Method for producing sodium sulfite by utilizing sulfur-containing tail gas

Abstract

The invention belongs to the technical field of preparation of sodium sulfite. The invention relates to a method for producing sodium sulfite by using sulfur-containing tail gas, which comprises the following steps: condensing the sulfur-containing tail gas after high-temperature incineration, introducing the condensed sulfur-containing tail gas into primary water absorption liquid, and filtering to obtain first mixed liquid; feeding the sulfur-containing tail gas subjected to water washing purification into secondary saturated sodium sulfite absorption liquid, and absorbing to obtain second mixed liquid; feeding sulfur-containing tail gas which is not completely absorbed into third-stage saturated sodium sulfite absorption liquid, and absorbing to obtain third mixed liquid; feeding the rest part of sulfur-containing tail gas into a fourth-stage sodium hydroxide absorption liquid to obtain a fourth mixed liquid; and adding a sodium hydroxide solution into the mixed solution, adjusting the pH value to 8-9, and directly drying and crystallizing the separated solid to obtain sodium sulfite. According to the method, no complex intermediate product is generated in the whole process, the purity of the prepared sodium sulfite is high, the technological process is simple, energy consumption is greatly reduced, and a new way is provided for comprehensive utilization and treatment of waste gas in dimethyl sulfoxide production.

Description

Technical Field

[0001] The invention relates to a method for producing sodium sulfite by utilizing sulfur-containing tail gas, and in particular to a method for preparing sodium sulfite. Background Art

[0002] In the production process of dimethyl sulfoxide, a large amount of sulfur-containing tail gas is generated, which pollutes the environment. Therefore, the treatment of sulfur-containing tail gas becomes a key problem to be solved in the production of dimethyl sulfoxide. The present invention utilizes the sulfur-containing waste gas in the factory to prepare sodium sulfite, which not only reduces environmental pollution but also realizes economic value.

[0003] At present, there are various methods for producing sodium sulfite, and the main methods for preparing anhydrous sodium sulfite include sulfur dioxide soda ash method, sulfur dioxide caustic soda method, sulfur dioxide sodium chloride method, sodium pyrosulfate method and Glauber's salt lime method, etc. Most existing technologies focus on generating high-purity sulfur dioxide by burning sulfur, and then further converting it into sodium sulfite. The potential of preparing sodium sulfite by using sulfur-containing tail gas after incineration has not been fully explored.

[0004] CN201910295068.X provides a method for producing anhydrous sodium sulfite by sulfur gasification, in which solid sulfur is melted into liquid sulfur, and the liquid sulfur is further refined after sedimentation separation; the refined sulfur enters the interior of a sulfur incinerator for combustion reaction, and high-purity sulfur dioxide flue gas is obtained, and sodium sulfite with a purity of up to 99% is obtained after absorption.

[0005] CN202410114270.9 provides a method for producing sodium sulfite, which uses quicklime, sulfur dioxide and sodium sulfate as raw materials to prepare sodium sulfite and co-produce calcium sulfate. The process steps are complicated and easy to clog equipment, and cannot meet the requirements for large-scale production of sodium sulfite.

[0006] CN202011112335.4 provides a method and system for preparing anhydrous sodium sulfite. The technology is mature, but the purity is not high. When producing sodium sulfite with higher purity, a complex purification and post-processing process is required, which has high energy consumption and high production cost, and seriously limits the large-scale and long-term application of the method.

[0007] Since the process of preparing sodium sulfite from sulfur-containing tail gas after incineration has not been fully developed, a large amount of sulfur-containing mixed tail gas will inevitably be produced in the actual production of dimethyl sulfoxide. Therefore, it is necessary to find a solution to the problem of sulfur-containing tail gas emissions while developing economically beneficial by-products. Summary of the invention

