Absorption stabilization system taking stabilized gasoline as re-absorbent in catalytic cracking device and rectification method

Abstract

The invention belongs to the field of petrochemical industry, and discloses an absorption stabilization system taking stabilized gasoline as a re-absorbent in a catalytic cracking device and a rectification method. The absorption stabilization system is improved on the basis of an existing absorption stabilization system, the tower bottom of a stabilization tower is connected with the tower top of a re-absorption tower through a pipeline, the tower bottom of the re-absorption tower is connected with a pipeline between a gas-rich air cooler and a water cooler through a pipeline, and a water cooler and a third-stage gas-rich compressor are arranged between a second-stage gas-rich compressor and the air cooler. A pipeline for connecting the second-stage rich gas compressor and the water cooler is connected with the top of the desorption tower through a pipeline; and a pipeline for connecting the third-stage rich gas compressor and the air cooler is connected with the acidic water outlet through a pipeline. The system adopts stable gasoline as a re-absorption tower absorbent, a supplementary absorbent of the absorption tower is shut down, bottom oil of the absorption tower does not enter a condensation oil tank, and return of rich diesel oil to the tower is canceled. The invention also discloses a rectification method. The absorption effect is enhanced, the diesel oil process is simplified, and the energy consumption and the cost are reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of petroleum processing, and particularly relates to an absorption and stabilization system and a rectification method in which poor diesel is stopped from being used in a catalytic cracking device and stabilized gasoline is used as a reabsorber. BACKGROUND

[0002] A fluid catalytic cracking unit (FCCU) is a very important petroleum processing unit. It takes heavy distillate oil, such as wax oil, as raw material, and under the action of catalyst at a certain temperature (about 500 DEG C) and pressure (0.2-0.4 MPa), the heavy distillate oil is cracked into light oil, such as dry gas, liquefied petroleum gas (LPG), gasoline and diesel. The unit is composed of reaction-regeneration, flue gas energy recovery, main fractionating column and absorption stabilization. The task of the reaction-regeneration system is to crack heavy oil and complete catalyst circulation and regeneration; the task of the main fractionating column is to separate reaction oil gas into rich gas, crude gasoline, diesel and oil slurry; the absorption stabilization system is composed of absorption tower, reabsorption tower, desorption tower and stabilization tower, and with the help of poor diesel from the main fractionating column, the compressed rich gas and crude gasoline from the top of the main fractionating column are separated into product dry gas, LPG and stabilized gasoline by using absorption, desorption and rectification processes.

[0003] It can be seen that the absorption stabilization is a unit for obtaining qualified product dry gas, LPG and stabilized gasoline. Since the content of ≥C3 components (components with carbon number ≥3) in the dry gas needs to be controlled to be ≤3% v, a reabsorption tower is additionally provided in addition to the absorption tower. The absorption tower takes crude gasoline and circulating stabilized gasoline (also called "supplementary absorbent") as absorbent, and the reabsorption tower takes poor diesel from the main fractionating column as absorbent. After absorbing a certain amount of gaseous components (mainly C3-C4), the rich diesel at the bottom of the reabsorption tower is returned to the main fractionating column for cracking. The process has the following problems: 1) the temperature of the rich diesel returned to the tower is low, which reduces the heat removal of the main fractionating column; 2) the processing capacity of the main fractionating column is increased; 3) the diesel cycle across the main fractionating column and the absorption stabilization system is set, which complicates the process and heat exchange process; 4) the diesel fraction is C 11 ~C 22 components, and the difference in carbon atom number from the C3-C4 gaseous components is large, so the absorption capacity is weak.

[0004] How to improve the absorption capacity and eliminate the diesel cycle across the systems is one of the problems that people need to solve. SUMMARY

[0005] In order to solve the problems of the existing catalytic cracking device, such as the decrease of reflux heat extraction in the main fractionating tower, the increase of processing capacity, the complexity of diesel process and heat exchange process, and the poor absorption effect of lean diesel, an absorption and stabilization system and a rectification method for a catalytic cracking device are provided.

[0006] The present application is realized by the following technical solutions: An absorption and stabilization system for a catalytic cracking device, comprising an absorption tower, a reabsorption tower, a desorption tower, and a stabilization tower. The top of the absorption tower is connected to the bottom of the reabsorption tower through a pipeline, the bottom of the absorption tower is connected to the top of the desorption tower through a pipeline, and a pressure reducing valve is arranged on the pipeline connecting the bottom of the absorption tower and the top of the desorption tower. The bottom of the desorption tower is connected to a desorption tower bottom reboiler and a stabilization tower feed heat exchanger through a pipeline, the desorption tower bottom reboiler is connected to the bottom of the desorption tower through a pipeline to form a reflux, and the stabilization tower feed heat exchanger is connected to the stabilization tower through a pipeline. The bottom of the stabilization tower is connected to the stabilization tower feed heat exchanger and a stabilization tower bottom reboiler through a pipeline, the stabilization tower feed heat exchanger is connected to the desorption tower intermediate reboiler and a stabilization gasoline three-time hot water heat exchanger through a pipeline, the stabilization gasoline three-time hot water heat exchanger is connected to a stabilization gasoline collection or treatment device and an absorption tower supplementary absorption agent circulating water cooler through a pipeline, a supplementary absorption agent pump is arranged on the pipeline connecting the stabilization gasoline three-time hot water heat exchanger and the absorption tower supplementary absorption agent circulating water cooler, the absorption tower supplementary absorption agent circulating water cooler is connected to the top of the reabsorption tower through a pipeline, and the absorption tower supplementary absorption agent circulating water cooler is connected to the first plate feed position of the top of the reabsorption tower through a pipeline. The top of the stabilizing tower is connected with a stabilizing tower top gas air cooling device, a stabilizing tower top gas circulating water cooler, a stabilizing tower top liquid separation tank, a stabilizing tower top product liquefied gas and a cold reflux pump in sequence through pipelines.

[0007] The upper part of the absorption tower is provided with a first reflux, and the lower part is provided with a second reflux; the liquid outlet of the first reflux is connected with an absorption tower first intermediate reflux pump, an absorption tower first circulating water cooler and a liquid inlet in sequence through pipelines; the liquid outlet of the second reflux is connected with an absorption tower second intermediate reflux pump, an absorption tower second intermediate circulating water cooler and a liquid inlet in sequence through pipelines.

[0008] The system comprises a secondary rich gas compressor, which is connected with a tertiary rich gas compressor front circulating water cooler through a pipeline, and the pipeline is a compressed rich gas pipeline.

[0009] The bottom of the desorption tower is also connected with a desorption tower bottom first secondary heat source reboiler through a pipeline, and the desorption tower bottom first secondary heat source reboiler is connected with the bottom of the desorption tower through a pipeline to form a reflux. The desorption tower bottom first secondary heat source reboiler is provided with heat source by the fraction in the middle part of the main fractionating tower.

