KR20180079701A - Apparatus and method for purifying solvent - Google Patents

Abstract

The purpose of the present invention is to provide an apparatus and a method for purifying a solvent, the apparatus and the method which can reduce an energy consumption amount while maintaining excellent separation efficiency. More specifically, the apparatus for purifying a solvent includes: a polymerization solution supply unit supplying a polymerization solution to purify the solvent existing in a by-product produced in the solution polymerization process of a thermoplastic elastomer; a multistage distillation column having n number of columns to separate the polymerization solution into tower top components, top side cut components and tower bottom components through fractional distillation; a first heat exchanger positioned between the polymerization solution supply unit and the multistage distillation column, and heating the polymerization solution flown in from the polymerization solution supply unit to continuously supply the heated polymerization solution to the multistage distillation column, and providing a heat quantity required for heating through heat exchange with the top side cut components discharged from the multistage distillation column; a second heat exchanger connected to a top side of the multistage distillation column to condense the tower top components discharged from the multistage distillation column; and a third heat exchanger connected to a bottom side of the multistage distillation column to vaporize a portion of the tower bottom components discharged from the multistage distillation column, wherein a polymerization solution inlet is disposed in the multistage distillation column so that the polymerization solution flown into the multistage distillation column from the first heat exchanger is supplied to a position of the multistage distillation column corresponding to 0.11 to 0.4 of the column number n.

Description

[0001] APPARATUS AND METHOD FOR PURIFYING SOLVENT [0002]

The present invention relates to a solvent refining apparatus and a refining method for improving the separation efficiency and reducing the energy and cost of the refining process in separating the solvent, raw material impurities and reaction by-products after solution polymerization of the thermoplastic elastomer.

Thermoplastic elastomer (TPE) is a polymeric material that can be thermally processed and can exhibit rubber properties. Since the thermoplastic elastomer is composed of a soft segment imparting elasticity and a hard segment imparting rigidity, it exhibits the physical properties of the rubber under the conditions of use, and is easily processed and reworked like thermoplastics under molding conditions . Accordingly, thermoplastic elastomers are one of very important synthetic polymers having various commercial applications such as automobile parts, fibers, adhesives, shoes, road pavement, and roof waterproofing.

These thermoplastic elastomers can be divided into olefin series, styrene series, amide series, ester series, urethane series and PVC series resin depending on the material. Of these, styrene series resins are used for automobile parts, medical supplies, adhesives, sealants, Cable jackets, sporting goods, and the like.

Styrenic resins are known to be the most rubber-like elastomers, and are most widely used in the thermoplastic elastomer market due to their wide hardness range, good flexural and abrasion resistance, low density and easy recyclability, accounting for about 40% of the entire market.

Generally, the thermoplastic elastomer can be produced by various polymerization methods such as bulk polymerization, suspension polymerization, and solution polymerization.

Solution polymerization is a method in which monomers are polymerized in a solvent, and there is little problem of polymerization heat or viscosity increase during polymerization, and it is advantageous in that the content, molecular weight and the like of the monomers that define the physical properties of the final polymer can be easily controlled. However, since a large amount of solvent is required in the reaction, a large amount of energy is used in the process for recovering the unreacted monomers and the solvent after the reaction, and there is a problem that the cost or the environmental load is increased.

Various methods have been proposed to improve the above-mentioned conventional solvent recovery process.

For example, Korean Patent Laid-Open Publication No. 2016-0051036 discloses a distillation apparatus and method for separating and recovering a solvent and unreacted monomers used in a polymerization process of a polyolefin elastomer using a separation wall type distillation column.

In addition, Chinese Patent Publication No. 102775267 proposes a method of purifying a solvent using a distillation column during the production of isoprene rubber using a distillation column.

These patents have improved solvent recovery efficiency to some extent, but the effect is not sufficient. Particularly, in the case of the former, time and cost are additionally required by introducing the separation wall type distillation column. Therefore, there is a further need for a stagnant apparatus and method for separating and recovering the solvent used in the thermoplastic elastomer polymerization process with high purity and high efficiency while consuming low energy.

Korean Patent Publication No. 2016-0051036 (May 2016), distillation apparatus Chinese Patent Publication No. 102775267 (June 20, 2012), Method for solvent refining during isoprene rubber production

Accordingly, the present inventors have conducted various studies in order to solve the above-mentioned problems. As a result, in the process of recovering the solvent by distillation using the multi-stage distillation column, when the polymerization solution for solvent recovery is put into the multi- And a plurality of heat exchangers were provided to recover the solvent. As a result, it was possible to effectively separate the high-purity solvent into a liquid phase with less energy.

Accordingly, an object of the present invention is to provide a solvent refining apparatus and a refining method capable of reducing energy consumption while having excellent separation efficiency.

