Process method for extracting methanol from waste sulfuric acid

Abstract

The invention relates to the field of waste sulfuric acid recovery and regeneration, in particular to a process method for extracting methanol from waste sulfuric acid. The invention relates to a process method for extracting methanol from waste sulfuric acid, which comprises the following steps of: filtering to remove impurities, diluting, hydrolyzing and separating light components, namely condensing and recycling steam which is generated by distillation and contains the light components to obtain an organic mixture, dehydrating through a molecular sieve product to obtain a finished product methanol, and performing primary concentration to obtain industrial sulfuric acid with the concentration of 80 percent. The process not only improves the resource recovery rate of waste sulfuric acid, but also can purify and recycle methanol, has the advantages of simplicity in operation, economy and high efficiency, has a positive promotion effect on environmental protection and waste reduction, and improves the overall economic benefit of waste sulfuric acid treatment.

Description

Technical Field

[0001] The invention relates to the field of waste sulfuric acid recovery and regeneration, in particular to a process for extracting methanol from waste sulfuric acid. Background Art

[0002] With the continuous expansion of industrial scale, the amount of waste acid generated is increasing year by year. For example, in the production of organosilicon and other chemical products, the generation of waste sulfuric acid has become an unavoidable problem. This waste sulfuric acid typically contains a certain concentration of sulfuric acid and various organic compounds such as dimethyl sulfate, methanol, and dimethyl ether. The direct discharge of these components not only pollutes the environment but also wastes a large amount of valuable resources. Therefore, how to efficiently and economically recover and utilize this waste sulfuric acid has become a pressing technical challenge.

[0003] In existing technologies, waste sulfuric acid can be treated harmlessly or by recycling. Harmless treatment of waste sulfuric acid typically involves neutralization, dilution, or simple incineration, which is suitable for treating low-concentration waste sulfuric acid. However, harmless treatment of waste sulfuric acid is difficult to recycle, often resulting in high costs and environmental pollution during the treatment process.

[0004] Existing sulfuric acid recovery processes primarily concentrate waste sulfuric acid to 92.5% industrial sulfuric acid through multi-stage distillation for recycling. This presents challenges such as high process complexity, high energy consumption, and significant equipment investment. Traditional concentration processes not only require multiple evaporation and concentration steps but also rigorously controlled operating conditions to prevent sulfuric acid decomposition and loss. These factors significantly increase the cost of the recovery process, impacting overall economic efficiency. Furthermore, the organic mixture (methyl ester, methanol, dimethyl ether, etc.) separated during the sulfuric acid recovery process is typically directly combusted or used as fuel for heating equipment. This results in high recovery costs and low overall economic efficiency. Summary of the Invention

[0005] In order to solve the problem of difficulty in recovering and regenerating waste sulfuric acid in the prior art, the present invention provides a process for extracting methanol from waste sulfuric acid.

[0006] The present invention provides a process for extracting methanol from waste sulfuric acid, which is achieved through the following technical solutions: A process for extracting methanol from waste sulfuric acid, comprising the following steps: Step 1: Filtration and impurity removal: waste sulfuric acid is filtered through multiple stages to obtain primary waste sulfuric acid; Step 2: dilution: dilute the finished waste sulfuric acid with water to 40-60wt%; Step 3, hydrolysis: using low-pressure steam to heat the waste sulfuric acid diluted in step 2 to 50-90°C, and hydrolyze the impurities at 50-90°C for 0.5-4.0h; Step 4: Separation of light components: Adjust the temperature to 65-90°C, distill at 65-90°C for 0.5-2.0 hours, condense the steam containing light components produced by distillation to obtain an organic mixture, and then dehydrate it through a molecular sieve product to obtain finished methanol; Step 5: After the separation of the light components, the waste sulfuric acid is concentrated in one stage to obtain regenerated industrial sulfuric acid with a concentration of 80%.

