A polyethylene elastomer process tail gas treatment device and process

Abstract

The present invention discloses a polyethylene elastomer process tail gas treatment device and process, belonging to the technical field of tail gas treatment devices. It includes a dehydrogenation tower, and also includes a first-stage compressor, a first-stage inter-separation tank feed heat exchanger, a first-stage inter-separation tank, a second-stage compressor, a second-stage inter-separation tank feed heat exchanger, a second-stage inter-separation tank, a dehydrogenation tower feed cooler, a dehydrogenation tower top cooler, a dehydrogenation tower reflux tank, and a third-stage compressor. The outlet of the dehydrogenation tower top cooler is connected to the inlet of the dehydrogenation tower reflux tank through a pipeline, and the outlet of the dehydrogenation tower reflux tank is connected to the inlet of the third-stage compressor through a pipeline, and an on-line monitoring instrument c is arranged on the pipeline. The outlet of the third-stage compressor is connected with a pipeline and a regulating valve g is arranged on the pipeline. A fourth control loop is arranged on the dehydrogenation tower reflux tank, and the fourth control loop is connected to the dehydrogenation tower. The present invention has high integration, strong pertinence to the separation of hydrogen, ethylene, and 1-octene, no pollution in the process, and high recovery efficiency.

Description

Technical Field

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

[0002] Due to its high molecular weight and long-chain structure, polyolefin elastomer exhibits excellent elastic properties, chemical resistance, and heat resistance. Moreover, its processing performance and compatibility are good. Since its discovery, it has been highly favored by the market and has always been regarded as a "high-end polyolefin material". With the increase in people's disposable income in China, the demand for improving the quality of life is increasing day by day. The multi-scene, environmental protection attributes, and weather resistance of polyolefin elastomers are widely used by manufacturing enterprises such as various household appliances, automobiles, and footwear, effectively improving the quality of products that people directly contact.

[0003] Our company has successively completed the development of polyolefin elastomer catalysts, as well as small-scale and pilot-scale experiments. We are getting closer and closer to the continuous production of polyolefin elastomers with independent and controllable technology. However, we also found some problems during the experimental process. For example, an inevitable tail gas is generated during the production of polyolefin. 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 ultra-heavy component. It only changes slightly when switching product grades. This tail gas is characterized by a high hydrogen content and a high content of high-value polymer monomers. If this tail gas can be effectively recovered, the unit consumption of polyolefin elastomers in our company will be effectively reduced, further enhancing the competitiveness of our company's products.

[0004] Patent 201210438912.8 discloses an improved process for recovering non-methane hydrocarbons from polyolefin tail gas by adsorption. In this process, each adsorption tower cyclically experiences steps of low-pressure adsorption, equal pressure increase, pressure increase, high-pressure adsorption, equal pressure decrease, displacement, reverse release, evacuation, and pressure increase in sequence, or each adsorption tower cyclically experiences steps of low-pressure adsorption, pressure increase, high-pressure adsorption, equal pressure decrease, displacement, reverse release, evacuation, and equal pressure increase in sequence.

[0005] Patent 202010681396.6 discloses a device and method for separating and recovering tail gas components of a polyolefin device. The device includes: a pretreatment mechanism, which is used to receive raw gas and purge gas, mix and compress the gas to remove impurities such as heavy hydrocarbons, and then transport it 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 swing 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. The desorption unit is used to receive the purge gas from the pretreatment mechanism, desorb the adsorbate, and then return it to the pretreatment mechanism to increase the hydrocarbon concentration entering the cryogenic mechanism.

[0006] Patent 202121647675.7 discloses a tail gas membrane recovery system for a polyolefin plant, including a tank body. The center of the bottom wall of the tank body is fixedly connected with a drain pipe. A plurality of groups of separation plates are uniformly fixedly connected to the bottom of the fixed seat. A plurality of groups of separation membranes are arranged inside all the separation plates. A plurality of groups of liquid guide grooves arranged front and back are arranged on the left of all the separation plates. First, a plurality of groups of steam pipes arranged evenly up and down are installed inside the recovery tank body. The two adjacent steam pipes up and down are connected by an installed U-shaped steam guide pipe, so that the tail gas can flow through the plurality of groups of steam pipes arranged up and down. A plurality of groups of separation plates are installed inside all the steam pipes. The tail gas enters the uppermost steam pipe and is first separated by the separation membrane on the separation plate. The remaining tail gas is ignited to further reduce the harmful environmental components contained therein. The burned gas is then discharged purely through the exhaust net.

