Naphtha hydrogenation system and method for cooling dechlorinator

Abstract

The present application provides a naphtha hydrogenation system and a method for cooling a dechlorination device. The naphtha hydrogenation system comprises a heating reaction device, a dechlorination device, and a gas-liquid separation device. The heating reaction device heats and reacts the feed to remove impurities in the raw material. The inlet end of the dechlorination device is connected to the outlet end of the heating reaction device. The outlet pipeline of the dechlorination device passes through the heating reaction device and is connected to the gas-liquid separation device. The gas-liquid separation device comprises a liquid phase outlet and a gas phase outlet. The gas phase outlet is connected to the heating reaction device and the inlet end of the dechlorination device, respectively, to recycle and deliver the hydrogen gas in the gas phase outlet to the dechlorination device, and to recover the oil gas and heat of the gas-liquid separation device through the heating reaction device. The present application can accelerate the replacement cooling speed of naphtha hydrogenation dechlorination, reduce the discharge of three wastes, and save the amount of nitrogen gas.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and in particular to a naphtha hydrogenation system and a method for cooling a dechlorinator. Background Technology

[0002] Naphtha is a petroleum product, also known as chemical light oil or crude gasoline. It is a light oil produced from crude oil or other raw materials and is used as a chemical raw material.

[0003] When the dechlorinating agent in a naphtha hydrotreating unit reaches the end of its service life, the dechlorinator needs to be disconnected from the system first, and then the liquid needs to be drained and cooled. The dechlorinator can only be opened for inspection and agent unloading when the temperature drops to 40°C. Because the dechlorinator is large and has thick walls with good external insulation, the traditional method of cooling with nitrogen replacement is slow and produces a lot of sludge and flare gas. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a naphtha hydrogenation system and a method for cooling the dechlorinator, in order to solve the problems in the prior art where the dechlorinator is large, has thick walls, and has good external insulation, the traditional method of nitrogen replacement cooling is slow and produces a lot of sludge and flare gas.

[0005] To achieve the above and other related objectives, the present invention provides a naphtha hydrotreating system, comprising: a heating reaction device for heating and reacting the feed to remove impurities; a dechlorination device, the inlet of which is connected to the outlet of the heating reaction device; and a gas-liquid separation device, the outlet pipeline of which passes through the heating reaction device and is connected to the gas-liquid separation device; the gas-liquid separation device includes a liquid phase outlet and a gas phase outlet, the gas phase outlet being connected to the inlet of the heating reaction device and the dechlorination device respectively, so as to circulate the hydrogen from the gas phase outlet to the dechlorination device, and recover the oil and gas and heat from the gas-liquid separation device through the heating reaction device.

[0006] In one embodiment of the present invention, the heating reaction apparatus includes: a heating device for preheating, heat exchange, and heating the raw materials for the reaction feed; and a reactor, the inlet end of which is connected to the outlet end of the heating device to remove impurities from the heated raw materials.

[0007] In one embodiment of the present invention, the heating device includes: a preheater having a feed inlet for preheating raw materials added through the feed inlet; a heat exchanger having its inlet end connected to the outlet end of the preheater for heat exchange heating of the preheated raw materials; and a heating furnace having its inlet end connected to the outlet end of the heat exchanger and its outlet end connected to a dechlorination device for heating the heat-exchanged raw materials to a preset temperature.

[0008] In one embodiment of the present invention, the dechlorination device includes: a dechlorinator, the inlet end of which is connected to the outlet end of the reactor, the outlet end of which is connected to a gas-liquid separation device via an outlet pipeline, and the outlet end of which is also provided with a sludge outlet and a flare outlet; and a purge port, which is connected to the inlet end of the dechlorinator and includes a nitrogen inlet and a steam inlet, so that when the inlet connecting the dechlorinator and the reactor is closed, nitrogen is blown in through the top of the dechlorinator for purging and replacement.

[0009] In one embodiment of the present invention, the outlet pipeline passes through a heat exchanger and a preheater in sequence and is connected to a gas-liquid separation device.

