Method for producing baking soda and ammonium sulfate by utilizing solid hazardous waste salt sodium sulfate

Abstract

The invention discloses a method for producing baking soda and ammonium sulfate by utilizing solid treatment hazardous waste salt sodium sulfate, and belongs to the technical field of chemical engineering. The method comprises the following steps: performing high-temperature refining on the waste salt sodium sulfate, mixing the refined waste salt sodium sulfate with ammoniated mother liquor, adding mixed salt for reaction, performing salting-out crystallization, and performing cold-out crystallization; cO2 is introduced into the cold separation mother liquor, ammonium bicarbonate solids and CO2 are added into the carbonized solution, sodium bicarbonate solids and mother liquor are formed through separation, ammonia gas is introduced into the mother liquor to enter an ammoniation process, the ammoniated mother liquor is subjected to salting-out crystallization, and circulation is formed; refining the double salt I to obtain mixed salt and mixed salt mother liquor, cooling the mixed salt mother liquor to obtain double salt II and an ammonium sulfate solution, evaporating the ammonium sulfate solution to obtain ammonium sulfate, and enabling the double salt II to enter a double salt refining process for recycling. Efficient treatment and resource utilization of the industrial waste salt are achieved, the process is environmentally friendly, secondary pollution is low, and the quality of the product baking soda and ammonium sulfate is stable.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology and relates to the treatment of industrial waste salt, specifically to a method for producing sodium bicarbonate and ammonium sulfate from hazardous waste salt from Ligu. Background Technology

[0002] Sodium sulfate in solid waste mainly comes from chemical by-products and wastewater treatment crystals. It usually contains a certain amount of impurities and generally undergoes pretreatment processes such as dissolution, filtration, and impurity removal. The pretreated sodium sulfate can be recycled.

[0003] Baking soda is an important alkali product widely used in the food, beverage, pharmaceutical, chemical, fire protection, aquaculture, and detergent industries. The traditional ammonia-soda process for producing baking soda involves pre-treating raw salt in a calcium removal tower, producing ammonia brine using an ammonia stripping tower, and then introducing carbon dioxide gas (produced in a lime kiln) into a carbonation tower to react with the ammonia brine to produce sodium bicarbonate. However, this method suffers from drawbacks such as a long process flow, high equipment investment, and high production costs. The metathesis process for producing baking soda mainly involves adding ammonium bicarbonate to the mother liquor and reacting it in a reactor. However, existing metathesis methods suffer from low conversion rates, the presence of sodium carbonate in the produced baking soda, lower quality baking soda with a pH > 8.3, and a particle size of over 300 mesh accounting for more than 80% of the total. Improving the utilization rate of ammonium bicarbonate in the system and refining the particle size and pH value of the baking soda are urgent technical problems that need to be solved in current baking soda production systems.

[0004] To address the aforementioned shortcomings of existing technologies, this invention develops a system for the recycling and regeneration of sodium sulfate from solid hazardous waste to produce sodium bicarbonate and ammonium sulfate. Summary of the Invention

[0005] The purpose of this invention patent is to provide a method for producing sodium bicarbonate and ammonium sulfate from hazardous waste sodium sulfate.

[0006] Another object of the present invention is to provide an apparatus for performing the aforementioned method for treating solid hazardous waste sodium sulfate.

[0007] This invention is achieved through the following technical solution: A method for producing sodium bicarbonate and ammonium sulfate from hazardous waste sodium sulfate involves recycling the waste sodium sulfate and reacting it with solid ammonium bicarbonate to produce sodium bicarbonate and the byproduct ammonium sulfate. The steps are as follows: Waste sodium sulfate is refined at high temperature and mixed with the mother liquor from the ammoniation process of sodium bicarbonate. Then, mixed salt is added for reaction, followed by salting out and crystallization, and then entering the cold crystallization process. The cold crystallization mother liquor is passed through CO2 to react, converting carbonate ions in the solution into bicarbonate ions for carbonation. After carbonation, ammonium carbonate solid and CO2 gas are added to the solution for full reaction, separating sodium bicarbonate solid and mother liquor. The mother liquor is passed through ammonia gas and enters the ammoniation process. The ammoniation mother liquor undergoes salting out and crystallization, forming a cycle. The first complex salt produced in the cold crystallization process is refined to obtain mixed salt and mixed salt mother liquor. After cooling, the mixed salt mother liquor yields second complex salt and ammonium sulfate solution. After evaporation of the ammonium sulfate solution, ammonium sulfate is obtained. Second complex salt enters the complex salt refining process for recycling.

[0008] Furthermore, the high-temperature refining of the waste salt sodium sulfate involves calcination at 800-1000℃ to completely remove organic matter from the waste salt, ensuring the stability of the mother liquor composition and product quality.

[0009] The pH of the sodium bicarbonate solid is <8.3. In the carbonation process, CO2 is mainly used to react with carbonate ions in the cold precipitation solution to generate bicarbonate ions, thereby reducing the carbonate content in the circulating mother liquor. In the sodium bicarbonate reaction process, an appropriate amount of CO2 gas is introduced to further reduce the carbonate content in the solution, ensuring that the pH of the sodium bicarbonate product is <8.3.

