阅读说明：本技术 一种生产聚丙烯腈碳纤维的dmso水溶液精馏残渣的回收利用方法 (Method for recycling DMSO (dimethyl sulfoxide) aqueous solution rectification residues in production of polyacrylonitrile carbon fibers ) 是由 陈秋飞 丁正南 常维平 李宇 于 2021-07-30 设计创作，主要内容包括：本发明公开了一种生产聚丙烯腈碳纤维的DMSO水溶液精馏残渣的回收利用方法。聚丙烯腈碳纤维生产过程中产生含DMSO水溶液,通过对水溶液的浓缩及精馏实现DMSO回收再利用,然而精馏过程中会产生大量的废渣,不仅导致再沸器换热效率的降低,且造成大量的热能及成本的浪费。本发明通过NaOH与溶解在DMSO水溶液中的低分子量聚丙烯腈发生水解反应,当DMSO达到一定浓度时,加入电解质将水解生成的高沸物聚丙烯酸钠聚沉,利用气浮池实现聚丙烯酸钠的分离,再经压滤,漂洗,造粒等工艺获得副产聚丙烯酸钠,可用于水处理剂、盐水精制及胶乳增稠等工业领域,做到变废为宝,同时减少污染,实现降本增效。气浮池下层淡黄色清夜继续浓缩后进入精馏塔,减压蒸馏获得成品DMSO。(The invention discloses a recycling method of DMSO (dimethyl sulfoxide) aqueous solution rectification residues for producing polyacrylonitrile carbon fibers. The production contains DMSO aqueous solution in the polyacrylonitrile carbon fiber production process, realizes DMSO through the concentration and the rectification to the aqueous solution and retrieves and recycle, nevertheless can produce a large amount of waste residues among the rectification process, not only leads to reboiler heat exchange efficiency's reduction, and causes the waste of a large amount of heat energy and cost. According to the invention, NaOH and low-molecular-weight polyacrylonitrile dissolved in a DMSO aqueous solution are subjected to hydrolysis reaction, when the DMSO reaches a certain concentration, electrolyte is added to perform coagulation on high-boiling-point sodium polyacrylate generated by hydrolysis, separation of sodium polyacrylate is realized by using an air flotation tank, and a byproduct sodium polyacrylate is obtained by processes such as pressure filtration, rinsing, granulation and the like. And (4) continuously concentrating the light yellow clear liquid at the lower layer of the air floatation tank, then feeding the light yellow clear liquid into a rectifying tower, and carrying out reduced pressure distillation to obtain a finished product DMSO.)

1. A recycling method of DMSO (dimethylsulfoxide) aqueous solution rectification residues for producing polyacrylonitrile carbon fibers is characterized by comprising the following specific steps of:

firstly, quantitatively adding a NaOH solution into a DMSO wastewater conveying pipeline for producing polypropylene carbon fibers through a metering pump, adjusting pH, mixing the solution by a static mixer, collecting the mixture in a storage tank, and continuously circulating the DMSO wastewater in the storage tank through an external circulating pump to keep the DMSO wastewater uniform;

secondly, controlling the flow of an external circulating pump to a dehydration tower through a flowmeter, heating the wastewater to a certain temperature through a reboiler, then feeding the wastewater into the dehydration tower, heating and circulating tower bottom liquid to the tower bottom through the reboiler, and controlling the temperature in the tower and the pressure at the tower top;

thirdly, controlling the concentration of DMSO (dimethyl sulfoxide) by extracting an opening degree of an adjusting valve at the bottom of the tower, quantitatively adding a coagulation agent into a DMSO aqueous solution pipeline by using a coagulation agent solution metering pump, linking the opening degree of the coagulation agent solution metering pump with a DMSO solution flowmeter, fully mixing by using a static mixer, controlling the temperature of a mixed material, flowing into a water tank through a pipeline, and carrying out heat preservation and stirring in the water tank for a period of time;

