Waste acid recovery method in sulfonated para-ester production process

Abstract

The invention provides a waste acid recovery method in a sulfonated para-ester production process. Comprising the following steps that 1, a waste acid solution is pretreated, solid particles and part of organic matter in the waste acid solution are removed, the solid particles comprise tar-shaped substances, unreacted sulfonation raw materials and carbides, and part of the organic matter comprises sulfonation decomposition products, sulfonation intermediates and polyaromatic hydrocarbons; step 2, introducing the pretreated waste acid solution into a triple-effect evaporation system for waste acid concentration, and increasing the acid concentration in the waste acid solution to 85-90%; step 3, carrying out tributyl phosphate-kerosene system extraction on the concentrated waste acid solution, and removing residual organic matters; step 4, carrying out ion exchange on the extracted waste acid solution to remove metal ions; and 5, carrying out vacuum crystallization on the waste acid solution obtained in the step 4 to obtain concentrated sulfuric acid with the concentration of more than or equal to 92.5% and the purity of more than or equal to 98%. The waste acid recovery method provided by the invention is efficient, environment-friendly and low in energy consumption, and has remarkable economic and social benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of waste acid recovery from sulfonated para - ester, and specifically to a method for recovering waste acid during the production process of sulfonated para - ester. Background Art

[0002] Sulfonated para - ester is an important class of chemical intermediates, widely used in fields such as dyes, pharmaceuticals, pesticides, and polymer materials. Its production process usually uses para - ester as the raw material and conducts sulfonation reactions under the catalysis of concentrated sulfuric acid or fuming sulfuric acid. However, a large amount of waste acid is generated during the sulfonation reaction, and its main components include unreacted sulfuric acid, unreacted raw materials, sulfonation intermediates, tar - like organic impurities, or metal ions such as iron and chromium. If these waste acids are directly discharged, it will not only cause serious environmental pollution but also lead to waste of sulfuric acid resources. Therefore, developing an efficient and low - energy - consumption waste acid recovery process has important economic and environmental significance.

[0003] Currently, the commonly used waste acid recovery methods in industry mainly include concentration methods, extraction methods, membrane separation methods, and neutralization methods, etc. If the above - mentioned methods are used to directly recover waste acid, they all have certain limitations. In addition, the composition of waste acid during the production process of sulfonated para - ester is complex. Especially the presence of tar - like substances and metal ions further increases the difficulty of recovery. Tar - like substances are likely to block equipment pipelines and affect the stability of the recovery process; metal ions may reduce the concentration of the recovered sulfuric acid and limit its recovery range. Therefore, the existing waste acid recovery technologies often face problems such as high energy consumption, low recovery rate, and serious equipment corrosion in practical applications, and it is difficult to meet the needs of industrial production. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] In view of the deficiencies of the prior art, the present invention provides a method for recovering waste acid during the production process of sulfonated para - ester, and solves the problems raised in the above - mentioned background art.

[0006] (2) Technical Solutions

[0007] To achieve the above - mentioned objectives, the present invention is realized through the following technical solutions:

[0008] According to the first aspect of the present invention, there is provided a method for recovering waste acid during the production process of sulfonated para - ester, including the following steps:

[0009] Step 1: Pretreat the waste acid solution to remove solid particles and some organic substances in the waste acid solution, where the solid particles include tar - like substances, unreacted sulfonation raw materials, and carbides, and the some organic substances include sulfonation decomposition products, sulfonation intermediates, and poly - aromatic hydrocarbons;

[0010] Step 2: Feed the waste acid solution pretreated in Step 1 into a triple-effect evaporation system for waste acid concentration to increase the acid concentration in the waste acid solution to 85-90%;

[0011] Step 3: Extract the waste acid solution concentrated in Step 2 with a tributyl phosphate-kerosene system to remove residual organic substances;

[0012] Step 4: Perform ion exchange on the waste acid solution extracted in Step 3 to remove metal ions;

[0013] Step 5: Perform vacuum crystallization on the waste acid solution in Step 4 to obtain concentrated sulfuric acid with a concentration ≥ 92.5% and a purity ≥ 98%.