[0008] In view of this, the purpose of the present invention is to provide a method for producing sodium sulfite using sulfur-containing tail gas, which not only solves the problem of sulfur-containing tail gas emission in the existing dimethyl sulfoxide production, but also produces sodium sulfite byproduct to increase economic benefits. In order to achieve the above purpose, the embodiment of the present invention provides the following technical solutions: A method for producing sodium sulfite using sulfur-containing tail gas, the method comprising the following steps: S1: A method for producing anhydrous sodium sulfite using sulfur-containing tail gas, characterized in that the sulfur-containing tail gas after incineration is condensed and introduced into a primary water absorption liquid, and after removing impurities and layers, filtered to obtain a first mixed liquid; S2: sending the purified sulfur-containing tail gas to a secondary saturated sodium sulfite absorption liquid for absorption to obtain a second mixed liquid; S3: sending the sulfur-containing tail gas that has not been completely absorbed to the tertiary saturated sodium sulfite absorption liquid to absorb and obtain a third mixed liquid; S4: sending the remaining sulfur-containing tail gas to the fourth-stage sodium hydroxide absorption liquid to obtain a fourth mixed liquid; S5: adding 45-48% sodium hydroxide solution to the mixed solution of steps S2 and S3 to obtain a supersaturated solution with a pH of 8-9, and drying and crystallizing the precipitated solid crystals to obtain sodium sulfite with a purity of more than 97%; S6: The mother liquor obtained in step S5 is continuously used in steps S2 and S3, and the process is repeated to obtain sodium sulfite with a purity of more than 90%; S7: The mixed solution of step S4 and step S1 is treated with 15-25% sodium hydroxide solution to adjust the pH to 9.5-11, and after being treated with activated carbon and an iron remover, it is concentrated under reduced pressure to remove water until the solution concentration is 45-60%, and then evaporated and crystallized to obtain sodium sulfite with a purity of more than 90%.

[0009] The reaction principle of the present invention is as follows: SO2+H2O→H2SO3 (1) H2SO3+Na2SO3→2NaHSO3 (2) NaHSO3+NaOH→Na2SO3+H2O (3) Overall reaction: SO2+H2O+2NaOH→Na2SO3+2H2O (4) Preferably, in S1, the sulfur-containing mixed gas after high-temperature incineration includes CO2, SO2, SO3, NOx, H2O(g), O2, and N2.

[0010] Preferably, in S1, the first mixed solution, calculated as a sulfurous acid solution, has a pH value in the range of 3.0-5.0 and a temperature in the range of 0-80°C. Particularly preferably, the pH value is in the range of 4.0-5.0 and the temperature is in the range of 40-60°C. Further preferably, the pH value of the first mixed solution is 4.0; and the temperature of the mixed solution is 30°C.

[0011] Preferably, in S2, the second mixed solution is calculated as a sodium bisulfite solution, and its pH range is 4.5-5.5, and its temperature range is 30-50°C. Particularly preferably, the pH is 4.5, and the temperature range is 35-45°C.

[0012] Preferably, in S3, the third mixed solution is calculated as sodium bisulfite solution, and its pH range is 4.5-5.5, and its temperature range is 30-50°C. Particularly preferably, the pH is 4.5, and the temperature range is 35-45°C.

[0013] Preferably, in S4, the fourth mixed solution is calculated as a sodium sulfite solution, and its pH range is 9-9.5, and its temperature range is 35-50°C. Particularly preferably, the pH is 9, and the temperature range is 35-45°C.

[0014] Preferably, in S5, the mass concentration of the sodium hydroxide solution is 45-48%, the reaction temperature is 35-50°C, and the pH range is 8-9. Particularly preferably, the temperature is 40°C and the pH is 8.5-9.

[0015] Preferably, in S6, the mother liquor is used as the absorption liquid, and the absorption endpoint pH is 4.5-5.

[0016] Preferably, in S7, the concentration of sodium hydroxide is 15-25%, and the pH range is 9.5-11. Particularly preferably, the concentration of sodium hydroxide is 18-20%, and the pH range is 9.5-10.5.

[0017] Preferably, in S7, water is removed by concentration under reduced pressure until the solution concentration is 45-60%, and particularly preferably, the solution concentration is 45-55%.

[0018] Beneficial effects: The invention solves the problem that sulfur-containing mixed tail gas is difficult to treat in the production of dimethyl sulfoxide, and at the same time prepares a sodium sulfite product with a purity of 97%. Saturated sodium sulfite solution absorbs sulfur-containing mixed tail gas, and the generated sodium bisulfite solution reacts with a high-concentration sodium hydroxide solution to directly precipitate sodium sulfite crystals, and the mother liquor after filtration is recycled to generate a sodium sulfite product with a purity higher than 90%. The invention has easy-to-obtain raw materials, a simple operation process, energy saving, and high product purity. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with embodiments, but the scope of protection claimed in the patent application of the present invention is not limited to the scope described in the embodiments.