[0007] Patent 201610721758.3 discloses a method for recovering polyolefin tail gas hydrocarbons by full-temperature adsorption extraction, including a hydrocarbon adsorption concentration process, a hydrocarbon extraction and desorption process, a hydrocarbon separation and recovery process, and a PSA separation and purification of nitrogen process. The polyolefin tail gas first passes through the hydrocarbon adsorption concentration process. Most of the C2+ hydrocarbon components are adsorbed in the adsorption tower. The 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 by-product 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, the hydrocarbon extraction and desorption process is carried out to dissolve the effective component - C2+ hydrocarbon components. The extraction and desorbed gas enters the hydrocarbon separation and recovery process, where it is depressurized or condensed and cooled. The non-condensable gas N2 escapes and is mixed with the nitrogen-rich gas and enters the PSA separation and purification of N2 process. Subsequently, the extractant escapes and is recycled after regeneration and recovery processing.

[0008] The above prior arts 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 and high investment due to the large number of control valve groups, adsorbents, etc. For membrane recovery, no relatively mature ethylene separation membrane has been seen. The extraction technology brings new impurities, increasing the removal of impurities and at the same time bringing the possibility of potential product pollution. Even more, some technical routes adopt the form of direct co-combustion and then direct discharge into the atmosphere, bringing huge waste and increasing the carbon dioxide emissions. Summary of the Invention

[0009] In order to solve the technical problems mentioned in the above background art, the present invention provides a tail gas treatment device for a polyethylene elastomer process, and the technical scheme adopted is as follows:

[0010] It includes a dehydrogenation tower, and also includes a first-stage compressor, a first-stage inter-stage separation tank feed heat exchanger, a first-stage inter-stage separation tank, a second-stage compressor, a second-stage inter-stage separation tank feed heat exchanger, a second-stage inter-stage separation tank, a dehydrogenation tower feed cooler, a dehydrogenation tower top cooler, a dehydrogenation tower reflux tank, and a third-stage compressor. The inlet of the first-stage compressor is connected to a pipeline. The outlet of the first-stage compressor and the inlet of the first-stage inter-stage separation tank feed heat exchanger are connected by a pipeline. The outlet of the first-stage inter-stage separation tank feed heat exchanger and the inlet of the first-stage inter-stage separation tank are connected by a pipeline. A first control loop is provided on the first-stage inter-stage separation tank. The outlet of the first-stage inter-stage separation tank is connected to the inlet of the second-stage compressor by a pipeline. The outlet of the second-stage compressor and the inlet of the second-stage inter-stage separation tank feed heat exchanger are connected by a pipeline. The outlet of the second-stage inter-stage separation tank feed heat exchanger and the inlet of the second-stage inter-stage separation tank are connected by a pipeline. A second control loop is provided on the second-stage inter-stage separation tank. The second control loop is connected to the first control loop. The outlet of the second-stage inter-stage separation tank is connected to the inlet of the dehydrogenation tower feed cooler by a pipeline, and an on-line monitoring instrument a is provided on the pipeline. The outlet of the dehydrogenation tower feed cooler is connected to the inlet of the dehydrogenation tower by a pipeline. A third control loop is provided on the dehydrogenation tower. The outlet of the dehydrogenation tower is connected to the inlet of the dehydrogenation tower top cooler by a pipeline, and an on-line monitoring instrument b is provided on the pipeline. The outlet of the dehydrogenation tower top cooler is connected to the inlet of the dehydrogenation tower reflux tank by a pipeline. The outlet of the dehydrogenation tower reflux tank is connected to the inlet of the third-stage compressor by a pipeline, and an on-line monitoring instrument c is provided on the pipeline. The outlet of the third-stage compressor is connected to a pipeline, and a regulating valve g is provided on the pipeline. A fourth control loop is provided on the dehydrogenation tower reflux tank. The fourth control loop is connected to the dehydrogenation tower.

