Heat exchange assembly for hydrogenation of diesel and wax oil, and hydrogenation system

Abstract

The heat exchange assembly comprises a first heat exchanger, a second heat exchanger, a third heat exchanger, and a fourth heat exchanger. An inlet of a first hot medium passage is used for importing a first-stage reacting product, an inlet of a first cold medium passage is used for importing a first-stage reacting feedstock, and an outlet of the first cold medium passage is used for exporting the first-stage reacting feedstock after heat exchange. An inlet of a second hot medium passage communicates with an outlet of the first hot medium passage, an outlet of the second hot medium passage communicates with an inlet of a hot high separation tank, and an inlet of a second cold medium passage is used for importing bottom liquid of a stripping tower.

Description

BACKGROUND Technical Field

[0001] The present invention relates to a technical field of petroleum processing, and in particular to a heat exchange assembly for hydrogenation of diesel and wax oil and a hydrogenation system thereof.Description of Related Art

[0002] As shown in FIG. 1, the existing system for hydrogenation of diesel and wax oil adopts the traditional shell-and-tube heat exchanger and has a series of problems, such as low heat exchange efficiency, easy internal leakage, difficulty in equipment enlargement and the like. A larger heat exchange temperature difference needs to be ensured to separate cold and hot material streams at multiple temperatures so as to realize heat transfer and equipment manufacturability. As a result, a large number of heat exchange devices is adopted, the number of high-pressure pipes and the area of high-pressure sealing surfaces are increased, and a larger floor space is occupied, so that it is difficult for piping, and the total investment in device frame design and equipment cost is high.SUMMARY

[0003] A first technical problem to be solved by the present invention is to provide a heat exchange assembly for hydrogenation of diesel and wax oil to reduce equipment investment and improve heat exchange efficiency.

[0004] A second technical problem to be solved by the present invention is to provide a hydrogenation system using the heat exchange assembly.

[0005] To solve the first technical problem, the heat exchange assembly for hydrogenation of diesel and wax oil comprises: a first heat exchanger having a first hot medium passage and a first cold medium passage; a second heat exchanger having a second hot medium passage and a second cold medium passage; a third heat exchanger having a third hot medium passage and a third cold medium passage; and a fourth heat exchanger having a fourth hot medium passage and a fourth cold medium passage; wherein, each of the hot medium passages and cold medium passages has an inlet and an outlet; the inlet of the first hot medium passage is used for importing a first-stage reacting product, the inlet of the first cold medium passage is used for importing a first-stage reacting feedstock, the outlet of the first cold medium passage is used for exporting the first-stage reacting feedstock after heat exchange; the inlet of the second hot medium passage communicates with the outlet of the first hot medium passage, the outlet of the second hot medium passage communicates with the inlet of a hot high separation tank, the inlet of the second cold medium passage is used for importing bottom liquid of a stripping tower; the inlet of the third hot medium passage is used for importing a second-stage reacting product, the inlet of the third cold medium passage communicates with the outlet of the second cold medium passage, the outlet of the third cold medium passage communicates with a downstream device; the inlet of the fourth hot medium passage communicates with the outlet of the third hot medium passage, the outlet of the fourth hot medium passage communicates with the inlet of the hot high separation tank, the inlet of the fourth cold medium passage is used for importing a second-stage reacting feedstock, the outlet of the fourth cold medium passage is used for exporting the second-stage reacting feedstock after heat exchange.

[0006] The design and connection of the four heat exchangers of the present invention can effectively increase outlet temperature of the first-stage reacting feedstock and the second-stage reacting feedstock, thereby reducing the subsequent load of the high-pressure reaction heating furnace, that is, reducing the investment of the heating furnace in high pressure. Moreover, the heat exchange assembly of the present invention enables the low-temperature and low-pressure stripping tower bottom liquid preferentially exchanges heat with the high-pressure reacting product, so that the heat transfer temperature difference of the heat exchangers in the high pressure is increased, and the equipment investment for the heat exchangers in the high pressure is reduced. Furthermore, the second-stage reacting product exchanges heat with the stripping tower bottom liquid at first, which is beneficial to increase the temperature of the stripping tower bottom liquid. To sum up, the heat exchange assembly of the present invention decreases the number of heat exchangers and improves the heat exchange efficiency, so that the system occupies less floor space, it is convenient for piping, and the total investment is obviously reduced.

[0007] To facilitate adjustment according to actual operation, preferably, a first feeding pipeline which is used for conveying the first-stage reacting feedstock is connected to the inlet of the first cold medium passage of the first heat exchanger, a first feeding valve for controlling flow is disposed on the first feeding pipeline, and a first discharge pipeline which is used for conveying the first-stage reacting feedstock after heat exchange is connected to the outlet of the first cold medium passage; the heat exchange assembly further comprises a first bypass pipeline having a first bypass valve for controlling flow, the first bypass pipeline has an inlet and an outlet, the inlet of the first bypass pipeline communicates with the first feeding pipeline, and the outlet of the first bypass pipeline communicates with the first discharge pipeline

[0008] Preferably, the first feeding pipeline comprises a raw oil pipeline having an outlet for conveying raw oil and a hydrogen pipeline having an outlet for conveying hydrogen, and both the outlet of the raw oil pipeline and the outlet of the hydrogen pipeline communicate with the inlet of the first cold medium passage of the first heat exchanger; the inlet of the first bypass pipeline communicates with the raw oil pipeline, and the first feeding valve is disposed on the raw oil pipeline.

[0009] Preferably, the inlet of the second cold medium passage of the second heat exchanger communicates with a second feeding pipeline which is used for conveying the bottom liquid of the stripping tower, a second feeding valve for controlling flow is disposed on the second feeding pipeline, and the outlet of the second cold medium passage communicates with the inlet of the third cold medium passage of the third heat exchanger through a second discharge pipeline; the heat exchange assembly further comprises a second bypass pipeline and a second bypass valve disposed on the second bypass pipeline for controlling flow, the second bypass pipeline has an inlet and an outlet, the inlet of the second bypass pipeline communicates with the second feeding pipeline, and the outlet of the second bypass pipeline communicates with the second discharge pipeline.

[0010] Preferably, the outlet of the third cold medium passage of the third heat exchanger communicates to a third discharge pipeline; the heat exchange assembly further comprises a third bypass pipeline and a third bypass valve disposed on the third bypass pipeline for controlling flow, the third bypass pipeline has an inlet and an outlet, the inlet of the third bypass pipeline communicates with the second discharge pipeline, and the outlet of the second bypass pipeline communicates with the third discharge pipeline; and, a third feeding valve for controlling flow is disposed at a position on the second discharge pipeline between the inlet of the third bypass pipeline and the inlet of the third cold medium passage.

[0011] In above-stated technical schemes, preferably, the inlet of the second cold medium passage of the second heat exchanger communicates to a second feeding pipeline which is used for conveying the bottom liquid in the stripping tower, a second feeding valve for controlling flow is disposed on the second feeding pipeline, and the outlet of the third cold medium passage of the third heat exchanger communicates to a third discharge pipeline; the heat exchange assembly further comprises a large bypass pipeline and a large bypass valve disposed on the large bypass pipeline for controlling flow, the large bypass pipeline has an inlet and an outlet, the inlet of the large bypass pipeline communicates with the second feeding pipeline, and the outlet of the large bypass pipeline communicates with the third discharge pipeline.

