System and method for separating and purifying ammonium sulfate in electrolytic manganese residues

Abstract

The system comprises a mixed gas pipeline, a heat exchanger a, a heat exchanger b, a heat exchanger c and a multi-stage refrigerating unit, the heat exchanger a, the heat exchanger b and the heat exchanger c are sequentially connected in series, the multi-stage refrigerating unit feeds cold media into the heat exchanger a, the heat exchanger b and the heat exchanger c for heat exchange, and the mixed gas pipeline is communicated with the heat exchanger a; and the output ends of the heat exchanger a, the heat exchanger b and the heat exchanger c are respectively provided with a gas-liquid separation tank a, a gas-liquid separation tank b and a gas-liquid separation tank c. According to the system and the method for separating and purifying the ammonium sulfate in the electrolytic manganese residues, gaseous sulfuric acid, sulfur dioxide, ammonia gas and nitrogen in mixed gas are respectively condensed and gradually recovered by utilizing the characteristic that the boiling points of the gaseous sulfuric acid, the sulfur dioxide, the ammonia gas and the nitrogen are different, components are used for recovering the ammonium sulfate and the nitrogen, and the sulfur dioxide is separated out; the ammonium sulfate recovery efficiency reduction caused by sulfur dioxide influence is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of equipment and method for recovering ammonium sulfate from electrolytic manganese slag, in particular to a system and method for separating and purifying ammonium sulfate from electrolytic manganese slag. Background Art

[0002] Electrolytic manganese ammonium sulfate slag contains approximately 45% ammonium sulfate. Because this type of double salt is a mixture of ammonium sulfate, manganese sulfate, magnesium sulfate, calcium sulfate, and other sulfates, the ammonium sulfate cannot be directly utilized, resulting in the mixture being stored. According to Chinese Patent 2025103245795, a system and method for producing ammonium sulfite from electrolytic manganese ammonium sulfate double salt is proposed. Ammonium sulfate undergoes a decomposition reaction at a certain temperature to produce ammonia and ammonium bisulfate. Electrolytic manganese ammonium sulfate slag contains ammonium sulfate and other impurities. By controlling the conditions of low-temperature calcination, the ammonium sulfate is preferentially decomposed and volatilized in a gaseous form. The volatilized ammonia and ammonium bisulfate are then collected and converted using a specific device to regenerate ammonium sulfate, thereby achieving ammonium sulfate recovery.

[0003] During the low-temperature calcination process, excessively high temperature may cause excessive decomposition of ammonium sulfate, generating gases such as nitrogen and sulfur dioxide that are difficult to recover, thereby reducing the recovery efficiency of ammonium sulfate. Nitrogen is a gas with relatively stable chemical properties, is difficult to dissolve in water, and does not chemically react with ammonium sulfate or water. However, sulfur dioxide is easily soluble in water and reacts with water to form sulfurous acid, which increases the hydrogen ion concentration in the solution and enhances the acidity of the solution. Ammonium sulfate is a strong acid and weak base salt, and its hydrolysis is acidic. The change in the acidity of the solution will inhibit the hydrolysis of ammonium ions in ammonium sulfate, causing the solubility of ammonium sulfate in water to change, thereby affecting the absorption effect of water on ammonium sulfate, thereby reducing the recovery efficiency of ammonium sulfate. For this reason, the present application is proposed. Summary of the Invention

[0004] The object of the present invention is to provide a system and method for separating and purifying ammonium sulfate from electrolytic manganese slag to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: A system for separating and purifying ammonium sulfate from electrolytic manganese slag comprises a mixed gas pipeline, a heat exchanger a, a heat exchanger b, a heat exchanger c, and a multi-stage refrigeration unit. The heat exchangers a, b, and c are connected in series in sequence. The multi-stage refrigeration unit supplies cold medium to the heat exchangers a, b, and c for heat exchange. The mixed gas pipeline is in communication with the heat exchanger a. The output ends of the heat exchangers a, b, and c are respectively provided with gas-liquid separation tanks a, b, and c, for separating sulfuric acid, sulfur dioxide, and ammonia. The liquid ammonia outputted from the gas-liquid separation tank c is connected to a heating reactor b via a liquid ammonia pipeline. The sulfuric acid outputted from the gas-liquid separation tank a is connected to a reactor via a sulfuric acid pipeline. The heating reactor b is connected to the reactor via an ammonia pipeline.

