Method for preventing coking of heavy distillate oil separation tower

Abstract

The invention discloses a method for preventing coking of a heavy distillate oil separation tower. The method comprises the following steps: simultaneously introducing a rectifying tower kettle liquid flowing out of the bottom of a rectifying separation tower kettle and hydrogen into a mixer for mixing; an outlet of the mixer is communicated with an inlet of a hydrogenation reactor, the hydrogenation reactor is filled with a catalyst, and a mixture discharged from the outlet of the mixer enters the hydrogenation reactor for reaction; a reaction product flowing out of an outlet of the hydrogenation reactor is divided into two paths, one path is communicated with heat exchange equipment, and the other path serves as produced liquid of a tower kettle of the rectification separation tower to be produced; a reaction product communicated with the heat exchange equipment is heated by the heat exchange equipment and then returns to the tower kettle of the rectification separation tower. The method provided by the invention effectively inhibits the occurrence of coking phenomenon, thereby improving the separation efficiency of the heavy distillate oil and the operation stability of equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil processing, and particularly relates to a method for preventing coking in a heavy fraction oil separation tower. Background Art

[0002] In the primary or secondary processing of petroleum refining, heavy fraction oil usually undergoes multi-stage separation and rectification to extract the required light oil products. However, components such as resins, asphaltenes, and polycyclic aromatic hydrocarbons in heavy fraction oil are prone to aggregation at high temperatures, forming solid precipitates and leading to coking. The coking phenomenon not only affects the operating efficiency of the separation tower but may also cause equipment failures, increasing production costs and seriously affecting the stability and continuity of the unit. Therefore, it is particularly important to develop effective anti-coking technologies.

[0003] Currently, the methods for preventing coking in heavy fraction oil separation towers mainly focus on the research of equipment, heating methods, and the addition of additives. However, these methods often have certain limitations, such as high transformation costs for equipment, strict requirements for operating conditions, and environmental and separation problems that may be brought about by chemical additives.

[0004] CN114082214B proposes an anti-coking precision distillation reboiler device, which replaces the hot material with an auxiliary cleaning liquid, optimizes the cleaning of the inner wall of the tube bundle through the equipment and improves the heat transfer efficiency, making the heat transfer process of the heat exchange tube more uniform. However, this method can only slow down coking and avoid coking caused by excessive local hot spots in the device, and it is impossible to avoid the coking tendency of the raw material itself.

[0005] CN105176567A proposes a method for preventing coking in heavy oil processing and a fractionating tower. This method sets up a high-temperature oil and gas guiding facility to divert high-temperature oil and gas to the washing and desuperheating section, shortening the residence time of high-temperature oil and gas in the fractionating tower, avoiding direct contact between high-temperature circulating oil slurry and high-temperature oil and gas, and avoiding local overheating of high-temperature circulating oil slurry, slowing down coking to a certain extent, but it also cannot avoid the coking tendency of the raw material itself.

[0006] CN116064179A proposes a method and device for recovering the heat of raw coke oven gas. By adding an additive with catalytic hydrogenation function to the washing heavy oil, heat recovery is achieved and the coking tendency is reduced. However, the addition of its additive poses a greater challenge to subsequent separation.

[0007] Therefore, there is an urgent need for a new anti-coking method to reduce the incidence of coking, improve the separation efficiency of heavy fraction oil, and ensure the economy and safety of the oil refining process. Summary of the Invention

[0008] The present invention is proposed to solve the problems existing in the prior art, such as high bottom temperature, easy coking, and large heat exchanger load in the heavy fraction oil separation tower, and its purpose is to provide a method for preventing coking in the heavy fraction oil separation tower.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for preventing coking in a heavy fraction oil separation tower specifically includes the following steps:

[0011] (ⅰ) Feed the bottoms liquid of the rectification separation tower flowing out from the bottom of the tower kettle and hydrogen into a mixer simultaneously for mixing;