[0010] The stabilizing tower bottom reboiler is provided with heat source by the fraction in the middle part of the main fractionating tower. The fraction in the middle part of the main fractionating tower provides heat through reflux. A valve is arranged on the reflux pipeline.

[0011] A method for rectification of an absorption stabilizing system using stabilized gasoline as a reabsorbing agent in a catalytic cracking device, comprising the following steps: 1) crude gasoline enters the absorption tower, and after treatment of the absorption tower, lean gas enters the bottom of the reabsorption tower from the top of the absorption tower; the absorption tower bottom oil enters the top of the desorption tower through a desorption tower bottom oil inlet decompression valve, and after treatment of the desorption tower, the desorption tower top gas is combined with compressed rich gas, then water-cooled, compressed by a tertiary rich gas compressor, mixed with acidic water to obtain a mixed liquid; the mixed liquid is air-cooled, then mixed with the reabsorption tower bottom oil, water-cooled, and enters a condensed oil tank together, and after expansion flash evaporation through the condensed oil tank, the dissolved gas component overflows into the absorption tower bottom, and the condensed oil enters the desorption tower through a desorption tower feed decompression valve; 2) a part of the desorption tower bottom oil is heated by steam in a desorption tower bottom reboiler to provide heat source, and after partial vaporization, the desorption tower bottom oil is refluxed to the desorption tower, and a part of the desorption tower bottom oil is heat-exchanged with the stabilized tower bottom oil in a stabilized tower feed heat exchanger, and then enters the stabilized tower after being heated; 3) A part of the stable column bottom oil exchanges heat with the desorption column bottom oil, the fraction from the middle of the desorption column and hot water in turn, and after cooling, stable gasoline is obtained; a part of the stable gasoline enters the top of the resorption column as a resorption agent, and another part of the stable gasoline enters the stable gasoline collecting device; A part of the stable column bottom oil exchanges heat with the fraction from the middle reflux device of the main fractionating column through the stable column bottom reboiler, and after heating, it returns to the bottom of the stable column; 4) The stable column top gas is air-cooled, water-cooled and then transported to the stable column top liquid separator to obtain liquefied gas; a part of the liquefied gas is transported to the top reflux of the stable column, and a part of the liquefied gas is transported to the collecting device; The resorption column top gas is dry gas.

[0012] The desorption column top gas in step 1 is combined with compressed rich gas, wherein the compressed rich gas refers to the rich gas compressed by the secondary rich gas compressor.

[0013] In step 1, the tertiary rich gas compressor is compressed, and the pressure of the outlet after compression is 1.5-1.7 MPa.

[0014] In step 3, a part of the stable column bottom oil exchanges heat with the desorption column bottom oil, the fraction from the middle of the desorption column and hot water in turn, which means that the stable column bottom oil exchanges heat with the desorption column bottom oil in the stable column feed heat exchanger, then exchanges heat with the fraction from the middle of the desorption column in the desorption column intermediate reboiler, and finally exchanges heat with hot water in the stable gasoline three-time-hot water heat exchanger.

[0015] A part of the stable gasoline enters the top of the resorption column, which means that a part of the stable gasoline is transported to the absorption column supplemental resorption agent circulating water cooler for cooling, and then transported to the top of the resorption column by the supplemental resorption agent pump.

[0016] A part of the desorption column bottom oil exchanges heat with the fraction from the middle reflux device of the main fractionating column through the desorption column bottom one-two secondary heat source reboiler, and after heating, it returns to the bottom of the desorption column.

[0017] The system and process of the present application reduce the rich diesel oil-diesel oil heat exchange process and the rich diesel oil return to the main fractionating column process; and about 40℃ stable gasoline from the bottom of the stable column, after heat exchange and circulating water cooling, is divided into two parts, one part replaces the lean diesel oil and is injected into the resorption column from the first block plate feed position as a resorption agent, and the other part is a product stable gasoline, which reduces the supplemental resorption agent process of the absorption column. The benefit is improved.

[0018] The present application does not send the oil at the bottom of the absorption tower to the condensed oil tank by pump pressure, but enters the desorption tower from the first tower plate through a pressure reducing valve; moreover, the stable gasoline is used as the reabsorbing agent in the reabsorption tower, the circulating stable gasoline is used to supplement the absorbing agent in the absorption tower, the third-stage rich gas compressor (or the current two-stage compressor is changed into a three-stage compressor) is set, the pressure of the rich gas is increased from the current two-stage outlet about 1.0 MPa (gauge pressure, the same below) to the three-stage outlet about 1.6 MPa, the operating pressure of the absorption tower and the reabsorption tower is increased from the current about 1.0 MPa to about 1.6 MPa, the desorption tower and the stabilizing tower keep the original operating pressure about 1.0 MPa unchanged, the condensed oil and the absorbing tower bottom oil pressure reducing valves are set, and the absorbing tower bottom oil pump is stopped.

[0019] In order to reduce the reboiling steam consumption of the process desorption tower, a secondary heat source reboiler is additionally arranged at the bottom of the desorption tower.

[0020] The stable gasoline in the present application is mainly C5~C 11 components.

[0021] Compared with the prior art, the present application has the following advantages and beneficial effects: 1) The present application does not use the lean diesel oil as the reabsorbing agent, the rich diesel oil is stopped, the heat output in the main fractionating tower is increased, the processing capacity is reduced, and the diesel oil process is simplified; 2) The present application stops the circulating stable gasoline supplementing absorbing agent in the absorption tower, and simplifies the absorption tower process; 3) The present application directly injects the absorbing tower bottom oil into the first plate of the desorption tower, reduces the cooling load of the condensed oil tank and the reboiling load of the desorption tower; 4) The present application does not change the material balance and product quality of the device, is suitable for old device modification and new device construction; and can be applied to the absorption and stabilization system of the delayed coking device.