[0006] As a further solution of the present invention: the heat exchange temperature of the heat exchanger a is 50-0°C, the heat exchange temperature of the heat exchanger b is -15--35°C, and the heat exchange temperature of the heat exchanger c is -40--50°C.

[0007] As a further solution of the present invention: the liquid phase output end of the gas-liquid separation tank b is connected to the heating reactor a through a sulfur dioxide pipeline, the heating reactor a is connected to the absorption tower through a separation pipeline, and the top of the absorption tower is connected to the heating reactor b through an ammonia recovery pipeline.

[0008] As a further solution of the present invention: the absorption tower is provided with a dosing pipeline and an absorption liquid pipeline.

[0009] As a further solution of the present invention: the heat exchanger a and the heat exchanger b are connected by a conveying line a, the gas-liquid separation tank a is arranged on the conveying line a, the liquid phase output end of the gas-liquid separation tank a is connected to the sulfuric acid pipeline, the gas phase output end of the gas-liquid separation tank a is connected to the heat exchanger b, the heat exchanger b and the heat exchanger c are connected by a conveying line b, the gas-liquid separation tank b is arranged on the conveying line b, the gas phase output end of the gas-liquid separation tank b is connected to the heat exchanger c, the output end of the heat exchanger c is connected to the gas-liquid separation tank c through the conveying line c, and the gas phase output end of the gas-liquid separation tank c is connected to the tail gas pipeline.

[0010] A method for separating and purifying ammonium sulfate from electrolytic manganese slag, comprising the following steps: S1: The electrolytic manganese ammonium sulfate mixture is put into a drum high-temperature drying device to dry out the moisture at 150°C; S2: crushing and screening the dried mixture in S1 into 50 meshes through a crushing device; S3: sending the sieved mixture in S2 into an oxygen-free calcining kiln for oxygen-free calcination and decomposition; S4: The tail gas generated by the oxygen-free calcination in S3 is subjected to dust removal treatment by a three-stage electrostatic precipitator connected to the rear end of the oxygen-free calcination kiln; S5: Connect the rear end of the three-stage electrostatic precipitator described in S4 to a three-stage refrigeration separation system, wherein the first stage condenses and separates sulfuric acid, the second stage condenses and separates sulfur dioxide, and the third stage condenses and separates ammonia; S6: restoring the ammonia obtained in S5 to a gaseous state, and reacting sulfuric acid and ammonia in a certain ratio to generate ammonium sulfate and water; S7: The ammonium sulfate and water obtained in S6 are sent to an evaporation system for evaporation and crystallization to obtain an ammonium sulfate product.

[0011] As a further solution of the present invention: the mixture in S3 is fed into a calcining kiln and subjected to low-temperature calcination and decomposition at 550-700° C. for 0.2-2 hours.

[0012] As a further solution of the present invention: the boiling point of sulfur dioxide in the secondary condensation separation in S5 is -10°C, and the boiling point of ammonia is -33.5°C. The boiling point temperature difference is small, and the separated sulfur dioxide contains some ammonia. It is necessary to further separate the small amount of ammonia in the sulfur dioxide.

[0013] As a further solution of the present invention, the three-stage condensation separates the ammonia into a liquid state, a heating reactor b is set up to convert the liquid state into a gaseous state, the separated sulfur dioxide and ammonia mixed liquid is sent to the heating reactor a to restore the gaseous state, and the sulfur dioxide and ammonia mixed gas is sent to an absorption tower. The absorption tower is equipped with an alkaline absorbent, such as sodium hydroxide solution, and the sulfur dioxide reacts with the sodium hydroxide to generate sodium sulfite or sodium bisulfite and is absorbed, and the ammonia is sent back to the heating reactor b.