In order to achieve the above object, the present invention provides a method for purifying a solvent present in a by-product produced in a solution polymerization process of a thermoplastic elastomer,

A polymerization solution supply part for supplying a polymerization solution;

A multi-stage distillation column having n number of stages for separating into a column bottom component comprising a column top component comprising a low boiling point material, a top side cut component comprising a solvent, and a high boiling point material through fractional distillation of the polymerization solution;

The polymerization solution supply unit is located between the polymerization solution supply unit and the multi-stage distillation column, and the polymerized solution introduced from the polymerization solution supply unit is heated and continuously supplied to the multi-stage distillation column. The heat amount required for heating is heat-exchanged with the top side cut component discharged from the multi- A first heat exchanger for providing heat through the heat exchanger;

A second heat exchanger connected to the upper side of the multi-stage distillation column to condense the discharged column components; And

And a third heat exchanger connected to the lower side of the multi-stage distillation column and for heating a part of the column bottom components discharged therefrom,

Wherein the polymerization solution inlet of the multi-stage distillation column is arranged such that the polymerization solution flowing into the multi-stage distillation column from the first heat exchanger is supplied at a position of 0.11 to 0.4 of the number n of the multi-stage distillation column.

Wherein the multi-stage distillation column is a continuous multi-stage distillation column having a number n of internal numbers satisfying 10? N? 80 therein.

The multi-stage distillation column has a first outlet for discharging the top side cut component to one side, a second outlet for discharging the exhaust gas from the top side, and a third outlet for discharging the bottom gas component from the bottom side .

The multi-stage distillation column has a first inlet for introducing the solvent separated from the second heat exchanger into one side of the multi-stage distillation column, and a second inlet for introducing the solvent separated from the third heat exchanger into the lower side of the multi- .

The polymerization solution is characterized in that the temperature difference between before and after passing through the first heat exchanger is 40 to 60 ° C.

The top side cut component is characterized in that the temperature difference between before and after passing through the first heat exchanger is -50 to -10 ° C.

And the second heat exchanger is a condenser that condenses a part of the overhead components by heat exchange with the cooling water.

One side of the second heat exchanger is characterized by having a branched piping structure for discharging the low boiling point material and refluxing the solvent to the multi-stage distillation column.

And the third heat exchanger is a reboiler for heat-exchanging part of the column bottom component with water vapor.

The top side cut component is characterized by being a liquid phase or a liquid / gas phase mixture.

The polymerization solution is characterized in that the thermoplastic elastomer produced in the solution polymerization step is removed by a process such as steam stripping, and includes impurities of a raw material, reaction by-products and a solvent.

Further, in order to purify the by-product produced in the solution polymerization process of the thermoplastic elastomer in the solvent using the solvent refining apparatus,

Supplying the polymerization solution from the polymerization solution supply unit to the multi-stage distillation column having n number of stages while being heated through the first heat exchanger;

Discharging the solvent into the topside cut component through fractional distillation of the multi-stage distillation column, discharging the low boiling point substance to the top component, and discharging the high boiling point substance to the bottom component;

Heating the polymerization solution supplied to the multi-stage distillation column through heat exchange through the first heat exchanger; And

The column top portion is condensed through the second heat exchanger to reflux the solvent in the low boiling point material to the multi-stage distillation column in a liquid state, and a part of the column bottom portion is heated through the third heat exchanger to heat the solvent in the high boiling point material to the multi- Comprising the steps of:

Wherein a polymerization solution inlet of the multi-stage distillation column is disposed such that the polymerization solution supplied from the first heat exchanger is supplied at a position 0.11 to 0.4 of the number n of the number n of the multi-stage distillation column.

The apparatus for purifying a solvent according to the present invention has the following advantages.

(1) By increasing the separation efficiency for the low-boiling components by controlling the inlet of the polymerization solution fed to the multi-stage distillation column to a specific position in the middle part of the multi-stage distillation column, The energy consumption can be reduced.

(2) Even when the entire amount of the topside cut component is separated into the liquid phase by heating only the polymerization solution excluding the reflux amount flowing into the multi-stage distillation column, the heat exchange through the first heat exchanger is enabled and the amount of energy consumed in the third heat exchanger is remarkably lowered , The cost can be reduced and the economical efficiency of the process can be improved.

1 is a schematic view of an apparatus for purifying a solvent according to an embodiment of the present invention.
2 is a schematic diagram showing a process of purifying a solvent according to the first embodiment of the present invention.
3 is a schematic diagram showing a process for purifying a solvent according to a second embodiment of the present invention.
4 is a schematic diagram showing a process for purifying a solvent according to Comparative Example 1 of the present invention.
5 is a graph showing the energy consumption of the third heat exchanger according to the position adjustment of the polymerization solution inlet in Examples 1 to 6 and Comparative Example 1 of the present invention.
6 is a graph showing energy consumption of the third heat exchanger according to the position of the polymerization solution inlet in Examples 7 to 11 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can readily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, like reference numerals refer to like elements, and for the convenience of description of the present invention, elements shown in the drawings may be simplified, exaggerated, or omitted as long as they do not affect the rights of the present invention .