[0010] In one embodiment of the present invention, the outlet end of the dechlorinator is further provided with a crossover line, the outlet end of which is connected to the outlet pipeline after heat exchange by the heat exchanger and the preheater.

[0011] In one embodiment of the present invention, the gas-liquid separation device includes: an air cooler, the outlet end of an outlet pipeline being connected to the inlet end of the air cooler; a gas-liquid separator, the inlet end of which is connected to the outlet end of the air cooler, with a liquid phase outlet and a gas phase outlet respectively disposed on the gas-liquid separator; and a compressor, the inlet end of which is connected to the gas phase outlet, and the outlet end of which is connected to the inlet ends of a heat exchanger and a dechlorination device respectively.

[0012] In one embodiment of the present invention, the compressor is a circulating hydrogen compressor, which includes a first pipeline and a second pipeline. The inlet end of the first pipeline is connected to the outlet end of the compressor, the inlet ends of two second pipelines are connected to the first pipeline, the outlet end of one second pipeline is connected to a heat exchanger, and the outlet end of the other second pipeline is connected to the inlet end of a dechlorination device.

[0013] In one embodiment of the present invention, the heat exchanger is a shell-and-tube heat exchanger.

[0014] The present invention also provides a method for cooling a dechlorinator using the aforementioned naphtha hydrotreating system, comprising the following steps:

[0015] In response to a control signal that requires the dechlorination unit to be cut off, the inlet valve of the dechlorination unit is closed and the corresponding valve on the second pipeline is opened, so that the compressor circulates hydrogen to the dechlorination unit. The hot oil in the dechlorination unit is replaced by heat exchangers and preheaters to recover oil and heat.

[0016] In response to the first temperature control signal of the dechlorination unit, the outlet valve of the dechlorination unit is closed, and the air cooler is opened to circulate and cool the dechlorination unit through the condensed hydrogen.

[0017] In response to the second temperature control signal of the dechlorination unit, the inlet valve of the dechlorination unit and the cross line connected to the air cooler are closed, and nitrogen gas is blown in from the top of the dechlorination unit for purging and replacement.

[0018] The beneficial effects of this invention are as follows: This invention proposes a naphtha hydrotreating system and a method for cooling a dechlorinator. Through the coordinated operation of a gas-liquid separation device, a dechlorination device, and a heating reaction device, the system and method allow hydrogen separated by the gas-liquid separation device to be pressurized and circulated into the dechlorination device. This hydrogen circulation displaces the hot oil in the dechlorinator into the heat exchanger and preheater, enabling oil and gas recovery and heat recovery. Furthermore, when the temperature inside the dechlorinator drops to the temperature corresponding to the first temperature control signal, the dechlorinator outlet valve is closed, and the cross-line valve to the air cooler is opened, continuing the hydrogen circulation cooling process while simultaneously recovering some of the oil and gas inside the dechlorinator. Finally, when the temperature inside the dechlorinator drops to the temperature corresponding to the second temperature control signal, the dechlorinator inlet hydrogen cross-line valve and the cross-line valve to the air cooler are closed, and nitrogen from the tank top is used for purging and replacement. This accelerates the naphtha hydrotreating and dechlorination cooling process, reduces the dechlorinator cooling time, saves nitrogen consumption, and simultaneously reduces the emission of waste oil and exhaust gas. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the displacement cooling system of the present invention.

[0020] Figure 2 This is a flowchart of the cooling method of the present invention.

[0021] Component designation explanation

[0022] Heating reaction device 1; dechlorination device 2; gas-liquid separation device 3; heating device 11; reactor 12; liquid phase outlet 31; gas phase outlet 32; preheater 111; heat exchanger 112; heating furnace 113; dechlorinator 21; purge port 22; outlet pipeline 23; nitrogen inlet 221; steam inlet 222; sludge outlet 211; flare outlet 212; cross-line 213; air cooler 33; gas-liquid separator 34; compressor 35; first pipeline 331; second pipeline 332. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0024] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0025] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0026] Please see Figure 1 This invention provides a naphtha hydrotreating system, comprising: a heating reaction device 1, which heats and reacts the feed to remove impurities; a dechlorination device 2, the inlet of which is connected to the outlet of the heating reaction device 1; and a gas-liquid separation device 3, the outlet pipeline 23 of which passes through the heating reaction device 1 and is connected to the gas-liquid separation device 3; the gas-liquid separation device 3 includes a liquid phase outlet 31 and a gas phase outlet 32, the gas phase outlet 32 ​​being connected to the inlet of the heating reaction device 1 and the dechlorination device 2 respectively, so as to circulate the hydrogen from the gas phase outlet 32 ​​to the dechlorination device 2, and recover the oil and gas and heat from the gas-liquid separation device 3 through the heating reaction device 1.