step four, overflowing the mixed liquid in the water tank to an air flotation sedimentation tank through liquid level difference, feeding the lower layer clear liquid into a dehydrating tower reboiler through a conveying pump, heating, carrying out reduced pressure distillation, and feeding the lower layer clear liquid into a rectifying tower, wherein the amount of the rectifying residue is reduced by more than 95%; collecting the upper layer solid through a scraper and pumping to a filter press;

fifthly, after filter pressing, the obtained solid is rinsed by mother liquor, then filter pressed and crushed to obtain a light yellow crude product;

and sixthly, adding the crude product into methanol according to a certain proportion, heating, stirring at constant temperature for reaction for a period of time, carrying out filter pressing by a filter press, and then sending into an oven for drying and granulating to obtain a finished product sodium polyacrylate solid.

2. The method for recycling the distillation residue of the DMSO aqueous solution for producing the polyacrylonitrile carbon fiber as claimed in claim 1, which is characterized in that: in the first step, the mass concentration of the NaOH solution is 25-50%.

3. The method for recycling the distillation residue of the DMSO aqueous solution for producing the polyacrylonitrile carbon fiber as claimed in claim 1, which is characterized in that: in the first step, the pH is controlled between 8 and 12.

4. The method for recycling the distillation residue of the DMSO aqueous solution for producing the polyacrylonitrile carbon fiber as claimed in claim 1, which is characterized in that: in the second step, the concentration temperature is 120-165 ℃, the concentration residence time is 3-5h, and the pressure at the top of the tower is 0.5 Mpa.

5. The method for recycling the distillation residue of the DMSO aqueous solution for producing the polyacrylonitrile carbon fiber as claimed in claim 1, which is characterized in that: in the third step, the coagulation agent is FeCl₃Or AlCl₃The mass concentration is 10-50%, and the addition amount is 1-5kg solution/ton DMSO waste liquid.

6. The method for recycling the distillation residue of the DMSO aqueous solution for producing the polyacrylonitrile carbon fiber as claimed in claim 1, which is characterized in that: in the third step, the DMSO mass concentration is 35-65%, and the temperature is 85-110 ℃.

7. The method for recycling the distillation residue of the DMSO aqueous solution for producing the polyacrylonitrile carbon fiber as claimed in claim 1, which is characterized in that: in the fourth step, the air flotation sedimentation tank is an electrolytic air flotation tank.

8. The method for recycling DMSO rectification residues as defined in claim 1, wherein the method comprises the following steps: and the mother liquid in the fifth step is saturated sodium polyacrylate methanol solution.

9. The method for recycling DMSO rectification residues as defined in claim 1, wherein the method comprises the following steps: and in the sixth step, the mass ratio of the materials to the methanol is 1: 10-2: 10.

Technical Field

The invention relates to the field of carbon fiber production, in particular to a recycling method of DMSO (dimethyl sulfoxide) aqueous solution rectification residues for producing polyacrylonitrile carbon fibers.

Background

Due to excellent physical, mechanical and thermal properties, the carbon fiber is widely applied in the fields of aerospace, transportation, sports goods and the like. The carbon fiber in the current market is mainly prepared by taking polyacrylonitrile as a precursor. DMSO is an excellent organic solvent, is widely used in the preparation process of polyacrylonitrile protofilament, and finally forms waste water containing 20-30 wt% DMSO. For example, in patent CN105731568A, the production cost and environmental pollution can be effectively reduced by rectifying and recovering the wastewater after vacuum dehydration. However, in the rectification process, high-boiling-point substances composed of low-molecular-weight polyacrylonitrile, DMSO decomposers and the like dissolved in the wastewater are easy to generate material viscosity increase, heat transfer is reduced, the cleaning period is shortened, and simultaneously, the problems of drying and incineration treatment of the high-boiling-point substances generate huge cost and the like, so that serious system instability, resource waste and expensive production cost are caused.

