Device and method for recovering sodium sulfate by using p-methylphenol byproduct

Abstract

The invention belongs to the technical field of recovery of p-methylphenol by-products, and particularly relates to a device and a method for recovering sodium sulfate by utilizing the p-methylphenol by-products. Comprising a pulping tank, the pulping tank is sequentially connected with a filter, a decoloring kettle, a leaf filter, an evaporator and a centrifugal machine through pipelines, the centrifugal machine is sequentially connected with a boiling dryer and a packaging machine, the liquid phase output end of the centrifugal machine is connected with a high-whiteness mother liquor tank and a low-whiteness mother liquor tank in parallel through a pipeline, and the high-whiteness mother liquor tank is connected to the liquid inlet end of the evaporator through a pipeline. The low-whiteness mother liquor tank is connected to the pulping tank through a pipeline, and the condensate water output end of the evaporator is connected with a condensate water tank through a pipeline. According to the method, the by-product can be converted into the high-purity I-class premium-grade sodium sulfate, so that waste is turned into wealth, the treatment cost of the by-product is reduced, additional economic benefits are brought, and the profit margin of p-methylphenol is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of recovery of by-products of p-cresol, and particularly relates to a device and method for recovering sodium sulfate by using by-products of p-cresol. Background Art

[0002] At present, the domestic process for producing p-cresol is the toluene sulfonation and alkali fusion method using sulfuric acid. That is, sulfuric acid reacts with toluene to generate p-toluenesulfonic acid. The p-toluenesulfonic acid undergoes an acid-base neutralization reaction with sodium sulfite produced by alkali fusion to generate a p-toluenesulfonate solution. The sulfonate reacts with flake caustic in an alkali fusion kettle to generate p-cresol sodium and sodium sulfite. The p-cresol sodium undergoes an acidification reaction with sulfur dioxide generated by neutralization to obtain crude phenol, and then through processes such as dehydration, continuous refining, crystallization, and rectification, p-cresol is obtained.

[0003] Among them, the neutralization reaction is the acid-base neutralization reaction of p-toluenesulfonic acid with sodium sulfite produced by alkali fusion to generate a p-toluenesulfonate solution. Since p-toluenesulfonic acid contains 4-10% sulfuric acid, during the reaction, sulfuric acid reacts with sodium sulfite to generate sodium sulfate, sulfur dioxide, and water. During the drying process of the sulfonate, due to the common ion effect, a large amount of sodium sulfate precipitates. This part of sodium sulfate contains impurities such as p-toluenesulfonate, p-cresol sodium, sodium sulfite, and insolubles, seriously affecting its use.

[0004] Currently, the main methods for treating this part of sodium sulfate are as follows:

[0005] (1) During the drying process of the sulfonate, through sedimentation and centrifugation, the sodium sulfate is packaged and stored in the warehouse. This part of sodium sulfate cannot be directly used by customers because it contains phenol sodium, p-toluenesulfonate, and impurities. Currently, this part of sodium sulfate can only be disposed of as hazardous waste, and the disposal cost is high.

[0006] (2) By reducing the concentration of the sulfonate during concentration, the sodium sulfate does not precipitate and is carried into the sulfonate during the drying process, and finally is carried out by alkali fusion sodium sulfite. This process seriously affects the alkali fusion reaction during the production of p-cresol, resulting in high unit consumption of p-cresol toluene and flake caustic, and the content of sodium sulfite produced is about 75%, which cannot be processed.

[0007] How to improve the purity of sodium sulfate, reduce the sales pressure of sodium sulfate, and reduce the production cost of p-cresol is a problem that the p-cresol industry has been trying to overcome. Summary of the Invention

[0008] The purpose of the present invention is to provide a device and method for recovering sodium sulfate by using by-products of p-cresol to solve the problems existing in the prior art.