[0007] This process not only improves the resource recovery rate of waste sulfuric acid, but also can purify and recycle methanol. It has the advantages of simple operation, economy and high efficiency, has a positive role in promoting environmental protection and waste reduction, and improves the overall economic benefits of waste sulfuric acid treatment.

[0008] Preferably, in the step 1, filtering and removing impurities: the waste sulfuric acid is sequentially passed through a 20-mesh PVDF filter, a 200-mesh PVDF filter, and an 800-mesh PVDF filter to complete three-stage filtration to obtain primary waste sulfuric acid.

[0009] Further preferably, in the step 1, filtering and removing impurities: the waste sulfuric acid is sequentially passed through a 20-mesh PVDF filter, a 200-mesh PVDF filter, an 800-mesh PVDF filter, and a PVDF ultrafiltration membrane MF to complete four-stage filtration to obtain primary waste sulfuric acid.

[0010] By adopting the above technical solution, solid particle impurities in waste sulfuric acid can be effectively removed.

[0011] Preferably, the concentration of the primary waste sulfuric acid is 70-80 wt %.

[0012] Preferably, in the step 2, dilution: the primary waste sulfuric acid is mixed with deionized water in a lightness removal tower and diluted to 40-60 wt%.

[0013] By adopting the above technical solution, if the concentration of the primary waste sulfuric acid is ≥70 wt%, it will release heat when diluted with water. The heat generated by the dilution of the waste sulfuric acid increases the temperature of the diluted waste sulfuric acid, which can reduce energy consumption.

[0014] Preferably, in step three, hydrolysis: the diluted waste sulfuric acid is sprayed downward, the diluted waste sulfuric acid is mixed with low-pressure steam for counter-heat exchange, and the temperature of the waste sulfuric acid at the bottom of the lightness removal tower is controlled to 65-80°C by controlling the pressure and flow rate of the low-pressure steam, and hydrolysis is carried out at a temperature of 65-80°C for 0.5-4.0h.

[0015] The energy required to raise the temperature of the waste sulfuric acid from room temperature to 65-80°C after completing the dilution treatment is provided by the thermal energy of low-pressure steam and the heat generated by the dilution of the waste sulfuric acid, which can reduce the energy consumption of waste sulfuric acid recovery.

[0016] Preferably, the step four is light component separation: the waste sulfuric acid at the bottom of the light component removal tower is heated and the temperature is adjusted to 65-90°C. An air valve is set at the top of the light component removal tower. The steam containing light components generated by distillation flows to the condenser through the air valve, and is condensed and recovered by the condenser to obtain an organic mixture. The organic mixture is dehydrated through a molecular sieve separator to obtain finished methanol. When the air valve is in a closed state, the waste sulfuric acid at the bottom of the light component removal tower flows into the concentration equipment.

[0017] The air valve is used to detect the methanol residue in the waste sulfuric acid at the bottom of the de-lightening tower. When the methanol in the waste sulfuric acid is completely distilled out and the air valve is in a closed state, the waste sulfuric acid at the bottom of the de-lightening tower flows into the concentration equipment. After one-stage concentration, regenerated industrial sulfuric acid with a concentration of 80% can be obtained, which can effectively improve the overall recovery efficiency and shorten the waste sulfuric acid treatment time.

[0018] By adopting the above technical solution, the hydrolysis reaction is carried out in the lightness removal tower and the methanol produced by the hydrolysis of dimethyl sulfate can be separated at the same time, thereby improving the overall recovery efficiency and shortening the waste sulfuric acid treatment time.

[0019] Preferably, the molecular sieve separator includes an input main pipe and an output main pipe connected to the condenser, the input main pipe is connected to three molecular sieve dehydration units through branch pipe A, the bottom of the molecular sieve dehydration unit is connected to the output main pipe through branch pipe B; the side wall of branch pipe A is connected to another condenser.

