阅读说明：本技术 聚苯硫醚生产中溶剂和原料的分离回收系统及方法 (System and method for separating and recovering solvent and raw materials in polyphenylene sulfide production ) 是由 马强 尹恩太 张千贺 耿骆 卢文明 于 2020-05-11 设计创作，主要内容包括：本发明公开了一种对聚苯硫醚工业生产中的溶剂NMP和原料对二氯苯通过减压蒸馏等方式有效分离和回收溶剂氮甲基吡咯烷酮、原料对二氯苯和水洗水的系统和方法,所述系统包括塔板式脱水塔,卧式沉降罐,汽提塔,和塔板式回收塔等装置。根据本发明的回收分离系统结构简便,方法操作简单,成本低。基本打通了具有高回收率、可靠、环保的NMP回收工艺路线,解决了在生产PPS生产过程中回收溶剂时出现的易分解、回收率低等问题。回收的氮甲基吡咯烷酮和对二氯苯的纯度高,不仅可以循环回收利用溶剂NMP,同时还将PPS生产过程中剩余的原料对二氯苯得以循环利用。回收的水分可以作重复利用,有效减少了工艺中产生的废水,降低污水治理成本。(The invention discloses a system and a method for effectively separating and recovering azomethyl pyrrolidone, p-dichlorobenzene as a raw material and water washing water from a solvent NMP and the p-dichlorobenzene as the raw material in the industrial production of polyphenylene sulfide in a vacuum distillation mode and the like. The recovery and separation system has simple structure, simple method operation and low cost. Basically gets through the NMP recovery process route with high recovery rate, reliability and environmental protection, and solves the problems of easy decomposition, low recovery rate and the like when the solvent is recovered in the production process of PPS. The recovered azomethyl pyrrolidone and p-dichlorobenzene have high purity, and can recycle the solvent NMP and recycle the residual raw material p-dichlorobenzene in the PPS production process. The recovered water can be reused, thereby effectively reducing the waste water generated in the process and lowering the sewage treatment cost.)

1. A separation and recovery system for solvent N-methyl pyrrolidone and raw material p-dichlorobenzene in industrial production of polyphenylene sulfide comprises:

a plate type dehydration tower which receives a mixed solution of reaction mother liquor produced by polyphenylene sulfide and washing liquor recovered by a washing system through a pipeline and separates the mixed solution by distillation, wherein water and p-dichlorobenzene are evaporated and condensed from the top of the plate type dehydration tower, crude N-methyl pyrrolidone is discharged from the bottom of the dehydration tower, the theoretical plate number of the plate type dehydration tower is 33-37, the operation pressure is 48-52Kpa, and the temperature is 215-225 ℃;

the horizontal settling tank is connected with the top of the tower plate type dehydrating tower through a pipeline, receives water and p-dichlorobenzene evaporated and condensed from the top of the tower plate type dehydrating tower, separates the water and the p-dichlorobenzene, and recovers the separated p-dichlorobenzene to a p-dichlorobenzene raw material tank in the production of the polyphenylene sulfide, wherein the operation pressure of the horizontal settling tank is 8-12Kpa, the temperature is 90-100 ℃, and the valve is opened according to the accumulation condition of the liquid level in the tank body until the volume in the tank body is more than 80 percent for discharging;

the stripping tower is connected with the horizontal settling tank through a pipeline, receives water separated from the horizontal settling tank, adopts circulating steam to strip and remove trace p-dichlorobenzene in the water separated from the horizontal settling tank, the recovered p-dichlorobenzene is recycled to a raw material tank for polyphenylene sulfide production, and the water collected from the stripping tower is conveyed to a liquid storage tank for recycling, wherein the stripping tower is a packed tower, the height of the packing is 4-5 meters, the operating pressure is 13-17Kpa, and the temperature is 98-104 ℃;

and the plate type recovery tower is connected with the bottom of the plate type dehydration tower through a pipeline, receives crude N-methyl pyrrolidone discharged from the bottom of the plate type dehydration tower and carries out reduced pressure fractionation, the N-methyl pyrrolidone fraction is evaporated from the top of the plate type recovery tower and is recovered to a N-methyl pyrrolidone raw material tank in polyphenylene sulfide production, a small amount of heavy components are discharged from the bottom of the plate type recovery tower, the theoretical plate number of the plate type recovery tower is 23-27, the operation pressure is-74 to-80 Kpa, and the bottom temperature is 167-.

