阅读说明：本技术 从包含未反应单体的混合物溶液中分离未反应单体的方法 (Method for separating unreacted monomer from mixture solution containing unreacted monomer ) 是由 李在益 俞成镇 李政锡 金美冏 于 2018-12-24 设计创作，主要内容包括：本发明涉及一种未反应单体的节能分离方法,以及能够进行该分离方法的分离系统,通过所述分离方法,可以容易地从包含未反应单体的混合物溶液中回收未反应单体。(The present invention relates to an energy-saving separation method of kinds of unreacted monomers, by which the unreacted monomers can be easily recovered from a mixture solution containing the unreacted monomers, and a separation system capable of performing the separation method.)

A process for the separation of unreacted monomers, the process comprising:

1) injecting a mixture solution containing an unreacted monomer, an aprotic polar solvent and water into an -th distillation column, recovering a -th fraction containing the unreacted monomer and a -th water fraction from the top of the column, and recovering a second fraction containing the aprotic polar solvent and a second water fraction from the bottom of the column, and

2) feeding said th fraction to a second distillation column, recovering a water-enriched fraction from the top of the column and a fraction enriched in unreacted monomers from the bottom of the column,

wherein heat is exchanged between at least portion of the fraction enriched in unreacted monomer and at least portion of the th fraction.

2. The separation process of unreacted monomers of claim 1, wherein said heat exchange is carried out by a temperature difference between said at least portion of said fraction enriched in unreacted monomers and said at least portion of said fraction.

3. The separation process of unreacted monomers of claim 1, wherein said at least portion of said th fraction has a temperature that is 10 ℃ to 20 ℃ higher than said at least portion of said fraction enriched in unreacted monomers prior to said heat exchange.

4. The separation process of unreacted monomers of claim 1, wherein, after said heat exchange, said at least portion of said th fraction is condensed and reintroduced into the overhead of said th distillation column.

5. The separation method of unreacted monomers of claim 1, wherein said at least portion of said fraction enriched in unreacted monomers is recovered from said fraction enriched in unreacted monomers after said heat exchange.

6. The method for separating an unreacted monomer according to claim 1, wherein a vapor generated by the heat exchange is used as a heat source of the second distillation column.

7. The method for separating an unreacted monomer according to claim 1, wherein the unreacted monomer contains 70% by weight or more of acrylonitrile.

8. The method for separating an unreacted monomer according to claim 1, wherein the fraction enriched in an unreacted monomer contains 90% by weight or more of the unreacted monomer.

9. The method for separating an unreacted monomer according to claim 1, wherein the recovery rate of the unreacted monomer in the separation method is 99% or more.

10. The method for separating an unreacted monomer according to claim 1, wherein the water-enriched fraction recovered from the top of the second distillation column is recycled to the -th distillation column.

11. The method for separating an unreacted monomer according to claim 1, wherein the mixture solution is a waste liquid generated in a process for producing polyacrylonitrile-based fiber.

A separation system for unreacted monomers, the separation system comprising:

an th distillation column for separating a th fraction containing an unreacted monomer containing acrylonitrile and a th water fraction and a second fraction containing an aprotic polar solvent and a second water fraction from a mixture solution containing the unreacted monomer, the aprotic polar solvent and water;

a second distillation column for separating a water-enriched fraction and a fraction enriched in unreacted monomers from said th fraction, and

a heat exchanger disposed between the top of the th distillation column and the bottom of the second distillation column,

wherein the heat exchanger is connected to the top of the distillation column through an th fraction recycle line and to the bottom of the second distillation column through a fraction recovery line enriched in unreacted monomer.

13. The separation system according to claim 12, wherein a supply line for supplying the mixture solution is provided on a side of the th distillation column, and on another side of the th distillation column, a th fraction flow line is provided at the top of the column, a second fraction flow line is provided at the bottom of the column,

the side of the second distillation column was connected to the top of the th distillation column through the th fraction flow line, and on the other side of the second distillation column, a water-enriched fraction recycle line for recycling the water-enriched fraction to the th distillation column was provided at the top of the second distillation column, and a fraction recovery line enriched in unreacted monomer was provided at the bottom of the second distillation column.

