Device for recovering light hydrocarbon from plastic pyrolysis gas

Abstract

The utility model relates to a device for recovering light hydrocarbon from plastic pyrolysis gas. The device comprises a first cooling unit, a second cooling unit and a light hydrocarbon collecting unit, wherein the first cooling unit and the second cooling unit are heat exchange elements serving as a light hydrocarbon collecting unit; the light hydrocarbon collecting unit is used for collecting light hydrocarbon from raw material gas generated by plastic pyrolysis, the plastic pyrolysis gas is retreated through the device, stable light hydrocarbon recovery is achieved, and good economic benefits are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of recycling and utilization of gases generated by plastic pyrolysis, in particular to a device for recovering light hydrocarbons from plastic pyrolysis gas. Background Art

[0002] With the increasing dependence of modern social life on plastic products, the amount of waste plastic products is also increasing continuously. The main method for recycling and reprocessing plastics is pyrolysis. Plastic pyrolysis gas is the gas generated when plastics are heated and decomposed, and its main components are low-molecular substances such as methane, ethane, ethylene, and hydrogen, and also contains a considerable amount of propane, propylene, 1-butene, etc.

[0003] Plastic pyrolysis gas is generally only used for combustion to supply heat for the pyrolysis process. However, the pyrolysis gas contains a large amount of chemical raw materials such as ethylene and propylene. Therefore, if the plastic pyrolysis gas is directly used for combustion to supply heat, it may produce toxic gases and smoke. The light hydrocarbons in the plastic pyrolysis gas belong to environmentally friendly fuels. Therefore, it is necessary to recover the combustible light hydrocarbons in the plastic pyrolysis gas, which has good economic benefits for combustion and subsequent processing. Summary of the Utility Model

[0004] The technical problem to be solved by the utility model is to process the plastic pyrolysis gas to separate the light hydrocarbons in the plastic pyrolysis gas

[0005] for recycling. In view of the above defects of the prior art, a device for recovering light hydrocarbons from plastic pyrolysis gas is provided.

[0006] In order to solve the above technical problems, the technical solution adopted by the utility model is as follows:

[0007] Construct a device for recovering light hydrocarbons from plastic pyrolysis gas, including a first cooling unit, a second cooling unit, and a light hydrocarbon collection unit;

[0008] Wherein both the first cooling unit and the second cooling unit are heat exchange elements of the light hydrocarbon collection unit;

[0009] The light hydrocarbon collection unit is used to collect light hydrocarbons from the raw material gas generated by plastic pyrolysis.

[0010] Preferably, the light hydrocarbon collection unit includes a pre-cooler, a secondary cooler, a de-ethanizer, a top cooler, a reboiler, and a top separator;

[0011] The raw material inlet in the pre-cooler is connected to the plastic pyrolysis gas supply pipe, the raw material outlet in the pre-cooler is connected to the raw material inlet of the secondary cooler through a pipeline, and the raw material outlet of the secondary cooler is connected to the middle inlet of the de-ethanizer through a pipeline; the top outlet of the de-ethanizer is connected to the raw material inlet of the top cooler through a pipeline, the raw material outlet of the top cooler is connected to the inlet of the top separator through a pipeline, the top raw material outlet of the top separator is connected to the raw material inlet of the pre-cooler, and the bottom raw material outlet of the top separator is connected to the raw material inlet of the upper part of the de-ethanizer through a pipeline. The raw material outlet of the pre-cooler is connected to the gas transmission pipeline to send the reheated gas to the device gas consumption point as fuel gas after being reheated to room temperature; the bottom raw material outlet of the de-ethanizer is connected to the raw material inlet of the bottom reboiler, and the raw material outlet of the bottom reboiler is connected to the light hydrocarbon storage device.

[0012] Preferably, in the light hydrocarbon collection unit:

[0013] The pre-cooler is used to cool the plastic pyrolysis gas so that the temperature of the plastic pyrolysis gas at the raw material outlet of the pre-cooler is about 15°C;

[0014] The secondary cooler is used to cool the plastic pyrolysis gas treated by the pre-cooler so that the temperature of the plastic pyrolysis gas at the raw material outlet of the secondary cooler is -35°C;

[0015] The de-ethanizer is used to rectify and separate the plastic pyrolysis gas treated by the secondary cooler so that the light components at -45°C are distilled out from the top outlet of the de-ethanizer and enter the top cooler, and the C3+ heavy components at 36°C enter the bottom reboiler from the bottom outlet of the de-ethanizer;