[0012] In above-stated heat exchange assembly, the stripping tower bottom liquid or raw oil as a cold fluid passes through the cold medium passage and the bypass pipeline of the heat exchanger, but the factors such as site frame and pipeline gallery need to be taken into consideration in the design of the bypass pipeline and the bypass valve. The bypass pipeline is often long, and the bypass potential difference is large, resulting in a larger bypass pressure drop than a pressure drop of a fluid flowing through the heat exchange devices, so that the bypass pipeline cannot be regulated normally. As a result, the temperature of the cold fluid after heat exchange will be higher than a designed desired value, which will affect subsequent heat exchange network and operation. Moreover, if the temperature of the cold fluid after heat exchange is too high and exceeds the maximum temperature that can be borne by the pipeline, the leakage or even explosion of the pipeline will occur, resulting in potential safety hazards.

[0013] Therefore, in each above-stated technical solution, to improve the safety in use, preferably, at least one of the first bypass pipeline, the second bypass pipeline and the third bypass pipeline is disposed in the corresponding heat exchanger to form a bypass passage having an inlet and an outlet, and the outlet of the bypass passage communicates with the outlet of the cold medium passage in the corresponding heat exchanger. Thus, the bypass medium can be mixed with the cold fluid after heat exchange and then discharged, and the temperature of a mixed medium can be lower than that of the cold fluid after heat exchange, so that the safety problem caused by too high temperature of the cold fluid after heat exchange is solved.

[0014] Preferably, each of the heat exchangers is a winding pipeline type heat exchanger and comprises a shell and the cold medium passage serves as a shell pass or tube pass; a cold medium inlet pipeline communicating with the inlet of the cold medium passage, a cold medium outlet pipeline communicating with the outlet of the cold medium passage and a bypass medium inlet pipeline communicating with the inlet of the bypass passage are respectively disposed on the shell; the outlet of the bypass passage communicates with the outlet of the cold medium passage, and, the cold medium outlet pipeline is used for exporting a mixed medium obtained after mixing a cold medium with a bypass medium.

[0015] Preferably, the bypass passage and the cold medium passage extend in a same direction, and the inlet of the bypass passage is adjacent relative to the inlet of the cold medium passage.

[0016] Preferably, the bypass passage is disposed in the cold medium passage.

[0017] To improve structure compactness of the heat exchange assembly, preferably, the bypass passage extends vertically and is located at a center of the shell defined as a central cylinder inside the shell, a heat exchange tube in the tube pass is spirally wound around the bypass passage.

[0018] In the above-stated technical solutions, to avoid a backflow of the medium in the bypass passage without affecting the normal transportation of the bypass medium, preferably, a switch capable of switching off or on a path in the bypass passage is disposed on the bypass passage at a position adjacent to the outlet of the bypass passage.

[0019] Preferably, the switch comprises a valve sheet and an elastic element, the valve sheet is rotatably disposed in the bypass passage to switch off or on the path of the bypass passage; the elastic element urges the valve sheet to rotate so as to switch off the path of the bypass passage; when the bypass medium flows from the inlet to the outlet of the bypass passage, the valve sheet is capable of overcoming an elastic force of the elastic element so as to rotate to switch on the path of the bypass passage.

[0020] Accordingly, the valve sheet can prevent the bypass medium to flow back to the bypass passage. When the bypass medium normally passes through the bypass passage, the bypass medium can flush the valve sheet and open the path in the bypass passage, without affecting the normal transportation of the bypass medium.

[0021] Preferably, a plate having a through hole is transversely arranged in the bypass passage, the valve sheet is rotatably disposed on the plate, and the valve sheet is located downstream of the plate in a flow direction of the bypass medium from the inlet to the outlet of the bypass passage to open or close the through hole; when the valve sheet opens the through hole, the path of the bypass passage is switched on, and when the valve sheet closes the through hole, the path of the bypass passage is switched off.

[0022] Preferably, an edge of the valve sheet is rotatably connected to the plate through a rotating shaft, and the elastic element is a torsion spring sleeved around the rotating shaft.

[0023] Preferably, the heat exchange tube has a top end and a bottom end, two tube plates respectively for supporting the top end and the bottom end of the heat exchange tube are disposed on the shell, and at least one of the inlet and the outlet of the bypass passage which is constrained on the tube plate is movable upward and downward relative to the corresponding tube plate.

[0024] To solve the second technical problem, the hydrogenation system comprises a fractionating tower having a feeding port, a stripping tower having a bottom and a feeding port, a heating furnace having an inlet and an outlet, a hot high separation tank having an inlet, an outlet and a top, a first heat exchange device having a hot medium passage and a cold medium heat exchange passage, and the above-stated heat exchange assembly; wherein, the stripping tower has an outlet on the bottom of the stripping tower , the inlet of the second cold medium passage of the second heat exchanger communicates with the outlet of the stripping tower; the outlet of the second hot medium passage of the second heat exchanger and the outlet of the fourth hot medium passage of the fourth heat exchanger respectively communicate with the inlet of the hot high separation tank; the outlet at the top of the hot high separation tank communicates with an inlet of the hot medium passage of the first heat exchange device; an inlet of the cold medium heat exchange passage of the first heat exchange device is connected to a stripping tower feeding pipeline which is used for conveying a stripping tower feedstock, and, an outlet of the cold medium heat exchange passage of the first heat exchange device communicates with the feeding port of the stripping tower; and the outlet of a third cold medium passage of a third heat exchanger communicates with the inlet of the heating furnace, and the outlet of the heating furnace communicates with the feeding port of the fractionating tower.

[0025] Preferably, the hydrogenation system further comprises a second heat exchange device having a cold medium heat exchange passage and a hot medium heat exchange passage; an inlet of the cold medium heat exchange passage of the second heat exchange device communicates with the outlet of the third cold medium passage of the third heat exchanger, an outlet of the cold medium heat exchange passage of the second heat exchange device communicates with the inlet of the heating furnace, an inlet of the hot medium heat exchange passage of the second heat exchange device communicates with an outlet at the bottom of the fractionating tower. Thus, the stripping tower bottom liquid can be heated by using the unconverted oil on the bottom of the fractionating tower, and a load of the heating furnace before feeding the fractionating tower can be reduced.

[0026] Preferably, the hydrogenation system further comprises a third heat exchange device, an inlet of a hot medium heat exchange passage of the third heat exchange device communicates with an outlet of the hot medium heat exchange passage of the second heat exchange device, an inlet of a cold medium heat exchange passage of the third heat exchange device communicates with a water supply pipeline which is used for conveying water.

