Tail gas unpowered recovery system

Abstract

The invention provides an unpowered tail gas recovery system. The unpowered tail gas recovery system comprises a cryogenic separation cold box; the cryogenic separation cold box is communicated with the auxiliary system skid through a liquid phase pipeline, and a liquid phase product in the cryogenic separation cold box is conveyed to the auxiliary system skid through the liquid phase pipeline; the intermediate heat exchanger is arranged on the liquid phase pipeline, the liquid phase pipeline is communicated with a first heat exchange pipeline of the intermediate heat exchanger, a second heat exchange pipeline of the intermediate heat exchanger is communicated with the ice maker pipeline, and an ice maker refrigerant enters the intermediate heat exchanger through the ice maker pipeline and exchanges heat with a liquid phase product. The problem that in the prior art, an unpowered tail gas recovery system is large in energy consumption is solved.

Description

Technical Field

[0001] The invention relates to the technical field of coal processing, and in particular to an unpowered tail gas recovery system. Background Art

[0002] The Unipol polyethylene process exhaust gas recovery system is used to recover comonomers (butene-1 / hexene-1) and hydrocarbon materials such as ICA from the exhaust gas of the product degassing bin.

[0003] The gas phase materials containing hydrocarbon materials at the top of the degassing bin can be discharged to the ground flare or exhaust gas recovery system through the exhaust gas of the product degassing bin. The exhaust gas filtered by the product degassing bin filter is filtered through the inlet protection filter and cooled to no higher than 40°C by the low-pressure cooler. The condensate flows into the low-pressure collection tank, and the liquid in the tank is pumped to the inter-stage collection tank by the low-pressure condensate pump. The gas discharged from the top of the tank enters the first-stage inlet of the exhaust gas compressor and is compressed to above 0.23MPa.

[0004] The gas after primary compression is cooled to no higher than 40°C by the inter-stage cooler, and the condensate flows into the inter-stage collection tank. The liquid in the tank is returned to the reactor feed system by the inter-stage condensate pump. The gas discharged from the top of the tank enters the second-stage inlet of the exhaust gas compressor and is compressed to 1.2MPa. The gas after secondary compression is cooled to 40°C and -16°C respectively by the high-pressure cooler and high-pressure condenser, and the condensate flows into the high-pressure collection tank. The recovered liquid is returned to the reactor by the high-pressure condensate pump. The gas discharged from the high-pressure collection tank is used as the conveying gas of the product discharge system, and the product is transported from the product blow-out tank of the product discharge system to the product degassing bin. The excess gas is further recycled and utilized by the tail gas unpowered recovery system for the hydrocarbons in the tail gas.

[0005] The existing unpowered tail gas recovery facilities use the double expansion self-cryogenic separation technology of expander and throttle valve to separate the high-pressure tail gas of the original flare system into oligomers and hydrocarbon-rich liquids after deep cooling, thereby achieving the purpose of recovering hydrocarbon materials and reducing unit consumption.

[0006] The current tail gas unpowered recovery system operates normally, recovering about 500 kg of hydrocarbons per hour, and the system operates stably. The disadvantage of the prior art is that the hydrocarbon material separated from the cold box needs to be heated by steam when separating the ethylene-rich gas and heavy hydrocarbons. The steam consumption is 100 kg per hour, and 800 tons of steam are consumed per year, which increases the energy consumption of the device. Summary of the invention

[0007] The main purpose of the present invention is to provide an unpowered exhaust gas recovery system to solve the problem of high energy consumption of unpowered exhaust gas recovery systems in the prior art.

[0008] In order to achieve the above-mentioned purpose, the present invention provides an unpowered exhaust gas recovery system, including: a cryogenic separation cold box; an auxiliary system skid, the cryogenic separation cold box and the auxiliary system skid are connected through a liquid phase pipeline, and the liquid phase product in the cryogenic separation cold box is transported to the auxiliary system skid through the liquid phase pipeline; an intermediate heat exchanger, the intermediate heat exchanger is arranged on the liquid phase pipeline, the liquid phase pipeline is connected to a first heat exchange pipeline of the intermediate heat exchanger, the second heat exchange pipeline of the intermediate heat exchanger is connected to an ice machine pipeline, and the ice machine refrigerant enters the intermediate heat exchanger through the ice machine pipeline and exchanges heat with the liquid phase product.