[0011] Further, the first control loop includes a pipeline connected to the outlet of the first-stage inter-stage separation tank, and a first-stage inter-stage separation tank bottom transfer pump, a regulating valve a, and an on-line monitoring instrument d are provided on the pipeline. A branch pipeline connected to the first-stage intermittent separation tank is provided on the pipeline where the regulating valve a is located, and a regulating valve b is provided on the branch pipeline. A calculation controller a is jointly provided on the circuit lines of the regulating valve a and the regulating valve b. A level gauge a is connected to the circuit line of the calculation controller a. The level gauge a is connected to the first-stage inter-stage separation tank.

[0012] Further, the second control loop includes a pipeline connected between the outlet of the second-stage inter-stage separation tank and the pipeline where the regulating valve a is located, and a regulating valve c is provided on the pipeline. A level gauge b is connected to the circuit line of the regulating valve c. The level gauge b is connected to the second-stage inter-stage separation tank.

[0013] Further, the third control loop includes a pipeline connected to the outlet of the dehydrogenation tower, and an on-line monitoring instrument e and a regulating valve d are provided on the pipeline. A level gauge c is connected to the circuit line of the regulating valve d. The level gauge c is connected to the dehydrogenation tower.

[0014] Further, the fourth control loop includes a pipeline connecting the outlet of the dehydrogenation tower reflux drum and the dehydrogenation tower, and a dehydrogenation tower top reflux pump and a regulating valve e are connected to the pipeline. A calculation controller b is connected to the circuit line of the regulating valve e, a liquid level gauge d is connected to the circuit line of the calculation controller b, the liquid level gauge d is connected to the dehydrogenation tower reflux drum, and a branch pipeline is further included which is connected to the pipeline where the regulating valve e is located and the branch pipeline is connected to the dehydrogenation tower reflux drum. A regulating valve f is provided on the branch pipeline and the circuit line on the regulating valve f is connected to the calculation controller b.

[0015] The processing process includes the following steps:

[0016] Step 1: Adjust the first control loop to make the liquid level in the first inter-stage separation tank reach 20%.

[0017] Step 2: Adjust the second control loop to make the liquid level in the second inter-stage separation tank reach 20%.

[0018] Step 3: Adjust the third control loop to make the liquid level in the dehydrogenation tower reach 20%.

[0019] Step 4: Adjust the fourth control loop to make the liquid level in the dehydrogenation tower reflux drum reach 20%.

[0020] Step 5: The tail gas enters the first-stage compressor, is compressed and then accelerated into the first inter-stage separation tank feed heat exchanger for heat exchange, so that the tail gas is cooled. The cooled tail gas enters the first inter-stage separation tank. The ultra-heavy component 1-octene in the tail gas becomes liquid and remains in the first inter-stage separation tank. 1-octene is discharged under the condition that the liquid level in the first inter-stage separation tank remains 20%. The tail gas in the first inter-stage separation tank enters the second-stage compressor, is compressed and then accelerated into the second inter-stage separation tank feed heat exchanger for heat exchange, so that the tail gas is further cooled, and then enters the second inter-stage separation tank. The remaining 1-octene in the tail gas becomes liquid and remains in the second inter-stage separation tank. It is merged into the first control loop and discharged under the condition that the liquid level in the second inter-stage separation tank remains 20%. The tail gas in the second inter-stage separation tank enters the dehydrogenation tower feed cooler for deep cooling and then enters the dehydrogenation tower. Only gaseous hydrogen and liquid ethylene remain in the tail gas. Through the regulation of the third control loop, the liquid ethylene in the dehydrogenation tower is discharged under the condition that the liquid level remains 20%. The hydrogen in the dehydrogenation tower is further cooled by the dehydrogenation tower top cooler and then enters the dehydrogenation tower reflux drum. The remaining liquid ethylene in the hydrogen remains in the dehydrogenation tower reflux drum. Under the regulation of the fourth control loop, under the condition that the liquid level in the dehydrogenation tower reflux drum remains 20%, the ethylene in the dehydrogenation tower reflux drum returns to the dehydrogenation tower, and the hydrogen in the dehydrogenation tower reflux drum is discharged through the dehydrogenation tower reflux drum gas outlet. Through the above steps, the efficient and high-purity separation and recovery of hydrogen, ethylene and 1-octene in the tail gas are completed.