[0022] In summary, the present application simplifies the process, reduces the load, reduces the energy consumption, improves the benefit, and reduces the cost. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1Figure 1 is a schematic diagram of an absorption-stabilization system of the prior art; 1 - secondary rich gas compressor, 2 - rich gas air cooler, 3 - condensing oil tank feed circulating water cooler, 4 - condensing oil tank, 5 - absorption tower, 6 - absorption tower first intermediate reflux pump, 7 - absorption tower first circulating water cooler, 8 - absorption tower second intermediate reflux pump, 9 - absorption tower second intermediate circulating water cooler, 10 - absorption tower bottom oil pump, 11 - reabsorption tower, 12 - desorption tower, 13 - desorption tower bottom reboiler, 14 - stabilized gasoline third hot water heat exchanger, 15 - desorption tower intermediate reboiler, 16 - deethanized gasoline pump, 17 - stabilization tower feed heat exchanger, 18 - absorption tower supplemental absorbent circulating water cooler, 19 - supplemental absorbent pump, 20 - stabilization tower, 21 - stabilization tower overhead gas air cooler, 22 - stabilization tower overhead gas circulating water cooler, 23 - stabilization tower overhead product liquid gas and cold reflux pump, 24 - stabilization tower bottom reboiler, 25 - desorption tower feed pump; Figure 2 Figure 2 is a schematic diagram of an absorption-stabilization system of the present application using stabilized gasoline as a reabsorbent in a catalytic cracking unit; 1 - secondary rich gas compressor, 2 - rich gas air cooler, 3 - condensing oil tank feed circulating water cooler, 4 - condensing oil tank, 5 - absorption tower, 6 - absorption tower first intermediate reflux pump, 7 - absorption tower first circulating water cooler, 8 - absorption tower second intermediate reflux pump, 9 - absorption tower second intermediate circulating water cooler, 10 - absorption tower bottom oil feed desorption tower pressure reducing valve, 11 - reabsorption tower, 12 - desorption tower, 13 - desorption tower bottom reboiler, 14 - stabilized gasoline third hot water heat exchanger, 15 - desorption tower intermediate reboiler, 16 - deethanized gasoline pump, 17 - stabilization tower feed heat exchanger, 18 - absorption tower supplemental absorbent circulating water cooler, 19 - supplemental absorbent pump, 20 - stabilization tower, 21 - stabilization tower overhead gas air cooler, 22 - stabilization tower overhead gas circulating water cooler, 23 - stabilization tower overhead product liquid gas and cold reflux pump, 24 - stabilization tower bottom reboiler, 25 - desorption tower feed pressure reducing valve, 26 - tertiary rich gas compressor, 27 - tertiary rich gas compressor front circulating water cooler; Figure 3Figure 1 is a schematic diagram of an absorption-stabilization system in a catalytic cracking unit of Example 2 using stabilized gasoline as a reabsorbent; 1 - secondary rich gas compressor, 2 - rich gas air cooler, 3 - condensed oil tank feed circulating water cooler, 4 - condensed oil tank, 5 - absorption tower, 6 - absorption tower first intermediate reflux pump, 7 - absorption tower first circulating water cooler, 8 - absorption tower second intermediate reflux pump, 9 - absorption tower second intermediate circulating water cooler, 10 - absorption tower bottom oil into desorption tower pressure reducing valve, 11 - reabsorption tower, 12 - desorption tower, 13 - desorption tower bottom reboiler, 14 - stabilized gasoline third hot water heat exchanger, 15 - desorption tower intermediate reboiler, 16 - deethanized gasoline pump, 17 - stabilized tower feed heat exchanger, 18 - absorption tower supplemental absorbent circulating water cooler, 19 - supplemental absorbent pump, 20 - stabilized tower, 21 - stabilized tower overhead gas air cooler, 22 - stabilized tower overhead gas circulating water cooler, 23 - stabilized tower overhead liquid separator tank, 24 - stabilized tower overhead product liquefied gas and cold reflux pump, 25 - stabilized tower bottom reboiler, 26 - desorption tower feed pressure reducing valve, 27 - tertiary rich gas compressor, 28 - tertiary rich gas compressor front circulating water cooler; 29 - desorption tower bottom first and second heat source reboiler. DETAILED DESCRIPTION

[0024] The application will be described in greater detail below with reference to the embodiments and drawings, but the embodiments of the application are not limited thereto.

[0025] Figure 1 is a schematic diagram of an absorption-stabilization system in a catalytic cracking unit of Example 2 using stabilized gasoline as a reabsorbent; 1 - secondary rich gas compressor, 2 - rich gas air cooler, 3 - condensed oil tank feed circulating water cooler, 4 - condensed oil tank, 5 - absorption tower, 6 - absorption tower first intermediate reflux pump, 7 - absorption tower first circulating water cooler, 8 - absorption tower second intermediate reflux pump, 9 - absorption tower second intermediate circulating water cooler, 10 - absorption tower bottom oil into desorption tower pressure reducing valve, 11 - reabsorption tower, 12 - desorption tower, 13 - desorption tower bottom reboiler, 14 - stabilized gasoline third hot water heat exchanger, 15 - desorption tower intermediate reboiler, 16 - deethanized gasoline pump, 17 - stabilized tower feed heat exchanger, 18 - absorption tower supplemental absorbent circulating water cooler, 19 - supplemental absorbent pump, 20 - stabilized tower, 21 - stabilized tower overhead gas air cooler, 22 - stabilized tower overhead gas circulating water cooler, 23 - stabilized tower overhead liquid separator tank, 24 - stabilized tower overhead product liquefied gas and cold reflux pump, 25 - stabilized tower bottom reboiler, 26 - desorption tower feed pressure reducing valve, 27 - tertiary rich gas compressor, 28 - tertiary rich gas compressor front circulating water cooler; 29 - desorption tower bottom first and second heat source reboiler. Figure 2 or 3; including absorption tower 5, reabsorption tower 11, desorption tower 12, and stabilized tower 20; The absorption tower 5 top is connected to the bottom of the reabsorption tower 11 through a pipeline, and the bottom of the absorption tower 5 is connected to the top of the desorption tower 12 through a pipeline, and an absorption tower bottom oil into desorption tower pressure reducing valve 10 is arranged on the connecting pipeline; the desorption tower 12 top is connected to the compressed rich gas pipeline through a pipeline, that is, the pipeline of the desorption tower 12 top is merged with the compressed rich gas pipeline, and the merged pipeline is sequentially connected to the tertiary rich gas compressor front circulating water cooler 28 and the tertiary rich gas compressor 27; the tertiary rich gas compressor 27 is sequentially connected to the rich gas air cooler device 2, the condensed oil tank feed circulating water cooler 3, and the condensed oil tank 4 through a pipeline; the pipeline connecting the tertiary rich gas compressor 27 and the rich gas air cooler device 2 is merged with the sour water pipeline, and the pipeline connecting the rich gas air cooler device 2 and the condensed oil tank feed circulating water cooler 3 is merged with the pipeline from the bottom of the reabsorption tower 11; the condensed oil tank 4 is respectively connected to the bottom of the absorption tower 5 and the top of the desorption tower 12 through a pipeline, and a desorption tower feed pressure reducing valve 26 is arranged on the pipeline connecting the condensed oil tank 4 and the top of the desorption tower 12; The bottom of the desorption tower 12 is connected to the bottom reboiler 13 and the feed heat exchanger of the stabilizer tower via pipelines. The bottom reboiler 13 is connected to the bottom of the desorption tower 12 via a pipeline to form a reflux. The feed heat exchanger 17 of the stabilizer tower is connected to the stabilizer tower via a pipeline. An ethane removal gasoline pump 16 is installed on the pipeline connecting the bottom of the desorption tower 12 and the feed heat exchanger 17 of the stabilizer tower. A reflux line is provided on the outer side of the middle part of the desorption tower 12. That is, the liquid outlet in the middle part of the desorption tower 12 is connected to the intermediate reboiler 15 of the desorption tower via a pipeline. The intermediate reboiler 15 of the desorption tower is connected to the liquid inlet in the lower part of the desorption tower 12 via a pipeline. The bottom of the stabilization tower 20 is connected to the stabilization tower feed heat exchanger 17 and the stabilization tower bottom reboiler 25 via pipelines. The stabilization tower feed heat exchanger 17 is connected to the desorption tower intermediate reboiler 15 and the stabilized gasoline tertiary-hot water heat exchanger 14 via pipelines. The stabilized gasoline tertiary-hot water heat exchanger 14 is connected to the stabilized gasoline collection or treatment device and the absorbent supplement circulating water cooler 18 via pipelines. A supplementary absorbent pump 19 is installed on the pipeline connecting the stabilized gasoline tertiary-hot water heat exchanger 14 and the absorbent supplement circulating water cooler 18. The absorbent supplement circulating water cooler 18 is connected to the top of the reabsorption tower 11 via a pipeline. The absorbent supplement circulating water cooler 18 is connected to the feed position of the first plate at the top of the reabsorption tower 11 via a pipeline. The top of the reabsorption tower 11 is provided with a dry gas outlet. The top of the stabilizer tower 20 is connected in sequence via pipes to the stabilizer tower top air cooler 21, the stabilizer tower top air circulating water cooler 22, the stabilizer tower top liquid separator 23, the stabilizer tower top product liquefied gas and the cold reflux pump 24. The stabilizer tower top product liquefied gas and the cold reflux pump 24 are connected via pipes to the top of the stabilizer tower 20 and the liquefied gas collection device, respectively.