[0009] Furthermore, the unpowered exhaust gas recovery system also includes an ice machine cooler, which is arranged on the ice machine pipeline and is connected to the second heat exchange pipeline of the intermediate heat exchanger through the ice machine pipeline.

[0010] Furthermore, the ice machine cooler is located downstream of the intermediate heat exchanger, and the ice machine refrigerant enters the ice machine cooler after passing through the intermediate heat exchanger.

[0011] Furthermore, the refrigerant of the ice machine is ethylene glycol aqueous solution.

[0012] Furthermore, the unpowered exhaust gas recovery system also includes a steam pipeline, which is connected to the auxiliary system skid and can supply steam to the auxiliary system skid.

[0013] Furthermore, the auxiliary system skid includes a first gas-liquid separator, and the first gas-liquid separator is connected to the liquid phase pipeline.

[0014] Furthermore, the auxiliary system skid also includes an ethylene-rich pipeline, a heavy hydrocarbon pipeline and a steam condensation pipeline. The ethylene-rich pipeline is connected to the top of the first gas-liquid separator, the heavy hydrocarbon pipeline is connected to the bottom of the first gas-liquid separator, and the steam condensation pipeline is connected to the bottom side of the first gas-liquid separator.

[0015] Furthermore, the deep-cold separation cold box includes: a plate heat exchanger, which is connected to the liquid phase pipeline; a second gas-liquid separator, whose inlet end is connected to the outlet end of the plate heat exchanger, and whose outlet end is connected to the inlet end of the plate heat exchanger. The hydrocarbon substances condensed in the plate heat exchanger enter the second gas-liquid separator for separation, and the liquid phase products obtained by separation are transported back to the plate heat exchanger to recover the cold energy and then transported to the intermediate heat exchanger through the liquid phase pipeline.

[0016] Furthermore, the second gas-liquid separator is the first or multiple second gas-liquid separators. When there are multiple second gas-liquid separators, the second gas-liquid separators are connected in series in sequence, and the bottom outlet of each second gas-liquid separator is respectively connected to the inlet of the next second gas-liquid separator. The bottom outlet of the second gas-liquid separator at the end is connected to the plate heat exchanger, and the top outlets of all second gas-liquid separators are connected to the plate heat exchanger.

[0017] Furthermore, the cryogenic separation cold box also includes a turbine expander, which is connected to the plate heat exchanger. The hydrocarbon substances condensed in the plate heat exchanger enter the second gas-liquid separator for separation. The separated gas products are transported back to the plate heat exchanger to recover the cold energy and then enter the refrigeration end of the turbine expander for expansion and refrigeration. Then, they are transported back to the plate heat exchanger to recover the cold energy and are heated at the braking end of the turbine expander and then discharged to the flare system.

[0018] By applying the technical solution of the present invention, an intermediate heat exchanger is arranged between the cryogenic separation cold box and the auxiliary system skid, and the intermediate heat exchanger can play a heat exchange role. The first heat exchange pipeline and the second heat exchange pipeline of the intermediate heat exchanger are respectively passed by the liquid phase product and the ice machine refrigerant. In this way, the liquid phase product with a lower temperature can exchange heat with the ice machine refrigerant with a relatively high temperature. For the liquid phase product, the temperature of the liquid phase product can be increased to meet the temperature requirements of subsequent separation, thereby reducing the amount of steam or not using steam for additional heating, reducing or eliminating the consumption of steam, thereby achieving the purpose of energy saving; and for the ice machine refrigerant, the temperature of the ice machine refrigerant has been reduced when it performs the subsequent role, so that it is not necessary to cool it later or the amount of cooling required for cooling later is reduced, which is beneficial to reducing the refrigeration load of the ice machine refrigerant. The above-mentioned setting method reduces the temperature of the ice machine refrigerant and increases the temperature of the hydrocarbon material, which is beneficial to reducing energy consumption from two aspects, and does not need to increase other additional energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 The schematic diagram of the structure of the tail gas unpowered recovery system of the present invention is shown.