[0009] The technical solution adopted by the present invention to solve its technical problems is:

[0010] A device for recycling sodium sulfate from by-products of p-methylphenol, comprising a pulping tank, which is sequentially connected to a filter, a decolorization kettle, a leaf filter, an evaporator, and a centrifuge through pipelines. The centrifuge is sequentially connected to a fluidized bed dryer and a packaging machine. The liquid phase output pipeline of the centrifuge is connected in parallel with a high-whiteness mother liquor tank and a low-whiteness mother liquor tank. The pipeline of the high-whiteness mother liquor tank is connected to the liquid inlet end of the evaporator, and the pipeline of the low-whiteness mother liquor tank is connected to the pulping tank. The condensate output pipeline of the evaporator is connected to a condensate tank, and the pipeline of the condensate tank is connected to the pulping tank.

[0011] Further, the pulping tank is a tank with a stirrer, and a steam pipe is fixed on the pulping tank. The input pipeline of the steam pipe is connected in parallel with a recycled steam valve and a fresh steam valve. The output end of the steam pipe penetrates through the pulping tank and extends into the lower position inside the pulping tank. A pulping pump is installed on the pipeline at the output end of the pulping tank. The steam input end of the evaporator is connected in parallel with a recycled steam valve and a fresh steam valve. The recycled steam valves on the pulping tank and the evaporator are jointly connected to a recycled steam pipeline, and the fresh steam valves on the pulping tank and the evaporator are jointly connected to a fresh steam pipeline.

[0012] Further, the decolorization kettle is a tank with a stirrer and a jacket, and a carbon slurry pump is installed on the pipeline at the output end of the decolorization kettle.

[0013] Further, a receiving cart is arranged at the bottom of the solid phase output end of the leaf filter.

[0014] Further, mother liquor valves are installed on both of the two pipelines connected in parallel at the liquid phase output end of the centrifuge, and a high-whiteness mother liquor pump and a low-whiteness mother liquor pump are respectively installed on the pipelines at the output ends of the high-whiteness mother liquor tank and the low-whiteness mother liquor tank.

[0015] Further, a condensate pump is installed on the pipeline at the output end of the condensate tank, and a fresh water pipeline is communicated with the input end of the condensate tank, and a fresh water valve is installed on the fresh water pipeline.

[0016] A method for recycling sodium sulfate from by-products of p-methylphenol, comprising the following steps:

[0017] (1) Pulping: Add the by-products and water into the pulping tank according to a mass ratio of 0.2 - 0.5:1, and introduce steam through the steam pipe to raise the temperature to 45 - 100 °C to ensure that all the by-products are dissolved;

[0018] (2) Iron removal: Add liquid caustic soda or flake caustic soda to the pulping tank to adjust the pH to 8 - 13, and pump the material liquid into the filter through the pulping pump to remove insoluble substances and iron hydroxide precipitates to obtain a filtrate;

[0019] (3) Decolorization: After the filtrate is input into the decolorization kettle, sulfuric acid is added to adjust the pH to 1 - 3, and then activated carbon is added at 0.7 - 1.2% of the filtrate mass. After decolorization at 80 - 95°C for 30 minutes, the slurry is pumped into a leaf filter by a carbon slurry pump for filtration to obtain a decolorized liquid and waste carbon. The decolorized liquid is input into the circulation tank of the evaporator, and the waste carbon falls into the receiving cart at the bottom and is sent to blend coal;

[0020] (4) Concentration: After the decolorized liquid enters the evaporator, liquid caustic soda is added to adjust the pH to 7 - 8, and it is concentrated under negative pressure at -80 - -99 kPa until the solid content reaches 20 - 65% to obtain a sodium sulfate slurry;

[0021] (5) Centrifugation: The sodium sulfate slurry is centrifuged by a centrifuge to obtain sodium sulfate solids with a moisture content of 4 - 10% and mother liquor. The mother liquor with a whiteness ≥ 90% is input into a high - whiteness mother liquor tank and then recycled to the concentration step through a high - whiteness mother liquor pump. The mother liquor with a whiteness < 90% is input into a low - whiteness mother liquor tank and then recycled to the pulping step through a low - whiteness mother liquor pump;

[0022] (6) Drying: The sodium sulfate solids are dried by a fluidized - bed dryer until the water content is within 0.05% and then packaged by a packaging machine to obtain the finished product.

