Polyethylene elastomer process tail gas treatment device and process

Abstract

The invention discloses a polyethylene elastomer process tail gas treatment device and process, and belongs to the technical field of tail gas treatment devices. The system further comprises a first-section compressor, a first-section separation tank feeding heat exchanger, a first-section separation tank, a second-section compressor, a second-section separation tank feeding heat exchanger, a second-section separation tank, a dehydrogenation tower feeding cooler, a dehydrogenation tower top cooler, a dehydrogenation tower return tank and a third-section compressor. A gas outlet of the dehydrogenation tower top cooler is connected with a gas inlet of the dehydrogenation tower return tank through a pipeline, a gas outlet of the dehydrogenation tower return tank is connected with a gas inlet of the third-section compressor through a pipeline, an online monitoring instrument c is arranged on the pipeline, and a gas outlet of the third-section compressor is connected with a pipeline, and an adjusting valve g is arranged on the pipeline; the hydrogen, ethylene and 1-octylene separation system and method have the advantages that the integration level is high, the pertinence on the separation of hydrogen, ethylene and 1-octylene is high, the process is free of pollution, and the recovery efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of tail gas treatment devices, in particular to a polyethylene elastomer process tail gas treatment device. Background Art

[0002] Polyolefin elastomers have high molecular weight and long chain structure, showing excellent elasticity, chemical resistance and heat resistance, and good processing performance and compatibility. Once discovered, they have been popular in the market and have been dubbed "high-end polyolefin materials". With the increase of disposable income of domestic people, people's demand for improving the quality of life is increasing. The multi-scenario, environmental protection properties and weather resistance of polyolefin elastomers are widely used by various home appliances, automobiles, footwear and other manufacturers, effectively improving the quality of products that people directly contact.

[0003] Our company has completed the development of polyolefin elastomer catalysts, small-scale tests and pilot experiments, and is getting closer and closer to the technically independent and controllable continuous production of polyolefin elastomers. However, we also found some problems during the experiment. For example, a tail gas will inevitably be produced during the polyolefin production process. The nature of this tail gas is relatively stable. It is a mixed gas composed of hydrogen, ethylene and 1-octene. Hydrogen is the light component, ethylene is the heavy component, and 1-octene is the super-heavy component. It only changes slightly when switching product grades. This tail gas has the characteristics of high hydrogen content and high content of high-value polymerization monomers. If this tail gas can be effectively recovered, the unit consumption of our polyolefin elastomer will be effectively reduced, further improving the competitiveness of our products.

[0004] Patent 201210438912.8 discloses an improved process for recovering non-methane hydrocarbons in polyolefin tail gas by adsorption, wherein each adsorption tower cycle sequentially undergoes the steps of low-pressure adsorption, pressure increase, pressure increase, high-pressure adsorption, pressure decrease, displacement, inversion, evacuation and pressure increase, or each adsorption tower cycle sequentially undergoes the steps of low-pressure adsorption, pressure increase, high-pressure adsorption, pressure decrease, displacement, inversion, evacuation and pressure increase.

[0005] Patent 202010681396.6 discloses a device and method for separating and recovering tail gas components of a polyolefin device, the device comprising: a pretreatment mechanism, which is used to receive raw gas and purge gas, mix and compress the gases to remove impurities such as heavy hydrocarbons, and then transport them to a cryogenic mechanism; a cryogenic mechanism, which is used to receive the mixed gas from the pretreatment mechanism, separate and recover the hydrocarbons therein, and discharge nitrogen-rich gas; a temperature-variable adsorption mechanism, which is divided into an adsorption unit and a desorption unit, the adsorption unit is used to receive the nitrogen-rich gas from the cryogenic mechanism and adsorb the hydrocarbons therein, and the desorption unit is used to receive the purge gas from the pretreatment mechanism, desorb the adsorbate, and return it to the pretreatment mechanism to increase the concentration of hydrocarbons entering the cryogenic mechanism.

[0006] Patent 202121647675.7 discloses a tail gas membrane recovery system for a polyolefin device, including a tank body, a drain pipe fixedly connected to the center of the bottom wall of the tank body, and multiple sets of separation plates evenly fixedly connected to the bottom of the fixed seat, multiple sets of separation membranes are arranged inside all the separation plates, and multiple sets of liquid guide grooves arranged front and back are arranged on the left of all the separation plates. First, multiple sets of steam pipes evenly arranged up and down are installed inside the recovery tank body, and the two adjacent sets of steam pipes are connected by the installed U-shaped steam guide pipes, so that the tail gas can flow through the multiple sets of steam pipes arranged up and down, and multiple sets of separation plates are installed inside the multiple sets of steam pipes, enter the top steam pipe, and pass through the separation membrane on the separation plate for the first separation, and ignite the remaining tail gas to continue to reduce the environmentally harmful components contained in it, and the burned gas is discharged cleanly through the exhaust net.