[0021] The above drawings include the following reference numerals:

[0022] 10. Cryogenic separation cold box; 11. Plate heat exchanger; 12. Second gas-liquid separator; 13. Turbine expander; 20. Auxiliary system skid; 21. First gas-liquid separator; 22. Ethylene-rich pipeline; 23. Heavy hydrocarbon pipeline; 24. Steam condensation pipeline; 30. Liquid phase pipeline; 40. Intermediate heat exchanger; 50. Ice machine pipeline; 60. Ice machine cooler; 70. Steam pipeline. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0025] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0026] In order to solve the problem of high energy consumption of the unpowered exhaust gas recovery system in the prior art, the present invention provides an unpowered exhaust gas recovery system.

[0027] like Figure 1 The exhaust gas unpowered recovery system shown includes a cryogenic separation cold box 10, an auxiliary system skid 20 and an intermediate heat exchanger 40. The cryogenic separation cold box 10 is connected to the auxiliary system skid 20 through a liquid phase pipeline 30, and the liquid phase product in the cryogenic separation cold box 10 is transported to the auxiliary system skid 20 through the liquid phase pipeline 30; the intermediate heat exchanger 40 is arranged on the liquid phase pipeline 30, the liquid phase pipeline 30 is connected to the first heat exchange pipeline of the intermediate heat exchanger 40, and the second heat exchange pipeline of the intermediate heat exchanger 40 is connected to the ice machine pipeline 50, and the ice machine refrigerant enters the intermediate heat exchanger 40 through the ice machine pipeline 50 and exchanges heat with the liquid phase product.

[0028] In this embodiment, an intermediate heat exchanger 40 is arranged between the cryogenic separation cold box 10 and the auxiliary system skid 20. The intermediate heat exchanger 40 can play a heat exchange role. The first heat exchange pipeline and the second heat exchange pipeline of the intermediate heat exchanger 40 respectively have liquid products and ice machine refrigerant passing through them. In this way, the liquid products with lower temperature can exchange heat with the ice machine refrigerant with relatively higher temperature. For the liquid products, the temperature of the liquid products can be increased to meet the temperature requirements of subsequent separation, thereby reducing the amount of steam or not using steam for additional heating, reducing or eliminating the consumption of steam, thereby achieving the purpose of energy saving; and for the ice machine refrigerant, the temperature of the ice machine refrigerant has been reduced when it performs the subsequent function. In this way, it is not necessary to cool it later or the amount of cooling required for cooling later is reduced, which is conducive to reducing the refrigeration load of the ice machine refrigerant. The above-mentioned setting method reduces the temperature of the ice machine refrigerant and increases the temperature of the hydrocarbon material, which is conducive to reducing energy consumption from two aspects without increasing other additional energy consumption.

[0029] In this embodiment, the exhaust gas unpowered recovery system further includes an ice machine cooler 60, which is disposed on the ice machine pipeline 50 and communicated with the second heat exchange pipeline of the intermediate heat exchanger 40 through the ice machine pipeline 50. The ice machine cooler 60 is used to cool the ice machine refrigerant, thereby avoiding the problem that the intermediate heat exchanger 40 cannot cool the ice machine refrigerant to the required temperature due to insufficient heat exchange capacity, and ensuring that the ice machine refrigerant is cooled to the required temperature.

[0030] Preferably, the ice machine cooler 60 is located downstream of the intermediate heat exchanger 40, and the ice machine refrigerant enters the ice machine cooler 60 after passing through the intermediate heat exchanger 40. In this way, the ice machine refrigerant first passes through the intermediate heat exchanger 40 to exchange heat with the liquid phase product, and then passes through the ice machine cooler 60 for cooling after the heat exchange is completed, so that the temperature of the ice machine refrigerant finally obtained meets the requirements, and the situation that the temperature of the liquid phase product is unstable and the temperature of the ice machine refrigerant after the heat exchange is unstable is avoided. Of course, multiple ice machine coolers 60 can also be set, and ice machine coolers 60 can also be set upstream of the intermediate heat exchanger 40.

