Light hydrocarbon conversion product fractionation system and method

Abstract

The invention discloses a light hydrocarbon conversion product fractionation system and method. The fractionation system comprises an absorption tower, an oil-gas separation tank, a desorption tower, a stabilization tower, a depentanizer and a compressor system; an inlet of the compressor system is connected with a light hydrocarbon conversion gas-phase reaction product inlet pipeline, the upper part of the absorption tower is connected with a light hydrocarbon conversion liquid-phase reaction product inlet pipeline, the top of the absorption tower is connected with an absorption tower top gas discharge pipeline, the absorption tower, the oil-gas separation tank, the desorption tower, the stabilization tower and the depentanizer are sequentially connected, and the top of the stabilization tower is connected with a liquefied gas discharge pipeline. A pipeline at the bottom of the stabilizing tower is divided into two paths, one path is connected with the upper part of the absorption tower, and the other path is connected with a C7 + fraction discharge pipeline; the top of the depentanizer is connected with a C5 fraction discharge pipeline, and the bottom of the depentanizer is connected with a C6 fraction discharge pipeline. The device construction cost and energy consumption are reduced, the processing cost can be reduced, the liquid yield is increased, and the aromatic hydrocarbon recovery rate is improved.

Description

Technical Field

[0001] The present invention belongs to the field of petrochemical or natural gas chemical industry, and relates to a light hydrocarbon conversion device and process. Specifically, it relates to a light hydrocarbon conversion product fractionation system and method. Background Art

[0002] Light hydrocarbon resources in China are relatively abundant, and these light hydrocarbons mainly include C4 - C7 components produced from refineries. Among them, C4 components mainly exist in liquefied petroleum gas products produced from refineries, and C5 - C7 components mainly exist in light naphtha fractions such as topped oil and raffinate oil produced from atmospheric distillation and catalytic reforming units. These can all be used as processing raw materials for light hydrocarbon conversion technology. In China where petroleum resources are relatively scarce, it is of great practical significance and good economic efficiency to use light hydrocarbon conversion technology to convert this part of relatively surplus light hydrocarbon resources into high - value - added BTX, propane, etc., and improve the efficiency of petrochemical enterprises. The process optimization of the device is particularly important, which can not only reduce production costs and improve economic benefits, but also save resources and reduce costs.

[0003] Currently, product separation in light hydrocarbon conversion devices generally uses an absorption - stabilization system for product separation, and product fractionation is carried out according to the different boiling points of each component. Although the technology is mature, this design not only requires a relatively high construction investment, but also has high energy consumption, and the processing cost has been staying high.

[0004] Utility Model CN 207243830U discloses a device for reducing consumption by side - line extraction of a stabilizing tower, which involves a liquid - collecting tank arranged at the upper part of the inner wall of the stabilizing tower. A side - output pipe is connected to the liquid - collecting tank, an electromagnetic valve is installed on the side - output pipe, the end of the side - output pipe is connected to a reactor pipeline, the end of the reactor pipeline is connected to a reboiler of a propane tower, and the outlet of the reboiler of the propane tower is connected to a cold - box pipeline. It mainly focuses on the internal structure of the stabilizing tower equipment. By side - line production, the amount of overhead product extraction is reduced to lower energy consumption, the processing capacity of the stabilizing tower is increased, the heat source of the propane tower is increased, and the processing cost is reduced. Among them, the side - line product is associated with the reaction pipeline and returns to the reaction system.

[0005] Utility Model CN 218932065U discloses a side - line extraction system for a stabilizing tower of a reforming device, which includes a stabilizing tower, an overhead product extraction and reflux system, a side - line extraction system, and a bottom circulation heating and extraction system; the extraction and reflux system includes an overhead air cooler, an overhead product heat exchanger, a stabilizing tower reflux drum, etc., mainly solving the problem that an additional de - pentane tower needs to be added in the existing reforming process to meet the process requirements, reducing the device construction cost and energy consumption in production. Summary of the Invention

[0006] In order to solve the problems of high construction investment, high energy consumption, and high processing cost of light hydrocarbon conversion devices, the present invention provides a light hydrocarbon conversion product fractionation system and method.

