Method for recovering conjugated diene monomers

Abstract

The present invention provides a method for recovering a conjugated diene-based monomer, comprising the steps of: supplying a feed stream containing a conjugated diene-based monomer to a condensation section to condense it, thereby obtaining a stream containing the condensed conjugated diene-based monomer and a stream containing uncondensed conjugated diene-based monomer; recovering the conjugated diene-based monomer from the stream containing the condensed conjugated diene-based monomer, supplying the stream containing the uncondensed conjugated diene-based monomer to a first absorption tower to bring it into contact with an absorbent, thereby obtaining an absorption solution in which the conjugated diene-based monomer is absorbed into the absorbent; supplying the absorption solution to a stripping column to separate the absorption solution into the absorbent and the conjugated diene-based monomer; circulating a bottom discharge stream from the stripping column containing the separated absorbent to the first absorption column; and circulating an top discharge stream from the stripping column containing the separated conjugated diene-based monomer to the condensation section.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0158562 dated November 23, 2022 and Korean Patent Application No. 10-2023-0158834 dated November 16, 2023, and all contents disclosed in the documents of the relevant Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a method for recovering a conjugated diene monomer, and more particularly to a method for recovering a conjugated diene monomer by introducing an absorbent to remove uncondensed gases such as nitrogen and effectively separating the absorbent and the conjugated diene monomer through a cooling section. [Background technology]

[0003] Generally, in the process of producing NBL (Nitrile Butadiene Rubber Latex), the aqueous polymer solution obtained after the polymerization reaction of a nitrile monomer and a conjugated diene monomer may contain not only the copolymer latex but also the conjugated diene monomer and the nitrile monomer that did not react in the polymerization reaction.

[0004] In this process, the nitrile monomer contained in the aqueous polymer solution is separated and recovered through a compression process and an absorption tower. The residue after separation of the nitrile monomer contains conjugated diene monomers, and conventionally, the residue after separation of the nitrile monomers (mixed gas) is supplied to a condenser, condensed, and then recovered in liquid form. However, uncondensed gases such as nitrogen introduced or fed during the process increase the vapor pressure of the mixed gas, resulting in a problem that a large amount of conjugated diene monomers are not condensed and are burned together with the nitrogen. The combustion of conjugated diene monomers raises environmental issues due to the greenhouse gases and total volatile organic compounds (tVOCs) generated during this process, as well as significant costs associated with the loss of conjugated diene monomers.

[0005] Therefore, it is necessary to introduce a process that can separate the conjugated diene monomer to be recovered from the uncondensed gas and can increase the recovery rate of the conjugated diene monomer. Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a method for recovering a conjugated diene monomer, which can effectively separate the conjugated diene monomer from uncondensed gases such as nitrogen and can increase the recovery rate of the conjugated diene monomer, in order to solve the problems mentioned in the background of the invention. [Means for solving the problem]

[0007] According to one embodiment of the present invention for solving the above-mentioned problems, the present invention provides a method for recovering a conjugated diene-based monomer, comprising the steps of: supplying a feed stream containing a conjugated diene-based monomer to a condensation part to condense it, thereby obtaining a stream containing a condensed conjugated diene-based monomer and a stream containing an uncondensed conjugated diene-based monomer; recovering the conjugated diene-based monomer from the stream containing the condensed conjugated diene-based monomer, supplying the stream containing the uncondensed conjugated diene-based monomer to a first absorption tower to contact it with an absorbent, thereby obtaining an absorption solution in which the conjugated diene-based monomer is absorbed into the absorbent; supplying the absorption solution to a stripping column to separate the absorption solution into the absorbent and the conjugated diene-based monomer, circulating a bottom discharge stream from the stripping column containing the separated absorbent to the first absorption tower, and circulating an top discharge stream from the stripping column containing the separated conjugated diene-based monomer to the condensation part. [Effects of the Invention]

[0008] According to the method for recovering a conjugated diene monomer of the present invention, an absorbent is introduced into a first absorption tower, and unabsorbed gas containing nitrogen that is not absorbed by the absorbent is separated from the conjugated diene monomer, thereby recovering the conjugated diene monomer. Specifically, the conjugated diene monomer is selectively absorbed into the absorbent to obtain an absorbent solution, and the conjugated diene monomer can be recovered from the absorbent solution. This minimizes the loss of the conjugated diene monomer that is separated and burned together with the unabsorbed gas.

[0009] Meanwhile, a cooling unit installed at the top of the stripping column directly controls the temperature of the upper portion of the stripping column, thereby preventing fouling within the stripping column. Furthermore, by controlling the temperature of the upper portion of the stripping column using the cooling unit, separation of the absorbent and the conjugated diene monomer in the stripping column can be easily performed, and the recovery rates of the conjugated diene monomer and the absorbent can also be increased. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a flow chart of a process for recovering a conjugated diene monomer according to one embodiment of the present invention. [Figure 2] 1 is a flow chart of steps in a method for recovering a conjugated diene monomer according to Comparative Example 1 of the present invention. [Figure 3] 1 is a flow chart of steps in a method for recovering a conjugated diene monomer according to Comparative Example 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The terms and words used in the description of the present invention and the claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0012] In the present invention, the term "stream" refers to the flow of fluid within a process, and can also refer to the fluid itself flowing in a pipe. Specifically, the term "stream" can refer to both the fluid itself flowing in a pipe connecting each device and the flow of the fluid. Furthermore, the fluid can contain one or more components of gas, liquid, and solid.