[0027] As can be seen from the above, in the naphtha hydrotreating process, the feedstock is first preheated, heat-exchanged, and heated in the hydrotreating reactor 1 to a temperature of, for example, 280°C. Then, impurities are removed from the feedstock, such as organic sulfur, nitrogen compounds, silicone oil, and metallic impurities. After this treatment, the feedstock undergoes hydrodechlorination in the dechlorination unit 2, and after pre-hydrogenation and mixing, it is fed back into the heating reactor 1 for heat exchange. The product is then condensed and cooled in the gas-liquid separator 3, resulting in liquid-phase reaction products and hydrogen, which are discharged through liquid-phase outlet 31 and gas-phase outlet 32, respectively. Liquid-phase outlet 31 can discharge the liquid-phase reaction products into a fractionation system for further processing, while gas-phase outlet 32 ​​further circulates the discharged hydrogen to the inlet of the heating reactor 1 and the dechlorination unit 2. This increases the nitrogen supply during naphtha hydrodechlorination, thereby accelerating the displacement cooling rate, reducing waste emissions, and saving nitrogen consumption. That is, for example, when the dechlorinating agent reaches the end of its lifespan and it is necessary to disconnect the dechlorination unit 2 from the system for drainage and cooling, the outlet valve of the gas-liquid separator 3 is opened, and hydrogen supplied by the gas-liquid separator 3 is used for circulating cooling, while simultaneously recovering some of the oil and gas in the dechlorination unit 2. Furthermore, before the circulating hydrogen is supplied for cooling, the hot oil in the dechlorination unit 2 can be replaced in the heating reaction device 1 by passing the circulating hydrogen through the heating reaction device 1, further recovering heat. And, when the temperature inside the dechlorination unit 2 drops to a temperature suitable for purging and replacement, the flow of circulating hydrogen from the gas-liquid separator 3 to the dechlorination unit 2 is shut off, and nitrogen is used to purge and replace the oil at the top of the tank of the dechlorination unit 2. Through these methods, the cooling time of the dechlorination unit 2 can be significantly shortened, nitrogen consumption can be saved, and the emission of sludge and waste gas can be reduced.

[0028] like Figure 1 As shown, the heating reaction apparatus 1 includes: a heating device 11, which preheats, exchanges heat and heats the raw materials for the reaction feed; and a reactor 12, the inlet end of which is connected to the outlet end of the heating device 11 to remove impurities from the heated raw materials.

[0029] In one embodiment of the present invention, in the heating reaction apparatus 1, the raw materials for the reaction feed are preheated, heat exchanged, and heated using the heating device 11. This heats the raw materials to a temperature of, for example, 280°C, before transferring them to the reactor 12 to remove organic sulfur, nitrogen compounds, silicone oil, and metallic impurities from the raw materials.

[0030] Furthermore, the heating device 11 includes: a preheater 111, which has a feed inlet for preheating the raw material added through the feed inlet; a heat exchanger 112, the inlet end of which is connected to the outlet end of the preheater 111 for heat exchange heating of the preheated raw material; and a heating furnace 113, the inlet end of which is connected to the outlet end of the heat exchanger 112, and the outlet end of the heating furnace 113 is connected to the dechlorination device 2 for heating the heat-exchanged raw material to a preset temperature.