[0014] Preferably, in Step 1, the pretreatment includes mechanical filtration and adsorption treatment;

[0015] The mechanical filtration uses an acid-resistant ceramic membrane filter with a pore size of 1-5 μm;

[0016] The adsorption treatment uses activated carbon to adsorb the waste acid solution.

[0017] During the pretreatment process, the present invention first performs mechanical filtration on the waste acid solution, which can effectively remove the tarry substances and carbides generated under high-temperature conditions in the waste acid solution, as well as the unreacted para-ester raw materials and sulfonation intermediates. Then, activated carbon adsorption is carried out, which can effectively remove the soluble organic substances and small-molecule impurities in the waste acid solution. Through the combined action of mechanical filtration and activated carbon adsorption, most of the organic substances in the waste acid solution can be effectively removed, providing preparatory work for the subsequent recovery of sulfuric acid.

[0018] Preferably, the particle size of the activated carbon is 2-4 mm, and the specific surface area ≥ 1000 m 2 / g;

[0019] The mass ratio of the activated carbon to the waste acid solution is 1:8-13.

[0020] The present invention can more efficiently remove impurities in the waste acid solution by optimizing the particle size of the activated carbon and the mass ratio to the waste acid solution.

[0021] Preferably, in Step 2, the triple-effect evaporation system includes a first-effect evaporator, a second-effect evaporator, and a third-effect evaporator connected in series in sequence;

[0022] The temperature of the first-effect evaporator is 120-130 °C, and the vacuum degree is -0.07 to -0.08 MPa;

[0023] The temperature of the second-effect evaporator is 90-100 °C, and the vacuum degree is -0.05 to -0.06 MPa;

[0024] The temperature of the triple-effect evaporator is 70-80°C, and the vacuum degree is -0.03 to -0.04 MPa.

[0025] The triple-effect evaporation system adopted in the present invention is a first-effect evaporator, a second-effect evaporator, and a third-effect evaporator connected in series in sequence, and each evaporator is provided with an energy recovery device. The first-effect evaporator uses the residual temperature generated during the production process of sulfonated p-ester. After the waste acid solution is concentrated through the triple-effect evaporation system, the concentration of the waste acid solution can be increased from 60-70% to 85-90%, and the steam consumption during the production process of sulfonated p-ester can be reduced by 40%.

[0026] Preferably, in step 3, in the tributyl phosphate-kerosene system, the volume ratio of tributyl phosphate to kerosene is 3:7.

[0027] Preferably, in step 3, during the extraction process, the volume ratio of the waste acid solution to the tributyl phosphate-kerosene system is 2-3:1;

[0028] The rotation speed of the extraction is 3000-4000 rpm.

[0029] Through the extraction treatment, more than 90% of the residual organic matter in the waste acid solution can be removed, and the sulfuric acid loss rate can be controlled below 5%.

[0030] Preferably, in step 4, the ion exchange uses a strongly acidic cation exchange resin;

[0031] During the ion exchange process, the flow rate of the waste acid solution is 10-15 BV / h.

[0032] Preferably, in step 5, the temperature of the vacuum crystallization is 40-50°C, the vacuum degree is -0.090 to -0.095 MPa, and the vacuum crystallization time is 4-6 h.

[0033] (III) Beneficial effects

[0034] The present invention provides a method for recovering waste acid during the production process of sulfonated p-ester. It has the following beneficial effects:

[0035] (1) For the method for recovering waste acid during the production process of sulfonated p-ester provided by this solution, through a multi-stage combined process, the sulfuric acid recovery rate can reach more than 90%, the concentration ≥ 92.5%, and the purity ≥ 98%.

[0036] (2) For the method for recovering waste acid during the production process of sulfonated p-ester provided by this solution, through steps such as pretreatment, extraction, and ion exchange, organic matter and metal ions in the waste acid solution can be effectively removed, the purity of sulfuric acid is improved, the recovery cost is low, and the heat energy is recycled. Specific embodiments

[0037] To better illustrate the content of the present invention, the following will be described in detail with specific embodiments.