2. The separation and recovery system of claim 1, further comprising: and the incineration device is connected with the bottom of the tower plate type recovery tower through a pipeline and is used for receiving the heavy components discharged from the bottom of the recovery tower and carrying out incineration treatment.

3. The separation and recovery system of claim 1, wherein the packing in the packed column as the stripping column is a pall ring having an average diameter of 16 mm.

4. A method for separating and recovering solvent N-methyl pyrrolidone and raw material p-dichlorobenzene in industrial production of polyphenylene sulfide comprises the following steps:

step 1) mixing reaction mother liquor generated after polyphenylene sulfide production and washing liquor recovered by a washing system to obtain a mixed solution, wherein the main components of the mixed solution are N-methyl pyrrolidone, residual p-dichlorobenzene in reaction and water, and the weight ratio of the N-methyl pyrrolidone to the residual p-dichlorobenzene in reaction is about 45-50:0.5-0.7:110-118, preferably 48:0.6: 114;

step 2) sending the mixed solution obtained in the step 1) to a plate type dehydrating tower for distillation separation, evaporating water and p-dichlorobenzene from the top of the dehydrating tower and condensing at the pressure of 48-52Kpa and the temperature of 215-225 ℃, and discharging crude N-methyl pyrrolidone from the bottom of the dehydrating tower;

step 3) condensing the tower top product of the tower plate type dehydrating tower in the step 2), and then sending the condensed tower top product into a horizontal settling tank, wherein the p-dichlorobenzene and the water are gradually layered after a certain retention time in the tank because the p-dichlorobenzene is insoluble in water, and the separated p-dichlorobenzene and the water are discharged after opening a valve according to the accumulation condition of the liquid level to more than 80% of the volume in the tank, so that the purity of the separated p-dichlorobenzene can reach 99.5%, and the separated p-dichlorobenzene is recycled into a p-dichlorobenzene raw material tank in the production of polyphenylene sulfide to be used as a raw material;

step 4), the water phase separated by the horizontal settling tank in the step 3) contains trace p-dichlorobenzene, part of the water is sent to a stripping tower, the stripping tower is stripped by adopting circulating steam to remove the trace p-dichlorobenzene, the recovered p-dichlorobenzene is recycled to the horizontal settling tank in the step 3), the water recovered from the bottom of the stripping tower can be returned to a washing system for polyphenylene sulfide production for reuse, wherein the steam flow in the stripping tower is 0.55-0.65t/h, the stripping steam temperature is 218-230 ℃, and the steam pressure is 0.9-1.0 Mpa;

and 5) sending the crude NMP obtained in the step 2) to a plate tower type recovery tower for reduced pressure fractionation, purifying the crude NMP at a certain temperature and pressure, evaporating azomethyl pyrrolidone fraction from the top of the plate tower type recovery tower to reach 99.9% of purity, recovering the azomethyl pyrrolidone fraction to a raw material tank of azomethyl pyrrolidone in polyphenylene sulfide production, and discharging a small amount of heavy components from the bottom of the recovery tower.

5. The separation and recovery method according to claim 4, further comprising:

and 6) burning the heavy components discharged from the bottom of the plate type recovery tower in the step 5).

Technical Field

The invention belongs to the field of chemical industry, and particularly relates to a separation and recovery system and a separation and recovery method for solvent N-methyl pyrrolidone (NMP) and raw material p-Dichlorobenzene (DCB) in a pilot-scale production device of polyphenylene sulfide.