[0013] Meanwhile, in the present invention, in apparatuses such as an absorption tower, stripping column, distillation tower, and recovery tower, the "lower part" of the apparatus means a point 95% to 100% below the top of the apparatus, specifically the lowest stage (bottom), unless otherwise specified. Similarly, the "upper part" of the apparatus means a point 0% to 5% below the top of the apparatus, specifically the top (top), unless otherwise specified.

[0014] Meanwhile, in the present invention, in apparatuses such as an absorption column, a stripping column, a distillation column, and a recovery column, the pressure of the apparatus refers to the pressure at the top of the apparatus unless otherwise specified.

[0015] In order to facilitate understanding of the present invention, the present invention will now be described in more detail with reference to FIG.

[0016] A method for recovering a conjugated diene monomer according to one embodiment of the present invention includes the steps of: supplying a feed stream containing a conjugated diene monomer to a condensation section 10 to condense it, thereby obtaining a stream containing the condensed conjugated diene monomer and a stream containing uncondensed conjugated diene monomer; recovering the conjugated diene monomer from the stream containing the condensed conjugated diene monomer, supplying the stream containing the uncondensed conjugated diene monomer to a first absorption tower 100 to contact it with an absorbent, thereby obtaining an absorption solution in which the conjugated diene monomer is absorbed into the absorbent; supplying the absorption solution to a stripping column 300 to separate the absorption solution into the absorbent and the conjugated diene monomer; circulating a bottom discharge stream from the stripping column containing the separated absorbent to the first absorption tower 100; and circulating an top discharge stream from the stripping column containing the separated conjugated diene monomer to the condensation section 10.

[0017] First, a method for recovering a conjugated diene monomer according to one embodiment of the present invention can include the steps of supplying a feed stream containing a conjugated diene monomer to a condensation section 10, condensing the feed stream, and obtaining a stream containing the condensed conjugated diene monomer and a stream containing uncondensed conjugated diene monomer.

[0018] In this case, the feed stream containing the conjugated diene monomer may be derived from a stream separated from a copolymer latex during a polymerization process in which reactants containing a nitrile monomer and a conjugated diene monomer are polymerized to obtain a copolymer latex. More specifically, the polymerization process may include a polymerization step and a vacuum stripping step. The polymerization step may be performed by supplying reactants containing a nitrile monomer and a conjugated diene monomer to a reactor and polymerizing them, thereby obtaining an aqueous polymer solution. In this case, water may be further supplied to the reactor. The aqueous polymer solution may contain water, a nitrile monomer, a conjugated diene monomer, and a copolymer latex. In this case, the nitrile monomer and the conjugated diene monomer may be unreacted monomers that were not polymerized during the polymerization reaction.

[0019] In the present invention, the nitrile-based monomer may include, but is not limited to, at least one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, α-chloronitrile, and α-cyanoethylacrylonitrile. As a specific example, the nitrile-based monomer may be acrylonitrile.

[0020] Meanwhile, the conjugated diene monomer may include, but is not limited to, one or more selected from the group consisting of 1,3-butadiene, 1,4-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, piperylene, 3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene, and isoprene. As a specific example, the conjugated diene monomer may be 1,3-butadiene or 1,4-butadiene.

[0021] A vacuum stripping step can be performed to obtain a copolymer latex contained in the aqueous polymer solution. By using vacuum and heat in the vacuum stripping step, by-products, nitrile monomers, and conjugated diene monomers contained in the aqueous polymer solution can be separated from the copolymer latex. Thus, a copolymer latex is finally obtained, and the copolymer latex can be, for example, nitrile-butadiene rubber latex (NBL).

[0022] In the polymerization process, the stream separated from the copolymer latex may further undergo a compression process. Specifically, the stream separated from the copolymer latex may be compressed and condensed in the compression process. This separates water and nitrile-based monomers, and the remainder from which the water and nitrile-based monomers are separated may be supplied to the second absorption tower 200. In this case, the water is treated as wastewater, and the nitrile-based monomers are separately recovered and reused as reactants in the polymerization process. Meanwhile, the remainder from which the water and nitrile-based monomers are separated may contain conjugated diene-based monomers.

[0023] According to the present invention, the remainder from which water and nitrile-based monomers are separated through the compression process can be supplied to the lower part of the second absorption tower 200 to further separate some of the nitrile-based monomers. In this case, the part of the nitrile-based monomers separated in the second absorption tower 200 may be the nitrile-based monomers that were not separated in the compression process.