[0027] Preferably, the first heat exchange device has three cold medium heat exchange passages, each cold medium heat exchange passage has an inlet and an outlet, the inlet of the first cold medium heat exchange passage communicates with a hydrogen supply pipeline which is used for conveying hydrogen, the inlet of the second cold medium heat exchange passage communicates with the stripping tower feeding pipeline , the inlet of the third cold medium heat exchange passage communicates with a water delivery pipeline which is used for conveying water; the first cold medium heat exchange passage, the second cold medium heat exchange passage and the third cold medium heat exchange passage are arranged alternatively in a flow direction of a hot high-fraction gas in the hot medium passage of the first heat exchange device. Accordingly, the heat of the hot high-fraction gas can be fully utilized.

[0028] Compared with the prior art, the heat exchange assembly and the hydrogenation system of the present invention have the following advantages. The design and connection of the four heat exchangers in the present invention can effectively increase outlet temperature of the first-stage reacting feedstock and the second-stage reacting feedstock, thereby reducing the subsequent load of the high-pressure reaction heating furnace, that is, reducing the investment of the heating furnace in high pressure. Moreover, the heat exchange assembly of the present invention enables the low-temperature and low-pressure stripping tower bottom liquid preferentially exchanges heat with the high-pressure reacting product, so that the heat transfer temperature difference of the heat exchangers in the high pressure is increased, and the equipment investment for the heat exchangers in the high pressure is reduced. Furthermore, the second-stage reacting product exchanges heat with the stripping tower bottom liquid at first, so that it is beneficial to increase the temperature of the stripping tower bottom liquid. To sum up, the heat exchange assembly of the present invention decreases the number of heat exchangers and improves the heat exchange efficiency, so that the hydrogenation system occupies less floor space, it is convenient for distributing the pipelines, and the total investment is obviously reduced.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Fig. 1 is a schematic diagram of a hydrogenation system in the prior art; Fig. 2 is a schematic diagram of a hydrogenation system according to Embodiment 1 of the present invention; Fig. 3 is a schematic diagram of a heat exchange assembly according to Embodiment 2 of the present invention (which replaces a part within the dashed line in Fig. 2); Fig. 4 is a schematic diagram of a heat exchange assembly according to Embodiment 3 of the present invention (which replaces a part within the dashed line in Fig. 2); Fig. 5 is a schematic diagram of a heat exchange assembly according to Embodiment 4 of the present invention (which replaces a part within the dashed line in Fig. 2); Fig. 6 is a sectional view of a heat exchanger according to Embodiment 4 of the present invention; a schematic diagram Fig. 7 is a sectional view of a heat exchanger according to Embodiment 5 of the present invention; Fig. 8 is a sectional view of a heat exchanger according to Embodiment 6 of the present invention; Fig. 9 is an enlarged view of a part-A in Fig. 8; Fig. 10 is a sectional view of the part-A in Fig. 8. DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention will be further described below in detail by embodiments with reference to the accompanying drawings.Embodiment 1:

[0031] Fig. 2 shows a preferred Embodiment 1 of a heat exchange assembly for hydrogenation of diesel and wax oil and a hydrogenation system of the present invention. The hydrogenation system comprises the heat exchange assembly, a fractionating tower 200 having a feeding port, a stripping tower 300 having a bottom and a feeding port, a heating furnace 400 having an inlet and an outlet, a hot high separation tank 500 having an inlet, an outlet and a top, a first heat exchange device 600 having a hot medium passage and a cold medium heat exchange passage, a second heat exchange device 700 having a cold medium heat exchange passage and a hot medium heat exchange passage and a third heat exchange device 800 having a hot medium heat exchange passage and a cold medium heat exchange passage.

[0032] The heat exchange assembly comprises a first heat exchanger 110, a second heat exchanger 120, a third heat exchanger 130 and a fourth heat exchanger 140.

[0033] The first heat exchanger 110 has a first hot medium passage and a first cold medium passage. Each of the first hot medium passage and the first cold medium passage has an inlet and an outlet. The inlet of the first hot medium passage is used for importing a first-stage reacting product, the inlet of the first cold medium passage is used for importing a first-stage reacting feedstock, the outlet of the first cold medium passage is used for exporting the first-stage reacting feedstock after heat exchange, and the outlet of the first cold medium passage communicates with a first-stage reacting feedstock heating furnace.

[0034] The second heat exchanger 120 has a second hot medium passage and a second cold medium passage. Each of the second hot medium passage and the second cold medium passage has an inlet and an outlet. The inlet of the second hot medium passage communicates with the outlet of the first hot medium passage of the first heat exchanger 110, the outlet of the second hot medium passage communicates with an inlet of a hot high separation tank 500, and the inlet of the second cold medium passage communicates with an outlet on the bottom of the stripping tower 300.

[0035] The third heat exchanger 130 has a third hot medium passage and a third cold medium passage. Each of the third hot medium passage and the third cold medium passage has an inlet and an outlet. The inlet of the third hot medium is used for importing a second-stage reacting product, and the inlet of the third cold medium passage communicates with the outlet of the second cold medium passage of the second heat exchanger 120.

[0036] The fourth heat exchanger 140 has a fourth hot medium passage and a fourth cold medium passage. Each of the fourth hot medium passage and the fourth cold medium passage has an inlet and an outlet. The inlet of the fourth hot medium passage communicates with the outlet of the third hot medium passage of the third heat exchanger 130; the outlet of the fourth hot medium passage communicates with the inlet of the hot high separation tank 500; the inlet of the fourth cold medium passage is used for importing a second-stage reacting feedstock; the outlet of the fourth cold medium passage is used for exporting the second-stage reacting feedstock after heat exchange; and the outlet of the fourth cold medium passage is used for communicating with a second-stage reacting feedstock heating furnace.

[0037] The first heat exchange device 600 has a hot medium passage having an inlet and an outlet and three cold medium heat exchange passages each having an inlet and an outlet. The inlet of the hot medium passage of the first heat exchange device 600 communicates with the outlet at the top of the hot high separation tank 500, and the outlet of the hot medium passage of the first heat exchange device 600 communicates with a downstream air cooler. The inlet of a first cold medium heat exchange passage of the three cold medium heat exchange passages communicates with a hydrogen supply pipeline 610 which is used for conveying hydrogen. The inlet of a second cold medium heat exchange passage communicates with a stripping tower feeding pipeline 310 which is used for conveying a stripping tower feedstock. The inlet of a third cold medium heat exchange passage communicates with a water delivery pipeline 620 which is used for conveying water. The first cold medium heat exchange passage, the second cold medium heat exchange passage and the third cold medium heat exchange passage are arranged alternatingly in a flow direction of a hot high-fraction gas in the hot medium passage of the first heat exchange device 600.

[0038] The stripping tower 300 is a hydrogen sulfide removal stripping tower, the feeding port of which communicates with the outlet of the second cold medium heat exchange passage of the first heat exchange device 600. The stripping tower 300 has a steam inlet on a lower portion of the stripping tower 300.

[0039] The outlet of the third cold medium passage of the third heat exchanger 130 communicates with the feeding port of the fractionating tower 200 successively through the second heat exchange device 700 and the heating furnace 400. Specifically, the cold medium heat exchange passage of the second heat exchange device 700 has an inlet and an outlet. An inlet of the cold medium heat exchange passage of the second heat exchange device 700 communicates with the outlet of the third cold medium passage of the third heat exchanger 130, and the outlet of the cold medium heat exchange passage of the second heat exchange device 700 communicates with the inlet of the heating furnace 400. The output end of the heating furnace 400 communicates with the feeding port of the fractionating tower 200. The hot medium heat exchange passage of the second heat exchange device 700 has an inlet and an outlet. The inlet of the hot medium heat exchange passage of the second heat exchange device 700 communicates with an outlet at the bottom of the fractionating tower 200.

