crystallization method;
s302: sodium chloride crystals are separated from the salt solution by an evaporative crystallization method.
As a preferable technical solution, a step of removing residual sulfate ions is further included between the step S301 and the step S302, and the manner of removing sulfate is T1 or T2:
t1: removing residual sulfate ions in the salt solution by adopting barium salt or calcium salt;
t2: the residual sulfate ion in the salt solution is separated by a membrane technology.
As a preferred technical scheme, the potassium salt in the salt solution is separated by adopting freezing crystallization, and the method comprises the following specific steps:
the solution after the step S302 is frozen and crystallized again to precipitate potassium chloride crystals.
As a preferable embodiment, the mother liquor from which potassium chloride crystals are precipitated by freeze crystallization is returned to step S202, and the residual sodium chloride is evaporated and crystallized again.
As a preferable technical scheme, sodium salt crystals obtained by salt separation crystallization in the step S3 are dissolved into an aqueous solution and then react with bicarbonate ions to generate sodium bicarbonate.
As a preferable technical scheme, sodium chloride crystals obtained by salt crystallization in the step S3 are dissolved into an aqueous solution and then react with ammonium bicarbonate to generate sodium bicarbonate and ammonium chloride, and the ammonium chloride is separated out by cold crystallization or frozen crystallization;
and (4) dissolving the sodium sulfate crystals obtained by salt separation crystallization in the step (S3) into an aqueous solution, reacting with ammonium bicarbonate to generate sodium bicarbonate and ammonium sulfate, evaporating and concentrating the ammonium sulfate, and then performing cold crystallization or freezing crystallization to separate out the ammonium sulfate.
As a preferred technical scheme, if an ammonium chloride crystal or an ammonium sulfate crystal is obtained by adopting a cold separation crystallization mode, the bicarbonate and sodium chloride which are not completely reacted in the mother liquor are removed before the cold separation crystallization, and the removing method is any one of the following methods:
f1: heating the mother liquor by an ammonia distillation method to decompose ammonium bicarbonate in the mother liquor into carbon dioxide and ammonia gas; evaporating and crystallizing to separate out sodium chloride;
f2: adding acid into the mother liquor to neutralize carbonate ions; evaporating and crystallizing to separate out sodium chloride;
if ammonium chloride crystals or ammonium sulfate crystals are obtained by adopting a freezing crystallization precipitation method, bicarbonate radicals need to be removed before freezing precipitation, and the removal method is any one of the following methods:
q1: heating the mother liquor by an ammonia distillation method to decompose ammonium bicarbonate in the mother liquor into carbon dioxide and ammonia gas;
q2: adding acid into the mother liquor to neutralize carbonate ions.
Preferably, the potassium chloride obtained in step S3 and the sodium sulfate obtained in step S3 are dissolved in an aqueous solution to obtain sodium chloride and potassium sulfate.
As a preferred technical scheme, potassium chloride and sodium sulfate are dissolved in water, and glaserite crystals are firstly generated, which is the glaserite crystal generation process; the glaserite crystal and potassium chloride react in water to generate a potassium sulfate crystal, which is a potassium sulfate crystal generation process; the residual mother liquor returns to the glaserite crystal generation process.
As a preferred technical scheme, the method for recycling the waste incineration fly ash comprises the following specific processes:
(1) sodium bicarbonate is adopted for reaction and deacidification of the waste incineration flue gas; incinerator for disposing 600 tons of domestic garbage every day, and generated smoke 9.8Nm3Spraying 600 meshes of sodium bicarbonate fine powder in a spraying amount of 260kg per hour, wherein the emission amount of sulfur dioxide after flue gas purification is lower than 50 mg/Nm3Hydrogen chloride of less than 5mg/Nm3Thus, fly ash was obtained in an amount of 500kg per hour.