[0012] (ⅱ) Connect the outlet of the mixer to the inlet of the hydrogenation reactor. The hydrogenation reactor is filled with a catalyst. Under the action of the catalyst, the mixture discharged from the outlet of the mixer removes gum and asphaltene substances and saturates some polycyclic aromatic hydrocarbons to obtain a hydrogenation product;

[0013] (ⅲ) The reaction product flowing out from the outlet of the hydrogenation reactor is divided into two paths. One path is connected to the heat exchange equipment, and the other path is taken out as the bottoms product of the rectification separation tower;

[0014] The distribution of the two paths can be based on the requirements of the bottoms extraction of a conventional rectification tower and the return to the rectification tower through the heat exchanger. The ratio gap between the two paths of different rectification towers is relatively large, and it is not easy to make a unified regulation;

[0015] (ⅳ) The reaction product of the hydrogenation reactor is returned to the bottom of the rectification separation tower after being heated by the heat exchange equipment.

[0016] In the above technical solution, the mixer is a conventional gas-liquid mixer or a microchannel gas-liquid mixer.

[0017] In the above technical solution, the volume ratio of hydrogen to the liquid phase (bottoms liquid of the rectification tower) in the mixer is 50 - 800 (standard condition); preferably, the volume ratio of hydrogen to the liquid phase is 100 - 600 (standard condition).

[0018] In the above technical solution, the hydrogenation reactor is a liquid-phase hydrogenation reactor or a gas-liquid-phase hydrogenation reactor;

[0019] In the above technical solution, the inlet temperature of the hydrogenation reactor is 60°C - 270°C, the reaction pressure is 0.1 MPa - 5.0 MPa, and the mass space velocity is 0.5 h -1 ~10.0 h -1 ; preferably, the inlet temperature of the hydrogenation reactor is 90°C - 240°C, the reaction pressure is 0.5 MPa - 3.5 MPa, and the mass space velocity is 0.8 h -1 ~3.0 h -1 .

[0020] In the above technical solution, when the hydrogenation reactor is a liquid-phase hydrogenation reactor, the reaction products of the hydrogenation reactor are divided into two paths. One path is connected to the heat exchange equipment, and the other path is taken out as the bottom product of the distillation separation column; the distribution of the two paths can be based on the requirements of the bottom product of a conventional distillation column and the return of the liquid entering the heat exchanger to the distillation column. The ratio gap between the two paths of different distillation columns is relatively large, and it is not easy to make a unified regulation.

[0021] In the above technical solution, when the hydrogenation reactor is a gas-liquid-phase hydrogenation reactor, a gas-liquid separator is arranged between the hydrogenation reactor and the heat exchange equipment. A part of the liquid separated by the gas-liquid separator is taken out as the bottom product of the distillation separation column, and the other part enters the heat exchange equipment. After being heated by the heat exchange equipment, it returns to the bottom of the distillation separation column. The gas (circulating hydrogen) separated by the gas-liquid separator returns to the mixer.

[0022] In the above technical solution, the catalyst loaded in the hydrogenation reactor includes the following components and the weight parts of each component:

[0023] Support: 30 - 90 parts;

[0024] Group VIII or Group VIB metal: 0.01 part - 16 parts;

[0025] Binder: 9.99 - 69.99 parts.

[0026] In the above technical solution, the support is any one or several of silica, alumina, amorphous silica-alumina or molecular sieve.

[0027] In the above technical solution, the Group VIII metal is any one or several of platinum, palladium, cobalt, iridium or nickel.

[0028] In the above technical solution, the Group VIB metal is any one or two of molybdenum or tungsten.

[0029] In the above technical solution, the binder is any one or several of pseudoboehmite, silica sol or acid-treated clay.

[0030] In the above technical solution, the heat exchange equipment is a heating furnace or a heat exchanger.