[0031] The refrigerant of the ice machine in this embodiment is ethylene glycol aqueous solution. More specifically, the ethylene glycol aqueous solution is -14°C before heat exchange, and is -20°C after heat exchange and cooling by the ice machine cooler 60. Of course, other types of liquids can also be used as ice machine refrigerants. The temperature of the liquid phase product produced by the cryogenic separation cold box 10 of this embodiment is about -40°C. After passing through the intermediate heat exchanger 40, the temperature can rise to above -20°C due to heat exchange with the ethylene glycol aqueous solution.

[0032] The exhaust gas unpowered recovery system of this embodiment further includes a steam pipeline 70, which is in communication with the auxiliary system skid 20 and can pass steam into the auxiliary system skid 20. The steam pipeline 70 is used to pass steam into the auxiliary system skid 20 for further heating when the temperature of the liquid phase product after heat exchange still does not meet the separation requirements, thereby ensuring that the temperature of the liquid phase product meets the requirements and ensuring the stability of the processing.

[0033] The auxiliary system skid 20 of this embodiment includes a first gas-liquid separator 21, which is a component for gas-liquid separation of liquid products. The first gas-liquid separator 21 is connected to a liquid phase pipeline 30. The liquid phase product obtained by the cryogenic separation cold box 10 is transported to the first gas-liquid separator 21 through the liquid phase pipeline 30 for separation, thereby obtaining ethylene-rich gas and heavy hydrocarbons. The steam pipeline 70 is also connected to the side of the middle and lower part of the first gas-liquid separator 21.

[0034] Furthermore, the auxiliary system skid 20 also includes an ethylene-rich pipeline 22, a heavy hydrocarbon pipeline 23 and a steam condensation pipeline 24. The ethylene-rich pipeline 22 is connected to the top of the first gas-liquid separator 21, the heavy hydrocarbon pipeline 23 is connected to the bottom of the first gas-liquid separator 21, and the steam condensation pipeline 24 is connected to the bottom side of the first gas-liquid separator 21. The lighter ethylene-rich gas obtained after separation in the first gas-liquid separator 21 is transported to the ethylene cracking unit through the top ethylene-rich pipeline 22, while the heavier heavy hydrocarbons are returned to the compressor inlet low-pressure liquid storage tank through the bottom heavy hydrocarbon pipeline 23, and are condensed through the compression condensation process and then sent to the reaction system. The condensed water formed by the steam can be discharged through the steam condensation pipeline 24.

[0035] In this embodiment, the cryogenic separation cold box 10 includes a plate heat exchanger 11 and a second gas-liquid separator 12. The inlet end of the middle and lower part of the plate heat exchanger 11 is connected to the tail gas intake pipeline, and the outlet end of the bottom of the plate heat exchanger 11 is connected to the liquid phase pipeline 30; the inlet end of the second gas-liquid separator 12 is connected to the outlet end of the middle and lower part of the plate heat exchanger 11, the outlet end of the top of the second gas-liquid separator 12 is connected to the inlet end of the top and middle part of the plate heat exchanger 11, and the outlet end of the bottom of the second gas-liquid separator 12 is connected to the inlet end of the bottom of the plate heat exchanger 11. In this way, the hydrocarbon substances condensed in the plate heat exchanger 11 enter the second gas-liquid separator 12 for separation, and the separated liquid phase product is transported back to the plate heat exchanger 11 to recover the cold, and then it can be transported to the intermediate heat exchanger 40 through the liquid phase pipeline 30. After heat exchange in the intermediate heat exchanger 40, it can be transported to the first gas-liquid separator 21 for gas-liquid separation to obtain ethylene-rich gas and heavy hydrocarbons.