[0007] The light hydrocarbon conversion product fractionation system provided by the present invention includes an absorption tower, an oil-gas separation tank, a desorption tower, a stabilizer tower, a de-pentane tower and a compressor system. The compressor system is equipped with an inter-stage cooler; the upper part of the absorption tower is connected to the inlet pipeline of the light hydrocarbon conversion liquid-phase reaction product, the top of the absorption tower is connected to the absorption tower top gas discharge pipeline, the bottom of the absorption tower is connected to the upper part of the oil-gas separation tank through a pipeline, the top of the oil-gas separation tank is connected to the lower part of the absorption tower through a pipeline, the upper part of the oil-gas separation tank is connected to the outlet of the compressor system through a pipeline, and the inlet of the compressor system is connected to the inlet pipeline of the light hydrocarbon conversion gas-phase reaction product; the bottom of the oil-gas separation tank is connected to the middle part of the desorption tower through a pipeline, the bottom of the desorption tower is connected to the middle part of the stabilizer tower through a pipeline, the middle and upper part of the stabilizer tower is connected to the middle part of the de-pentane tower through a pipeline, the top of the stabilizer tower is connected to the liquefied gas discharge pipeline, and the pipeline at the bottom of the stabilizer tower is divided into two paths, one path is connected to the upper part of the absorption tower, and the other path is connected to the C7+ fraction discharge pipeline; the top of the de-pentane tower is connected to the C5 fraction discharge pipeline, and the bottom of the de-pentane tower is connected to the C6 fraction discharge pipeline.

[0008] As an improvement, the absorption tower top gas discharge pipeline is connected to the inlet of the absorption tower top cooler, the outlet of the absorption tower top cooler is connected to the middle part of the hydrogen-rich gas separation tank through a pipeline, the bottom of the hydrogen-rich gas separation tank is connected to the upper part of the stabilizer tower through a pipeline, and the top of the hydrogen-rich gas separation tank is connected to the hydrogen-rich gas discharge pipeline.

[0009] As another improvement, the top of the desorption tower is connected to the inlet of the inter-stage cooler of the compressor system through a pipeline.

[0010] The compressor system is set to two to three stages of compression, compressed to 1.5 - 3.0 MPa (gauge pressure).

[0011] The operating pressure at the top of the absorption tower is 1.3 - 2.8 MPa (gauge pressure). The top gas is condensed to 0 - 10 °C by the absorption tower top cooler and sent to the hydrogen-rich gas separation tank. The hydrogen-rich gas at the top of the tank is sent to the PSA unit, and the liquid phase at the bottom of the tank is sent to the stabilizer tower. The absorption tower top cooler uses chilled water or propane as the cold source.

[0012] The operating pressure at the top of the desorption tower is 1.2 - 1.8 MPa (gauge pressure), the operating temperature at the top of the tower is 45 - 55 °C, and the operating temperature at the bottom of the tower is 140 - 160 °C. The gas phase at the top of the desorption tower enters the inter-stage cooler of the compressor according to the pressure match, and the liquid at the bottom of the tower is sent to the stabilizer tower under the cascade control of liquid level and flow rate.

[0013] The operating pressure at the top of the stabilizer tower is 1.0 - 1.5 MPa (gauge pressure), the operating temperature at the top is 50 - 60 °C, the operating temperature at the bottom is 220 - 260 °C, and the bottom of the tower is heated by a reboiler furnace or heat transfer oil. The liquefied gas at the top of the tower is sent to the gas fractionation unit. The side draw outlet is located in the upper section of the tower body. The tower body is equipped with a sensitive plate or differential temperature control to regulate the side draw rate. The side draw product is sent to the de-pentane tower. Part of the C7+ fraction at the bottom of the tower returns to the absorption tower under the cascade control of liquid level and flow rate, and the other part is sent to the aromatics separation unit.

[0014] The operating pressure at the top of the de-pentane tower is 0.80 - 1.20 MPa (gauge pressure), the operating temperature at the top is 60 - 90 °C, the operating temperature at the bottom is 140 - 180 °C. The C5 fraction at the top of the tower is returned to the reaction system as recycle material, and the C6 fraction at the bottom of the tower is sent to the benzene extraction unit.

[0015] The present invention also provides a fractionation method for light hydrocarbon conversion products, comprising the following steps:

[0016] 1) The liquid-phase reaction product of light hydrocarbon conversion enters the absorption tower from the upper part of the absorption tower as an absorbent. The bottom stream of the absorption tower enters the oil-gas separation tank. The hydrogen-rich gas at the top of the absorption tower is subjected to gas-liquid separation after condensation. The separated hydrogen-rich gas is sent to the PSA unit, and the separated liquid phase is sent to the stabilizer tower.