Throughout this specification, when an element is referred to as being "connected" to another element, it is intended to include not only "directly connected" but also "indirectly connected" do.

In this specification, the term " piping connection " means a connection through a connection pipe (or pipeline). In this case, the pipe for connection of the piping includes a flow sensor for controlling the flow rate, a mixing valve, a solenoid valve, As shown in FIG. They may be connected to a separate control unit (e.g., a computer, not shown) to control whether or not they are opened or closed.

The present invention relates to a refining apparatus and a refining method for efficiently refining a solvent while reducing the amount of consumed energy from raw material impurities and polymerization by-products in a solution polymerization process of a thermoplastic elastomer.

The method of preparing a thermoplastic elastomer through solution polymerization can produce a polymer having various properties because it can obtain a homogeneous polymer as compared with other polymerization methods and can easily control the monomer content, molecular weight or degree of polymerization. In addition, since the solvent absorbs the heat of polymerization and lowers the viscosity of the polymerization system, there is no problem caused by heat generation or viscosity increase.

However, since a solvent is used in an amount of 4 to 5 times or more as much as the amount of the monomers to be added during the solution polymerization, a large amount of energy is consumed in the process for recovering the solvent and unreacted monomers after the reaction, In addition, since the amount of cooling water or steam used is large, there is a problem that the influence on the environment is great.

The present invention relates to a method for separating a solvent in a by-product obtained by a solution polymerization process of a thermoplastic elastomer, in which both the polymerization solution and reflux components are heated at the time of refining an existing solvent, It is possible to increase the separation efficiency with respect to the low boiling point component by supplying only the polymerization solution to the stage located at the center of the multi-stage distillation column, and to dissolve the entire amount of the topside cut component into the liquid phase and heat- A solvent refining apparatus and a refining method.

1 is a schematic view of an apparatus for purifying a solvent according to an embodiment of the present invention.

Referring to FIG. 1, the apparatus for stagnating a solvent according to an embodiment of the present invention includes a polymerization solution supply unit 100 for supplying a polymerization solution to purify a solvent present in a by-product produced in a solution polymerization process of a thermoplastic elastomer, ; A multi-stage distillation column (200) having n number of stages for separating into a column bottom component comprising a column top component comprising a low boiling point material, a top side cut component comprising a solvent, and a high boiling point material through fractional distillation of the polymerization solution; The polymerization solution introduced from the polymerization solution supply part 100 is heated and continuously supplied to the multi-stage distillation column 200, which is located between the polymerization solution supply part 100 and the multi-stage distillation column 200. At this time, A first heat exchanger (300) for providing heat exchange with a top side cut component discharged from the multi-stage distillation column (200); A second heat exchanger (400) connected to the upper side of the multi-stage distillation column (200) to condense the column components discharged therefrom; And a third heat exchanger 500 connected to the lower side of the multi-stage distillation column 200 and for heating a part of the column bottom components discharged therefrom.

In the present invention, the thermoplastic elastomer may comprise a polymer or a mixture of polymers having both thermoplastic and elastomeric properties. The thermoplastic elastomer may be a styrene-based copolymer. For example, the styrenic copolymer may be a styrene-butadiene-styrene (SBS) block copolymer, a styrene-isoprene-styrene (SIS) block copolymer, a styrene-isoprene- Butadiene-styrene block copolymers, styrene-ethylene-butadiene-styrene (SEBS) block copolymers, styrene-ethylene-propylene-styrene -Ethylene-Propylene-Styrene (SEPS) block copolymers and styrene-ethylene-ethylene / propylene-styrene (SEEPS) block copolymers.

In the present invention, the solvent is generally used in a solution polymerization reaction of a thermoplastic elastomer, and is not particularly limited. For example, the solvent may be selected from the group consisting of propane, butane, pentane, n-hexane, n-heptane, cyclohexane, methylcyclohexane, octane, cyclooctane, decane, dodecane, benzene, xylene, And may be at least one selected from the group consisting of benzene, toluene, ethylbenzene, chlorobenzene, dichlorobenzene, and trichlorobenzene.

The polymerization solution supply part 100 comprises a storage space for storing the polymerization solution therein and an outlet for discharging the polymerization solution from the storage space.

The polymerization solution is recovered from a thermoplastic elastomer separation process which is a reaction product after preparing a thermoplastic elastomer through solution polymerization. Accordingly, the polymerization solution may include by-products and raw material impurities produced in the synthesis of the thermoplastic elastomer by the solution polymerization reaction, and the solvent used in the reaction. The by-products and the raw material impurities may include a low boiling point material, a high boiling point material, an unreacted monomer, and the like.

In addition, the polymerization solution supply unit 100 may be directly connected to a reactor in which a steam stripping process for separating the thermoplastic elastomer from the polymer solution is performed.