[0031] The beneficial effects of the present invention are:

[0032] The invention provides a method for preventing coking of a heavy distillate oil separation tower. The method has strong adaptability and can handle the separation of heavy distillate oil in the primary or secondary processing of petroleum refining; the reaction heat in the hydrogenation process of the heavy distillate oil is effectively utilized, the heat load of the heat exchanger is reduced, and the energy consumption is low; the colloid, asphaltenes and polycyclic aromatic hydrocarbons in the heavy distillate oil are partially removed, the risk of coking of the heavy distillate oil is fundamentally reduced, and the quality of the heavy distillate oil product is improved; the temperature of the tower bottom heat exchanger / reboiler is low; the process flow is simple, the investment in new equipment is low, and the transformation of old equipment is simple; compared with a conventional heavy distillate oil separation tower, the application reduces the temperature of the tower bottom heat exchanger by 5°C to 50°C and the heat exchanger load by 5% to 60%. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of embodiments 1 and 2 of the present invention;

[0034] Figure 2 It is a schematic diagram of the structure of Embodiments 3 and 4 of the present invention;

[0035] Figure 3 It is a schematic diagram of the structure of Comparative Examples 1 and 2 of the present invention;

[0036] in:

[0037] 1. Distillation separation tower kettle; 2. Mixer; 3. Hydrogenation reactor; 4. Heat exchange equipment; 5. Gas-liquid separator.

[0038] A. Mixed raw materials; B. Distillation tower bottom liquid; C. Hydrogen; D. Reactor outlet logistics; E. Distillation tower bottom produced liquid; F. Distillation tower bottom reflux liquid; G. Circulating hydrogen.

[0039] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0041] Example 1

[0042] A method for preventing coking of a heavy distillate oil separation tower, using Figure 1 The device shown specifically comprises the following steps:

[0043] (i) a mixed feedstock A containing heavy distillate oil enters a distillation separation tower kettle 1, and a distillation tower kettle liquid B and hydrogen C flowing out of the bottom of the distillation separation tower kettle 1 are simultaneously introduced into a mixer 2 for thorough mixing;

[0044] (ii) The outlet of the mixer 2 is connected to the inlet of the hydrogenation reactor 3. The hydrogenation reactor 3 is filled with a catalyst. The mixed mixture discharged from the outlet of the mixer 2 is in the hydrogenation reactor 3 and under the action of the catalyst, gums and asphaltene substances are removed, and some polycyclic aromatic hydrocarbons are saturated to obtain a hydrogenation product;

[0045] (iii) The reaction product D flowing out of the outlet of the hydrogenation reactor 3 is divided into two paths. One path is used as the reflux liquid F at the bottom of the distillation column and is connected to the heat exchange device 4, and the other path is taken out as the bottom product E of the distillation column at the bottom of the distillation separation column 1;

[0046] (iv) The reflux liquid F at the bottom of the distillation column returns to the bottom of the distillation separation column 1 after being heated by the heat exchange device 4.

[0047] In this embodiment, the mixed raw material A containing heavy distillate oil is a mixed aromatic hydrocarbon component, and its raw material properties are shown in Table 1. The mixed raw material A containing heavy distillate oil needs to be separated by distillation to separate toluene, xylene, trimethylbenzene, naphthalene and methylnaphthalene, and the raw material amount is 10 t / h.

[0048] Table 1: Raw material properties of mixed aromatic hydrocarbon components

[0049] Component Content, wt% Toluene 15 Xylene 30 Trimethylbenzene 15 Naphthalene 20 Methylnaphthalene 20

[0050] In this embodiment, the number of theoretical plates of the bottom of the distillation separation column 1 is 40, and the top pressure is 0.1 MPa.

[0051] In this embodiment, the hydrogenation reactor 3 is a liquid-phase hydrogenation reactor, and the mixer 2 is a microchannel gas-liquid intensifying mixer; the heat exchange device 4 is a heating furnace.

[0052] In this embodiment, the catalyst filled in the hydrogenation reactor 3 includes the following components and the weight parts of each component are: amorphous silica-alumina carrier 70 parts; pseudo-boehmite binder 28 parts; platinum 0.2 parts; palladium 0.2 parts; molybdenum 1.2 parts; iridium 0.4 parts.