(2) Adding a proper amount of water into the fly ash generated by deacidification purification, and fully stirring to dissolve the soluble salt in the fly ash into the water as much as possible;
(3) and (2) carrying out solid-liquid separation on the dissolved feed liquid, filtering out water-insoluble substances, adding a flocculating agent into a salt solution to remove suspended matters in the solution, and adding sulfide (sodium sulfide and/or potassium sulfide) to deeply purify impurities such as heavy metals in the solution. Performing solid-liquid separation to obtain refined salt solution;
(4) adding acid into the solution obtained in the step (3) to neutralize carbonate ions; controlling the end point pH of the feed liquid to be 6.0-7.0; the acid is hydrochloric acid and/or sulfuric acid.
(5) Adopting a freezing crystallization process to the feed liquid obtained in the step (4), crystallizing and separating out sodium sulfate decahydrate crystals with uniform granularity, wherein the crystallization temperature is-5-0 oCThe yield of the sodium sulfate reaches 85-90%, and the purity of the sodium sulfate decahydrate reaches more than 99.0%;
(6) mother liquor after sodium sulfate decahydrate is separated by solid-liquid separation is added with a precipitator to further remove sulfate ions, so that the removal rate of residual sulfate ions reaches more than 95%; precipitants include, but are not limited to: removing sulfate ions in the solution by using any one of barium chloride dihydrate, calcium chloride dihydrate, barium hydroxide and calcium hydroxide or by adopting a membrane technology;
(7) after the solid-liquid separation of the mother liquor in the step (6), crystallizing and precipitating sodium chloride crystals with uniform particle size by adopting an evaporative crystallization process, wherein the evaporative crystallization temperature is 40-95 DEG oCThe purity of the sodium chloride reaches more than 97.5 percent;
(8) after the solid-liquid separation of the mother liquor in the step (7), a cooling crystallization process is adopted to crystallize and separate out particlesCooling the potassium chloride crystals with uniform temperature to crystallize at-10 to 5 DEG CoC, the purity of the potassium chloride reaches more than 97.5 percent;
(9) carrying out double decomposition reaction on the sodium sulfate decahydrate obtained in the step (5), ammonium bicarbonate and water according to the mass ratio of 1: 1.05-1.15: 2.2-2.26 to crystallize, thus obtaining a sodium bicarbonate crystal product, wherein the double decomposition reaction crystallization temperature is 32.5-40oCThe purity of the sodium bicarbonate reaches more than 97.0 percent;
(10) after the solid-liquid separation of the mother liquor in the step (9), a cooling crystallization process is adopted to crystallize and separate out mixed crystals of sodium sulfate decahydrate and ammonium bicarbonate, wherein the cooling crystallization temperature is-10 to-5oC, returning the mixed frozen salt to the metathesis reaction crystallization system in the step (9) to ensure that the cyclic crystallization yield of the sodium bicarbonate reaches more than 95 percent;
(11) after the solid-liquid separation of the mother liquor in the step (10), adding a sulfuric acid solution to remove residual bicarbonate ions and a very small amount of carbonate ions;
(12) and (3) crystallizing the neutralized mother liquor obtained in the step (11) to separate out ammonium sulfate crystals by adopting an evaporative crystallization process, wherein the evaporative crystallization temperature is 80-85 DEGoC, the purity of the ammonium sulfate reaches more than 99.0 percent;
(13) performing double decomposition reaction on the sodium chloride obtained in the step (7), ammonium bicarbonate and water according to a proper mass ratio for crystallization to obtain a sodium bicarbonate crystal product, wherein the double decomposition reaction crystallization temperature is 15-40 DEG oCThe purity of the sodium bicarbonate reaches more than 97.0 percent;
(14) adding hydrochloric acid after the solid-liquid separation of the mother liquor obtained in the step (13) to remove residual bicarbonate ions and a very small amount of carbonate ions in the feed liquid, wherein the neutralization temperature is 80-85 DEGoC；
(15) And (4) neutralizing the mother liquor in the step (14), crystallizing and precipitating sodium chloride crystals with uniform particle size by adopting an evaporation crystallization process, wherein the evaporation crystallization temperature is 50-95 DEG CoC, the purity of the sodium chloride reaches more than 97.5 percent;
(16) after the mother liquor in the step (15) is subjected to solid-liquid separation, adopting a cooling crystallization process to crystallize and separate out ammonium chloride crystals, and cooling the crystallization temperatureThe degree is 5 to-40oC, the purity of the ammonium chloride reaches more than 98.5 percent;
(17) mixing the potassium chloride prepared in the step (8), the sodium sulfate decahydrate prepared in the step (5) and water according to a mass ratio of 1: 11.6-11.7: 4.25-4.35, and crystallizing to obtain glaserite crystal at reaction temperature of 15-25%oC；
(18) And (3) mixing the potassium chloride prepared in the step (8), the glaserite prepared in the step (17) and water according to a mass ratio of 1: 6.122-6.13: 9.85-9.95, and performing reaction crystallization of potassium sulfate to obtain potassium sulfate crystal, wherein the reaction crystallization temperature is 15-25%oAnd C, returning the mother liquor obtained by solid-liquid separation to the step (17).