[0040] An inlet of the hot medium heat exchange passage of the third heat exchange device 800 communicates with the outlet of the hot medium heat exchange passage of the second heat exchange device 700, and an inlet of the cold medium heat exchange passage of the third heat exchange device 800 communicates with a water supply pipeline 810 which is used for conveying water.

[0041] The heat exchange process in this embodiment will be described below.

[0042] The first-stage reacting product successively passes through the first hot medium passage of the first heat exchanger 110 and the second hot medium passage of the second heat exchanger 120 and is then imported into the hot high separation tank 500. The first-stage reacting product before entering the first hot medium passage of the first heat exchanger 110 has a temperature of 425°C and a pressure of 17.08 MPa, and the first-stage reacting product exported from the second hot medium passage of the second heat exchanger 120 has a temperature of 255°C. Meanwhile, the first-stage reacting feedstock (with a temperature of 207°C and a pressure of 19.54 MPa) is imported into the first cold medium passage of the first heat exchanger 110 to exchange heat with the first-stage reacting product, and the first-stage reacting feedstock after heat exchange (with a temperature of 405°C) is conveyed to the first-stage reacting feedstock heating furnace.

[0043] The second-stage reacting product successively passes through the third hot medium passage of the third heat exchanger 130 and the fourth hot medium passage of the fourth heat exchanger 140 and is then imported into the hot high separation tank 500. The second-stage reacting product before entering the third hot medium passage of the third heat exchanger 130 has a temperature of 403°C and a pressure of 16.8 MPa, and the second-stage reacting product exported from the fourth hot medium passage of the fourth heat exchanger 140 has a temperature of 255°C. Meanwhile, the second-stage reacting feedstock (with a temperature of 216°C and a pressure of 18.3 MPa) is imported into the fourth cold medium passage of the fourth heat exchanger 140 to exchange heat with the second-stage reacting product, and the second-stage reacting feedstock after heat exchange (with a temperature of 380°C) is conveyed to the second-stage reacting feedstock heating furnace.

[0044] The hot high-fraction gas (with a pressure of 16.4 MPa) exported from the top of the hot high separation tank 500 passes through the hot medium passage of the first heat exchange device 600 and is then exported to the air cooler. The hot high-fraction gas exported from the hot medium passage of the first heat exchange device 600 has a temperature of 90°C. Meanwhile, hydrogen enters the first cold medium heat exchange passage of the first heat exchange device 600 through the hydrogen supply pipeline 610 to exchange heat with the hot high-fraction gas. The hydrogen before heat exchange has a temperature of 87°C, and the hydrogen after heat exchange has a temperature of 200.7°C. The stripping tower feedstock enters the second cold medium heat exchange passage of the first heat exchange device 600 through the stripping tower feeding pipeline 310 to exchange heat with the hot high-fraction gas. The stripping tower feedstock before heat exchange has a temperature of 49°C, and the stripping tower feedstock after heat exchange has a temperature of 166.6°C. Water enters the third cold medium heat exchange passage of the first heat exchange device 600 through the water delivery pipeline 620 to exchange heat with the hot high-fraction gas. The water before heat exchange has a temperature of 70°C, and the water after heat exchange has a temperature of 95°C.

[0045] The stripping tower bottom liquid exported from the bottom of the stripping tower 300 successively passes through the second cold medium passage of the second heat exchanger 120, the third cold medium passage of the third heat exchanger 130, the cold medium heat exchange passage of the second heat exchange device 700 and the heating furnace 400 and is then imported into the fractionating tower 200. The stripping tower bottom liquid exported from the bottom of the stripping tower 300 has a temperature of 213°C and a pressure of 3.0 MPa. The stripping tower bottom liquid exported from the second cold medium passage of the second heat exchange device 120 has a temperature of 276°C. The stripping tower bottom liquid exported from the third cold medium passage of the third heat exchanger 130 has a temperature of 282.4°C. The stripping tower bottom liquid exported from the cold medium heat exchange passage of the second heat exchange device 700 has a temperature of 307.5°C.

[0046] Meanwhile, an unconverted oil exported from the bottom of the fractionating tower 200 successively passes through the hot medium heat exchange passage of the second heat exchange device 700 and the hot medium heat exchange passage of the third heat exchange device 800 and is then exported, wherein the unconverted oil exported from the bottom of the fractionating tower 200 has a temperature of 354°C and a pressure of 1.6 MPa. The unconverted oil exported from the hot medium heat exchange passage of the second heat exchange device 700 has a temperature of 287.5°C, and the unconverted oil exported from the hot medium heat exchange passage of the third heat exchange device 800 has a temperature of 240°C. Meanwhile, water at 70°C enters the cold medium passage of the third heat exchange device 800 through the water supply pipeline 810 and is then exported after exchanging heat with the unconverted oil, wherein the exported water has a temperature of 95°C.

[0047] In this embodiment, the outlet temperature of both the first-stage reacting feedstock and the second-stage reacting feedstock is effectively increased, so that a subsequent load of the high-pressure reaction heating furnace is reduced, that is, the investment of the heating furnace in the high pressure is reduced.

[0048] Moreover, a temperature rise of 10°C to 15°C is redefined for the reacting feedstock heating furnace, which is advantageous for the adjustment of operating condition changes. In addition, the large bypass for the raw oil and the stripping tower bottom liquid makes the adjustment of the whole system more convenient and effective.

[0049] Compared with the prior art, in this embodiment, a designed load of the low-pressure heating furnace 400 needs to be increased, but the cost increase ratio is not high due to low pressure.

[0050] Furthermore, in this embodiment, by exchanging heat between the hot high-fraction gas and the stripping tower feedstock, the temperature of the stripping tower feedstock is increased, and the consumption of the stripping tower steam is effectively reduced.

[0051] Due to the design of the second heat exchange device 700, the temperature difference of heat exchange between the unconverted oil and the stripping tower bottom liquid is reduced, and the load of the heating furnace 400 before feeding the fractionating tower 200 is reduced.

[0052] Each of the first to fourth heat exchangers is a winding pipeline type heat exchanger.Embodiment 2:

[0053] Fig. 3 shows a preferred Embodiment 2 of a heat exchange assembly for hydrogenation of diesel and wax oil and a hydrogenation system of the present invention. This embodiment is basically the same as Embodiment 1, while differs from Embodiment 1 in that: an inlet of the second cold medium passage of the second heat exchanger 120 communicates with a second feeding pipeline 121 which is used for conveying the bottom liquid of the stripping tower. A second feeding valve 122 for controlling flow is disposed on the second feeding pipeline 121, and the outlet of the second cold medium passage communicates with the inlet of the third cold medium passage of the third heat exchanger 130 through a second discharge pipeline 123; the outlet of the third cold medium passage of the third heat exchanger 130 communicates to a third discharge pipeline 133.