[0053] In this embodiment, the volume ratio of hydrogen to the liquid phase in the mixer is 100 (standard condition).

[0054] In this embodiment, the inlet temperature of the hydrogenation reactor 3 is 100 °C, the reaction pressure is 3 MPa, and the mass space velocity is 3.0 h -1 。

[0055] In this embodiment, the load of the heating furnace as the heat exchange device 4 and the temperature of the bottom heat exchanger are shown in Table 2.

[0056] Example 2

[0057] A method for preventing coking in a heavy distillate oil separation column, using the device as shown in Figure 1 and specifically includes the following steps:

[0058] (ⅰ) The mixed raw material A containing heavy distillate oil enters the bottom of the rectifying separation column 1. The rectifying column bottom liquid B flowing out from the bottom of the rectifying separation column 1 and hydrogen C are simultaneously introduced into the mixer 2 for sufficient mixing;

[0059] (ⅱ) The outlet of the mixer 2 is connected to the inlet of the hydrogenation reactor 3. The catalyst is loaded in the hydrogenation reactor 3. The mixed mixture discharged from the outlet of the mixer 2 removes gum and asphaltene substances under the action of the catalyst in the hydrogenation reactor 3, and part of the polycyclic aromatic hydrocarbons is saturated to obtain the hydrogenation product;

[0060] (ⅲ) The reaction product D flowing out from the outlet of the hydrogenation reactor 3 is divided into two paths. One path is used as the rectifying column bottom reflux liquid F and is connected to the heat exchange equipment 4, and the other path is taken out as the rectifying column bottom extract E of the rectifying separation column 1;

[0061] (ⅳ) The rectifying column bottom reflux liquid F returns to the bottom of the rectifying separation column 1 after being heated by the heat exchange equipment 4.

[0062] In this embodiment, the mixed raw material A containing heavy distillate oil is reformed heavy aromatics. The mixed raw material A containing heavy distillate oil needs to be rectified and separated to separate tetramethylbenzene and lighter components, and the raw material amount is 30 t / h.

[0063] In this embodiment, the number of theoretical plates of the rectifying separation column 1 is 70, and the top pressure is 0.1 MPa.

[0064] In this embodiment, the hydrogenation reactor 3 is a liquid-phase hydrogenation reactor, and the mixer 2 is a microchannel gas-liquid intensifying mixer; the heat exchange equipment 4 is a heating furnace.

[0065] In this embodiment, the catalyst loaded in the hydrogenation reactor 3 includes the following components and the weight parts of each component are: 50 parts of amorphous silica-alumina carrier; 20 parts of Y molecular sieve carrier; 20 parts of pseudo-boehmite binder; 7 parts of nickel; 2 parts of molybdenum; 1 part of cobalt.

[0066] In this embodiment, the volume ratio of hydrogen to liquid phase in the mixer is 50 (standard condition).

[0067] In this embodiment, the inlet temperature of the hydrogenation reactor 3 is 50 °C, the reaction pressure is 0.5 MPa, and the mass space velocity is 0.8 h -1 .

[0068] In this embodiment, the load of the heating furnace as the heat exchange equipment 4 and the temperature of the bottom heat exchanger are shown in Table 3.

[0069] Example 3

[0070] A method for preventing coking in a heavy distillate oil separation column, using as Figure 2The device shown specifically includes the following steps:

[0071] (i) The mixed raw material A containing heavy distillate oil enters the bottom of the rectification separation tower 1. The rectification tower bottom liquid B flowing out from the bottom of the rectification separation tower 1 and hydrogen C are simultaneously introduced into the mixer 2 for full mixing.

[0072] (ii) The outlet of the mixer 2 is connected to the inlet of the hydrogenation reactor 3. The hydrogenation reactor 3 is filled with a catalyst. The mixed mixture discharged from the outlet of the mixer 2 removes gum and asphaltene substances and saturates some polycyclic aromatic hydrocarbons under the action of the catalyst in the hydrogenation reactor 3 (gas-phase hydrogenation reactor) to obtain a hydrogenation product.

