Hydrogenation heat exchange assembly and hydrogenation heat exchange system with same

Abstract

A hydrogenation heat exchange assembly comprises a heat exchange device, a raw oil main pipeline and a hydrogen main pipeline, the output end of the raw oil main pipeline is connected with a first raw oil pipeline and a second raw oil pipeline, the output end of the hydrogen main pipeline is connected with a first hydrogen pipeline and a second hydrogen pipeline, the first raw oil pipeline, the second raw oil pipeline, the first hydrogen pipeline and the second hydrogen pipeline are all provided with a first valve, the heat exchange device is a winding pipe heat exchanger with one shell pass and two pipe passes, the two pipe passes are a first pipe pass and a second pipe pass, the inlet end of the first pipe pass is communicated with the outlet end of the first raw oil pipeline and the outlet end of the first hydrogen pipeline, and the inlet end of the second pipe pass is communicated with the outlet end of the second raw oil pipeline and the outlet end of the second hydrogen pipeline. The application further discloses a hydrogenation heat exchange system with the hydrogenation heat exchange assembly. Compared with the prior art, the heat exchanger in the application can adapt to load fluctuation and realize conversion of different processing technologies of pre-furnace hydrogen mixing and post-furnace hydrogen mixing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heat exchange, and particularly relates to a hydrogenation heat exchange assembly and a hydrogenation heat exchange system with the same. BACKGROUND

[0002] Hydrogenation treatment is one of the important treatment methods for petroleum products, which refers to removing sulfur, nitrogen, oxygen and other heteroatoms and metal impurities in oil products under certain temperature, hydrogen partial pressure and catalyst conditions, and saturating olefins and partially hydrogenating aromatic hydrocarbons to improve the use performance of oil products.

[0003] The process of hydrogenation treatment is as follows: after the oil product is mixed with hydrogen, it is sent into a heating furnace to be heated to a specified temperature, and then enters a reactor provided with a catalyst; after the reaction is completed, hydrogen is separated in a separator and recycled by a compressor; and products are separated into hydrogen sulfide, ammonia, water and a small amount of gaseous hydrogen generated in the reaction process in a stabilizing tower.

[0004] The existing hydrogenation heat exchange system is disclosed in the patent application No. CN202110477804.0, namely, the hydrogenation heat exchange system and process using multi-stream winding pipe heat exchanger (application publication No. CN113063309A) and the patent application No. CN202110477790.2, namely, the heat exchange system and process for hydrogenation process (application publication No. CN113267075A).

[0005] The working load of the heat exchanger in the existing hydrogenation heat exchange system generally needs to be maintained at 60-110% of the design load, and it is difficult to maintain the working load above 60% when starting up or when the raw material supply is insufficient. Low load operation often leads to the occurrence of fouling and coking in the heat exchanger, making it difficult for the entire system to operate for a long time. SUMMARY

[0006] The first technical problem to be solved by the present application is to provide a hydrogenation heat exchange assembly to enable the heat exchanger to adapt to load fluctuations in view of the current status of the prior art.

[0007] The second technical problem to be solved by the present application is to provide a hydrogenation heat exchange system with the above hydrogenation heat exchange assembly.

[0008] The technical solution adopted by the present application to solve the above first technical problem is as follows: a hydrogenation heat exchange assembly, comprising a heat exchange device, a raw oil main pipeline for conveying raw oil, and a hydrogen main pipeline for conveying hydrogen, characterized in that:

[0009] The output end of the raw oil main pipeline is connected with a first raw oil pipeline and a second raw oil pipeline;

[0010] The output end of the hydrogen gas main pipeline is connected with a first hydrogen gas pipeline and a second hydrogen gas pipeline;

[0011] A first valve for controlling flow is arranged on each of the first raw oil pipeline, the second raw oil pipeline, the first hydrogen gas pipeline and the second hydrogen gas pipeline.

