阅读说明：本技术 一种乙烯的低温提纯装置 (Low-temperature purification device for ethylene ) 是由 郝雅博 秦燕 许路军 吴辉江 徐志明 吴杰 卫光普 于 2021-06-15 设计创作，主要内容包括：本发明公开了一种乙烯的低温提纯装置,主要处理来自以乙烯为原料的合成工艺或生产乙烯工艺过程中产生的尾气,如醋酸乙烯-乙烯共聚物制备过程中产生的脱泡气、乙烯生产过程中的尾气等,其工艺尾气中通常含有乙烯、醋酸乙烯或重组分、氮气、甲烷、乙烷、氧气、二氧化碳、水或甲醇等,通过该装置可以得到纯度达到99.5%(mole)以上的乙烯产品气,本发明装置采用了分子筛的吸附净化单元,集成板翅式换热器(6/40/41)、重组分分离罐、乙烯分离罐或乙烯提纯塔、乙烯储罐或液态冷剂虹吸罐的低温分离冷箱单元,冷剂压缩机单元及连接管道为一体的深冷分离冷箱单元,本发明具有能耗低、投资小、易于调节等特点,提高企业的整体经济效益。(The invention discloses a low-temperature purification device of ethylene, which mainly treats tail gas generated in a synthesis process or an ethylene production process by taking ethylene as a raw material, such as deaeration gas generated in a preparation process of vinyl acetate-ethylene copolymer, tail gas generated in an ethylene production process and the like, wherein the process tail gas usually contains ethylene, vinyl acetate or heavy components, nitrogen, methane, ethane, oxygen, carbon dioxide, water or methanol and the like, and ethylene product gas with the purity of more than 99.5% (mole) can be obtained by the device. The invention has the characteristics of low energy consumption, small investment, easy adjustment and the like, and improves the overall economic benefit of enterprises.)

1. The utility model provides a low temperature purification device of ethylene, it is adsorbed purification unit (I) by the molecular sieve, and low temperature separation cold box unit (II), cryogen make-up system triplex are passed through the pipe connection between, its characterized in that: the molecular sieve adsorption purification unit (I) is internally provided with a feed gas precooling heat exchanger (1), a water separation tank (2), a first molecular sieve adsorber (3) and a second molecular sieve adsorber (4) respectively, wherein one end of the feed gas precooling heat exchanger (1) is connected with external raw material gas through a pipeline, the other end of the feed gas precooling heat exchanger is connected to the water separation tank (2) through a pipeline, the top of the water separation tank (2) is provided with a gas pipeline which is connected to the first molecular sieve adsorber (3) and the second molecular sieve adsorber (4) respectively, the bottom of the water separation tank is provided with a sewage pipeline (13) which is connected to a sewage outlet system, the bottoms of the first molecular sieve adsorber (3) and the second molecular sieve adsorber (4) are connected to an electric heater or a steam heater (5) through a pipeline (16), so that high-temperature regeneration gas can be sent to the first molecular sieve adsorber (3) or the second molecular sieve adsorber (4), and (3) regenerating the molecular sieve, connecting the first molecular sieve adsorber (3) and the second molecular sieve adsorber (4) with the low-temperature separation cold box unit (II) through pipelines, and feeding the purified gas into the low-temperature separation cold box (II).

2. The apparatus for the cryogenic purification of ethylene according to claim 1, characterized in that: the low-temperature separation cold box (II) is composed of a main plate fin type heat exchanger (6) internally provided with a plurality of flow channels, a heavy component separation tank (7), an ethylene separation tank (8) or an ethylene purification tower (39), a refrigerant supplement system, a plurality of connecting pipelines and a plurality of throttle valves.