[0017] 2) The gas-phase reaction product of light hydrocarbon conversion is compressed and mixed with the top gas of the desorption tower coming from the top of the desorption tower, and then enters the oil-gas separation tank after boosting the pressure. In the oil-gas separation tank, it is mixed with the stream coming from the bottom of the absorption tower and then subjected to gas-liquid separation. The gas at the top of the tank is sent to the lower part of the absorption tower for absorption by the absorbent, and the liquid at the bottom of the tank is sent to the desorption tower.

[0018] 3) The liquid at the bottom of the tank in step 2) is desorbed in the desorption tower. The top gas of the desorption tower is sent out from the top of the desorption tower, mixed with the gas-phase reaction product of light hydrocarbon conversion, and then enters the oil-gas separation tank after boosting the pressure. The liquid phase at the bottom of the desorption tower is sent to the stabilizer tower.

[0019] 4) In the stabilizer tower, the liquid phase separated in step 1) and the liquid phase at the bottom of the desorption tower are mixed and separated. The liquefied gas at the top of the stabilizer tower is sent to the gas fractionation unit. Part of the C7+ fraction at the bottom of the stabilizer tower returns to the absorption tower as a recycle absorbent, and the rest is sent to the aromatics separation unit as a product. The side draw product of the stabilizer tower is sent to the de-pentane tower.

[0020] 5) The side draw product of the stabilizer tower is further separated in the de-pentane tower. The C5 fraction at the top of the de-pentane tower is returned to the reaction system as recycle material, and the C6 fraction at the bottom of the de-pentane tower is sent to the benzene extraction unit.

[0021] The working process of the present invention is as follows:

[0022] (1) The light hydrocarbon conversion liquid-phase reaction product enters the absorption tower from the upper part of the absorption tower through the light hydrocarbon conversion liquid-phase reaction product inlet pipeline as an absorbent. The bottom stream of the absorption tower enters the oil-gas separation tank through a pipeline. The hydrogen-rich gas at the top of the absorption tower enters the absorber top cooler through a pipeline, is condensed, and then sent to the hydrogen-rich gas separation tank. The hydrogen-rich gas at the top of the tank is sent to the PSA unit through the hydrogen-rich gas discharge pipeline, and the liquid phase at the bottom of the tank is sent to the stabilizing tower.

[0023] (2) The light hydrocarbon conversion gas-phase reaction product enters the compressor system through the light hydrocarbon conversion gas-phase reaction product inlet pipeline, mixes with the desorption tower top gas before the inter-stage cooler sent from the top of the desorption tower to the compressor system, is boosted in pressure, and then enters the oil-gas separation tank. In the oil-gas separation tank, after mixing with the stream coming from the bottom of the absorption tower, gas-liquid separation is carried out. The gas at the top of the tank is sent into the absorption tower from the lower part (bottom) of the absorption tower, and the liquid at the bottom of the tank is sent to the desorption tower.

[0024] (3) The desorption tower top gas returns from the top of the desorption tower to before the inter-stage cooler of the compressor system, and the liquid phase at the bottom of the desorption tower is sent to the stabilizing tower.

[0025] (4) The liquefied gas at the top of the stabilizing tower is sent to the gas fractionation unit through the liquefied gas discharge pipeline. Part of the C7+ fraction at the bottom of the stabilizing tower is returned to the absorption tower as a circulating absorbent, and the rest is sent to the aromatics separation unit as a product through the C7+ fraction discharge pipeline. The side stream product of the stabilizing tower is sent to the de-pentanizing tower through a pipeline.

[0026] (5) The C5 fraction at the top of the de-pentanizing tower is returned to the reaction system as a circulating material through the C5 fraction discharge pipeline, and the C6 fraction at the bottom of the de-pentanizing tower is sent to the benzene extraction unit through the C6 fraction discharge pipeline.

[0027] The light hydrocarbon conversion technology in the present invention mainly refers to the light hydrocarbon aromatization technology, which uses various C4-C7 light hydrocarbons such as naphtha and / or liquefied gas as raw materials, and undergoes a series of complex reactions such as selective cracking of naphtha, olefin oligomerization and cyclization dehydrogenation, and hydrogen transfer on the aromatization catalyst to produce aromatics, propane and by-product hydrogen. That is, the composition of the light hydrocarbon conversion product is mainly: aromatics, propane and hydrogen.