[0007] Patent 201610721758.3 discloses a method for recovering hydrocarbons from polyolefin tail gas by full-temperature adsorption extraction, including a hydrocarbon adsorption concentration process, a hydrocarbon extraction desorption process, a hydrocarbon separation and recovery process, and a PSA separation and purification of nitrogen process. The polyolefin tail gas first undergoes a hydrocarbon adsorption concentration process, and most of the C2+ hydrocarbon components are adsorbed in the adsorption tower. Nitrogen-rich gas flows out from the top of the tower and enters the PSA separation and purification of N2 process to obtain a N2 byproduct with a purity of 99%. The desorbed gas is pressurized and returned to the hydrocarbon adsorption concentration process to further recover N2 and C2+ hydrocarbon components. After the adsorption step is completed, a hydrocarbon extraction and desorption process is carried out to dissolve the effective component - C2+ hydrocarbon components. The extracted desorbed gas enters the hydrocarbon separation and recovery process, depressurizes or condenses and cools, and the non-condensable gas N2 escapes and mixes with the nitrogen-rich gas, and enters the PSA separation and purification of N2 process; then the extractant escapes and is recycled and reused after regeneration and recovery processing.

[0008] The above existing technologies basically adopt the technical routes of adsorption, membrane recovery and extraction. Pressure swing adsorption can achieve high-precision tail gas refinement, but it also brings the characteristics of high technical integration, high investment due to the large number of control valve groups and adsorbents, etc.; while membrane recovery has not seen a more mature ethylene separation membrane, and extraction technology has brought new impurities, which increases the possibility of potential product contamination while increasing impurity removal. What's more, some technical routes adopt the form of direct mixing and direct discharge to the atmosphere, which not only brings huge waste but also increases the emission of carbon dioxide. Summary of the invention

[0009] In order to solve the technical problems mentioned in the above background technology, the present invention provides a polyethylene elastomer process tail gas treatment device, and the technical solution adopted is as follows: The invention comprises a dehydrogenation tower, a first-stage compressor, a first-stage separator tank feed heat exchanger, a first-stage separator tank, a second-stage compressor, a second-stage separator tank feed heat exchanger, a second-stage separator tank, a dehydrogenation tower feed cooler, a dehydrogenation tower top cooler, a dehydrogenation tower reflux tank and a third-stage compressor, wherein the air inlet of the first-stage compressor is connected with a pipeline, the air outlet of the first-stage compressor and the air inlet of the first-stage separator tank feed heat exchanger are connected through a pipeline, the air outlet of the first-stage separator tank feed heat exchanger is connected with the air inlet of the first-stage separator tank through a pipeline, the first-stage separator tank is provided with a first control loop, the air outlet of the first-stage separator tank is connected with the air inlet of the second-stage compressor through a pipeline, the air outlet of the second-stage compressor and the air inlet of the second-stage separator tank feed heat exchanger are connected through a pipeline, the air outlet of the second-stage separator tank feed heat exchanger is connected with the air inlet of the second-stage separator tank The second control loop is connected through a pipeline, and the second control loop is provided on the second-stage separation tank, and the second control loop is connected to the first control loop. The air outlet of the second-stage separation tank is connected to the air inlet of the dehydrogenation tower feed cooler through a pipeline, and an online monitoring instrument a is provided on the pipeline. The air outlet of the dehydrogenation tower feed cooler is connected to the air inlet of the dehydrogenation tower through a pipeline. The third control loop is provided on the dehydrogenation tower, and the air outlet of the dehydrogenation tower is connected to the air inlet of the dehydrogenation tower top cooler through a pipeline, and an online monitoring instrument b is provided on the pipeline. The air outlet of the dehydrogenation tower top cooler is connected to the air inlet of the dehydrogenation tower reflux tank through a pipeline, and the air outlet of the dehydrogenation tower reflux tank is connected to the air inlet of the third-stage compressor through a pipeline, and an online monitoring instrument c is provided on the pipeline. The air outlet of the third-stage compressor is connected to a pipeline, and a regulating valve g is provided on the pipeline. The fourth control loop is provided on the dehydrogenation tower reflux tank, and the fourth control loop is connected to the dehydrogenation tower.

[0010] Furthermore, the first control loop includes a pipeline connected to the discharge port of the first inter-stage separation tank, and the pipeline is provided with a first inter-stage separation tank bottom delivery pump, a regulating valve a and an online monitoring instrument d, the pipeline where the regulating valve a is located is provided with a branch pipeline connected to the first intermittent separation tank, and the branch pipeline is provided with a regulating valve b, a computing controller a is commonly provided on the circuit lines on the regulating valves a and the regulating valves b, the circuit line on the computing controller a is connected to a liquid level meter a, and the liquid level meter a is connected to the first inter-stage separation tank.

[0011] Furthermore, the second control loop includes a pipeline connected between the discharge port of the second inter-stage separation tank and the pipeline where the regulating valve a is located, and a regulating valve c is arranged on the pipeline. The circuit line on the regulating valve c is connected to a liquid level meter b, and the liquid level meter b is connected to the second inter-stage separation tank.