Background

Polyphenylene sulfide has excellent heat resistance, flame retardance and insulativity, and is high in hardness and strength, so that the polyphenylene sulfide is a special engineering plastic with the highest cost performance in the world so far, and becomes the first large variety of the special engineering plastic. The method is mainly applied to the fields of automobiles, environmental protection, electronics, electricity, machinery, petrifaction, war industry, aerospace and the like. With the progress of science and technology and the rapid development of economy, the application of polyphenylene sulfide products in other fields is also increasingly wide, and the market potential is huge. China polyphenylene sulfide is also gradually developed, and as the technology is monopolized by western countries, compared with Japan, America and other countries, domestic polyphenylene sulfide still needs to be further improved in the aspects of product quality, production process stability and the like, and particularly becomes a technical difficulty in the aspects of solvent and auxiliary agent recovery.

NMP is often used as a solvent in the process of synthesizing polyphenylene sulfide (PPS), and the NMP is large in usage amount and expensive, so that the research on the NMP recovery process is particularly important. A large amount of deionized water is also used for washing and purifying in the post-treatment process of the polyphenylene sulfide, so that the recovery process of the solvent and the washing water after the reaction is finished is an important link for reducing the cost and enhancing the enterprise competitiveness. At present, two NMP recovery methods are mainly available in China: one method is to recover NMP by rectifying the recovered solution containing NMP by utilizing different boiling points of substances in the recovered solution, the method can obtain the NMP with higher purity, but the higher temperature can cause partial decomposition of the NMP in the rectifying and recovering process because the boiling point of the NMP is higher; one is to obtain NMP with high purity by an extraction method by utilizing the property that NMP has strong polarity and is insoluble in a nonpolar organic solvent but soluble in a polar solvent (such as chloroform), but the method easily causes deviation of a recovery environment from neutrality in a process of recovering NMP, and causes a problem of low NMP recovery rate.

Disclosure of Invention

Aiming at the problem that the existing polyphenylene sulfide production technology has low efficiency in the aspect of solvent recovery and causes high cost in the aspects of solvent, raw material and product post-treatment in the production of polyphenylene sulfide, the invention aims to provide a system for effectively separating and recovering azomethyl pyrrolidone, raw material p-dichlorobenzene and washing water from a solvent NMP and a raw material p-dichlorobenzene in the industrial production of polyphenylene sulfide by means of reduced pressure distillation and the like.

The separation and recovery system of the solvent N-methyl pyrrolidone (NMP) and the raw material p-Dichlorobenzene (DCB) comprises:

a plate type dehydration tower which receives a mixed solution of reaction mother liquor produced by polyphenylene sulfide and washing liquor recovered by a washing system through a pipeline and separates the mixed solution by distillation, wherein water and p-dichlorobenzene are evaporated and condensed from the top of the plate type dehydration tower, crude N-methyl pyrrolidone is discharged from the bottom of the dehydration tower, the theoretical plate number of the plate type dehydration tower is 33-37, the operation pressure is 48-52Kpa, and the temperature is 215-225 ℃;

the horizontal settling tank is connected with the top of the tower plate type dehydrating tower through a pipeline, receives water and p-dichlorobenzene evaporated and condensed from the top of the tower plate type dehydrating tower, separates the water and the p-dichlorobenzene, and recovers the separated p-dichlorobenzene to a p-dichlorobenzene raw material tank in the production of the polyphenylene sulfide, wherein the operation pressure of the horizontal settling tank is 8-12Kpa, the temperature is 90-100 ℃, and the valve is opened according to the accumulation condition of the liquid level in the tank body until the volume in the tank body is more than 80 percent for discharging;

the stripping tower is connected with the horizontal settling tank through a pipeline, receives water separated from the horizontal settling tank, adopts circulating steam to strip and remove trace p-dichlorobenzene in the water separated from the horizontal settling tank, the recovered p-dichlorobenzene is recycled to a raw material tank for polyphenylene sulfide production, and the water collected from the stripping tower is conveyed to a liquid storage tank for recycling, wherein the stripping tower is a packed tower, the height of the packing is 4-5 meters, the operating pressure is 13-17Kpa, and the temperature is 98-104 ℃;