[0028] The present invention has the following beneficial effects:

[0029] 1) By adding a pipeline connection from the upper section of the stabilizing tower body to the middle part of the de-pentanizing tower, four product separations are realized between the stabilizing tower and the de-pentanizing tower, reducing one fractionating tower compared with the conventional process, not only reducing the device construction cost and energy consumption, but also reducing the processing cost.

[0030] 2) By setting the absorber top cooler and the hydrogen-rich gas separation tank to cool and separate the gas-liquid of the absorber top gas, the aromatics content in the dry gas can be reduced. The liquid recovered at the bottom of the tank is recycled to the stabilizing tower, which can increase the liquid yield and improve the aromatics recovery rate.

[0031] 3) By connecting the top of the desorption tower to the inlet of the inter-stage cooler of the compressor system through a pipeline, the gas at the top of the desorption tower can be returned to the front of the inter-stage cooler of the compressor system according to pressure matching, which can reduce the operating pressure of the desorption tower, reduce the equipment investment and energy consumption of the desorption tower, and improve the economy of the device.

[0032] 4) The light hydrocarbon conversion product fractionation system of the present invention can be used in, but not limited to, light hydrocarbon to propane plants and light hydrocarbon aromatization plants. Among them, the light hydrocarbon to propane plant takes propane as the main product and by-produces aromatics; while the light hydrocarbon aromatization plant takes aromatics as the main product and by-produces propane. Brief Description of the Drawings

[0033] Figure 1 It is a schematic structural diagram of the present invention.

[0034] In the figure: 1 - inlet pipeline for light hydrocarbon conversion gas-phase reaction products, 2 - compressor system, 3 - oil-gas separation tank, 4 - absorption tower, 5 - inlet pipeline for light hydrocarbon conversion liquid-phase reaction products, 6 - desorption tower, 7 - absorption tower top cooler, 8 - hydrogen-rich gas separation tank, 9 - stabilizer tower, 10 - de-pentane tower, 11 - absorption tower top gas discharge pipeline, 12 - hydrogen-rich gas discharge pipeline, 13 - liquefied gas discharge pipeline, 14 - C5 fraction discharge pipeline, 15 - C6 fraction discharge pipeline, 16 - C7+ fraction discharge pipeline. Detailed Embodiments

[0035] The present invention will be further described below with reference to the drawings.

[0036] As Figure 1 shown, the light hydrocarbon conversion product fractionation system provided by the present invention includes an absorption tower 4, an oil-gas separation tank 3, a desorption tower 6, a stabilizer tower 9, a de-pentane tower 10, a compressor system 2, an absorption tower top cooler 7, and a hydrogen-rich gas separation tank 8. The compressor system 2 is provided with an inter-stage cooler (not shown in the figure); the upper part of the absorption tower 4 is connected to the inlet pipeline 5 for light hydrocarbon conversion liquid-phase reaction products. The top of the absorption tower is connected to the absorption tower top cooler 7 through the absorption tower top gas discharge pipeline 11. The absorption tower top cooler 7 is connected to the middle part of the hydrogen-rich gas separation tank 8 through a pipeline. The bottom of the hydrogen-rich gas separation tank 8 is connected to the upper part of the stabilizer tower 9 through a pipeline. The top of the hydrogen-rich gas separation tank 8 is connected to the hydrogen-rich gas discharge pipeline 12.

[0037] The bottom of the absorption tower 4 is connected to the upper part of the oil-gas separation tank 3 through a pipeline. The top of the oil-gas separation tank 3 is connected to the lower part of the absorption tower 4 through a pipeline. The upper part of the oil-gas separation tank 3 is connected to the outlet of the compressor system 2 through a pipeline. The inlet of the compressor system 2 is connected to the light hydrocarbon conversion gas-phase reaction product inlet pipeline 1. The bottom of the oil-gas separation tank 3 is connected to the middle part of the desorption tower 6 through a pipeline. The bottom of the desorption tower 6 is connected to the middle part of the stabilizer tower 9 through a pipeline. The top of the desorption tower 6 is connected to the inlet of the inter-stage cooler of the compressor system 2 through a pipeline.

[0038] The upper part of the stabilizer tower 9 is connected to the middle part of the de-pentane tower 10 through a pipeline. The top of the stabilizer tower 9 is connected to the liquefied gas discharge pipeline 13. The pipeline at the bottom of the stabilizer tower 9 is divided into two paths. One path is connected to the upper part of the absorption tower 4, and the other path is connected to the C7+ fraction discharge pipeline 16. The top of the de-pentane tower 10 is connected to the C5 fraction discharge pipeline 14, and the bottom of the de-pentane tower is connected to the C6 fraction discharge pipeline 15.