[0024] Specifically, a solvent is supplied to the top of the second absorption tower 200, and a nitrile-based monomer is dissolved in the solvent to obtain a nitrile-based monomer aqueous solution. The solvent may include water. The nitrile-based monomer can be recovered from the nitrile-based monomer aqueous solution and reused as a reactant in the polymerization reaction step. Meanwhile, a stream containing the residue obtained by separating the nitrile-based monomer aqueous solution in the second absorption tower 200 can be supplied to the condenser 10 as a feed stream of the present invention. In this case, the feed stream may contain nitrogen, oxygen, and C4 impurities (i-butane, n-butane, 1-butene, i-butene, trans / cis-2-butene, 1,2-butadiene) in addition to the conjugated diene-based monomer.

[0025] The condensation unit 10 may include a condenser 11 and a flash tank 20. Specifically, a feed stream containing a conjugated diene-based monomer may be supplied to the condenser 11 and condensed, thereby obtaining a condensation product. The condensation product may include the conjugated diene-based monomer condensed by the condenser 11 and uncondensed conjugated diene-based monomer. In this case, the temperature at which condensation is performed in the condenser 11 may be 10°C or more or 12°C or more and 20°C or less or 18°C ​​or less.

[0026] The condensed product can then be supplied to a flash tank 20 and separated into a liquid phase and a gas phase. Specifically, the condensed product can be separated in the flash tank 20 into a stream containing condensed conjugated diene monomers and a stream containing uncondensed conjugated diene monomers. More specifically, the stream containing condensed conjugated diene monomers can be obtained in a liquid phase, and the stream containing uncondensed conjugated diene monomers can be obtained in a gas phase. In this case, the conjugated diene monomers can be recovered from the stream containing condensed conjugated diene monomers and reused as a reactant in the polymerization process.

[0027] Meanwhile, the stream containing the uncondensed conjugated diene monomer may further contain nitrogen, oxygen, and C4 impurities in addition to the conjugated diene monomer. In this case, the conjugated diene monomer may be one that was not condensed in the condenser 11 and recovered in the flash tank 20.

[0028] Meanwhile, when a stream containing the uncondensed conjugated diene monomer is flared as in the past, environmental problems have arisen due to greenhouse gases and tVOCs (Total Volatile Organic Compounds) generated in the process. Furthermore, the loss cost of the conjugated diene monomer contained in the stream containing the uncondensed conjugated diene monomer has excessively increased. Therefore, the present invention not only increases the recovery rate of the conjugated diene monomer but also solves the environmental problems caused by combustion by separately separating and recovering the conjugated diene monomer contained in the stream containing the uncondensed conjugated diene monomer.

[0029] According to the present invention, the content of the conjugated diene monomer contained in the stream containing the uncondensed conjugated diene monomer may be 80 wt% or more, 84 wt% or more, or 88 wt% or more, and 95 wt% or less, 94 wt% or less, or 92 wt% or less. When the content of the conjugated diene monomer contained in the stream containing the uncondensed conjugated diene monomer is within the above range, the load on the first absorption tower 100 (described below) is reduced, and the absorption efficiency of the first absorption tower 100 can be maximized compared to the size of the equipment. Therefore, this is preferable in terms of economy, such as process equipment costs and device costs.

[0030] The method for recovering a conjugated diene monomer according to one embodiment of the present invention may include a step of supplying a stream containing the uncondensed conjugated diene monomer to a first absorption tower 100, contacting the stream with an absorbent, and obtaining an absorbent solution in which the conjugated diene monomer is absorbed by the absorbent.

[0031] Specifically, the conjugated diene monomer contained in the stream containing the uncondensed conjugated diene monomer can be absorbed by the absorbent, thereby obtaining an absorbent solution. Meanwhile, a non-absorbed gas containing components not dissolved in the absorbent can be separated from the absorbent solution. The non-absorbed gas may contain C4 impurities, nitrogen, and oxygen. Therefore, the first absorber 100 can separate a lower discharge stream from the first absorber containing the absorbent solution and an upper discharge stream from the first absorber containing the non-absorbed gas. In this case, the upper discharge stream from the first absorber can be burned separately. By absorbing the conjugated diene monomer into the absorbent and separating it in the first absorber 100, the loss of the conjugated diene monomer can be minimized compared to the conventional method of burning the stream containing the uncondensed conjugated diene monomer.

[0032] On the other hand, if the non-absorbed gas containing nitrogen and oxygen is recycled to the condenser 11 together with the conjugated diene monomer without separating and removing it, the amount of the conjugated diene monomer that is not condensed in the condenser 11 may increase excessively due to the increased steam pressure, and the yield of the condensed conjugated diene monomer may decrease. Therefore, it is preferable to separate the non-absorbed gas in the first absorption tower 100.

[0033] For this purpose, the operating pressure of the first absorption tower 100 is set to 2 to 5 kgf / cm. 2 (g), specifically 2.5 to 3.5 kgf / cm 2 (g). The operating pressure of the first absorber 100 may be a gauge pressure. By operating the first absorber 100 at a pressure within the above range, the conjugated diene monomer can be effectively absorbed into the absorbent, and separation of the non-absorbed gas and the absorbent solution within the first absorber can be facilitated. Therefore, the content of the conjugated diene monomer in the top discharge stream of the first absorber can be minimized.