[0020] Preferably, the molecular sieve dehydration unit includes an outer shell made of polytetrafluoroethylene, two mesh disks of polytetrafluoroethylene spaced apart from each other are fixedly connected to the outer shell, and a molecular sieve filling cavity is formed between the mesh disks; the molecular sieve filling cavity 5003 is filled with a water adsorption layer; the water adsorption layer is a spherical 3A molecular sieve or a spherical 4A molecular sieve.

[0021] By adopting the above-mentioned molecular sieve products, methanol and water can be quickly separated. The water molecular weight is adsorbed by the molecular sieve products, and the methanol flows into the storage tank for collection, thereby improving the methanol recovery efficiency, shortening the waste sulfuric acid treatment time, and improving the overall economic benefits of waste sulfuric acid treatment.

[0022] Further preferably, the water adsorption layer is a spherical AA molecular sieve; and Teflon heating wires are connected between adjacent mesh plates.

[0023] The saturated water adsorption layer can be analyzed by the Teflon heating wire to regenerate the water adsorption layer, which is convenient for efficiently removing water from methanol and reducing the cost of methanol extraction.

[0024] In summary, the present invention has the following advantages: 1. The process of the present invention not only improves the resource recovery rate of waste sulfuric acid, but also can purify and recycle methanol, thereby improving the overall economic benefits of waste sulfuric acid treatment.

[0025] 2. The process of the present invention only requires one-level concentration to obtain regenerated industrial sulfuric acid that meets national standards, reduces energy consumption, and has a positive promoting effect on environmental protection and waste reduction.

[0026] 3. The process of the present invention has the advantages of simple operation, economy and high efficiency.

[0027] 4. The process of the present invention utilizes the energy generated by the exothermic dilution of waste sulfuric acid, and only low-pressure steam is needed to promote the decomposition of dimethyl sulfate, which has low energy consumption, less process difficulty, reduces production, and improves the overall economic benefits of waste sulfuric acid treatment.

[0028] 5. The process of the present invention achieves zero waste discharge, significantly reduces environmental pollution, and fully recovers small organic molecules in waste sulfuric acid, with high resource utilization, which helps to achieve sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a process flow chart of extracting methanol from waste sulfuric acid.

[0030] Figure 2 It is a structural schematic diagram of the production system for extracting methanol from waste sulfuric acid in the present invention.

[0031] Figure 3 It is a schematic diagram of the structure of the molecular sieve separator used in extracting methanol from waste sulfuric acid.

[0032] Figure 4 This is a schematic diagram of the structure of the molecular sieve dehydration unit in extracting methanol from waste sulfuric acid.

[0033] Figure 5 It is a schematic diagram of the structure of the light removal tower in extracting methanol from waste sulfuric acid.