[0026] The absorption tower 5 has a No. 1 reflux in the upper part and a No. 2 reflux in the lower part. The outlet of the No. 1 reflux is connected to the first intermediate reflux pump 6, the first circulating water cooler 7, and the No. 1 inlet of the absorption tower via pipelines. The outlet of the No. 2 reflux is connected to the second intermediate reflux pump 8, the second intermediate circulating water cooler 9, and the No. 2 inlet of the absorption tower via pipelines. The No. 1 outlet is higher than the No. 1 inlet; the No. 2 outlet is higher than the No. 2 inlet.

[0027] The system includes a two-stage rich gas compressor 1, which is connected to the pre-circulating water cooler 28 of the three-stage rich gas compressor via a pipeline. This pipeline is the rich gas pipeline after compression.

[0028] The bottom of the desorption tower 12 is also connected to the secondary heat source reboiler 29 at the bottom of the desorption tower via a pipeline. The secondary heat source reboiler 29 at the bottom of the desorption tower is connected to the bottom of the desorption tower 12 via a pipeline to form a reflux. The heat source for the secondary heat source reboiler 29 at the bottom of the desorption tower is provided by the distillate from the middle of the main fractionation tower as the heat source for the bottom liquid of the desorption tower.

[0029] The stabilizer reboiler 25 uses the fraction from the middle of the main fractionation column as a heat source to stabilize the bottom liquid. The fraction from the middle of the main fractionation column is heated via reflux. A valve is installed on the reflux line.

[0030] In the system, the pipe at the top of the desorption tower 12 merges with the compressed rich gas pipe. The merged pipe is then connected in sequence to the circulating water cooler 28 before the three-stage rich gas compressor and the three-stage rich gas compressor 27. Specifically, the top of the desorption tower 12 is connected to the circulating water cooler 28 before the three-stage rich gas compressor through a pipe, and the two-stage rich gas compressor is connected to the circulating water cooler 28 before the three-stage rich gas compressor through a pipe.

[0031] The pipe connecting the three-stage rich gas compressor 27 and the rich gas air-cooling device 2 merges with the acidic water pipe. The pipe connecting the rich gas air-cooling device 2 and the condensate tank feed circulating water cooler 3 merges with the pipe from the bottom of the reabsorption tower 11. Specifically, the three-stage rich gas compressor 27 is connected to the rich gas air-cooling device 2 through a pipe, the acidic water outlet is connected to the rich gas air-cooling device 2 through a pipe, the rich gas air-cooling device 2 is connected to the condensate tank feed circulating water cooler 3 through a pipe, and the bottom of the reabsorption tower 11 is connected to the condensate tank feed circulating water cooler 3 through a pipe.

[0032] A method for distillation in an absorption stabilization system using stabilized gasoline as a reabsorbent in a catalytic cracking unit includes the following steps: 1) Crude gasoline enters the absorption tower. After being processed by the absorption tower, the lean gas enters the bottom of the reabsorption tower from the top of the absorption tower. The bottom oil of the absorption tower enters the desorption tower from the top (first plate) through the bottom oil pressure reducing valve of the absorption tower. After being processed by the desorption tower, the top gas of the desorption tower merges with the rich gas compressed by the two-stage rich gas compressor, and then they are sent to the circulating water cooler before the three-stage rich gas compressor for water cooling. After being compressed by the three-stage rich gas compressor, it is mixed with acidic water to obtain a mixture. The mixture is air-cooled by the rich gas air-cooling device, and then mixed with the bottom oil of the reabsorption tower. They enter the condensate tank feed circulating water cooler for water cooling, and then enter the condensate tank. After being expanded and flashed in the condensate tank, the dissolved gas components overflow and enter the bottom of the absorption tower. The condensate enters the top of the desorption tower through the desorption tower feed pressure reducing valve. 2) Part of the bottom oil from the desorption tower exchanges heat with steam in the reboiler at the bottom of the desorption tower. The steam provides the heat source, raising the temperature of the bottom oil. After partial vaporization, it flows back to the bottom of the desorption tower. Another part of the bottom oil from the desorption tower is transported to the middle of the stabilizer tower via a deethane gasoline pump. Before being transported to the middle of the stabilizer tower, this part of the bottom oil from the desorption tower exchanges heat with the bottom oil from the stabilizer tower in the stabilizer tower feed heat exchanger. After being heated, it enters the stabilizer tower. 3) A portion of the bottom oil of the stabilizer tower is sequentially exchanged with the bottom oil of the desorption tower, the fraction from the middle of the desorption tower, and hot water. After cooling, stabilized gasoline is obtained. A portion of the stabilized gasoline enters the top of the reabsorption tower as a reabsorbent, and the other portion of the stabilized gasoline enters the stabilized gasoline collection device. A portion of the bottom oil of the stabilizer column undergoes a first heat exchange with the fraction from the reflux unit in the middle of the main fractionation column through the stabilizer column bottom reboiler, and after being heated, it is refluxed back to the bottom of the stabilizer column. 4) The gas at the top of the stabilizer tower is cooled by air by the stabilizer tower top gas air-cooling device and by water by the stabilizer tower top gas circulating water cooler. Then it is delivered to the stabilizer tower top liquid separator to obtain liquefied gas. Through the stabilizer tower top product liquefied gas and the cold reflux pump, part of the liquefied gas is delivered to the top of the stabilizer tower for reflux, and part of the liquefied gas is delivered to the collection device. The gas at the top of the reabsorption tower is dry gas.