[0012] Furthermore, the third control loop includes a pipeline connected to the discharge port of the dehydrogenation tower and an online monitoring instrument e and a regulating valve d are arranged on the pipeline. The circuit line on the regulating valve d is connected to a liquid level meter c, and the liquid level meter c is connected to the dehydrogenation tower.

[0013] Furthermore, the fourth control loop includes a pipeline connected to the discharge port of the dehydrogenation tower reflux tank and the dehydrogenation tower, and the pipeline is connected to the dehydrogenation tower top reflux pump and the regulating valve e, the circuit line of the regulating valve e is connected to the calculation controller b, the circuit line of the calculation controller b is connected to the liquid level meter d, the liquid level meter d is connected to the dehydrogenation tower reflux tank, and also includes a branch pipeline connected to the pipeline where the regulating valve e is located, and the branch pipeline is connected to the dehydrogenation tower reflux tank, the branch pipeline is provided with a regulating valve f, and the circuit line on the regulating valve f is connected to the calculation controller b.

[0014] The treatment process includes the following steps: Step 1: Adjust the first control loop so that the liquid level in the first-stage separation tank reaches 20%; Step 2: Adjust the second control loop so that the liquid level in the second-stage separation tank reaches 20%; Step 3: Adjust the third control loop to make the liquid level of the dehydrogenation tower reach 20%; Step 4: Adjust the fourth control loop to make the liquid level of the dehydrogenation tower reflux tank reach 20%; Step 5, the tail gas enters the first-stage compressor and is compressed, and then is accelerated to enter the first-stage separation tank feed heat exchanger for heat exchange, so that the tail gas is cooled. The cooled tail gas enters the first-stage separation tank, and the super-heavy component 1-octene in the tail gas becomes a liquid phase and remains in the first-stage separation tank. The 1-octene is discharged when the liquid level in the first-stage separation tank is maintained at 20%. The tail gas in the first-stage separation tank enters the second-stage compressor and is compressed, and then is accelerated to enter the second-stage separation tank feed heat exchanger for heat exchange, so that the tail gas is further cooled, and then enters the second-stage separation tank. The remaining 1-octene in the tail gas becomes a liquid phase and remains in the second-stage separation tank. When the liquid level in the second-stage separation tank is maintained at 20%, it is merged into the first control loop and discharged. After the tail gas in the inter-stage separation tank enters the feed cooler of the dehydrogenation tower for deep cooling, the tail gas enters the dehydrogenation tower, and only gaseous hydrogen and liquid ethylene are left in the tail gas. After adjustment by the third control loop, the liquid ethylene in the dehydrogenation tower is discharged while maintaining the liquid level at 20%. The hydrogen in the dehydrogenation tower is further cooled by the top cooler of the dehydrogenation tower and enters the reflux tank of the dehydrogenation tower. The residual liquid ethylene in the hydrogen remains in the reflux tank of the dehydrogenation tower. Under the adjustment of the fourth control loop, the liquid level in the reflux tank of the dehydrogenation tower is maintained at 20%, and the ethylene in the reflux tank of the dehydrogenation tower refluxes to the dehydrogenation tower. The hydrogen in the reflux tank of the dehydrogenation tower is discharged through the gas outlet of the reflux tank of the dehydrogenation tower. The above steps are used to complete the efficient and high-purity separation and recovery of hydrogen, ethylene and 1-octene in the tail gas.

[0015] The invention has the following advantages: by manually adjusting the first control loop and the fourth control loop, the liquid levels in the first inter-stage separation tank and the dehydrogenation tower reflux tank are respectively 30%, so that a liquid sealing layer is formed in the first inter-stage separation tank and the dehydrogenation tower reflux tank, and then by manually adjusting the first control loop and the fourth control loop, the liquid levels in the first inter-stage separation tank and the dehydrogenation tower reflux tank are respectively gradually reduced to 20%, and then the first control loop, the second control loop, the third control loop and the fourth control loop are automatically adjusted to keep the liquid levels in the first inter-stage separation tank, the second inter-stage separation tank, the dehydrogenation tower and the dehydrogenation tower reflux tank at 20%, so that high-purity separation and recovery of hydrogen, ethylene and 1-octene in tail gas is achieved. The invention has high integration, strong pertinence in separation of hydrogen, ethylene and 1-octene, no pollution in the process and high recovery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the process of the present invention.