[0054] The heat exchange assembly further comprises a second bypass pipeline 124 and a second bypass valve 125 disposed on the second bypass pipeline 124 for controlling flow. The second bypass pipeline 124 has an inlet and an outlet. The inlet of the second bypass pipeline 124 communicates with the second feeding pipeline 121, and the outlet of the second bypass pipeline 124 communicates with a section of the second discharge pipeline 123 adjacent to the outlet of the second cold medium passage of the second heat exchanger 120.

[0055] The heat exchange assembly further comprises a third bypass pipeline 134 and a third bypass valve 135 disposed on the third bypass pipeline 134 for controlling flow. The third bypass pipeline 134 has an inlet and an outlet. The inlet of the third bypass pipeline 134 communicates with a section of the second discharge pipeline 123 adjacent to the inlet of the third cold medium passage of the third heat exchanger 130.

[0056] The arrangement of each bypass pipeline in this embodiment is convenient for the adjustment of the temperature of a medium in the corresponding discharge pipeline.Embodiment 3:

[0057] Fig. 4 shows a preferred Embodiment 3 of a heat exchange assembly for hydrogenation of diesel and wax oil and a hydrogenation system of the present invention. This embodiment is basically the same as Embodiment 1, while differs from Embodiment 1 in that: a first discharge pipeline 113 which is used for conveying a first-stage reacting feedstock after heat exchange is connected to an outlet of a first cold medium passage of a first heat exchanger 110. A first feeding pipeline 111 which is used for conveying the first-stage reacting feedstock is connected to an inlet of the first cold medium passage of the first heat exchanger 110. The first feeding pipeline 111 comprises a raw oil pipeline 1111 having an outlet for conveying raw oil and a hydrogen pipeline 1112 having an outlet for conveying hydrogen, and both the outlet of the raw oil pipeline 1111 and the outlet of the hydrogen pipeline 1112 communicate with the inlet of the first cold medium passage of the first heat exchanger 110. A first feeding valve 112 is disposed on the raw oil pipeline 1111 for controlling flow.

[0058] The heat exchange assembly further comprises a first bypass pipeline 114 having a first bypass valve 115 for controlling flow. The first bypass pipeline 114 has an inlet and an outlet, the inlet of the first bypass pipeline 114 communicates with the first feeding pipeline 111, and the outlet of the first bypass pipeline 114 communicates with the first discharge pipeline 113.

[0059] Meanwhile, the inlet of the second hot medium passage of the second heat exchanger 120 communicates with the second feeding pipeline 121 which is used for conveying the bottom liquid of the stripping tower. A second feeding valve 122 for controlling flow is disposed on the second feeding pipeline 121. The outlet of the third hot medium passage of the third heat exchanger 130 communicates with a third discharge pipeline 133.

[0060] The heat exchange assembly further comprises a large bypass pipeline 144 and a large bypass valve 145 for controlling flow is disposed on the large bypass pipeline 144. The large bypass pipeline 144 has an inlet and an outlet. The inlet of the large bypass pipeline 144 communicates with the second feeding pipeline 121, and the outlet of the large bypass pipeline 144 communicates with the third discharge pipeline 133.

[0061] Similarly, the arrangement of each bypass pipeline in this embodiment is convenient for the adjustment of the temperature of a medium in the corresponding discharge pipeline.Embodiment 4:

[0062] Figs. 5-6 show a preferred Embodiment 4 of a heat exchange assembly for hydrogenation of diesel and wax oil and a hydrogenation system of the present invention. This embodiment is basically the same as Embodiment 2, while differs from Embodiment 2 in that: a first discharge pipeline 113 which is used for conveying a first-stage reacting feedstock after heat exchange is connected to an outlet of the first cold medium passage of a first heat exchanger 110. A first feeding pipeline 111 which is used for conveying the first-stage reacting feedstock is connected to an inlet of the first cold medium passage of the first heat exchanger 110. The first feeding pipeline 111 comprises a raw oil pipeline 1111 having an outlet for conveying raw oil and a hydrogen pipeline 1112 having an outlet for conveying hydrogen, and both the outlet of the raw oil pipeline 1111 and the outlet of the hydrogen pipeline 1112 communicate with the inlet of the first cold medium passage of the first heat exchanger 110. The first feeding valve 112 is disposed on the raw oil pipeline 1111 (not shown in Fig. 5, referring to Fig. 4 instead).

[0063] The heat exchange assembly further comprises a first bypass pipeline 114 having a first bypass valve 115 for controlling flow. The first bypass pipeline 114 has an inlet and an outlet. The inlet of the first bypass pipeline 114 communicates with the raw oil pipeline 1111, and the outlet of the first bypass pipeline 114 communicates with the first discharge pipeline 113.

[0064] Meanwhile, in this embodiment, the first bypass pipeline 114, the second bypass pipeline 124 and the third bypass pipeline 134 are respectively arranged in the corresponding heat exchanger to form three bypass passages 2 each having an inlet and an outlet (as shown in Fig. 6), and an outlet of each bypass passage 2 communicates with an outlet of a cold medium passage in the corresponding heat exchanger. Specifically: as shown in Fig. 6, each heat exchanger is a winding pipeline type heat exchanger, and comprises a shell 1 having a top end, a bottom end, an upper portion and a lower portion, a bypass passage 2 and a heat exchange tube 3.

[0065] The shell 1 is a cylinder arranged vertically, and a cold medium inlet pipeline 100a and a cold medium outlet pipeline 100b are respectively disposed at the top end and the bottom end of the shell 1. Meanwhile, a shell-pass inlet pipeline 1a for importing a hot medium is disposed at the lower portion of a sidewall of the shell 1, a shell-pass outlet pipeline 1b for exporting the hot medium is disposed at the upper portion of the sidewall of the shell 1. Each of the shell-pass inlet pipeline 1a and the shell-pass outlet pipeline 1b communicates with an inside of the shell 1 (which is defined as the shell pass 101 of the heat exchanger).

[0066] The bypass passage 2 having an upper end and a lower end extends vertically, and is located at a center of the shell 1 as a central cylinder. Two tube plates 5 are disposed in the shell 1 corresponding to two ends of the bypass passage 2. The lower end of the bypass passage 2 is located above the corresponding tube plate 5, and the both are connected to each other. A lower port of the bypass passage 2 communicates with the cold medium outlet pipeline 100b. The upper end of the bypass passage 2 is located below the corresponding tube plate 5, and the both are connected with each other in an insertion manner, so that the upper end of the bypass passage 2 is movable upward and downward relative to the corresponding tube plate 5. Meanwhile, the upper end of the bypass passage 2 communicates with the cold medium inlet pipeline 100a.

[0067] The heat exchange tube 3 defined as the tube pass 102 of the heat exchanger (that is, the cold medium passage) is spirally wound around the bypass passage 2. The heat exchange tube 3 has an upper end and a lower end. The upper and lower ends of the heat exchange tube 3 are respectively supported on the corresponding tube plate 5 and respectively communicate with the corresponding cold medium inlet pipeline 100a and the cold medium outlet 100b.