[0023] Furthermore, when heating by introducing steam through a steam pipe in the pulping step and during negative - pressure concentration in the concentration step, the corresponding recovered steam valve is preferably opened first to use the recovered low - pressure steam. When insufficient, the new steam valve is opened to use new steam.

[0024] Furthermore, in the pulping step, the pulping water preferably uses the steam condensate recovered in the condensate water tank. When insufficient, the new water valve is opened to use new water.

[0025] The present invention has the following beneficial effects:

[0026] 1. The present invention can convert by - products into high - purity Class I premium sodium sulfate, thus turning waste into treasure. It not only reduces the treatment cost of by - products but also brings additional economic benefits and increases the profit margin of p - cresol.

[0027] 2. Through the recycling and utilization of exhausted steam and condensate water, the recovery cost of sodium sulfate is further reduced, and the energy consumption is decreased.

[0028] 3. Blending coal with activated carbon realizes zero discharge of waste carbon and reduces the treatment cost of waste carbon.

[0029] 4. Recycling of mother liquor increases the yield of sodium sulfate. Brief Description of the Drawings

[0030] Figure 1 is the structural schematic diagram of the present invention.

[0031] Figure 2This is the process flow chart of the present invention.

[0032] Among them: 1. Pulping tank; 2. Filter; 3. Decolorization kettle; 4. Leaf filter; 5. Evaporator; 6. Centrifuge; 7. Fluidized bed dryer; 8. Packaging machine; 9. High whiteness mother liquor tank; 10. Low whiteness mother liquor tank; 11. Condensate water tank; 12. Steam pipe; 13. Recovery steam valve; 14. New steam valve; 15. Pulping pump; 16. Recovery steam pipeline; 17. New steam pipeline; 18. Carbon slurry pump; 19. Receiving truck; 20. Mother liquor valve; 21. High whiteness mother liquor pump; 22. Low whiteness mother liquor pump; 23. Condensate water pump; 24. New water pipeline; 25. New water valve. Detailed implementation manners

[0033] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Embodiment 1:

[0035] As Figure 1 shown, a device for recovering sodium sulfate by using p-methylphenol by-products includes a pulping tank 1. The pulping tank 1 is sequentially connected with a filter 2, a decolorization kettle 3, a leaf filter 4, an evaporator 5, and a centrifuge 6 through pipelines. The centrifuge 6 is sequentially connected with a fluidized bed dryer 7 and a packaging machine 8. The liquid phase output end pipeline of the centrifuge 6 is connected in parallel with a high whiteness mother liquor tank 9 and a low whiteness mother liquor tank 10. The pipeline of the high whiteness mother liquor tank 9 is connected to the liquid inlet end of the evaporator 5, and the pipeline of the low whiteness mother liquor tank 10 is connected to the pulping tank 1. The condensate water output end pipeline of the evaporator 5 is connected with a condensate water tank 11, and the pipeline of the condensate water tank 11 is connected to the pulping tank 1.

[0036] The pulping tank 1 is a tank body with a stirrer. A steam pipe 12 is fixed on the pulping tank 1. The input end pipeline of the steam pipe 12 is connected in parallel with a recovery steam valve 13 and a new steam valve 14. The output end of the steam pipe 12 penetrates through the pulping tank 1 and extends into the lower position inside the pulping tank 1. A pulping pump 15 is installed on the pipeline at the output end of the pulping tank 1. The steam input end of the evaporator 5 is connected in parallel with a recovery steam valve 13 and a new steam valve 14. The recovery steam valves 13 on the pulping tank 1 and the evaporator 5 are jointly connected with a recovery steam pipeline 16, and the new steam valves 14 on the pulping tank 1 and the evaporator 5 are jointly connected with a new steam pipeline 17. The recovery steam pipeline 16 is low-pressure steam such as exhausted steam and dry waste steam recovered in the workshop. When pulping in the pulping tank 1, supersaturated steam with a relatively high pressure is not required, so the cost can be reduced by using the recovered steam.