[0016] The top cooler is used to cool the -45°C light hydrocarbons distilled out from the top outlet of the de-ethanizer so that the light hydrocarbons are cooled to -59°C;

[0017] The top separator is used to separate the gas and liquid of the -59°C light hydrocarbons, and the separated gas is transported to the pre-cooler to be reheated to room temperature and then sent to the device gas consumption point as fuel gas, and the separated liquid is refluxed to the upper part of the de-ethanizer through a pipeline;

[0018] The bottom reboiler is used to heat the 36°C C3+ heavy components entering it to 38°C to vaporize the light components and return them to the lower part of the de-ethanizer for heat and mass transfer, and another part of the light hydrocarbons is sent to the light hydrocarbon storage tank.

[0019] Preferably, the first cooling unit includes a refrigerant compressor A, a refrigerant cooler A, a bottom reboiler, a refrigerant throttle valve A, and a secondary cooler; the refrigerant pipelines in the refrigerant compressor A, the refrigerant cooler, the bottom reboiler, the refrigerant throttle valve A, and the secondary cooler are sequentially connected to form a first refrigerant circuit, and a first refrigerant is injected into the first refrigerant circuit.

[0020] Preferably, in the first cooling unit:

[0021] The refrigerant compressor A is used to compress and transport the first refrigerant to the refrigerant cooler A;

[0022] The refrigerant cooler A is used to cool down the first refrigerant to 55°C;

[0023] The bottom reboiler is used to cool the first refrigerant to the liquefied state at 45°C;

[0024] The refrigerant throttle valve A is used to adjust and reduce the pressure of the first refrigerant circuit;

[0025] The secondary cooler is used to provide cooling capacity for the secondary cooling of the plastic pyrolysis gas.

[0026] Preferably, the second cooling unit includes a refrigerant compressor, a refrigerant cooler, a refrigerant heat exchanger, a throttle valve, and a top cooler; wherein the refrigerant pipelines in the refrigerant compressor B, the refrigerant cooler B, the refrigerant heat exchanger, the refrigerant throttle valve B, and the top cooler are sequentially connected to form a second refrigerant circuit, and a second refrigerant is injected into the second refrigerant circuit.

[0027] Preferably, in the second cooling unit:

[0028] The refrigerant compressor B is used to compress and transport the second refrigerant to the refrigerant cooler B;

[0029] The refrigerant cooler B is used to cool down the temperature of the second refrigerant to 45°C;

[0030] The refrigerant heat exchanger is used to condense the second refrigerant to the liquefied state at -60°C;

[0031] The refrigerant throttle valve B is used to adjust and reduce the pressure of the second refrigerant circuit.

[0032] The top cooler 6 is used to exchange heat with the plastic pyrolysis gas.

[0033] The beneficial effects of the present utility model are as follows:

[0034] 1. Through the synergistic effect of the first cooling unit and the second cooling unit, the present utility model can effectively cool and separate the light hydrocarbons in the plastic pyrolysis gas, improving the recovery rate and purity of the light hydrocarbons.

[0035] 2. In the present utility model, components such as the pre-cooler, secondary cooler, deethanizer, top cooler, and bottom reboiler minimize energy consumption and reduce operating costs through precise temperature control and heat exchange design.

[0036] 3. The utility model reduces greenhouse gas emissions by recovering and utilizing light hydrocarbons in plastic pyrolysis gas, contributing to environmental protection and sustainable development.

[0037] 4. Components such as the refrigerant compressor, refrigerant cooler, and throttle valve in the utility model can be adjusted according to actual production requirements, ensuring the flexibility and adaptability of the device.

[0038] 5. By forming the first refrigerant circuit and the second refrigerant circuit, the utility model ensures the stability and reliability of the cooling process and reduces the possibility of system failures.

[0039] 6. By efficiently recovering light hydrocarbons and using them as fuel gas, the utility model not only reduces dependence on external energy but also brings additional economic benefits to the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will further illustrate the present utility model in conjunction with the drawings and embodiments. The drawings in the following description are only partial embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings:

[0041] Figure 1 It is a schematic diagram of the overall structure connection of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] In order to make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present utility model. Obviously, the described embodiments are partial embodiments of the present utility model, rather than all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present utility model.

[0043] As Figure 1 shown, a device for recovering light hydrocarbons from plastic pyrolysis gas includes a first cooling unit, a second cooling unit, and a light hydrocarbon collection unit;

[0044] wherein both the first cooling unit and the second cooling unit are heat exchange elements serving as the light hydrocarbon collection unit;

[0045] The light hydrocarbon collection unit is used to collect light hydrocarbons from the raw material gas generated by plastic pyrolysis.