[0073] (iii) The reaction product D flowing out from the outlet of the hydrogenation reactor 3 enters the gas-liquid separation device 5. The gas-liquid separation device 5 separates to obtain recycled hydrogen G which returns to the mixer 2. The liquid-phase product is divided into two paths. One path is taken out as the rectification tower bottom product E, and the other path is taken as the rectification tower bottom reflux liquid F. After being heated by the heat exchange device 4, it returns to the bottom of the rectification separation tower 1.

[0074] In this embodiment, the mixed raw material A containing heavy distillate oil is a mixed aromatic hydrocarbon component. Its raw material properties are shown in Table 1. The mixed raw material A containing heavy distillate oil needs to be separated by rectification to separate toluene, xylene, trimethylbenzene, naphthalene, and methylnaphthalene. The raw material amount is 10 t / h.

[0075] In this embodiment, the number of theoretical plates of the rectification separation tower 1 is 40, and the top pressure is 0.1 MPa.

[0076] In this embodiment, the hydrogenation reactor 3 is a gas-liquid hydrogenation reactor, and the mixer 2 is a conventional gas-liquid mixer; the heat exchange device 4 is a heating furnace.

[0077] In this embodiment, the catalyst filled in the hydrogenation reactor 3 includes the following components and the weight parts of each component: amorphous silica-alumina carrier 50 parts; alumina carrier 20 parts; silica sol binder 25 parts; platinum 0.2 parts; palladium 0.2 parts; nickel 3 parts; tungsten 1.6 parts.

[0078] In this embodiment, the volume ratio of hydrogen to the liquid phase in the mixer is 600 (standard condition).

[0079] In this embodiment, the inlet temperature of the hydrogenation reactor 3 is 270 °C, the reaction pressure is 1.0 MPa, and the mass space velocity is 3.0 h -1 .

[0080] In this embodiment, the load of the heating furnace as the heat exchange device 4 and the temperature of the bottom tower heat exchanger are shown in Table 2.

[0081] Example 4

[0082] A method for preventing coking in a heavy fraction oil separation column uses the device as shown in Figure 2 and specifically includes the following steps:

[0083] (ⅰ) The mixed raw material A containing heavy fraction oil enters the bottom of the rectifying separation column 1. The rectifying column bottom liquid B flowing out from the bottom of the rectifying separation column 1 and hydrogen C are simultaneously introduced into the mixer 2 for thorough mixing;

[0084] (ⅱ) The outlet of the mixer 2 is connected to the inlet of the hydrogenation reactor 3. The hydrogenation reactor 3 is filled with a catalyst. The mixed mixture discharged from the outlet of the mixer 2 removes gum and asphaltene substances under the action of the catalyst in the hydrogenation reactor 3, and saturates some polycyclic aromatic hydrocarbons to obtain a hydrogenation product;

[0085] (ⅲ) The reaction product D flowing out from the outlet of the hydrogenation reactor 3 is divided into two paths. One path is used as the rectifying column bottom reflux liquid F and is connected to the heat exchange device 4, and the other path is taken out as the rectifying column bottom product E of the rectifying separation column 1;

[0086] (ⅳ) The rectifying column bottom reflux liquid F returns to the rectifying separation column bottom 1 after being heated by the heat exchange device 4.

[0087] In this embodiment, the mixed raw material A containing heavy fraction oil is reformed heavy aromatics. The mixed raw material A containing heavy fraction oil needs to be separated by rectification to separate tetramethylbenzene and lighter components, and the raw material amount is 30 t / h.

[0088] In this embodiment, the number of theoretical plates of the rectifying separation column bottom 1 is 70, and the top pressure is 0.1 MPa.

[0089] In this embodiment, the hydrogenation reactor 3 is a gas-liquid hydrogenation reactor, and the mixer 2 is a conventional gas-liquid mixer; the heat exchange device 4 is a heat exchanger.