The multi-stage distillation column 200 is a device designed for fractional distillation of the polymerization solution introduced from the polymerization solution supply unit 100. The multi-stage distillation column 200 is a column in which the top components (low-boiling point substances) are separated from each other using the boiling point difference of the components of the polymerization solution (F, F ') containing the low boiling point substance (B), the high boiling point substance (C) , A column bottom component (high boiling point material) and a top side cut component (solvent).

The specific type of the multi-stage distillation column 200 is not particularly limited, and a general distillation column which separates the liquid mixture by boiling point difference can be widely used in the art. The inner shape or inner diameter of the multi-stage distillation tower is not particularly limited, and it is also possible to use a multi-stage distillation tower modified in consideration of purification efficiency.

The multi-stage distillation column 200 may include an internal in which gas-liquid contact of the polymerized solution introduced therein is performed. At this time, the multi-stage distillation column 200 may be a continuous multi-stage distillation column including both the packing and the tray as the internal. For example, the tray may be any of a bubble cap tray, a sieve tray, a unflux tray, a valve tray, a Natta valve tray, a ballast tray, a venturi tray, a kitter tray, a turbo grid tray, It is possible to do. The filling material may be a ring type such as a Rashig ring, a Lessing ring, a split ring or a Pall ring, a saddle type such as bar saddle or interlock saddle, It is possible to employ any type of packing, Stedman packing, Dixon ring, Magmahon packing, Helix packing, Tellerrette, Cross spiral packing.

In the present invention, the multi-stage distillation column 200 has n stages, where the number n means the number of trays when the internal tray is a tray and the number of theoretical stages when the internal is a packing. For continuous multi-stage distillation columns containing both trays and packing, n is the sum of the number of trays and the theoretical number of stages.

The multi-stage distillation column 200 used in the present invention may include internals having a number n satisfying 10? N? 80. Preferably 15? N? 60, more preferably 25? N? 50. If the number n of the number of stages is smaller than 10, the separation efficiency decreases. On the other hand, if the number of stages n is larger than 80, the pressure difference between the upper and lower portions of the column becomes too large, The temperature must be increased to increase the cost.

The interior of the multi-stage distillation column 200 may be divided into a top region 201, an intermediate region 202 and a bottom region 203, as shown in FIG.

The overhead region 201 is a region through which the column top component including the low boiling point material B is discharged to the top of the tower. The middle region 202 is a region into which the polymerization solution (F, F ') flows and a top side cut component containing the solvent (A) is discharged. The column bottom portion 203 is a region where the column bottom component including the high boiling point material C is discharged to the lower portion of the column. The top of the multi-stage distillation column 200 refers to the top of the multi-stage distillation column 200 and may be included in the top region 201 of the multi-stage distillation column 200 described above. The top of the multi-stage distillation column 200 refers to the bottom of the multi-stage distillation column 200 and may be included in the column bottom region 203 of the multi-stage distillation column 200.

The multi-stage distillation column (200) has a polymerization solution inlet (202b) through which the polymerization solution flows into one side. In the present invention, the polymerization solution inlet 202b is provided at a position 0.11 to 0.4 of the number n of stages of the multi-stage distillation column 200. Preferably, the polymerization solution inlet 202b may be at a position 0.15 to 0.3 of the number n. Particularly, in the multi-stage distillation column 200 according to the present invention, since the polymerization solution inlet 202b is located in the middle part of the column, the separation efficiency can be improved compared to the conventional solvent purification process of supplying the polymerization solution to the first stage, have. In addition, as the position of the polymerization solution inlet 202b is adjusted to the middle portion of the column, the amount of vaporization into the overhead region 201 and the flow rate of the component refluxed to the multi-stage distillation column 200 among the column top components decrease, The amount of energy consumed in the heat exchanger 400 can be reduced.

The multi-stage distillation column 200 includes a first outlet 202a for discharging the top side cut component to one side, a second outlet 201a for discharging the top component to the top side, And a third discharge port 203a for discharging.

The multi-stage distillation column 200 includes a first inlet 201b for reflux into the multi-stage distillation column 200 of the solvent separated from the second heat exchanger 400 and a first inlet 201b for flowing into one side of the multi- And a second inlet 203b for introducing the gaseous solvent separated from the heat exchanger 500 into the lower portion of one side of the multi-stage distillation column 200.

The first heat exchanger 300 is located between the polymerization solution supply unit 100 and the multi-stage distillation column 200. One side of the first heat exchanger 300 is connected to the polymerization solution supply unit 100, (200).

The first heat exchanger 300 heats the polymerized solution F introduced from the polymerization solution supply part 100 and continuously supplies the heated polymerization solution F to the multi-stage distillation column 200.