Compared with the prior art, the invention has the following beneficial effects:
sodium bicarbonate is used as a reactant to treat incineration flue gas, compared with lime slurry which is adopted in China in large quantity, acid gas in the flue gas can be better removed, and ultralow emission is realized.
The invention carries out cyclic resource utilization on the fly ash, and uses the baking soda as a reactant to realize ultralow emission. At the same time, the cost of using baking soda as reactant is reduced. And the fly ash is completely recycled without landfill, so that a large amount of land resources and the risk of secondary pollution are saved.
Meanwhile, as the fly ash contains sodium chloride and sodium sulfate, the salt in the fly ash is purified and crystallized respectively, and then sodium bicarbonate is generated by utilizing the characteristic that the sodium chloride and the sodium sulfate can react with the ammonium bicarbonate, and the generated sodium bicarbonate is sent back to the dry deacidification process to be used as a reactant, so that the smoke treatment cost is greatly reduced, and the production byproducts are ammonium sulfate and ammonium chloride which can be used as raw materials of chemical fertilizers and compound fertilizers.
The fly ash also contains a large amount of potassium chloride, sodium sulfate extracted from the fly ash after the potassium chloride is crystallized by salt separation can generate potassium sulfate, and the potassium sulfate is used as a potassium fertilizer.
Through the above steps, the respective utilization of the components in the fly ash is realized, and the harmlessness and the resource utilization of the materials are realized.
Drawings
FIG. 1 is a schematic diagram of a salt separation crystallization process.
FIG. 2 is a schematic diagram of a sodium sulfate decahydrate resource utilization process.
FIG. 3 is a schematic diagram of the process of recycling sodium chloride.
FIG. 4 is a schematic view of the process of recycling potassium chloride and sodium sulfate decahydrate.
FIG. 5 is a schematic view of the fly ash resource utilization of the present invention.
Detailed Description
The invention aims to overcome the defects of the prior art and provides a method for recycling waste incineration fly ash, which is further described in detail by combining with the embodiment.
Example 1
A method for recycling waste incineration fly ash resources is characterized in that NaHCO3 is adopted to perform dry deacidification on waste incineration flue gas, and the generated fly ash contains: na2SO4, NaCl, KCl;
the dry deacidification process comprises the following specific steps:
incinerator for disposing 600 tons of domestic garbage every day, and generated smoke 9.8Nm3Spraying 600 meshes of sodium bicarbonate fine powder in a spraying amount of 260kg per hour, wherein the emission amount of sulfur dioxide after flue gas purification is lower than 50 mg/Nm3Hydrogen chloride of less than 5mg/Nm3Thus, fly ash was obtained in an amount of 500kg per hour.
The method for recycling the fly ash generated by dry deacidification comprises the following steps:
(1) dissolving, removing impurities and purifying: the soluble salts were separated.