[0090] In this embodiment, the catalyst filled in the hydrogenation reactor 3 includes the following components and the weight parts of each component are: amorphous silica-alumina carrier 40 parts; Y zeolite carrier 20 parts; ZSM-5 zeolite carrier 10 parts; pseudoboehmite binder 20 parts; nickel 8 parts; molybdenum 2 parts.

[0091] In this embodiment, the volume ratio of hydrogen to liquid phase in the mixer is 800 (standard condition).

[0092] In this embodiment, the inlet temperature of the hydrogenation reactor 3 is 100 °C, the reaction pressure is 3 MPa, and the mass space velocity is 1.2 h -1 .

[0093] In this embodiment, the load of the heating furnace as the heat exchange device 4 and the temperature of the bottom column heat exchanger are shown in Table 3.

[0094] Comparative Example 1

[0095] A separation method for a heavy fraction oil separation column, using the device as shown in Figure 3 as follows:

[0096] The mixed raw material A containing heavy fraction oil enters the bottom of the rectifying separation column 1. The rectifying column bottom liquid B flowing out from the bottom of the rectifying separation column 1 is divided into two paths. One path is taken out as the rectifying column bottom product E, and the other path is taken as the rectifying column bottom reflux liquid F, which is heated by the heat exchange device 4 and then returned to the rectifying separation column 1.

[0097] In this comparative example, the mixed raw material A containing heavy fraction oil is a mixed aromatic hydrocarbon component, and its raw material properties are shown in Table 1. The mixed raw material A containing heavy fraction oil needs to be separated by rectification to separate toluene, xylene, trimethylbenzene, naphthalene, and methylnaphthalene, and the raw material quantity is 10 t / h.

[0098] In this comparative example, the number of theoretical plates of the rectifying separation column 1 is 70, and the top pressure is 0.1 MPa.

[0099] In this comparative example, the heat exchange device 4 is a heating furnace.

[0100] In this comparative example, the load of the heating furnace as the heat exchange device 4 and the temperature of the bottom heat exchanger are shown in Table 2.

[0101] Comparative Example 2

[0102] A separation method for a heavy fraction oil separation column, using the device as shown in Figure 3 as follows:

[0103] The mixed raw material A containing heavy fraction oil enters the bottom of the rectifying separation column 1. The rectifying column bottom liquid B flowing out from the bottom of the rectifying separation column 1 is divided into two paths. One path is taken out as the rectifying column bottom product E, and the other path is taken as the rectifying column bottom reflux liquid F, which is heated by the heat exchange device 4 and then returned to the rectifying separation column 1.

[0104] In this comparative example, the mixed raw material A containing heavy fraction oil is reformed heavy aromatics. The mixed raw material A containing heavy fraction oil needs to be separated by rectification to separate tetramethylbenzene and lighter components, and the raw material quantity is 30 t / h.

[0105] In this comparative example, the number of theoretical plates of the rectifying separation column 1 is 70, and the top pressure is 0.1 MPa.

[0106] In this comparative example, the heat exchange device 4 is a heating furnace.

[0107] In this comparative example, the load of the heating furnace as the heat exchange device 4 and the temperature of the bottom heat exchanger are shown in Table 3.

[0108] Table 2 Data Sheet of Example 1, Example 3, and Comparative Example 1

[0109] Example 1 Example 3 Comparative Example 1 Bottom heating load, KW 918 673 1426 Bottom reboiler temperature, °C 228 216 233

[0110] Table 3 Data Sheet of Example 2, Example 4, and Comparative Example 2

[0111] Example 2 Example 4 Comparative Example 2 Bottom heating load, KW 1436 905 1795 Bottom reboiler temperature, °C 319 308 338

[0112] As can be seen from Tables 2 and 3, compared with Comparative Examples 1 and 2 using the traditional method, Examples 1 to 4 using the method of the present application reduce the temperature of the bottom tower heat exchanger by 5°C to 50°C and the heat exchanger load by 5% to 60%.