[0034] In the figure, 1. waste sulfuric acid storage tank; 10. primary filter; 2. filter assembly; 21. primary filter; 22. secondary filter; 23. tertiary filter; 24. quaternary filter; 3. lightness removal tower; 30. air valve; 31. heat exchange steel pipe; 32. porous spray plate; 321. air outlet; 322. receiving cavity; 33. low-pressure steam spray plate; 4. condenser A; 5. molecular sieve separator; 500. molecular sieve dehydration unit; 5001. outer shell; 5002. mesh plate; 500 3. Molecular sieve filling cavity; 50004. Water adsorption layer; 5005. Teflon heating wire 5005; 501. Input main pipe; 502. Output main pipe; 503. Branch pipe A; 504. Branch pipe B; 51. Detection kettle; 52. Unqualified methanol storage tank; 53. Qualified methanol storage tank; 6. Primary evaporation chamber; 61. Condenser B; 62. Condensate storage tank; 63. Heater; 64. Delivery pump; 65. Sulfuric acid concentration detection instrument; 7. Regenerated industrial sulfuric acid storage tank; 8. Siloxane recovery tank. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0036] Reference Figure 1 A process for extracting methanol from waste sulfuric acid comprises the following steps: Step 1: Filtration and impurity removal: The waste sulfuric acid is filtered through multiple stages to obtain finished waste sulfuric acid. Specifically, the waste sulfuric acid is filtered through a 20-mesh PVDF filter, a 200-mesh PVDF filter, an 800-mesh PVDF filter, and a PVDF ultrafiltration membrane MF in sequence to obtain a primary waste sulfuric acid. The concentration of the primary waste sulfuric acid is 70-80 wt%. Step 2: dilution: the primary waste sulfuric acid is mixed with deionized water in the light removal tower and diluted to 40-60wt%. The preferred concentration of the diluted waste sulfuric acid is 50wt%. Step 3, hydrolysis: using low-pressure steam to heat the waste sulfuric acid that has been diluted in step 2 to 50-90° C., and hydrolyzing the impurities at 50-90° C. for 0.5-4.0 hours; preferably, hydrolysis: spraying the diluted waste sulfuric acid downward, spraying the diluted waste sulfuric acid downward and mixing it with the low-pressure steam for counter-heat exchange, controlling the temperature of the waste sulfuric acid at the bottom of the lightness removal tower to 65-80° C. by controlling the pressure and flow rate of the low-pressure steam, and performing hydrolysis at 65-80° C. for 0.5-4.0 hours; Step 4: Separating light components: heating the waste sulfuric acid at the bottom of the light removal tower, adjusting the temperature to 65-90°C, and distilling at 65-90°C for 0.5-2.0h. The steam containing light components produced by the distillation is condensed and recovered to obtain an organic mixture, which is then dehydrated in a molecular sieve separator to obtain finished methanol. After 2.0h of distillation, sampling is performed to detect the methanol content in the waste sulfuric acid. When the methanol content is lower than 0.05%, the waste sulfuric acid at the bottom of the light removal tower flows into the concentration equipment. Otherwise, the distillation is continued for 30min and the methanol content is measured. If the methanol content is higher than 0.05%, the distillation is continued for 30min and the methanol content is measured again until the methanol content is lower than 0.05%. Step 5: The waste sulfuric acid flowing into the concentration equipment undergoes a first-stage concentration to obtain regenerated industrial sulfuric acid with a concentration of 80%.

[0037] Reference Figure 2 The process for extracting methanol from waste sulfuric acid relies on a corresponding production system for extracting methanol from waste sulfuric acid. The production system for extracting methanol from waste sulfuric acid includes a waste sulfuric acid storage tank 1, which is connected to a filter assembly 2 via a pipeline. One end of the filter assembly 2 is connected to the waste sulfuric acid storage tank 1 and the other end is connected to a de-lightening tower 3. The liquid outlet of the filter assembly 2 is connected to the upper sidewall of the de-lightening tower 3. The top of the de-lightening tower 3 is connected to a condenser A4 via a pipeline. An air valve 30 is installed on the pipeline between the de-lightening tower 3 and the condenser A4. The air valve 30 is installed on the top of the de-lightening tower 3. One end of the condenser A4 is connected to the top of the de-lightening tower 3 and the other end is connected to a molecular sieve separator 5. The inlet of the molecular sieve separator 5 is connected to the condenser A4 and the other end is connected to a detection kettle 51 via a pipeline. The detection kettle 51 is connected to a methanol concentration detector 52. The bottom of the detection kettle 51 is connected to a storage tank 52 for unqualified methanol and a storage tank 53 for qualified methanol via pipelines. The unqualified methanol storage tank 52 is connected to the inlet of the molecular sieve separator 5 through a pipeline, and the methanol with substandard purity in the unqualified methanol storage tank 52 is subjected to secondary dehydration treatment until the moisture content of the recovered methanol is lower than 0.5% and then stored in the qualified methanol storage tank 53.

[0038] Reference Figure 2 In order to prevent large particles of impurities from clogging the pipeline, the liquid inlet port of the waste sulfuric acid storage tank 1 is connected to a primary filter 10, and the primary filter 10 is filled with a 10-mesh PVDF filter screen.