[0017] Figures: 1 dehydrogenation tower, 2 first-stage compressor, 3 first-stage separator tank feed heat exchanger, 4 first-stage separator tank, 5 second-stage compressor, 6 second-stage separator tank feed heat exchanger, 7 second-stage separator tank, 8 dehydrogenation tower feed cooler, 9 dehydrogenation tower top cooler, 10 dehydrogenation tower reflux tank, 11 third-stage compressor, 12 online monitoring instrument a, 13 online monitoring instrument b, 14 online monitoring instrument c, 15 first-stage separator tank bottom delivery pump, 16 regulating valve a, 17 online monitoring instrument d, 18 regulating valve b, 19 calculation controller a, 20 liquid level gauge a, 21 regulating valve c, 22 liquid level gauge b, 23 online monitoring instrument e, 24 regulating valve d, 25 liquid level gauge c, 26 dehydrogenation tower top reflux pump, 27 regulating valve e, 28 calculation controller b, 29 liquid level gauge d, 30 regulating valve f, 31 regulating valve g, 32 regulating valve h. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Please refer to Figure 1 A polyethylene elastomer process tail gas treatment device includes a dehydrogenation tower 1, a first-stage compressor 2, a first-stage separation tank feed heat exchanger 3, a first-stage separation tank 4, a second-stage compressor 5, a second-stage separation tank feed heat exchanger 6, a second-stage separation tank 7, a dehydrogenation tower feed cooler 8, a dehydrogenation tower top cooler 9, a dehydrogenation tower reflux tank 10 and a third-stage compressor 11.

[0020] The air inlet of the first-stage compressor 2 is connected with a pipeline, and the tail gas from the polyolefin elastomer enters the first-stage compressor 2 through the pipeline. The air outlet of the first-stage compressor 2 and the air inlet of the first-stage separation tank feed heat exchanger 3 are connected through the pipeline. The first-stage compressor 2 compresses the tail gas and accelerates it to enter the first-stage separation tank feed heat exchanger 3 through the pipeline to cool the tail gas. The air outlet of the first-stage separation tank feed heat exchanger 3 is connected with the air inlet of the first-stage separation tank 4 through a pipeline. Due to the cooling of the tail gas, the super-heavy component 1-octene in the tail gas becomes a liquid phase and remains in the first-stage separation tank 4. The first-stage separation tank 4 is provided with a first control loop to control the liquid level height in the separation tank 4.

[0021] The gas outlet of the first-stage separator 4 is connected to the gas inlet of the second-stage compressor 5 through a pipeline. After 1-octene is separated from the first-stage separator 4, tail gas composed of hydrogen and ethylene is left. The tail gas enters the second-stage compressor 5 through a pipeline. The gas outlet of the second-stage compressor 5 is connected to the gas inlet of the feed heat exchanger 6 of the second-stage separator via a pipeline. The tail gas in the second-stage compressor 5 is compressed and accelerated to enter the feed heat exchanger 6 of the second-stage separator, so that the tail gas continues to cool down. The gas outlet of the device 6 is connected to the gas inlet of the second inter-stage separation tank 7 through a pipeline, the tail gas in the second inter-stage separation tank feed heat exchanger 6 enters the second inter-stage separation tank 7, and the residual 1-octene in the tail gas continues to fall into the second inter-stage separation tank 7 in the form of liquid phase. The second inter-stage separation tank 7 is provided with a second control loop, and the second control loop controls the liquid level height in the second inter-stage separation tank 7. The second control loop is connected to the first control loop, and the first control loop and the second control loop jointly control the discharge of 1-octene.

[0022] The gas outlet of the second-stage separation tank 7 is connected to the gas inlet of the dehydrogenation tower feed cooler 8 through a pipeline, and an online monitoring instrument a12 is arranged on the pipeline. The online monitoring instrument a12 monitors the dew point in the pipeline to prevent freezing and blockage in the pipeline. The tail gas enters the dehydrogenation tower feed cooler 8 through the pipeline for deep cooling. The gas outlet of the dehydrogenation tower feed cooler 8 is connected to the gas inlet of the dehydrogenation tower 1 through a pipeline. The deep-cooled tail gas enters the dehydrogenation tower 1 through the pipeline. The ethylene in the deep-cooled tail gas changes into liquid phase and falls into the dehydrogenation tower 1. The dehydrogenation tower 1 is provided with a third control loop, and the third loop controls the liquid level height in the dehydrogenation tower 1 and the discharge of ethylene.