3. The apparatus for the cryogenic purification of ethylene according to claim 2, characterized in that: the pipeline is communicated with a flow channel A (6a) of the main plate fin type heat exchanger (6), and is communicated with a middle feed inlet of the heavy component separation tank (7) through the pipeline after being cooled in a flow channel E (6E), heavy components in the process gas are condensed in the heavy component separation tank (7), and then are discharged out of the cold box through the pipeline, so that the heavy components with high freezing points are prevented from freezing equipment and pipelines at a low-temperature part; the gas separated from the top of the heavy component separation tank (7) passes through a pipeline, is cooled in a flow passage B (6B) and then is communicated with an ethylene separation tank (8) or an ethylene purification tower (39) through a pipeline, a throttle valve (V12) and a pipeline, the light component gas in the ethylene separation tank (8) or the ethylene purification tower (39) is separated, the top of the ethylene separation tank (8) or the ethylene purification tower (39) is connected with the lower end of a flow passage C (6C) of the main plate fin type heat exchanger (6) through a pipeline, and the upper end of the ethylene separation tank (8) or the ethylene purification tower (39) is connected with a non-condensable gas collecting device through a pipeline; liquid at the bottom of the ethylene separation tank (8) or the ethylene purification tower (39) is communicated with the lower end of a flow channel D (6D) of the main plate fin heat exchanger (6) through a pipeline, a liquid level control valve (V13) and the pipeline, the liquid is reheated through the flow channel D (6D) of the heat exchanger and then is connected with an ethylene product gas collection device through the pipeline, high-purity ethylene product gas is obtained, and one side of the middle part of the ethylene separation tank (8) or the ethylene purification tower (39) is also connected with a refrigerant supplement system.

4. The apparatus for the cryogenic purification of ethylene according to claim 3, characterized in that: the refrigerant supplementing system is an ethylene storage tank (9) connected with liquid refrigerants on the outer side through a pipeline, wherein liquid at the bottom of the ethylene storage tank is communicated with a middle feed inlet of the ethylene separation tank (8) through the pipeline, a valve (V14) and the pipeline, and is mixed with process gas phase to supplement cold for the system; and the top of the ethylene storage tank (9) is connected with a torch collecting device through a pipeline, so that the higher pressure of the device is maintained, and the overhigh pressure of the ethylene storage tank (9) is avoided.

5. The apparatus for the cryogenic purification of ethylene according to claim 3, characterized in that: the cold-agent supplementing system is a liquid siphon tank (31) connected with external liquid cold agent through a pipeline and a valve (V15), the liquid siphon tank (31) is communicated with the lower end and the middle end of a flow channel E (6E) of the main plate fin type heat exchanger (6) through the pipeline, the upper end of the flow channel E (6E) is communicated with the low-pressure gas collecting device through the pipeline, liquid evaporation in the main plate fin type heat exchanger (6) causes upper and lower density difference to realize liquid evaporation, and therefore continuous and stable cold energy is provided for the ethylene separation system.

6. The apparatus for the cryogenic purification of ethylene according to claim 5, characterized in that: still be equipped with runner F (6F) in mainboard finned heat exchanger (6), the lower extreme of this runner F (6F) is connected with heavy ends knockout drum (7) through pipeline, choke valve (V16), is connected with the heavy ends collection device in the outside through the pipeline in the upper end of runner F (6F), and this device can be through the evaporation cold volume of retrieving the heavy ends waste liquid to the feed gas that the heavy ends content is high to the cold volume of system is supplyed has been saved.

7. The apparatus for the cryogenic purification of ethylene according to claim 6, characterized in that: the upper portion of the main plate fin type heat exchanger (6) is also provided with a refrigerant compressor unit (III), one side of the bottom of the main plate fin type heat exchanger (6) which is positioned at the ethylene purification tower (39) is provided with a tower bottom reboiler (40), the tower bottom reboiler (40) is communicated with a flow channel A (6a) of the main plate fin type heat exchanger (6) through a pipeline, heat can flow into the flow channel A (6a) of the main plate fin type heat exchanger (6) through the pipeline, the other side of the tower bottom reboiler is provided with a pipeline, cold can be returned to the flow channel A (6a) again, the top of the ethylene purification tower (39) is provided with a tower top condenser (41), and the cold is communicated with a refrigerant circulating system through the pipeline.