and the plate type recovery tower is connected with the bottom of the plate type dehydration tower through a pipeline, receives crude N-methyl pyrrolidone discharged from the bottom of the plate type dehydration tower and carries out reduced pressure fractionation, the N-methyl pyrrolidone fraction is evaporated from the top of the plate type recovery tower and is recovered to a N-methyl pyrrolidone raw material tank in polyphenylene sulfide production, a small amount of heavy components are discharged from the bottom of the plate type recovery tower, the theoretical plate number of the plate type recovery tower is 23-27, the operation pressure is-74 to-80 Kpa, and the bottom temperature is 167-.

Preferably, the system for separating and recovering the solvent N-methylpyrrolidone (NMP) and the raw material p-Dichlorobenzene (DCB) according to the invention further comprises: and the incineration device is connected with the bottom of the tower plate type recovery tower through a pipeline and is used for receiving the heavy components discharged from the bottom of the recovery tower and carrying out incineration treatment.

Preferably, the packing in the packed column as the stripping column may be pall rings with an average diameter of 16 mm.

According to another aspect of the present invention, it is another object of the present invention to provide a method for effectively separating and recovering a solvent of N-methylpyrrolidone, p-dichlorobenzene as a raw material, and water as washing water by distillation under reduced pressure or the like for NMP as a solvent in industrial production of polyphenylene sulfide, comprising the steps of:

step 1) mixing reaction mother liquor generated after polyphenylene sulfide production and washing liquor recovered by a washing system to obtain a mixed solution, wherein the main components of the mixed solution are N-methyl pyrrolidone, residual p-dichlorobenzene in reaction and water, and the weight ratio of the N-methyl pyrrolidone to the residual p-dichlorobenzene in reaction is about 45-50:0.5-0.7:110-118, preferably 48:0.6: 114;

step 2) sending the mixed solution obtained in the step 1) to a plate type dehydrating tower for distillation separation, evaporating water and p-dichlorobenzene from the top of the dehydrating tower and condensing at the pressure of 48-52Kpa and the temperature of 215-225 ℃, and discharging crude N-methyl pyrrolidone from the bottom of the dehydrating tower;

step 3) condensing the tower top product of the tower plate type dehydrating tower in the step 2), and then sending the condensed tower top product into a horizontal settling tank, wherein the p-dichlorobenzene and the water are gradually layered after a certain retention time in the tank because the p-dichlorobenzene is insoluble in water, and the separated p-dichlorobenzene and the water are discharged after opening a valve according to the accumulation condition of the liquid level to more than 80% of the volume in the tank, so that the purity of the separated p-dichlorobenzene can reach 99.5%, and the separated p-dichlorobenzene is recycled into a p-dichlorobenzene raw material tank in the production of polyphenylene sulfide to be used as a raw material;

step 4), the water phase separated by the horizontal settling tank in the step 3) contains trace p-dichlorobenzene, part of the water is sent to a stripping tower, the stripping tower is stripped by adopting circulating steam to remove the trace p-dichlorobenzene, the recovered p-dichlorobenzene is recycled to the horizontal settling tank in the step 3), the water recovered from the bottom of the stripping tower can be returned to a washing system for polyphenylene sulfide production for reuse, wherein the steam flow in the stripping tower is 0.55-0.65t/h, the stripping steam temperature is 218-230 ℃, and the steam pressure is 0.9-1.0 Mpa;

and 5) sending the crude NMP obtained in the step 2) to a plate tower type recovery tower for reduced pressure fractionation, purifying the crude NMP at a certain temperature and pressure, evaporating azomethyl pyrrolidone fraction from the top of the plate tower type recovery tower to reach 99.9% of purity, recovering the azomethyl pyrrolidone fraction to a raw material tank of azomethyl pyrrolidone in polyphenylene sulfide production, and discharging a small amount of heavy components from the bottom of the recovery tower.