[0023] The outlet of the dehydrogenation tower 1 is connected to the air inlet of the dehydrogenation tower top cooler 9 through a pipeline, and an online monitoring instrument b13 is arranged on the pipeline. The online monitoring instrument b13 monitors the heat load in the pipeline to prevent the pipeline from bursting. The tail gas in the dehydrogenation tower 1 enters the dehydrogenation tower top cooler 9 through a pipeline for cooling. The outlet of the dehydrogenation tower top cooler 9 is connected to the air inlet of the dehydrogenation tower reflux tank 10 through a pipeline. The cooled tail gas enters the dehydrogenation tower reflux tank 10 through the pipeline via the dehydrogenation tower top cooler 9. The residual ethylene in the tail gas continues to become a liquid phase and falls into the dehydrogenation tower reflux tank 10. The outlet of the dehydrogenation tower reflux tank 10 is connected to the air inlet of the third-stage compressor 11 through a pipeline, and an online monitoring instrument c14 is arranged on the pipeline. The online monitoring instrument c14 monitors the purity of the hydrogen in the pipeline. The hydrogen discharged from the gas outlet of the flow tank 10 enters the third-stage compressor 11 through a pipeline. The gas outlet of the third-stage compressor 11 is connected to a pipeline and a regulating valve g31 is arranged on the pipeline. The switch of the pipeline is controlled to open the regulating valve g31 to discharge the hydrogen in the pipeline. A branch pipeline is arranged on the pipeline where the regulating valve g31 is located. The branch pipeline is connected to the pipeline connected to the air inlet of the first-stage compressor 2 and a regulating valve h32 is arranged on the pipeline. If the online monitoring instrument c14 monitors that the purity of the hydrogen in the pipeline is impure, the regulating valve g31 is closed and the regulating valve h32 is opened. The hydrogen flows back to the first-stage compressor 2 through the line change. A fourth control loop is arranged on the dehydrogenation tower reflux tank 10. The fourth control loop is connected to the dehydrogenation tower 1. The fourth control loop controls the liquid level height in the dehydrogenation tower reflux tank 10.

[0024] The first control loop includes a pipeline connected to the discharge port of the first inter-stage separation tank 4, and the pipeline is provided with a first inter-stage separation tank bottom delivery pump 15, a regulating valve a16 and an online monitoring instrument d17, the online monitoring instrument d17 monitors the purity of 1-octene in the pipeline, the pipeline where the regulating valve a16 is located is provided with a branch pipeline connected to the first intermittent separation tank 4, and the branch pipeline is provided with a regulating valve b18, the regulating valve a16 and the regulating valve b18 can be manual or electric, and the circuit lines on the regulating valves a16 and the regulating valves b18 are jointly provided with a computing controller a19, the computing controller a19 controls the opening of the regulating valves a16 and the regulating valves b18, the circuit line on the computing controller a19 is connected with a liquid level meter a20, the signal of the liquid level meter a20 is fed back to the computing controller a19, and the liquid level meter a20 is connected to the first inter-stage separation tank 4.

[0025] The second control loop includes a pipeline connected between the discharge port of the second inter-stage separation tank 7 and the pipeline where the regulating valve a16 is located, and a regulating valve c21 is arranged on the pipeline. The circuit line on the regulating valve c21 is connected to a liquid level meter b22, and the liquid level meter b22 feeds back a signal to the regulating valve c21. The liquid level meter b22 is connected to the second inter-stage separation tank 7, and the liquid level meter b22 monitors the liquid level height in the second inter-stage separation tank 7.

[0026] The third control loop includes a pipeline connected to the discharge port of the dehydrogenation tower 1 and an online monitoring instrument e23 and a regulating valve d24 are arranged on the pipeline. The online monitoring instrument e23 monitors the purity of ethylene in the pipeline. The circuit line on the regulating valve d24 is connected to a liquid level meter c25. The liquid level meter c25 is connected to the dehydrogenation tower 1. The liquid level meter c25 feeds back a signal to the regulating valve d24. The liquid level meter c25 monitors the liquid level height in the dehydrogenation tower 1.

[0027] The fourth control loop includes a pipeline connected to the discharge port of the dehydrogenation tower reflux tank 10 and the dehydrogenation tower 1, and the pipeline is connected to the dehydrogenation tower top reflux pump 26 and the regulating valve e27, the circuit line of the regulating valve e27 is connected to the calculation controller b28, the circuit line of the calculation controller b28 is connected to the liquid level meter d29, the liquid level meter d29 monitors the liquid level height in the dehydrogenation tower reflux tank 10, the liquid level meter d29 is connected to the dehydrogenation tower reflux tank 10, and also includes a branch pipeline connected to the pipeline where the regulating valve e27 is located, and the branch pipeline is connected to the dehydrogenation tower reflux tank 10, the branch pipeline is provided with a regulating valve f30, and the circuit line on the regulating valve f30 is connected to the calculation controller b28, the liquid level meter d29 feeds back a signal to the calculation controller b28, the calculation controller b28 controls the opening of the regulating valve e27 and the regulating valve f30, and the regulating valve e27 and the regulating valve f30 can be either manual or electric.