[0038] Example 1

[0039] A method for recovering waste acid in the production process of sulfonated para-ester includes the following steps:

[0040] Pretreatment: Pass the waste acid solution through an acid-resistant ceramic membrane filter with a pore size of 1 μm to remove large solid impurities, and then use activated carbon with a particle size of 2 mm and a specific surface area of 1200 m 2 / g to adsorb the waste acid solution, and adjust the mass ratio of activated carbon to waste acid solution to 1:10;

[0041] Triple-effect evaporation concentration: Pass the pretreated waste acid solution into a triple-effect evaporation system, adjust the temperature of the first-effect evaporator to 125 °C and the vacuum degree to -0.075 MPa; the temperature of the second-effect evaporator to 95 °C and the vacuum degree to -0.055 MPa; the temperature of the third-effect evaporator to 75 °C and the vacuum degree to -0.035 MPa to obtain a waste acid solution with a concentration of 88%;

[0042] Solvent extraction: Use a tributyl phosphate-kerosene system with a volume ratio of 3:7 to extract the concentrated waste acid solution, adjust the volume ratio of the waste acid solution to the extractant to 2.5:1, and the extraction rotation speed to 3500 rpm;

[0043] Ion exchange: Use a strong acidic cation exchange resin to perform ion exchange on the waste acid solution, and adjust the flow rate of the waste acid solution to 12 BV / h;

[0044] Vacuum crystallization: Crystallize the purified waste acid solution at 45 °C and a vacuum degree of -0.093 MPa for 5 h to obtain concentrated sulfuric acid with a concentration of 93% and a purity of 98.5%.

[0045] Example 2

[0046] A method for recovering waste acid in the production process of sulfonated para-ester includes the following steps:

[0047] Pretreatment: Pass the waste acid solution through an acid-resistant ceramic membrane filter with a pore size of 3 μm to remove large solid impurities, and then use activated carbon with a particle size of 3 mm and a specific surface area of 1100 m 2 / g to adsorb the waste acid solution, and adjust the mass ratio of activated carbon to waste acid solution to 1:12;

[0048] Triple-effect evaporation concentration: The pretreated waste acid solution is introduced into a triple-effect evaporation system. The temperature of the first-effect evaporator is controlled at 130 °C and the vacuum degree is -0.08 MPa; the temperature of the second-effect evaporator is 100 °C and the vacuum degree is -0.6 MPa; the temperature of the third-effect evaporator is 80 °C and the vacuum degree is -0.04 MPa, obtaining a waste acid solution with a concentration of 90%;

[0049] Solvent extraction: The concentrated waste acid solution is extracted using a tributyl phosphate-kerosene system with a volume ratio of 3:7. The volume ratio of the waste acid solution to the extractant is controlled at 3:1, and the extraction rotation speed is 4000 rpm;

[0050] Ion exchange: The waste acid solution is subjected to ion exchange using a strongly acidic cation exchange resin. The flow rate of the waste acid solution is controlled at 15 BV / h;

[0051] Vacuum crystallization: The purified waste acid solution is crystallized at 50 °C and a vacuum degree of -0.095 MPa for 6 h, obtaining concentrated sulfuric acid with a concentration of 92.5% and a purity of 98%.

[0052] Example 3

[0053] A method for recovering waste acid in the production process of sulfonated para-ester, comprising the following steps:

[0054] Pretreatment: The waste acid solution is introduced into an acid-resistant ceramic membrane filter with a pore size of 5 μm to remove large solid impurities, and then activated carbon with a particle size of 4 mm and a specific surface area of 1000 m 2 / g is used to adsorb the waste acid solution. The mass ratio of the activated carbon to the waste acid solution is controlled at 1:8;

[0055] Triple-effect evaporation concentration: The pretreated waste acid solution is introduced into a triple-effect evaporation system. The temperature of the first-effect evaporator is controlled at 120 °C and the vacuum degree is -0.07 MPa; the temperature of the second-effect evaporator is 90 °C and the vacuum degree is -0.5 MPa; the temperature of the third-effect evaporator is 70 °C and the vacuum degree is -0.03 MPa, obtaining a waste acid solution with a concentration of 86%;