Technical Field

Cross Reference to Related Applications

This application claims the benefit of korean patent application No. 10-2017-.

Background

PAN-based fibers have a high melting point due to the high polarity of nitrile groups and a bonding mechanism and a crosslinking mechanism between dipoles generated thereby, and is widely used as a precursor of carbon fibers.

PAN-based fibers are produced by polymerizing a monomer raw material containing acrylonitrile as a main component, dissolving the polymer thus obtained in an aprotic polar solvent to prepare a polymer solution, spinning the polymer solution in a coagulation bath containing an aqueous coagulation liquid, and washing if necessary. In this case, the unreacted monomers not participating in the reaction are discharged and mixed with the aprotic polar solvent and the aqueous coagulation liquid in the coagulation bath and remain.

The unreacted monomer is a loss of raw materials and becomes a factor of increasing the manufacturing cost. Costs are also incurred and economic feasibility is reduced in the case of discarding the unreacted monomer. Therefore, in order to improve the economic feasibility of PAN-based fibers in the manufacturing process, it is necessary to establish a technique for recovering and recycling the unreacted monomers.

Therefore, in the PAN-based fiber production method, a method for recovering and recycling the unreacted monomer is being studied.

For example, Japanese laid-open patent No.2000-044606A proposes recovery methods for evaporating an unreacted monomer from a polymerization solution before spinning, and Japanese laid-open patent No.2000-336115A proposes methods for directly recycling a waste liquid containing the recovered unreacted monomer as a raw material without separation.

In addition, the aqueous condensate in the waste liquid forms an azeotrope with the unreacted monomer and it is difficult to separate each pure component by simple distillation.

Therefore, in order to ensure the economic feasibility of the PAN-based fiber production process, it is necessary to develop methods for easily separating and recovering the unreacted monomers as pure components from the waste liquid generated in the PAN-based fiber production process without consuming excessive energy.

Disclosure of Invention

Technical problem

An aspect of the present invention is to solve the limitations of the prior art and to provide an energy-saving method of separating unreacted monomers, by which the unreacted monomers can be easily separated and recovered from a mixture solution containing the unreacted monomers such as acrylonitrile, for example, a waste liquid generated in a process of producing polyacrylonitrile-based fibers.

Another aspect of the invention is to provide separation systems capable of performing a separation process of unreacted monomers.

Technical scheme

In order to solve the above-mentioned task, there is provided a separation method of unreacted monomers, comprising a step of injecting a mixture solution containing unreacted monomers, an aprotic polar solvent and water into a th distillation column, recovering a th fraction containing the unreacted monomers and a th water fraction from the top of the column and recovering a second fraction containing the aprotic polar solvent and a second water fraction from the bottom of the column (step 1), and a step of injecting the th fraction into a second distillation column, recovering a water-enriched fraction from the top of the column and recovering an unreacted monomer-enriched fraction from the bottom of the column (step 2), wherein heat exchange is performed between at least part of the unreacted monomer-enriched fraction and at least part of the th fraction.

Further, the present invention provides separation systems of unreacted monomers, comprising a distillation column for separating a th fraction containing unreacted monomers and a th water fraction and a second fraction containing aprotic polar solvent and a second water fraction from a mixture solution containing unreacted monomers containing acrylonitrile, aprotic polar solvent and water, a second distillation column for separating a fraction enriched in water and a fraction enriched in unreacted monomers from the th fraction, and a heat exchanger disposed between a column top of the th distillation column and a column bottom of the second distillation column, wherein the heat exchanger is connected to the column top of the distillation column through a fraction circulation line and to the column bottom of the second distillation column through a fraction recovery line enriched in unreacted monomers.