[0028] Working principle of the present invention: The tail gas of the polyethylene elastomer process enters the first-stage compressor 2 through a pipeline, and after being compressed, it is accelerated to enter the first-stage separation tank feed heat exchanger 3, the tail gas is cooled, and then the tail gas enters the first-stage separation tank 4 through a pipeline through the first-stage separation tank feed heat exchanger 3. The 1-octene in the tail gas becomes a liquid phase and falls into the first-stage separation tank 4. At this time, the worker manually closes the regulating valve a16, opens the regulating valve b18, and starts the first-stage separation tank bottom delivery pump 15. The 1-octene in the first-stage separation tank 4 is pumped into the pipeline where the regulating valve b18 is located, so that the liquid phase 1-octene extracted from the first-stage separation tank 4 returns to the first-stage separation tank 4 until the liquid level in the first-stage separation tank 4 is monitored by the liquid level meter a20 to reach 30%. The liquid level in this process adopts a circulating reflux method in order to increase the residence time of 1-octene in the first-stage separation tank 4 and avoid the tail gas from being discharged from the first-stage separation tank 4 too quickly. The first use of liquid holding is also to form a liquid seal layer in the first-stage separation tank 4. Otherwise, the tail gas will also be pumped away under the negative pressure extracted by the delivery pump 15 at the bottom of the first-stage separation tank. After the liquid level in the first-stage separation tank 4 reaches 30%, the regulating valve a16 is opened, and the opening of the regulating valve b18 is reduced. The 1-octene in the first-stage separation tank 4 is discharged through the discharge port at the bottom thereof. In order to avoid the discharge flow rate being too fast and bringing out the tail gas, the opening of the regulating valve b18 is reduced, so that part of the 1-butene is directly discharged, and a small part returns to the first-stage separation tank 4, until the liquid level meter a20 monitors that the liquid level in the first-stage separation tank 4 is 20%, and then the calculation controller a19 adjusts the opening of the regulating valve a16 and the regulating valve b18, so that while the 1-butene is discharged, the liquid level in the first-stage separation tank 4 is always maintained at 20%; The tail gas in the first-stage separation tank 4 enters the second-stage compressor 5 through a pipeline, and after being compressed, it is accelerated through a pipeline to enter the second-stage separation tank feed heat exchanger 6, so that the tail gas is still kept cooled. Then, the tail gas in the second-stage separation tank feed heat exchanger 6 enters the second-stage separation tank 7, and the residual liquid 1-octene in the tail gas falls into the second-stage separation tank 7. The liquid level meter b22 monitors the liquid level in the second-stage separation tank 7 and feeds back a signal to the regulating valve c21. The regulating valve c21 adjusts the opening to keep the liquid level in the second-stage separation tank 7 at 20% at all times, forming a liquid seal layer to prevent the tail gas from being discharged from the bottom of the second-stage separation tank 7. The 1-octene in the second-stage separation tank 7 is discharged together through the pipeline into the pipeline where the regulating valve a16 is located; The tail gas in the second-stage separation tank 4 enters the dehydrogenation tower feed cooler 8 through a pipeline to cool the tail gas. The tail gas in the dehydrogenation tower feed cooler 8 enters the dehydrogenation tower 1 through a pipeline. The ethylene in the tail gas changes into a liquid phase and falls into the dehydrogenation tower 1. The liquid level meter c25 monitors the liquid level in the dehydrogenation tower 1 and feeds back a signal to the regulating valve d24 to adjust the opening, so that the liquid level in the dehydrogenation tower 1 is always maintained at 20% and discharged through the pipeline where the regulating valve d24 is located. The liquid level of ethylene forms a liquid seal layer in the dehydrogenation tower 1 to prevent the tail gas from being discharged from the bottom of the dehydrogenation tower 1. The tail gas in the dehydrogenation tower 1 enters the dehydrogenation tower top cooler 9 through a pipeline to continue to be cooled, and then enters the dehydrogenation tower reflux tank 10 through a pipeline. The liquid ethylene remaining in the tail gas falls into the dehydrogenation tower reflux tank 10. At this time, the manual adjustment valve e27 is closed and the regulating valve f30 is opened. Then, under the extraction of the dehydrogenation tower top reflux pump 26, the ethylene in the dehydrogenation tower reflux tank 10 is refluxed to the dehydrogenation tower reflux tank 10 through the pipeline where the regulating valve f is located. When the liquid level meter d29 monitors that the liquid level in the dehydrogenation tower top reflux tank 10 is 30%, the regulating valve e27 is opened, and the opening of the regulating valve f30 is reduced. The liquid ethylene in the dehydrogenation tower reflux tank 10 is discharged into the dehydrogenation tower through the pipeline where the regulating valve e27 is located. Tower 1, and a small part of it flows back to the dehydrogenation tower reflux tank 10 through the pipeline where the regulating valve f30 is located. Its purpose is the same as the regulation when the first inter-stage separation tank is used. Ethylene forms a liquid seal layer in the dehydrogenation tower reflux tank 10. When the liquid level meter d29 monitors that the liquid level in the dehydrogenation tower reflux tank 10 reaches 20%, the calculation controller b28 controls the opening of the regulating valve e27 and the regulating valve f30 to keep the liquid level in the dehydrogenation tower reflux tank 10 at 20%. At this time, the tail gas in the dehydrogenation tower reflux tank 10 is only hydrogen. The hydrogen in the dehydrogenation tower reflux tank 10 enters the third stage compressor 11 through the pipeline, and enters the pipeline where the regulating valve g31 is located after compression and acceleration. By initially manually adjusting the first inter-stage separation tank 4 and the dehydrogenation tower reflux tank 10, and then automatically adjusting the first inter-stage separation tank 4, the second inter-stage separation tank 7, the dehydrogenation tower 1 and the dehydrogenation tower reflux tank 10, the liquid levels in the first inter-stage separation tank 4, the second inter-stage separation tank 7, the dehydrogenation tower 1 and the dehydrogenation tower reflux tank 10 are maintained at 20%, thereby achieving efficient and high-purity separation and recovery of hydrogen, liquid ethylene and liquid 1-octene.

