Atmospheric-reduced pressure light hydrocarbon recovery integrated device using low-temperature heat instead of high-temperature heat

Abstract

The utility model discloses an atmospheric and vacuum light hydrocarbon recovery integrated unit using low-temperature heat instead of high-temperature heat, which belongs to the technical field of catalytic cracking units and comprises an atmospheric tower, the atmospheric tower is connected with an atmospheric-medium circulating oil path, and a first heat exchanger and a second heat exchanger are connected in series on the atmospheric-medium circulating oil path; the atmospheric tower is connected with a second normal stripping tower and a third normal stripping tower through a second normal pipeline and a third normal pipeline; the normal second pipeline and the normal third pipeline are connected with a mixing pipeline; a reboiler is additionally arranged at the bottom of the light hydrocarbon recovery desorption tower, a cold source inlet end and a cold source outlet end of the reboiler are connected with the light hydrocarbon recovery desorption tower, a heat source inlet end is connected with the mixing pipeline, a heat source outlet end is connected with an air cooling pipeline, and the air cooling pipeline is connected with an air cooling device. A second normal pipeline and a third normal pipeline are mixed together and sent to a reboiler to heat a light hydrocarbon recovery desorption tower, and a first normal circulation oil path and a middle normal circulation oil path are all used for raw oil heat exchange; high-temperature waste heat and low-temperature waste heat can be effectively utilized, so that the gas consumption of the heating furnace is reduced, and the load of an air cooling device is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of atmospheric and vacuum light hydrocarbon combined devices, and in particular relates to an atmospheric and vacuum light hydrocarbon recovery combined device using low-temperature heat to replace high-temperature heat. Background Art

[0002] The statements in this section merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] In the petrochemical industry, heavy oil needs to be processed into light oil. This requires the use of a light hydrocarbon recovery desorption tower. In traditional processes, the bottom of the light hydrocarbon recovery desorption tower is connected to a steam reboiler, which uses 1.0 MPa superheated steam as a heat source to desorb the C2 components in the condensate. In this process, the reboiler at the bottom of the light hydrocarbon recovery desorption tower is overloaded and easily results in heat waste.

[0004] To solve the above problems, Figure 1 As shown, the prior art adds a reboiler 2 at the bottom of the light hydrocarbon recovery and desorption tower 1, and the model of the reboiler 2 is DN600; and the normal-medium circulation oil line 31 of the atmospheric pressure tower 3 is connected to the reboiler 2, and the normal-medium circulation oil line 31 is used as a heat source to heat the oil at the bottom of the light hydrocarbon recovery and desorption tower; then the normal-medium circulation oil line 31 heats the raw oil, and finally returns to the atmospheric pressure tower; the raw oil is heated by the heating furnace 8 and enters the atmospheric pressure tower for distillation; the diesel in the atmospheric pressure tower is stripped out by the normal-second stripping tower and the normal-third stripping tower, and then the normal-second line pipeline and the normal-third line pipeline exchange heat with the raw oil. The temperature of the diesel after heat exchange is about 130°C and is directly sent to the air cooling device for cooling.

[0005] The temperature at the bottom of the light hydrocarbon recovery desorption tower is controlled at approximately 95°C, while the temperature of the circulating oil line 31 in the first stripper is approximately 200°C. Heating the bottom of the light hydrocarbon recovery desorption tower results in a loss of approximately 30°C, dropping the temperature to 170°C. Using 170°C low-temperature heat to heat the feedstock, the heated feedstock temperature will not exceed 170°C. This undoubtedly increases the load on the heating furnace to heat the feedstock, resulting in energy waste. Furthermore, after exchanging heat with the feedstock in the second and third strippers, the diesel fuel in the second and third strippers is directly fed into the air cooling unit for cooling, even at a temperature of approximately 130°C. This also results in energy waste.

[0006] In summary, how to recover the low-temperature heat from the second and third line pipelines and utilize the high-temperature heat from the first line to better heat the crude oil and maximize the benefits of the device is an urgent problem to be solved. Utility Model Content

[0007] In response to the above problems, the utility model provides a combined atmospheric and vacuum light hydrocarbon recovery device that uses low-temperature heat instead of high-temperature heat. The normal second-line pipeline and the normal third-line pipeline are mixed together and sent to the reboiler to heat the light hydrocarbon recovery desorption tower; the normal first-line circulating oil circuit is fully utilized for raw oil heat exchange; it can reduce the gas consumption of the heating furnace, reduce the load of the air cooling device, and save air cooling electricity consumption.