Advantageous effects

By the separation method of unreacted monomers according to the present invention, unreacted monomers in a pure state in a non-mixture state can be recovered from a mixture solution containing the unreacted monomers, for example, a waste liquid generated in a production process of polyacrylonitrile-based fibers, and at least part of fraction is condensed and easily refluxed by heat exchange between at least part of fraction recovered from the top of distillation column and at least part of fraction enriched in unreacted monomers recovered from the bottom of second distillation column, and by using the thus-generated steam as a heat source of the second distillation column, calories used in condensers and reboilers can be reduced and process efficiency can be improved.

Drawings

The following drawings attached to the specification describe preferred embodiments of the present invention by way of example and serve to further the technical idea of the present invention together with a detailed description of the present invention given below, so that the present invention should not be understood as being limited to only matters in these drawings.

Fig. 1 schematically shows a separation system for separating and recovering an unreacted monomer from a mixture solution containing the unreacted monomer, an aprotic polar solvent and water according to embodiments of the present invention;

fig. 2 schematically illustrates a separation system for separating and recovering an unreacted monomer from a mixture solution including the unreacted monomer, an aprotic polar solvent, and water according to a comparative example of the present disclosure.

[ description of reference numerals ]

10,100: separation system

21,41 th th distillation column

22,42: second distillation column

11,31: supply line

12, 32: fraction flow line

13,33: second fraction flow line

14,34: water-enriched distillate recycle line

15,35: fraction recovery line enriched in unreacted monomers

50: heat exchanger

51: th fraction recycle line

52: steam introduction line

Detailed Description

Hereinafter, the present invention will be described in more detail to enable understanding of the present invention.

The words or terms used in the specification and claims should not be construed as having meanings defined in common dictionaries based on the principle that an inventor can properly define the meanings of the words or terms to best describe the present invention, the words or terms should be construed as having meanings corresponding to their meanings in the technical idea of the present invention.

For example, th water fraction and a second water fraction indicate that the amount of water is divided into two groups, being the th water fraction and being the second water fraction.

As used herein, the term "… … -enriched fraction" refers to a fraction comprising a particular component in a high proportion relative to other components in a fraction or mixture of components.A -enriched water fraction, for example, refers to a fraction comprising water in a high proportion relative to other components in the components comprising the fraction.

The term "azeotrope" as used in the present invention means a mixture in which the gas composition and the liquid composition are the same. Generally, in the case of distilling a mixture solution containing two or more components, the composition may be changed according to the boiling thereof, and thus, the two components may be separated. In contrast, azeotropes boil at a constant temperature without changing the composition, and the compositions of the gas and liquid become the same, and therefore, the components cannot be separated by simple distillation.

The present invention provides separation methods of unreacted monomers for recovering and recycling the unreacted monomers in a pure state in a non-mixture state from a mixture solution containing the unreacted monomers such as acrylonitrile and water which can form an azeotrope therewith, specifically, a waste liquid generated in a production process of polyacrylonitrile-based fibers, by which the unreacted monomers are easily separated and energy is saved.

In general, polyacrylonitrile-based fibers are prepared by polymerizing a monomer raw material containing acrylonitrile as a main component, dissolving the thus-obtained polymer in an aprotic polar solvent to prepare a polymer solution, discharging the thus-prepared polymer solution into a coagulation bath containing water through a spinning nozzle, and treating the polymer solution that has been spun into the coagulation bath with a diffusion process of a solvent and a non-solvent to precipitate and gel the polymer.

In addition, in the waste liquid, the aprotic polar solvent used in the process of preparing the polymer solution before spinning and water used as the aqueous condensate are contained together with the unreacted monomer , and since the difference in boiling points of the aprotic polar solvent and the unreacted monomer is large and can be easily separated by distillation, but since water forms an azeotrope with the unreacted monomer, the separation thereof cannot be achieved by simple distillation.

Therefore, in the production process of polyacrylonitrile-based fibers, in order to improve economic feasibility without lowering process efficiency, it is necessary to establish a technology of separating unreacted monomers from water and recovering and recycling the unreacted monomers in a pure state without consuming much energy.