[0033] In the second reflux, the distillate in the absorption tower is drawn out through the second liquid outlet, cooled by the second intermediate circulating water cooler of the absorption tower, and then refluxed back to the absorption tower through the second liquid inlet.

[0034] In the first reflux, the distillate in the absorption tower is drawn out through the first liquid outlet, cooled by the first intermediate circulating water cooler of the absorption tower, and then refluxed back to the absorption tower through the first liquid inlet.

[0035] The fractions in the absorption tower are cooled through reflux 1 and reflux 2.

[0036] In step 1), the three-stage rich gas compressor compresses the gas, and the outlet pressure after compression is 1.5~1.7MPa.

[0037] A portion of the bottom oil of the desorption tower undergoes a second heat exchange with the fraction from the reflux device in the middle of the main fractionation tower through the secondary heat source reboiler at the bottom of the desorption tower. The heated portion vaporizes and flows back to the bottom of the desorption tower.

[0038] Comparative Example A schematic diagram of a comparative absorption stabilization system; including absorption tower 5, reabsorption tower 11, desorption tower 12, and stabilization tower 20; The top of the absorption tower 5 is connected to the bottom of the reabsorption tower 11 via a pipeline, and the bottom of the absorption tower 5 is connected to the feed circulating water cooler 3 of the condensate tank via a pipeline. An absorption tower bottom oil pump 10 is installed on the pipeline connecting the bottom of the absorption tower 5 to the feed circulating water cooler 3 of the condensate tank. The top of the desorption tower 12 is connected to a compressed rich gas pipeline via a pipeline. The secondary rich gas compressor 1 is connected to a rich gas air-cooling device 2 via a compressed rich gas pipeline, and the compressed rich gas pipeline is connected to an acidic water pipeline. The rich gas air-cooling device 2 is connected sequentially to the feed circulating water cooler 3 of the condensate tank and the condensate tank 4 via pipelines. The condensate tank 4 is connected to the bottom of the absorption tower 5 and the top of the desorption tower 12 via pipelines, and a desorption tower feed pump 26 is installed on the pipeline connecting the condensate tank 4 and the top of the desorption tower 12. The bottom of the desorption tower 12 is connected to the bottom reboiler 13 and the feed heat exchanger 17 of the stabilizer tower via pipelines. The bottom reboiler 13 is connected to the bottom of the desorption tower 12 via a pipeline to form a reflux. The feed heat exchanger 17 of the stabilizer tower is connected to the middle of the stabilizer tower 20 via a pipeline. An ethane removal gasoline pump 16 is installed on the pipeline connecting the bottom of the desorption tower 12 and the feed heat exchanger 17 of the stabilizer tower. A reflux line is provided on the outer side of the middle of the desorption tower 12, that is, the liquid outlet in the middle of the desorption tower 12 is connected to the intermediate reboiler 15 of the desorption tower via a pipeline. The intermediate reboiler 15 of the desorption tower is connected to the liquid inlet in the lower part of the desorption tower 12 via a pipeline. The bottom of the stabilizer tower 20 is connected to the stabilizer tower feed heat exchanger 17 and the stabilizer tower bottom reboiler 25 via pipelines. The stabilizer tower feed heat exchanger 17 is connected to the desorption tower intermediate reboiler 15 and the stabilized gasoline tertiary-hot water heat exchanger 14 via pipelines. The stabilized gasoline tertiary-hot water heat exchanger 14 is connected to the stabilized gasoline collection or treatment device and the absorber tower supplementary absorbent circulating water cooler 18 via pipelines. A supplementary absorbent pump 19 is installed on the pipeline connecting the stabilized gasoline tertiary-hot water heat exchanger 14 and the absorber tower supplementary absorbent circulating water cooler 18. The absorber tower supplementary absorbent circulating water cooler 18 is connected to the top of the absorber tower 5 via a pipeline. The absorber tower supplementary absorbent circulating water cooler 18 is connected to the feed position of the first plate at the top of the absorber tower 5 via a pipeline. The stabilizer tower bottom reboiler 25 is connected to the bottom of the stabilizer tower via a pipeline to form a reflux. The top of the stabilizer tower 20 is connected in sequence via pipes to the stabilizer tower top gas air cooling device 21, the stabilizer tower top gas circulating water cooler 22, the stabilizer tower top liquid separator 23, the stabilizer tower top product liquefied gas and cold reflux pump 24. The stabilizer tower top product liquefied gas and cold reflux pump 24 are connected via pipes to the top of the stabilizer tower 20 and the liquefied gas collection device, respectively.

[0039] The reabsorption tower 11 is connected to a dry gas collection device or a processing device; the top of the reabsorption tower 11 is provided with a lean diesel inlet, and the bottom of the reabsorption tower 11 is provided with a rich diesel outlet.

[0040] The absorption tower 5 has a No. 1 reflux in the upper part and a No. 2 reflux in the lower part. The outlet of the No. 1 reflux is connected to the first intermediate reflux pump 6, the first circulating water cooler 7, and the No. 1 inlet of the absorption tower via pipelines. The outlet of the No. 2 reflux is connected to the second intermediate reflux pump 8, the second intermediate circulating water cooler 9, and the No. 2 inlet of the absorption tower via pipelines. The No. 1 outlet is higher than the No. 1 inlet; the No. 2 outlet is higher than the No. 2 inlet.

[0041] The desorption tower 12 is provided with a reflux line on the outer side of the middle section. That is, the liquid outlet in the middle of the desorption tower 12 is connected to the intermediate reboiler 15 of the desorption tower through a pipe, and the intermediate reboiler 15 of the desorption tower is connected to the liquid inlet in the lower part of the desorption tower 12 through a pipe.

[0042] The stabilizer reboiler 25 uses the fraction from the middle of the main fractionation column as a heat source to stabilize the bottom liquid. The fraction from the middle of the main fractionation column is heated via reflux. A valve is installed on the reflux line.

[0043] In the comparative example, the rich gas is compressed to 1.0 MPa by a two-stage rich gas compressor, and then mixed with the desorption gas (i.e., the desorbed gas) at the top of the desorption tower and the acidic water from the main fractionation tower. After being cooled by the rich gas air-cooling device and the feed circulating water cooler of the condensate tank, the gas enters the condensate tank. Then the gas enters the bottom of the absorption tower, and the condensate enters the top of the desorption tower through the desorption tower feed pump.

[0044] Crude gasoline enters the absorption tower. After being processed by the absorption tower, the lean gas at the top of the absorption tower enters the re-absorption tower. The re-absorbent is the main fraction of diesel products from the fractionation tower, and the product obtained at the top of the re-absorption tower is dry gas.

[0045] The absorbent consists of crude gasoline from the main fractionation tower and partially stabilized gasoline from the stabilization tower. Lean gas from the top of the absorber enters the bottom of the reabsorption tower; the top gas from the reabsorption tower is dry gas, and lean diesel oil is added to the reabsorption tower as the absorbent. The bottom oil from the reabsorption tower is rich diesel oil, which is returned to the main fractionation tower for separation.