8. The apparatus for the cryogenic purification of ethylene according to claim 7, characterized in that: the high-pressure gas of the refrigerant compressor unit (III) is communicated with the upper end of a flow channel H (6H) of the main plate fin type heat exchanger (6) through a pipeline, the high-pressure gas is divided into two parts through the pipeline after being cooled and condensed by the heat exchanger, one part is communicated with the refrigerant siphon tank (31) through a throttle valve (V15) and the pipeline, and the upper end of the flow channel E (6E) is connected with the low-pressure end of the refrigerant compressor unit (III) through the pipeline; the other strand is communicated with a tower top condenser (41) through a pipeline and a throttle valve (V17), is communicated with the lower end of a flow passage G (6G) of the main plate fin type heat exchanger (6) after reheating, is connected with the medium-pressure end of a refrigerant compressor unit (III) through the upper end of the reheating flow passage G (6G) through a pipeline, and forms closed circulation to the refrigerant circulation system.

Technical Field

The invention relates to a low-temperature ethylene purification device, and belongs to the field of low-temperature gas separation.

Background

In the existing factories, the treatment methods of tail gas generated in the synthesis process or the ethylene production process by taking ethylene as a raw material, such as deaeration gas generated in the preparation process of vinyl acetate-ethylene copolymer, tail gas generated in the ethylene production process and the like, are all torch-free incineration discharge, incomplete combustion of some components generates substances such as carbon monoxide, carbon black and the like which directly pollute the environment, and carbon dioxide gas can be generated after complete combustion, so that the greenhouse effect of the earth is intensified; in addition, the national emphasis on environmental resources advocates the realization of clean production in factories, the reduction of emission of greenhouse gases and the realization of the carbon neutralization goal. At the same time, these tail gases contain the effective component ethylene, and the discharge thereof directly results in a large economic loss. Therefore, the high-efficiency green ethylene purification device is adopted to recover ethylene components, realize the purification and recovery of ethylene, have important significance and greatly improve the economic benefit of factories.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, designs a low-temperature ethylene purification device, and adopts the following technical scheme for realizing the aim: a low-temperature ethylene purification device comprises a molecular sieve adsorption and purification unit, a low-temperature separation cold box unit and a refrigerant compressor unit which are connected through pipelines, wherein a feed gas precooling heat exchanger, a water separation tank and a molecular sieve adsorber are respectively arranged in the molecular sieve adsorption and purification unit, one end of the feed gas precooling heat exchanger is connected with external raw material gas through a pipeline, the other end of the feed gas precooling heat exchanger is connected to the water separation tank through a pipeline, the top of the water separation tank is provided with a gas pipeline which is respectively connected to a first molecular sieve adsorber and a second molecular sieve adsorber, the bottom of the water separation tank is provided with a sewage pipeline which is connected to a sewage outlet system, the bottoms of the first molecular sieve adsorber and the second molecular sieve adsorber are connected to an electric heater or a steam heater through pipelines, so that high-temperature regeneration gas can be sent to the first molecular sieve adsorber or the second molecular sieve adsorber, and regenerating the molecular sieve, wherein the first molecular sieve adsorber or the second molecular sieve adsorber is connected with the low-temperature separation cold box unit through a pipeline, and the purified gas enters the low-temperature separation cold box.

Preferably, the method comprises the following steps: the low-temperature separation cold box consists of a main plate fin type heat exchanger with a plurality of built-in runners, a heavy component separation tank, an ethylene separation tank or an ethylene purification tower, a refrigerant supplement system, a plurality of connecting pipelines and a plurality of throttle valves.