The first heat exchanger 300 serves to heat the polymerization solution through heat exchange with the top side cut component discharged from the multi-stage distillation column 200. The topside cut component is discharged through the first outlet 202a of the multi-stage distillation column 200 and includes a solvent. The topside cut component can be a liquid or a liquid / gaseous mixture. Particularly, the present invention is characterized in that only the polymerization solution supplied to the multi-stage distillation column (200) is heated and supplied through the first heat exchanger (300) This is possible. The amount of energy consumed in the third heat exchanger 500, which will be described later, can be further reduced by separating all of the top side cut components into a liquid phase, and can be directly used without any additional treatment process when reused in a solution polymerization reaction .

The first heat exchanger 300 includes an inner pipe through which the polymerization solution F supplied from the polymerization solution supply unit 100 is transferred; And an outer tube enclosing the inner tube. At this time, the top side cut component at a high temperature flows into the outer surface of the first heat exchanger 300, and the polymerization solution is heated and supplied to the multi-stage distillation column 200 through heat exchange between the inner pipe and the outer pipe, The component, the solvent, is recovered. The recovered solvent may be supplied directly to the polymerization reactor in which the solution polymerization reaction of the thermoplastic elastomer is carried out.

At this time, the temperature difference between the polymerization solution (F) before passing through the first heat exchanger (300) and the heated polymerization solution (F ') after passing may be 40 to 60 ° C. In addition, the temperature difference between the top side cut component before and after the first heat exchanger 300 may be -50 to -10 ° C.

The second heat exchanger (400) is connected to the upper side of the multi-stage distillation column (200) and serves to condense the column top components discharged from the second discharge port (201a). The second heat exchanger (400) is a device for heat-exchanging and condensing the top components discharged from the multi-stage distillation column (200) by a method of contacting the top components discharged from the multi-stage distillation column (200) with cooling water serving as a refrigerant. The capacitor used can be used without limitation. At this time, the cooling water may be introduced from the outside through a separate device (not shown).

Among the top components introduced into the second heat exchanger 400, the gas D is discharged to the outside, and the top component passing through the second heat exchanger 400 includes a low boiling point substance and a solvent. Accordingly, the second heat exchanger (400) is provided with a branched piping structure for discharging a low-boiling substance to one side and refluxing the solvent to the multi-stage distillation column. At this time, the refluxed solvent flows through the first inlet 201b of the multi-stage distillation column 200 as described above.

The third heat exchanger 500 is piped to the lower side of the multi-stage distillation column 200 and serves to heat a part of the column bottom components discharged from the third discharge port 203a. The third heat exchanger 500 is a device for heat-exchanging the liquid column bottom component discharged from the multi-stage distillation column 200 with water vapor serving as a heat medium or heating and evaporating the heat again through a heating device, and reboilers commonly used in the art can be used without limitation.

The column bottom component discharged from the third outlet 203a contains a high boiling point material and a solvent. At this time, the high boiling point material is discharged to the outside, and the solvent flows into the third heat exchanger 500 and is heated. The gaseous solvent heated through the third heat exchanger 500 flows into the multi-stage distillation column 200 through the second inlet 203b of the multi-stage distillation column 200 as described above.

In addition, the present invention can provide a method for purifying a solvent using the apparatus for purifying a solvent described above.

A method for purifying a solvent according to an embodiment of the present invention comprises

Supplying the polymerization solution from the polymerization solution supply unit to the multi-stage distillation column having n number of stages while being heated through the first heat exchanger;

Discharging the solvent into the topside cut component through fractional distillation of the multi-stage distillation column, discharging the low boiling point substance to the top component, and discharging the high boiling point substance to the bottom component;

Heating the polymerization solution supplied to the multi-stage distillation column through heat exchange through the first heat exchanger; And

The column top portion is condensed through the second heat exchanger to reflux the solvent in the low boiling point material to the multi-stage distillation column in a liquid state, and a part of the column bottom portion is heated through the third heat exchanger to heat the solvent in the high boiling point material to the multi- Through the inflow step.

The method of purifying the solvent according to the first embodiment of the present invention is performed as follows to purify the solvent present in the by-product produced in the solution polymerization process of the thermoplastic elastomer.

2 is a schematic diagram showing a process of purifying a solvent according to the first embodiment of the present invention. In Fig. 2, a solid line indicates a liquid phase flow, and a dotted line indicates a gas phase flow.

For better understanding, by-products prepared after solution polymerization of styrene-butadiene-styrene block copolymer rubber were used as raw materials. In the polymerization solution, styrene and 1,3-butadiene, which are unreacted monomers, are present, n-hexane and cyclohexane used as a solvent are contained, and in addition, 1-butene and 2-butene, Molecular weight regulators, antioxidants, polymerization regulators, and the like. At this time, the boiling point of styrene is 145 占 폚, 1,3-butadiene is -4.4 占 폚, 68 占 폚 for n-hexane and 80.7 占 폚 for cyclohexane.