[0046] A portion of the bottom oil from the desorption tower exchanges heat with steam in the bottom reboiler of the desorption tower. The steam provides the heat source, raising the temperature of the bottom oil, which then flows back to the bottom of the desorption tower. Another portion of the bottom oil is pumped to the middle of the stabilizer tower via a deethane gasoline pump. Before being pumped to the middle of the stabilizer tower, this portion of the bottom oil exchanges heat with the bottom oil from the stabilizer tower in the stabilizer tower feed heat exchanger, and then enters the stabilizer tower after being heated. A portion of the bottom oil from the stabilizer tower undergoes heat exchange sequentially with the bottom oil from the desorption tower, the fraction from the middle of the desorption tower, and hot water. After cooling, stabilized gasoline is obtained. A portion of the stabilized gasoline enters the top of the absorber tower as a supplementary absorbent, while the other portion enters the stabilized gasoline collection device. A portion of the bottom oil of the stabilizer column exchanges heat with the fraction from the reflux unit in the middle of the main fractionation column through the bottom reboiler of the stabilizer column. The heated portion vaporizes and is then refluxed back to the bottom of the stabilizer column. The gas at the top of the stabilizer tower is cooled by air by the stabilizer tower top gas air-cooling device and by water by the stabilizer tower top gas circulating water cooler. Then it is delivered to the stabilizer tower top liquid separator to obtain liquefied gas. Through the stabilizer tower top product liquefied gas and the cold reflux pump, part of the liquefied gas is delivered to the top of the stabilizer tower for reflux, and part of the liquefied gas is delivered to the collection device.

[0047] The rich diesel oil absorbed by the lean diesel oil in the reabsorption tower is returned to the main fractionation tower for circulation. The absorbent oil at the bottom of the absorption tower is cooled before entering the desorption tower after returning to the feed circulating water cooler of the condensate tank. The oil contains about 90% ≥C3 components, which need to flow out from the bottom of the desorption tower. Therefore, it needs to be heated after cooling, which increases the load on the reboiler at the bottom of the desorption tower.

[0048] Taking a 1 million tons / year catalytic cracking unit in an oil refinery as an example, the corresponding crude gasoline output is 45.1 t / h and rich gas output is 15737 Nm³. 3 / h, 27.2t / h. The main operating parameters and energy consumption of its main fractionation tower and absorption stabilization system are shown in Table 1 and Table 2, respectively.

[0049] Table 1. Main operating parameters and energy consumption of the main fractionation column in the comparative example.

[0050] Table 2. Main operating parameters and energy consumption of the comparative absorption stabilization system

[0051] As can be seen from Tables 1 and 2, the 21.4 t / h rich diesel oil returned to the tower at 141.2℃, which is 57℃ lower than the feed plate equilibrium temperature; the heat extracted from the first main fractionation tower is 801 × 10⁻⁶. 4 kcal / h, rich gas compressor power consumption 1946kw; desorption tower bottom reboiling load 411×10 4 kcal / h, consuming 7.6t / h of 1.0MPa reboiling steam; stabilizer tower reboiling load 492×10 4 kcal / h.

[0052] Example 1 A schematic diagram of the absorption stabilization system in this embodiment is shown below. Figure 2 As shown; it includes absorption tower 5, reabsorption tower 11, desorption tower 12, and stabilization tower 20; The top of the absorption tower 5 is connected to the bottom of the reabsorption tower 11 via a pipe, and the bottom of the absorption tower 5 is connected to the top of the desorption tower 12 via a pipe. A pressure reducing valve 10 for the bottom oil of the absorption tower to the desorption tower is installed on the connecting pipe. The top of the desorption tower 12 is connected to the compressed rich gas pipeline via a pipe, meaning the pipe at the top of the desorption tower 12 merges with the compressed rich gas pipeline. The merged pipeline is sequentially connected to the circulating water cooler 28 before the three-stage rich gas compressor and the three-stage rich gas compressor 27. The three-stage rich gas compressor 27 is connected to the reabsorption tower 11 via a pipe. The rich gas compressor 27 is connected to the rich gas air-cooling unit 2, the condensate tank feed circulating water cooler 3, and the condensate tank 4. The pipe connecting the rich gas compressor 27 to the rich gas air-cooling unit 2 merges with the acidic water pipe. The pipe connecting the rich gas air-cooling unit 2 to the condensate tank feed circulating water cooler 3 merges with the pipe from the bottom of the reabsorption tower 11. The condensate tank 4 is connected to the bottom of the absorption tower 5 and the top of the desorption tower 12 through pipes. The pipe connecting the condensate tank 4 to the top of the desorption tower 12 is equipped with a desorption tower feed pressure reducing valve 26. The bottom of the desorption tower 12 is connected to the bottom reboiler 13 and the feed heat exchanger of the stabilizer tower via pipelines. The bottom reboiler 13 is connected to the bottom of the desorption tower 12 via a pipeline to form a reflux. The feed heat exchanger 17 of the stabilizer tower is connected to the stabilizer tower via a pipeline. An ethane removal gasoline pump 16 is installed on the pipeline connecting the bottom of the desorption tower 12 and the feed heat exchanger 17 of the stabilizer tower. A reflux line is provided on the outer side of the middle part of the desorption tower 12. That is, the liquid outlet in the middle part of the desorption tower 12 is connected to the intermediate reboiler 15 of the desorption tower via a pipeline. The intermediate reboiler 15 of the desorption tower is connected to the liquid inlet in the lower part of the desorption tower 12 via a pipeline. The bottom of the stabilization tower 20 is connected to the stabilization tower feed heat exchanger 17 and the stabilization tower bottom reboiler 25 via pipelines. The stabilization tower feed heat exchanger 17 is connected to the desorption tower intermediate reboiler 15 and the stabilized gasoline tertiary-hot water heat exchanger 14 via pipelines. The stabilized gasoline tertiary-hot water heat exchanger 14 is connected to the stabilized gasoline collection or treatment device and the absorbent supplement circulating water cooler 18 via pipelines. A supplementary absorbent pump 19 is installed on the pipeline connecting the stabilized gasoline tertiary-hot water heat exchanger 14 and the absorbent supplement circulating water cooler 18. The absorbent supplement circulating water cooler 18 is connected to the top of the reabsorption tower 11 via a pipeline. The absorbent supplement circulating water cooler 18 is connected to the feed position of the first plate at the top of the reabsorption tower 11 via a pipeline. The top of the reabsorption tower 11 is provided with a dry gas outlet. The top of the stabilizer tower 20 is connected in sequence via pipes to the stabilizer tower top air cooler 21, the stabilizer tower top air circulating water cooler 22, the stabilizer tower top liquid separator 23, the stabilizer tower top product liquefied gas and the cold reflux pump 24. The stabilizer tower top product liquefied gas and the cold reflux pump 24 are connected via pipes to the top of the stabilizer tower 20 and the liquefied gas collection device, respectively.