Preferably, the method comprises the following steps: the pipeline is communicated with the flow channel A of the main plate fin type heat exchanger, and is communicated with a middle feed inlet of the heavy component separation tank through the pipeline after being cooled in the flow channel E, heavy components in the process gas are condensed in the heavy component separation tank and then are discharged out of the cold box through the pipeline, and the heavy components with high freezing points are prevented from freezing equipment and pipelines at the low-temperature part; the gas separated from the top of the heavy component separation tank passes through a pipeline, is cooled in a flow passage B and then is communicated with an ethylene separation tank or an ethylene purification tower through the pipeline, a throttle valve and the pipeline, the light component gas in the ethylene separation tank or the ethylene purification tower is separated out, the top of the ethylene separation tank or the ethylene purification tower is connected with the lower end of a flow passage C of the main plate fin type heat exchanger through the pipeline, and the upper end of the ethylene separation tank or the ethylene purification tower is connected with a non-condensable gas collecting device through the pipeline; the liquid at the bottom of the ethylene separation tank or the ethylene purification tower is communicated with the lower end of a flow channel D of the main plate fin type heat exchanger through a pipeline and a liquid level control valve, the liquid is reheated by the flow channel D of the heat exchanger and then is connected with an ethylene product gas collecting device through a pipeline to obtain high-purity ethylene product gas, and one side of the middle part of the ethylene separation tank or the ethylene purification tower is also connected with a refrigerant supplementing system.

Preferably, the method comprises the following steps: the refrigerant supplementing system is an ethylene storage tank connected with liquid refrigerants on the outer side through a pipeline, wherein liquid at the bottom of the ethylene storage tank is communicated with a middle feeding hole of the ethylene separation tank through a pipeline and a valve, and is mixed with the process gas phase to supplement cold energy for the system; and the top of the ethylene storage tank is connected with a torch collecting device through a pipeline, so that the higher pressure of the device is maintained, and the overhigh pressure of the ethylene storage tank is avoided.

Preferably, the method comprises the following steps: the cold agent supplementing system is a liquid siphon tank connected with external liquid cold agent through a pipeline and a valve, the liquid siphon tank is communicated with the lower end and the middle end of a flow channel E of the main plate fin type heat exchanger through the pipeline, the upper end of the flow channel E is communicated with the low-pressure gas collecting device through the pipeline, liquid evaporation is realized due to the fact that liquid in the main plate fin type heat exchanger is evaporated and the upper and lower density difference is caused, and therefore continuous and stable cold energy is provided for the ethylene separation system.

Preferably, the method comprises the following steps: still be equipped with runner F in the mainboard finned heat exchanger, this runner F's lower extreme passes through pipeline, choke valve, pipeline and is connected with the heavy ends knockout drum, is connected with the heavy ends collection device in the outside through the pipeline at runner F's upper end, should put the raw gas that is high to the heavy ends content, can be through the evaporation cold volume of retrieving the heavy ends waste liquid to the cold volume of system is supplied has been saved.

Preferably, the method comprises the following steps: the main plate fin type heat exchanger is characterized in that a refrigerant compressor unit is further arranged above the main plate fin type heat exchanger, a tower bottom reboiler is arranged on one side, located at the bottom of the ethylene purification tower, of the bottom of the main plate fin type heat exchanger and communicated with a flow channel A of the main plate fin type heat exchanger through a pipeline, heat can flow into the flow channel A of the main plate fin type heat exchanger through the pipeline, a pipeline is arranged on the other side of the main plate fin type heat exchanger and can return cold energy to the flow channel A again, a tower top condenser is arranged at the top of the ethylene purification tower, and the cold energy of the ethylene purification tower is communicated with a refrigerant circulating system through the pipeline and the pipeline.

Preferably, the method comprises the following steps: the high-pressure gas of the refrigerant compressor unit is communicated with the upper end of a flow channel H of the main plate fin type heat exchanger through a pipeline, the high-pressure gas is cooled and condensed by the heat exchanger and then is divided into two parts through the pipeline, one part is communicated with the refrigerant siphon tank through a throttle valve and the pipeline, and the upper end of the flow channel E is connected with the low-pressure end of the refrigerant compressor unit through the pipeline; the other strand is communicated with a tower top condenser through a pipeline and a throttle valve, is communicated with the lower end of a flow channel G of the main plate fin type heat exchanger after reheating, is connected with the medium-pressure end of a refrigerant compressor unit through the upper end of the reheating flow channel G through a pipeline, and forms closed circulation to a refrigerant circulating system.