[0014] As a further solution of the present invention: the reaction tank sends ammonium sulfate and water to the evaporation system through the ammonium sulfate pipeline.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The system and method for separating and purifying ammonium sulfate from electrolytic manganese slag utilizes the different boiling points of gaseous sulfuric acid, sulfur dioxide, ammonia, and nitrogen in the mixed gas to condense and gradually recover them separately, and utilize the components to prepare ammonium sulfate and recover nitrogen, and separate sulfur dioxide to avoid reducing the recovery efficiency of ammonium sulfate due to the influence of sulfur dioxide.

[0016] 2. The system and method for separating and purifying ammonium sulfate from electrolytic manganese slag further recovers ammonia from sulfur dioxide condensate through an alkaline absorbent. Ammonia and sulfuric acid react in a certain proportion to generate ammonium sulfate. The recovered ammonium sulfate has a high concentration and completely separates sulfur dioxide without affecting the recovery of ammonium sulfate, thereby improving the recovery rate of ammonium sulfate, reducing water consumption, and reducing industrial water use. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is a system diagram for separating and purifying ammonium sulfate from electrolytic manganese slag.

[0018] In the figure: 1. Mixed gas pipeline; 2. Heat exchanger a; 3. Heat exchanger b; 4. Heat exchanger c; 5. Multi-stage refrigeration unit; 6. Conveying line a; 7. Conveying line b; 8. Conveying line c; 9. Tail gas pipeline; 10. Gas-liquid separation tank a; 11. Gas-liquid separation tank b; 12. Gas-liquid separation tank c; 13. Sulfuric acid pipeline; 14. Sulfur dioxide pipeline; 15. Liquid ammonia pipeline; 16. Ammonia recovery pipeline; 17. Heating reactor b; 18. Absorption tower; 19. Separation pipeline; 20. Heating reactor a; 21. Ammonia pipeline; 22. Reaction tank; 23. Ammonium sulfate pipeline; 24. Absorption liquid pipeline; 25. Dosing pipeline. DETAILED DESCRIPTION

[0019] See also Figure 1 In an embodiment of the present invention, a system for separating and purifying ammonium sulfate from electrolytic manganese slag includes a mixed gas pipeline 1, a heat exchanger a2, a heat exchanger b3, a heat exchanger c4, and a multi-stage refrigeration unit 5. The heat exchangers a2, b3, and c4 are connected in series in sequence. The multi-stage refrigeration unit 5 respectively supplies a cold medium to the heat exchangers a2, b3, and c4 for heat exchange. The mixed gas pipeline 1 is connected to the heat exchanger a2. The output ends of the heat exchangers a2, b3, and c4 are respectively provided with gas-liquid separation tanks a10, b11, and c12 to separate sulfuric acid, sulfur dioxide, and ammonia. The liquid ammonia output from the gas-liquid separation tank c12 is connected to the heating reactor b17 through the liquid ammonia pipeline 15, the sulfuric acid output from the gas-liquid separation tank a10 is connected to the reaction tank 22 through the sulfuric acid pipeline 13, and the heating reactor b17 is connected to the reaction tank 22 through the ammonia pipeline 21. The multi-stage refrigeration unit 5 is a prior art that can accurately control the refrigeration temperature by adjusting the refrigeration output at different levels to meet the temperature accuracy requirements of various processes and environments. Through multi-stage compression, the refrigerant is compressed and expanded at different pressure levels, which can be closer to the ideal refrigeration cycle, improve refrigeration efficiency, and reduce energy consumption.