[0037] The decolorization kettle 3 is a tank body with a stirrer and a jacket. A carbon slurry pump 18 is installed on the pipeline at the output end of the decolorization kettle 3.

[0038] A receiving truck 19 is provided at the bottom of the solid-phase output end of the leaf filter 4.

[0039] Mother liquid valves 20 are installed on both of the two pipes connected in parallel at the liquid-phase output end of the centrifuge 6. High-white-degree mother liquid pumps 21 and low-white-degree mother liquid pumps 22 are respectively installed on the pipes at the output ends of the high-white-degree mother liquid tank 9 and the low-white-degree mother liquid tank 10.

[0040] A condensate water pump 23 is installed on the pipe at the output end of the condensate water tank 11. A new water pipeline 24 is connected to the input end of the condensate water tank 11, and a new water valve 25 is installed on the new water pipeline 24.

[0041] Embodiment 2: The method steps of this embodiment are implemented based on the structure of Embodiment 1.

[0042] As Figure 2 shown, a method for recovering sodium sulfate from p-methylphenol by-products includes the following steps:

[0043] (1) Pulping: Add 200 kg of by-products and 1 t of water into the pulping tank 1. The pulping water preferably uses the steam condensate recovered in the condensate water tank 11. When there is not enough, open the new water valve 25 to use new water. Pass steam through the steam pipe 12 to raise the temperature to 45 °C to ensure that all the by-products are dissolved. When passing steam through the steam pipe 12 to raise the temperature, preferably open the recovered steam valve 13 on the pulping tank 1 to use the recovered low-pressure steam. When there is not enough, open the new steam valve 14 to use new steam.

[0044] (2) Iron removal: Add 30% liquid alkali to the pulping tank 1 to adjust the pH to 8, so that the iron ions in the sodium sulfate form iron hydroxide precipitate. Pump the material liquid into the filter 2 through the pulping pump 15 to filter out insoluble substances and iron hydroxide precipitate to obtain a filtrate.

[0045] (3) Decolorization: After the filtrate is input into the decolorization kettle 3, add sulfuric acid to adjust the pH to 3, so that sodium sulfite in the filtrate is converted into sodium sulfate, p-toluenesulfonate is converted into p-toluenesulfonic acid, and p-methylphenolate is converted into p-methylphenol. Then add activated carbon according to 1.2% of the filtrate quality, decolorize at 80 °C for 30 minutes, and then pump the material liquid into the leaf filter 4 through the carbon slurry pump 18 for filtration to obtain a decolorized liquid and waste carbon. The decolorized liquid is input into the circulation tank of the evaporator 5, and the waste carbon falls into the receiving truck 19 at the bottom and is sent to the coal blending.

[0046] (4) Concentration: After the decolorized liquid enters the evaporator 5, add liquid alkali to adjust the pH to 8, and concentrate under negative pressure at -80 to -99 kPa until the solid content (the proportion of the precipitated solid in the total mass of the sodium sulfate slurry) is 20% to obtain a sodium sulfate slurry. When concentrating under negative pressure, preferably open the recovered steam valve 13 on the evaporator 5 to use the recovered low-pressure steam. When there is not enough, open the new steam valve 14 to use new steam.

[0047] (5) Centrifugation: The sodium sulfate slurry is centrifuged by a centrifuge 6 to obtain sodium sulfate solids with a moisture content of 4% and a purity of 99.8%, and the mother liquor. The mother liquor with a whiteness ≥ 90% is input into the high-whiteness mother liquor tank 9, and then recycled to the concentration step through the high-whiteness mother liquor pump 21. The mother liquor with a whiteness < 90% is input into the low-whiteness mother liquor tank 10, and then recycled to the pulping step through the low-whiteness mother liquor pump 22.

[0048] (6) Drying: The sodium sulfate solids are dried by a fluidized bed dryer 7 to a moisture content within 0.05%, and then packaged by a packaging machine 8 to obtain the finished product.