2, the polymerization solution (F) having the above composition is first supplied to the first heat exchanger (300) from the polymerization solution supply part (100) at 45 ° C, and the polymerization The solution (F ') is supplied to a predetermined position of the multi-stage distillation column (200) through the polymerization solution inlet (202b) while being heated to 92 ° C.

At this time, when the number of stages of the multi-stage distillation column 200 is 26, the polymerization solution inlet 202b is positioned at the 5th stage, and the polymerization solution is supplied through the inlet.

Next, the polymerization solution supplied to the multi-stage distillation column 200 is subjected to fractional distillation by heating to separate the solvent n-hexane and cyclohexane into liquid or liquid / gaseous state at a temperature of 113 ° C as the first side cut component And is discharged through the discharge port 202a.

The top side cut components discharged from the first outlet 202a are introduced into the first heat exchanger 300 and some gaseous components are liquefied through the first heat exchanger 300 at a temperature of 113 ° C, (A). ≪ / RTI >

At this time, the energy consumption of the first heat exchanger 300 is 0.52 Gcal.

At this time, low-boiling substances including 1,3-butadiene and the like are transferred to the upper portion of the tower as a column top component through fractional distillation of the multi-stage distillation column 200 and discharged through the second discharge port 201a (B).

The discharged top component contains some solvent together with the low-boiling substance in the state of being heated to the temperature of 93 캜, and is discharged to the vapor phase.

At this time, in order to recover the solvent contained in the column top component, the column top component passes through the second heat exchanger (400).

The vapor phase of the top component is removed through the second heat exchanger 400 as a vent gas (D). In addition, the second heat exchanger (400) is cooled by using cooling water as a condenser, and the solvent is condensed and converted into a liquid state. At this time, the energy consumption of the second heat exchanger (400) is 0.2 Gcal.

The condensed solvent is injected into the first inlet 201b through the reflux line and recovered to the upper portion of the tower of the multi-stage distillation column 200. The recovered solvent may be recovered as top side cut components via a continuous fractionation process.

On the other hand, the high boiling point material including styrene and the like is transferred to the bottom of the column as the column bottom component through the fractional distillation of the multi-stage distillation column 200 and discharged through the third discharge port 203a (C).

The discharged column bottom component is heated to a temperature of 116 DEG C and discharged as a liquid phase including some solvent together with the high boiling point material.

At this time, in order to recover the solvent contained in the column bottom component, some of the discharged column bottom components pass through the third heat exchanger 500.

In the third heat exchanger 500, heat is exchanged with water vapor by the reboiler, and the solvent is heated and returned in a gaseous state, wherein the energy consumption of the third heat exchanger 500 is 0.77 Gcal.

The heated solvent is injected into the second inlet 203b through the return line and recovered to the lower portion of the tower of the multi-stage distillation column 200. The recovered solvent may be recovered as top side cut components via a continuous fractionation process.

According to the first embodiment of the present invention, after the production of the styrene-butadiene-styrene block copolymer, a total of 1.49 Gcal is required for the recovery of n-hexane and cyclohexane as solvents, In case of 0.52 Gcal, it can be saved because it is supplied through heat exchange with the topside cut. Therefore, the amount of heat actually consumed is 0.97 Gcal, which shows a very low energy consumption as compared to the conventional 1.54 Gcal consumed in Comparative Example 1, which will be described later.

In addition, the energy consumption can be reduced by consuming energy in the third heat exchanger 500 as the entire amount of the top side cut component discharged from the multi-stage distillation column 200 is separated into a liquid phase.

3 is a schematic diagram showing a process for purifying a solvent according to a second embodiment of the present invention. In Fig. 3, a solid line represents a liquid phase flow and a dotted line represents a gas phase flow.

Referring to FIG. 3, when the topside cut component is discharged into a liquid phase rather than discharged through a liquid / gas mixture and passed through the first heat exchanger 300, a third heat exchange for heating the solvent recovered from the column bottom component The energy consumption of the unit 500 can be greatly reduced from 0.77 Gcal to 0.44 Gcal.

The apparatus for refining and purifying the solvent according to the present invention has the following advantages in comparison with the purification process of the solvent which is performed after the solution polymerization of the conventional thermoplastic elastomer.

First, by adjusting the position of the inlet of the polymerization solution fed to the multi-stage distillation column to a specific position in the middle part rather than the top of the multi-stage distillation column, it is possible to increase the separation efficiency for the low boiling point component, It can reduce the overall energy consumption.

Second, by heating only the polymerization solution excluding the amount of reflux flowing into the multi-stage distillation column, even when the entire amount of the top side cut component is separated into liquid phase, heat exchange through the first heat exchanger is enabled and the amount of energy consumed in the third heat exchanger is significantly reduced The cost can be reduced, and the economical efficiency of the process can be improved.

Hereinafter, examples and comparative examples of the present invention will be exemplified. The following examples are provided to illustrate the present invention in order to facilitate understanding of the present invention, and thus the technical scope of the present invention is not limited thereto.