[0046] In this embodiment, the light hydrocarbon collection unit includes a pre-cooler 1, a secondary cooler 2, a de-ethanizer 4, a top cooler 6, a reboiler 5, and a top separator 7;

[0047] The raw material inlet in the pre-cooler 1 is connected to the plastic pyrolysis gas supply pipe. The raw material outlet in the pre-cooler 1 is connected to the raw material inlet of the secondary cooler 2 through a pipeline. The raw material outlet of the secondary cooler 2 is connected to the middle inlet of the de-ethanizer 4 through a pipeline. The top outlet of the de-ethanizer 4 is connected to the raw material inlet of the top cooler 6 through a pipeline. The raw material outlet of the top cooler 6 is connected to the inlet of the top separator 7 through a pipeline. The top raw material outlet of the top separator 7 is connected to the raw material inlet of the pre-cooler 1, and the bottom raw material outlet of the top separator 7 is connected to the raw material inlet of the upper part of the de-ethanizer 4 through a pipeline. The raw material outlet of the pre-cooler 1 is connected to the gas transmission pipeline to send the reheated gas at normal temperature as fuel gas to the gas consumption point of the device. Of course, it can also be stored as fuel gas for other uses. The bottom raw material outlet of the de-ethanizer 4 is connected to the raw material inlet of the bottom reboiler 5, and the raw material outlet of the bottom reboiler 5 is connected to the light hydrocarbon storage device.

[0048] In this embodiment, in the light hydrocarbon collection unit:

[0049] The pre-cooler 1 is used to cool the plastic pyrolysis gas so that the temperature of the plastic pyrolysis gas at the raw material outlet of the pre-cooler 1 is about 15°C.

[0050] The secondary cooler 2 is used to cool the plastic pyrolysis gas processed by the pre-cooler 1 so that the temperature of the plastic pyrolysis gas at the raw material outlet of the secondary cooler 2 is -35°C.

[0051] The de-ethanizer 4 is used to rectify and separate the plastic pyrolysis gas processed by the secondary cooler 2 so that the light components at -45°C are distilled out from the top outlet of the de-ethanizer 4 and enter the top cooler 6, and the C3+ heavy components at 36°C enter the bottom reboiler 5 from the bottom outlet of the de-ethanizer 4.

[0052] The top cooler 6 is used to cool the -45°C light hydrocarbons distilled out from the top outlet of the de-ethanizer 4 so that the light hydrocarbons are cooled to -59°C.

[0053] The top separator 7 is used to separate the gas and liquid of the -59°C light hydrocarbons, and the separated gas is transported to the pre-cooler 1 (it should be noted that the light hydrocarbons enter the pre-cooler 1 as a refrigerant) to be reheated to normal temperature and then sent as fuel gas to the gas consumption point of the device. The separated liquid flows back to the upper part of the de-ethanizer 4 through a pipeline.

[0054] The bottom reboiler 5 is used to heat the 36°C C3+ heavy components entering it to 38°C to vaporize the light components and return them to the lower part of the de-ethanizer 4 for heat and mass transfer, and another part of the light hydrocarbons is sent to the light hydrocarbon storage tank.

[0055] In this embodiment, the first cooling unit includes a refrigerant compressor A12, a refrigerant cooler A13, a bottom reboiler 5, a refrigerant throttle valve A3, and a secondary cooler 2. Among them, the refrigerant pipelines in the refrigerant compressor A12, the refrigerant cooler A13, the bottom reboiler 5, the refrigerant throttle valve A3, and the secondary cooler 2 are sequentially connected to form a first refrigerant circuit.

[0056] It should be noted in the description that in the first cooling unit:

[0057] The refrigerant compressor A12 is used to compress and transport the first refrigerant into the refrigerant cooler A13.

[0058] The refrigerant cooler A13 is used to cool down the first refrigerant to 55°C.

[0059] The bottom reboiler 5 is used to cool the first refrigerant to the liquefied state at 45°C.

[0060] The refrigerant throttle valve A3 is used to adjust and reduce the pressure of the first refrigerant circuit.

[0061] The secondary cooler 2 is used to provide cooling capacity for the secondary cooling of the plastic pyrolysis gas.

[0062] In this embodiment, the second cooling unit includes a refrigerant compressor B8, a refrigerant cooler B9, a refrigerant heat exchanger 10, a refrigerant throttle valve B9, and a top cooler 6. Among them, the refrigerant pipelines in the refrigerant compressor B8, the refrigerant cooler B9, the refrigerant heat exchanger 10, the refrigerant throttle valve B11, and the top cooler 6 are sequentially connected to form a second refrigerant circuit.