[0021] The present invention has the following advantages: By manually adjusting the first control loop and the fourth control loop first, the liquid levels in the first inter-stage separation tank and the dehydrogenation tower reflux tank reach 30% respectively, so that a liquid seal layer is formed in each of the first inter-stage separation tank and the dehydrogenation tower reflux tank. Then, through the manual adjustment of the first control loop and the fourth control loop respectively, the liquid levels in the first inter-stage separation tank and the dehydrogenation tower reflux tank gradually drop to 20% respectively. 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%, realizing the high-purity separation and recovery of hydrogen, ethylene, and 1-octene in the tail gas. The present invention has high integration, strong pertinence to the separation of hydrogen, ethylene, and 1-octene, no pollution in the process, and high recovery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic flow diagram of the present invention.

[0023] DRAWINGS: 1 dehydrogenation tower, 2 first-stage compressor, 3 first inter-stage separation tank feed heat exchanger, 4 first inter-stage separation tank, 5 second-stage compressor, 6 second inter-stage separation tank feed heat exchanger, 7 second inter-stage separation tank, 8 dehydrogenation tower feed cooler, 9 dehydrogenation tower top cooler, 10 dehydrogenation tower reflux tank, 11 third-stage compressor, 12 on-line monitoring instrument a, 13 on-line monitoring instrument b, 14 on-line monitoring instrument c, 15 first inter-stage separation tank bottom transfer pump, 16 regulating valve a, 17 on-line 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 on-line 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 OF THE EMBODIMENTS

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] Please refer to Figure 1 , a polyethylene elastomer process tail gas treatment device, including a dehydrogenation tower 1, and also including a first-stage compressor 2, a first inter-stage separation tank feed heat exchanger 3, a first inter-stage separation tank 4, a second-stage compressor 5, a second inter-stage separation tank feed heat exchanger 6, a second inter-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.

[0026] The intake port of the first-stage compressor 2 is connected to a pipeline. The tail gas from the polyolefin elastomer enters the first-stage compressor 2 through the pipeline. The outlet port of the first-stage compressor 2 and the intake port of the first-stage inter-stage separation tank feed heat exchanger 3 are connected through a pipeline. The first-stage compressor 2 compresses the tail gas and then accelerates it through the pipeline into the first-stage inter-stage separation tank feed heat exchanger 3, so that the tail gas is cooled. The outlet port of the first-stage inter-stage separation tank feed heat exchanger 3 and the intake port of the first-stage inter-stage separation tank 4 are connected through a pipeline. Due to the cooling of the tail gas, the overweight component 1-octene in the tail gas becomes a liquid phase and remains in the first-stage inter-stage separation tank 4. A first control loop is provided on the first-stage inter-stage separation tank 4 to control the liquid level height in the separation tank 4.

[0027] The outlet port of the first-stage inter-stage separation tank 4 is connected to the intake port of the second-stage compressor 5 through a pipeline. After 1-octene is separated in the first-stage inter-stage separation tank 4, the remaining tail gas composed of hydrogen and ethylene enters the second-stage compressor 5 through the pipeline. The outlet port of the second-stage compressor 5 and the intake port of the second-stage inter-stage separation tank feed heat exchanger 6 are connected through a pipeline. The tail gas in the second-stage compressor 5 is compressed and accelerated into the second-stage inter-stage separation tank feed heat exchanger 6, so that the tail gas continues to be cooled. The outlet port of the second-stage inter-stage separation tank feed heat exchanger 6 and the intake port of the second-stage inter-stage separation tank 7 are connected through a pipeline. The tail gas in the second-stage inter-stage separation tank feed heat exchanger 6 enters the second-stage inter-stage separation tank 7. The remaining 1-octene in the tail gas continues to fall in the second-stage inter-stage separation tank 7 in a liquid phase. A second control loop is provided on the second-stage inter-stage separation tank 7 to control the liquid level height in the second-stage inter-stage separation tank 7. The second control loop is connected to the first control loop. The first control loop and the second control loop jointly control the discharge of 1-octene.

[0028] The outlet port of the second-stage inter-stage separation tank 7 is connected to the intake port of the dehydrogenation tower feed cooler 8 through a pipeline, and an on-line monitoring instrument a12 is provided on the pipeline. The on-line monitoring instrument a12 monitors the dew point condition in the pipeline where it is located to prevent freezing and blockage in the pipeline. The tail gas enters the dehydrogenation tower feed cooler 8 through the pipeline for cryogenic cooling. The outlet port of the dehydrogenation tower feed cooler 8 is connected to the intake port of the dehydrogenation tower 1 through a pipeline. The cryogenically cooled tail gas enters the dehydrogenation tower 1 through the pipeline. The ethylene in the cryogenically cooled tail gas becomes a liquid phase and falls in the dehydrogenation tower 1. A third control loop is provided on the dehydrogenation tower 1 to control the liquid level height in the dehydrogenation tower 1 and the discharge of ethylene.