[0049] Example 3: The method steps of this example are implemented based on the structure of Example 1.

[0050] As Figure 2 shown, a method for recovering sodium sulfate from p-cresol by-products includes the following steps:

[0051] (1) Pulping: 500 kg of by-products and 1 t of water are added to the pulping tank 1. The pulping water preferably uses the steam condensate recovered in the condensate tank 11. When insufficient, the new water valve 25 is opened to use new water. Steam is introduced through the steam pipe 12 to raise the temperature to 100 °C to ensure that all by-products are dissolved. When introducing steam through the steam pipe 12 to raise the temperature, the recovered low-pressure steam valve 13 on the pulping tank 1 is preferably opened first to use the recovered low-pressure steam. When insufficient, the new steam valve 14 is opened to use new steam.

[0052] (2) Iron removal: 30% liquid alkali is added to the pulping tank 1 to adjust the pH to 13, so that the iron ions in sodium sulfate form iron hydroxide precipitation. The slurry is pumped into the filter 2 by the pulping pump 15 to remove insoluble substances and iron hydroxide precipitation, and the filtrate is obtained.

[0053] (3) Decolorization: After the filtrate is input into the decolorization kettle 3, sulfuric acid is added to adjust the pH to 1, so that sodium sulfite in the filtrate is converted into sodium sulfate, p-toluenesulfonate is converted into p-toluenesulfonic acid, and p-cresol sodium is converted into p-cresol. Then, activated carbon is added according to 0.7% of the filtrate mass, and after decolorization at 95 °C for 30 minutes, the slurry is pumped into the leaf filter 4 by the carbon slurry pump 18 for filtration to obtain the decolorized liquid and waste carbon. The decolorized liquid is input into the circulation tank of the evaporator 5, and the waste carbon falls into the receiving truck 19 at the bottom and is sent to mix with coal.

[0054] (4) Concentration: After the decolorized liquid enters the evaporator 5, liquid alkali is added to adjust the pH to 7, and it is negatively concentrated at -80 to -99 kPa to a solid content (the proportion of the precipitated solid in the total mass of the sodium sulfate slurry) of 65% to obtain the sodium sulfate slurry. When negatively concentrating, the recovered low-pressure steam valve 13 on the evaporator 5 is preferably opened first to use the recovered low-pressure steam. When insufficient, the new steam valve 14 is opened to use new steam.

[0055] (5) Centrifugation: The sodium sulfate slurry is centrifuged by a centrifuge 6 to obtain sodium sulfate solids with a water content of 10% and a purity of 99.6%, and the mother liquor. The mother liquor with a whiteness ≥ 90% is input into the high-whiteness mother liquor tank 9, and then recycled to the concentration step through the high-whiteness mother liquor pump 21. The mother liquor with a whiteness < 90% is input into the low-whiteness mother liquor tank 10, and then recycled to the pulping step through the low-whiteness mother liquor pump 22.

[0056] (6) Drying: The sodium sulfate solids are dried by a flash dryer 7 until the water content is within 0.05%, and then packaged by a packaging machine 8 to obtain the finished product.

[0057] Example 4: The method steps of this example are implemented based on the structure of Example 1.

[0058] As Figure 2 shown, a method for recovering sodium sulfate from p-cresol by-products includes the following steps:

[0059] (1) Pulping: 300 kg of by-products and 1 t of water are added to the pulping tank 1. The pulping water preferably uses the steam condensate recovered in the condensate tank 11, and when insufficient, the new water valve 25 is opened to use new water. Steam is introduced through the steam pipe 12 to raise the temperature to 80 °C to ensure that all by-products are dissolved. When introducing steam through the steam pipe 12 to raise the temperature, the recovered steam valve 13 on the pulping tank 1 is preferably opened to use the recovered low-pressure steam, and when insufficient, the new steam valve 14 is opened to use new steam.

[0060] (2) Iron removal: 30% liquid caustic soda is added to the pulping tank 1 to adjust the pH to 10, so that the iron ions in sodium sulfate form iron hydroxide precipitate. The slurry is pumped into the filter 2 by the pulping pump 15 to remove insoluble substances and iron hydroxide precipitate, and the filtrate is obtained.