[0010] The cold crystallization process involves cooling the salt-out solids and mother liquor to 22-32°C within the cold crystallization process, thereby further precipitating the complex salt I in the solution.

[0011] The refining of the double salt involves mixing double salt I produced by cold crystallization and double salt II produced by the cooling process, adding water and an accelerator, and reacting them at 65-85°C to form a mixed salt and a mixed salt mother liquor.

[0012] In the refining process of the double salt, the mass ratio of water, accelerator, and double salt II is 0.2-0.6:0.01-0.05:1.

[0013] The cooling of the double salt adopts the principle of vacuum flash evaporation, which uses vacuum to reduce the temperature of the mixed salt mother liquor to 25-35℃. The double salt produced during the cooling process is returned to the double salt refining process.

[0014] The ammonium sulfate evaporation is carried out using negative pressure vacuum evaporation. The ammonium sulfate evaporation control node is controlled to ensure that the quality of ammonium sulfate meets the requirement of nitrogen content >20.5%. The separated mother liquor is returned to the cooling process.

[0015] This invention treats solid hazardous waste sodium sulfate by using a recycling method to produce sodium bicarbonate and ammonium sulfate. The sodium bicarbonate production system mainly includes a carbonization process for the cold precipitate mother liquor, a reaction between the carbonized mother liquor and ammonium bicarbonate in the sodium bicarbonate, centrifugal separation of the sodium bicarbonate slurry, and ammoniation of the sodium bicarbonate mother liquor. The carbonization process of the cold precipitate mother liquor mainly utilizes carbon dioxide gas to react with carbonate ions in the cold precipitate solution to generate bicarbonate ions, reducing the carbonate ion content in the recycled mother liquor. The carbonized mother liquor is fed into a sodium bicarbonate reactor, where it reacts fully with the ammonium bicarbonate solid to produce solid sodium bicarbonate. An appropriate amount of [unspecified substance] is introduced into the sodium bicarbonate reaction process. CO2 gas further reduces the carbonate content in the solution; the ammoniation system allows the baking soda mother liquor to absorb ammonia, which reacts with sodium bicarbonate / ammonium bicarbonate in the solution to form sodium carbonate / ammonium carbonate, preventing the formation of fine particulate baking soda solids during the cold precipitation crystallization process; the mother liquor recycling system includes a high-temperature refining process for waste sodium sulfate, a salt-precipitation crystallization process for refined sodium sulfate, and a cold precipitation crystallization process; the high-temperature refining of solid waste sodium sulfate mainly involves calcination at 800-1000℃ to completely remove organic matter from the waste salt, ensuring the stability of the mother liquor composition and product yield. The product quality meets relevant standard requirements; the main function of the salting-out crystallization process is to fully dissolve the refined sodium sulfate and the mixed salt produced in the subsequent double salt refining process in the ammonified sodium bicarbonate mother liquor, while forming double salt one; the main function of cold crystallization is to cool the salting-out solid slurry and mother liquor to 22-32℃ in the cold crystallization process, further precipitating double salt one in the solution; the ammonium sulfate system mainly includes the double salt refining process, the mother liquor cooling process, and ammonium sulfate evaporation; the double salt refining process mainly involves double salt one produced by cold crystallization and double salt two produced by the cooling process, and adding [the following ingredients] in the double salt refining process. Water and accelerator react fully with the accelerator at 65-85℃ to form mixed salt and mixed salt mother liquor, wherein the mass ratio of water:accelerator:double salt II is (0.2-0.6):(0.01-0.05):1; the double salt cooling process adopts the principle of vacuum flash evaporation and cooling, using vacuum to reduce the temperature of the mixed salt mother liquor to 25-35℃, and the double salt II generated during the cooling process is returned to the double salt refining process; ammonium sulfate evaporation can be carried out by negative pressure vacuum evaporation, controlling the ammonium sulfate evaporation control point to ensure that the quality of ammonium sulfate meets the requirement of nitrogen content >20.5%, and the separated mother liquor is returned to the cooling process.