[0034] In the present invention, the absorbent may be a hydrocarbon compound having 6 to 30 carbon atoms, specifically, kerosene or diesel oil (gas oil). More specifically, the kerosene and diesel oil are the result of distillation of crude oil and may be obtained in a lower stage than naphtha and higher stage than heavy oil (fuel oil) in a crude oil distillation tower. The boiling point of the kerosene may be 140°C or higher, 150°C or higher, or 200°C or higher, and 300°C or lower, 270°C or lower, or 250°C or lower. The boiling point of the diesel oil may be 130°C or higher, 150°C or higher, or 200°C or higher, and 380°C or lower, 360°C or lower, or 350°C or lower. When kerosene or diesel oil is used as the absorbent of the present invention, the conjugated diene monomer contained in the stream containing the uncondensed conjugated diene monomer can be effectively absorbed by the absorbent.

[0035] Meanwhile, the mass flow rate at which the absorbent is introduced into the first absorption tower 100 may be 5 times or more, 7 times or more, or 9 times or more, and 15 times or less, 13 times or less, or 11 times or less, of the mass flow rate at which the stream containing the uncondensed conjugated diene monomer is supplied to the first absorption tower 100. When the flow rate at which the absorbent is introduced into the first absorption tower 100 is a multiple within the above range of the flow rate of the stream containing the uncondensed conjugated diene monomer, the conjugated diene monomer can be easily absorbed by the absorbent, and the loss of the conjugated diene monomer that is burned together with the non-absorbed gas in the upper discharge stream of the first absorption tower can be minimized.

[0036] According to the present invention, the content of the conjugated diene monomer contained in the absorbent solution may be 1 wt% or more, 5 wt% or more, or 7 wt% or more, and 20 wt% or less, 15 wt% or less, or 10 wt% or less. When the content of the conjugated diene monomer contained in the absorbent solution, i.e., the lower discharge stream of the first absorber, is within the above range, an appropriate amount of the conjugated diene monomer is absorbed into the absorbent, and an excessive increase in temperature due to heat released as absorption progresses in the first absorber 100 can be prevented. In addition, the solubility of the conjugated diene monomer is increased, and the absorption efficiency in the first absorber 100 can be further maximized.

[0037] A method for recovering a conjugated diene-based monomer according to one embodiment of the present invention may include the steps of supplying the absorption solution to a stripping column 300 to separate the absorption solution into an absorbent and a conjugated diene-based monomer, circulating a bottom discharge stream from the stripping column containing the separated absorbent to a first absorption tower 100, and circulating an top discharge stream from the stripping column containing the separated conjugated diene-based monomer to the condensation section 10.

[0038] Specifically, the bottom discharge stream from the first absorber containing the absorbent solution can be supplied to the stripping column 300 and separated into a bottom fraction from the stripping column 300 containing the absorbent and an upper fraction from the stripping column 300 containing the conjugated diene monomer. The bottom fraction from the stripping column 300 can be circulated to the first absorber 100 as the bottom discharge stream from the stripping column, and the upper fraction from the stripping column 300 can be circulated to the condenser 10 as the top discharge stream from the stripping column.

[0039] More specifically, heat is supplied to the stripping column 300 by the reboiler 40 provided downstream of the stripping column 300, and thus the vaporized conjugated diene monomer can move to the upper part of the stripping column 300. The conjugated diene monomer that has moved to the upper part of the stripping column 300 increases the temperature at the upper part of the stripping column 300, which may cause fouling.

[0040] Therefore, in the present invention, the stripping column 300 may include a cooling section 50 at the highest stage. The stripping column 300 is a column composed of multiple stages, and the highest stage is the highest stage where the top of the column is located. Specifically, the cooling section 50 may include a cooling coil, which may reduce the temperature at a height of 0 to 20% of the height of the stripping column 300, more specifically, the temperature at the top of the stripping column 300. Furthermore, the absorbent vaporized together with the conjugated diene monomer by the reboiler 40 is cooled in the cooling section 50 at the highest stage of the stripping column, thereby effectively separating the cooled absorbent from the conjugated diene monomer.

[0041] The cooling unit 50 may control the temperature of the stripping column 300 from 0% to 20% of its height to 10°C or more, 12°C or more, or 14°C or more, and 30°C or less, 28°C or less, or 20°C or less, based on the 0% height of the top of the stripping column 300. In this case, the top of the stripping column 300 may refer to the top of the column. For example, if the cooling unit 50 is installed at the top of the stripping column 300, the temperature at the top of the stripping column 300 may be lowest, and the temperature may increase from the top to the bottom of the stripping column 300. Therefore, the cooling unit 50 may control the temperature in the 0% to 20% height region of the stripping column 300 to fall within a temperature range of 10°C to 30°C.