[0029] The outlet of the dehydrogenation tower 1 is connected to the inlet of the overhead cooler 9 of the dehydrogenation tower through a pipeline, and an on-line monitoring instrument b13 is arranged on the pipeline. The on-line 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 overhead cooler 9 of the dehydrogenation tower through a pipeline for cooling. The outlet of the overhead cooler 9 of the dehydrogenation tower is connected to the inlet of the reflux drum 10 of the dehydrogenation tower through a pipeline. The cooled tail gas enters the reflux drum 10 of the dehydrogenation tower through the overhead cooler 9 of the dehydrogenation tower. The remaining ethylene in the tail gas continues to become liquid and falls in the reflux drum 10 of the dehydrogenation tower. The outlet of the reflux drum 10 of the dehydrogenation tower is connected to the inlet of the third-stage compressor 11 through a pipeline, and an on-line monitoring instrument c14 is arranged on the pipeline. The on-line monitoring instrument c14 monitors the purity of hydrogen in the pipeline where it is located. The hydrogen discharged from the outlet of the reflux drum 10 of the dehydrogenation tower enters the third-stage compressor 11 through a pipeline. The outlet of the third-stage compressor 11 is connected with a pipeline, and a regulating valve g31 is arranged on the pipeline to control the switch of the pipeline where it is located. When the regulating valve g31 is opened, the hydrogen in the pipeline is discharged. A branch pipeline is arranged on the pipeline where the regulating valve g31 is located. This branch pipeline is connected to the pipeline connected to the inlet of the first-stage compressor 2, and a regulating valve h32 is arranged on the pipeline. If the on-line monitoring instrument c14 monitors that the purity of hydrogen in the pipeline where it is located is impure, the regulating valve g31 is closed and the regulating valve h32 is opened, and the hydrogen returns to the first-stage compressor 2 through the changed pipeline. A fourth control loop is arranged on the reflux drum 10 of the dehydrogenation tower. The fourth control loop is connected to the dehydrogenation tower 1, and the fourth control loop controls the liquid level height in the reflux drum 10 of the dehydrogenation tower.

[0030] The first control loop includes a pipeline connected to the outlet of the first-stage intermediate separation tank 4, and a first-stage intermediate separation tank bottom transfer pump 15, a regulating valve a16 and an on-line monitoring instrument d17 are arranged on the pipeline. The on-line monitoring instrument d17 monitors the purity of 1-octene in the pipeline where it is located. A branch pipeline connected to the first intermittent separation tank 4 is arranged on the pipeline where the regulating valve a16 is located, and a regulating valve b18 is arranged on the branch pipeline. Both the regulating valve a16 and the regulating valve b18 can be manual or electric. A calculation controller a19 is jointly arranged on the circuit lines of the regulating valve a16 and the regulating valve b18. The calculation controller a19 controls the opening degrees of the regulating valve a16 and the regulating valve b18. A liquid level gauge a20 is connected to the circuit line of the calculation controller a19. The signal of the liquid level gauge a20 is fed back to the calculation controller a19, and the liquid level gauge a20 is connected to the first-stage intermediate separation tank 4.

[0031] The second control loop includes a pipeline connected between the outlet of the second-stage intermediate separation tank 7 and the pipeline where the regulating valve a16 is located, and a regulating valve c21 is arranged on the pipeline. A liquid level gauge b22 is connected to the circuit line of the regulating valve c21. The liquid level gauge b22 feeds back a signal to the regulating valve c21. The liquid level gauge b22 is connected to the second-stage intermediate separation tank 7, and the liquid level gauge b22 monitors the liquid level height in the second-stage intermediate separation tank 7.