[0031] In one embodiment of the present invention, when the heating device 11 heats the raw material of the reaction feed, it uses a preheater 111 to preheat the naphtha before it enters the main heating equipment, thereby increasing the temperature of the naphtha and preparing it for subsequent heat exchange and heating processes. Specifically, the preheater can use a low-grade heat source (such as waste heat from cooling water) or exchange heat with other process streams to preheat the naphtha. After preheating, the naphtha feedstock enters the heat exchanger 112 to further heat the naphtha feedstock using the heat energy of the reaction products or other high-temperature streams. This method can improve energy utilization efficiency and reduce energy consumption. Furthermore, after preheating and heat exchange, the temperature of the naphtha has been significantly increased, but may not yet reach the temperature required for the reaction. Therefore, the final heating is performed by the heating furnace 113. Specifically, the heating furnace 113 can use fuel (such as natural gas, fuel oil, etc.) for combustion, and the resulting high-temperature flame heats the naphtha to the temperature required for the reaction (e.g., 280°C) through the furnace tubes.

[0032] Specifically, the dechlorination device 2 includes: a dechlorinator 21, the inlet end of which is connected to the outlet end of the reactor 12, the outlet end of which is connected to the gas-liquid separation device 3 via an outlet pipeline 23, and the outlet end of the dechlorinator 21 is also provided with a sludge outlet 211 and a flare outlet 212; and a purge port 22, which is connected to the inlet end of the dechlorinator 21, and includes a nitrogen inlet 221 and a steam inlet 222, so that when the inlet connecting the dechlorinator 21 to the reactor 12 is closed, nitrogen is blown in through the top of the dechlorinator 21 for purging and replacement.

[0033] In one embodiment of the present invention, during dechlorination, the dechlorination device 2 utilizes the dechlorinator 21 to hydrogenate the naphtha feedstock with hydrogen gas at the top of the dechlorinator 21 under the action of a catalyst, removing impurities and unsaturated hydrocarbons. The oil and gas are then discharged to the light sludge oil outlet 211 and to the flare system through the flare outlet 212. To accelerate the replacement and cooling rate of the dechlorinator 21, circulating hydrogen gas is introduced into the dechlorinator 21 via a gas-liquid separator 3 to rapidly cool it. Furthermore, when the temperature drops to a certain level, such as 80°C, the circulating hydrogen gas in the dechlorinator 21 is shut off, and nitrogen gas from the top of the dechlorinator 21 is used for purging and replacement, effectively saving nitrogen consumption and reducing the emission of sludge oil and waste gas.

[0034] Preferably, the outlet pipeline 23 passes through the heat exchanger 112 and the preheater 111 in sequence and is connected to the gas-liquid separation device 3.

[0035] In one embodiment of the present invention, when the circulating hydrogen gas of the gas-liquid separation device 3 is introduced into the dechlorinator 21, the circulating hydrogen gas is used to replace the hot oil in the dechlorinator 21 through the outlet pipeline 23 into the heat exchanger 112 and the preheater 111, so as to recover oil gas and heat.

[0036] Furthermore, the outlet end of the dechlorinator 21 is also provided with a crossover line 213, the outlet end of which is connected to the outlet pipeline 23 after heat exchange with the heat exchanger 112 and the preheater 111. In this embodiment, the crossover line 213 is also provided with a corresponding control valve. This allows the outlet valve of the dechlorinator 21 to be closed and the gas-liquid separation device 3 to be opened when the temperature of the dechlorinator 21 drops to a preset temperature, thereby achieving continuous cooling by utilizing circulating hydrogen and recovering some of the oil and gas in the dechlorinator 21.

[0037] Furthermore, the gas-liquid separation device 3 includes: an air cooler 33, the outlet end of the outlet pipeline 23 being connected to the inlet end of the air cooler 33; a gas-liquid separator 34, the inlet end of the gas-liquid separator 34 being connected to the outlet end of the air cooler 33, with a liquid phase outlet 31 and a gas phase outlet 32 ​​respectively located on the gas-liquid separator 34; and a compressor 35, the inlet end of the compressor 35 being connected to the gas phase outlet 32, and the outlet end of the compressor 35 being connected to the inlet ends of the heat exchanger 112 and the dechlorination device 2 respectively.