Accordingly, the present invention provides a separation method of kinds of unreacted monomers, by which the unreacted monomers can be easily recovered in a pure state from a mixture solution comprising the unreacted monomers, water which can form an azeotrope therewith, and an aprotic polar solvent, and energy consumption can be reduced.

Here, the mixture solution may be a waste liquid generated in the production process of polyacrylonitrile-based fibers, and the separation method of the unreacted monomer may be used as a method of recycling the unreacted monomer in the production process of polyacrylonitrile-based fibers.

The separation process of the unreacted monomers according to the embodiments of the present invention is characterized by comprising injecting a mixture solution comprising the unreacted monomers, the aprotic polar solvent and water into a th distillation column, recovering a th fraction comprising the unreacted monomers and a th water fraction from the top of the column, recovering a second fraction comprising the aprotic polar solvent and a second water fraction from the bottom of the column (step 1), and injecting the th fraction into a second distillation column, recovering a water-enriched fraction from the top of the column, and recovering an unreacted monomer-enriched fraction from the bottom of the column (step 2), wherein heat exchange is performed between at least part of the unreacted monomer-enriched fraction and at least part of the th fraction.

In the present invention, the mixture solution may represent a waste liquid (residual solution) generated in a production process of polyacrylonitrile-based fibers, specifically, polyacrylonitrile-based fibers are produced by polymerizing a monomer raw material having acrylonitrile as a main component to produce a polymer, dissolving the polymer in an aprotic polar solvent to produce a spinning solution, and spinning the spinning solution into a coagulation bath containing an aqueous coagulation liquid. In this case, the solution remaining in the coagulation bath after spinning may be a mixture solution. In addition, in the case of washing the acrylic fiber produced after spinning, the mixture solution may contain a solution remaining after washing.

Therefore, in the mixture solution, in addition to the unreacted monomer that does not participate in the polymerization, an aprotic polar solvent used in the preparation of the polymer solution and water used as an aqueous condensate may be contained.

In addition, in the present invention, the unreacted monomer may mean a monomer that does not participate in polymerization among monomer raw materials used in a preparation process of the polyacrylonitrile-based fiber, and the monomer raw materials may include acrylonitrile as a main component, and may further include a comonomer, as required.

In addition, in the case where the unreacted monomer includes acrylonitrile and a comonomer, the unreacted monomer may include 70% by weight or more, specifically 95% by weight or more of acrylonitrile.

In addition, the aprotic polar solvent may be any kinds used in the art for the same purpose without particular limitation, and may be, for example, dimethyl sulfoxide (DMSO), Dimethylacetamide (DMAC), or Dimethylformamide (DMF).

Step 1 is a distillation step of separating a th fraction containing unreacted monomer and an th water fraction and a second fraction containing aprotic polar solvent and a second water fraction from a mixture solution containing unreacted monomer, aprotic polar solvent and water, and the mixture solution may be injected into a th distillation column and distilled, a th fraction containing unreacted monomer and a th water fraction is recovered from the top of the column, and the second fraction containing aprotic polar solvent and a second water fraction is recovered from the bottom of the column.

Further, the fraction separated by the th distillation step contains unreacted monomers and the th water fraction and, according to circumstances, may contain a trace amount of aprotic polar solvent, but even if contained, its amount is less than 0.5% by weight.

Step 2 is a second distillation step of separating the water-enriched fraction and the unreacted monomer-enriched fraction from the th fraction, and the th fraction may be injected into a second distillation column, recovering the water-enriched fraction from the top of the column and the unreacted monomer-enriched fraction from the bottom of the column.

The fraction enriched in unreacted monomer can comprise greater than 90 weight percent, specifically greater than 95 weight percent, more specifically 100 weight percent of unreacted monomer. That is, the unreacted monomer fraction separated from the waste liquid by the separation method of the present invention is mainly composed of the unreacted monomer and contains little water, or specifically, is composed of only the unreacted monomer.