5kg of fly ash generated by dry deacidification and purification and 10kg of deionized water are taken to be stirred and dissolved for 30min, and the dissolving temperature is about 40oCAt this point, the soluble salts in the fly ash are dissolved. Insoluble materials were removed by filtration, the filter cake was washed with 1.1kg of deionized water, and the washing solution was mixed with the filtrate, the specific gravity of the mixed mother liquor was 1.264, and the pH was about 10.2. Adding 18.5g of sodium sulfide into the filtrate to generate black precipitate, and filtering and separating675ml of 36% hydrochloric acid is added dropwise into the mother liquor to remove carbonate ions in the mother liquor, and then the pH of the purified clear mother liquor is 6.95 and the specific gravity is 1.24. The treated insoluble material is used to produce construction raw materials, such as cement, which are sent to a cement kiln. And the insoluble substances in the fly ash are recycled.
(2) Fractional salt crystallization (separation of sodium sulfate, sodium chloride and potassium chloride): transferring the feed liquid dissolved with soluble salt into a 15L cooling crystallizer, starting a refrigerator, slowly cooling, wherein the cooling rate is 3-4 oCH, but the temperature was reduced to 13.5 oCIn this case, 10g of seed crystal was added, and the temperature was further lowered to-5 oCThe cooling rate is 4-6 oCH, when the temperature is stabilized at-5 oCThen, starting a feeding peristaltic pump, adjusting the feeding flow rate to 240ml/h, adjusting the outlet water temperature of a refrigerator, and maintaining the temperature of crystal slurry in the crystallizer to be-5 +/-0.2 in the whole crystallization process oCThe crystal mush is continuously and slowly discharged through a crystal mush discharge port, the liquid level of the crystal mush in the crystallizer is controlled to be stable, the crystal is washed by low-temperature water, the crystal product is analyzed by a gravimetric method, the purity reaches 99.43%, and the conversion rate of sodium sulfate in fly ash reaches 89.5%.
Barium chloride dihydrate is added into the sodium sulfate decahydrate frozen crystallization mother liquor, the addition amount is 16.0g/L, sulfate ions are further removed, and the removal rate of residual sulfate ions reaches 99.9%; separating to remove precipitate (barium sulfate as byproduct), transferring the mother liquid to evaporation crystallizer, regulating vacuum degree to-0.06 MPa, and slowly heating to 80 deg.C oCStarting a feeding peristaltic pump, adjusting the feeding flow rate to 120ml/h, controlling the temperature stability and the liquid level stability of crystal slurry, taking out the crystal slurry once when the content of the crystal slurry in the evaporation crystallizer reaches 30-40%, filtering and separating the crystal slurry while the crystal slurry is hot, rinsing the crystal with a small amount of water, and testing the purity of sodium chloride to 97.86% by chemical titration analysis.
The mother liquor after the solid-liquid separation of the sodium chloride crystal slurry adopts a cooling crystallization process to crystallize and separate out potassium chloride crystals with uniform granularity, and the cooling crystallization temperature is-10 DEGoAnd C, the purity of the potassium chloride reaches 98.7 percent. Chlorine in the fly ash is crystallized by a salt separation processSodium chloride, sodium sulfate and potassium chloride are separated out by mass crystallization.