Disclosure of Invention

In order to solve the problems existing in the background technology, the dissolved low molecular weight polyacrylonitrile is taken as the main reason, and the acrylonitrile is hydrolyzed and then recovered before vacuum rectification, so that the influence on a rectification system is reduced, and simultaneously, the acrylonitrile can be used as a byproduct sodium polyacrylate to create new economic value. The invention provides a recycling method of DMSO (dimethyl sulfoxide) aqueous solution rectification residues for producing polyacrylonitrile carbon fibers. The method comprises the following steps:

firstly, in the DMSO waste water pipeline of production polypropylene carbon fiber, add NaOH solution through the measuring pump ration, adjust pH, collect in the storage tank after static mixer mixes, make DMSO waste water constantly circulate in the storage tank through external circulating pump, keep the homogeneity.

And secondly, controlling the flow of the external circulating pump to the dehydrating tower through a flow meter, raising the temperature of the wastewater to a certain temperature through a reboiler, entering the dehydrating tower, raising the temperature of tower bottom liquid through the reboiler, circulating the tower bottom liquid, and controlling the temperature in the tower and the pressure at the top of the tower.

And thirdly, controlling the quality concentration of DMSO (dimethyl sulfoxide) by the opening of a bottom extraction regulating valve, quantitatively adding a coagulation agent into a DMSO water solution pipeline by using a coagulation agent solution metering pump, linking the opening of the coagulation agent solution metering pump with a DMSO solution flowmeter, fully mixing by using a static mixer, controlling the temperature of a mixed material, flowing into a water tank through a pipeline, and carrying out heat preservation and stirring in the water tank for a period of time.

Step four, overflowing the mixed liquid in the water tank to an air flotation sedimentation tank through liquid level difference, feeding the lower layer clear liquid into a dehydrating tower reboiler through a conveying pump, heating, carrying out reduced pressure distillation, and feeding the lower layer clear liquid into a rectifying tower, wherein the amount of the rectifying residue is reduced by more than 95%; the upper layer solid is collected by a scraper and then is pumped to a filter press.

And fifthly, rinsing the solid obtained after filter pressing through mother liquor, then carrying out filter pressing, and crushing to obtain a light yellow crude product.

And sixthly, adding the crude product into methanol according to a certain proportion, heating, stirring at constant temperature for reaction for a period of time, carrying out filter pressing by a filter press, and then sending into an oven for drying and granulating to obtain a finished product sodium polyacrylate solid.

The invention has the following advantages:

1, the DMSO aqueous solution becomes viscous along with the increase of the concentration of sodium polyacrylate, and a recovery system is easy to block a heat exchanger and a conveying pipeline, so that unstable production and waste of heat energy are caused; according to the invention, the high-boiling-point sodium polyacrylate in the DMSO aqueous solution is stripped in advance, the cleaning period of the heat exchanger is prolonged from 1 day to 15 days, the consumption of steam is reduced by 20%, the efficiency of DMSO rectification is improved, and the production cost is reduced.

2. High waste is stripped from the distillation residual liquid through a drying machine in the original recovery system, so that a large amount of steam is wasted, the components of the waste are complex, and the waste can only be used as dangerous solid waste to be entrusted and treated. The invention precipitates the sodium polyacrylate from the water through a simple aqueous solution treatment process, and obtains the high molecular weight sodium polyacrylate through a certain treatment process, thereby not only reducing the discharge of dangerous solid wastes, but also endowing the high molecular weight sodium polyacrylate with new functions and economic values, changing waste into valuable, reducing the waste of resources, increasing the operating benefits of companies and reducing the production cost.

Drawings

FIG. 1 is a schematic view of a process flow for recycling rectification residues of DMSO wastewater.

Detailed Description

The invention is further illustrated by the following examples of various coagulants, it being understood that the examples described herein are for the purpose of illustration and explanation only and are not intended to be limiting.