[0042] Specifically, adjusting the temperature at 0 to 20% height of stripping column 300 within the above range is preferable in that the vaporized absorbent is cooled to separate it from the conjugated diene monomer, and it is possible to reduce the risk of fouling due to a rise in temperature within stripping column 300. In this case, the temperature at 0 to 20% height of stripping column 300 can be controlled by the cooling unit 50, and by adjusting the cooling coil provided in the cooling unit 50 to a temperature lower than the target temperature of stripping column 300 in the present invention, the temperature at 0 to 20% height of stripping column 300 can be controlled to 10°C to 30°C.

[0043] More specifically, if the temperature at the 0-20% height of the stripping column 300 is less than 10°C, the conjugated diene monomer may condense with the absorbent and remain inside the stripping column 300 due to the low temperature. Furthermore, to meet this temperature requirement, a new cooling source is required instead of the conventional chilled water used in the cooling unit, which is undesirable from an economic standpoint, such as additional process and equipment costs. Meanwhile, if the temperature at the 0-20% height of the stripping column 300 exceeds 30°C, it may be difficult to condense the absorbent in the cooling unit, which may make it difficult to effectively separate the absorbent and the conjugated diene monomer within the stripping column 300. Furthermore, it may be difficult to prevent fouling within the stripping column 300.

[0044] On the other hand, the operating pressure of the stripping column 300 is -0.9 kgf / cm 2 (g) or more, -0.8kgf / cm 2 (g) or more, or -0.7kgf / cm 2 (g) or more, and -0.1kgf / cm 2 (g) or less, -0.2kgf / cm 2 (g) or less, or -0.4kgf / cm 2(g) or less. In this case, the operating pressure of the stripping column 300 is a gauge pressure, which may mean the absolute pressure minus atmospheric pressure. By operating the stripping column 300 at a pressure within the above range, the boiling point difference between the substances to be separated in the stripping column 300 increases, thereby increasing the separation efficiency of the stripping column 300. Furthermore, by lowering the pressure from the first absorption tower 100 to the stripping column 300, the separation of the conjugated diene-based monomer in the stripping column 300 can be more smoothly performed. Therefore, the separation of the conjugated diene-based monomer and the absorbent in the stripping column 300 can be effectively performed.

[0045] In this way, by controlling the operating pressure and temperature of the stripping column 300, the amount of absorbent lost can be minimized and the recovered absorbent can be reused in the first absorber 100. Therefore, the amount of fresh absorbent supplied to the first absorber 100 can be minimized.

[0046] Meanwhile, before circulating the top discharge stream from the stripping column to the condensation unit 10, the top discharge stream from the stripping column may be supplied to a vacuum compression unit 30 to be compressed, and the stream containing the absorbent may be supplied to a first absorption tower 100, and the compressed stream containing the conjugated diene-based monomer may be circulated to the condensation unit 10.

[0047] Specifically, the process performed in the vacuum compression unit 30 may include a first compression step and a second compression step. First, the top discharge stream of the stripping column may be introduced into the first compression step. More specifically, in the first compression step, the top discharge stream of the stripping column may be supplied to a vacuum pump to be compressed, supplied to an aftercooler to be cooled, and then separated into a liquid phase stream containing the absorbent and a gas phase stream containing the conjugated diene monomer. In this case, the vacuum pump may be the same device as the compressor, but the pressures of the upstream and downstream stages may be different. Specifically, the vacuum pump may be operated with the upstream pressure set to vacuum.

[0048] Next, the gaseous stream separated through the first compression step can be introduced into a second compression step. More specifically, in the second compression step, the gaseous stream can be supplied to a compressor to be compressed and then supplied to a post-cooler to be cooled. As a result, the absorbent cooled in the post-cooler of the second compression step can be separated from the compressed conjugated diene-based monomer. Therefore, a stream containing the absorbent cooled in the post-cooler of the second compression step and a stream containing the compressed conjugated diene-based monomer are obtained. In this case, the absorbent cooled in the post-cooler of the second compression step can be the absorbent that was not separated in the first compression step.

[0049] Meanwhile, the compressed conjugated diene monomer is in a gaseous state and may be pressurized by a vacuum compression unit 30 to reduce the pressure difference when the compressed conjugated diene monomer-containing stream is supplied to the condenser 10. Finally, the gaseous stream separated in the first compression step and the absorbent-containing stream cooled in the post-cooler of the second compression step are absorbent-containing streams containing a trace amount of absorbent not separated in the preceding stripping column 300 and may be recycled to the first absorption tower 100. Specifically, the absorbent-containing stream may be mixed with the bottom discharge stream of the stripping column to form a mixed stream, and the mixed stream may be supplied to the first absorption tower 100. Meanwhile, the compressed conjugated diene monomer-containing stream may be circulated to the condenser 10.

[0050] The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and technical concept of the present invention, and the scope of the present invention is not limited to these examples.

[0051] Example Example 1 The conjugated diene monomer recovery process was simulated using Aspen Plus simulator from Aspen Corporation, following the process flow shown in Figure 1.