[0038] In one embodiment of the present invention, during operation, the gas-liquid separation device 3 condenses and cools the product through an air cooler 33 before it enters the gas-liquid separator 32. The reaction products undergo gas-liquid separation in the gas-liquid separator 34. Hydrogen is drawn from the top gas phase outlet 32, pressurized by a circulating hydrogen compressor, and then circulated back into the reaction system. The liquid phase reaction product is sent to downstream fractionation from the bottom liquid phase outlet 31. Specifically, the air cooler 33 uses ambient air as the cooling medium, passing across the outside of the finned tubes to cool or condense the high-temperature process fluid inside. The gas-liquid separator 34 is a device that uses the differences in physical properties (such as density and flow characteristics) between gas and liquid to separate them. Specifically, gas-liquid separation can be achieved through gravity settling, baffle separation, centrifugal separation, and packed fractionation.

[0039] Specifically, compressor 35 is a circulating hydrogen compressor. Compressor 35 includes a first pipeline 331 and a second pipeline 332. The inlet end of the first pipeline 331 is connected to the outlet end of compressor 35, and the inlets of the two second pipelines 332 are connected to the first pipeline 331. The outlet end of one second pipeline 332 is connected to heat exchanger 112, and the outlet end of the other second pipeline 332 is connected to the inlet end of dechlorination unit 2. In this embodiment, the circulating hydrogen compressor is used to increase the circulating hydrogen pressure to overcome the system pressure drop and ensure the circulating gas volume required by the process. The hydrogen compressed by compressor 35 is transported through the first pipeline 331 to several second pipelines 332, and then further transported through the second pipelines 332 to the inlet ends of heat exchanger 112 and dechlorination unit 2.

[0040] Preferably, heat exchanger 112 is a shell-and-tube heat exchanger. In this embodiment, the shell-and-tube heat exchanger can be composed of a shell, tube bundle, tube sheet, and end caps. During operation, based on heat conduction and fluid flow, the cold fluid and hot fluid flow through different paths (tube side and shell side). The cold fluid enters the shell-and-tube heat exchanger from one side, passes through the tube wall, and is separated from the flow path of the hot fluid within the tube by a certain distance. Heat conduction within this distance allows heat energy to be transferred from the hot fluid to the cold fluid, causing the temperature of the hot fluid to decrease while the temperature of the cold fluid increases. The fluid flow direction can be either co-current or counter-current, with counter-current flow achieving higher heat exchange efficiency.

[0041] Please see Figure 1In a preferred embodiment, a hydrogen cross-line (first pipeline 331 and corresponding second pipeline 332) is added at the inlet of the dechlorinator 21, connecting it to the gas-liquid separator 3. A cross-line 213 is added at the outlet of the dechlorinator 21 to the air cooler 33. When the dechlorinator 21 malfunctions or reaches the end of its lifespan and requires inspection or refrigerant replacement, the inlet valve of the dechlorinator 21 is first closed, and the corresponding valve of the hydrogen cross-line is opened. Hydrogen circulation is used to replace the hot oil in the dechlorinator 21 with heat exchanger 112 and preheater 111 for oil and gas and heat recovery. When the temperature inside the dechlorinator 21 drops to 150°C, the outlet valve of the dechlorinator 21 is closed, and the cross-line valve corresponding to the cross-line 213 to the air cooler is opened. Hydrogen circulation continues to cool the dechlorinator while simultaneously recovering some of the oil and gas inside. When the temperature inside the dechlorinator 21 drops to 80°C, the inlet hydrogen cross-line valve of the dechlorinator 21 and the cross-line valve on cross-line 213 to the air cooler 33 are closed, and nitrogen from the top of the dechlorinator 21 is used for purging and replacement. By treating the dechlorinator 21 with the aforementioned circulating hydrogen, it is expected that the cooling time of the dechlorinator 21 can be reduced from 7 days to 3 days, saving 190,000 Nm3 of nitrogen, while also reducing the emission of sludge and exhaust gas.