The invention mainly treats tail gas generated in a synthesis process or an ethylene production process by taking ethylene as a raw material, such as deaeration gas generated in the preparation process of vinyl acetate-ethylene copolymer, tail gas generated in the ethylene production process and the like, wherein the tail gas of the process usually contains ethylene, vinyl acetate or heavy components, nitrogen, methane, ethane, oxygen, carbon dioxide, water or methanol and the like, and the separation of the device can obtain ethylene product gas with the purity of more than 99.5 percent (mole), so that the recovery rate is higher, and the problem that the heavy components are easy to freeze at low temperature in the separation process is solved.

Drawings

Fig. 1 is a schematic view of the connection structure of the present invention.

Fig. 2 is a second schematic construction of the cryogenic separation cold box of fig. 1.

Fig. 3 is a third schematic view of the cryogenic separation cold box of fig. 1.

Fig. 4 is a schematic view of a fourth configuration of the cryogenic separation cold box of fig. 1.

Detailed Description

The invention will be described in detail with reference to the following drawings: as shown in fig. 1, a low-temperature ethylene purification device comprises a molecular sieve adsorption purification unit i, a low-temperature separation cold box unit ii, and a refrigerant supplement system, which are connected to each other by pipes, wherein the molecular sieve adsorption purification unit i is internally provided with a feed gas precooling heat exchanger 1, a water separation tank 2, a first molecular sieve adsorber 3, and a second molecular sieve adsorber 4, respectively, one end of the feed gas precooling heat exchanger 1 is connected to an external feed gas by a pipe, the other end of the feed gas precooling heat exchanger is connected to the water separation tank 2 by a pipe, the top of the water separation tank 2 is provided with a gas pipe, which is connected to the first molecular sieve adsorber 3 and the second molecular sieve adsorber 4, respectively, the bottoms of the first molecular sieve adsorber 3 and the second molecular sieve adsorber 4 are provided with a sewage pipe 13, which is connected to a sewage discharge system, the bottoms of the first molecular sieve adsorber 3 and the second molecular sieve adsorber 4 are connected to an electric heater or a steam heater 5 by a pipe 16, and the high-temperature regeneration gas can be sent to the first molecular sieve adsorber 3 or the second molecular sieve adsorber 4 to regenerate the molecular sieve, the first molecular sieve adsorber 3 and the second molecular sieve adsorber 4 are connected with the low-temperature separation cold box unit II through pipelines, and the purified gas enters the low-temperature separation cold box II.

And the low-temperature separation cold box II consists of a main plate fin type heat exchanger 6 with a plurality of built-in runners, a heavy component separation tank 7, an ethylene separation tank 8 or an ethylene purification tower 39, a refrigerant supplement system, a plurality of connecting pipelines and a plurality of throttle valves.

The pipeline is communicated with a flow channel A6a of the main plate fin type heat exchanger 6, and is communicated with a feed inlet in the middle of the heavy component separation tank 7 through the pipeline after being cooled in the flow channel E6E, heavy components in the process gas are condensed in the heavy component separation tank 7 and then discharged out of the cold box through the pipeline, and therefore the heavy components with high freezing points are prevented from freezing equipment and pipelines at the low-temperature part; the gas separated from the top of the heavy component separation tank 7 is communicated with the ethylene separation tank 8 or the ethylene purification tower 39 through a pipeline, a throttle valve V12 and a pipeline after being cooled in a flow passage B6B, the light component gas in the ethylene separation tank 8 or the ethylene purification tower 39 is separated, the top of the ethylene separation tank 8 or the ethylene purification tower 39 is connected with the lower end of a flow passage C6C of the main plate fin type heat exchanger 6 through a pipeline, and the upper end of the ethylene separation tank 8 or the ethylene purification tower 39 is connected with a non-condensable gas collecting device through a pipeline; the liquid at the bottom of the ethylene separation tank 8 or the ethylene purification tower 39 is communicated with the lower end of a flow channel D6D of the main plate fin heat exchanger 6 through a pipeline, a liquid level control valve V13 and a pipeline, the liquid is reheated through the flow channel D6D of the heat exchanger and then is connected with an ethylene product gas collection device through a pipeline to obtain high-purity ethylene product gas, and one side of the middle part of the ethylene separation tank 8 or the ethylene purification tower 39 is also connected with a refrigerant supplement system.

