Exhaust gas non-powered recovery system

Abstract

This invention provides a non-powered exhaust gas recovery system, comprising: a cryogenic separation cold box; an auxiliary system skid, the cryogenic separation cold box and the auxiliary system skid being connected via a liquid phase pipeline, the liquid phase product in the cryogenic separation cold box being transported to the auxiliary system skid via the liquid phase pipeline; and an intermediate heat exchanger, disposed on the liquid phase pipeline, the liquid phase pipeline being connected to a first heat exchange pipeline of the intermediate heat exchanger, and a second heat exchange pipeline of the intermediate heat exchanger being connected to an ice machine pipeline, the ice machine refrigerant entering the intermediate heat exchanger via the ice machine pipeline and exchanging heat with the liquid phase product. This invention solves the problem of high energy consumption in existing non-powered exhaust gas recovery systems.

Description

Technical Field

[0001] This invention relates to the field of coal processing technology, and more specifically, to a tail gas non-powered recovery system. Background Technology

[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 from the product degassing chamber.

[0003] The gaseous material containing hydrocarbons at the top of the degassing chamber can be discharged to a ground flare or exhaust gas recovery system. The exhaust gas, filtered by the product degassing chamber filter, passes through an inlet protection filter and is cooled to no higher than 40°C by a low-pressure cooler. The condensate flows into a low-pressure collection tank, where it is pumped to an inter-stage collection tank. The gas discharged from the top of the tank enters the first-stage inlet of the exhaust gas compressor and is compressed to above 0.23 MPa.

[0004] The gas after primary compression is cooled to no higher than 40°C by an interstage cooler. The condensate flows into an interstage collection tank, and the liquid in the tank is returned to the reactor feed system by an interstage 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 1.2 MPa. The gas after secondary compression is cooled to 40°C by a high-pressure cooler and -16°C by a high-pressure condenser. The condensate flows into a high-pressure collection tank, and the recovered liquid is returned to the reactor by a high-pressure condensate pump. The gas discharged from the high-pressure collection tank is used as the conveyor gas for the product discharge system, transporting the product from the product blow-out tank to the product degassing chamber. Excess gas is further recovered and reused by a tail gas non-powered recovery system to recover hydrocarbons from the tail gas.

[0005] The existing exhaust gas non-powered recovery facility adopts a dual expansion self-deep cryogenic separation technology using an expander and a throttle valve. This technology separates the high-pressure exhaust gas from the original flare system into oligomers and hydrocarbon-rich liquids after deep cryogenic separation, achieving the goal of hydrocarbon material recovery and reducing unit consumption.

[0006] The current exhaust gas recovery system is operating normally, recovering approximately 500 kg of hydrocarbons per hour, and the system is running stably. The drawback of the existing technology is that the hydrocarbons separated from the cold box require steam heating during the separation of ethylene-rich gas and heavy hydrocarbons, consuming 100 kg of steam per hour and 800 tons of steam per year, increasing the plant's energy consumption. Summary of the Invention

[0007] The main objective of this invention is to provide a non-powered exhaust gas recovery system to solve the problem of high energy consumption in existing non-powered exhaust gas recovery systems.

[0008] To achieve the above objectives, the present invention provides a non-powered exhaust gas recovery system, comprising: a cryogenic separation cold box; an auxiliary system skid, wherein the cryogenic separation cold box and the auxiliary system skid are connected by 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; and an intermediate heat exchanger, wherein the intermediate heat exchanger is disposed on the liquid phase pipeline, the liquid phase pipeline is connected to a first heat exchange pipeline of the intermediate heat exchanger, and the second heat exchange pipeline of the intermediate heat exchanger is connected to an ice machine pipeline, wherein 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 exhaust gas non-powered recovery system also includes an ice machine cooler, which is installed on the ice machine pipeline and 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 for the ice machine is an aqueous solution of ethylene glycol.