[0052] Specifically, a feed stream containing conjugated diene monomers, nitrogen, oxygen, and C4 impurities was supplied to the condenser 10 at a flow rate of 2000 kg / hr. More specifically, the feed stream was supplied to the condenser 11 and condensed to obtain a condensed product, which was then supplied to the flash tank 20 to obtain a stream containing condensed conjugated diene monomers and a stream containing uncondensed conjugated diene monomers. The conjugated diene monomers were recovered from the stream containing the condensed conjugated diene monomers. At this time, the condensation in the condenser 11 was carried out at a temperature of 20°C. Meanwhile, the content of the conjugated diene monomers in the stream containing uncondensed conjugated diene monomers was 90 wt%.

[0053] The stream containing the uncondensed conjugated diene monomer was supplied to the first absorption tower 100 and brought into contact with kerosene as an absorbent to obtain an absorbed solution in which the conjugated diene monomer was absorbed by the absorbent. The upper discharge stream from the first absorption tower containing nitrogen and oxygen, which are components not absorbed by the absorbent, was burned, and the lower discharge stream from the first absorption tower containing the absorbed solution was supplied to the first stage from the top of the stripping column 300. At this time, the operating pressure of the first absorption tower 100 was 3 kgf / cm. 2 The mass flow rate at which the absorbent was introduced into the first absorption tower 100 was 10 times the mass flow rate at which the stream containing the uncondensed conjugated diene monomer was supplied to the first absorption tower 100.

[0054] The absorbent solution was then separated into an absorbent and a conjugated diene-based monomer in the stripping column 300, yielding a stripping column bottom discharge stream containing the separated absorbent and a stripping column top discharge stream containing the separated conjugated diene-based monomer. The temperature at the top of the stripping column 300 was 10°C due to the cooling unit 50 installed at the top of the stripping column 300, and the temperature at the bottom of the stripping column 300 was 144°C due to the reboiler 40 installed downstream of the stripping column 300. The operating pressure of the stripping column 300 was -0.8 kgf / cm. 2The stripping column was operated as in (g). The bottom discharge stream from the stripping column was circulated to the first absorption tower 100, and the top discharge stream from the stripping column was supplied to the vacuum compression section 30. At this time, the top discharge stream from the stripping column was discharged at a temperature of 10°C.

[0055] Next, a stream containing an absorbent and a stream containing compressed conjugated diene monomers were obtained through a process performed in the vacuum compression section 30. The absorbent-containing stream was mixed with the bottom discharge stream of the stripping column to obtain a mixed stream, and the mixed stream was supplied to the first absorption tower 100. The compressed conjugated diene monomer-containing stream was mixed with a feed stream and supplied to the condensation section 10.

[0056] As a result, the recovery rate of the conjugated diene monomer was 100% by weight, and the loss rate of the absorbent was 0.007% by weight.

[0057] Example 2 In Example 2, a conjugated diene monomer was recovered in accordance with the same process flow as in Example 1, except that a cooling section was not provided at the top stage of the stripping column.

[0058] As a result, the temperature at the top of the stripping column was 40° C., and the top discharge stream of the stripping column was discharged at a temperature of 40° C. The recovery rate of the conjugated diene monomer and the loss rate of the absorbent are shown in Table 1 below.

[0059] Example 3 In Example 3, a conjugated diene monomer was recovered in accordance with the same process flow as in Example 1, except that the temperature at the top of the stripping column was controlled to 15°C by the cooling section.

[0060] Example 4 In Example 4, the conjugated diene monomer was recovered in accordance with the same process flow as in Example 1, except that the temperature at the top of the stripping column was controlled to 35°C by the cooling section.

[0061] Comparative Example Comparative Example 1 The conjugated diene monomer recovery process was simulated using the Aspen Plus simulator from Aspen Corporation, following the process flow shown in Figure 2.

[0062] In Comparative Example 1, a flash tank 400 was provided instead of the stripping column, and the conjugated diene monomer was recovered in the same manner as in Example 1, except that the upper and lower temperatures of the flash tank and the discharge temperature of the conjugated diene monomer were 40°C.

[0063] Specifically, a feed stream containing conjugated diene monomers, nitrogen, oxygen, and C4 impurities was supplied to the condenser 10 at a flow rate of 2000 kg / hr. The feed stream was condensed in the condenser 10 to obtain a stream containing condensed conjugated diene monomers and a stream containing uncondensed conjugated diene monomers. The condensation was carried out at a temperature of 20°C. Meanwhile, the content of the conjugated diene monomers in the stream containing uncondensed conjugated diene monomers was 90 wt%.

[0064] The stream containing the uncondensed conjugated diene monomer was supplied to a first absorption tower 100 and contacted with kerosene as an absorbent to obtain an upper discharge stream from the first absorption tower containing unabsorbed gas and a lower discharge stream from the first absorption tower containing an absorbent solution. At this time, the operating pressure of the first absorption tower 100 was 3 kgf / cm. 2 The mass flow rate at which the absorbent was introduced into the first absorption tower 100 was 10 times the mass flow rate at which the stream containing the uncondensed conjugated diene monomer was supplied to the first absorption tower 100.

