Methyl (meth) acrylate production wastewater treatment process

Abstract

The invention relates to the technical field of chemical production, and discloses a methyl (meth) acrylate production wastewater treatment process. The invention relates to a methyl (meth) acrylate production wastewater treatment process. The process comprises the following steps: removing light components in wastewater; mixing the wastewater from which the light components are removed with an extraction agent, so that acid in the wastewater enters the extraction agent to obtain an acid extraction solution; separating the extracting agent from the acid extracting solution to obtain an acid solution; and further refining the acid liquor to obtain a mixed acid product. According to the technical scheme provided by the invention, a specific process of removing light components in the wastewater, extracting acid substances in the wastewater by using the extracting agent, recycling the extracting agent and recycling the mixed acid is adopted, so that the acid substances in the wastewater can be effectively removed, and a mixed acid product with the purity of 95 wt% or above can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical production, and particularly relates to a process for treating wastewater from the production of methyl (meth) acrylate. Background Art

[0002] Using methyl acetate and formaldehyde as raw materials, methyl acrylate can be produced through a one-step aldol condensation reaction, or methyl methacrylate can be further produced through a second-step aldol condensation. This not only solves the problem of overcapacity in the formaldehyde industry but also generates good economic benefits, making it a chemical industry with good comprehensive effects.

[0003] Among them, the chemical reactions involved include:

[0004] CH 3 COOCH 3 +HCHO→CH 2 =CHCOOCH 3 +H 2 O;

[0005] CH 2 =CHCOOCH 3 +H 2 →CH 3 CH 2 COOCH 3 ;

[0006] CH 3 CH 2 COOCH 3 +HCHO→CH 2 =CHCH 3 COOCH 3 +H 2 O;

[0007] The by-products generated by the above reactions include dimethyl ether, CO 2 , acetic acid, acrylic acid, methyl methacrylate, acrylic acid, and acrolein, etc. Among them, although the content of acid by-products such as acetic acid and acrylic acid is small, it is difficult to separate them by distillation. In the prior art, there is generally no special recovery for the waste acid among them, but it is directly sent to the sewage treatment plant for treatment. The presence of acid substances increases the difficulty of sewage treatment, and the cost of sewage treatment is closely related to the acid content in the wastewater. Generally, the cost is relatively low when it is 0.05wt% - 0.1wt%, and after exceeding 0.3wt%, not only the cost will increase greatly, but also material loss will occur. The above sewage treatment cost problem needs to be calculated during the project design stage. Excessive sewage treatment cost may lead to the project not being implemented.

[0008] Therefore, there is an urgent need for a solution to recover and treat acid by-products to solve the problem of sewage treatment. Summary of the Invention

[0009] The main object of the present invention is to provide a process for treating wastewater from the production of methyl (meth)acrylate and a recovery device, aiming to solve the problem that acid by-products in the wastewater from the production of methyl acrylate affect the recovery and treatment of downstream wastewater in the prior art.

[0010] To achieve the above object, the present invention provides a process for treating wastewater from the production of methyl (meth)acrylate, comprising the following steps:

[0011] S10: Provide wastewater from the production of methyl acrylate and / or methyl methacrylate, and remove light components from the wastewater;

[0012] S20: Mix the wastewater after removing light components with an extractant, so that the acid in the wastewater enters the extractant, obtaining an acid extraction solution and deacidified wastewater containing the extractant;

[0013] S30: Separate the extractant from the acid extraction solution and the deacidified wastewater containing the extractant;

[0014] S40: Further refine the acid solution separated from the acid extraction solution to obtain a mixed acid product.

[0015] Optionally, in step S30, the extractant separated from the acid extraction solution and / or the extractant separated from the deacidified wastewater containing the extractant is returned to step S20 for reuse.

[0016] Optionally, in step S20, the extractant is selected from at least one of dimethyl sulfoxide, methyl ethyl ketone, and isobutyl isobutyrate.

[0017] Optionally, in step S20, the extractant is a mixed solvent of methyl ethyl ketone and dimethyl sulfoxide; or, the extractant is a mixed solvent of methyl ethyl ketone and isobutyl isobutyrate;

[0018] Wherein, the proportion of methyl ethyl ketone in the mixed solvent is 1 wt% - 10 wt%.

[0019] Optionally, in step S20, the mass dosage of the extractant is 0.5 - 5 times the mass of the wastewater.

[0020] Optionally, in step S10, a light removal tower is used for light removal, mainly removing light components such as methyl acetate and methanol in the wastewater; the operating conditions of the light removal tower are: atmospheric distillation, the top temperature is 50 - 65°C, and the bottom temperature is 100 - 110°C.