[0063] It should be noted that in the second cooling unit:

[0064] The refrigerant compressor B8 is used to compress and transport the second refrigerant into the refrigerant cooler B.

[0065] The refrigerant cooler B9 is used to cool down the temperature of the second refrigerant to 45°C.

[0066] The refrigerant heat exchanger 10 is used to condense the second refrigerant to the liquefied state at -60°C.

[0067] The refrigerant throttle valve B11 is used to adjust and reduce the pressure of the second refrigerant circuit.

[0068] The top cooler 6 is used to exchange heat with the plastic pyrolysis gas.

[0069] The specific operation of the first refrigerant circuit of the present utility model is as follows: The first refrigerant is first compressed by the refrigerant compressor A12, and then cooled to 55°C by the refrigerant cooler A13. The first refrigerant at 55°C enters the bottom reboiler 5 and is cooled and condensed to 45°C to be completely liquefied. The liquefied first refrigerant passes through the refrigerant throttle valve A3, where it undergoes throttling and pressure reduction, and partial vaporization occurs, with the temperature dropping to -39°C. Finally, the first refrigerant at -39°C enters the secondary cooler 2 to provide cooling capacity for the secondary cooler. After complete vaporization during rewarming, it returns to the refrigerant compressor A12 to continue participating in the next cycle.

[0070] The specific operation of the second refrigerant circuit of the present utility model is as follows: The second refrigerant is first compressed by the refrigerant compressor B8, and then cooled to 45°C by the refrigerant cooler B9. It enters the refrigerant heat exchanger 10 and is cooled and condensed to -60°C to be completely liquefied. After passing through the refrigerant throttle valve B11 for throttling and pressure reduction, partial vaporization occurs, with the temperature dropping to -79°C. It enters the top cooler 6 to provide cooling capacity, is rewarmed to -59°C with partial vaporization, and then enters the refrigerant heat exchanger 10 again to be completely vaporized after rewarming, and returns to the refrigerant compressor B8 to continue participating in the next cycle.

[0071] The specific process for recovering light hydrocarbons in the present utility model is as follows: The plastic pyrolysis gas enters the precooler 1 through a pipeline and is preliminarily cooled to about 15°C, and then enters the secondary cooler 2 and is cooled to -35°C, with partial liquefaction. It enters the middle part of the deethanizer 4, and rectification separation is carried out in the deethanizer 4. The light components at -45°C are distilled out from the top of the deethanizer 4, are cooled to -59°C in the top cooler 6, with partial liquefaction, and gas-liquid two-phase separation is carried out in the top separator 7. The liquid flows back to the upper part of the deethanizer 4, and the gas comes out from the top of the top separator 7 and enters the precooler 1, where it is rewarmed to normal temperature and sent to the device gas consumption point as fuel gas. The C3+ heavy components at 36°C come out from the bottom of the deethanizer 4. Part of them enters the bottom reboiler 5 and is heated to 38°C to vaporize the light components, which then return to the lower part of the deethanizer 4 for heat and mass transfer. The other part is sent to the light hydrocarbon storage tank as the product stable light hydrocarbon.

[0072] It should be noted that in the first cooling unit, the secondary cooler and the secondary cooler in the light hydrocarbon collection unit are the same device. The secondary cooler serves to exchange heat between the plastic pyrolysis gas in the light hydrocarbon collection unit and the first refrigerant in the first cooling unit.

[0073] It should be understood that the present utility model is described by some embodiments. Those skilled in the art will know that various changes or equivalent replacements can be made to these features and embodiments without departing from the spirit and scope of the present utility model. Additionally, under the teaching of the present utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present utility model. Therefore, the present utility model is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present utility model.

Claims

1. An apparatus for recovering light hydrocarbons from plastic pyrolysis gas, characterized in that, It includes a first cooling unit, a second cooling unit and a light hydrocarbon collection unit; Both the first cooling unit and the second cooling unit are heat exchange elements of the light hydrocarbon collection unit; The light hydrocarbon collection unit is used to collect light hydrocarbons from the raw material gas generated by plastic pyrolysis.