The refrigerant supplementing system is an ethylene storage tank 9 connected with liquid refrigerants on the outer side through a pipeline, wherein liquid at the bottom of the ethylene storage tank is communicated with a middle feeding hole of the ethylene separation tank 8 through the pipeline, a valve V14 and the pipeline, and is mixed with process gas phase to supplement cold for the system; and the top of the ethylene storage tank 9 is connected with a torch collecting device through a pipeline, so that the higher pressure of the device is maintained, and the overhigh pressure of the ethylene storage tank 9 is avoided.

The refrigerant supplementing system is a liquid siphon tank 31 connected with external liquid refrigerant through a pipeline and a valve V15, the liquid siphon tank 31 is communicated with the lower end and the middle end of a flow channel E6E of the main plate fin type heat exchanger 6 through the pipeline, the upper end of the flow channel E6E is communicated with the low-pressure gas collecting device through the pipeline, liquid evaporation in the main plate fin type heat exchanger 6 causes upper and lower density difference to realize liquid evaporation, and therefore continuous and stable cold energy is provided for the ethylene separation system.

Still be equipped with runner F6F in the mainboard finned heat exchanger 6, the lower extreme of this runner F6F is connected with heavy ends knockout drum 7 through pipeline, choke valve V16, is connected with the heavy ends collection device in the outside through the pipeline at the upper end of runner F6F, and this device can be through the evaporation cold volume of retrieving the heavy ends waste liquid to the feed gas that the heavy ends content is high to the cold volume of system is supplementary has been saved.

A refrigerant compressor unit III is further arranged above the main plate fin type heat exchanger 6, a tower bottom reboiler 40 is arranged at one side of the bottom of the main plate fin type heat exchanger 39, the tower bottom reboiler 40 is communicated with a flow channel A6a of the main plate fin type heat exchanger 6 through a pipeline, heat can flow into the flow channel A6a of the main plate fin type heat exchanger 6 through the pipeline, a pipeline is arranged at the other side of the tower bottom reboiler 40, cold can return to the flow channel A6a again, a tower top condenser 41 is arranged at the top of the ethylene purification tower 39, and the cold is communicated with a refrigerant circulating system through the pipeline.

The high-pressure gas of the refrigerant compressor unit III is communicated with the upper end of a flow channel H6H of the main plate fin type heat exchanger 6 through a pipeline, the high-pressure gas is divided into two parts through the pipeline after being cooled and condensed by the heat exchanger, one part is communicated with the refrigerant siphon tank 31 through a throttle valve V15 and the pipeline, and the upper end of the flow channel E6E is connected with the low-pressure end of the refrigerant compressor unit III through the pipeline; the other branch is communicated with the tower top condenser 41 through a pipeline and a throttle valve V17, is communicated with the lower end of a flow passage G6G of the main plate fin type heat exchanger 6 after reheating, is connected with the medium-pressure end of the refrigerant compressor unit III through the upper end of a reheating flow passage G6G through a pipeline, and forms closed circulation to the refrigerant circulation system.

The invention relates to a low-temperature ethylene purification device and a low-temperature ethylene purification method, which comprise a molecular sieve adsorption purification unit I, a low-temperature separation cold box unit II and a refrigerant supplement system, wherein the molecular sieve adsorption purification unit I comprises a molecular sieve adsorption purification unit I, a low-temperature separation cold box unit II and a refrigerant supplement system, and the low-temperature separation cold box unit II comprises a molecular sieve adsorption purification unit I, a molecular sieve adsorption purification unit II and a refrigerant supplement system, wherein the molecular sieve adsorption purification unit I comprises a molecular sieve adsorption purification unit I, a molecular sieve adsorption purification unit II and a molecular sieve adsorption purification unit II, and the low-temperature separation cold box unit II comprises a molecular sieve adsorption purification unit II, a molecular sieve adsorption purification unit I, a molecular sieve adsorption purification unit II and a refrigerant supplement system I, wherein: the tail gas is generated in the synthesis process or the ethylene production process by taking ethylene as a raw material, such as deaeration gas generated in the preparation process of vinyl acetate-ethylene copolymer, tail gas generated in the ethylene production process and the like, the tail gas in the process usually contains ethylene, vinyl acetate or heavy components, nitrogen, methane, ethane, oxygen, carbon dioxide, water or methanol and the like, and the tail gas is used as a raw material gas and is firstly sent to a raw material gas precooling heat exchanger 1 through a pipeline 10, and the heat exchanger is in the form of a shell-and-tube heat exchanger or a plate-fin heat exchanger. The cooled gas channel 12 is sent to the water separation tank 2, the liquid is sent out of the sewage system through a bottom pipeline 13, and the gas at the top of the water separation tank 2 is connected with the first molecular sieve adsorber 3 and the second molecular sieve adsorber 4 through a pipeline 14.