[0021] Optionally, in step S20, the wastewater after removing light components is fed into the upper part of the extraction column, and the extractant is fed into the lower part of the extraction column. The extractant and the wastewater perform countercurrent extraction in the column, and the acid in the wastewater enters the extractant.

[0022] The acid extraction liquid is taken out from the top of the extraction column, and the deacidified wastewater containing the extractant is taken out from the bottom of the extraction column.

[0023] The operating pressure of the extraction column is atmospheric pressure, and the temperature is 10 - 40 °C.

[0024] Optionally, in step S30, the acid extraction liquid taken out from the top of the extraction column is fed into the extractant recovery column. The extractant recovery column performs vacuum rectification operation. The extractant is taken out from the top of the column and recycled, and the acid liquid is taken out from the bottom of the column.

[0025] The operating pressure of the extractant recovery column is -90 kPa to atmospheric pressure, the temperature at the bottom of the column is 90 - 130 °C, and the temperature at the top of the column is 50 - 80 °C.

[0026] Optionally, in step S40, the acid liquid taken out from the bottom of the extractant recovery column is fed into the acid recovery column. The acid recovery column performs vacuum rectification operation. The mixed acid product is taken out from the top of the column, and the impurities are at the bottom of the column.

[0027] The operating pressure of the acid recovery column is -90 kPa to -50 kPa, the temperature at the bottom of the column is 70 - 85 °C, and the temperature at the top of the column is 50 - 60 °C.

[0028] Optionally, the purity of the mixed acid taken out from the top of the acid recovery column reaches more than 95 wt%.

[0029] Optionally, in step S20, the deacidified wastewater containing the extractant taken out from the bottom of the extraction column is fed into the wastewater stripping column. The extractant is taken out from the top of the wastewater stripping column and recycled, and the wastewater after removing the extractant and acid is taken out from the bottom of the column.

[0030] The operating pressure of the wastewater stripping column is atmospheric pressure, the temperature at the bottom of the column is 95 - 110 °C, and the temperature at the top of the column is 85 - 95 °C.

[0031] Optionally, in step S20, the mass flow ratio of the extractant to the wastewater entering the extraction column is 0.5 - 5:1.

[0032] In the technical solution of the present invention, the production wastewater of methyl (meth)acrylate is first de-lighted to separate light components such as methyl acetate and methanol in the wastewater. The separated light components can be returned to the methyl (meth)acrylate reaction system as raw materials for the production of methyl (meth)acrylate. The wastewater after removing the light components is sent to an extraction tower. The extractant is added from the lower part of the tower, and the wastewater is added from the upper part of the tower. The extractant and the wastewater carry out mass transfer and exchange in the tower, and the acid in the wastewater enters the extractant. The acid extraction liquid drawn from the top of the extraction tower is sent to an extractant recovery tower for separation and recovery. The extractant drawn from the top of the tower can be reused as a raw material source for the extractant, and the acid liquid is drawn from the bottom of the tower. The acid liquid drawn from the bottom of the extractant recovery tower is sent to an acid recovery tower for further refining, and a mixed acid product with a purity of more than 95 wt% can be drawn from the top of the tower.

[0033] The deacidified wastewater containing the extractant drawn from the bottom of the extraction tower is sent to a wastewater stripping tower for stripping to recover the extractant. The extractant drawn from the top of the tower can be reused as a raw material source for the extractant. The total acid content in the deacidified wastewater drawn from the bottom of the tower can reach less than 0.3 wt%, meeting the requirements of most sewage treatment plants.

[0034] The technical solution of the present invention adopts an extractant to extract the acid substances in the wastewater, which can not only effectively remove the acid by-products in the wastewater and reduce the cost of sewage treatment, but also obtain a mixed acid product with a purity of more than 95 wt%. Brief Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0036] Figure 1 It is a schematic structural diagram of an embodiment of an acid recovery device for the production wastewater of methyl (meth)acrylate provided by the present invention.

[0037] Explanation of the Reference Numerals in the Drawings:

[0038] 1. De-lighting tower; 2. Extraction tower; 3. Extractant recovery tower; 4. Acid recovery tower; 5. Wastewater stripping tower.

[0039] The realization, functional features and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the drawings. Detailed Embodiments

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] It should be noted that if there are directional indications (such as up, down, left, right, front, back,...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0042] In addition, if there are descriptions such as "first" and "second" involved in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that satisfies both A and B at the same time. In addition, the technical solutions between the embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0043] Unless otherwise specified, the values of pressure in the present invention are gauge pressures.