(3) Sodium sulfate and ammonium bicarbonate metathesis crystallization: sodium sulfate decahydrate, ammonium bicarbonate and water are subjected to double decomposition reaction and crystallization according to the mass ratio of 1:1.1:2.4, and a sodium bicarbonate crystal product is prepared. The prepared sodium bicarbonate is sent to a dry deacidification process to be used as a reactant to react with flue gas, so that the quantity of purchased sodium bicarbonate is reduced, and the cost is saved. Sodium sulfate in fly ash is recycled
The metathesis crystallization temperature was 38 deg.C oCThe purity of the sodium bicarbonate reaches 97.8 percent. The mother liquor after solid-liquid separation is crystallized by adopting a cooling crystallization process to separate out mixed frozen salt of sodium sulfate decahydrate and ammonium bicarbonate, and the cooling crystallization temperature is-10 DEG CoC, returning the mixed frozen salt to a double decomposition reaction crystallizer of sodium sulfate and ammonium bicarbonate to ensure that the circulating crystallization yield of the sodium bicarbonate reaches 95 percent; mixing the mother liquor after the separation of the frozen salt, adding a sulfuric acid solution to remove residual bicarbonate ions and a very small amount of carbonate ions, and neutralizing at the temperature of 85 DEGoC; the neutralized mother liquor is subjected to an evaporative crystallization process to crystallize and separate out ammonium sulfate crystals with uniform granularity, wherein the evaporative crystallization temperature is about 85 DEGoAnd C, the purity of the ammonium sulfate reaches 99.35 percent.
(4) Sodium chloride and ammonium bicarbonate metathesis crystallization: carrying out double decomposition reaction on sodium chloride, ammonium bicarbonate and water according to the mass ratio of 1:1.32:2.78 for crystallization, and preparing a sodium bicarbonate crystal product. The prepared sodium bicarbonate is sent to a dry deacidification process to be used as a reactant to react with flue gas, so that the quantity of purchased sodium bicarbonate is reduced, and the cost is saved. The sodium chloride in the fly ash is recycled.
The crystallization temperature of the metathesis reaction is 15 oCThe purity of the sodium bicarbonate reaches 97.3 percent; adding hydrochloric acid solution into the mother liquor after solid-liquid separation to remove residual bicarbonate ions and a very small amount of carbonate ions, wherein the neutralization temperature is 85 DEGoC; the neutralized mother liquor is crystallized by an evaporative crystallization process to separate out ammonium sulfate crystals with uniform granularity, and the evaporative crystallization temperature is about 85 DEGoAnd C, the purity of the ammonium chloride reaches 98.5 percent.
(5) Preparing potassium sulfate from potassium chloride: the process comprises two parts, namely glaserite crystallization and potassium sulfate crystallization;
crystallizing glaserite: potassium chloride, sodium sulfate decahydrate and water in a mass ratio of 1: 11.7: 4.28 proportion (there is also a circulation mother liquid from potassium sulfate reaction crystallization) to obtain glaserite crystal, the reaction crystallization temperature is 15 deg.CoC；
Crystallization of potassium sulfate: the potassium chloride, the glaserite and the water are mixed according to the mass ratio of 1: 6.126: 9.9, the potassium sulfate is crystallized by reaction, and the reaction crystallization temperature is 15oAnd C, the purity of the potassium sulfate reaches 98.5%, and the mother liquor obtained by solid-liquid separation returns to the glaserite crystallizer.
The produced potassium sulfate is used as a potash fertilizer, so that the potassium chloride and the sodium sulfate are recycled.
Example 2
A method for recycling waste incineration fly ash resources is characterized in that NaHCO3 is adopted to perform dry deacidification on waste incineration flue gas, and the generated fly ash contains: na2SO4, NaCl, KCl;
the dry deacidification process comprises the following specific steps:
incinerator for disposing 600 tons of domestic garbage every day, and generated smoke 9.8Nm3Spraying 600 meshes of sodium bicarbonate fine powder in a spraying amount of 260kg per hour, wherein the emission amount of sulfur dioxide after flue gas purification is lower than 50 mg/Nm3Hydrogen chloride of less than 5mg/Nm3Thus, fly ash was obtained in an amount of 500kg per hour.