The first molecular sieve adsorber 3 and the second molecular sieve adsorber 4 are filled with molecular sieves, the molecular sieves adsorb easily-solidified components such as carbon dioxide, methanol or water in the mixed gas at low temperature on the premise of not adsorbing ethylene, so that pipelines and equipment are prevented from being frozen by the substances, the purified gas is connected with an inlet pipeline 15 of the low-temperature separation cold box unit II, and the purified gas is introduced into the low-temperature separation cold box II. The molecular sieve realizes automatic regeneration switching, low-pressure nitrogen is heated by an electric heater or a steam heater 5, and then high-temperature regeneration gas is sent to the first molecular sieve adsorber 3 or the second molecular sieve adsorber 4 through a pipeline 16 to regenerate the molecular sieve. The molecular sieve adsorption unit I is provided with program-controlled switching valves 1-11, so that adsorption and regeneration are automatically switched through a program, and unattended and intelligent operation is realized. The cryogenic separation cold box contains 4 variants, the total integration of which includes: the main plate-fin heat exchanger 6 is provided with 8 passages including 6 a-6 h at most, the reboiling plate-fin heat exchanger 40, the condensing plate-fin heat exchanger 41, the heavy component separation tank 7, the ethylene separation tank 8 or the ethylene purification tower 39, the ethylene storage tank 9 or the liquid refrigerant siphon tank 31 and further comprises pipelines 15-48 and throttle valves V12-V17 required by equipment connection.

An inlet pipeline 15 of the low-temperature separation cold box in the figure 1 is communicated with a flow channel 6a of the main plate fin type heat exchanger 6, and is communicated with a middle feed inlet of a heavy component separation tank 7 through a pipeline 18 after being cooled in a flow channel 6e, heavy components (such as VAC, heavy hydrocarbon components and other heavy components) in the process gas are condensed in the heavy component separation tank 7 and discharged out of the cold box through a pipeline 19, and the heavy components with high freezing points are prevented from freezing equipment and pipelines at the low-temperature part; the gas separated from the top of the heavy component separation tank 7 passes through a pipe 20, is cooled in a flow passage 6b, and then is communicated with the ethylene separation tank 8 through a pipe 21, a throttle valve V12 and a pipe 22, and the light component gas is separated from the ethylene separation tank 8.

The top of the ethylene separation tank 8 is connected with the lower end of a flow channel C6C of the main plate fin heat exchanger 6 through a pipeline 23, and the upper end of the ethylene separation tank is connected with a non-condensable gas collecting device through a pipeline 24; the liquid at the bottom of the ethylene separation tank 8 is communicated with the lower end of a flow channel D6D of the main plate fin type heat exchanger 6 through a pipeline 25, a liquid level control valve V13 and a pipeline 26, and the liquid is reheated through the flow channel D6D of the heat exchanger and then is connected with an ethylene product gas collection device through a pipeline 27, so that high-purity ethylene product gas is obtained.