[0061] (3) Decolorization: After the filtrate is input into the decolorization kettle 3, sulfuric acid is added to adjust the pH to 2, so that sodium sulfite in the filtrate is converted into sodium sulfate, p-toluenesulfonate is converted into p-toluenesulfonic acid, and p-cresol sodium is converted into p-cresol. Then, activated carbon is added according to 1% of the filtrate quality, and after decolorization at 80 °C for 30 minutes, the slurry is pumped into the leaf filter 4 by the carbon slurry pump 18 for filtration to obtain the decolorized liquid and waste carbon. The decolorized liquid is input into the circulation tank of the evaporator 5, and the waste carbon falls into the receiving cart 19 at the bottom and is sent to coal blending.

[0062] (4) Concentration: After the decolorized liquid enters the evaporator 5, liquid caustic soda is added to adjust the pH to 7.5, and it is negatively concentrated at -80 to -99 kPa until the solid content (the proportion of the precipitated solid in the total mass of the sodium sulfate slurry) is 55% to obtain the sodium sulfate slurry. When negatively concentrating, the recovered steam valve 13 on the evaporator 5 is preferably opened to use the recovered low-pressure steam, and when insufficient, the new steam valve 14 is opened to use new steam.

[0063] (5) Centrifugation: The sodium sulfate slurry is centrifuged by a centrifuge 6 to obtain sodium sulfate solids with a moisture content of 6% and a purity of 99.7%, and the mother liquor. The mother liquor with a whiteness ≥ 90% is input into the high-whiteness mother liquor tank 9 and then recycled to the concentration step through the high-whiteness mother liquor pump 21. The mother liquor with a whiteness < 90% is input into the low-whiteness mother liquor tank 10 and then recycled to the pulping step through the low-whiteness mother liquor pump 22.

[0064] (6) Drying: The sodium sulfate solids are dried by a flash dryer 7 to a moisture content within 0.05% and then packaged by a packaging machine 8 to obtain the finished product.

[0065] The working principle of the present invention is:

[0066] First, the by-product is dissolved, the pH is adjusted to alkaline to form iron hydroxide precipitate, which is removed by filtration. Then, the pH is adjusted to acidic with sulfuric acid to convert sodium sulfite in the filtrate into sodium sulfate, p-toluenesulfonic acid sodium into p-toluenesulfonic acid, and sodium p-methylphenoxide into p-methylphenol. Activated carbon adsorbs p-toluenesulfonic acid and p-methylphenol to improve the purity of sodium sulfate. After adjusting the pH to alkaline, sodium sulfate is precipitated by concentration, and further centrifuged and dried to obtain high-purity sodium sulfate products.

[0067] The above embodiments merely describe the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various variations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope of the present invention.

[0068] The technologies, shapes, and structures not described in detail in the present invention are all well-known technologies.

Claims

1. A device for recovering sodium sulfate from p-methylphenol byproduct, characterized in that: The invention comprises a beating tank, which is connected with a filter, a decolorizing kettle, a leaf filter, an evaporator and a centrifuge in sequence through pipelines. The centrifuge is connected with a boiling dryer and a packaging machine in sequence. The liquid phase output end pipeline of the centrifuge is connected with a high-whiteness mother liquor tank and a low-whiteness mother liquor tank in parallel. The high-whiteness mother liquor tank pipeline is connected with the liquid inlet end of the evaporator, the low-whiteness mother liquor tank pipeline is connected with the beating tank, the condensate output end pipeline of the evaporator is connected with a condensate water tank, and the condensate water tank pipeline is connected with the beating tank.