The method for recycling the fly ash generated by dry deacidification comprises the following steps:
(1) dissolving, removing impurities and purifying: 5.1kg of fly ash generated by dry deacidification and purification and 10kg of deionized water are taken to be stirred and dissolved for 45min, and the dissolving temperature is about 40 oCThe insoluble material was removed by filtration, the filter cake was washed with 1.2kg of deionized water, and the washing solution was mixed with the filtrate, the specific gravity of the mixed mother liquor was 1.262, and the pH was about 10.1. Adding 20g of sodium sulfide into the filtrate to generate black precipitate, filtering and separating, dropwise adding 680ml of 36% hydrochloric acid into the mother liquor to remove carbonate ions in the mother liquor, wherein the pH value of the purified clear mother liquor is 7.05 and the specific gravity is 1.24.
(2) Fractional salt crystallization (separation of sodium sulfate, sodium chloride and potassium chloride): transferring the feed liquid into a 15L cooling crystallizer, starting a refrigerator, slowly cooling, wherein the cooling rate is 4 oCH, but the temperature is reduced to 14 oCIn this case, 15g of seed crystal was added, and the temperature was further lowered to-5 oCCooling rate 5 oCH, when the temperature is stabilized at-5 oCThen, starting a feeding peristaltic pump, adjusting the feeding flow rate to be 220ml/h, adjusting the outlet water temperature of a refrigerator, and maintaining the temperature of crystal slurry in the crystallizer to be-5 +/-0.2 in the whole crystallization process oCThe crystal mush is continuously and slowly discharged through a crystal mush discharge port, the liquid level of the crystal mush in the crystallizer is controlled to be stable, the crystal is washed by low-temperature water, the crystal product is analyzed by a gravimetric method, the purity reaches 99.23 percent, and the conversion rate of sodium sulfate in fly ash reaches 90.2 percent. Adding calcium chloride dihydrate into the sodium sulfate decahydrate frozen crystallization mother liquor, wherein the addition amount is 10.7g/L, further removing sulfate ions, and the removal rate of residual sulfate ions reaches 95.8%; separating to remove precipitate (precipitate calcium sulfate dihydrate as byproduct), transferring the mother liquid of the freeze crystallization with deep sulfate radical removal to an evaporation crystallizer, starting a heating device and a vacuum device, adjusting the vacuum degree to-0.057 MPa, and slowly heating to 85% oCStarting a feeding peristaltic pump, adjusting the feeding flow rate to be 100ml/h, controlling the temperature stability and the liquid level stability of crystal slurry, taking out the crystal slurry once when the content of the crystal slurry in the evaporation crystallizer reaches 30-40%, filtering and separating the crystal slurry while the crystal slurry is hot, rinsing the crystal with a small amount of water, and testing the purity of sodium chloride to reach 97.6% by chemical titration analysis. The mother liquor after the solid-liquid separation of the sodium chloride crystal slurry adopts a cooling crystallization process to crystallize and separate out potassium chloride crystals with uniform granularity, and the cooling crystallization temperature is-10 DEGoAnd C, the purity of the potassium chloride reaches 98.6 percent. Sodium chloride, sodium sulfate and potassium chloride in the fly ash are separated out through a salting-out crystallization process.
(3) Sodium sulfate and ammonium bicarbonate metathesis crystallization: sodium sulfate decahydrate, ammonium bicarbonate and water are subjected to double decomposition reaction crystallization according to the mass ratio of 1:1.06:2.4 to prepare a sodium bicarbonate crystal product, and the double decomposition reaction crystallization temperature is 38oCThe purity of the sodium bicarbonate reaches 97.6 percent. The mother liquor after solid-liquid separation is prepared byCooling crystallization process, crystallizing to separate out mixed frozen salt of sodium sulfate decahydrate and ammonium bicarbonate, cooling to crystallization temperature of-10 deg.CoC, returning the mixed frozen salt to a double decomposition reaction crystallizer of sodium sulfate and ammonium bicarbonate to ensure that the circulating crystallization yield of the sodium bicarbonate reaches 95 percent; mixing the mother liquor after the separation of the frozen salt, adding a sulfuric acid solution to remove residual bicarbonate ions and a very small amount of carbonate ions, and neutralizing at the temperature of 80 DEG CoC; the neutralized mother liquor is subjected to an evaporative crystallization process to crystallize and separate out ammonium sulfate crystals with uniform granularity, wherein the evaporative crystallization temperature is about 80 DEGoAnd C, the purity of the ammonium sulfate reaches 99.23 percent.