[0068] Meanwhile, a bypass medium inlet pipeline 2a having an inlet and an outlet is disposed at a position on the upper portion of the shell 1 adjacent to the cold medium inlet pipeline 100a. A part of the bypass medium inlet pipeline 2a passes downward through the corresponding tube plate 5 and extends into an upper port of the bypass passage 2 (which is defined as an inlet of the bypass passage 2) to communicate with the bypass passage 2. A lower port of the bypass passage 2 (which is defined as an outlet of the bypass passage 2) communicates with a lower port of the heat exchange tube 3. The cold medium outlet pipeline 100b is used for exporting a mixed medium obtained after mixing a cold medium with a bypass medium.

[0069] In the operation process, a hot medium is imported into the shell 1 from the shell-pass inlet pipeline 1a, then exchanges heat with a cold medium and is exported from the shell-pass outlet pipeline 1b. A bypass medium is imported into the bypass passage 2 from the bypass medium inlet pipeline 2a, and the cold medium is imported into the heat exchange tube 3 from the cold medium inlet pipeline 100a, then exchanges heat with the hot medium, flows out of the heat exchange tube 3 and is mixed with the bypass medium and exported from the cold medium outlet pipeline 100b.

[0070] Similarly, the arrangement of each bypass pipeline in this embodiment is convenient for the adjustment of a temperature of a medium in the corresponding discharge pipeline.Embodiment 5:

[0071] Fig. 7 shows a preferred Embodiment 5 of a heat exchange assembly for hydrogenation of diesel and wax oil and a hydrogenation system of the present invention. This embodiment is basically the same as Embodiment 4, while differs from Embodiment 4 in that: a shell 1 is a cylinder arranged vertically, and a cold medium outlet pipeline 100b and a cold medium inlet pipeline 100a are disposed at an upper and lower ends of the shell 1, respectively. Meanwhile, a shell-pass inlet pipeline 1a for importing a hot medium is disposed at an upper portion of a sidewall of the shell 1, a shell-pass outlet pipeline 1b for exporting the hot medium is disposed at a lower portion of the sidewall of the shell 1. Each of the shell-pass inlet pipeline 1a and the shell-pass outlet pipeline 1b communicates with an inside of the shell 1 (which is defined as a shell pass 101 of the heat exchanger).

[0072] The bypass passage 2 having an upper end and a lower end extends vertically, and is located in a center of the inside of the shell 1 as a central cylinder. Two tube plates 5 are disposed in the shell 1 corresponding to two ends of the bypass passage 2. The lower end of the bypass passage 2 is located above the corresponding tube plate 5, and the both are connected to each other. A lower port of the bypass passage 2 communicates with the cold medium outlet pipeline 100b. The upper end of the bypass passage 2 is located below the corresponding tube plate 5, and the both are connected with each other in an insertion manner, so that the upper end of the bypass passage 2 is movable upward and downward relative to the corresponding tube plate 5. Meanwhile, the upper end of the bypass passage 2 communicates with the cold medium inlet pipeline 100a.

[0073] The heat exchange tube 3 defined as the tube pass 102 of the heat exchanger (that is, the cold medium passage) is spirally wound around the bypass passage 2. The heat exchange tube 3 has an upper end and a lower end. The upper and lower ends of the heat exchange tube 3 are respectively supported on the corresponding tube plate 5 and respectively communicate with the corresponding cold medium outlet pipeline 100b and the cold medium inlet 100a.

[0074] Meanwhile, a bypass medium inlet pipeline 2a having an inlet and an outlet is disposed at a position on an upper portion of the shell 1 adjacent to the cold medium inlet pipeline 100a. A part of the bypass medium inlet pipeline 2a passes downward through the corresponding tube plate 5 and extends into a lower port of the bypass passage 2 (which is defined as an inlet of the bypass passage 2) to communicate with the bypass passage 2. An upper port of the bypass passage 2 (which is defined as an outlet of the bypass passage 2) communicates with an upper port of the heat exchange tube 3. The cold medium outlet pipeline 100b is used for exporting a mixed medium obtained after mixing a cold medium with a bypass medium.

[0075] In the operation process, a hot medium is imported into the shell 1 from the shell-pass inlet pipeline 1a, then exchanges heat with a cold medium and is exported from the shell-pass outlet pipeline 1b. A bypass medium is imported into the bypass passage 2 from the bypass medium inlet pipeline 2a, and the cold medium is imported into the heat exchange tube 3 from the cold medium inlet pipeline 100a, then exchanges heat with the hot medium, flows out of the heat exchange tube 3 and is mixed with the bypass medium and exported from the cold medium outlet pipeline 100b.Embodiment 6:

[0076] Figs. 8-10 show a preferred Embodiment 6 of a heat exchange assembly for hydrogenation of diesel and wax oil and a hydrogenation system of the present invention. This embodiment is basically the same as Embodiment 4, while differs from Embodiment 4 in that:

[0077] The winding pipeline type heat exchanger comprises a shell 1, a bypass passage 2, a switch element and a heat exchanger tube 3.

[0078] The shell 1 is a cylinder arranged vertically, and a tube-pass inlet pipeline for importing a tube-pass medium and a tube-pass outlet pipeline for exporting the tube-pass medium are disposed at upper and lower ends of the shell 1, respectively. Meanwhile, a cold medium inlet pipeline 100a for importing a cold medium is disposed at a lower portion of a sidewall of the shell 1, a cold medium outlet pipeline 100b for exporting the cold medium is disposed at an upper portion of the sidewall of the shell 1. Each of the cold medium inlet pipeline 100a and the cold medium outlet pipeline 100b communicates with an inside of the shell 100 (which is defined as a shell passe 101 of the heat exchanger, that is, the cold medium passage).

[0079] The bypass passage 2 having an upper end and a lower end extends vertically, and is located in a center of the inside of the shell 1 as a central cylinder. Two tube plates 5 are disposed in the shell 1 corresponding to two ends of the bypass passage 2. The lower end of the bypass passage 2 (which is defined as an inlet end of the bypass passage 2) is located above the corresponding tube plate 5, and the both are connected to each other. An upper end of the bypass passage 2 (which is defined as an outlet end of the bypass passage 2) is located below the corresponding tube plate 5, and the both are connected with each other in an insertion manner, so that the upper end of the bypass passage 2 is movable upward and downward relative to the corresponding tube plate 5.

[0080] The heat exchange tube 3 defined as the tube pass 102 of the heat exchanger is spirally wound around the bypass passage 2. The heat exchange tube 3 has an upper end and a lower end. The upper and lower ends of the heat exchange tube 3 are respectively supported on the corresponding tube plate 5 and respectively communicate with the corresponding tube-pass inlet pipeline and tube-pass outlet pipeline.

[0081] Meanwhile, a bypass medium inlet pipeline 2a is disposed at a position on the lower portion of the sidewall of the shell 1 corresponding to the lower end of the bypass passage 2. A part of the bypass medium inlet pipeline 2a transversely extends into the shell 1 and communicates with the bypass passage 2. The bypass passage 2 has a fluid outlet 22 at the upper end of the bypass passage 2 (which is defined as the outlet end of the bypass passage 2). This fluid outlet 22 faces the cold medium outlet pipeline 100a, and the both are communicated with each other through an internal space of the shell 1. That is, the cold medium outlet pipeline 100b exports a mixed medium obtained after mixing a cold medium with a bypass medium.