The cryogen of the low-temperature separation cold box is supplemented by high-purity ethylene liquid, and the ethylene liquid from the ethylene storage equipment is communicated with the liquid inlet in the middle of the ethylene storage tank 9 through a pipeline 27. The ethylene storage tank 9 is characterized in that: in order to keep the continuous operation of the device, the liquid at the bottom of the ethylene storage tank is communicated with the middle feed inlet of the ethylene separation tank 8 through a pipeline 29, a valve V14 and a pipeline 30, and is mixed with the process gas phase to supplement the cold energy for the system; meanwhile, the top of the ethylene storage tank 9 is connected with a flare collecting device through a pipeline 28, so that the higher pressure of the device is maintained, and the overhigh pressure of the ethylene storage tank 9 is avoided.

Fig. 2 is a modification of the cryogenic separation cold box shown in fig. 1, in which the refrigerant supplement system is modified from the cold supplied from the ethylene storage tank 9 into liquid refrigerant and communicated with the middle feed inlet of the liquid siphon tank 31 through the pipeline 32, the throttle valve V15 and the pipeline 33, the liquid siphon tank 31 is communicated with the lower end and the middle end of the flow channel E6E of the main plate fin heat exchanger 6 through the pipeline 35 and the pipeline 34, and the upper end of the flow channel E6E is communicated with the low-pressure gas collection device through the pipeline 36. The mechanism is that the liquid evaporation is realized through the difference of upper and lower densities caused by the evaporation of the liquid in the main plate fin type heat exchanger 6, thereby providing continuous and stable cold energy for the ethylene separation system.

Fig. 3 is a modification of the cryogenic separation cold box of fig. 1 or fig. 2, in which the liquid in the heavy component separation tank 7 is communicated with the lower end of a flow channel F6F of the main plate fin heat exchanger 6 through a pipeline 19, a throttle valve V16 and a pipeline 37, and the upper end of the flow channel F6F is connected with a heavy component collection device through a pipeline 38. The device can recover the evaporation cold quantity of the heavy component waste liquid for the raw material gas with high heavy component content, thereby saving the cold quantity supplement of the system.

Fig. 4 is an upgraded version of the cryogenic separation cold box of fig. 3, with the ethylene separation tank 8 replaced by an ethylene purification column 39, and with a circulating refrigerant compression system added to refrigerant compressor unit iii.

The ethylene purification tower 39 is characterized in that: the ethylene purification tower 39 is in a packed tower type, similar to the connection type of the ethylene separation tank 8, the top of the ethylene purification tower is communicated with a flow channel C6C of the main plate fin heat exchanger 6 through a pipeline 23, and the bottom liquid is communicated with a flow channel D6D of the main plate fin heat exchanger 6 through a pipeline 25, a throttle valve V13 and a pipeline 26; meanwhile, the ethylene purification tower 39 is provided with a tower bottom reboiler 40 at the bottom, the heat of the ethylene purification tower is communicated with a flow channel A6a of the main plate fin heat exchanger 6 through a pipeline 42, and the ethylene purification tower is cooled and then returns to the flow channel A6a through a pipeline 43; the top of the ethylene purification tower 39 is provided with an overhead condenser 41, the refrigeration capacity of which is communicated with the refrigerant circulation system through a pipeline 45 and a pipeline 46.

In the refrigerant circulating system, high-pressure gas from the refrigerant compressor unit III is communicated with the upper end of a flow channel H6H of the main plate fin type heat exchanger 6 through a pipeline 48, is divided into two parts through a pipeline 32 after being cooled and condensed by the heat exchanger, one part is communicated with a refrigerant siphon tank 31 through a throttle valve V15 and a pipeline 33, the evaporation of the high-pressure gas is similar to the evaporation mode of the liquid siphon tank 31 of the low-temperature separation cold box II-2, and the difference is that the upper end of the flow channel E6E is connected with the low-pressure end of the refrigerant compressor unit III through a pipeline 36; the other branch is communicated with the tower top condenser 41 through a pipeline 44, a throttle valve V17 and a pipeline 45, is communicated with the lower end of a flow channel G6G of the main plate fin type heat exchanger 6 after reheating, is connected with the medium-pressure end of the refrigerant compressor unit III through the upper end of a reheating flow channel G6G through a pipeline 47, and forms closed circulation to the refrigerant circulation system.