[0053] The absorption tower 5 has a No. 1 reflux in the upper part and a No. 2 reflux in the lower part. The outlet of the No. 1 reflux is connected to the first intermediate reflux pump 6, the first circulating water cooler 7, and the No. 1 inlet of the absorption tower via pipelines. The outlet of the No. 2 reflux is connected to the second intermediate reflux pump 8, the second intermediate circulating water cooler 9, and the No. 2 inlet of the absorption tower via pipelines. The No. 1 outlet is higher than the No. 1 inlet; the No. 2 outlet is higher than the No. 2 inlet.

[0054] The system includes a two-stage rich gas compressor 1, which is connected to the pre-circulating water cooler 28 of the three-stage rich gas compressor via a pipeline. This pipeline is the rich gas pipeline after compression.

[0055] In the system, or, the top of the desorption tower 12 is connected to the circulating water cooler 28 before the third-stage rich gas compressor via a pipeline; the second-stage rich gas compressor 1 is connected to the circulating water cooler 28 before the third-stage rich gas compressor via a pipeline; the circulating water cooler 28 before the third-stage rich gas compressor is connected to the third-stage rich gas compressor 27 via a pipeline; the third-stage rich gas compressor 27 is connected to the rich gas air-cooling device 2 via a pipeline; the acidic water outlet is connected to the rich gas air-cooling device 2 via a pipeline; the rich gas air-cooling device 2 is connected to the condensate tank feed circulating water cooler 3 via a pipeline; the bottom of the reabsorption tower 11 is connected to the condensate tank feed circulating water cooler 3 via a pipeline; and the condensate tank feed circulating water cooler 3 is connected to the condensate tank 4 via a pipeline.

[0056] Process parameters for this embodiment: 1) The rich gas is compressed by a three-stage rich gas compressor, increasing the pressure from 1.0 MPa at the outlet of the two-stage rich gas compressor to 1.6 MPa at the outlet of the three-stage rich gas compressor; 2) In this embodiment, 37.9 t / h stable gasoline is used as the absorbent in the reabsorption tower; the replenishment absorbent in the absorption tower is zero. 3) The pressure at the top of the absorption tower increased from about 0.9 MPa in the comparative example to 1.6 MPa, and the pressure at the top of the reabsorption tower also increased from about 0.9 MPa in the comparative example to 1.6 MPa; the pressures at the top of the stabilization tower and the desorption tower remained unchanged.

[0057] The composition of the lean gas at the top of the absorption tower and the dry gas at the top of the reabsorption tower in Example 1 and the comparative example is shown in Table 3.

[0058] Table 3. Composition of lean and dry gases in Example 1 and the comparative example, and comparison with the comparative example.

[0059] It can be seen that the flow rate and composition of the dry gas product are consistent with those of the comparative example, with the content of ≥C3 components all being 3%v.

[0060] The main operating parameters and energy consumption of the main fractionation tower and absorption stabilization system of Example 1 and Comparative Example 1 are shown in Table 4.

[0061] Table 4. Main operating parameters and energy consumption of Example 1 and Comparative Example

[0062] It is evident that the material balance remains unchanged. And the heat extracted from the middle is 917 × 10⁻⁶. 4 kcal / h (the heat extraction in the first part refers to the heat provided by the reflux to the bottom oil of the stabilizer column from the outer middle part of the main fractionation column), compared with the comparative example 801×10 4 kcal / h increased by 116 × 10 4 kcal / h, equivalent to the heat required to produce 1.93 t / h of medium-pressure 3.5 MPa steam; the cooling load at the top of the main fractionation tower is reduced by 41 × 10 4 kcal / h; desorption tower bottom reboil load from 411×10 4 kcal / h dropped to 358×10 4 kcal / h, saving 1t / h of 1.0MPa steam; the reboiling load at the bottom of the stabilizer is reduced by 56×10 4 This translates to a saving of 0.93 t / h of 3.5MPa steam; however, it increases compressor power consumption by 332 kW. Based on the following costs: 3.5MPa steam at 276.59 yuan / t, 1.0MPa steam at 242.59 yuan / t, electricity at 0.65 yuan / kWh, and an annual operating time of 8000 hours, Example 1 reduces energy costs by 6.543 million yuan / year.

[0063] Example 2 This embodiment adds a secondary heat source reboiler at the bottom of the desorption tower to the system provided in Embodiment 1. This reboiler is installed in parallel with the existing reboiler at the bottom of the desorption tower. A detailed structural diagram is shown below. Figure 3 As shown in the figure. The reboiler at the bottom of the desorption tower retains steam for heating and plays an auxiliary regulatory role. The secondary heat source reboiler at the bottom of the desorption tower uses the heat source from the first fractionation tower and is normally kept on during production. The parameters and energy consumption of the absorption stabilization system in Example 2 and the comparative example are shown in Table 5.

[0064] By adjusting the process flow, the heat extraction load of the first stage (where the reflux in the middle of the main fractionation tower provides heat to other systems through distillation) can be increased by 116 × 10⁻⁶. 4 kcal / h, and the load reduction at the bottom of the stabilizer tower is 56×10 4 This method, while maintaining the original process, can generate an additional 172 × 10 kcal / h. 4 With a heat capacity of kcal / h and a temperature above 200℃, the quality is high. It can be used as a reboiling heat source at the bottom of the desorption tower, which can significantly reduce the steam consumption at the bottom of the desorption tower.

[0065] Table 5. Parameters and energy consumption of Example 2 and Comparative Example

[0066] In Example 2, because the excess heat from Example 1 is used for the reboiling load of the desorption tower, the consumption of low-pressure steam is significantly reduced from 7.6 t / h to 3.4 t / h, saving 4.2 t / h of steam. The parameters of the remaining main fractionation tower and absorption stabilization system, as well as the flow rates and masses of each product, are consistent with the data from Example 1. Based on the costs of 3.5 MPa steam (276.59 yuan / t), 1.0 MPa steam (242.59 yuan / t), electricity (0.65 yuan / kWh), and an annual operating time of 8000 hours, Example 2 reduces the overall energy cost of the unit by 6.425 million yuan.