[0020] Example 1 A method for producing sodium sulfite using sulfur-containing tail gas: Absorption part: The sulfur-containing tail gas after incineration is introduced into the primary water absorption liquid, and after water washing, impurity removal and layer removal, a sulfurous acid solution with a pH of 4.0 is obtained by filtering, and the temperature of the mixed liquid is 40°C (the temperature is limited mainly to increase the solubility of sulfur dioxide in water); the pure tail gas after water washing is continuously introduced into the secondary saturated sodium sulfite solution, and a sodium bisulfite solution with a pH of 4.5 is obtained by absorption (the pH is limited mainly to determine the absorption end point, and all are converted into sodium bisulfite solution), and the temperature of the mixed liquid is between 35 and 45°C; the tail gas that has not been completely absorbed is continuously introduced into the tertiary saturated sodium sulfite solution, and a sodium bisulfite solution with a pH of 4.5 is obtained by absorption, and the temperature of the mixed liquid is between 35 and 45°C; finally, the remaining tail gas is introduced into the 18% sodium hydroxide absorption liquid, and the reaction generates a sodium sulfite solution with a pH of 9.52, and the temperature of the mixed liquid is between 35 and 45°C.

[0021] Processing part: The second and third mixed liquids are passed through 48% sodium hydroxide solution to obtain a supersaturated solution with a pH of 8.7, and the precipitated solid is directly dried and crystallized to obtain sodium sulfite with a purity of 97.5%; the mother liquor obtained by filtration is continuously recycled as an absorption liquid, and the pH at the absorption end point is 4.5, and 48% sodium hydroxide solution is passed through to obtain a supersaturated solution with a pH of 8.9, and the precipitated solid is directly dried and crystallized to obtain a sodium sulfite solution with a purity of 95.3%; the sulfurous acid solution obtained by the first-stage absorption and the sodium sulfite solution obtained by the fourth-stage absorption are continuously mixed, and 18% sodium hydroxide solution is passed through for reaction, and after iron and impurity removal and dehydration under reduced pressure to 45-55%, 95.6% sodium sulfite is obtained by evaporation and crystallization.

[0022] Example 2 This embodiment is the same as embodiment 1, except that the absorption end point pH of the absorption part is different, and the absorption temperature of each level of absorption liquid is 40°C. The sulfur-containing tail gas after incineration is introduced into the first-level water absorption liquid, and after water washing, impurity removal and layer removal, a sulfurous acid solution with a pH of 4.12 is obtained by filtration; the pure tail gas after water washing is continuously introduced into the second and third level saturated sodium sulfite solutions, and a sodium bisulfite solution with a pH of 5.0 is obtained by absorption; finally, the remaining tail gas is introduced into the 18% sodium hydroxide absorption liquid, and a sodium sulfite solution with a pH of 9.76 is generated by reaction; The treatment part is the same as Example 1. After the second and third level mixed liquors are treated, sodium sulfite with a purity of 97.6% is obtained; after the mother liquor is used as an absorption liquid and treated, sodium sulfite with a purity of 95.9% is obtained; after the first and fourth level mixed liquors are treated, sodium sulfite with a purity of 95.1% is obtained by evaporation and crystallization.

[0023] Example 3 This embodiment is the same as embodiment 1, except that the absorption end point pH of the absorption part is different. The sulfur-containing tail gas after incineration is introduced into the primary water absorption liquid, and after water washing, impurity removal and layer removal, a sulfurous acid solution with a pH of 4.52 is obtained by filtration; the pure tail gas after water washing is continuously introduced into the secondary and tertiary saturated sodium sulfite solutions to absorb and obtain a sodium bisulfite solution with a pH of 5.5; finally, the remaining tail gas is introduced into the 18% sodium hydroxide absorption liquid to react and generate a sodium sulfite solution with a pH of 9.38; The treatment part is the same as Example 1. After the second and third level mixed liquors are treated, sodium sulfite with a purity of 97.3% is obtained; after the mother liquor is used as an absorption liquid and treated, sodium sulfite with a purity of 95.2% is obtained; after the first and fourth level mixed liquors are treated, sodium sulfite with a purity of 94.5% is obtained by evaporation and crystallization.