[0039] The working process of the present invention is as follows:

[0040] (1) The light hydrocarbon conversion liquid-phase reaction product enters the absorption tower 4 from the upper part of the absorption tower 4 as an absorbent through the light hydrocarbon conversion liquid-phase reaction product inlet pipeline 5. The bottom stream of the absorption tower 4 enters the oil-gas separation tank 3 through a pipeline. The hydrogen-rich gas at the top of the absorption tower 4 enters the absorption tower top cooler 7 through the absorption tower top gas discharge pipeline 11, is condensed and then sent to the hydrogen-rich gas separation tank 8. The hydrogen-rich gas at the top of the tank is sent to the PSA unit through the hydrogen-rich gas discharge pipeline 12, and the liquid phase at the bottom of the tank is sent to the stabilizer tower 9.

[0041] (2) The light hydrocarbon conversion gas-phase reaction product enters the compressor system 2 through the light hydrocarbon conversion gas-phase reaction product inlet pipeline 1, is mixed with the desorption tower top gas sent to the front of the inter-stage cooler of the compressor system 2 from the top of the desorption tower 6, is boosted in pressure and then enters the oil-gas separation tank 3. In the oil-gas separation tank 3, it is mixed with the stream coming from the bottom of the absorption tower 4 and then undergoes gas-liquid separation. The gas at the top of the tank is sent into the absorption tower 4 from the lower part (bottom) of the absorption tower 4, and the liquid at the bottom of the tank is sent to the desorption tower 6.

[0042] (3) The desorption tower top gas returns from the top of the desorption tower 6 to the front of the inter-stage cooler of the compressor system 2, and the liquid phase at the bottom of the desorption tower 6 is sent to the stabilizer tower 9.

[0043] (4) The liquefied gas at the top of the stabilizer tower 9 is sent to the gas fractionation unit through the liquefied gas discharge pipeline 13. A part of the C7+ fraction at the bottom of the stabilizer tower 9 is returned to the absorption tower 4 as a circulating absorbent, and the rest is sent to the aromatics separation unit as a product through the C7+ fraction discharge pipeline 16. The side stream product of the stabilizer tower 9 is sent to the de-pentane tower 10 through a pipeline.

[0044] (5) The C5 fraction at the top of the de-pentane tower 10 is returned to the reaction system as recycled material through the C5 fraction discharge pipeline 14, and the C6 fraction at the bottom of the de-pentane tower 10 is sent to the benzene extraction unit through the C6 fraction discharge pipeline 15.

[0045] The above are only typical embodiments of the present invention, and there is no formal limitation on the present invention. Any person skilled in the art, without departing from the technical solution of the present invention, the changes or modifications made using the above content should be regarded as equivalent examples of equivalent changes. All content that does not depart from the technical solution of the present invention, any equivalent changes made to the above embodiments based on the technical essence of the present invention, all fall within the protection scope of the technical solution of the present invention.

Claims

1. A light hydrocarbon conversion product fractionation system, characterized in that: It includes an absorption tower, an oil-gas separation tank, a desorption tower, a stabilizer column, a de-pentane tower and a compressor system. The compressor system is equipped with an inter-stage cooler. The upper part of the absorption tower is connected to the inlet pipeline of the light hydrocarbon conversion liquid-phase reaction product. The top of the absorption tower is connected to the absorption tower top gas discharge pipeline. The bottom of the absorption tower is connected to the upper part of the oil-gas separation tank through a pipeline. The top of the oil-gas separation tank is connected to the lower part of the absorption tower through a pipeline. The upper part of the oil-gas separation tank is connected to the outlet of the compressor system. The inlet of the compressor system is connected to the inlet pipeline of the light hydrocarbon conversion gas-phase reaction product. The bottom of the oil-gas separation tank is connected to the middle part of the desorption tower through a pipeline. The bottom of the desorption tower is connected to the middle part of the stabilizer column through a pipeline. The middle and upper part of the stabilizer column is connected to the middle part of the de-pentane tower through a pipeline. The top of the stabilizer column is connected to the liquefied gas discharge pipeline. The pipeline at the bottom of the stabilizer column is divided into two paths. One path is connected to the upper part of the absorption tower, and the other path is connected to the C7+ fraction discharge pipeline. The top of the de-pentane tower is connected to the C5 fraction discharge pipeline, and the bottom of the de-pentane tower is connected to the C6 fraction discharge pipeline.