[0008] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A combined atmospheric and vacuum light hydrocarbon recovery unit using low-temperature heat instead of high-temperature heat comprises an atmospheric tower connected to a normal-medium circulating oil circuit, wherein a first heat exchanger and a second heat exchanger are connected in series on the normal-medium circulating oil circuit;

[0010] The atmospheric pressure tower is also connected to the normal second-line stripping tower and the normal third-line stripping tower respectively; the normal second-line stripping tower is connected to the normal second-line pipeline, the normal third-line stripping tower is connected to the normal third-line pipeline, and the normal second-line pipeline and the normal third-line pipeline are connected to the mixing pipeline;

[0011] It also includes a light hydrocarbon recovery desorption tower, and the original 1.0Mpa steam reboiler of the light hydrocarbon recovery desorption tower is retained;

[0012] A reboiler is added to the bottom of the light hydrocarbon recovery and desorption tower. Specifically, the cold source inlet and outlet ends of the reboiler are connected to the light hydrocarbon recovery and desorption tower, the heat source inlet end is connected to the mixing pipeline, the heat source outlet end is connected to the air cooling pipeline, the air cooling pipeline is connected to the air cooling device, and the air cooling device is connected to the tank area.

[0013] Preferably, the mixing pipeline is connected to the air cooling pipeline, and a second regulating valve is provided between the mixing pipeline and the air cooling pipeline; and a first regulating valve is provided between the mixing pipeline and the reboiler.

[0014] Preferably, a temperature sensor is provided between the reboiler and the light hydrocarbon recovery and desorption tower. Specifically, the temperature sensor is provided at the cold source outlet end of the reboiler.

[0015] Preferably, a control system is further included, and the temperature sensor, the first regulating valve, and the second regulating valve are all connected to the control system.

[0016] Preferably, the heat source pipelines of the first heat exchanger and the second heat exchanger are connected to the Chang-Zhong circulating oil circuit, and the cold source pipeline is connected to the raw oil pipeline; a Chang-Zhong circulating pump is provided on the Chang-Zhong circulating oil circuit.

[0017] Preferably, the raw oil pipeline is provided with a plurality of heat exchangers including a first heat exchanger and a second heat exchanger; the raw oil pipeline is connected to a heating furnace, and the heating furnace is connected to the atmospheric pressure tower.

[0018] Preferably, the normal second-line stripping tower is connected to the normal second-line heat exchanger through a normal second-line pipeline, a normal second-line pump is arranged between the normal second-line stripping tower and the normal second-line heat exchanger, and a normal second-line regulating valve is arranged on the side of the normal second-line heat exchanger away from the normal second-line pump.

[0019] Preferably, the conventional three-line stripping tower is connected to the conventional three-line heat exchanger through a conventional three-line pipeline, a conventional three-line pump is arranged between the conventional three-line stripping tower and the conventional three-line heat exchanger, and a conventional three-line regulating valve is arranged on the side of the conventional three-line heat exchanger away from the conventional three-line pump.

[0020] Preferably, the normal three-line heat exchanger or the normal two-line heat exchanger is connected to the normal three-line pipeline or the normal two-line pipeline through its heat source pipeline, and the cold source pipelines of the normal three-line heat exchanger and the normal two-line heat exchanger are connected to the raw oil pipeline.

[0021] Preferably, the normal three-line heat exchanger and the normal two-line heat exchanger are arranged in front of the first heat exchanger and the second heat exchanger.

[0022] Compared with the prior art, the advantages and positive effects of this utility model are:

[0023] The utility model mixes the second and third normal pipelines through the heat exchanger, sends them to the reboiler to heat the light hydrocarbon recovery and desorption tower, and then sends them to the air cooling device for air cooling; the entire normal one medium circulation oil circuit is utilized for heat exchange of raw oil; both high-temperature waste heat and low-temperature waste heat can be effectively utilized, thereby reducing the gas consumption of the heating furnace, reducing the load of the air cooling device, saving air cooling electricity consumption, not only saving resources but also saving capital costs, and realizing maximum device efficiency.