[0012] Furthermore, the exhaust gas non-powered recovery system also includes a steam pipeline that 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, which is connected to a 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 cryogenic separation cold box includes: a plate heat exchanger connected to a liquid phase pipeline; a second gas-liquid separator, the inlet of which is connected to the outlet of the plate heat exchanger, and the outlet of which is connected to the inlet of the plate heat exchanger. The hydrocarbons condensed in the plate heat exchanger enter the second gas-liquid separator for separation. The separated liquid phase product is transported back to the plate heat exchanger to recover its cooling capacity and then transported to the intermediate heat exchanger through the liquid phase pipeline.

[0016] Furthermore, there may be one or more second gas-liquid separators. When there are multiple second gas-liquid separators, they are connected in series. The bottom outlet of each second gas-liquid separator is 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. The top outlet of all second gas-liquid separators is connected to the plate heat exchanger.

[0017] Furthermore, the cryogenic separation cold box also includes a turboexpander, which is connected to a plate heat exchanger. The hydrocarbons condensed in the plate heat exchanger enter the second gas-liquid separator for separation. The separated gaseous product is sent back to the plate heat exchanger to recover the cold energy and then enters the refrigeration end of the turboexpander for expansion and cooling. After that, it is sent back to the plate heat exchanger to recover the cold energy, heated at the braking end of the turboexpander, and then discharged to the flare system.

[0018] By applying the technical solution of this invention, an intermediate heat exchanger is installed between the cryogenic separation cold box and the auxiliary system skid. This intermediate heat exchanger serves a heat exchange function, with liquid phase product and ice machine refrigerant passing through its first and second heat exchange pipes, respectively. This allows the lower-temperature liquid phase product to exchange heat with the relatively higher-temperature ice machine refrigerant. For the liquid phase product, this raises its temperature to meet the temperature requirements for subsequent separation, thereby reducing steam consumption or eliminating the need for additional steam heating, thus achieving energy saving. For the ice machine refrigerant, its temperature has already decreased before subsequent processing, so subsequent cooling is unnecessary or the required cooling capacity is reduced, thus lowering the refrigeration load on the ice machine refrigerant. This arrangement lowers the temperature of the ice machine refrigerant and raises the temperature of the hydrocarbon materials, both contributing to energy reduction without requiring additional energy consumption. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 A schematic diagram of the exhaust gas recovery system of the present invention is shown.

[0021] The above figures 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 Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0025] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0026] To address the problem of high energy consumption in existing exhaust gas recovery systems without power, this invention provides an exhaust gas recovery system without power.

[0027] like Figure 1 The exhaust gas non-powered 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 and the auxiliary system skid 20 are connected by a liquid phase pipeline 30. 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 installed 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. 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 installed between the cryogenic separation cold box 10 and the auxiliary system skid 20. The intermediate heat exchanger 40 serves a heat exchange function, with liquid phase product and ice machine refrigerant passing through its first and second heat exchange pipes, respectively. This allows the lower-temperature liquid phase product to exchange heat with the relatively higher-temperature ice machine refrigerant. For the liquid phase product, this raises its temperature to meet the temperature requirements for subsequent separation, thereby reducing steam consumption or eliminating the need for additional steam heating, thus achieving energy savings. For the ice machine refrigerant, its temperature has already decreased before subsequent processing, so subsequent cooling is unnecessary or the required cooling amount is reduced, thus lowering the refrigeration load on the ice machine refrigerant. This arrangement lowers the temperature of the ice machine refrigerant and raises the temperature of the hydrocarbon materials, both contributing to energy reduction without requiring additional energy consumption.

[0029] In this embodiment, the exhaust gas non-powered recovery system also includes an ice machine cooler 60, which is installed on the ice machine pipeline 50 and connected to the second heat exchange pipeline of the intermediate heat exchanger 40 via 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 is insufficient in heat exchange capacity and cannot cool the ice machine refrigerant to the required temperature when acting alone, 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 exchanges heat with the liquid product in the intermediate heat exchanger 40, and then passes through the ice machine cooler 60 for cooling. This ensures that the final temperature of the ice machine refrigerant meets the requirements, avoiding the situation where the unstable temperature of the liquid product leads to unstable temperature of the ice machine refrigerant after heat exchange. Of course, multiple ice machine coolers 60 can be provided, or an ice machine cooler 60 can also be provided upstream of the intermediate heat exchanger 40.