[0020] In a preferred embodiment, the heat exchange temperature of heat exchanger a2 is 50-0°C, the heat exchange temperature of heat exchanger b3 is -15-35°C, and the heat exchange temperature of heat exchanger c4 is -40-50°C. Sulfuric acid has a high boiling point, and the temperature for condensing and recovering gaseous sulfuric acid can be controlled at 50-100°C. The heat exchange temperature of heat exchanger a2 is 50-0°C, which can effectively condense and recover gaseous sulfuric acid into liquid. The boiling point of sulfur dioxide is -10°C, and the full condensation of sulfur dioxide requires the heat exchange temperature of heat exchanger b3 to be controlled at -15-35°C. The boiling point of ammonia is relatively high at -33.5°C, and the full condensation of ammonia requires the heat exchange temperature of heat exchanger c4 to be maintained at -40-50°C. Nitrogen has a very low boiling point. -195.8℃, nitrogen can be used in other sections of electrolytic manganese, such as bag dust collectors, etc. During the processing of metallic manganese, there will be a need to recover metal powder. Metal powder has high chemical activity, and they have a large contact area with air, which is prone to oxidation reaction. Under certain conditions, the heat generated by the oxidation reaction accumulates, which may cause combustion or even explosion. Therefore, using recycled nitrogen to replace the air can effectively improve production safety. This application utilizes the different boiling points of gaseous sulfuric acid, sulfur dioxide, ammonia and nitrogen in the mixed gas, condenses them separately and gradually recovers them, and uses the components to prepare ammonium sulfate and nitrogen recovery, and separates sulfur dioxide to avoid reducing the recovery efficiency of ammonium sulfate due to the influence of sulfur dioxide.

[0021] In a preferred embodiment, the liquid phase output end of the gas-liquid separation tank b11 is connected to the heating reactor a20 through the sulfur dioxide pipeline 14, and the heating reactor a20 is connected to the absorption tower 18 through the separation pipeline 19. The top of the absorption tower 18 is connected to the heating reactor b17 through the ammonia recovery pipeline 16. The boiling point of ammonia is -33.5°C, and the boiling point of sulfur dioxide is -10°C. The temperature difference between the boiling points of the two is small, resulting in a small amount of ammonia condensing during the sulfur dioxide condensation process. In order to be able to recover this part of the ammonia, the present application separates by absorption method, converts liquid sulfur dioxide and ammonia into gaseous state by heating, and utilizes the difference in solubility of sulfur dioxide and ammonia in different absorbents for separation. Sulfur dioxide is an acidic gas and can react with alkaline solution, while ammonia is an alkaline gas and does not react with alkaline solution, but can be absorbed by acidic solution. When the two are passed into the alkaline absorbent, sulfur dioxide will react with sodium hydroxide to generate sodium sulfite or sodium bisulfite and be absorbed. The reaction equation is: SO2+2NaOH=Na2SO3+H2O; When there is excess sulfur dioxide; SO2+2NaOH=NaHSO3 Ammonia does not react with the sodium hydroxide solution and is discharged from the top of the absorption tower.

[0022] In a preferred embodiment, the absorption tower 18 is provided with a dosing line 25 and an absorption liquid line 24 . Alkaline absorbent, such as sodium hydroxide solution, is added through the dosing line 25 , and the reaction liquid is discharged through the absorption liquid line 24 as sodium sulfite and sodium bisulfite.

[0023] In a preferred embodiment, the heat exchanger a2 and the heat exchanger b3 are connected by a conveying line a6, the gas-liquid separation tank a10 is arranged on the conveying line a6, the liquid phase output end of the gas-liquid separation tank a10 is connected to the sulfuric acid pipeline 13, the gas phase output end of the gas-liquid separation tank a10 is connected to the heat exchanger b3, the heat exchanger b3 and the heat exchanger c4 are connected by a conveying line b7, the gas-liquid separation tank b11 is arranged on the conveying line b7, the gas phase output end of the gas-liquid separation tank b11 is connected to the heat exchanger c4, the output end of the heat exchanger c4 is connected to the gas-liquid separation tank c12 through the conveying line c8, and the gas phase output end of the gas-liquid separation tank c12 is connected to the tail gas pipeline 9.

[0024] A method for separating and purifying ammonium sulfate from electrolytic manganese slag, comprising the following steps: S1: The electrolytic manganese ammonium sulfate mixture is put into a drum high-temperature drying device to dry out the moisture at 150°C; S2: crush the dried mixture in S1 through a crushing device and sieve it to 50 mesh; S3: sending the sieved mixture of S2 into an oxygen-free calcining kiln for oxygen-free calcination and decomposition; S4: The tail gas generated by the oxygen-free calcination of S3 is subjected to dust removal treatment by a three-stage electrostatic precipitator connected to the rear end of the oxygen-free calcination kiln; S5: Connect the rear end of the S4 three-stage electrostatic precipitator to a three-stage refrigeration separation system. The first stage condenses and separates sulfuric acid, the second stage condenses and separates sulfur dioxide, and the third stage condenses and separates ammonia. S6: restoring the ammonia obtained in S5 to a gaseous state, and reacting sulfuric acid and ammonia in a certain ratio to generate ammonium sulfate and water; S7: The ammonium sulfate and water obtained in S6 are sent to an evaporation system for evaporation and crystallization to obtain an ammonium sulfate product.