[0082] In the operation process, a hot medium is imported into the heat exchange tube 3 from the tube-pass inlet pipeline, then exchanges heat with the cold medium and flows out of the heat exchange tube 3. The bypass medium is imported into the bypass passage 2 from the bypass medium inlet pipeline 2a. A cold medium is imported into the shell 1 from the cold medium inlet pipeline 100a, then exchanges heat with the hot medium and is mixed with a bypass medium and exported from the cold medium outlet pipeline 100b.

[0083] The switch element is disposed in the bypass passage 2 adjacent to the upper end of the bypass passage 2 and located below the fluid outlet 22. Specifically, a plate 25 having a through hole 250 is transversely arranged at a position in the bypass passage 2 corresponding to the switch element. The switch comprises a valve sheet 23 and an elastic element 24. An edge of one side of the valve sheet 23 is rotatably connected to the plate 25 through a rotating shaft 231 to open or close the through hole 250. When the valve sheet 23 opens the through hole 250, the path of the bypass passage 2 is switched on, and when the valve sheet 23 closes the through hole 250, the path of the bypass passage 2 is switched off. The elastic element 24 is a torsion spring sleeved around the rotating shaft 231, urging the valve sheet 23 to close the through hole 250. Meanwhile, when a bypass medium flows from down to up in the bypass passage 2, the valve sheet 23 is disposed to overcome an elastic force of the elastic element 24 to rotate to a state of opening the path. Thus, the valve sheet 23 can only open the through hole 250 when the bypass medium flowing from down to up, so that the path in the bypass passage 2 is switched on.

[0084] It should be noted that in the specification and claims of the present invention, directional terms such as "front," "rear," "upper," "lower," "left," "right," "side," "top," and "bottom" are used to describe various exemplary structural parts and components of the invention. However, these terms are employed herein solely for the purpose of facilitating explanation and are defined based on the exemplary orientations illustrated in the accompanying drawings. Since the disclosed embodiments of the present invention may be arranged in different orientations, these directional terms are used for illustrative purposes only and should not be construed as limiting. For example, "upper" and "lower" are not necessarily restricted to directions opposite to or aligned with the direction of gravity.

[0085] In addition, the term "vertical" is used in the specification and claims of the present invention to mean substantially along the up-down direction, and is not limited to a strictly vertical orientation; it may also include slight deviations from the exact vertical direction.

Claims

1. A heat exchange assembly for hydrogenation of diesel and wax oil, comprising: a first heat exchanger (110) having a first hot medium passage and a first cold medium passage; a second heat exchanger (120) having a second hot medium passage and a second cold medium passage; a third heat exchanger (130) having a third hot medium passage and a third cold medium passage; and a fourth heat exchanger (140) having a fourth hot medium passage and a fourth cold medium passage; characterized in that, each of the hot medium passages and cold medium passages has an inlet and an outlet; the inlet of the first hot medium passage is used for importing a first-stage reacting product, the inlet of the first cold medium passage is used for importing a first-stage reacting feedstock, the outlet of the first cold medium passage is used for exporting the first-stage reacting feedstock after heat exchange; the inlet of the second hot medium passage communicates with the outlet of the first hot medium passage, the outlet of the second hot medium passage communicates with the inlet of a hot high separation tank (500), the inlet of the second cold medium passage is used for importing bottom liquid of a stripping tower; the inlet of the third hot medium passage is used for importing a second-stage reacting product, the inlet of the third cold medium passage communicates with the outlet of the second cold medium passage, the outlet of the third cold medium passage communicates with a downstream device; the inlet of the fourth hot medium passage communicates with the outlet of the third hot medium passage, the outlet of the fourth hot medium passage communicates with the inlet of the hot high separation tank (500), the inlet of the fourth cold medium passage is used for importing a second-stage reacting feedstock, the outlet of the fourth cold medium passage is used for exporting the second-stage reacting feedstock after heat exchange.

2. The heat exchange assembly according to claim 1, characterized in that, a first feeding pipeline (111) which is used for conveying the first-stage reacting feedstock is connected to the inlet of the first cold medium passage of the first heat exchanger (110), a first feeding valve (112) for controlling flow is disposed on the first feeding pipeline (111), and a first discharge pipeline (113) which is used for conveying the first-stage reacting feedstock after heat exchange is connected to the outlet of the first cold medium passage; the heat exchange assembly further comprises a first bypass pipeline (114) having a first bypass valve (115) for controlling flow, the first bypass pipeline (114) has an inlet and an outlet, the inlet of the first bypass pipeline (114) communicates with the first feeding pipeline (111), and the outlet of the first bypass pipeline (114) communicates with the first discharge pipeline (113).

3. The heat exchange assembly according to claim 2, characterized in that, the first feeding pipeline (111) comprises a raw oil pipeline (1111) having an outlet for conveying raw oil and a hydrogen pipeline (1112) having an outlet for conveying hydrogen, and both the outlet of the raw oil pipeline (1111) and the outlet of the hydrogen pipeline (1112) communicate with the inlet of the first cold medium passage of the first heat exchanger (110); the inlet of the first bypass pipeline (114) communicates with the raw oil pipeline (1111), and the first feeding valve (112) is disposed on the raw oil pipeline (1111).

4. The heat exchange assembly according to claim 2, characterized in that, the inlet of the second cold medium passage of the second heat exchanger (120) communicates with a second feeding pipeline (121) which is used for conveying the bottom liquid of the stripping tower, a second feeding valve (122) for controlling flow is disposed on the second feeding pipeline (121), and the outlet of the second cold medium passage communicates with the inlet of the third cold medium passage of the third heat exchanger (130) through a second discharge pipeline (123); the heat exchange assembly further comprises a second bypass pipeline (124) and a second bypass valve (125) disposed on the second bypass pipeline 124 for controlling flow, the second bypass pipeline (124) has an inlet and an outlet, the inlet of the second bypass pipeline (124) communicates with the second feeding pipeline (121), and the outlet of the second bypass pipeline (124) communicates with the second discharge pipeline (123).

5. The heat exchange assembly according to claim 4, characterized in that, the outlet of the third cold medium passage of the third heat exchanger (130) communicates to a third discharge pipeline (133); the heat exchange assembly further comprises a third bypass pipeline (134) and a third bypass valve (135) disposed on the third bypass pipeline (134) for controlling flow, the third bypass pipeline (134) has an inlet and an outlet, the inlet of the third bypass pipeline (134) communicates with the second discharge pipeline (123), and the outlet of the second bypass pipeline (124) communicates with the third discharge pipeline (133); and, a third feeding valve (132) for controlling flow is disposed at a position on the second discharge pipeline (123) between the inlet of the third bypass pipeline (134) and the inlet of the third cold medium passage.