(4) Sodium chloride and ammonium bicarbonate metathesis crystallization: performing double decomposition reaction on sodium chloride, ammonium bicarbonate and water according to the mass ratio of 1:1.3:2.8 to crystallize, thus obtaining a sodium bicarbonate crystal product, wherein the double decomposition reaction crystallization temperature is 15 oCThe purity of the sodium bicarbonate reaches 97.8 percent; adding hydrochloric acid solution into the mother liquor after solid-liquid separation to remove residual bicarbonate ions and a very small amount of carbonate ions, wherein the neutralization temperature is 80 DEGoC; the neutralized mother liquor is subjected to an evaporative crystallization process to crystallize and separate out ammonium sulfate crystals with uniform granularity, wherein the evaporative crystallization temperature is about 80 DEGoAnd C, the purity of the ammonium chloride reaches 98.5 percent.
(5) Preparing potassium sulfate from potassium chloride: the process comprises two parts, namely glaserite crystallization and potassium sulfate crystallization; potassium chloride, sodium sulfate decahydrate and water in a mass ratio of 1: 11.6: 4.3 (there is also a circulation mother liquid from potassium sulfate reaction crystallization) to obtain glaserite crystal, the reaction crystallization temperature is 15%oC; further, the mass ratio of potassium chloride to glaserite to water is 1: 6.13: 9.95, the potassium sulfate is crystallized by reaction, and the reaction crystallization temperature is 15oAnd C, the purity of the potassium sulfate reaches 98.2%, and the mother liquor obtained by solid-liquid separation returns to the glaserite crystallizer.
It should be noted that, based on the above-mentioned structural design, in order to solve the same technical problems, even if some insubstantial modifications or tints are made on the invention, the essence of the adopted technical solution is the same as the invention, and therefore, the technical solution should be within the protection scope of the invention.
Claims (10)
1. A method for recycling waste incineration fly ash is characterized by comprising the following steps: the method comprises the following steps:
s1: by using NaHCO3The fly ash generated by dry-method removal of acid gas from waste incineration flue gas as a reactant contains sodium salt and potassium salt; the sodium salts include sodium chloride and sodium sulfate; the potassium salt is potassium chloride;
s2: washing the fly ash with water, separating water-insoluble substances, and dissolving soluble salts to form salt solutions;
s3: performing salt separation crystallization, namely respectively extracting sodium salt from the fly ash solution for crystallization, and performing salt separation crystallization to extract sodium salt and potassium salt for crystallization; performing salt separation and crystallization to obtain sodium chloride, potassium chloride and sodium sulfate;
s4: sodium salt reacts to generate sodium bicarbonate by using the step S3 through a chemical reaction; the sodium salts include sodium chloride and sodium sulfate; dissolving sodium chloride obtained by salt separation crystallization into an aqueous solution, and reacting with ammonium bicarbonate to generate sodium bicarbonate and ammonium chloride; dissolving potassium chloride and sodium sulfate in an aqueous solution to react to generate potassium sulfate and sodium chloride;
s5: returning the sodium bicarbonate generated in the step S4 to the dry deacidification process, and using the sodium bicarbonate as a reactant to purify the incineration flue gas;
in the step S3, the separation of the sodium salt from the salt solution by salt separation crystallization specifically includes the following steps:
s301: separating sodium sulfate crystals from the salt solution by adopting a low-temperature freezing crystallization method;
s302: separating sodium chloride crystals from the salt solution by adopting an evaporative crystallization method;
the potassium salt in the salt solution is separated by adopting freezing crystallization, and the method comprises the following specific steps:
the solution after the step S302 is frozen and crystallized again to precipitate potassium chloride crystals.