[0056] Solvent extraction: The concentrated waste acid solution is extracted using a tributyl phosphate-kerosene system with a volume ratio of 3:7. The volume ratio of the waste acid solution to the extractant is controlled at 2:1, and the extraction rotation speed is 3000 rpm;

[0057] Ion exchange: The waste acid solution is subjected to ion exchange using a strongly acidic cation exchange resin. The flow rate of the waste acid solution is controlled at 10 BV / h;

[0058] Vacuum crystallization: The purified waste acid solution is crystallized at 40 °C and a vacuum degree of -0.090 MPa for 4 h, obtaining concentrated sulfuric acid with a concentration of 92.5% and a purity of 98%.

[0059] The concentrated sulfuric acid prepared according to the technical solutions of Embodiment 1 to Embodiment 3 can all be used for the recycling of concentrated sulfuric acid, and the recycling is efficient, with low energy consumption, and the wastewater discharge is more environmentally friendly.

[0060] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering spent acid in a sulfonated para-ester production process, characterized in that: The following steps are involved: Step 1, pre-treating the waste acid solution to remove solid particles and some organic matter in the waste acid solution, wherein the solid particles include tar-like substances, unreacted sulfonation raw materials and carbides, and the part of the organic matter includes sulfonation decomposition products, sulfonation intermediates and polyaromatic hydrocarbons; Step 2, passing the waste acid solution pretreated in step 1 into a triple-effect evaporation system to concentrate the waste acid, thereby increasing the acid concentration in the waste acid solution to 85-90%; Step 3, extracting the waste acid solution after the waste acid concentration in step 2 with a tributyl phosphate-kerosene system to remove residual organic matter; Step 4, performing ion exchange on the waste acid solution extracted in step 3 to remove metal ions; Step 5: vacuum crystallize the waste acid solution obtained in step 4 to obtain concentrated sulfuric acid with a concentration of ≥92.5% and a purity of ≥98%.

2. The method for recovering waste acid in a sulfonated para-ester production process according to claim 1, characterized in that: In step 1, the pretreatment includes mechanical filtration and adsorption treatment; The mechanical filtration uses an acid-resistant ceramic membrane filter with a pore size of 1 to 5 μm; The adsorption treatment uses activated carbon to adsorb the waste acid solution.

3. The method for recovering waste acid in a sulfonated para-ester production process according to claim 2, characterized in that: The particle size of the activated carbon is 2-4 mm, and the specific surface area is ≥1000m 2 / g; The mass ratio of the activated carbon to the waste acid solution is 1:8-13.

4. The method for recovering waste acid in a sulfonated para-ester production process according to claim 1, characterized in that: In step 2, the three-effect evaporation system comprises a first-effect evaporator, a second-effect evaporator and a third-effect evaporator connected in series in sequence; The temperature of the first-effect evaporator is 120-130°C, and the vacuum degree is -0.07-0.08MPa; The temperature of the second-effect evaporator is 90-100°C, and the vacuum degree is -0.05--0.06MPa; The temperature of the triple-effect evaporator is 70-80° C., and the vacuum degree is -0.03-0.04 MPa.

5. The method for recovering waste acid in a sulfonated para-ester production process according to claim 1, characterized in that: In step 3, in the tributyl phosphate-kerosene system, the volume ratio of tributyl phosphate to kerosene is 3:

7.

6. The method for recovering waste acid in a sulfonated para-ester production process according to claim 1, characterized in that: In step 3, during the extraction process, the volume ratio of the waste acid solution to the tributyl phosphate-kerosene system is 2 to 3:1; The extraction rotation speed is 3000-4000 rpm.

7. The method for recovering waste acid in a sulfonated para-ester production process according to claim 1, characterized in that: In step 4, the ion exchange uses a strongly acidic cation exchange resin; During the ion exchange process, the flow rate of the waste acid solution is 10 to 15 BV / h.

8. The method for recovering waste acid in a sulfonated para-ester production process according to claim 1, characterized in that: In step 5, the temperature of the vacuum crystallization is 40 to 50° C., the vacuum degree is -0.090 to -0.095 MPa, and the vacuum crystallization time is 4 to 6 hours.