Accordingly, in the case where the water-enriched fraction is directly discharged out of the system and recovered, the unreacted monomer may be discharged at , and as a result, economic feasibility may be reduced.A separation method according to embodiments of the present invention may include recycling the water-enriched fraction recovered from the overhead of the second distillation column to the th distillation column, and thus, recovery rate of the unreacted monomer may be increased by being reintroduced to the th distillation step.

Meanwhile, the separation and recovery of unreacted monomers from the waste liquid is generally performed through a distillation column, and in order to improve the recovery efficiency, a condenser is provided at the top of the distillation column for reflux and a reboiler is provided at the bottom to supply a heat source required for distillation.

The separation process of the unreacted monomers according to embodiments of the present invention can improve process efficiency by heat exchange of at least portion of the th fraction recovered from the overhead of the th distillation column with at least portion of the unreacted monomer-enriched fraction recovered from the bottom of the second distillation column.

In particular, the separation process may comprise a step of heat exchange of at least part of the fraction enriched in unreacted monomer with at least part of the fraction, in which case said heat exchange may be carried out by a temperature difference between at least part of unreacted monomer and at least part of the fraction.

In this case, the temperature difference may be 20 ℃ or less, specifically, 10 ℃ to 20 ℃.

In addition, after heat exchange, at least portion of the th fraction can be condensed and reintroduced to the overhead of the th distillation column, and the at least portion of the unreacted monomer-enriched fraction can be recovered with the unreacted monomer-enriched fraction .

The term "at least fractions" as used herein means fractions or more in total, for example, in the case of 10 portions, at least portions or more, at least portions of the th fraction may represent portions of the th fraction or all of the th fraction.

Meanwhile, the separation method according to embodiments of the present invention may be performed by a continuous process circulating two or more times.

Here, "loop" means a loop in which the same process is repeated a plurality of times. For example, steps 1 and 2 of the separation method may be repeated a plurality of times in sequence.

That is, during the initial th cycle, the th distillation column may condense and reflux at least of the th fraction through a separately disposed condenser and the second distillation column may provide a heat source through a separately disposed reboiler.

By the separation method according to embodiments of the present invention, the recovery rate of the separated unreacted monomers can be 99% or more.

Here, the recovery rate of the unreacted monomer represents a ratio of the amount of the unreacted monomer in the recovered unreacted monomer fraction to the amount of the unreacted monomer contained in the mixture solution, and may be a calculated value by the following mathematical formula 1:

[ mathematical formula 1]

Recovery rate (%) of the unreacted monomer { (amount of unreacted monomer (g) }/{ amount of unreacted monomer (g) } in the mixture solution) × 100

Meanwhile, the separation method of the unreacted monomers according to embodiments of the present invention may be performed using a separation system to be described later.

The present invention provides separation systems of unreacted monomers, by which the unreacted monomers can be separated and recovered from a mixture solution containing the unreacted monomers, an aprotic polar solvent and water.

A separation system according to embodiments of the present invention includes a distillation column for separating a th fraction containing unreacted monomer and a th water fraction and a second fraction containing aprotic polar solvent and a second water fraction from a mixture solution containing unreacted monomer containing acrylonitrile, aprotic polar solvent and water, a second distillation column for separating a water-enriched fraction and an unreacted monomer-enriched fraction from the th fraction, and

a heat exchanger disposed between the top of the th distillation column and the bottom of the second distillation column,

wherein the heat exchanger is connected to the top of the th distillation column through an th fraction recycle line and to the bottom of the second distillation column through a fraction recovery line enriched in unreacted monomer.

Hereinafter, the separation system will be described specifically with reference to fig. 1.

Fig. 1 schematically shows a separation system of an unreacted monomer according to embodiments of the present invention, which can be used to separate and recover the unreacted monomer from a mixture solution containing the unreacted monomer, an aprotic polar solvent, and water.

As shown in fig. 1, the separation system 100 according to embodiments of the present invention includes a th distillation column 41, a second distillation column 42, and a heat exchanger 50 disposed between the top of the th distillation column and the bottom of the second distillation column, and a reboiler may be disposed at the bottom of the th distillation column and a condenser may be disposed at the top of the second distillation column.