[0024] The utility model also arranges a temperature sensor between the newly added reboiler and the light hydrocarbon recovery and desorption tower. The mixing pipeline is not only connected to the reboiler, but also connected to the air cooling device through the air cooling pipeline. The first and second regulating valves are respectively arranged between the mixing pipeline and the reboiler, and between the mixing management and the air cooling device. The temperature sensor and the first and second regulating valves are all connected to the existing control system, which can control the flow rate of the mixed oil flowing from the mixing pipeline to the reboiler, thereby accurately controlling the heating temperature of the light hydrocarbon recovery and desorption tower by the reboiler, and ensuring the temperature stability in the light hydrocarbon recovery and desorption tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention.

[0026] Figure 1 It is a schematic diagram of the prior art;

[0027] Figure 2It is a schematic diagram of Example 1 of the present utility model;

[0028] In the picture:

[0029] 1. Light hydrocarbon recovery desorption tower; 2. Reboiler; 3. Atmospheric pressure tower; 31. Changyi medium circulating oil circuit; 32. Changyi medium circulating pump; 33. First heat exchanger; 34. Second heat exchanger; 4. Changyi line stripping tower; 41. Changyi line pipeline; 42. Changyi line heat exchanger; 43. Changyi line pump; 44. Changyi line regulating valve; 5. Changyi line stripping tower; 51. Changyi line pipeline; 52. Changyi line heat exchanger; 53. Changyi line pump; 54. Changyi line regulating valve; 6. Mixing pipeline; 61. First regulating valve; 62. Second regulating valve; 63. Temperature sensor; 7. Raw oil pipeline; 8. Heating furnace; 91. Air cooling pipeline; 9. Air cooling device. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0031] Name explanation:

[0032] The medium of the Changyi circulating oil circuit is the gasoline and diesel mixture of the atmospheric tower. Its main function is to serve as the external reflux of the atmospheric tower, extracting the excess heat from the distillation process in the tower through a pump, exchanging heat with the crude oil, and then returning it to the tower.

[0033] Normally, the medium in the second-line pipeline and the third-line pipeline is the distillation product, which is straight-run diesel. After heat exchange with crude oil, it is air-cooled to a safe temperature (usually 55°C) and sent to the tank area for storage.

[0034] The present invention is described in detail below with reference to the accompanying drawings. This embodiment discloses a combined atmospheric and vacuum light hydrocarbon recovery unit that uses low-temperature heat to replace high-temperature heat. Figure 2 As shown, the atmospheric tower 3 includes an atmospheric tower 3, which is connected to a normal-medium circulating oil circuit 31. The normal-medium circulating oil circuit 31 extracts oil from the atmospheric tower 3 and returns to the atmospheric tower 3 after a series of heat exchanges. Specifically, a normal-medium circulating pump 32 is provided on the normal-medium circulating oil circuit 31 to maintain the circulation operation of the normal-medium circulating oil circuit 31.

[0035] The first heat exchanger 33 and the second heat exchanger 34 are connected in series on the Changyi circulating oil circuit 31. Specifically, the heat source pipelines of the first heat exchanger 33 and the second heat exchanger 34 are connected to the Changyi circulating oil circuit 31, while the cold source pipelines of the first heat exchanger 33 and the second heat exchanger 34 are connected to the raw oil pipeline 7.

[0036] like Figure 2As shown, the raw oil pipeline 7 is provided with multiple heat exchangers, including a first heat exchanger and a second heat exchanger, for heating the raw oil passing through. In this embodiment, eight heat exchangers are provided on the raw oil pipeline 7. It is understood that the number of heat exchangers is set according to actual conditions, and in some embodiments, more heat exchangers can be provided. The raw oil pipeline 7 is connected to a heating furnace 8, which is connected to the atmospheric pressure tower 3. The raw oil flows into the raw oil pipeline 7 from the end away from the heating furnace 8, and then passes through multiple heat exchangers to increase the temperature. It is heated to the required temperature in the heating furnace. In this embodiment, the raw oil is heated to 355°C and then sent to the atmospheric pressure tower 3 for distillation.