[0025] In a preferred embodiment, the mixture in S3 is fed into a calcining kiln and subjected to low-temperature calcination and decomposition at 550-700° C. for 0.2-2 hours.

[0026] In a preferred embodiment, the boiling point of sulfur dioxide in the secondary condensation separation in S5 is -10°C, and the boiling point of ammonia is -33.5°C. The boiling point temperature difference is small, and the separated sulfur dioxide contains some ammonia. It is necessary to further separate the small amount of ammonia in the sulfur dioxide.

[0027] In a preferred embodiment, the ammonia is separated into liquid form by the three-stage condensation, and a heating reactor b17 is set to convert the liquid into gas form. The separated sulfur dioxide and ammonia mixed liquid is sent to the heating reactor a20 to restore the gas form, and the sulfur dioxide and ammonia mixed gas is sent to the absorption tower 18. The absorption tower 18 is equipped with an alkaline absorbent, such as sodium hydroxide solution. The sulfur dioxide will react with the sodium hydroxide to produce sodium sulfite or sodium bisulfite and be absorbed, and the ammonia is sent back to the heating reactor b17.

[0028] In a preferred embodiment, the reaction tank 22 sends ammonium sulfate and water to the evaporation system through the ammonium sulfate pipeline 23.

[0029] The ammonium sulfate recovered in this way has a high concentration and the sulfur dioxide is completely separated, which will not affect the recovery of ammonium sulfate, thereby improving the recovery rate of ammonium sulfate, reducing water consumption and reducing industrial water use.

[0030] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0031] The above-described embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A system for separating and purifying ammonium sulfate from electrolytic manganese slag, characterized in that: The invention comprises a mixed gas pipeline (1), a heat exchanger a (2), a heat exchanger b (3), a heat exchanger c (4) and a multi-stage refrigeration unit (5), wherein the heat exchanger a (2), the heat exchanger b (3) and the heat exchanger c (4) are sequentially connected in series, and the multi-stage refrigeration unit (5) respectively sends cold medium to the heat exchanger a (2), the heat exchanger b (3) and the heat exchanger c (4) for heat exchange, and the mixed gas pipeline (1) is connected to the heat exchanger a (2), the heat exchanger a (2), the heat exchanger b (3) and the heat exchanger c (4) are connected in series. The output ends are respectively provided with a gas-liquid separation tank a (10), a gas-liquid separation tank b (11) and a gas-liquid separation tank c (12), which separate sulfuric acid, sulfur dioxide and ammonia. The liquid ammonia output from the gas-liquid separation tank c (12) is connected to the heating reactor b (17) through a liquid ammonia pipeline (15). The sulfuric acid output from the gas-liquid separation tank a (10) is connected to the reaction tank (22) through a sulfuric acid pipeline (13). The heating reactor b (17) is connected to the reaction tank (22) through an ammonia pipeline (21).

2. The system for separating and purifying ammonium sulfate from electrolytic manganese slag according to claim 1, characterized in that: The heat exchange temperature of the heat exchanger a (2) is 50-0°C, the heat exchange temperature of the heat exchanger b (3) is -15--35°C, and the heat exchange temperature of the heat exchanger c (4) is -40--50°C.

3. The system for separating and purifying ammonium sulfate from electrolytic manganese slag according to claim 1 or 2, characterized in that: The liquid phase output end of the gas-liquid separation tank b (11) is connected to the heating reactor a (20) through the sulfur dioxide pipeline (14), the heating reactor a (20) is connected to the absorption tower (18) through the separation pipeline (19), and the top of the absorption tower (18) is connected to the heating reactor b (17) through the ammonia recovery pipeline (16).