[0039] Reference Figure 2The filter assembly 2 includes a primary filter 21, a secondary filter 22, a tertiary filter 23, and a quaternary filter 24. The primary filter 21 is filled with a 20-mesh PVDF filter screen. The secondary filter 22 is filled with a 200-mesh PVDF filter screen. The secondary filter 22 is filled with a 200-mesh PVDF filter screen. The tertiary filter 23 is filled with an 800-mesh PVDF filter screen. The quaternary filter 24 is filled with a PVDF ultrafiltration membrane MF. One end of the primary filter 21 is connected to the waste sulfuric acid storage tank 1 and the other end is connected to the secondary filter 22. One end of the secondary filter 22 is connected to the primary filter 21 and the other end is connected to the tertiary filter 23. One end of the tertiary filter 23 is connected to the secondary filter 22 and the other end is connected to the quaternary filter 24. A delivery pump is installed on the pipeline between the primary filter 21 and the secondary filter 22, a delivery pump is installed on the pipeline between the secondary filter 22 and the tertiary filter 23, and a delivery pump is installed on the pipeline between the tertiary filter 23 and the quaternary filter 24, which can pressurize the waste sulfuric acid and improve the filtration quality and filtration efficiency.

[0040] Reference Figure 2 and Figure 3 The molecular sieve separator 5 includes an input main pipe 501 connected to condenser A4 and an output main pipe 502 connected to the detection kettle 51. The input main pipe 501 is connected to three molecular sieve dehydration units 500 via branch pipes A503. The bottom of the molecular sieve dehydration unit 500 is connected to the input and output main pipes 502 via branch pipes B504. The sidewall of branch pipe 503 is connected to condenser B61. The unqualified methanol storage tank 52 is connected to the input main pipe 501 in the molecular sieve separator 5 via a pipeline.

[0041] Reference Figure 3 and Figure 4 The molecular sieve dehydration unit 50 comprises a polytetrafluoroethylene outer shell 5001. Two spaced-apart polytetrafluoroethylene mesh disks 5002 are fixedly attached to the outer shell 5001. A molecular sieve-filled cavity 5003 is formed between the mesh disks 5002. The molecular sieve-filled cavity 5003 is filled with a water adsorption layer 5004, which is a spherical 3A molecular sieve or a spherical 4A molecular sieve group. Teflon heating wires 5005 are connected between adjacent mesh disks 5002. These heat and decompose the water adsorption layer, generating steam that flows to condenser B61. The recovered distilled water is stored in condensate tank 62.

[0042] Reference Figure 2 and Figure 5A heat exchange steel pipe 31 is fixedly connected to the de-lightening tower 3, and the heat exchange steel pipe 31 is spirally fixed to the inner wall of the de-lightening tower 3. One end of the heat exchange steel pipe 31 is connected to the liquid outlet of the filter assembly 2 through a pipe, and one end of the connecting pipe between the liquid outlet of the filter assembly 2 and the heat exchange steel pipe 31 is located outside the de-lightening tower 3 and connected to the filter assembly 2, and the other end is located inside the de-lightening tower 3 and connected to the heat exchange steel pipe 31. The connection position between the heat exchange steel pipe 31 and the connecting pipe inside the de-lightening tower 3 is the liquid inlet port at the bottom of the heat exchange steel pipe 31. The top liquid outlet port of the heat exchange steel pipe 31 is connected to a porous spray plate 32 through a pipe. The porous spray plate 32 is formed with an air outlet 321 for steam circulation. A accommodating cavity 322 connected to the heat exchange steel pipe 31 is formed in the porous spray plate 32, and the spray head on the porous spray plate 32 is connected to the accommodating cavity 322. A low-pressure steam spray pan 33 is fixedly connected to the de-light tower 3 and is located between the porous spray pan 32 and the heat exchange steel pipe 31. The steam outlet of the low-pressure steam spray pan 33 is vertically upward, and the spray head on the porous spray pan 32 is vertically downward. The sprayed waste sulfuric acid and the low-pressure steam undergo convection heat exchange, which can effectively improve the heat exchange effect and cause a partial hydrolysis reaction of dimethyl sulfate, thereby increasing the recovery and regeneration efficiency of the waste sulfuric acid.