[0037] The system further comprises a conventional second-line stripping tower 4 and a conventional third-line stripping tower 5. The atmospheric pressure tower 3 is connected to the conventional second-line stripping tower 4 and the conventional third-line stripping tower 5, respectively. Diesel is extracted from the atmospheric pressure tower 3 and enters the conventional second-line stripping tower 4 and the conventional third-line stripping tower 5, respectively. The conventional second-line stripping tower 4 is connected to the conventional second-line heat exchanger 42 via a conventional second-line pipeline 41. A conventional second-line pump 43 is provided between the conventional second-line stripping tower 4 and the conventional second-line heat exchanger 42. A conventional second-line regulating valve 44 is provided on the side of the conventional second-line heat exchanger 42 away from the conventional second-line pump 43. The conventional third-line stripping tower 5 is connected to the conventional third-line heat exchanger 52 via a conventional third-line pipeline 51. A conventional third-line pump 53 is provided between the conventional third-line stripping tower 5 and the conventional third-line heat exchanger 52. A conventional third-line regulating valve 54 is provided on the side of the conventional third-line heat exchanger 52 away from the conventional third-line pump 53. The normal second-line pipeline 41 and the normal third-line pipeline 51 are merged into the mixing pipeline 6. Specifically, the normal second-line pipeline and the normal third-line pipeline are merged into the mixing pipeline 6 on the side of the normal second-line regulating valve 44 away from the normal third-line heat exchanger, and on the side of the normal third-line regulating valve 54 away from the normal third-line heat exchanger.

[0038] It should be noted that both the third-line heat exchanger 52 and the second-line heat exchanger 42 are connected to the third-line or second-line normal pipelines via their heat source pipelines, while their cold source pipelines are connected to the crude oil pipeline. The diesel flowing in the third-line and second-line normal pipelines serves as a heat source to heat the crude oil in the crude oil pipeline. Specifically, the third-line heat exchanger 52 and the second-line normal heat exchanger 42 are located before the first heat exchanger 33 and the second heat exchanger 34.

[0039] like Figure 2 As shown, the system also includes a light hydrocarbon recovery and desorption tower 1, with a reboiler 2 installed at the bottom. The reboiler's cold source inlet and outlet are connected to the light hydrocarbon recovery and desorption tower. The reboiler's heat source inlet is connected to a mixing line 6, and its heat source outlet is connected to an air cooling line 91. Air cooling line 91 is connected to an air cooling device 9, which is connected to a tank farm. The mixed oil in the mixing line serves as a heat source to heat the light hydrocarbon recovery and desorption tower.

[0040] like Figure 2As shown, a first regulating valve 61 is installed between the mixing line 6 and the reboiler 2. The mixing line 6 is also directly connected to the air cooling line 91. A second regulating valve 62 is installed between the mixing line 6 and the air cooling line 91. A temperature sensor 63 is installed between the reboiler 2 and the light hydrocarbon recovery desorption tower 1. Specifically, the temperature sensor 63 is installed at the cold source outlet of the reboiler 2. A control system is also included. This control system is based on existing technology and is the original control system in the production line. The first regulating valve 61, the second regulating valve 62, and the temperature sensor 63 are connected to the control system.

[0041] Temperature sensor 63 monitors the heating temperature of oil flowing from reboiler 2 to light hydrocarbon recovery desorption tower 1 and transmits this information to the control system. The control system then controls the opening and closing, or the degree of opening and closing, of first and second regulating valves 61 and 62 based on the monitored temperature. For example, when temperature sensor 63 detects that the heating temperature is too high, exceeding a set maximum threshold, the control system will open second regulating valve 62 and, accordingly, reduce the opening and closing degree of first regulating valve 61, thereby reducing the flow of mixed oil to the reboiler and allowing some of the mixed oil to flow directly into the air cooling device. When temperature sensor 63 detects that the heating temperature drops to a set minimum threshold, the control system will close second regulating valve 62 or reduce its opening and closing degree, increase the opening and closing degree of first regulating valve 61, and increase the flow of mixed oil to the reboiler. This allows precise control of the reboiler's heating temperature for the light hydrocarbon recovery desorption tower, ensuring temperature stability within the tower. It is understood that the aforementioned control processes of the control system are all achievable using existing technology.

