Apparatus and method for recovering valuable components in olefin copolymer off-gas

Abstract

The application discloses a device for recycling effective components in olefin copolymer exhaust gas, which comprises a light component separation tower, a heavy component separation tower, an exhaust gas absorption unit, at least two levels of flash tanks, and a separator. The first inlet end of the exhaust gas absorption unit is communicated with the outlet end of the light component separation tower, and the second inlet end of the exhaust gas absorption unit is communicated with the outlet end of the heavy component separation tower. The inlet end of the first level of flash tanks is communicated with the outlet end of the exhaust gas absorption unit, the outlet end at the bottom of the first level of flash tanks is communicated with the inlet end of the second level of flash tanks, and the outlet end at the bottom of the second level of flash tanks is communicated with the light component separation tower. The inlet end of the separator is communicated with the outlet end at the top of the second level of flash tanks. The application also discloses a method. Compared with the prior art, the application can improve the recycling efficiency of effective components and make the effective components directly participate in the cyclic reaction of the copolymer.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer preparation, and in particular relates to a device and method for recovering effective components in olefin copolymer exhaust gas. Background Art

[0002] Olefin copolymers are polymeric compounds formed by the addition polymerization of multiple monomers (small molecule olefins, such as ethylene, propylene, 1-butene, 1-pentene, and 1-octene). Olefin copolymers are generally obtained by the addition polymerization of two or more olefin monomers. Common examples include ethylene-1-butene copolymers, ethylene-1-octene copolymers, and propylene-1-octene copolymers. After years of development, the polymerization process for olefin copolymers has become relatively mature, with common polymerization processes including gas-phase polymerization, slurry polymerization, solution polymerization, and bulk polymerization. For example, in olefin copolymer elastomers, the light monomers (light monomers are olefins with four or fewer carbon atoms) are ethylene or propylene, and the heavy comonomers (heavy comonomers are alpha-olefins with eight or more carbon atoms) are 1-octene, 1-decene, and the like.

[0003] No matter which polymerization process is mentioned above, the production process of olefin copolymers needs to solve the common problem of exhaust gas treatment. At the moment when olefin copolymer reaction catalyst systems are becoming increasingly mature, the single-pass conversion rate of the polymerization process is still limited. After the olefin monomers that do not participate in the reaction leave the reactor, they need to be pressurized as circulating gas and then return to the reactor to continue the reaction to ensure the high monomer conversion rate of the final addition polymerization. The addition polymerization of macromolecules is a complicated process. During the circulation process of the circulating gas, there will be an enrichment phenomenon of inert gas (such as reaction byproducts, and small molecule alkanes with 1-6 carbon atoms such as ethane and propane of olefin hydrogenation reaction, nitrogen, etc.). The enrichment of inert gas in the reactor will have a significant impact on the partial pressure control of reactor hydrogen, and the partial pressure control of reactor hydrogen is the main means of molecular weight regulation of olefin copolymers. In order to avoid the enrichment of inert gas, it is usually necessary to process a part of the circulating gas as exhaust gas in the polymerization process of olefin copolymers. Typically, hydrocarbon components account for 5-40% of the total exhaust gas volume, and the ethylene and propylene contained in the exhaust gas account for approximately 0.4-1% of the olefin copolymer production volume. In early olefin copolymer plants, exhaust gas was typically burned in a flare system, resulting in significant waste of olefin monomers and environmental pollution during the flare process. Therefore, recovering the active components in the exhaust gas (monomers such as ethylene and propylene, and solvents such as hexane) can not only significantly reduce unit consumption and improve economic efficiency, but also mitigate environmental pollution.

[0004] With the increasing demands for environmental protection and economic benefits, the treatment methods for olefin copolymer exhaust gas have made great progress. Currently, olefin copolymer plants often use pressure swing adsorption (PSA), membrane separation, compression condensation, cryogenics and other methods to treat exhaust gas. However, the effective component recovery rate, energy consumption and investment of these methods vary greatly, and various problems exist in actual use.