Example  And Comparative Example

[Example 1]

A styrene-butadiene-styrene block copolymer was prepared by a conventional solution polymerization method using n-hexane and cyclohexane as a solvent. After separating the styrene-butadiene-styrene block copolymer synthesized from the polymer solution, the polymerization solution containing the by-products and the solvent was introduced into the third stage of the multi-stage distillation column having a theoretical number of steps of 26 at a flow rate of 21 ton / hr, .

The polymer solution had the composition shown in Table 1 below and was fed to the multi-stage distillation column by heating to 92 ° C through the first heat exchanger. (Reflux point), top side cut component (solvent) and column bottom component (high boiling point substance) from the multi-stage distillation column through the purification process. Wherein the top side cut component comprising the solvent was a liquid / gaseous mixture.

The composition of the components obtained from the first outlet to the third outlet of the multi-stage distillation tower and the energy consumption of the first to third heat exchangers are shown in Table 1 below.

[Example 2]

The solvent was purified and recovered in the same manner as in Example 1 except that the polymerization solution inlet was changed from the third stage to the fourth stage.

[Example 3]

The solvent was purified and recovered in the same manner as in Example 1 except that the polymerization solution inlet was changed from the third stage to the fifth stage.

[Example 4]

The solvent was purified and recovered in the same manner as in Example 1, except that the polymerization solution inlet was changed from the third stage to the sixth stage.

[Example 5]

The solvent was purified and recovered in the same manner as in Example 1, except that the polymerization solution inlet was changed from the third stage to the seventh stage.

[Example 6]

The solvent was purified and recovered in the same manner as in Example 1 except that the polymerization solution inlet was changed from the third stage to the first stage.

[Example 7]

The solvent was purified and recovered in the same manner as in Example 1, except that all of the top side cut components were recovered in a liquid phase.

[Example 8]

The solvent was purified and recovered in the same manner as in Example 1, except that the entire amount of the top side cut component was recovered as a liquid phase and the polymerization solution inlet portion was changed from the third stage to the fourth stage.

[Example 9]

The solvent was purified and recovered in the same manner as in Example 1, except that all of the top side cut components were recovered as a liquid phase and the polymerization solution inlet was changed from the third stage to the fifth stage.

[Example 10]

The solvent was purified and recovered in the same manner as in Example 1, except that all of the top side cut components were recovered as a liquid phase and the polymerization solution inlet was changed from the third stage to the sixth stage.

[Example 11]

The solvent was purified and recovered in the same manner as in Example 1, except that the above-mentioned top side cut components were all recovered in a liquid phase and the polymerization solution inlet was changed from the third stage to the seventh stage.

[Comparative Example 1]

The solvent was purified and recovered in the same manner as in Example 1 except that both the polymerization solution and the reflux component were heated to the first stage of the multi-stage distillation column by heating with a first heat exchanger. Respectively. In Fig. 4, the solid line represents the liquid phase flow and the dotted line represents the gas phase flow.

Polymerization solution Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Comparative Example 1 Composition (% by weight) Low-boiling substance 0.091 0.024 0.024 0.024 0.024 0.024 0.024 0.023 0.023 0.023 0.024 0.024 0.023 menstruum 99.701 99.816 99.815 99.815 99.815 99.816 99.816 99.799 99.798 99.798 99.798 99.799 99.798 High boiling point material 0.147 0.111 0.112 0.112 0.112 0.112 0.111 0.126 0.127 0.127 0.127 0.127 0.127 Energy consumption (Gcal) The first heat exchanger - 0.53 0.53 0.53 0.53 0.53 0.53 0.53 0.53 0.53 0.53 0.53 0.64 The second heat exchanger - 0.21 0.19 0.19 0.2 0.2 0.23 0.22 0.2 0.2 0.2 0.2 0.54 The third heat exchanger - 0.79 0.77 0.76 0.77 0.77 0.8 0.47 0.44 0.44 0.44 0.45 One Sum - 1.53 1.49 1.48 1.49 1.50 1.56 1.22 1.17 1.17 1.17 1.18 2.18

As shown in Table 1, it can be seen that the separation efficiency is improved and the total amount of energy used in the purification process is lowered in comparison with the comparative example using the conventional solvent purification process.

Comparing the above Examples 1 to 6 and Comparative Example 1, it can be seen that the efficiency of separation is increased and the overall energy consumption is reduced by changing the position of the inflow portion of the polymerization solution. In particular, in the case of Examples 7 to 11 in which all of the topside cut components including the solvent were separated into liquid phase, the energy consumption of the third heat exchanger was about 45% as compared with Comparative Example 1, and the topside cut component was used as the liquid / It was confirmed that the separation efficiency was improved and the energy saving effect was obtained when the solvent was separated by the purification apparatus and purification method of the solvent according to the present invention through 20% have.

The apparatus and method for purifying a solvent of the present invention enable purification of an effective solvent while consuming a significantly lower energy than conventional methods.