[0012] The heat exchange device is a spiral wound tube heat exchanger having one shell pass and two tube passes, i.e., a first tube pass and a second tube pass. The inlet end of the first tube pass is connected in communication with the outlet end of the first raw oil pipeline and the outlet end of the first hydrogen gas pipeline, and the inlet end of the second tube pass is connected in communication with the outlet end of the second raw oil pipeline and the outlet end of the second hydrogen gas pipeline.

[0013] The "hydrogen gas" in the present application can be recycled hydrogen (which can contain impurities) output from a hydrogenation device, or hydrogen gas directly accessed from outside.

[0014] To ensure the heat exchange effect, preferably, the heat exchange tubes of the spiral wound tube heat exchanger are spirally wound into multiple layers of spiral tubes from the inside to the outside. Each layer of spiral tube has heat exchange tubes of the first tube pass and the second tube pass, and the heat exchange tubes of the first tube pass and the second tube pass are uniformly distributed in each layer of spiral tube. In this way, the shell pass medium and the medium of each layer of spiral tube are uniformly heat exchanged, and especially when raw oil and hydrogen gas are passed through the first tube pass and only a small amount of hydrogen gas is passed through the second tube pass, the heat exchange effect can be effectively ensured.

[0015] Preferably, a second valve for controlling flow is arranged on each of the raw oil main pipeline and the hydrogen gas main pipeline.

[0016] Further, the outlet end of the first tube pass and the outlet end of the second tube pass are independently separated to form two paths.

[0017] Alternatively, the outlet end of the first tube pass and the outlet end of the second tube pass are combined into one path.

[0018] Preferably, in the state that the outlet end of the first tube pass and the outlet end of the second tube pass are independently separated to form two paths, the hydrogenation heat exchange assembly further comprises:

[0019] A first raw oil bypass pipeline, the input end of which is connected in communication with the first raw oil pipeline and located between the inlet end of the first raw oil pipeline and the first valve on the first raw oil pipeline, and the output end of which is connected in communication with the outlet end of the first tube pass.

[0020] A second raw oil bypass pipeline, the input end of which is connected in communication with the second raw oil pipeline and located between the inlet end of the second raw oil pipeline and the first valve on the second raw oil pipeline, and the output end of which is connected in communication with the outlet end of the second tube pass.

[0021] Both the first and second feedstock bypass lines are equipped with a third valve for flow control. Thus, the third valve can be controlled based on the tube-side outlet temperature of the heat exchanger. For example, when the tube-side outlet temperature is high, the corresponding third valve can be opened, allowing the unheated, low-temperature feedstock to mix with the medium at the tube-side outlet, thereby lowering the temperature of the medium at the tube-side outlet.

[0022] Preferably, the outlet ends of the first tube and the second tube are combined into one; the hydrogenation heat exchanger assembly also includes:

[0023] The third feedstock bypass pipeline has its input end connected to the above-mentioned feedstock main pipeline, and its output end connected to the combined outlet end of the first pipeline and the outlet end of the second pipeline.

[0024] Furthermore, a third valve is installed on the third raw material oil bypass pipeline.

[0025] The technical solution adopted by the present invention to solve the second technical problem mentioned above is as follows: a hydrogenation heat exchange system, including a heating furnace and a hydrogenation reactor connected to the output end of the heating furnace, characterized in that it further includes the hydrogenation heat exchange assembly as described above, the outlet end of the first tube side and the outlet end of the second tube side are connected to the input end of the heating furnace, the inlet end of the shell side of the heat exchange device is connected to the output end of the hydrogenation reactor, and the outlet end of the shell side of the heat exchange device is connected to downstream equipment.

[0026] Preferably, it also includes a furnace bypass pipeline, with its inlet connected to the pipeline between the inlet of the furnace and the tube-side outlet of the heat exchanger, and its outlet connected to the pipeline between the outlet of the furnace and the inlet of the hydrogenation reactor; and a fourth valve for controlling the flow rate is provided on both the furnace bypass pipeline and the pipeline between the inlet of the furnace and the tube-side outlet of the heat exchanger. Thus, when the temperature of the medium at the tube-side outlet is high, it can directly flow through the furnace bypass pipeline.