[0005] For example, Chinese invention patent ZL201110225097.2, "Process for Treating Polyolefin Tail Gases by High- and Low-Pressure Adsorption" (authorization publication number CN102389682B), discloses a method for treating high- and low-pressure olefin copolymer exhaust gases generated during the production of polyethylene and polypropylene. This method utilizes a pressure swing adsorption process, employing at least four adsorbent-filled refining beds, each of which sequentially undergoes low-pressure adsorption, high-pressure adsorption, sequential discharge, concentration, vacuuming, vacuum cleaning, and pressurization. This method can separate hydrocarbons from nitrogen and hydrogen through pressure swing adsorption, but it cannot separate olefins from alkanes. The recovered hydrocarbon-rich gas can only be sent to a cracking plant for recycling or condensation, and cannot participate in the recycling reaction.

[0006] Another example is Chinese invention patent number ZL200910038599.7, "A Method for Completely Recycling Tail Gas from a Polyethylene Plant" (authorization publication number CN101530711B), which discloses a method for completely recycling exhaust gas from a polyethylene plant. This method utilizes a combination of membrane separation technology and pressure swing adsorption technology. This process feeds the exhaust gas from the high-pressure condensate tank of the polyethylene plant into a membrane separation recovery system, recovering a certain amount of ethylene and comonomers (butene, hexene, octene), along with an induced condensing agent (isopentane, hexane), which are returned to the inlet of the recycle compressor. The membrane-separated exhaust gas is then passed through a pressure swing adsorption system to adsorb hydrocarbon components, producing hydrogen and nitrogen for use as plant purge gas. The pressure swing adsorption system then desorbs the hydrocarbon-rich gas under vacuum conditions, which is then burned as fuel. While this method can recover hydrocarbons, the proportion of hydrocarbons recovered for the recycle reaction is limited, and a significant amount of hydrocarbons is still consumed as fuel. Summary of the Invention

[0007] The first technical problem to be solved by the present invention is to provide a device for recovering effective components in olefin copolymer exhaust gas in response to the current status of the existing technology, so as to improve the recovery efficiency of the effective components and enable the effective components to directly participate in the circulation reaction of the copolymer.

[0008] The second technical problem to be solved by the present invention is to provide a method for recovering effective components from the exhaust gas of olefin copolymers using the above-mentioned device.

[0009] The technical solution adopted by the present invention to solve the above-mentioned first technical problem is: a device for recovering effective components in olefin copolymer exhaust gas, comprising:

[0010] A light component separation tower, the top of which is provided with an outlet for outputting tail gas containing light component monomers;

[0011] a heavy component separation tower having an outlet at the top thereof for outputting the medium containing the heavy component comonomer;

[0012] It is characterized by also including:

[0013] an exhaust gas absorption unit, wherein a first inlet end thereof is connected to the outlet end of the light component separation tower, and a second inlet end thereof is connected to the outlet end of the heavy component separation tower;

[0014] At least two stages of flash tanks, namely a first stage flash tank and a second stage flash tank, wherein the inlet end of the first stage flash tank is connected to the outlet end of the exhaust gas absorption unit, the outlet end at the bottom of the first stage flash tank is connected to the inlet end of the second stage flash tank, and the outlet end at the bottom of the second stage flash tank is connected to the light component separation tower;

[0015] The separator is used to separate the light component monomers from the gas phase components, and its inlet end is connected to the outlet end of the top of the second-stage flash tank, and its outlet end is connected to the outlet pipeline of the copolymer reaction unit or the light component separation tower.

[0016] In this way, the heavy comonomer acts as an absorbent in the exhaust gas absorption unit, effectively absorbing the light monomers discharged from the light monomer separation tower. A primary flash evaporation process removes non-condensable gases (such as nitrogen and hydrogen) generated during the polymerization process. A secondary flash evaporation process and separation in a separator efficiently remove alkanes, resulting in effective light monomers. This reduces the raw material consumption of the olefin copolymer plant and improves economic efficiency. The components discharged from the separator can directly participate in the copolymer cycle reaction.

[0017] Preferably, the exhaust gas absorption unit is a high-pressure mixer or a gas-phase absorption tower or a combination of the two. The high-pressure mixer and the gas-phase absorption tower are both prior art.