[0043] Reference Figure 2 The sidewalls of the light-removal tower 3 are connected to a primary evaporation chamber 6 via a pipe. The top of the primary evaporation chamber 6 is connected to a condenser B61 via a pipe. One end of the condenser B61 is connected to the top of the primary evaporation chamber 6, and the other end is connected to a condensate storage tank 62 via a pipe. The bottom of the primary evaporation chamber 6 is connected to a heater 63 via a pipe, and the bottom of the primary evaporation chamber 6 is also connected to the bottom of the heater 63 via a pipe. A transfer pump 64 is installed in the pipe between the bottom of the primary evaporation chamber 6 and the bottom of the heater 63. Specifically, the middle sidewall of the primary evaporation chamber 6 is connected to the top sidewall of the heater 63 via a pipe. Specifically, the hydrolyzed waste sulfuric acid in the primary evaporation chamber 6 is pumped from the bottom into the bottom of the heater 63, passes through the heater 63 from bottom to top, and then flows from the top sidewall of the heater 63 into the middle sidewall of the primary evaporation chamber 6. After circulating heating, the water in the waste sulfuric acid vaporizes and flows to the condenser B61. The condensed water in the condenser B61 is collected in the condensate storage tank 62. The bottom sidewall of the primary evaporation chamber 61 is connected to a sulfuric acid concentration detector 65, specifically a sulfuric acid concentration meter. The bottom sidewall of the primary evaporation chamber 6 is connected to a regenerated industrial sulfuric acid storage tank 7 via a pipe. When the sulfuric acid concentration detector 65 detects that the regenerated sulfuric acid concentration in the primary evaporation chamber 6I is 80.0±0.2%, the heater 63 stops operating, and the qualified regenerated industrial sulfuric acid in the primary evaporation chamber 6 flows to the regenerated industrial sulfuric acid storage tank 7 for storage. The bottom of the light removal tower 3 is connected to a siloxane recovery tank 8 via a pipe to collect siloxane separated from the waste sulfuric acid and located at the bottom.