[0032] The third control loop includes a pipeline connected to the outlet of the dehydrogenation tower 1, and an on-line monitoring instrument e23 and a regulating valve d24 are arranged on the pipeline. The on-line monitoring instrument e23 monitors the purity of ethylene in the pipeline where it is located. The circuit line of the regulating valve d24 is connected to a liquid level gauge c25. The liquid level gauge c25 is connected to the dehydrogenation tower 1. The liquid level gauge c25 feeds back a signal to the regulating valve d24, and the liquid level gauge c25 monitors the liquid level height in the dehydrogenation tower 1.

[0033] The fourth control loop includes a pipeline connected to the outlet of the dehydrogenation tower reflux drum 10 and the dehydrogenation tower 1, and a dehydrogenation tower top reflux pump 26 and a regulating valve e27 are connected to the pipeline. The circuit line of the regulating valve e27 is connected to a calculation controller b28. The circuit line of the calculation controller b28 is connected to a liquid level gauge d29. The liquid level gauge d29 monitors the liquid level height in the dehydrogenation tower reflux drum 10. The liquid level gauge d29 is connected to the dehydrogenation tower reflux drum 10. It 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 drum 10. A regulating valve f30 is arranged on the branch pipeline, and the circuit line of the regulating valve f30 is connected to the calculation controller b28. The liquid level gauge d29 feeds back a signal to the calculation controller b28. The calculation controller b28 controls the opening degrees of the regulating valve e27 and the regulating valve f30. Both the regulating valve e27 and the regulating valve f30 can be manual or electric.

[0034] The working principle of the present invention:

[0035] The process tail gas of the polyethylene elastomer enters the first-stage compressor 2 through a pipeline. After compression, it accelerates and enters the feed heat exchanger 3 of the first-stage inter-stage separation tank, where the tail gas is cooled. Then, the tail gas enters the first-stage inter-stage separation tank 4 through the pipeline of the feed heat exchanger 3 of the first-stage inter-stage separation tank. The 1-octene in the tail gas turns into a liquid phase and falls into the first-stage inter-stage separation tank 4. At this time, the worker manually closes the regulating valve a16, opens the regulating valve b18, and starts the bottom transfer pump 15 of the first-stage inter-stage separation tank. The 1-octene in the first-stage inter-stage separation tank 4 is pumped into the pipeline where the regulating valve b18 is located, so that the liquid-phase 1-octene drawn out of the first-stage inter-stage separation tank 4 returns to the first-stage inter-stage separation tank 4 until the liquid level in the first-stage inter-stage separation tank 4 is monitored by the liquid level gauge a20 and reaches 30%. The liquid level is maintained by the circulating reflux method in this process to increase the residence time of 1-octene in the first-stage inter-stage separation tank 4, avoid the tail gas flowing out of the first-stage inter-stage separation tank 4 too quickly, and reduce the amount of 1-octene in the tail gas remaining in the first-stage inter-stage separation tank 4. The first use of liquid level maintenance is also to form a liquid seal layer in the first-stage inter-stage separation tank 4. Otherwise, under the negative pressure condition pumped by the bottom transfer pump 15 of the first-stage inter-stage separation tank, the tail gas will also be pumped away. After the liquid level in the first-stage inter-stage separation tank 4 reaches 30%, the regulating valve a16 is opened, and the opening of the regulating valve b18 is adjusted smaller. The 1-octene in the first-stage inter-stage separation tank 4 is discharged through the discharge port at its bottom. To avoid the discharge flow rate being too fast and carrying out the tail gas, the opening of the regulating valve b18 is adjusted smaller, so that a part of 1-butene is directly discharged, and a small part returns to the first-stage inter-stage separation tank 4 until the liquid level gauge a20 monitors that the liquid level in the first-stage inter-stage separation tank 4 is 20%. Then, the calculation controller a19 adjusts the opening of the regulating valve a16 and the regulating valve b18, so that while 1-butene is discharged, the liquid level in the first-stage inter-stage separation tank 4 always remains at 20%;

[0036] The tail gas in the first-stage inter-stage separation tank 4 enters the second-stage compressor 5 through a pipeline. After compression, it accelerates and passes through the pipeline into the feed heat exchanger 6 of the second-stage inter-stage separation tank, so that the tail gas still remains cooled. Then, the tail gas in the feed heat exchanger 6 of the second-stage inter-stage separation tank enters the second-stage inter-stage separation tank 7. The residual liquid-phase 1-octene in the tail gas falls into the second-stage inter-stage separation tank 7. The liquid level gauge b22 monitors the liquid level in the second-stage inter-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 inter-stage separation tank 7 always at 20%, forming a liquid seal layer to prevent the tail gas from being discharged from the bottom of the second-stage inter-stage separation tank 7. The 1-octene in the second-stage inter-stage separation tank 7 is discharged together through the pipeline into the pipeline where the regulating valve a16 is located;