[0036] Optionally, the second gas-liquid separator 12 is the first or multiple ones. In this embodiment, two are provided as an example. When there are multiple second gas-liquid separators 12, each second gas-liquid separator 12 is connected in series in sequence, and the bottom outlet of each second gas-liquid separator 12 is respectively connected to the inlet of the next second gas-liquid separator 12, and the bottom outlet of the second gas-liquid separator 12 at the end is connected to the plate heat exchanger 11, and the top outlets of all second gas-liquid separators 12 are connected to the plate heat exchanger 11. Along the flow direction, the top outlets of the two second gas-liquid separators 12 are respectively connected to the inlet end in the middle and the inlet end at the top of the plate heat exchanger 11. In this way, the liquid phase material in the second gas-liquid separator 12 can be sequentially separated into gas and liquid to obtain the final liquid phase product, and the gaseous material after each separation is returned to the plate heat exchanger 11 and subsequently transported to the flare system.

[0037] In this embodiment, the cryogenic separation cold box 10 further includes a turbine expander 13, which is connected to the plate heat exchanger 11. Specifically, the turbine expander 13 includes a refrigeration end and a brake end, and the two ends of the refrigeration end are respectively connected to the outlet end in the middle and the inlet end at the top of the plate heat exchanger 11, and the brake end is connected to the outlet end at the top of the plate heat exchanger 11. In this way, the hydrocarbon substances condensed in the plate heat exchanger 11 enter the second gas-liquid separator 12 for separation, and the separated gas phase products are transported back to the plate heat exchanger 11 to recover the cold and then enter the refrigeration end of the turbine expander 13 for expansion and refrigeration, and then transported back to the plate heat exchanger 11 to recover the cold and then discharged to the flare system after being heated up by the brake end of the turbine expander 13.

[0038] The overall working process of the exhaust gas unpowered recovery system of this embodiment is as follows:

[0039] The tail gas enters the deep cold separation cold box 10, and first enters the plate heat exchanger 11. After fully absorbing the cold, the temperature is reduced to become a gas-liquid mixture, and the hydrocarbon substances are condensed and enter the second gas-liquid separator 12 for separation; the gas phase product separated from the gas and liquid recovers the cold in the plate heat exchanger 11 and enters the refrigeration end of the turbine expander 13 for expansion and refrigeration, and then recovers the cold again through the plate heat exchanger 11, and is heated at the brake end of the turbine expander 13 before exiting the deep cold separation cold box 10 and being discharged to the flare system; and the liquid phase product recovers the cold in the plate heat exchanger 11 and exchanges heat with the ice machine refrigerant through the intermediate heat exchanger 40, and then enters the first gas-liquid separator 21 after heat exchange, and the steam is appropriately heated for gas-liquid separation to obtain ethylene-rich products and heavy hydrocarbon products respectively. The ethylene-rich gas product is sent to the ethylene cracking unit, and the heavy hydrocarbon product returns to the low-pressure liquid accumulation tank at the compressor inlet, is condensed through the compression and condensation process, and then is sent to the reaction system.

[0040] It should be noted that, the multiple in the above embodiments refers to at least two.

[0041] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0042] 1. Solve the problem of high energy consumption of the unpowered exhaust gas recovery system in the prior art;

[0043] 2. The temperature of the liquid product is increased to meet the temperature requirements for subsequent separation, thereby reducing the amount of steam used or completely eliminating the need for additional steam heating, thereby reducing or eliminating steam consumption and achieving energy saving;

[0044] 3. Subsequent cooling may not be required or the amount of cooling required for subsequent cooling may be reduced, thereby helping to reduce the refrigeration load of the ice machine refrigerant;

[0045] 4. The temperature of the refrigerant in the ice machine is lowered and the temperature of the hydrocarbon material is raised, which is beneficial to reducing energy consumption from two aspects without increasing other additional energy consumption.

[0046] Obviously, the above-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 ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0048] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A tail gas unpowered recovery system, characterized in that: include: Cryogenic separation cold box (10); An auxiliary system skid (20), wherein the cryogenic separation cold box (10) and the auxiliary system skid (20) are connected via a liquid phase pipeline (30), and the liquid phase product in the cryogenic separation cold box (10) is transported to the auxiliary system skid (20) via the liquid phase pipeline (30); An intermediate heat exchanger (40), wherein the intermediate heat exchanger (40) is arranged on the liquid phase pipeline (30), the liquid phase pipeline (30) is connected to a first heat exchange pipeline of the intermediate heat exchanger (40), and the second heat exchange pipeline of the intermediate heat exchanger (40) is connected to an ice machine pipeline (50), and the ice machine refrigerant enters the intermediate heat exchanger (40) through the ice machine pipeline (50) and exchanges heat with the liquid phase product.