[0044] The fresh extractants provided in the present invention are all of analytical purity.

[0045] The production wastewater of methyl acrylate and / or methyl methacrylate refers to the production wastewater of methyl acrylate, or the production wastewater of methyl methacrylate, or the combined wastewater of the production wastewater of methyl acrylate and the production wastewater of methyl methacrylate.

[0046] The technical solutions of 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 following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0047] The wastewater used in the embodiments of the present application comes from the combined wastewater (hereinafter referred to as "wastewater") of a certain MMA production enterprise (10,000 tons / year), in which the acid concentration is 6.0 ± 1.0 wt%, and it contains acetic acid, propionic acid, acrylic acid and methacrylic acid.

[0048] Example 1

[0049] Combined with the attached Figure 1 , a process for treating waste water from methyl methacrylate production, comprising the following steps:

[0050] Provide waste water and fresh extractant, wherein the fresh extractant is dimethyl sulfoxide.

[0051] Send the waste water to the light component removal tower 1. The light component removal tower is rectified at atmospheric pressure. The top temperature of the tower is 60 °C, and the bottom temperature of the tower is 100 °C. Light components such as methyl acetate and methanol are taken out from the top of the light component removal tower, and the waste water after removing the light components is taken out from the bottom of the tower. The light components taken out from the top of the light component removal tower are returned to the production system as raw materials for the MMA production system.

[0052] The waste water after removing the light components taken out from the bottom of the light component removal tower is sent to the extraction tower 2, and the extractant is sent into the extraction tower. Among them, the extractant is added from the lower part of the extraction tower, and the waste water is added from the upper part of the extraction tower. The operating conditions of the extraction tower are: atmospheric pressure. The extractant and the waste water carry out countercurrent mass transfer exchange in the tower, and the acid in the waste water enters the extractant. The acid extraction liquid is taken out from the top of the extraction tower, and the deacidified waste water containing a small amount of extractant is taken out from the bottom of the tower.

[0053] In order to enable several acidic substances in the waste water to enter the extractant more fully, the extractant in the extraction tower needs to be in excess relative to the acid in the waste water. However, too much extractant will cause too much extractant at the bottom of the tower, bringing pressure to the subsequent extractant recovery. In this embodiment, the mass flow ratio of the extractant and the waste water entering the extraction tower is controlled to be 1:1.

[0054] Send the acid extraction liquid taken out from the top of the extraction tower to the extractant recovery tower 3. The extractant recovery tower operates at atmospheric pressure. The top temperature of the tower is 60 °C, and the bottom temperature of the tower is 100 °C. The extractant is taken out from the top of the extractant recovery tower, and the light components containing the extractant taken out are refluxed to the extraction tower as extractant raw materials; the acid liquid is taken out from the bottom of the extractant recovery tower.

[0055] Send the acid liquid taken out from the bottom of the extractant recovery tower to the acid recovery tower 4 for further refining. The operating pressure of the acid recovery tower is -60 kPa, the top temperature of the tower is 55 °C, and the bottom temperature of the tower is 80 °C. The mixed acid product is taken out from the top of the acid recovery tower. After the system operates stably for 1 hour, samples are taken to measure the composition of the mixed acid product, which contains acetic acid, propionic acid, acrylic acid, and methacrylic acid, and the total content of the four components reaches more than 95 wt%.

[0056] The deacidified wastewater containing a small amount of extractant withdrawn from the bottom of the extraction column is sent into the wastewater stripping column 5. The wastewater stripping column operates at atmospheric pressure, with the top temperature at 90 °C and the bottom temperature at 100 °C. After stripping treatment, the light components containing the extractant are withdrawn from the top of the column, and the deacidified wastewater is withdrawn from the bottom of the column. The light components containing the extractant are refluxed to the extraction column as raw materials for the extractant, and the deacidified wastewater is sent to the downstream sewage treatment device. After the system has been operating stably for 1 hour, a water sample is taken from the bottom of the wastewater stripping column to measure the total acid content in the deacidified wastewater.

[0057] Examples 2 to 5

[0058] Examples 2 to 5 are based on Example 1, and the difference lies in that: different fresh extractants are provided.

[0059] Example 2: The fresh extractant is methyl ethyl ketone.

[0060] Example 3: The fresh extractant is isobutyl isobutyrate.

[0061] Example 4: The fresh extractant is a mixture of methyl ethyl ketone and isobutyl isobutyrate with a mass ratio of 1:49.