[0042] like Figure 2 As shown, the present invention also provides a method for cooling a dechlorinator using the aforementioned naphtha hydrotreating system, comprising the following steps:

[0043] In response to a control signal that requires the dechlorination unit 2 to be cut off, the inlet valve of the dechlorination unit 2 is closed and the corresponding valve on the second pipeline 322 is opened, so that the compressor 35 circulates hydrogen to the dechlorination unit 2, and the hot oil in the dechlorination unit 2 is replaced to the heat exchanger 112 and the preheater 111 to recover oil and heat.

[0044] In response to the first temperature control signal of the dechlorination unit 2, the outlet valve of the dechlorination unit 2 is closed and the air cooler 33 is opened to circulate and cool the dechlorination unit 2 through the condensed hydrogen.

[0045] In response to the second temperature control signal of the dechlorination unit 2, the inlet valve of the dechlorination unit 2 and the cross line 213 connected to the air cooler 33 are closed, and nitrogen gas is blown in from the top of the dechlorination unit 21 for purging and replacement.

[0046] In one embodiment of the present invention, during the process of accelerating the replacement and cooling efficiency of the dechlorinator 21 using the naphtha hydrogenation system of the present invention, a hydrogen cross-line (first pipeline 331 and corresponding second pipeline 332) is added at the inlet of the dechlorinator 21, that is, connected to the gas-liquid separation device 3, and a cross-line 213 is added at the outlet of the dechlorinator 21 to the air cooler 33. When the dechlorinator 21 malfunctions or reaches the end of its service life and needs to be inspected or replaced, the inlet valve of the dechlorinator 21 is first closed, and the corresponding valve of the hydrogen cross-line is opened. The hot oil in the dechlorinator 21 is replaced by hydrogen circulation to the heat exchanger 112 and the preheater 111 for oil and gas and heat recovery. When the first temperature control signal is collected, the outlet valve of the dechlorinator 21 is closed, and the cross-line valve corresponding to the cross-line 213 to the air cooler is opened to continue cooling with hydrogen circulation, while recovering some of the oil and gas in the dechlorinator. When the second temperature control signal is acquired, the inlet hydrogen cross-line valve of the dechlorinator 21 and the cross-line valve on the cross-line 213 to the air cooler 33 are closed, and nitrogen from the top of the dechlorinator 21 is used for purging and replacement.