[0037] 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 becomes liquid phase and falls in the dehydrogenation tower 1. The liquid level gauge c25 monitors the liquid level in the dehydrogenation tower 1 and feeds back a signal to the regulating valve d24 to adjust the opening degree, so that the liquid level in the dehydrogenation tower 1 is always maintained at 20% and is 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;

[0038] The tail gas in the dehydrogenation tower 1 enters the dehydrogenation tower top cooler 9 through a pipeline and continues to be cooled, and then enters the dehydrogenation tower reflux drum 10 through a pipeline. The residual liquid-phase ethylene in the tail gas falls in the dehydrogenation tower reflux drum 10. At this time, manually adjust the regulating valve e27 to close and the regulating valve f30 to open. Under the extraction of the dehydrogenation tower top reflux pump 26, the ethylene in the dehydrogenation tower reflux drum 10 returns to the dehydrogenation tower reflux drum 10 through the pipeline where the regulating valve f is located until the liquid level gauge d29 monitors that the liquid level in the dehydrogenation tower top reflux drum 10 is 30%. Then open the regulating valve e27 and reduce the opening degree of the regulating valve f30. The liquid-phase ethylene in the dehydrogenation tower reflux drum 10 is discharged into the dehydrogenation tower 1 through the pipeline where the regulating valve e27 is located, and a small part returns to the dehydrogenation tower reflux drum 10 through the pipeline where the regulating valve f30 is located. Its purpose is the same as the adjustment when the first-stage separation tank is in use. The ethylene forms a liquid seal layer in the dehydrogenation tower reflux drum 10. When the liquid level gauge d29 monitors that the liquid level in the dehydrogenation tower reflux drum 10 reaches 20%, the calculation controller b28 controls the opening degrees of the regulating valve e27 and the regulating valve f30 to keep the liquid level in the dehydrogenation tower reflux drum 10 at 20% all the time. At this time, the component of the tail gas in the dehydrogenation tower reflux drum 10 is only hydrogen left. The hydrogen in the dehydrogenation tower reflux drum 10 enters the third-stage compressor 11 through a pipeline, and after being compressed and accelerated, it enters the pipeline where the regulating valve g31 is located and is discharged;

[0039] Through the initial manual adjustment of the first-stage separation tank 4 and the dehydrogenation tower reflux drum 10, and then the subsequent automatic adjustment of the first-stage separation tank 4, the second-stage separation tank 7, the dehydrogenation tower 1 and the dehydrogenation tower reflux drum 10, the liquid levels in the first-stage separation tank 4, the second-stage separation tank 7, the dehydrogenation tower 1 and the dehydrogenation tower reflux drum 10 are all maintained at 20%, realizing the efficient and high-purity separation and recovery of hydrogen, liquid-phase ethylene and liquid-phase 1-octene.

[0040] The following are the data of the material components of the polyethylene elastomer tail gas before entering this device and the separated hydrogen, ethylene and 1-octene components when leaving this device:

[0041]

[0042] As can be seen from the above data, after the hydrogen in the tail gas of the polyethylene elastomer is separated alone, the concentration ratio of hydrogen in the hydrogen is ≥99 mol%, and only a small amount of ethylene and 1-octene are contained, and the recovery efficiency of hydrogen is high; after the ethylene in the tail gas of the polyethylene elastomer is separated alone, the concentration ratio of ethylene is ≥99 mol%, and only a small amount of hydrogen and 1-octene are contained, and the recovery efficiency of ethylene is high; after the 1-octene in the tail gas of the polyethylene elastomer is separated alone, the concentration ratio of 1-octene is ≥94 mol%, and the recovery efficiency of 1-octene is high; in summary, the present invention has high recovery efficiency and high recovery purity for hydrogen, ethylene and 1-octene in the tail gas of the polyethylene elastomer.

[0043] The operation of the present invention is simple and convenient to use, and is suitable for comprehensive promotion and application. Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can 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 inter-stage 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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