[0042] In this embodiment, the diesel in the normal second-line pipeline and the normal third-line pipeline undergoes heat exchange and enters the mixing pipeline for mixing. At this time, the mixed oil temperature is about 130°C. The mixed oil enters the reboiler 2 to be heated at the bottom of the light hydrocarbon recovery and desorption tower. After losing about 30°C in temperature, the 102°C mixed oil flows through the air cooling pipeline 91 to the air cooling device for air cooling, and is cooled to 55°C and sent to the tank area.

[0043] Different from Figure 1 In the embodiment, diesel is extracted from the normal second line pipeline and the normal third line pipeline by a pump and pressurized, and is sent to the heat exchanger for heat exchange and then directly sent to the respective air cooling devices; in this embodiment, diesel is mixed together from the normal second line pipeline and the normal third line pipeline after heat exchange in the heat exchanger and sent to the reboiler 2, and then enters the air cooling device. In order to ensure the normal control of the liquid level of the normal second stripping tower and the normal third stripping tower, the normal second line regulating valve and the normal third line regulating valve after the air cooling device are cancelled. Instead, a normal second line regulating valve is set after the normal second line heat exchanger, and a normal third line regulating valve is set after the normal third line heat exchanger.

[0044] In this embodiment, the heat source at the bottom of the light hydrocarbon recovery desorption tower is adjusted from the original normal one medium circulation oil line 31 (about 200°C) to the mixed low-temperature waste heat of the normal two-line pipeline and the normal three-line pipeline after heat exchange (about 130°C), and all the heat of the normal one medium circulation oil line 31 is used for raw oil heat exchange; and in order to avoid flow fluctuations that affect the stable operation of desorption, two valves are added to control the reboiler outlet temperature through the valves.

[0045] In this embodiment, since the heat source at the bottom of the light hydrocarbon recovery and desorption tower is adjusted from the original normal one medium circulation oil circuit 31 (about 200°C) to the mixed low-temperature waste heat of the normal two-line pipeline and the normal three-line pipeline after heat exchange (about 130°C), the reboiler at the bottom of the light hydrocarbon recovery and desorption tower is changed from the original DN600 to DN1000, the heat exchange area of ​​the reboiler is increased, and the utilization of the mixed low-temperature waste heat of the normal two-line pipeline and the normal three-line pipeline is increased.

[0046] In this embodiment, the Chang-1 intermediate oil circulation line 31 heats only the feedstock oil, using a 200°C heat source to directly heat the feedstock oil. This raises the feedstock oil temperature before entering the heater compared to the original design, thereby reducing the heater's gas consumption by approximately 0.15 t / h. Through this modification, the combined low-temperature waste heat from the Chang-2 and Chang-3 pipelines can meet the heat requirements of the reboiler in the light hydrocarbon recovery desorption tower, enabling stable operation of the light hydrocarbon recovery desorption tower. The temperature of the mixed diesel oil passing through the reboiler in the light hydrocarbon recovery desorption tower drops from 130°C to approximately 102°C. This also significantly reduces the load on the subsequent air cooling unit, saving electricity for air cooling, generating an annual benefit of approximately 3.4966 million yuan.

[0047] It should be noted that the original 1.0Mpa steam reboiler of the light hydrocarbon recovery desorption tower is retained in this embodiment. When the production plan changes and the mixed oil heat of the normal second line pipeline and the normal third line pipeline is insufficient, some 1.0Mpa steam can be used to supplement the insufficient heat. Daily control mainly uses the mixed low-temperature waste heat of the normal second line pipeline and the normal third line pipeline to heat the reboiler of the light hydrocarbon recovery desorption tower.

[0048] In this embodiment, in order to better utilize the heat of the circulating oil circuit 31 of Changyi, the heat exchange area of ​​the first heat exchanger and the second heat exchanger is changed from DN800 to DN1100, and the flow rate of Changyi pump is increased from the original 120t / h to 200t / h by replacing the high-flow pump.

[0049] Although the above description of the specific implementation methods of the present invention is combined with the accompanying drawings, it does not limit the scope of protection of the present invention. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present invention, various modifications or deformations that can be made by technical personnel in this field without creative work are still within the scope of protection of the present invention.