[0047] In summary, this invention, through the cooperation of the gas-liquid separation device 3, the dechlorination device 2, and the heating reaction device 1, enables the hydrogen separated by the gas-liquid separation device to be pressurized and circulated into the dechlorination device 2. This hydrogen circulation then displaces the hot oil in the dechlorinator 21 into the heat exchanger 112 and preheater 111, achieving oil and gas recovery and heat recovery. Furthermore, when the temperature inside the dechlorinator drops to 150°C, the outlet valve of the dechlorinator 21 is closed, and the cross-line valve 213 leading to the air cooler 33 is opened, continuing to use hydrogen circulation for cooling while simultaneously recovering some of the oil and gas inside the dechlorinator 21. Finally, when the temperature inside the dechlorinator 21 drops to 80°C, the inlet hydrogen cross-line valve of the dechlorinator 21 and the cross-line valve to the air cooler 33 are closed, and nitrogen from the top of the dechlorinator 21 is used for purging and replacement. This accelerates the cooling rate of naphtha hydrodechlorination and replacement, reduces the cooling time of the dechlorinator 21, saves nitrogen consumption, and reduces oily waste and exhaust emissions. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0048] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A naphtha hydrogenation system, characterized in that, include: A heating reaction apparatus (1) is used to heat and react the feed material to remove impurities. The heating reaction apparatus (1) includes a heating device (11) and a reactor (12). The heating device (11) preheats, exchanges heat, and heats the feed material. The inlet end of the reactor (12) is connected to the outlet end of the heating device (11) to remove impurities from the heated feed material. The heating device (11) includes a preheater (111). 11) It is provided with a feed inlet to preheat the raw material added through the feed inlet; a heat exchanger (112), the inlet end of the heat exchanger (112) is connected to the outlet end of the preheater (111) to heat the preheated raw material; and a heating furnace (113), the inlet end of the heating furnace (113) is connected to the outlet end of the heat exchanger (112), and the outlet end of the heating furnace (113) is connected to the dechlorination device (2) to heat the heat-exchanged raw material to a preset temperature; A dechlorination device (2), the inlet of which is connected to the outlet of the heating reaction device (1); and The gas-liquid separation device (3) has an outlet pipeline (23) of the dechlorination device (2) that passes through the heating reaction device (1) and is connected to the gas-liquid separation device (3). The gas-liquid separation device (3) includes a liquid phase outlet (31) and a gas phase outlet (32). The gas phase outlet (32) is connected to the inlet end of the heating reaction device (1) and the dechlorination device (2) respectively, so as to circulate the hydrogen from the gas phase outlet (32) to the dechlorination device (2) and recover the oil, gas and heat of the gas-liquid separation device (3) through the heating reaction device (1). The inlet of the dechlorination device (2) is connected to the outlet of the heating reaction device (1); the dechlorination device (2) includes: a dechlorinator (21), the inlet of which is connected to the outlet of the reactor (12), the outlet of which is connected to the gas-liquid separation device (3) via the outlet pipeline (23), and the outlet of which is also provided with an oily waste outlet (211) and a flare outlet (212); and a purge port (22), which is connected to the inlet of the dechlorinator (21). (22) Includes a nitrogen inlet (221) and a steam inlet (222) so that when the inlet connecting the dechlorinator (21) and the reactor (12) is closed, nitrogen is blown in through the top of the dechlorinator (21) for purging and replacement; the outlet pipeline (23) passes through the heat exchanger (112) and the preheater (111) in sequence and is connected to the gas-liquid separation device (3); the outlet end of the dechlorinator (21) is also provided with a cross line (213), and the outlet end of the cross line (213) is connected to the outlet pipeline (23) after heat exchange by the heat exchanger (112) and the preheater (111). The gas-liquid separation device (3) includes: an air cooler (33), the outlet end of the outlet pipeline (23) being connected to the inlet end of the air cooler (33); a gas-liquid separator (34), the inlet end of the gas-liquid separator (34) being connected to the outlet end of the air cooler (33), the liquid phase outlet (31) and the gas phase outlet (32) being respectively provided on the gas-liquid separator (34); and a compressor (35), the inlet end of the compressor (35) being connected to the gas phase outlet (32), the outlet end of the compressor (35) being respectively connected to the heat exchanger (1) 12) and the inlet end of the dechlorination device (2); the compressor (35) is a circulating hydrogen compressor, the compressor (35) includes a first pipeline (331) and a second pipeline (332), the inlet end of the first pipeline (331) is connected to the outlet end of the compressor (35), the inlet ends of the two second pipelines (332) are connected to the first pipeline (331), the outlet end of one second pipeline (332) is connected to the heat exchanger (112), and the outlet end of the other second pipeline (332) is connected to the inlet end of the dechlorination device (2).

2. The naphtha hydrogenation system according to claim 1, characterized in that: The heat exchanger (112) is a shell-and-tube heat exchanger.

3. A method for cooling a dechlorinator using the naphtha hydrotreating system according to any one of claims 1-2, characterized in that, Includes the following steps: In response to a control signal that requires the dechlorination unit (2) to be cut off, the inlet valve of the dechlorination unit (2) is closed and the corresponding valve on the second pipeline (332) is opened, so that the compressor (35) circulates hydrogen to the dechlorination unit (2), and the hot oil in the dechlorination unit (2) is replaced to the heat exchanger (112) and the preheater (111) to recover oil and heat. In response to the first temperature control signal of the dechlorination device (2), the outlet valve of the dechlorination device (2) is closed and the air cooler (33) is opened to circulate and cool the dechlorination device (2) through the condensed hydrogen. In response to the second temperature control signal of the dechlorination device (2), the inlet valve of the dechlorination device (2) and the cross line (213) connected to the air cooler (33) are closed, and nitrogen gas is blown in from the top of the dechlorinator (21) for purging and replacement.

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