Preferably, the separation and recovery method according to the present invention further comprises:

and 6) burning the heavy components discharged from the bottom of the plate type recovery tower in the step 5).

And (3) performance testing:

in the above separation and recovery method, both the DCB content in step 3) and the NMP content in step 5) can be measured by gas chromatography.

Advantageous effects

The recovery separation system and method of the present invention have studied and designed the recovery process of solvent NMP and raw material DCB in the reaction mother liquor and filtrate generated in the production of PPS by polycondensation. Has the following advantages:

1. the recovery and separation method provided by the invention is simple to operate and low in cost.

2. Basically gets through the NMP recovery process route with high recovery rate, reliability and environmental protection, and solves the problems of easy decomposition, low recovery rate and the like when the solvent is recovered in the production process of PPS.

3. The recovered azomethyl pyrrolidone and p-dichlorobenzene have high purity, and can recycle the solvent NMP and recycle the residual raw material p-dichlorobenzene in the PPS production process.

4. The recovered water can be used as polyphenylene sulfide washing water for recycling, so that the waste water generated in the process is effectively reduced, and the sewage treatment cost is reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a process flow diagram showing a separation recovery method according to the present invention;

FIG. 2 is a chromatogram showing the recovery of NMP according to example 1;

FIG. 3 is a diagram showing the chromatographic analysis of DCB recovery according to example 1;

FIG. 4 is a diagram showing chromatography on NMP according to example 2;

FIG. 5 is a chromatogram showing the recovery of DCB according to example 2;

FIG. 6 is a chromatogram showing the recovery of NMP according to example 3;

FIG. 7 is a diagram showing the chromatographic analysis of DCB recovery according to example 3;

Detailed Description

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Accordingly, the description herein is of preferred examples for the purpose of illustration only and is not intended to limit the scope of the present invention, so it will be understood that other equivalent implementations and modifications may be made without departing from the spirit and scope of the present invention.

The system for separating and recovering the solvent N-methyl pyrrolidone (NMP) and the raw material p-Dichlorobenzene (DCB) is in a continuous operation mode, and can effectively recover NMP, DCB and water washing water in part of the reaction mother liquor and the product washing liquor before. In a tower plate type dehydration tower, water and DCB are evaporated from the top of the tower, condensed and conveyed to a horizontal settling tank, the DCB is insoluble in water, kept in the horizontal settling tank for a certain time, and discharged after the liquid level is accumulated to more than 80% of the volume in the tank, so that the separation of the DCB in the horizontal settling tank is realized. The aqueous phase separated from the horizontal settling tank then contains traces of DCB, is sent to the stripper where it is stripped with live steam to remove traces of DCB, and the recovered DCB is recycled to the DCB feed tank. The collected water can be returned to the process system for reuse. And discharging from the bottom of the plate type dehydration tower, sending to a recovery tower, and evaporating NMP from the top of the plate type recovery tower. A small amount of heavy components discharged from the bottom of the tray recovery column is sent to an incineration unit.

The operation parameters of each apparatus are determined by trial and error, and when the operation parameters are within the range described below according to the present invention, there are problems that the operation energy consumption is increased or the separation effect is deteriorated, and therefore, the operation parameters of each apparatus described below cannot be changed at will.

For example, in the plate-type dehydration tower, the theoretical plate number is 33-37, the operation pressure is 48-52Kpa, and the temperature is 215-225 ℃; the operating pressure of the horizontal settling tank is 8-12Kpa, and the temperature is 90-100 ℃; the stripping tower is a packed tower, the height of the packing is 4-5 m, the operating pressure is 13-17Kpa, and the temperature is 98-104 ℃; the theoretical plate number of the plate-type recovery tower is 23-27, the operation pressure is-74 to-80 Kpa, and the tower bottom temperature is 167-.

The following examples are given by way of illustration of embodiments of the invention and are not to be construed as limiting the invention, and it will be understood by those skilled in the art that modifications may be made without departing from the spirit and scope of the invention. Unless otherwise specified, reagents and equipment used in the following examples are commercially available products.