Claims

1. A combined atmospheric and vacuum light hydrocarbon recovery unit using low-temperature heat instead of high-temperature heat, characterized in that: The atmospheric pressure tower is connected to a normal-pressure oil circulation line, and a first heat exchanger and a second heat exchanger are connected in series on the normal-pressure oil circulation line; The atmospheric pressure tower is also connected to the normal second-line stripping tower and the normal third-line stripping tower respectively; the normal second-line stripping tower is connected to the normal second-line pipeline, the normal third-line stripping tower is connected to the normal third-line pipeline, and the normal second-line pipeline and the normal third-line pipeline are connected to the mixing pipeline; It also includes a light hydrocarbon recovery desorption tower, and the original 1.0Mpa steam reboiler of the light hydrocarbon recovery desorption tower is retained; A reboiler is added to the bottom of the light hydrocarbon recovery and desorption tower. Specifically, the cold source inlet and outlet ends of the reboiler are connected to the light hydrocarbon recovery and desorption tower, the heat source inlet end is connected to the mixing pipeline, the heat source outlet end is connected to the air cooling pipeline, the air cooling pipeline is connected to the air cooling device, and the air cooling device is connected to the tank area.

2. The atmospheric and vacuum light hydrocarbon recovery combined device using low-temperature heat instead of high-temperature heat as claimed in claim 1, characterized in that: The mixing pipeline is connected to the air cooling pipeline, and a second regulating valve is arranged between the mixing pipeline and the air cooling pipeline; and a first regulating valve is arranged between the mixing pipeline and the reboiler.

3. The atmospheric and vacuum light hydrocarbon recovery combined device using low-temperature heat instead of high-temperature heat as claimed in claim 1, characterized in that: A temperature sensor is provided between the reboiler and the light hydrocarbon recovery and desorption tower. Specifically, the temperature sensor is provided at the cold source outlet end of the reboiler.

4. The atmospheric and vacuum light hydrocarbon recovery combined device using low-temperature heat instead of high-temperature heat as claimed in claim 3, characterized in that: It also includes a control system, and the temperature sensor, the first regulating valve, and the second regulating valve are all connected to the control system.

5. The atmospheric and vacuum light hydrocarbon recovery combined device using low-temperature heat instead of high-temperature heat as claimed in claim 1, characterized in that: The heat source pipelines of the first heat exchanger and the second heat exchanger are connected to the Changyizhong circulating oil circuit, and the cold source pipeline is connected to the raw oil pipeline; a Changyizhong circulating pump is provided on the Changyizhong circulating oil circuit.

6. The atmospheric and vacuum light hydrocarbon recovery combined device using low-temperature heat instead of high-temperature heat as claimed in claim 5, characterized in that: The raw oil pipeline is provided with a plurality of heat exchangers including a first heat exchanger and a second heat exchanger; the raw oil pipeline is connected to a heating furnace, and the heating furnace is connected to an atmospheric pressure tower.

7. The atmospheric and vacuum light hydrocarbon recovery combined device using low-temperature heat instead of high-temperature heat as claimed in claim 1, characterized in that: The conventional second-line stripping tower is connected to the conventional second-line heat exchanger through a conventional second-line pipeline. A conventional second-line pump is arranged between the conventional second-line stripping tower and the conventional second-line heat exchanger. A conventional second-line regulating valve is arranged on the side of the conventional second-line heat exchanger away from the conventional second-line pump.

8. The atmospheric and vacuum light hydrocarbon recovery combined device using low-temperature heat instead of high-temperature heat as claimed in claim 1, characterized in that: The conventional three-line stripping tower is connected to the conventional three-line heat exchanger through a conventional three-line pipeline. A conventional three-line pump is arranged between the conventional three-line stripping tower and the conventional three-line heat exchanger. A conventional three-line regulating valve is arranged on the side of the conventional three-line heat exchanger away from the conventional three-line pump.

9. The atmospheric and vacuum light hydrocarbon recovery combined device using low-temperature heat instead of high-temperature heat as claimed in claim 8, characterized in that: The three-line heat exchanger or the two-line heat exchanger is connected to the three-line pipeline or the two-line pipeline through its heat source pipeline, and the cold source pipeline of the three-line heat exchanger and the two-line heat exchanger is connected to the raw oil pipeline.

10. The atmospheric and vacuum light hydrocarbon recovery combined device using low-temperature heat instead of high-temperature heat as claimed in claim 8, characterized in that: The normal three-line heat exchanger and the normal two-line heat exchanger are arranged in front of the first heat exchanger and the second heat exchanger.

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