2. The light hydrocarbon conversion product fractionation system according to claim 1, characterized in that: The absorption tower top gas discharge pipeline is connected to the inlet of the absorption tower top cooler. The outlet of the absorption tower top cooler is connected to the middle part of the hydrogen-rich gas separation tank through a pipeline. The bottom of the hydrogen-rich gas separation tank is connected to the upper part of the stabilizer column through a pipeline. The top of the hydrogen-rich gas separation tank is connected to the hydrogen-rich gas discharge pipeline.

3. The light hydrocarbon conversion product fractionation system according to claim 1, characterized in that: The top of the desorption tower is connected to the inlet of the inter-stage cooler of the compressor system through a pipeline.

4. The light hydrocarbon conversion product fractionation system according to claim 2, characterized in that: The top of the desorption tower is connected to the inlet of the inter-stage cooler of the compressor system through a pipeline.

5. The light hydrocarbon conversion product fractionation system according to any one of claims 1 to 4, characterized in that: The compressor system is set to two to three-stage compression.

6. A light hydrocarbon conversion product fractionation method, characterized in that, It includes the following steps: 1) The light hydrocarbon conversion liquid-phase reaction product enters the absorption tower from the upper part of the absorption tower as an absorbent. The bottom stream of the absorption tower enters the oil-gas separation tank. After the hydrogen-rich gas at the top of the absorption tower is condensed for gas-liquid separation, the separated hydrogen-rich gas is sent to the PSA unit, and the separated liquid phase is sent to the stabilizer column. 2) The light hydrocarbon conversion gas-phase reaction product is compressed and then mixed with the desorption tower top gas coming from the top of the desorption tower to increase the pressure and then enters the oil-gas separation tank. In the oil-gas separation tank, it is mixed with the stream coming from the bottom of the absorption tower and then undergoes gas-liquid separation. The gas at the top of the tank is sent into the absorption tower from the lower part of the absorption tower for the absorbent to absorb, and the liquid at the bottom of the tank is sent to the desorption tower. 3) The liquid at the bottom of the tank in step 2) is desorbed in the desorption tower. The desorption tower top gas is sent out from the top of the desorption tower, mixed with the light hydrocarbon conversion gas-phase reaction product to increase the pressure and then enters the oil-gas separation tank. The liquid phase at the bottom of the desorption tower is sent to the stabilizer column. 4) In the stabilizer column, the liquid phase separated in step 1) and the liquid phase at the bottom of the desorption tower are mixed and separated. The liquefied gas at the top of the stabilizer column is sent to the gas fractionation unit. A part of the C7+ fraction at the bottom of the stabilizer column is returned to the absorption tower as a circulating absorbent, and the rest is sent to the aromatics separation unit as a product. The side stream product of the stabilizer column is sent to the de-pentane tower. 5) The side stream product of the stabilizer column is further separated in the de-pentane tower. The C5 fraction at the top of the de-pentane tower is returned to the reaction system as a circulating material, and the C6 fraction at the bottom of the de-pentane tower is sent to the benzene extraction unit.

7. The light hydrocarbon conversion product fractionation method according to claim 6, wherein: The operating pressure at the top of the absorption tower is 1.3 - 2.8 MPa. The hydrogen-rich gas at the top of the absorption tower is condensed to 0 - 10 °C for gas-liquid separation, and the cooling source for condensation is chilled water or propane; The operating pressure at the top of the desorption tower is 1.2 - 1.8 MPa, the operating temperature at the top is 45 - 55 °C, and the operating temperature at the bottom is 140 - 160 °C. Before the gas phase at the top of the desorption tower is mixed with the reaction product of the light hydrocarbon conversion gas phase for pressure boosting according to pressure matching, the liquid at the bottom of the tower is sent to the stabilizer under the cascade control of liquid level and flow rate; The operating pressure at the top of the stabilizer is 1.0 - 1.5 MPa, the operating temperature at the top is 50 - 60 °C, and the operating temperature at the bottom is 220 - 260 °C. The bottom of the tower is heated by a reboiler furnace or heat transfer oil; A part of the C7+ fraction at the bottom of the tower is returned to the absorption tower under the cascade control of liquid level and flow rate, and the other part is sent to the aromatics separation unit; The operating pressure at the top of the de-pentane tower is 0.80 - 1.20 MPa, the operating temperature at the top is 60 - 90 °C, and the operating temperature at the bottom is 140 - 180 °C.

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