[0016] This invention achieves efficient treatment and resource utilization of industrial waste salt. By introducing ammonia into the baking soda mother liquor, bicarbonate ions in the solution are converted into carbonate ions, preventing the production of small-particle baking soda in the mother liquor circulation system, thus ensuring the particle size of baking soda in the baking soda reaction system. The mother liquor circulation system and ammonium sulfate refining system ensure that the utilization rate of ammonium carbonate in the system reaches over 90%. The mother liquor carbonization process involves introducing a certain amount of CO2 gas to increase the carbonization degree of the mother liquor, reducing the carbonate content in the solution and improving the particle size and pH value of the baking soda. The production process is environmentally friendly, reducing secondary pollution and conforming to the concept of green chemistry. The resulting baking soda and ammonium sulfate have stable quality and high economic value. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1 As shown in the diagram, sodium sulfate, a solid hazardous waste generated from industries such as petrochemicals, coal chemicals, metallurgy, and new energy batteries, is recycled to produce sodium bicarbonate and ammonium sulfate. The steps are as follows: (1) After the mother liquor from the cold crystallization process enters the carbonization process, it reacts with CO2 in the system to convert carbonate ions in the solution into bicarbonate ions; the carbonized mother liquor enters the sodium bicarbonate reaction process and reacts fully with the added ammonium carbonate solid to generate sodium bicarbonate; an appropriate amount of CO2 gas is introduced into the sodium bicarbonate reaction process, and after the reaction, the sodium bicarbonate solid and mother liquor are obtained by centrifugation. (2) The mother liquor obtained in step (1) enters the ammoniation process. In the ammoniation process, the bicarbonate in the mother liquor reacts with the ammonia to produce carbonate. After ammoniation, the mother liquor enters the mother liquor circulation system for salt precipitation crystallization. (3) Waste salt sodium sulfate is refined by high-temperature calcination at 800-1000℃ to completely remove organic matter from the waste salt. The refined sodium sulfate enters the salting-out crystallization process and reacts fully with the mother liquor after ammoniation to generate double salt I. The solid slurry and solution of salting-out crystallization enter the cold crystallization process, and the temperature of the cold crystallization solution is controlled at 22-32℃ to further generate double salt I. After separation, double salt I and cold crystallization mother liquor are obtained. The cold crystallization mother liquor enters the carbonization process, and the solid double salt I enters the ammonium sulfate system. (4) The first double salt enters the ammonium sulfate system for double salt refining. It is then combined with the second double salt returned from the cold precipitation system, along with an accelerator and water. The water:accelerator:double salt ratio is (0.2~0.6):(0.01~0.05):1. The mixture reacts fully at 65-85℃ to obtain a mixed salt solid and mother liquor. The mixed salt solid is returned to the salting-out crystallization process. The mother liquor enters the cooling process, where vacuum flash evaporation lowers the solution temperature to 25-35℃, precipitating the second double salt from the solution. This precipitate is then returned to the double salt refining process. The mother liquor enters the ammonium sulfate evaporation process. Vacuum evaporation is used in the ammonium sulfate evaporation process, controlling the ammonium sulfate evaporation control point to ensure the ammonium sulfate quality meets the nitrogen content requirement of >20.5%. The separated mother liquor is then returned to the cooling system.

Claims

1. A method for producing sodium bicarbonate and ammonium sulfate from hazardous waste sodium sulfate, characterized in that, The process involves recycling waste sodium sulfate and reacting it with solid ammonium bicarbonate to produce sodium bicarbonate and the byproduct ammonium sulfate. The steps are as follows: Waste sodium sulfate is refined at high temperature and mixed with the mother liquor from the ammoniation process of sodium bicarbonate. Then, mixed salt is added for reaction, followed by salting out and crystallization, and then entering the cold crystallization process. The cold crystallization mother liquor is passed through CO2 to react, converting carbonate ions in the solution into bicarbonate ions for carbonation. After carbonation, ammonium carbonate solid and CO2 gas are added to the solution for full reaction, separating sodium bicarbonate solid and mother liquor. The mother liquor is passed through ammonia gas and enters the ammoniation process. The ammoniation mother liquor undergoes salting out and crystallization, forming a cycle. The first complex salt produced in the cold crystallization process is refined to obtain mixed salt and mixed salt mother liquor. After cooling, the mixed salt mother liquor yields second complex salt and ammonium sulfate solution. After evaporation of the ammonium sulfate solution, ammonium sulfate is obtained. Second complex salt enters the complex salt refining process for recycling.

2. The method according to claim 1, characterized in that, The high-temperature refining of the waste salt sodium sulfate involves calcination at 800-1000℃ to completely remove organic matter from the waste salt.

3. The method according to claim 1, characterized in that, The pH of the sodium bicarbonate solid is <8.

3.

4. The method according to claim 1, characterized in that, The cold crystallization process involves cooling the salt-out solids and mother liquor to 22-32°C within the cold crystallization process, thereby further precipitating the complex salt I in the solution.

5. The method according to claim 1, characterized in that, The refining of the double salt involves mixing double salt I produced by cold crystallization and double salt II produced by the cooling process, adding water and an accelerator, and reacting them at 65-85°C to form a mixed salt and a mixed salt mother liquor.

6. The method according to claim 5, characterized in that, In the refining process of the double salt, the mass ratio of water, accelerator, and double salt II is 0.2-0.6:0.01-0.05:

1.

7. The method according to claim 1, characterized in that, The cooling of the double salt adopts the principle of vacuum flash evaporation, which uses vacuum to reduce the temperature of the mixed salt mother liquor to 25-35℃. The double salt produced during the cooling process is returned to the double salt refining process.

8. The method according to claim 1, characterized in that, The ammonium sulfate evaporation is carried out using negative pressure vacuum evaporation. The ammonium sulfate evaporation control node is controlled to ensure that the quality of ammonium sulfate meets the requirement of nitrogen content >20.5%. The separated mother liquor is returned to the cooling process.

Images