Claims

1. An absorption-stabilization system in a catalytic cracking unit using stabilized gasoline as a reabsorber, characterized by: The system comprises an absorption tower, a reabsorption tower, a desorption tower and a stabilization tower. The top of the absorption tower is connected to the bottom of the reabsorption tower through a pipeline, the bottom of the absorption tower is connected to the top of the desorption tower through a pipeline, and a pressure reducing valve is arranged on the pipeline connecting the bottom of the absorption tower to the top of the desorption tower; the top of the desorption tower is connected to a pipeline for compressed rich gas through a pipeline, the pipeline for compressed rich gas is merged with the pipeline at the top of the desorption tower, and the merged pipeline is sequentially connected to a pre-circulating water cooler of a three-stage rich gas compressor and the three-stage rich gas compressor; the three-stage rich gas compressor is sequentially connected to a condensing oil tank through a pipeline; the pipeline connecting the three-stage rich gas compressor to the condensing oil tank is merged with a pipeline from the bottom of the reabsorption tower; the condensing oil tank is connected to the bottom of the absorption tower and the top of the desorption tower through pipelines respectively, and a pressure reducing valve is arranged on the pipeline connecting the condensing oil tank to the top of the desorption tower. The bottom of the desorption tower is connected to a desorption tower bottom reboiler and a stabilization tower feed heat exchanger through pipelines respectively; the desorption tower bottom reboiler is connected to the bottom of the desorption tower through a pipeline to form a reflux; the stabilization tower feed heat exchanger is connected to the stabilization tower through a pipeline, and a de-ethanized gasoline pump is arranged on the pipeline connecting the bottom of the desorption tower to the stabilization tower feed heat exchanger; a reflux line is arranged on the outer side of the middle part of the desorption tower, that is, a liquid outlet in the middle part of the desorption tower is connected to a desorption tower middle reboiler through a pipeline, and the desorption tower middle reboiler is connected to a liquid inlet in the lower part of the desorption tower through a pipeline. The bottom of the stabilization tower is connected to the stabilization tower feed heat exchanger and a stabilization tower bottom reboiler through pipelines respectively; the stabilization tower feed heat exchanger is sequentially connected to the desorption tower middle reboiler and a stabilization gasoline three-time hot water heat exchanger through a pipeline; the stabilization gasoline three-time hot water heat exchanger is connected to a stabilization gasoline collection or treatment device and an absorption tower supplementary absorbent circulating water cooler through pipelines respectively; a supplementary absorbent pump is arranged on the pipeline connecting the stabilization gasoline three-time hot water heat exchanger to the absorption tower supplementary absorbent circulating water cooler; the absorption tower supplementary absorbent circulating water cooler is connected to the top of the reabsorption tower through a pipeline; and the absorption tower supplementary absorbent circulating water cooler is connected to a first plate feeding position of the top of the reabsorption tower through a pipeline. The top of the stabilization tower is sequentially connected to a stabilization tower top gas air cooler, a stabilization tower top gas circulating water cooler, a stabilization tower top liquid separator, a stabilization tower top product liquid gas and a cold reflux pump through pipelines; the stabilization tower top product liquid gas and the cold reflux pump are connected to the top of the stabilization tower and a liquid gas collection device through pipelines respectively.

2. The system according to claim 1, wherein the system is an absorption-stabilization system using stabilized gasoline as a reabsorbent in a catalytic cracking apparatus. A first reflux is arranged in the upper part of the absorption tower, and a second reflux is arranged in the lower part of the absorption tower; a first liquid outlet of the first reflux is sequentially connected to a first intermediate reflux pump of the absorption tower, a first circulating water cooler of the absorption tower and a first liquid inlet through pipelines; a second liquid outlet of the second reflux is sequentially connected to a second intermediate reflux pump of the absorption tower, a second intermediate circulating water cooler of the absorption tower and a second liquid inlet through pipelines.

3. The system according to claim 1, wherein the system is a catalytic cracking unit using a stabilized gasoline as a reabsorber. The system comprises a two-stage rich gas compressor, and the two-stage rich gas compressor is connected to a pre-circulating water cooler of a three-stage rich gas compressor through a pipeline, and the pipeline is a pipeline for compressed rich gas. The top of the reabsorption tower is provided with a dry gas outlet.

4. The absorption-stabilization system using stabilized gasoline as a reabsorber in the catalytic cracking apparatus according to claim 1, characterized by: The desorption tower bottom is also connected with a secondary heat source reboiler at the bottom of the desorption tower through a pipeline, and the secondary heat source reboiler at the bottom of the desorption tower is connected with the bottom of the desorption tower through a pipeline to form a reflux; the secondary heat source reboiler at the bottom of the desorption tower is provided with heat by the remaining heat after the fraction in the middle of the main fractionating tower provides heat for the stable tower bottom liquid.

5. A method for rectification using an absorption-stabilization system with a stabilized gasoline as a reabsorbent in a catalytic cracking unit according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: 1) The crude gasoline enters the absorption tower, is treated by the absorption tower, and the lean gas enters the bottom of the reabsorption tower from the top of the absorption tower; The oil at the bottom of the absorption tower enters from the top of the desorption tower, is treated by the desorption tower, the gas at the top of the desorption tower is combined with the compressed rich gas, then is water-cooled, compressed, mixed with the sour water, and the mixed liquid is obtained; the mixed liquid is air-cooled, then is mixed with the oil at the bottom of the reabsorption tower, is water-cooled, and enters the condensed oil tank together, passes through the condensed oil tank, is expanded and flashed, the dissolved gas component overflows into the bottom of the absorption tower, and the condensed oil enters the desorption tower; 2) A part of the oil at the bottom of the desorption tower is heated by steam, is partially gasified, and is refluxed to the middle of the desorption tower, and a part of the oil at the bottom of the desorption tower is heat-exchanged with the fraction from the middle of the main fractionating tower, and is heated to enter the stable tower; 3) A part of the oil at the bottom of the stable tower is heat-exchanged with the oil at the bottom of the desorption tower, the fraction from the middle of the desorption tower and hot water in turn, and the stable gasoline is obtained after being cooled; a part of the stable gasoline enters the top of the reabsorption tower as a reabsorbing agent, and another part of the stable gasoline enters a stable gasoline collecting device; A part of the oil at the bottom of the stable tower is heat-exchanged with the fraction from the reflux device in the middle of the main fractionating tower through a stable tower bottom reboiler, and is heated to be refluxed to the bottom of the stable tower; 4) The gas at the top of the stable tower is air-cooled, is water-cooled, and then is transported to a stable tower top liquid separator to obtain liquefied gas; a part of the liquefied gas is transported to the top of the stable tower to be refluxed, and another part of the liquefied gas is transported to a collecting device; The gas at the top of the reabsorption tower is dry gas.

6. The method of claim 5, wherein: In the step 1), the compressed rich gas in the combination of the gas at the top of the desorption tower and the compressed rich gas refers to that the rich gas is compressed by a secondary rich gas compressor; In the step 1), then water-cooled and compressed, wherein the compression refers to that the compression is performed by a tertiary rich gas compressor; the pressure at the outlet after the compression is 1.5-1.7 MPa.

7. The method of claim 5, wherein: A part of the oil at the bottom of the desorption tower is heat-exchanged with the fraction from the reflux device in the middle of the main fractionating tower through the secondary heat source reboiler at the bottom of the desorption tower, is heated and partially gasified, and is refluxed to the bottom of the desorption tower.

8. The method of claim 5, wherein: The desorption tower bottom reboiler retains the steam heating measure, plays an auxiliary adjusting role, the secondary heat source reboiler at the bottom of the desorption tower uses the heat source in the middle of the main fractionating tower, and is normally opened in normal production.

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