[0029] The following are the data on the material composition of polyethylene elastomer tail gas before it enters the device and the hydrogen, ethylene and 1-octene components separated when it leaves the device:

[0030] It can be seen from the above data that after the hydrogen in the polyethylene elastomer tail gas is separated separately, the concentration of hydrogen in the hydrogen accounts for ≥99 mol%, and only contains a small amount of ethylene and 1-octene, and the hydrogen recovery efficiency is high; after the ethylene in the polyethylene elastomer tail gas is separated separately, the concentration of ethylene accounts for ≥99 mol%, and only contains a small amount of hydrogen and 1-octene, and the ethylene recovery efficiency is high; after the 1-octene in the polyethylene elastomer tail gas is separated separately, the concentration of 1-octene accounts for ≥94 mol%, and the 1-octene recovery efficiency is high; in summary, the present invention has not only high recovery efficiency but also high recovery purity for hydrogen, ethylene and 1-octene in the polyethylene elastomer tail gas.

[0031] The present invention is simple to operate, convenient to use, and suitable for comprehensive promotion and application. Although the embodiments of the present invention have been shown and described, it is understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polyethylene elastomer process tail gas treatment device, comprising a dehydrogenation tower (1), characterized in that: It also includes a first-stage compressor (2), a first-stage separator tank feed heat exchanger (3), a first-stage separator tank (4), a second-stage compressor (5), a second-stage separator tank feed heat exchanger (6), a second-stage separator tank (7), a dehydrogenation tower feed cooler (8), a dehydrogenation tower top cooler (9), a dehydrogenation tower reflux tank (10), and a third-stage compressor (11); The air inlet of the first-stage compressor (2) is connected to a pipeline, the air outlet of the first-stage compressor (2) and the air inlet of the first-stage separation tank feed heat exchanger (3) are connected through the pipeline, the air outlet of the first-stage separation tank feed heat exchanger (3) and the air inlet of the first-stage separation tank (4) are connected through the pipeline, and the first-stage separation tank (4) is provided with a first control circuit for controlling the liquid level in the first-stage separation tank (4); The air outlet of the first inter-stage separation tank (4) is connected to the air inlet of the second-stage compressor (5) through a pipeline, the air outlet of the second-stage compressor (5) is connected to the air inlet of the feed heat exchanger (6) of the second inter-stage separation tank through a pipeline, the air outlet of the feed heat exchanger (6) of the second inter-stage separation tank is connected to the air inlet of the second inter-stage separation tank (7) through a pipeline, and the second inter-stage separation tank (7) is provided with a second control circuit for controlling the liquid level in the second inter-stage separation tank (7), and the second control circuit is connected to the first control circuit; The gas outlet of the second interstage separation tank (7) is connected to the gas inlet of the dehydrogenation tower feed cooler (8) through a pipeline, and an online monitoring instrument a (12) is provided on the pipeline. The gas outlet of the dehydrogenation tower feed cooler (8) is connected to the gas inlet of the dehydrogenation tower (1) through a pipeline. The dehydrogenation tower (1) is provided with a third control loop for controlling the liquid level in the dehydrogenation tower (1).

2. The polyethylene elastomer process tail gas treatment device according to claim 1, characterized in that: The gas outlet of the dehydrogenation tower (1) is connected to the gas inlet of the dehydrogenation tower top cooler (9) through a pipeline, and an online monitoring instrument b (13) is arranged on the pipeline. The gas outlet of the dehydrogenation tower top cooler (9) is connected to the gas inlet of the dehydrogenation tower reflux tank (10) through a pipeline. The gas outlet of the dehydrogenation tower reflux tank (10) is connected to the gas inlet of the third-stage compressor (11) through a pipeline, and an online monitoring instrument c (14) is arranged on the pipeline. The gas outlet of the third-stage compressor (11) is connected to a pipeline, and a regulating valve g (31) is arranged on the pipeline. A branch pipeline is arranged on the pipeline where the regulating valve g (31) is located. The branch pipeline is connected to the pipeline connected to the gas inlet of the first-stage compressor (2), and a regulating valve h (32) is arranged on the pipeline. A fourth control loop is arranged on the dehydrogenation tower reflux tank (10), and the fourth control loop is connected to the dehydrogenation tower (1).