[0044] The specific implementation plan is as follows: Reference Figure 2A process for extracting methanol from waste sulfuric acid comprises the following steps: The organic silicon waste sulfuric acid (the sulfuric acid concentration in the organic silicon waste sulfuric acid is 70-80wt%) transported by tank truck is first filtered through the primary filter 10, that is, filtered through a 10-mesh PVDF filter and input into the waste sulfuric acid storage tank 1 for storage as the waste sulfuric acid to be recovered; Step 1, filtering and removing impurities: the waste sulfuric acid to be recovered stored in the waste sulfuric acid storage tank 1 is sequentially passed through the primary filter 21, the secondary filter 22, the tertiary filter 23, and the quaternary filter 24 by a delivery pump, that is, the waste sulfuric acid to be recovered is sequentially passed through a 20-mesh PVDF filter, a 200-mesh PVDF filter, an 800-mesh PVDF filter, and a PVDF ultrafiltration membrane MF under the transmission of the delivery pump. After the four-stage filtration of the filter component 2, impurities with a particle size of ≥10µm are effectively removed to obtain primary waste sulfuric acid; Step 2: Dilution: Use a sulfuric acid concentration meter to test the sulfuric acid content in the primary waste sulfuric acid to find that it is X%. The flow rate of the primary waste sulfuric acid per unit time is a / m 3 , the flow rate of deionized water per unit time is b / m 3 In the light removal tower 3, the primary waste sulfuric acid is mixed with deionized water and diluted to Y wt%, Y is 40-60wt%, and the flow rate of deionized water per unit time is [(XY)*a / Y] / m 3 The preferred concentration Y of diluted waste sulfuric acid is 50wt%, and the flow rate of deionized water per unit time is [2X-1*a] / m 3 ; Step three, hydrolysis: the waste sulfuric acid that has completed the dilution treatment flows to the spray plate 32 through the heat exchange steel pipe 31, and the waste sulfuric acid in the spray plate 32 is sprayed downward under the action of the spray head. The steam port of the low-pressure steam spray plate 33 is vertically upward, and the diluted waste sulfuric acid is sprayed downward to perform counter-heat exchange mixing with the low-pressure steam. By controlling the pressure and flow rate of the low-pressure steam, the temperature of the waste sulfuric acid at the bottom of the de-light tower 3 is controlled to be 65-80°C, and hydrolysis is carried out at a temperature of 65-80°C for 0.5-4.0h. Preferably, the temperature of the waste sulfuric acid at the bottom of the de-light tower is controlled to be 70°C, and the liquid level of the waste sulfuric acid at the bottom of the de-light tower 3 reaches 1 / 3 of the volume of the de-light tower 3, and the addition of primary waste sulfuric acid and deionized water to the de-light tower 3 is stopped, and the low-pressure steam input to the low-pressure steam spray plate 33 is also stopped; Step 4, separation of light components: low-pressure steam is input into the jacket layer of the light component removal tower 3 to heat the waste sulfuric acid at the bottom of the light component removal tower, and the temperature is adjusted to 65-90°C, preferably 70-75°C. The steam containing light components produced by distillation at 70-75°C flows to the condenser A4 through the air valve 30, and the organic mixture is condensed and recovered through the condenser A4. The organic mixture is dehydrated through the molecular sieve separator 5 and then flows into the detection kettle 51. The methanol concentration detector 52 in the detection kettle 51 detects the methanol concentration. The water content in the methanol is less than 0.5% and flows into the qualified methanol storage tank 53 to obtain the finished methanol. Alcohol, the water content in methanol is higher than 0.5% and flows into the unqualified methanol storage tank 52, the unqualified methanol storage tank 52 is pumped into the molecular sieve separator 5, that is, the methanol with substandard purity in the unqualified methanol storage tank 52 is subjected to secondary dehydration treatment until the water content in the recovered methanol is lower than 0.5% and then stored in the qualified methanol storage tank 53 to obtain finished methanol. When the air valve 30 is in a closed state, the low-boiling point organic matter can no longer be distilled out of the waste sulfuric acid at the bottom of the light removal tower 3, the waste sulfuric acid and siloxane at the bottom of the light removal tower 3 are separated, and the siloxane is pumped into the siloxane recovery tank 8 for storage and recovery. The waste sulfuric acid after removing the siloxane is pumped into the primary evaporation chamber 6; In step 5, the waste sulfuric acid flowing into the concentration equipment undergoes primary concentration: after the waste sulfuric acid in the primary evaporation chamber 6 is circulated and heated by the heater 63, the water in the waste sulfuric acid is vaporized and flows to the condenser B61. The condensed water in the condenser B61 is collected in the condensed water storage tank 62. The sulfuric acid concentration is detected by the sulfuric acid concentration detection instrument 65. When the sulfuric acid concentration detection instrument 65 shows that the sulfuric acid concentration is 80%, the delivery pump 64 is turned off, the heater 63 stops heating, and the regenerated industrial sulfuric acid that has completed the primary concentration in the primary evaporation chamber 6 is stored in the regenerated industrial sulfuric acid storage tank 7.

[0045] In summary, this process not only improves the resource recovery rate of waste sulfuric acid, but also can purify and recycle methanol. It has the advantages of simple operation, economy and high efficiency, and has a positive role in promoting environmental protection and waste reduction, and improves the overall economic benefits of waste sulfuric acid treatment.