2. The device for recovering sodium sulfate from p-methylphenol byproduct according to claim 1, characterized in that: The beating tank is a tank body with an agitator, and a steam pipe is fixed on the beating tank. A recovery steam valve and a new steam valve are connected in parallel to the input end of the steam pipe. The output end of the steam pipe penetrates the beating tank and extends into the lower position inside the beating tank. A beating pump is installed on the pipe at the output end of the beating tank. A recovery steam valve and a new steam valve are connected in parallel to the steam input end of the evaporator. The recovery steam valves on the beating tank and the evaporator are commonly connected to a recovery steam pipeline, and the new steam valves on the beating tank and the evaporator are commonly connected to a new steam pipeline.

3. The device for recovering sodium sulfate from p-methylphenol byproduct according to claim 1, characterized in that: The decolorizing kettle is a tank body with a stirrer and a jacket, and a carbon slurry pump is installed on the pipeline at the output end of the decolorizing kettle.

4. The device for recovering sodium sulfate from p-methylphenol byproduct according to claim 1, characterized in that: A material receiving vehicle is arranged at the bottom of the solid phase output end of the leaf filter.

5. The device for recovering sodium sulfate from p-methylphenol byproduct according to claim 1, characterized in that: The two pipes connected in parallel at the liquid phase output end of the centrifuge are both equipped with mother liquid valves, and the pipes at the output ends of the high whiteness mother liquid tank and the low whiteness mother liquid tank are respectively equipped with a high whiteness mother liquid pump and a low whiteness mother liquid pump.

6. The device for recovering sodium sulfate from p-methylphenol byproduct according to claim 1, characterized in that: A condensate pump is installed on the pipeline at the output end of the condensate tank, and a new water pipeline is connected to the input end of the condensate tank, and a new water valve is installed on the new water pipeline.

7. A method for recovering sodium sulfate from p-methylphenol byproduct according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) beating: add the by-product and water in a mass ratio of 0.2 to 0.5:1 into a beating tank, introduce steam through a steam pipe to raise the temperature to 45 to 100° C., and ensure that all the by-products are dissolved; (2) Iron removal: Add liquid caustic soda or caustic soda flakes to the pulping tank to adjust the pH to 8-13, and use a pulping pump to pump the liquid into a filter for filtration to remove insoluble substances and iron hydroxide precipitates to obtain a filtrate; (3) Decolorization: After the filtrate is input into the decolorization kettle, sulfuric acid is added to adjust the pH to 1-3, and then activated carbon is added at 0.7-1.2% of the mass of the filtrate. After decolorization at 80-95°C for 30 minutes, the slurry is input into the leaf filter through a carbon slurry pump to obtain decolorized liquid and waste carbon. The decolorized liquid is input into the circulation tank of the evaporator, and the waste carbon falls into the receiving car at the bottom and is sent to coal blending; (4) Concentration: After the decolorized liquid enters the evaporator, liquid caustic soda is added to adjust the pH to 7-8, and concentrated under negative pressure at -80-99 kPa to a solid content of 20-65% to obtain a sodium sulfate slurry; (5) Centrifugation: The sodium sulfate slurry is centrifuged to obtain sodium sulfate solid and mother liquor with a moisture content of 4-10%. The mother liquor with a whiteness ≥90% is input to a high-whiteness mother liquor tank, and then is pumped back to the concentration step through a high-whiteness mother liquor pump. The mother liquor with a whiteness <90% is input to a low-whiteness mother liquor tank, and then is pumped back to the pulping step through a low-whiteness mother liquor pump; (6) Drying: The sodium sulfate solid is dried by a boiling dryer until the water content is within 0.05% and then packaged by a packaging machine to obtain the finished product.

8. The method for preparing high-purity sodium sulfate using p-methylphenol byproduct according to claim 7, characterized in that: When steam is introduced through the steam pipe to increase the temperature in the beating step and when negative pressure concentration is performed in the concentration step, the corresponding recovery steam valve is opened first to use the recovered low-pressure steam. If the steam is insufficient, the new steam valve is opened to use new steam.

9. The method for preparing high-purity sodium sulfate using p-methylphenol byproduct according to claim 7, characterized in that: In the beating step, steam condensate recovered from the condensate tank is preferentially used as the beating water, and when it is insufficient, a new water valve is opened to use new water.

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