The invention relates to a recycling method of DMSO (dimethyl sulfoxide) aqueous solution rectification residues for producing polyacrylonitrile carbon fibers, which comprises the following steps of:

firstly, quantitatively adding a NaOH solution into a DMSO wastewater conveying pipeline for producing polypropylene carbon fibers through a metering pump, adjusting pH, mixing the solution by a static mixer, collecting the mixture in a storage tank, and continuously circulating the DMSO wastewater in the storage tank through an external circulating pump to keep the DMSO wastewater uniform;

secondly, controlling the flow of an external circulating pump to a dehydration tower through a flowmeter, heating the wastewater to a certain temperature through a reboiler, then feeding the wastewater into the dehydration tower, heating and circulating tower bottom liquid to the tower bottom through the reboiler, and controlling the temperature in the tower and the pressure at the tower top;

thirdly, controlling the quality concentration of DMSO (dimethyl sulfoxide) by the opening of a bottom extraction regulating valve, quantitatively adding a coagulation agent into a DMSO aqueous solution pipeline by using a coagulation agent solution metering pump, linking the opening of the coagulation agent solution metering pump with a DMSO solution flowmeter, fully mixing by using a static mixer, controlling the temperature of a mixed material, flowing into a water tank through a pipeline, and carrying out heat preservation and stirring in the water tank for a period of time;

step four, overflowing the mixed liquid in the water tank to an air flotation sedimentation tank through liquid level difference, feeding the lower layer clear liquid into a dehydrating tower reboiler through a conveying pump, heating, carrying out reduced pressure distillation, and feeding the lower layer clear liquid into a rectifying tower, wherein the amount of the rectifying residue is reduced by more than 95%; collecting the upper layer solid through a scraper and pumping to a filter press;

fifthly, after filter pressing, the obtained solid is rinsed by mother liquor, then filter pressed and crushed to obtain a light yellow crude product;

and sixthly, adding the crude product into methanol according to a certain proportion, heating, stirring at constant temperature for reaction for a period of time, carrying out filter pressing by a filter press, and then sending into an oven for drying and granulating to obtain a finished product sodium polyacrylate solid.

In the first step, the mass concentration of the NaOH solution is 25-50%.

In the first step, the pH is controlled between 8 and 12.

In the second step, the concentration temperature is 120-165 ℃, the concentration residence time is 3-5h, and the pressure at the top of the tower is 0.5 Mpa.

In the third step, the coagulation agent is FeCl₃Or AlCl₃The mass concentration is 10-50%, and the addition amount is 1-5kg solution/ton DMSO waste liquid.

In the third step, the DMSO mass concentration is 35-65%, and the temperature is 85-110 ℃.

In the fourth step, the air flotation sedimentation tank is an electrolytic air flotation tank.

And the mother liquid in the fifth step is saturated sodium polyacrylate methanol solution.

And in the sixth step, the mass ratio of the materials to the methanol is 1: 10-2: 10.

The coagulation agent is FeCl₃Examples

Firstly, adding a 30% NaOH solution by mass concentration into a DMSO wastewater conveying pipeline with 15% of polypropylene carbon fiber concentration through a metering pump at a flow rate of 10kg/h, adjusting the pH value to 9-10, mixing the solution by a static mixer, collecting the mixed solution in a storage tank, and continuously circulating the DMSO wastewater in the storage tank through an external circulating pump to keep the DMSO wastewater uniform.

And secondly, controlling the flow of the DMSO solution in a storage tank entering the dehydration tower to be 20t/h, heating the wastewater to 129 ℃ through a reboiler, entering the dehydration tower, heating the tower bottom liquid through the reboiler, circulating to the tower bottom, controlling the temperature of the kettle bottom to be 145 ℃, and controlling the pressure of the tower top to be 0.45 Mpa.

Thirdly, FeCl with 20 percent mass concentration of the coagulating agent is utilized₃The solution is added into a DMSO aqueous solution pipeline at the speed of 20kg/h, the opening of a coagulation agent solution metering pump is linked with a DMSO solution flow meter extracted from the bottom of the tower, the DMSO mass concentration is controlled to be 55% by adjusting the opening of a valve, the DMSO solution is fully mixed by a static mixer, the temperature of the mixed material is controlled to be 105 ℃, the mixed material flows into a water tank through a pipeline and is stirred in the water tank in a heat preservation way, and the retention time is 2 h.