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

[0032] The exhaust gas non-powered recovery system of this embodiment also includes a steam pipeline 70, which is connected to the auxiliary system skid 20 and can supply steam to the auxiliary system skid 20. The steam pipeline 70 is used to supply steam to the auxiliary system skid 20 for further heating when the temperature of the liquid product after heat exchange still does not meet the separation requirements, thereby ensuring that the temperature of the liquid product meets the requirements and ensuring processing stability.

[0033] In this embodiment, the auxiliary system skid 20 includes a first gas-liquid separator 21, which is a component for separating the liquid phase product into gas and liquid phases. The first gas-liquid separator 21 is connected to the liquid phase pipeline 30. The liquid phase product obtained from 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 lower middle side 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 by 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 accumulator tank through the bottom heavy hydrocarbon pipeline 23, where they are condensed and sent to the reaction system. The condensate formed by the steam injection 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 lower inlet of the plate heat exchanger 11 is connected to the exhaust gas inlet pipe, and the bottom outlet of the plate heat exchanger 11 is connected to the liquid phase pipe 30. The inlet of the second gas-liquid separator 12 is connected to the lower outlet of the plate heat exchanger 11, the top outlet of the second gas-liquid separator 12 is connected to the top and middle inlet of the plate heat exchanger 11, and the bottom outlet of the second gas-liquid separator 12 is connected to the bottom inlet 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. The separated liquid product is transported back to the plate heat exchanger 11 to recover the cold energy, and then transported to the intermediate heat exchanger 40 through the liquid phase pipe 30. After heat exchange in the intermediate heat exchanger 40, it is transported to the first gas-liquid separator 21 for gas-liquid separation to obtain ethylene-rich gas and heavy hydrocarbons.

[0036] Optionally, there may be one or more second gas-liquid separators 12. This embodiment takes two as an example. When there are multiple second gas-liquid separators 12, they are connected in series. The bottom outlet of each second gas-liquid separator 12 is connected to the inlet of the next second gas-liquid separator 12. The bottom outlet of the last second gas-liquid separator 12 is connected to the plate heat exchanger 11. 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 connected to the inlet end in the middle and the top inlet end of the plate heat exchanger 11, respectively. In this way, the liquid phase in the second gas-liquid separator 12 can be sequentially separated into gas and liquid phases to obtain the final liquid phase product, while the gaseous material after each separation returns to the plate heat exchanger 11 and is subsequently transported to the flare system.

[0037] In this embodiment, the cryogenic separation cold box 10 also includes a turbine expander 13, which is connected to the plate heat exchanger 11. Specifically, the turbine expander 13 includes a cooling end and a braking end. The two ends of the cooling end are connected to the outlet end in the middle and the inlet end at the top of the plate heat exchanger 11, respectively, and the braking 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. The separated gaseous product is sent back to the plate heat exchanger 11 to recover its cooling capacity and then enters the cooling end of the turbine expander 13 for expansion and cooling. After recovering its cooling capacity, it is heated by the braking end of the turbine expander 13 and then discharged into the flare system.