2. The exhaust gas unpowered recovery system according to claim 1, characterized in that: The unpowered exhaust gas recovery system further comprises an ice machine cooler (60), wherein the ice machine cooler (60) is arranged on the ice machine pipeline (50) and is connected to the second heat exchange pipeline of the intermediate heat exchanger (40) through the ice machine pipeline (50).

3. The tail gas unpowered recovery system according to claim 2, characterized in that: The ice machine cooler (60) is located downstream of the intermediate heat exchanger (40), and the ice machine refrigerant enters the ice machine cooler (60) after passing through the intermediate heat exchanger (40).

4. The tail gas unpowered recovery system according to claim 1, characterized in that: The refrigerant of the ice machine is ethylene glycol aqueous solution.

5. The exhaust gas unpowered recovery system according to claim 1, characterized in that: The unpowered tail gas recovery system further comprises a steam pipeline (70), wherein the steam pipeline (70) is in communication with the auxiliary system skid (20) and is capable of supplying steam to the auxiliary system skid (20).

6. The tail gas unpowered recovery system according to claim 1, characterized in that: The auxiliary system skid (20) comprises a first gas-liquid separator (21), and the first gas-liquid separator (21) is in communication with the liquid phase pipeline (30).

7. The tail gas unpowered recovery system according to claim 6, characterized in that: The auxiliary system skid (20) further includes an ethylene-rich pipeline (22), a heavy hydrocarbon pipeline (23) and a steam condensation pipeline (24), wherein the ethylene-rich pipeline (22) is connected to the top of the first gas-liquid separator (21), the heavy hydrocarbon pipeline (23) is connected to the bottom of the first gas-liquid separator (21), and the steam condensation pipeline (24) is connected to the bottom side of the first gas-liquid separator (21).

8. The tail gas unpowered recovery system according to claim 1, characterized in that: The cryogenic separation cold box (10) comprises: a plate heat exchanger (11), the plate heat exchanger (11) being in communication with the liquid phase pipeline (30); A second gas-liquid separator (12), wherein the inlet end of the second gas-liquid separator (12) is connected to the outlet end of the plate heat exchanger (11), and the outlet end of the second gas-liquid separator (12) is connected to the inlet end of the plate heat exchanger (11). The hydrocarbon substances condensed in the plate heat exchanger (11) enter the second gas-liquid separator (12) for separation, and the liquid phase product obtained by separation is transported back to the plate heat exchanger (11) to recover cold energy and then transported to the intermediate heat exchanger (40) through the liquid phase pipeline (30).

9. The tail gas unpowered recovery system according to claim 8, characterized in that: The second gas-liquid separator (12) is the first or multiple second gas-liquid separators (12). When the second gas-liquid separators (12) are multiple, the second gas-liquid separators (12) are connected in series in sequence. The bottom outlet of each second gas-liquid separator (12) is respectively connected to the inlet of the next second gas-liquid separator (12). The bottom outlet of the second gas-liquid separator (12) at the end is connected to the plate heat exchanger (11), and the top outlets of all the second gas-liquid separators (12) are connected to the plate heat exchanger (11).

10. The unpowered exhaust gas recovery system according to claim 8, characterized in that: The cryogenic separation cold box (10) also includes a turbine expander (13), which is connected to the plate heat exchanger (11). The hydrocarbon substances condensed in the plate heat exchanger (11) enter the second gas-liquid separator (12) for separation, and the separated gaseous products are transported back to the plate heat exchanger (11) to recover the cold energy, and then enter the refrigeration end of the turbine expander (13) for expansion and refrigeration, and then transported back to the plate heat exchanger (11) to recover the cold energy, and then heated up at the braking end of the turbine expander (13) and discharged to the flare system.

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