Step four, overflowing the mixed liquid in the water tank to a vertical electrolytic air flotation tank through a liquid level difference, keeping the mixed liquid for 1h, feeding the lower layer clear liquid into a dehydrating tower reboiler through a conveying pump, heating, carrying out reduced pressure distillation, and then feeding the lower layer clear liquid into a rectifying tower, wherein the amount of the rectification residue is reduced by 97%; the upper layer solid is collected by a scraper and then is pumped to a filter press.

And fifthly, after pressure filtration, the obtained solid is rinsed for many times by mother liquor, and then is subjected to pressure filtration and crushing to obtain a light yellow crude product.

And sixthly, adding the crude product of 200KG into methanol according to the mass ratio of 15%, heating to 60 ℃, stirring at constant temperature for reaction for a period of time, carrying out filter pressing through a filter press, sending into an oven for drying and granulating, and taking out after 5 hours to obtain the finished product of the sodium polyacrylate solid.

The coagulation agent is CaCl₂Comparative example

Firstly, in a DMSO wastewater conveying pipeline for producing polypropylene carbon fiber with the concentration of 15%, adding 30% NaOH solution at the flow rate of 10kg/h through a metering pump, adjusting the pH value to 9-10, mixing the solution by a static mixer, collecting the mixture in a storage tank, and continuously circulating the DMSO wastewater in the storage tank through an external circulating pump to keep uniform.

And secondly, controlling the flow of the DMSO solution in a storage tank entering the dehydration tower to be 20t/h, heating the wastewater to 129 ℃ through a reboiler, entering the dehydration tower, heating the tower bottom liquid through the reboiler, circulating to the tower bottom, controlling the temperature of the kettle bottom to be 145 ℃, and controlling the pressure of the tower top to be 0.45 Mpa.

Thirdly, utilizing 20 percent CaCl of coagulation agent₂The solution is added into a DMSO aqueous solution pipeline at the speed of 20kg/h, the DMSO aqueous solution is still reddish brown, and no solid is separated out.

Comparative example of coagulation agent NaCl

Firstly, in a DMSO wastewater conveying pipeline for producing polypropylene carbon fiber with the concentration of 15%, adding 30% NaOH solution at the flow rate of 10kg/h through a metering pump, adjusting the pH value to 9-10, mixing the solution by a static mixer, collecting the mixture in a storage tank, and continuously circulating the DMSO wastewater in the storage tank through an external circulating pump to keep uniform.

And secondly, controlling the flow of the DMSO solution in a storage tank entering the dehydration tower to be 20t/h, heating the wastewater to 129 ℃ through a reboiler, entering the dehydration tower, heating the tower bottom liquid through the reboiler, circulating to the tower bottom, controlling the temperature of the kettle bottom to be 145 ℃, and controlling the pressure of the tower top to be 0.45 Mpa.

And thirdly, adding a coagulating agent 20% NaCl solution into the DMSO aqueous solution pipeline at the speed of 20kg/h, wherein the DMSO aqueous solution is still reddish brown and no solid is separated out.

The coagulation agent is ZnCl₂Examples

Firstly, in a DMSO wastewater conveying pipeline for producing polypropylene carbon fiber with the concentration of 15%, adding 30% NaOH solution at the flow rate of 10kg/h through a metering pump, adjusting the pH value to 9-10, mixing the solution by a static mixer, collecting the mixture in a storage tank, and continuously circulating the DMSO wastewater in the storage tank through an external circulating pump to keep uniform.

And secondly, controlling the flow of the DMSO solution in a storage tank entering the dehydration tower to be 20t/h, heating the wastewater to 129 ℃ through a reboiler, entering the dehydration tower, heating the tower bottom liquid through the reboiler, circulating to the tower bottom, controlling the temperature of the kettle bottom to be 145 ℃, and controlling the pressure of the tower top to be 0.45 Mpa.

Thirdly, using 20 percent of ZnCl as coagulation agent₂The solution is added into a DMSO aqueous solution pipeline at the speed of 20kg/h, the DMSO aqueous solution is still reddish brown, and no solid is separated out.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and modifications can be made, and equivalents can be substituted for elements thereof. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.