[0038] The overall working process of the exhaust gas non-powered recovery system in this embodiment is as follows:

[0039] The exhaust gas enters the cryogenic separation cold box 10, first entering the plate heat exchanger 11. After fully absorbing the cold energy, the temperature decreases and it becomes a gas-liquid mixture. The hydrocarbons are condensed and enter the second gas-liquid separator 12 for separation. The gas phase product separated from the gas-liquid mixture recovers its cold energy in the plate heat exchanger 11 and then enters the refrigeration end of the turbine expander 13 for expansion and cooling. After recovering its cold energy again through the plate heat exchanger 11, it is heated at the braking end of the turbine expander 13 and then exits the cryogenic separation cold box 10 and is discharged to the flare system. The liquid phase product recovers its cold energy in the plate heat exchanger 11 and then exchanges heat with the refrigerant of the ice machine in the intermediate heat exchanger 40. After the heat exchange, it enters the first gas-liquid separator 21, where the steam is appropriately heated for gas-liquid separation, yielding ethylene-rich products and heavy hydrocarbon products respectively. The ethylene-rich gas product is sent to the ethylene cracking unit, while the heavy hydrocarbon product returns to the compressor inlet low-pressure accumulator tank, is condensed through the compression and condensation process, and then sent to the reaction system.

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

[0041] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0042] 1. It solves the problem of high energy consumption in existing exhaust gas recovery systems without power;

[0043] 2. This increases the temperature of the liquid product, thereby meeting the temperature requirements for subsequent separation. This reduces the amount of steam used or eliminates the need for additional steam heating, thus reducing or eliminating steam consumption and achieving energy saving.

[0044] 3. Subsequent cooling may not be required or the amount of cooling required may be reduced, which helps to reduce the refrigeration load of the refrigerant in the ice machine;

[0045] 4. This reduces the temperature of the refrigerant in the ice machine and increases the temperature of the hydrocarbon materials, thus reducing energy consumption in both aspects without requiring additional energy consumption.

[0046] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0047] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

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

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A non-powered exhaust gas recovery system, characterized in that, include: Cryogenic separation cold box (10); The auxiliary system skid (20) is connected to the cryogenic separation cold box (10) 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) is installed 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). The ice machine refrigerant enters the intermediate heat exchanger (40) through the ice machine pipeline (50) and exchanges heat with the liquid phase product. The auxiliary system skid (20) includes a first gas-liquid separator (21), which is connected to the liquid phase pipeline (30); 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 cryogenic separation cold box (10) includes: Plate heat exchanger (11), which is connected to the liquid phase pipeline (30); The second gas-liquid separator (12) has its inlet end connected to the outlet end of the plate heat exchanger (11) and its outlet end 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. The separated liquid phase product is transported back to the plate heat exchanger (11) to recover the cold energy and then transported to the intermediate heat exchanger (40) through the liquid phase pipeline (30).

2. The exhaust gas non-powered recovery system according to claim 1, characterized in that, The exhaust gas non-powered recovery system also includes an ice machine cooler (60), which is installed on the ice machine pipeline (50) and connected to the second heat exchange pipeline of the intermediate heat exchanger (40) through the ice machine pipeline (50).

3. The exhaust gas non-powered 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 exhaust gas non-powered recovery system according to claim 1, characterized in that, The refrigerant for the ice machine is an aqueous solution of ethylene glycol.

5. The exhaust gas non-powered recovery system according to claim 1, characterized in that, The exhaust gas non-powered recovery system also includes a steam pipeline (70), which is connected to the auxiliary system skid (20) and can supply steam to the auxiliary system skid (20).

6. The exhaust gas non-powered recovery system according to claim 1, characterized in that, The second gas-liquid separator (12) is the first or multiple. When there are multiple second gas-liquid separators (12), each second gas-liquid separator (12) is connected in series. The bottom outlet of each second gas-liquid separator (12) is 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). The top outlet of all second gas-liquid separators (12) is connected to the plate heat exchanger (11).

7. The exhaust gas non-powered recovery system according to claim 1, characterized in that, The cryogenic separation cold box (10) also includes a turboexpander (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. The separated gas phase product is sent back to the plate heat exchanger (11) to recover the cold energy and then enters the refrigeration end of the turboexpander (13) for expansion and refrigeration. Then it is sent back to the plate heat exchanger (11) to recover the cold energy. After being heated by the braking end of the turboexpander (13), it is discharged to the flare system.

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