[0046] The embodiments of this specific implementation method are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for extracting methanol from waste sulfuric acid, characterized in that: Here are the steps: Step 1: Filtration and impurity removal: waste sulfuric acid is filtered through multiple stages to obtain primary waste sulfuric acid; Step 2: dilution: dilute the primary waste sulfuric acid with water to 40-60wt%; Step 3, hydrolysis: using low-pressure steam to heat the waste sulfuric acid diluted in step 2 to 50-90°C, and hydrolyze the impurities at 50-90°C for 0.5-4.0h; Step 4: Separation of light components: Adjust the temperature to 65-90°C, distill at 65-90°C for 0.5-2.0 hours, condense the steam containing light components produced by distillation to obtain an organic mixture, and then dehydrate it through a molecular sieve product to obtain finished methanol; Step 5: After the separation of the light components, the waste sulfuric acid is concentrated in one stage to obtain regenerated industrial sulfuric acid with a concentration of 80%.

2. The process for extracting methanol from waste sulfuric acid according to claim 1, wherein: The first step is filtering and removing impurities: the waste sulfuric acid is sequentially passed through a 20-mesh PVDF filter, a 200-mesh PVDF filter, an 800-mesh PVDF filter, and a PVDF ultrafiltration membrane MF to complete four-stage filtration to obtain the primary waste sulfuric acid.

3. The process for extracting methanol from waste sulfuric acid according to claim 2, wherein: The concentration of the primary waste sulfuric acid is 70-80 wt %.

4. The process for extracting methanol from waste sulfuric acid according to claim 3, wherein: The second step is dilution: the primary waste sulfuric acid is mixed with deionized water in a lightness removal tower and diluted to 40-60 wt%.

5. The process for extracting methanol from waste sulfuric acid according to claim 4, wherein: The step three is hydrolysis: the waste sulfuric acid after the dilution treatment is sprayed downward, and the diluted waste sulfuric acid is mixed with low-pressure steam by counter-heat exchange. By controlling the pressure and flow rate of the low-pressure steam, the temperature of the waste sulfuric acid at the bottom of the lightness removal tower is controlled to 65-80° C., and hydrolysis is carried out at a temperature of 65-80° C. for 0.5-4.0 hours.

6. The process for extracting methanol from waste sulfuric acid according to claim 4, wherein: The fourth step is light component separation: the waste sulfuric acid at the bottom of the light component removal tower is heated and the temperature is adjusted to 65-90°C. An air valve is set at the top of the light component removal tower. The steam containing light components produced by distillation flows to the condenser through the air valve. The organic mixture is condensed and recovered by the condenser. The organic mixture is dehydrated by the molecular sieve separator (5) to obtain the finished methanol. When the air valve is in a closed state, the waste sulfuric acid at the bottom of the light component removal tower flows into the concentration equipment.

7. The process for extracting methanol from waste sulfuric acid according to claim 6, wherein: The molecular sieve separator (5) comprises an input main pipe (501) and an output main pipe (502) connected to a condenser. The input main pipe (501) is connected to three molecular sieve dehydration units (500) respectively through a branch pipe A (503). The bottom of the molecular sieve dehydration unit (500) is connected to the output main pipe (502) through a branch pipe B (504). The side wall of the branch pipe A (503) is connected to another condenser.

8. The process for extracting methanol from waste sulfuric acid according to claim 6, wherein: The molecular sieve dehydration unit (500) comprises an outer shell (5001) made of polytetrafluoroethylene, wherein two mesh disks (5002) spaced apart from each other and made of polytetrafluoroethylene are fixedly connected to the outer shell (5001), and a molecular sieve filling cavity (5003) is formed between the mesh disks (5002); the molecular sieve filling cavity (5003) is filled with a water adsorption layer (5004); the water adsorption layer (5004) is a spherical 3A molecular sieve or a spherical 4A molecular sieve.

9. The process for extracting methanol from waste sulfuric acid according to claim 7, wherein: The water adsorption layer (5004) is a spherical AA molecular sieve; Teflon heating wires (5005) are connected between adjacent mesh plates (5002).

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