[0018] Preferably, a gas compressor and a first heater are sequentially provided on the connecting pipeline between the outlet end of the light component separation tower and the first inlet end of the exhaust gas absorption unit, and the gas compressor is located upstream of the first heater;

[0019] A pressure pump and a second heater are sequentially provided on the connecting pipeline between the outlet end of the heavy component separation tower and the second inlet end of the exhaust gas absorption unit, and the pressure pump is located upstream of the second heater.

[0020] The outlet pressure of the gas compressor is 2.7~3.1MPa(A).

[0021] Preferably, a reflux tank is further provided on the connecting pipeline between the outlet end of the light component separation tower and the first inlet end of the exhaust gas absorption unit. The reflux tank is located upstream of the gas compressor, and the outlet end at the top of the reflux tank is connected to the inlet end of the gas compressor, the inlet end 1 in the middle of the reflux tank is connected to the outlet end at the top of the light component separation tower, the inlet end 2 in the middle of the reflux tank is connected to the outlet end of the separator, and the outlet end at the bottom of the reflux tank is connected to the inlet end at the top of the light component separation tower;

[0022] Meanwhile, the outlet end of the gas compressor is connected to a circulation pipeline, which is connected to the copolymer reaction unit.

[0023] In each of the above schemes, preferably, the separator is a membrane separator having a separation membrane, and the separation membrane is arranged to allow only light component monomers to pass therethrough.

[0024] Preferably, a first pressure reducing valve is provided on the connecting pipeline between the inlet end of the separator and the outlet end of the top of the second-stage flash tank; a second pressure reducing valve is provided on the pipeline connected to the outlet end of the top of the first-stage flash tank.

[0025] The technical solution adopted by the present invention to solve the second technical problem is: a method for recovering effective components from olefin copolymer exhaust gas using the above-mentioned device, characterized by the following steps:

[0026] 1. Mixing the tail gas containing light component monomers output from the outlet of the light component separation tower and the medium containing heavy component comonomers output from the outlet of the heavy component separation tower in an exhaust gas absorption unit, so that the heavy component comonomers in the medium act as an absorbent to absorb the light component monomers in the tail gas, wherein the tail gas entering the exhaust gas absorption unit is referred to as the first stream, and the medium entering the exhaust gas absorption unit is referred to as the second stream. The mass flow rate ratio of the first stream to the second stream is 1:2.1 to 1:3.3, and the operating pressure of the exhaust gas absorption unit is 2.7 to 3.0 MPa(A), and the operating temperature is 240 to 270° C.;

[0027] 2. The fluid output from the outlet end of the exhaust gas absorption unit enters the first-stage flash tank for primary flash evaporation, and the gaseous phase component after the primary flash evaporation is vented as exhaust gas. The liquid phase component after the primary flash evaporation enters the second-stage flash tank for secondary flash evaporation. The gaseous phase component after the secondary flash evaporation enters the separator, and the required effective components are output from the outlet end of the separator. The liquid phase component after the secondary flash evaporation is transported to the above-mentioned light component separation tower, wherein the pressure of the above-mentioned primary flash evaporation is 0.4~0.6MPa(A), and the pressure of the secondary flash evaporation is 0.15~0.25MPa(A).

[0028] The "A" in MPa(A) in the above pressure units refers to absolute pressure.

[0029] Preferably, the light component monomer is an olefin having 2 to 4 carbon atoms; and the heavy component comonomer is an olefin having 8 or more carbon atoms.

[0030] Preferably, the light component monomer is ethylene; and the heavy component comonomer is 1-octene.

[0031] Compared with the existing technology, the present invention has the following advantages: by adding an exhaust gas absorption unit, at least two flash tanks, and a separator to the existing light component separation tower and heavy component separation tower, the heavy component comonomer acts as an absorbent in the exhaust gas absorption unit to effectively absorb the light component monomer discharged from the light component separation tower. After a first-stage flash evaporation, non-condensable gases (such as nitrogen and hydrogen) generated during the polymerization process are removed. After a second-stage flash evaporation and separation in the separator, alkanes are efficiently removed to obtain effective light component monomer, thereby reducing the raw material consumption of the olefin copolymerization device and improving economic benefits. In addition, the components discharged from the separator can directly participate in the copolymer circulation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic structural diagram of Example 1 of the present invention;

[0033] Figure 2 This is a structural diagram of Example 4 of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0035] Example 1:

[0036] like Figure 1 As shown, a preferred embodiment 1 of the device and method for recovering effective components in olefin copolymer exhaust gas of the present invention is shown, wherein the device includes a light component separation tower 1, a heavy component separation tower 2, an exhaust gas absorption unit 3, a flash tank and a separator 6.