3. The polyethylene elastomer process tail gas treatment device according to claim 2, characterized in that: The first control loop comprises a pipeline connected to the discharge port of the first inter-stage separation tank (4), on which a first inter-stage separation tank bottom delivery pump (15), a regulating valve a (16) and an online monitoring instrument d (17) are arranged; a branch pipeline connected to the first intermittent separation tank (4) is arranged on the pipeline where the regulating valve a (16) is located, and a regulating valve b (18) is arranged on the branch pipeline; a calculation controller a (19) is commonly arranged on the circuit lines on the regulating valves a (16) and the regulating valves b (18); a liquid level gauge a (20) is connected to the circuit line on the calculation controller a (19), and the liquid level gauge a (20) is connected to the first inter-stage separation tank (4).

4. The polyethylene elastomer process tail gas treatment device according to claim 3, characterized in that: The second control loop comprises a pipeline connected between the discharge port of the second inter-stage separation tank (7) and the pipeline where the regulating valve a (16) is located, and a regulating valve c (21) is arranged on the pipeline, and the circuit line on the regulating valve c (21) is connected to a liquid level meter b (22), and the liquid level meter b (22) is connected to the second inter-stage separation tank (7).

5. A polyethylene elastomer process tail gas treatment device according to claim 4, characterized in that: The third control loop comprises a pipeline connected to the discharge port of the dehydrogenation tower (1), and an online monitoring instrument e (23) and a regulating valve d (24) are arranged on the pipeline. The circuit line on the regulating valve d (24) is connected to a liquid level meter c (25), and the liquid level meter c (25) is connected to the dehydrogenation tower (1).

6. A polyethylene elastomer process tail gas treatment device according to claim 5, characterized in that: The fourth control loop comprises a pipeline connected to the discharge port of the dehydrogenation tower reflux tank (10) and the dehydrogenation tower (1), and the pipeline is connected to a dehydrogenation tower top reflux pump (26) and a regulating valve e (27), the circuit line of the regulating valve e (27) is connected to a calculation controller b (28), the circuit line of the calculation controller b (28) is connected to a liquid level meter d (29), the liquid level meter d (29) is connected to the dehydrogenation tower reflux tank (10), and also comprises a branch pipeline connected to the pipeline where the regulating valve e (27) is located, and the branch pipeline is connected to the dehydrogenation tower reflux tank (10), the branch pipeline is provided with a regulating valve f (30), and the circuit line on the regulating valve f (30) is connected to the calculation controller b (28).

7. A polyethylene elastomer tail gas treatment process, which uses a polyethylene elastomer process tail gas treatment device according to any one of claims 2-6, characterized in that: The treatment process includes the following steps: Step 1: Adjust the first control loop so that the liquid level in the first inter-stage separation tank (4) reaches 20%; Step 2: Adjust the second control loop so that the liquid level in the second inter-stage separation tank (7) reaches 20%; Step 3: Adjust the third control loop so that the liquid level of the dehydrogenation tower (1) reaches 20%; Step 4: Adjust the fourth control loop so that the liquid level of the dehydrogenation tower reflux tank (10) reaches 20%; Step 5: The tail gas enters the first compressor (2) and is compressed before accelerating into the first inter-stage separation tank feed heat exchanger (3) for heat exchange, so that the tail gas is cooled. The cooled tail gas enters the first inter-stage separation tank (4), and the super-heavy component 1-octene in the tail gas is converted into a liquid phase and remains in the first inter-stage separation tank (4). The 1-octene is discharged when the liquid level in the first inter-stage separation tank (4) is maintained at 20%. The tail gas in the first inter-stage separation tank (4) enters the second compressor (5) and is compressed before accelerating into the second inter-stage separation tank feed heat exchanger (6) for heat exchange, so that the tail gas is further cooled. The tail gas then enters the second inter-stage separation tank (7), and the remaining 1-octene in the tail gas is converted into a liquid phase and remains in the second inter-stage separation tank (7). The tail gas is discharged when the liquid level in the second inter-stage separation tank (7) is maintained at 20%. The tail gas in the second inter-stage separation tank ( The tail gas in the dehydrogenation tower (7) enters the dehydrogenation tower feed cooler (8) for deep cooling, and then enters the dehydrogenation tower (1). Only gaseous hydrogen and liquid ethylene remain in the tail gas. After adjustment by the third control loop, the liquid ethylene in the dehydrogenation tower (1) is discharged while maintaining the liquid level at 20%. The hydrogen in the dehydrogenation tower (1) is further cooled by the dehydrogenation tower top cooler (9) and then enters the dehydrogenation tower reflux tank (10). The liquid ethylene remaining in the hydrogen remains in the dehydrogenation tower reflux tank (10). Under the adjustment of the fourth control loop, the liquid level in the dehydrogenation tower reflux tank (10) is maintained at 20%, and the ethylene in the dehydrogenation tower reflux tank (10) refluxes into the dehydrogenation tower (1). The hydrogen in the dehydrogenation tower reflux tank (10) is discharged through the gas outlet of the dehydrogenation tower reflux tank (10). Through the above steps, the efficient and high-purity separation and recovery of hydrogen, ethylene and 1-octene in the tail gas is completed.

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