[0065] Next, the bottom discharge stream of the first absorber was supplied to flash tank 400 via heater 60. At this time, the heater was operated at a temperature of 40°C. In flash tank 400, the absorbent solution contained in the bottom discharge stream of the first absorber was separated into an absorbent and a conjugated diene-based monomer, and a bottom discharge stream of the flash tank containing the separated absorbent and an top discharge stream of the flash tank containing the separated conjugated diene-based monomer were obtained. At this time, the temperature of rush tank 400 was 40°C, and the operating pressure was -0.8 kgf / cm. 2 The bottom discharge stream from the flash tank was circulated to the first absorption tower 100, and the top discharge stream from the flash tank was supplied to the vacuum compression section 30. At this time, the top discharge stream from the flash tank was discharged at a temperature of 40°C.

[0066] Next, a stream containing an absorbent and a stream containing compressed conjugated diene monomers were obtained through a process performed in the vacuum compression section 30. The absorbent-containing stream was mixed with the bottom discharge stream of the flash tank to obtain a mixed stream, and the mixed stream was supplied to the first absorption tower 100. The compressed conjugated diene monomer-containing stream was mixed with a feed stream and supplied to the condensation section 10.

[0067] As a result, the recovery rate of the conjugated diene monomer was 100% by weight, and the loss rate of the absorbent was 0.013% by weight.

[0068] Comparative Example 2 The conjugated diene monomer recovery process was simulated using the Aspen Plus simulator from Aspen Corporation, following the process flow shown in Figure 3.

[0069] In Comparative Example 1, a conjugated diene monomer was recovered in accordance with the same process flow as in Example 1, except that a distillation column 500 was provided instead of the stripping column.

[0070] Specifically, a feed stream containing conjugated diene monomers, nitrogen, oxygen, and C4 impurities was supplied to the condenser 10 at a flow rate of 2000 kg / hr. The feed stream was condensed in the condenser 10 to obtain a stream containing condensed conjugated diene monomers and a stream containing uncondensed conjugated diene monomers. The condensation was carried out at a temperature of 20°C. Meanwhile, the content of the conjugated diene monomers in the stream containing uncondensed conjugated diene monomers was 90 wt%.

[0071] The stream containing the uncondensed conjugated diene monomer was supplied to a first absorption tower 100 and contacted with kerosene as an absorbent to obtain an upper discharge stream from the first absorption tower containing unabsorbed gas and a lower discharge stream from the first absorption tower containing an absorbent solution. At this time, the operating pressure of the first absorption tower 100 was 3 kgf / cm. 2 The mass flow rate at which the absorbent was introduced into the first absorption tower 100 was 10 times the mass flow rate at which the stream containing the uncondensed conjugated diene monomer was supplied to the first absorption tower 100.

[0072] Next, the bottom discharge stream of the first absorption tower was supplied to a distillation tower 500, and the absorbent solution contained in the bottom discharge stream of the first absorption tower was separated into an absorbent and a conjugated diene-based monomer, thereby obtaining a bottom discharge stream of the distillation tower containing the separated absorbent and an upper discharge stream of the distillation tower containing the separated conjugated diene-based monomer. At this time, the top temperature of the distillation tower 500 was 40°C, and the bottom temperature was 144°C. The operating pressure of the distillation tower 500 was -0.8 kgf / cm. 2 The bottom discharge stream from the distillation tower was circulated to the first absorption tower 100, and the top discharge stream from the distillation tower was passed through a condenser 70, with a portion of the stream being supplied to the vacuum compression section 30 and the remainder being refluxed to the distillation tower 500. At this time, the top discharge stream from the distillation tower passed through the condenser 70 was discharged at a temperature of 10°C.

[0073] Next, a stream containing an absorbent and a stream containing compressed conjugated diene monomers were obtained through a process performed in the vacuum compression section 30. The stream containing the absorbent was mixed with the bottom discharge stream of the distillation column to obtain a mixed stream, and the mixed stream was supplied to the first absorption column 100. The stream containing compressed conjugated diene monomers was mixed with a feed stream and circulated to the condensation section 10.

[0074] In the above examples and comparative examples, the operating conditions of the apparatus, the conjugated diene monomer recovery rate, the absorbent loss rate, and the occurrence of fouling are shown in Table 1 below.

[0075] The conjugated diene monomer recovery rate is expressed as a percentage by subtracting the mass flow rate of the conjugated diene monomer contained in the stream containing the uncondensed conjugated diene monomer from the mass flow rate of the conjugated diene monomer contained in the stream containing the uncondensed conjugated diene monomer.

[0076] The absorbent loss rate is expressed as a percentage of the mass flow rate of the absorbent contained in the top discharge stream of the first absorption tower and the stream containing the compressed conjugated diene-based monomer obtained from the vacuum compression section, relative to the mass flow rate of the absorbent contained in the mixed stream supplied to the first absorption tower.