4. The system for separating and purifying ammonium sulfate from electrolytic manganese slag according to claim 3, characterized in that: The absorption tower (18) is provided with a dosing pipeline (25) and an absorption liquid pipeline (24).

5. The system for separating and purifying ammonium sulfate from electrolytic manganese slag according to claim 1, characterized in that: The heat exchanger a (2) and the heat exchanger b (3) are connected via a conveying line a (6). The gas-liquid separation tank a (10) is arranged on the conveying line a (6). The liquid phase output end of the gas-liquid separation tank a (10) is connected to the sulfuric acid pipeline (13). The gas phase output end of the gas-liquid separation tank a (10) is connected to the heat exchanger b (3). The heat exchanger b (3) and the heat exchanger c (4) are connected via a conveying line b (7). The gas-liquid separation tank b (11) is arranged on the conveying line b (7). The gas phase output end of the gas-liquid separation tank b (11) is connected to the heat exchanger c (4). The output end of the heat exchanger c (4) is connected to the gas-liquid separation tank c (12) via a conveying line c (8). The gas phase output end of the gas-liquid separation tank c (12) is connected to the tail gas pipeline (9).

6. A method for separating and purifying ammonium sulfate from electrolytic manganese slag, characterized in that: The method for separating and purifying ammonium sulfate from electrolytic manganese slag using claims 1 to 5 comprises the following steps: S1: The electrolytic manganese ammonium sulfate mixture is put into a drum high-temperature drying device to dry out the moisture at 150°C; S2: crushing and screening the dried mixture in S1 into 50 meshes through a crushing device; S3: sending the sieved mixture in S2 into an oxygen-free calcining kiln for oxygen-free calcination and decomposition; S4: The tail gas generated by the oxygen-free calcination in S3 is subjected to dust removal treatment by a three-stage electrostatic precipitator connected to the rear end of the oxygen-free calcination kiln; S5: Connect the rear end of the three-stage electrostatic precipitator described in S4 to a three-stage refrigeration separation system, wherein the first stage condenses and separates sulfuric acid, the second stage condenses and separates sulfur dioxide, and the third stage condenses and separates ammonia; S6: restoring the ammonia obtained in S5 to a gaseous state, and reacting sulfuric acid and ammonia in a certain ratio to generate ammonium sulfate and water; S7: The ammonium sulfate and water obtained in S6 are sent to an evaporation system for evaporation and crystallization to obtain an ammonium sulfate product.

7. The method for separating and purifying ammonium sulfate from electrolytic manganese slag according to claim 6, wherein: The mixture in S3 is fed into a calcining kiln and subjected to low-temperature calcination and decomposition at 550-700° C. for 0.2-2 hours.

8. The method for separating and purifying ammonium sulfate from electrolytic manganese slag according to claim 6, wherein: In the secondary condensation separation in S5, the boiling point of sulfur dioxide is -10°C, and the boiling point of ammonia is -33.5°C. The boiling point temperature difference is small, and the separated sulfur dioxide contains some ammonia. It is necessary to further separate the small amount of ammonia in the sulfur dioxide.

9. The method for separating and purifying ammonium sulfate from electrolytic manganese slag according to claim 8, characterized in that: The three-stage condensation separates ammonia gas into liquid state, and a heating reactor b (17) is set to convert the liquid state into gaseous state. The separated sulfur dioxide and ammonia mixed liquid is sent to the heating reactor a (20) to restore the gaseous state. The sulfur dioxide and ammonia mixed gas is sent to the absorption tower (18). The absorption tower (18) is equipped with an alkaline absorbent, such as sodium hydroxide solution. The sulfur dioxide reacts with the sodium hydroxide to generate sodium sulfite or sodium bisulfite and is absorbed. The ammonia is sent back to the heating reactor b (17).

10. The method for separating and purifying ammonium sulfate from electrolytic manganese slag according to claim 6, characterized in that: The reaction tank (22) sends ammonium sulfate and water to the evaporation system through the ammonium sulfate pipeline (23).

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