[0024] Example 4 This embodiment is the same as embodiment 1, except that the absorption temperature of the absorption part is different, which affects the absorption effect. The sulfur-containing tail gas after incineration is introduced into the first-level water absorption liquid. After water washing, impurity removal and layer removal, the absorption liquid temperature is 80°C, and a sulfurous acid solution with a pH of 5.51 is obtained by filtration; the pure tail gas after water washing is continuously introduced into the second and third-level saturated sodium sulfite solutions, and the solution absorption temperature is 75°C, and a sodium bisulfite solution with a pH of 6.04 is obtained by absorption; finally, the remaining tail gas is introduced into the 18% sodium hydroxide absorption liquid, and the reaction generates a sodium sulfite solution with a pH of 9.38; The treatment part is the same as Example 1. After the second and third level mixed liquors are treated, sodium sulfite with a purity of 97.1% is obtained; after the mother liquor is used as an absorption liquid and treated, sodium sulfite with a purity of 95.2% is obtained; after the first and fourth level mixed liquors are treated, sodium sulfite with a purity of 93.5% is obtained by evaporation and crystallization.

[0025] Example 5 This embodiment is the same as embodiment 1, except that the absorption end point pH of the absorption part is different. The sulfur-containing tail gas after incineration is introduced into the primary water absorption liquid, and after water washing, impurity removal and layer removal, a sulfurous acid solution with a pH of 4.08 is obtained by filtration, and the temperature of the mixed liquid is 40° C. The pure tail gas after water washing is continuously introduced into the secondary and tertiary saturated sodium sulfite solutions to absorb and obtain a mixed solution with a pH of 6.5; finally, the remaining tail gas is introduced into the 18% sodium hydroxide absorption liquid to react and generate a sodium sulfite solution with a pH of 9.86; The treatment part is the same as Example 1. After the second and third level mixed liquors are treated, sodium sulfite with a purity of 90.9% is obtained; after the mother liquor is used as an absorption liquid and treated, sodium sulfite with a purity of 84.4% is obtained; after the first and fourth level mixed liquors are treated, sodium sulfite with a purity of 94.3% is obtained by evaporation and crystallization.

[0026] Example 6 This embodiment is the same as embodiment 1, except that the absorption end point pH of the absorption part is different. The sulfur-containing tail gas after incineration is introduced into the primary water absorption liquid, and after water washing, impurity removal and layer removal, a sulfurous acid solution with a pH of 4.27 is obtained by filtration, and the temperature of the mixed liquid is 40° C.; the pure tail gas after water washing is continuously introduced into the secondary and tertiary saturated sodium sulfite solutions to absorb and obtain a mixed solution with a pH of 7.0; finally, the remaining tail gas is introduced into the 18% sodium hydroxide absorption liquid to react and generate a sodium sulfite solution with a pH of 9.46; The treatment part is the same as Example 1. After the second and third level mixed liquors are treated, sodium sulfite with a purity of 87.3% is obtained; after the mother liquor is used as an absorption liquid and treated, sodium sulfite with a purity of 83.6% is obtained; after the first and fourth level mixed liquors are treated, sodium sulfite with a purity of 93.3% is obtained by evaporation and crystallization.

[0027] Example 7 This embodiment is the same as embodiment 1, except that the absorption temperature of the absorption part is different. The sulfur-containing tail gas after incineration is introduced into the primary water absorption liquid, and after water washing, impurity removal and layer removal, a sulfurous acid solution with a pH of 5.0 is obtained by filtration, and the temperature of the mixed solution is 60°C; the pure tail gas after water washing is continuously introduced into the secondary and tertiary saturated sodium sulfite solutions, and a mixed solution with a pH of 6.5 is obtained by absorption, and the temperature of the mixed solution is 55°C; finally, the remaining tail gas is introduced into the 18% sodium hydroxide absorption liquid, and the reaction generates a sodium sulfite solution with a pH of 9.55; The treatment part is the same as Example 1. After the second and third level mixed liquors are treated, sodium sulfite with a purity of 89.8% is obtained; after the mother liquor is used as an absorption liquid and treated, sodium sulfite with a purity of 84.6% is obtained; after the first and fourth level mixed liquors are treated, sodium sulfite with a purity of 90.3% is obtained by evaporation and crystallization.