[0037] The top of the light component separation tower 1 is provided with an outlet for outputting tail gas containing light component monomers.

[0038] The top of the heavy component separation tower 2 is provided with an outlet for discharging the medium containing the heavy component comonomer.

[0039] In this embodiment, similar to the prior art, the bottom of the light component separation tower 1 passes through the primary separation system 7 and the solvent separation system 8 in sequence and is then connected to the heavy component separation tower 2 .

[0040] The exhaust gas absorption unit 3 is a high-pressure mixer, whose first inlet end is connected to the outlet end of the light component separation tower 1, and whose second inlet end is connected to the outlet end of the heavy component separation tower 2. A reflux tank 13, a gas compressor 11, and a first heater 12 are sequentially provided on the connecting pipeline between the outlet end of the light component separation tower 1 and the first inlet end of the exhaust gas absorption unit 3. The gas compressor 11 is located upstream of the first heater 12 and downstream of the reflux tank 13. The outlet end at the top of the reflux tank 13 is connected to the inlet end of the gas compressor 11, the inlet end in the middle of the reflux tank 13 is connected to the outlet end at the top of the light component separation tower 1, and the outlet end at the bottom of the reflux tank 13 is connected to the inlet end at the top of the light component separation tower 1. At the same time, the outlet end of the gas compressor 11 is connected to a circulation pipeline 111, which is connected to the copolymer reaction unit. A pressure pump 21 and a second heater 22 are sequentially provided on the connecting pipeline between the outlet end of the heavy component separation tower 2 and the second inlet end of the exhaust gas absorption unit 3 . The pressure pump 21 is located upstream of the second heater 22 .

[0041] The above-mentioned flash tank has two stages, namely a first-stage flash tank 4 and a second-stage flash tank 5, wherein the inlet end of the first-stage flash tank 4 is connected to the outlet end of the exhaust gas absorption unit 3, and a second pressure reducing valve 41 is provided on the pipeline connected to the outlet end of the top of the first-stage flash tank 4. The outlet end of the bottom of the first-stage flash tank 4 is connected to the inlet end of the second-stage flash tank 5, and the outlet end of the bottom of the second-stage flash tank 5 is connected to the light component separation tower 1.

[0042] The separator 6 is a membrane separator having a separation membrane arranged to allow only the light monomer to pass through. The inlet of the separator 6 is connected to the outlet at the top of the second-stage flash tank 5, and a first pressure reducing valve 51 is provided on the connecting pipeline. The outlet of the separator 6 is also connected to the second inlet at the middle of the reflux tank 13.

[0043] The second pressure reducing valve 41 reduces the pressure to 0.5 MPa (A), and the exhaust gas discharged from the outlet end of the top of the first-stage flash tank can enter the flare system for combustion treatment.

[0044] The first pressure reducing valve 51 reduces the pressure to 0.23 MPa (A).

[0045] The method steps for recovering the effective components in the olefin copolymer exhaust gas using the device of this embodiment are as follows:

[0046] I. The tail gas (temperature 30℃, pressure 0.2MPa(A)) with light component monomer (ethylene) outputted from the outlet end of the light component separation tower 1 and the medium with heavy component comonomer (1-octene) outputted from the outlet end of the heavy component separation tower 2 are respectively pressurized and heated, and then mixed in the vent gas absorption unit 3, so that the heavy component comonomer in the medium absorbs the light component monomer in the tail gas as an absorbent, wherein the tail gas entering the vent gas absorption unit 3 is the first stream, the medium entering the vent gas absorption unit 3 is the second stream, the flow rate of the first stream is 1873kg / h, the flow rate of the second stream is 3933.3kg / h, the operating pressure of the vent gas absorption unit 3 is 2.7MPa(A), and the operating temperature is 244℃.