6. The heat exchange assembly according to claim 2, characterized in that, the inlet of the second cold medium passage of the second heat exchanger (120) communicates to a second feeding pipeline (121) which is used for conveying the bottom liquid in the stripping tower, a second feeding valve (122) for controlling flow is disposed on the second feeding pipeline (121), and the outlet of the third cold medium passage of the third heat exchanger (130) communicates to a third discharge pipeline (133); the heat exchange assembly further comprises a large bypass pipeline (144) and a large bypass valve (145) disposed on the large bypass pipeline (144) for controlling flow, the large bypass pipeline (144) has an inlet and an outlet, the inlet of the large bypass pipeline (144) communicates with the second feeding pipeline (121), and the outlet of the large bypass pipeline (144) communicates with the third discharge pipeline (133).

7. The heat exchange assembly according to claim 5, characterized in that, at least one of the first bypass pipeline (114), the second bypass pipeline (124) and the third bypass pipeline (134) is disposed in the corresponding heat exchanger to form a bypass passage (2) having an inlet and an outlet, and the outlet of the bypass passage (2) communicates with the outlet of the cold medium passage in the corresponding heat exchanger.

8. The heat exchange assembly according to claim 7, characterized in that, each of the heat exchangers is a winding pipeline type heat exchanger and comprises a shell (1) and the cold medium passage serves as a shell pass (101) or tube pass (102); a cold medium inlet pipeline (100a) communicating with the inlet of the cold medium passage, a cold medium outlet pipeline (100b) communicating with the outlet of the cold medium passage and a bypass medium inlet pipeline (2a) communicating with the inlet of the bypass passage (2) are respectively disposed on the shell (1); the outlet of the bypass passage (2) communicates with the outlet of the cold medium passage, and, the cold medium outlet pipeline (100b) is used for exporting a mixed medium obtained after mixing a cold medium with a bypass medium.

9. The heat exchange assembly according to claim 8, characterized in that, the bypass passage (2) and the cold medium passage extend in a same direction, and the inlet of the bypass passage (2) is adjacent relative to the inlet of the cold medium passage.

10. The heat exchange assembly according to claim 9, characterized in that, the bypass passage (2) is disposed in the cold medium passage.

11. The heat exchange assembly according to claim 10, characterized in that, the bypass passage (2) extends vertically and is located at a center of the shell (1) defined as a central cylinder inside the shell (1), a heat exchange tube (3) in the tube pass (102) is spirally wound around the bypass passage (2).

12. The heat exchange assembly according to claim 11, characterized in that, a switch capable of switching off or on a path in the bypass passage (2) is disposed on the bypass passage (2) at a position adjacent to the outlet of the bypass passage (2).

13. The heat exchange assembly according to claim 12, characterized in that, the switch comprises a valve sheet (23) and an elastic element (24), the valve sheet (23) is rotatably disposed in the bypass passage (2) to switch off or on the path of the bypass passage (2); the elastic element (24) urges the valve sheet (23) to rotate so as to switch off the path of the bypass passage (2); when the bypass medium flows from the inlet to the outlet of the bypass passage (2), the valve sheet (23) is capable of overcoming an elastic force of the elastic element (24) so as to rotate to switch on the path of the bypass passage (2).

14. The heat exchange assembly according to claim 13, characterized in that, a plate (25) having a through hole (250) is transversely arranged in the bypass passage (2), the valve sheet (23) is rotatably disposed on the plate (25), and the valve sheet (23) is located downstream of the plate (25) in a flow direction of the bypass medium from the inlet to the outlet of the bypass passage (2) to open or close the through hole (250); when the valve sheet (23) opens the through hole (250), the path of the bypass passage (2) is switched on, and when the valve sheet (23) closes the through hole (250), the path of the bypass passage (2) is switched off.

15. The heat exchange assembly according to claim 14, characterized in that, an edge of the valve sheet (23) is rotatably connected to the plate (25) through a rotating shaft (231), and the elastic element (24) is a torsion spring sleeved around the rotating shaft (231).

16. The heat exchange assembly according to claim 11, characterized in that, the heat exchange tube has an top end and a bottom end, two tube plates (5) respectively for supporting the top end and the bottom end of the heat exchange tube are disposed on the shell (1), and at least one of the inlet and the outlet of the bypass passage (2) which is constrained on the tube plate (5) is movable upward and downward relative to the corresponding tube plate (5).

17. A hydrogenation system, comprising: a fractionating tower (200) having a feeding port, a stripping tower (300) having a bottom and a feeding port, a heating furnace (400) having an inlet and an outlet, a hot high separation tank (500) having an inlet, an outlet and a top, a first heat exchange device (600) having a hot medium passage and a cold medium heat exchange passage, and a heat exchange assembly of any one of claims 1-16; characterized in that, the stripping tower (300) has an outlet on the bottom of the stripping tower (300), the inlet of the second cold medium passage of the second heat exchanger (120) communicates with the outlet of the stripping tower (300); the outlet of the second hot medium passage of the second heat exchanger (120) and the outlet of the fourth hot medium passage of the fourth heat exchanger (140) respectively communicate with the inlet of the hot high separation tank (500); the outlet at the top of the hot high separation tank (500) communicates with an inlet of the hot medium passage of the first heat exchange device (600); an inlet of the cold medium heat exchange passage of the first heat exchange device (600) is connected to a stripping tower feeding pipeline (310) which is used for conveying a stripping tower feedstock, and, an outlet of the cold medium heat exchange passage of the first heat exchange device (600) communicates with the feeding port of the stripping tower (300); the outlet of a third cold medium passage of a third heat exchanger (130) communicates with the inlet of the heating furnace (400), and the outlet of the heating furnace (400) communicates with the feeding port of the fractionating tower (200).

18. The hydrogenation system according to claim 17, further comprising a second heat exchange device (700) having a cold medium heat exchange passage and a hot medium heat exchange passage; an inlet of the cold medium heat exchange passage of the second heat exchange device (700) communicates with the outlet of the third cold medium passage of the third heat exchanger (130), an outlet of the cold medium heat exchange passage of the second heat exchange device (700) communicates with the inlet of the heating furnace (400), an inlet of the hot medium heat exchange passage of the second heat exchange device (700) communicates with an outlet at the bottom of the fractionating tower (200).

19. The hydrogenation system according to claim 18, characterized in that, comprising a third heat exchange device (800), an inlet of a hot medium heat exchange passage of the third heat exchange device (800) communicates with an outlet of the hot medium heat exchange passage of the second heat exchange device (700), an inlet of a cold medium heat exchange passage of the third heat exchange device (800) communicates with a water supply pipeline (810) which is used for conveying water.

20. The hydrogenation system according to claim 17, characterized in that, the first heat exchange device (600) has three cold medium heat exchange passages, each cold medium heat exchange passage has an inlet and an outlet, the inlet of the first cold medium heat exchange passage communicates with a hydrogen supply pipeline (610) which is used for conveying hydrogen, the inlet of the second cold medium heat exchange passage communicates with the stripping tower feeding pipeline (310), the inlet of the third cold medium heat exchange passage communicates with a water delivery pipeline (620) which is used for conveying water; the first cold medium heat exchange passage, the second cold medium heat exchange passage and the third cold medium heat exchange passage are arranged alternatively in a flow direction of a hot high-fraction gas in the hot medium passage of the first heat exchange device (600).

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