[0077] [Table 1]

[0078] Referring to Table 1, it can be seen that the Examples equipped with a stripping column had an excellent conjugated diene monomer recovery rate of 100 wt%. Furthermore, it can be seen that Examples 1, 3, and 4, in which a cooling unit was provided at the top stage of the stripping column to control the upper temperature of the stripping column, did not experience fouling compared to Comparative Example 2 and had a better absorbent loss rate compared to Comparative Example 1. In particular, it can be seen that Example 1, in which the difference between the upper and lower temperatures of the stripping column was large, increased the separation efficiency of the stripping column. Specifically, it was found that the low temperature at the top of the stripping column facilitated absorbent condensation, resulting in the lowest absorbent loss rate among the Examples.

[0079] In contrast, in Comparative Example 1, which was equipped with a flash tank instead of a stripping column, the loss of the absorbent increased as the conjugated diene monomer and the absorbent were separated depending on the pressure and temperature of the flash tank, and it was confirmed that the absorbent loss rate was 1.8 times higher than in Example 1.

[0080] On the other hand, in Comparative Example 2, which included a distillation column instead of a stripping column, the distillation column was operated under vacuum, and under these conditions, the conjugated diene monomer was hardly condensed by the condenser upstream of the distillation column. As a result, the conjugated diene monomer was hardly condensed by the condenser upstream of the distillation column, and only the vaporized absorbent was condensed, resulting in a low reflux flow rate at the top of the distillation column. In this case, the low reflux flow rate at the top of the distillation column resulted in a minimal cooling effect at the top of the distillation column, making it difficult to control the temperature at the top of the distillation column, resulting in fouling. In this case, the occurrence of fouling was indirectly confirmed based on the temperature in the distillation column.

Claims

1. a step of supplying a feed stream containing a conjugated diene-based monomer to a condensation section and condensing the feed stream to obtain a stream containing a condensed conjugated diene-based monomer and a stream containing an uncondensed conjugated diene-based monomer; recovering the conjugated diene monomer from the stream containing the condensed conjugated diene monomer; supplying the stream containing the uncondensed conjugated diene monomer to a first absorption tower to contact it with an absorbent, thereby obtaining an absorbed solution in which the conjugated diene monomer is absorbed into the absorbent; supplying the absorption solution to a stripping column to separate the absorption solution into an absorbent and a conjugated diene-based monomer, circulating a bottom discharge stream from the stripping column containing the separated absorbent to a first absorption tower, and circulating an top discharge stream from the stripping column containing the separated conjugated diene-based monomer to the condensation section.

2. The feed stream containing the conjugated diene monomer is 2. The method for recovering a conjugated diene monomer according to claim 1, wherein the conjugated diene monomer is derived from a stream separated from a copolymer latex in a polymerization step in which a reactant containing a nitrile monomer and a conjugated diene monomer is polymerized to obtain the copolymer latex.

3. The feed stream containing the conjugated diene monomer is 3. The method for recovering a conjugated diene monomer according to claim 2, wherein the stream separated from the copolymer latex is supplied to a second absorption tower and the nitrile monomer is separated from the stream.

4. 2. The method for recovering a conjugated diene monomer according to claim 1, wherein the content of the conjugated diene monomer contained in the stream containing the uncondensed conjugated diene monomer is 80 to 95% by weight.

5. 2. The method for recovering a conjugated diene monomer according to claim 1, wherein the absorbent is a hydrocarbon compound having 6 to 30 carbon atoms.

6. 2. The method for recovering a conjugated diene monomer according to claim 1, wherein a mass flow rate at which the absorbent is introduced into the first absorption tower is 5 to 15 times a mass flow rate at which the stream containing the uncondensed conjugated diene monomer is supplied to the first absorption tower.

7. 2. The method for recovering a conjugated diene monomer according to claim 1, wherein the content of the conjugated diene monomer contained in the absorption solution is 5 to 20 wt %.

8. 2. The method for recovering a conjugated diene monomer according to claim 1, wherein the stripping column comprises a cooling section at the top stage.

9. 9. The method for recovering a conjugated diene monomer according to claim 8, wherein the cooling section controls the temperature at a height of 0 to 20% of the top of the stripping column relative to 0% to be 10°C to 30°C.

10. before recycling the top discharge stream of the stripping column to the condensation section, 2. The method for recovering a conjugated diene-based monomer according to claim 1, further comprising the steps of supplying the top discharge stream of the stripping column to a vacuum compression section to compress it, supplying a stream containing an absorbent to a first absorption tower, and circulating the compressed stream containing the conjugated diene-based monomer to the condensation section.

11. The operating pressure of the first absorption tower is 2 to 5 kgf / cm 2 The method for recovering a conjugated diene monomer according to claim 1, wherein the above-mentioned (g) is the same as above.

12. The operating pressure of the stripping column is −0.9 to −0.1 kgf / cm 2 The method for recovering a conjugated diene monomer according to claim 1, wherein the above-mentioned (g) is the same as above.

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