[0047] II. The fluid outputted from the outlet end of the vent gas absorption unit 3 enters the first-stage flash tank 4 for first-stage flashing, the gas-phase component after the first-stage flashing is vented, the liquid-phase component after the first-stage flashing enters the second-stage flash tank 5 for second-stage flashing, the gas-phase component after the second-stage flashing enters the separator 6, the required effective component is outputted from the outlet end of the separator 6, and the liquid-phase component after the second-stage flashing is transported to the light component separation tower 1, wherein the pressure of the first-stage flashing is 0.5MPa(A), and the pressure of the second-stage flashing is 0.23MPa(A).

[0048] The results of the embodiment are shown in Table 1 below, wherein "inlet tail gas" in the table refers to the first stream, "recovered light hydrocarbon gas" refers to the stream outputted from the outlet end of the separator 6, "vent gas" refers to the stream discharged from the outlet end at the top of the first-stage flash tank 4, and "recovered liquid" refers to the stream outputted from the outlet end at the bottom of the second-stage flash tank 5.

[0049] Table 1

[0050]

[0051]

[0052] The present application introduces the vent gas absorption unit 3 and the flash separation unit (such as the components defined by the dotted box in the middle) to the original olefin copolymer device. Figure 1 Based on the principle of "like dissolves like", the heavy component comonomer 1-octene is selected as the absorbent to effectively absorb the monomer ethylene in the vent tail gas (i.e. the first stream). The liquid-phase absorption of ethylene is essentially a physical absorption process, increasing the gas-phase partial pressure of ethylene is to increase the mass transfer driving force, and low temperature is conducive to improving the solubility of ethylene, and selecting low temperature and high pressure operating conditions is conducive to absorbing the effective components of the tail gas.

[0053] The critical pressure, critical temperature and boiling point data of several components involved in the present application are shown in Table 2 below:

[0054] Table 2

[0055]

[0056] In the present application, the operating temperature of the vent gas absorption unit 3 is higher than the critical temperature of ethylene, propylene and n-hexane, and is lower than the critical temperature of 1-octene; the operating pressure is higher than the critical pressure of 1-octene, and is lower than the critical pressure of ethylene, propylene and n-hexane. The effective components in the tail gas and the absorbent are in a subcritical state, and the effective components cannot be liquefied, and the absorbent cannot be gasified. In the subcritical state, the molecular diffusion performance of ethylene, propylene and the like is significantly enhanced, and the mass transfer speed is accelerated, and compared with other conventional absorption unit operations, good absorption effect is expected to be achieved.

[0057] The present application preferably uses 1-octene as the absorbent, which has good solubility for ethylene, and also has a high boiling point (122-123℃) and is difficult to gasify. If a lower boiling point absorbent (such as hexane) is used, a large amount of absorbent will be gasified after flash separation, which will seriously reduce the separation effect and thus reduce the economic efficiency of the separation operation.

[0058] The present application uses two-stage flash evaporation, which aims to maximize the recovery of effective components (ethylene and hexane) in the vent gas. The incondensable gas (nitrogen and hydrogen) accumulated in the device during production is removed by the first-stage flash evaporation, and the alkanes are further removed by the separator 6 in the second-stage flash evaporation, thereby reducing the raw material consumption of the olefin copolymer device and improving the economic benefit.

[0059] Example 2

[0060] This example is basically the same as Example 1, except that the method parameters are different. In this example, the flow rate of the second stream in step one is 5244.4 kg / h, and the results of this example are shown in Table 3 below:

[0061] Table 3

[0062]

[0063] Example 3

[0064] This example is basically the same as Example 1, except that the method parameters are different. In this example, the operating pressure of the vent gas absorption unit 3 in step one is 2.9 MPa(A), and the operating temperature is 248℃; the flow rate of the second stream is 5244.4 kg / h, and the results of this example are shown in Table 4 below:

[0065] Table 4

[0066]

[0067] The results of the analysis of Examples 1-3 above are as follows:

[0068] Hydrocarbon recovery rate (%) Exhaust gas flow kg / h Example 1 78.07 1341.9 Example 2 84.13 1305.76 Example 3 89.25 1285.53

[0069] It can be seen from the above three embodiments that the method of the present invention for recovering effective components of exhaust gas from heavy comonomers can achieve efficient recovery of effective components of exhaust gas without introducing a medium from a non-reaction system. The recovery rate of hydrocarbons is very high, which saves energy investment and reduces the unit consumption of the reaction.