2. The device for recovering light hydrocarbons from plastic pyrolysis gas according to claim 1, characterized in that, The light hydrocarbon collection unit includes a pre-cooler, a secondary cooler, a de-ethanizer, a top cooler, a bottom reboiler and a top separator; Among them, the raw material inlet in the pre-cooler is connected to the plastic pyrolysis gas supply pipe, the raw material outlet in the pre-cooler is connected to the raw material inlet of the secondary cooler through a pipeline, and the raw material outlet of the secondary cooler is connected to the middle inlet of the de-ethanizer through a pipeline; the top outlet of the de-ethanizer is connected to the raw material inlet of the top cooler through a pipeline, the raw material outlet of the top cooler is connected to the inlet of the top separator through a pipeline, the top raw material outlet of the top separator is connected to the raw material inlet of the pre-cooler, and the bottom raw material outlet of the top separator is connected to the raw material inlet of the upper part of the de-ethanizer through a pipeline. The raw material outlet of the pre-cooler is connected to a gas transmission pipeline to send the reheated gas to the device gas use point as fuel gas at normal temperature; the bottom raw material outlet of the de-ethanizer is connected to the raw material inlet of the bottom reboiler, and the raw material outlet of the bottom reboiler is connected to a light hydrocarbon storage device.

3. The device for recovering light hydrocarbons from plastic pyrolysis gas according to claim 2, wherein In the light hydrocarbon collection unit: The pre-cooler is used to cool the plastic pyrolysis gas so that the temperature of the plastic pyrolysis gas at the raw material outlet of the pre-cooler is about 15°C; The secondary cooler is used to cool the plastic pyrolysis gas treated by the pre-cooler so that the temperature of the plastic pyrolysis gas at the raw material outlet of the secondary cooler is -35°C; The de-ethanizer is used to rectify and separate the plastic pyrolysis gas treated by the secondary cooler so that the -45°C light components are distilled out from the top outlet of the de-ethanizer and enter the top cooler, and the 36°C C3+ heavy components enter the bottom reboiler from the bottom outlet of the de-ethanizer; The top cooler is used to cool the -45°C light hydrocarbons distilled out from the top outlet of the de-ethanizer so that the light hydrocarbons are cooled to -59°C; The top separator is used to separate the -59°C light hydrocarbons into gas and liquid, and the separated gas is transported to the pre-cooler to be reheated to normal temperature and sent to the device gas use point as fuel gas, and the separated liquid flows back to the upper part of the de-ethanizer through a pipeline; The bottom reboiler is used to heat the 36°C C3+ heavy components entering it to 38°C to vaporize the light components and return them to the lower part of the de-ethanizer for heat and mass transfer, and another part of the light hydrocarbons is sent to the light hydrocarbon storage tank.

4. The device for recovering light hydrocarbons from plastic pyrolysis gas according to claim 3, wherein, The first cooling unit includes a refrigerant compressor A, a refrigerant cooler A, a bottom reboiler, a throttle valve A, and a secondary cooler; the refrigerant pipelines in the refrigerant compressor A, the refrigerant cooler, the bottom reboiler, the refrigerant throttle valve A, and the secondary cooler are sequentially connected to form a first refrigerant circuit.

5. The device for recovering light hydrocarbons from plastic pyrolysis gas according to claim 4, characterized in that, In the first cooling unit: The refrigerant compressor A is used to compress and transport the first refrigerant to the refrigerant cooler A; The refrigerant cooler A is used to cool and lower the temperature of the first refrigerant to 55°C; The bottom reboiler is used to cool the first refrigerant to a liquefied state at 45°C; The refrigerant throttle valve A is used to adjust and reduce the pressure of the first refrigerant circuit; The secondary cooler is used to provide cooling capacity for the secondary cooling of the plastic pyrolysis gas.

6. The device for recovering light hydrocarbons from plastic pyrolysis gas according to claim 5, characterized in that, The second cooling unit includes a refrigerant compressor B, a refrigerant cooler B, a refrigerant heat exchanger, a refrigerant throttle valve B, and a top cooler; the refrigerant pipelines in the refrigerant compressor B, the refrigerant cooler B, the refrigerant heat exchanger, the refrigerant throttle valve B, and the top cooler are sequentially connected to form a second refrigerant circuit.

7. The device for recovering light hydrocarbons from plastic pyrolysis gas according to claim 6, characterized in that, In the second cooling unit: The refrigerant compressor B is used to compress the second refrigerant and transport it to the refrigerant cooler B; The refrigerant cooler B is used to cool the temperature of the second refrigerant to 45°C; The refrigerant heat exchanger is used to condense the second refrigerant to a liquefied state at -60°C; The refrigerant throttle valve B is used to adjust and reduce the pressure of the second refrigerant circuit.

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