Claims

1. A method for producing sodium sulfite using sulfur-containing tail gas, characterized in that: The steps include: S1: The sulfur-containing tail gas after high-temperature incineration is condensed and introduced into the primary water absorption liquid, and after impurities are removed, filtered to obtain the first mixed liquid; S2: sending the sulfur-containing tail gas after water washing and purification in step S1 to a secondary saturated sodium sulfite absorption liquid for absorption to obtain a second mixed liquid; S3: sending the sulfur-containing tail gas that has not been completely absorbed in step S2 to a tertiary saturated sodium sulfite absorption liquid for absorption to obtain a third mixed liquid; S4: sending the remaining sulfur-containing tail gas in step S3 to a fourth-stage sodium hydroxide absorption liquid to obtain a fourth mixed liquid; S5: adding sodium hydroxide solution to the mixed solution obtained by mixing steps S2 and S3, adjusting the pH value to 8-9, and directly drying and crystallizing the precipitated solid to obtain sodium sulfite with a purity of more than 97%; S6: The mother liquor obtained in step S5 is continuously used in steps S2 and S3, and the cycle is repeated to obtain sodium sulfite with a purity of more than 90%; S7: Mix the solutions of step S4 and step S1, adjust the pH to 9.5-11 with sodium hydroxide solution, treat with activated carbon and iron remover, concentrate under reduced pressure, evaporate and crystallize to obtain sodium sulfite with a purity of more than 90%.

2. A method for producing sodium sulfite using sulfur-containing tail gas according to claim 1, characterized in that: In S1, the sulfur-containing tail gas after high-temperature incineration includes CO2, SO2, SO3, NOx, H2O(g), O2, and N2.

3. A method for producing sodium sulfite using sulfur-containing tail gas according to claim 1, characterized in that: In S1, the first mixed solution is calculated as a sulfurous acid solution, and its pH range is 3.0-5.0, and its temperature range is 0-80°C. It is particularly preferred that the pH range is 4.0-5.0, and the temperature range is 30-50°C.

4. A method for producing sodium sulfite using sulfur-containing tail gas according to claim 1, characterized in that: In S2, the second mixed solution is calculated as sodium bisulfite solution, and its pH range is 4.5-5.5, and its temperature range is 30-50°C. It is particularly preferred that the pH is 4.5 and the temperature range is 35-45°C.

5. A method for producing sodium sulfite using sulfur-containing tail gas according to claim 1, characterized in that: In S3, the third mixed solution is calculated as sodium bisulfite solution, and its pH range is 4.5-5.5, and its temperature range is 30-50°C. It is particularly preferred that the pH is 4.5 and the temperature range is 35-45°C.

6. A method for producing sodium sulfite using sulfur-containing tail gas according to claim 1, characterized in that: In S4, the fourth mixed solution is calculated as a sodium sulfite solution, and its pH range is 9-9.5, and its temperature range is 35-50°C. It is particularly preferred that the pH is 9 and the temperature range is 35-45°C.

7. A method for producing sodium sulfite using sulfur-containing tail gas according to claim 1, characterized in that: In the S5, the mass concentration of the sodium hydroxide solution is 45-48%, the reaction temperature is 35-50°C, and the pH range is 8-9. It is particularly preferred that the temperature is 40°C and the pH is 8.5-9.

8. A method for producing sodium sulfite using sulfur-containing tail gas according to claim 1, characterized in that: In the S6, the mother liquor is used as the absorption liquid, and the absorption end point pH is 4.5-5.

9. A method for producing sodium sulfite using sulfur-containing tail gas according to claim 1, characterized in that: In S7, the concentration of sodium hydroxide is 15-25%, and the pH range is 9.5-11. It is particularly preferred that the concentration of sodium hydroxide is 18-20%, and the pH range is 9.5-10.

5.

10. The method for producing sodium sulfite by utilizing sulfur-containing tail gas according to claim 1, characterized in that: In the above S7, when the water is removed by concentration under reduced pressure to a solution concentration of 45-60%, it is particularly preferred that the solution concentration is 45-55%.