[0070] Example 4:

[0071] like Figure 2 The following is a preferred embodiment 4 of the apparatus and method for recovering effective components from olefin copolymer exhaust gas according to the present invention. This embodiment is substantially the same as the first embodiment, except that the exhaust gas absorption unit 3 is a gas phase absorption tower. The results of this embodiment are shown in Table 5 below:

[0072] Table 5

[0073]

[0074] Example 5:

[0075] This embodiment is basically the same as Example 1, except that in this embodiment, the exhaust gas absorption unit 3 is a combination of a high-pressure mixer and a gas-phase absorption tower, which are connected in series. The first and second streams first enter the high-pressure mixer for primary absorption and then enter the gas-phase absorption tower for secondary absorption. The streams after the secondary absorption undergo subsequent flash evaporation. The pressure in the high-pressure mixer is 3.1 MPa(A) and the operating temperature is 263°C. The pressure in the gas-phase absorption tower is 3.0 MPa(A), which is slightly lower than the pressure in the high-pressure mixer, and the operating temperature in the gas-phase absorption tower is 262°C. The results of this embodiment are shown in Table 6 below:

[0076] Table 6

[0077]

[0078]

[0079] Example 6:

[0080] This example is essentially the same as Example 1, except for the different method parameters. In this example, the operating pressure of the exhaust gas absorption unit 3 in step 1 is 3.0 MPa(A) and the operating temperature is 270°C; the pressure of the first flash evaporation in step 2 is 0.4 MPa(A), and the pressure of the second flash evaporation is 0.15 MPa(A). The results of this example are shown in Table 7 below:

[0081] Table 7

[0082]

[0083]

[0084] Example 7:

[0085] This example is essentially the same as Example 1, except for the different method parameters. In this example, the operating pressure of the exhaust gas absorption unit 3 in step 1 is 2.8 MPa(A) and the operating temperature is 240°C; the pressure of the first flash evaporation in step 2 is 0.6 MPa(A), and the pressure of the second flash evaporation is 0.25 MPa(A). The results of this example are shown in Table 8 below:

[0086] Table 8

[0087]

[0088]

[0089] The above examples 3 to 7 were analyzed and the results were as follows:

[0090] Hydrocarbon recovery rate (%) Exhaust gas flow kg / h Example 3 89.25 1285.53 Example 4 73.52 1356.2 Example 5 86.67 1306.7 Example 6 74.27 1360.8 Example 7 79.18 1328.2

[0091] As can be seen from Examples 3-7, the present invention's method for recovering effective components from exhaust gas using heavy comonomers achieves efficient recovery of effective components from exhaust gas without the need for introducing non-reactive media. High hydrocarbon recovery rates are achieved, saving energy investment and reducing unit reaction costs. In particular, Example 5, utilizing a combination of a gas-phase absorption tower and a high-pressure mixer, achieves a higher hydrocarbon recovery rate while using less heavy absorption monomer than in Example 3.

Claims

1. A device for recovering effective components in olefin copolymer exhaust gas, comprising: A light component separation tower (1) has an outlet at its top for outputting tail gas containing light component monomers; A heavy component separation tower (2) having an outlet at its top for discharging the medium containing the heavy component comonomer; It is characterized by Also included are: an exhaust gas absorption unit (3), a first inlet end of which is connected to the outlet end of the light component separation tower (1), and a second inlet end of which is connected to the outlet end of the heavy component separation tower (2); At least two stages of flash tanks, namely a first stage flash tank (4) and a second stage flash tank (5), wherein the inlet end of the first stage flash tank (4) is connected to the outlet end of the exhaust gas absorption unit (3), the outlet end at the bottom of the first stage flash tank (4) is connected to the inlet end of the second stage flash tank (5), and the outlet end at the bottom of the second stage flash tank (5) is connected to the light component separation tower (1); A separator (6) for separating light component monomers from the gas phase components, wherein the inlet end of the separator is connected to the outlet end at the top of the second-stage flash tank (5), and the outlet end of the separator is connected to the outlet pipeline of the copolymer reaction unit or the light component separation tower (1); A gas compressor (11) and a first heater (12) are sequentially provided on a connecting pipeline between the outlet end of the light component separation tower (1) and the first inlet end of the exhaust gas absorption unit (3), wherein the gas compressor (11) is located upstream of the first heater (12); A pressure pump (21) and a second heater (22) are sequentially provided on the connecting pipeline between the outlet end of the heavy component separation tower (2) and the second inlet end of the exhaust gas absorption unit (3), and the pressure pump (21) is located upstream of the second heater (22).