The th distillation column 41 is used to separate a 0 th fraction containing unreacted monomer and th water fraction and a second fraction containing aprotic polar solvent and a second water fraction from a mixture solution containing unreacted monomer, aprotic polar solvent and water, wherein a supply line 31 for supplying the mixture solution may be provided on the side, and on the other side, a th fraction flow line 32 and an th fraction circulation line 51 may be provided on the top thereof, and a second fraction flow line 33 may be provided on the bottom thereof, the th fraction circulation line 51 may be connected to the th fraction flow line 32 or to the top of the th distillation column 41 separately from the th fraction flow line 32.

The second distillation column 42 is for separating a water-enriched fraction and a fraction enriched in unreacted monomers from the th fraction, wherein a side portion of the second distillation column 42 may be connected to the top of the th distillation column 41 through a th fraction flow line 32, and on the other side portion, a water-enriched fraction recycle line 34 may be disposed at the top thereof, and a fraction recovery line 35 enriched in unreacted monomers and a vapor introduction line 52 may be disposed at the bottom thereof.

Further, a heat exchanger 50 may be provided between the top of the th distillation column 41 and the bottom of the second distillation column 42, and the heat exchanger 50 may be connected to the top of the th distillation column 41 through a th fraction recycling line 51 and to the bottom of the second distillation column through a fraction recovering line 35 rich in the unreacted monomer the fraction recovering line 35 rich in the unreacted monomer may be extended at the bottom of the second distillation column 42 and may be connected to the outside of the system through the heat exchanger 50.

In the case of performing the separation method of the unreacted monomers according to embodiments of the present invention using the above-described separation system, a mixture solution containing the unreacted monomers, the aprotic polar solvent and water, for example, a waste liquid generated in the production process of polyacrylonitrile-based fibers is introduced into the -th distillation column 41 through the mixture solution supply line 31 and separated into a -th fraction containing the unreacted monomers and the -th water fraction and a second fraction containing the aprotic polar solvent and the second water fraction, the -th fraction is sent from the overhead of the -th distillation column 41 to the second distillation column 42 through the -th fraction flow line 32, and the second fraction is discharged from the bottom of the -th distillation column 41 to the outside of the system through the second fraction flow line 33.

The th fraction fed to the second distillation column 42 is separated into a fraction enriched in unreacted monomer and a fraction enriched in water, and the fraction enriched in unreacted monomer is fed to the outside of the system through the unreacted monomer-enriched fraction recovery line 35 and recovered at the bottom of the second distillation column 42, and the water-enriched fraction is fed to the top of the th distillation column 41 through the water-enriched fraction recycle line 34 in this case, at least a portion of the 1 th fraction fed from the top of the 0 th distillation column 41 to the second distillation column 42 is fed to the heat exchanger 50 through the th fraction recycle line 51, at least a portion of the unreacted monomer-enriched fraction fed from the bottom of the second distillation column 42 is fed to the heat exchanger 50 through the unreacted monomer-enriched fraction recovery line 35 for heat exchange with each other, the at least a portion of the th fraction is condensed and reintroduced into the th distillation column 41, and the at least the th portion of the unreacted monomer-enriched fraction is recycled to the remaining unreacted monomer-enriched fraction through the heat exchange line to the outside of the second distillation column 42 to be used as a heat source for steam heat exchange with the second distillation column 42.

Hereinafter, the present invention will be described more specifically by embodiments. However, the following embodiments are to more specifically describe the present invention, and the scope of the present invention is not limited thereto.

In the following examples and comparative examples, the separation process according to the invention was simulated using the commercial process simulation program ASPEN PLUS. The constants required for the simulation are values contained in the program, values described in the literature, and the like.

In this case, the mixture solution is set to contain acrylonitrile or methyl acrylate as an unreacted monomer, dimethyl sulfoxide as an aprotic polar solvent, and water.