[0113] The distillation separation tower generally consists of a tower body, a reboiler (heat exchange equipment), a condenser cooler, a reflux drum, and a reflux pump. The heat exchange equipment is the key area where coking occurs. The method for preventing coking of the heavy fraction oil separation tower provided by the present invention is used to prevent coking of the heat exchange equipment of the separation tower.

[0114] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preventing coking in a heavy fraction oil separation tower, characterized in that: The following steps are involved: (i) introducing the distillation tower bottom liquid and hydrogen flowing out from the bottom of the distillation separation tower bottom (1) into a mixer (2) for mixing; (ii) the outlet of the mixer (2) is connected to the inlet of the hydrogenation reactor (3), the hydrogenation reactor (3) is filled with a catalyst, and the mixture discharged from the outlet of the mixer (2) enters the hydrogenation reactor (3) for reaction; (iii) the reaction product flowing out of the outlet of the hydrogenation reactor (3) is divided into two paths, one of which is connected to the heat exchange device (4) and the other is taken out as the produced liquid of the bottom of the distillation separation tower (1); (iv) The reaction product of the hydrogenation reactor (3) is heated by the heat exchange device (4) and then returned to the bottom of the distillation separation tower (1).

2. The method for preventing coking in a heavy fraction oil separation tower according to claim 1, characterized in that: The mixer (2) is a conventional gas-liquid mixer or a microchannel gas-liquid mixer; the volume ratio of hydrogen to distillation tower bottom liquid in the mixer (2) is (50-800):

1.

3. The method for preventing coking in a heavy fraction oil separation tower according to claim 1, characterized in that: The hydrogenation reactor (3) is a liquid phase hydrogenation reactor or a gas-liquid phase hydrogenation reactor; the inlet temperature of the hydrogenation reactor (3) is 60°C to 270°C, the reaction pressure is 0.1MPa to 5.0MPa, and the mass space velocity is 0.5h -1 ~10.0h -1 The preferred inlet temperature of the hydrogenation reactor (3) is 90°C to 240°C, the reaction pressure is 0.5MPa to 3.5MPa, and the mass space velocity is 0.8h -1 ~3.0h -1 .

4. The method for preventing coking in a heavy fraction oil separation tower according to claim 3, characterized in that: When the hydrogenation reactor (3) is a gas-liquid phase hydrogenation reactor, a gas-liquid separator (5) is arranged between the hydrogenation reactor (3) and the heat exchange device (4); a portion of the liquid separated by the gas-liquid separator (5) is produced as the produced liquid of the distillation separation tower kettle (1), and the other portion enters the heat exchange device (4), is heated by the heat exchange device (4), and then returns to the distillation separation tower kettle (1); the gas separated by the gas-liquid separator (5) returns to the mixer (2).

5. The method for preventing coking in a heavy fraction oil separation tower according to claim 1, characterized in that: The catalyst loaded in the hydrogenation reactor (3) includes the following components and the weight proportions of the components: 30-90 parts of carrier; 0.01 to 16 parts of Group VIII or Group VIB metals; 9.99 to 69.99 parts of binder.

6. The method for preventing coking in a heavy fraction oil separation tower according to claim 5, characterized in that: The carrier is any one or more of silicon oxide, aluminum oxide, amorphous silicon aluminum or molecular sieve.

7. The method for preventing coking in a heavy fraction oil separation tower according to claim 5, characterized in that: The Group VIII metal is any one or more of platinum, palladium, cobalt, iridium or nickel.

8. The method for preventing coking in a heavy fraction oil separation tower according to claim 5, characterized in that: The VIB group metal is any one or both of molybdenum and tungsten.

9. The method for preventing coking in a heavy fraction oil separation tower according to claim 5, characterized in that: The binder is any one or more of pseudo-boehmite, silica sol or clay treated with acid.

10. The method for preventing coking in a heavy fraction oil separation tower according to claim 1, characterized in that: The heat exchange equipment (4) is a heating furnace or a heat exchanger.

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