2. The device according to claim 1, characterized in that: The exhaust gas absorption unit (3) is a high-pressure mixer or a gas phase absorption tower or a combination of the two.

3. The device according to claim 1, characterized in that: A reflux tank (13) is further provided on the connecting pipeline between the outlet end of the light component separation tower (1) and the first inlet end of the exhaust gas absorption unit (3). The reflux tank (13) is located upstream of the gas compressor (11), and the outlet end at the top of the reflux tank (13) is connected to the inlet end of the gas compressor (11), the inlet end 1 at the middle of the reflux tank (13) is connected to the outlet end at the top of the light component separation tower (1), the inlet end 2 at the middle of the reflux tank (13) is connected to the outlet end of the separator (6), and the outlet end at the bottom of the reflux tank (13) is connected to the inlet end at the top of the light component separation tower (1); Meanwhile, the outlet end of the gas compressor (11) is connected to a circulation pipeline (111), and the circulation pipeline (111) is connected to the copolymer reaction unit.

4. The device according to any one of claims 1 to 3, characterized in that: The separator (6) is a membrane separator having a separation membrane, and the separation membrane is arranged to allow only light component monomers to pass therethrough.

5. The device according to claim 4, characterized in that: A first pressure reducing valve (51) is provided on the connecting pipeline between the inlet end of the separator (6) and the outlet end at the top of the second-stage flash tank (5); and a second pressure reducing valve (41) is provided on the pipeline connected to the outlet end at the top of the first-stage flash tank (4).

6. A method for recovering effective components from olefin copolymer exhaust gas using the device according to any one of claims 1 to 5, characterized in that Here are the steps:

1. The tail gas containing light component monomers output from the outlet of the light component separation tower (1) and the medium containing heavy component comonomers output from the outlet of the heavy component separation tower (2) are mixed in an exhaust gas absorption unit (3), so that the heavy component comonomers in the medium act as an absorbent to absorb the light component monomers in the tail gas, wherein the tail gas entering the exhaust gas absorption unit (3) is referred to as the first stream, and the medium entering the exhaust gas absorption unit (3) is referred to as the second stream. The mass flow ratio of the first stream to the second stream is 1:2.1 to 1:3.

3. The operating pressure of the exhaust gas absorption unit (3) is 2.7 to 3.0 MPa(A), and the operating temperature is 240 to 270°C.

2. The fluid output from the outlet of the exhaust gas absorption unit (3) enters the first-stage flash tank (4) for primary flash evaporation, and the gaseous phase component after the primary flash evaporation is discharged as exhaust gas. The liquid phase component after the primary flash evaporation enters the second-stage flash tank (5) for secondary flash evaporation, and the gaseous phase component after the secondary flash evaporation enters the separator (6). The required effective components are output from the outlet of the separator (6), and the liquid phase component after the secondary flash evaporation is transported to the above-mentioned light component separation tower (1), wherein the pressure of the above-mentioned primary flash evaporation is 0.4~0.6MPa(A), and the pressure of the secondary flash evaporation is 0.15~0.25MPa(A).

7. The method according to claim 6, characterized in that: The light component monomer is an olefin with 2 to 4 carbon atoms; the heavy component comonomer is an olefin with 8 or more carbon atoms.

8. The method according to claim 7, wherein: The light component monomer is ethylene; the heavy component comonomer is 1-octene.

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