100: polymerization solution inlet part 200: multi-stage distillation tower
201: top plate region 201a: second outlet
201b: first inlet 202: middle area
202b: polymerization solution inlet port 202a: first outlet port
203: a bottom region 203a: a third outlet
203b: second inlet port 300: first heat exchanger
400: second heat exchanger 500: third heat exchanger
F, F ': Polymerization solution A: Solvent
B: Low boiling point material C: High boiling point material
D: Gas

Claims (14)

In order to purify the solvent present in the byproducts produced in the solution polymerization process of the thermoplastic elastomer,
A polymerization solution supply part for supplying a polymerization solution;
A multi-stage distillation column having n number of stages for separating into a column bottom component comprising a column top component comprising a low boiling point material, a top side cut component comprising a solvent, and a high boiling point material through fractional distillation of the polymerization solution;
The polymerization solution supply unit is located between the polymerization solution supply unit and the multi-stage distillation column to continuously heat the polymerization solution introduced into the multi-stage distillation column, A first heat exchanger for providing heat through the heat exchanger;
A second heat exchanger connected to the upper side of the multi-stage distillation column to condense the discharged column components; And
And a third heat exchanger connected to the lower side of the multi-stage distillation column and for heating a part of the column bottom components discharged therefrom,
Wherein the polymerization solution inlet of the multi-stage distillation column is arranged such that the polymerization solution flowing into the multi-stage distillation column from the first heat exchanger is supplied at a position of 0.11 to 0.4 of the number n of the multi-stage distillation column. The method according to claim 1,
Wherein the multi-stage distillation column is a continuous multi-stage distillation column having a number n of internals satisfying 10? N? 80 therein. The method according to claim 1,
The multi-stage distillation column has a first outlet for discharging the top side cut component to one side, a second outlet for discharging the exhaust gas from the top side, and a third outlet for discharging the bottom gas component from the bottom side And a solvent. The method according to claim 1,
The multi-stage distillation column has a first inlet for introducing the solvent separated from the second heat exchanger into one side of the multi-stage distillation column, and a second inlet for introducing the solvent separated from the third heat exchanger into the lower side of the multi- And the solvent is refluxed. The method according to claim 1,
Wherein the polymerization solution has a temperature difference between 40 DEG C and 60 DEG C before and after passing through the first heat exchanger. The method according to claim 1,
Wherein the topside cut component has a temperature difference between before and after passing through the first heat exchanger is from -50 to -10 占 폚. The method according to claim 1,
Wherein the second heat exchanger is a condenser for condensing a part of the overhead components by heat exchange with the cooling water. The method according to claim 1,
Wherein one side of the second heat exchanger has a branched piping structure for discharging the low boiling point material and refluxing the solvent to the multi-stage distillation column. The method according to claim 1,
Wherein the third heat exchanger is a reboiler for heating a part of the column bottom component by heat exchange with water vapor. The method according to claim 1,
Wherein the topside cut component is a liquid or liquid / gaseous mixture. The method according to claim 1,
Wherein the polymerization solution includes a raw material impurity, a reaction by-product, and a solvent after the thermoplastic elastomer produced in the solution polymerization step is removed by a process such as steam stripping. The method according to claim 1,
The thermoplastic elastomer may be a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a styrene-isoprene / butadiene-styrene block copolymer, a styrene- - styrene block copolymer and styrene-ethylene-ethylene / propylene-styrene block copolymer. The method according to claim 1,
The solvent is selected from the group consisting of propane, butane, pentane, n-hexane, n-heptane, cyclohexane, methylcyclohexane, octane, cyclooctane, decane, dodecane, benzene, xylene, Wherein the solvent is at least one selected from the group consisting of ethylbenzene, chlorobenzene, dichlorobenzene and trichlorobenzene. 14. A process for the purification of a solvent present in a by-product formed in a solution polymerization process of a thermoplastic elastomer using a solvent refining apparatus according to any one of claims 1 to 13,
Supplying the polymerization solution from the polymerization solution supply unit to the multi-stage distillation column having n number of stages while being heated through the first heat exchanger;
Discharging the solvent into the topside cut component through fractional distillation of the multi-stage distillation column, discharging the low boiling point substance to the top component, and discharging the high boiling point substance to the bottom component;
Heating the polymerization solution supplied to the multi-stage distillation column through heat exchange through the first heat exchanger; And
The column top portion is condensed through the second heat exchanger to reflux the solvent in the low boiling point material to the multi-stage distillation column in a liquid state, and a part of the column bottom portion is heated through the third heat exchanger to heat the solvent in the high boiling point material to the multi- Comprising the steps of:
Wherein the polymerization solution inlet of the multi-stage distillation column is arranged such that the polymerization solution supplied from the first heat exchanger is supplied at a position 0.11 to 0.4 of the number n of the number n of the multi-stage distillation column.

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