2. The method according to claim 1, wherein the water-insoluble substances separated in step S2 are used as building materials for recycling treatment.
3. The method according to claim 1, wherein the sodium sulfate refers to sodium sulfate containing crystal water and/or sodium sulfate not containing crystal water.
4. The method according to claim 1, wherein in step S2, the salt solution generated by washing is purified and refined before salt separation and crystallization, and the process is as follows: and adding a sulfide precipitator to precipitate and remove heavy metal ions in the salt solution.
5. The method according to claim 1, wherein in step S2, the salt solution generated by washing is purified and refined before salt separation and crystallization, and the process is as follows: acid is added to neutralize the carbonate ions.
6. The method of claim 1, further comprising a step of removing residual sulfate ions between the step S301 and the step S302, wherein the sulfate ions are removed in a manner of T1 or T2:
t1: removing residual sulfate ions in the salt solution by adopting barium salt or calcium salt;
t2: the residual sulfate ion in the salt solution is separated by a membrane technology.
7. The method for recycling fly ash from waste incineration as a resource according to claim 1, wherein the mother liquor from which potassium chloride crystals are precipitated by freezing crystallization is returned to the step S302, and the residual sodium chloride is evaporated and crystallized again.
8. The method for recycling waste incineration fly ash according to claim 1, wherein sodium chloride crystals obtained by salt crystallization in step S3 are dissolved into an aqueous solution and then react with ammonium bicarbonate to generate sodium bicarbonate and ammonium chloride, and the ammonium chloride is precipitated by cold crystallization or frozen crystallization;
and (4) dissolving the sodium sulfate crystals obtained by salt separation crystallization in the step (S3) into an aqueous solution, reacting with ammonium bicarbonate to generate sodium bicarbonate and ammonium sulfate, evaporating and concentrating the ammonium sulfate, and then performing cold crystallization or freezing crystallization to separate out the ammonium sulfate.
9. The method for recycling fly ash from waste incineration as claimed in claim 8, wherein if ammonium chloride crystals or ammonium sulfate crystals are obtained by cold crystallization, the incompletely reacted bicarbonate and sodium chloride in the mother liquor are removed before the cold crystallization, and the removing method is any one of the following methods:
f1: heating the mother liquor by an ammonia distillation method to decompose ammonium bicarbonate in the mother liquor into carbon dioxide and ammonia gas; evaporating and crystallizing to separate out sodium chloride;
f2: adding acid into the mother liquor to neutralize bicarbonate radical ions; evaporating and crystallizing to separate out sodium chloride;
if ammonium chloride crystals or ammonium sulfate crystals are obtained by adopting a freezing crystallization precipitation method, bicarbonate radicals need to be removed before freezing precipitation, and the removal method is any one of the following methods:
q1: heating the mother liquor by an ammonia distillation method to decompose ammonium bicarbonate in the mother liquor into carbon dioxide and ammonia gas;
q2: adding acid into the mother liquor to neutralize bicarbonate ion.
10. The method according to claim 1, wherein the potassium chloride and the sodium sulfate are dissolved in water to generate glaserite crystals, which is a glaserite crystal generation process; the glaserite crystal and potassium chloride react in the water solution to generate a potassium sulfate crystal, which is a potassium sulfate crystal generation process; the residual mother liquor returns to the glaserite crystal generation process.
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| CN114260300A (en) * | 2021-12-24 | 2022-04-01 | 中国矿业大学(北京) | Method for synchronously solidifying toxic elements in fly ash and separating chlorine salt |
| TWI800193B (en) * | 2021-12-30 | 2023-04-21 | 信鼎技術服務股份有限公司 | Incineration plant carbon capture and fly ash sodium salt recovery system and method for sodium bicarbonate reuse |
| CN116282081A (en) * | 2023-05-17 | 2023-06-23 | 中国科学院过程工程研究所 | Method for preparing sodium bicarbonate from baking soda desulfurization ash |
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