[0062] Example 5: The fresh extractant is a mixture of methyl ethyl ketone and dimethyl sulfoxide with a mass ratio of 1:49.

[0063] In Examples 2 to 5, the purity of the mixed acid product withdrawn from the top of the acid recovery column reaches over 95 wt%. The detection conditions of the deacidified wastewater at the bottom of the wastewater stripping column in Examples 1 to 5 are shown in Table 1 below.

[0064] Table 1 Acid content in the deacidified wastewater of Examples 1 to 5 (unit: wt%)

[0065]

[0066]

[0067] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the patent protection scope of the present invention.

Claims

1. A process for treating wastewater from the production of methyl (meth)acrylate, characterized in that: The following steps are involved: S10, providing methyl acrylate and / or methyl methacrylate production wastewater, and removing light components in the wastewater; S20, mixing the wastewater after light components are removed with an extractant, so that the acid in the wastewater enters the extractant, and obtaining an acid extract and deacidified wastewater containing the extractant; S30, separating the acid extract and the extractant in the deacidification wastewater containing the extractant; S40, further refining the acid solution separated from the acid extract to obtain a mixed acid product.

2. The process for treating wastewater from the production of methyl (meth)acrylate according to claim 1, wherein: In the step S30, the extractant separated from the acid extract and / or the extractant separated from the deacidification wastewater containing the extractant is returned to the step S20 for reuse.

3. The process for treating wastewater from the production of methyl (meth)acrylate according to claim 1, wherein: In step S20, the extractant is selected from at least one of dimethyl sulfoxide, methyl ethyl ketone and isobutyl isobutyrate.

4. The process for treating wastewater from the production of methyl (meth)acrylate according to claim 3, wherein: In step S20, the extractant is a mixed solvent of methyl ethyl ketone and dimethyl sulfoxide; or The extractant is a mixed solvent of methyl ethyl ketone and isobutyl isobutyrate; Wherein, the proportion of the methyl ethyl ketone in the mixed solvent is 1wt% to 10wt%.

5. The process for treating wastewater from the production of methyl (meth)acrylate according to claim 1, characterized in that: In step S20, the mass dosage of the extractant is 0.5 to 5 times the mass of the wastewater.

6. The process for treating wastewater from the production of methyl (meth)acrylate according to claim 1, wherein: In the step S20, the wastewater after the light components are removed is fed into the upper part of the extraction tower, and the extractant is fed into the lower part of the extraction tower, the extractant and the wastewater are subjected to countercurrent extraction in the tower, and the acid in the wastewater enters the extractant; The acid extract is taken out from the top of the extraction tower, and the deacidified wastewater containing the extractant is taken out from the bottom of the extraction tower; The operating pressure of the extraction tower is normal pressure and the temperature is 10-40°C.

7. The process for treating wastewater from the production of methyl (meth)acrylate according to claim 6, characterized in that: In the step S30, the acid extract extracted from the top of the extraction tower is sent to the extractant recovery tower, and the extractant recovery tower is vacuum distilled, the extractant is extracted from the top of the tower and reused, and the acid solution is extracted from the bottom of the tower; The operating pressure of the extractant recovery tower is -90kpa to normal pressure, the bottom temperature is 90-130°C, and the top temperature is 50-80°C.

8. The process for treating wastewater from the production of methyl (meth)acrylate according to claim 7, characterized in that: In the step S40, the acid solution extracted from the bottom of the extractant recovery tower is sent to the acid recovery tower, and the acid recovery tower is subjected to vacuum distillation operation, and a mixed acid product is extracted from the top of the tower, and impurities are extracted from the bottom of the tower; The operating pressure of the acid recovery tower is -90kpa to -50kpa, the bottom temperature is 70-85°C, and the top temperature is 50-60°C.

9. The process for treating wastewater from the production of methyl (meth)acrylate according to claim 6, wherein: In the step S20, the deacidified wastewater containing the extractant extracted from the bottom of the extraction tower is sent to a wastewater stripping tower, the extractant is extracted from the top of the wastewater stripping tower and reused, and the wastewater from which the extractant and acid are removed is extracted from the bottom of the tower; The operating pressure of the wastewater stripping tower is normal pressure, the bottom temperature is 95-110°C, and the top temperature is 85-95°C.

10. The process for treating wastewater from the production of methyl (meth)acrylate according to claim 6, characterized in that: In the step S20, the mass flow rate ratio of the extractant and the wastewater entering the extraction tower is 0.5 to 5:1.

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