[0027] Preferably, the outlet ends of the first and second passes are independently separated, forming two separate paths. These two paths are connected to the input end of the heater via their respective pipelines, and both pipelines are equipped with the aforementioned fourth valve. There are also two bypass pipelines for the heater, each equipped with a fourth valve. The input ends of the two bypass pipelines are connected to their respective two bypass pipelines, and their output ends are connected to the pipeline between the output end of the heater and the input end of the hydrogenation reactor. In this way, depending on the operating conditions and the type of oil being processed, the conversion between pre-furnace hydrogen mixing and post-furnace hydrogen mixing processes can be achieved, combining the advantages of both hydrogenation processes and making production more flexible and adaptable.

[0028] Compared with the prior art, the advantages of the present invention are as follows: By adding first and second raw material oil pipelines, first and second hydrogen pipelines, and first valves installed on each pipe box, the output ends of the first raw material oil pipeline and the first hydrogen pipeline are connected to the first tube side of the heat exchanger, and the output ends of the second raw material oil pipeline and the second hydrogen pipeline are connected to the second tube side of the heat exchanger. Thus, when the heat exchanger is operating under normal or high-load conditions, the first valves are open, and the raw material oil and hydrogen are mixed and flow through both tube sides of the heat exchanger; when the heat exchanger is operating under low-load conditions, the flow can be... The required minimum flow rate is achieved by adjusting the flow rates of the gas and liquid phases in different tube passes. For example, the feedstock oil flows only through the first tube pass, while hydrogen flows through both the first and second tube passes. Since all the feedstock oil flows through the first tube pass, the oil-gas mixture feed rate entering the heat exchanger is maintained between 60% and 110% of the normal design rate, solving the problem of low-load, long-cycle operation and ensuring the flow rate to maintain the heat exchanger's efficiency. Because hydrogen passes through the second tube pass, damage to the heat exchanger caused by prolonged exposure to high external pressure and high temperature conditions when a single tube pass of a multi-flow heat exchanger is empty is effectively avoided. Furthermore, this application enables the conversion between pre-furnace hydrogen mixing and post-furnace hydrogen mixing processes. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure of Embodiment 3 of the present invention. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] Example 1:

[0034] like Figure 1 As shown, this is a preferred embodiment of a hydrogenation heat exchange component and a hydrogenation heat exchange system having the component according to the present invention. The hydrogenation heat exchange component includes a heat exchange device 1, a main feedstock oil pipeline 2 for transporting feedstock oil, a main hydrogen pipeline 3 for transporting hydrogen, a first feedstock oil bypass pipeline 51, and a second feedstock oil bypass pipeline 52.

[0035] The second valve 42 for controlling flow rate is arranged on the raw material oil main pipeline 2 and the hydrogen main pipeline 3. The output end of the raw material oil main pipeline 2 is connected with the first raw material oil pipeline 21 and the second raw material oil pipeline 22. The output end of the hydrogen main pipeline 3 is connected with the first hydrogen pipeline 31 and the second hydrogen pipeline 32. The first valve 41 for controlling flow rate is arranged on the first raw material oil pipeline 21, the second raw material oil pipeline 22, the first hydrogen pipeline 31 and the second hydrogen pipeline 32.

[0036] The heat exchange device 1 is a winding pipe heat exchanger with one shell pass and two pipe passes, i.e. the first pipe pass 11 and the second pipe pass 12. The inlet end of the first pipe pass 11 is connected with the outlet end of the first raw material oil pipeline 21 and the outlet end of the first hydrogen pipeline 31. The inlet end of the second pipe pass 12 is connected with the outlet end of the second raw material oil pipeline 22 and the outlet end of the second hydrogen pipeline 32. The outlet end of the first pipe pass 11 and the outlet end of the second pipe pass 12 are independently separated to form two routes. In this embodiment, the heat exchange pipes of the winding pipe heat exchanger are spirally wound into multiple layers of spiral pipes from the inside to the outside. The heat exchange pipes of the first pipe pass 11 and the second pipe pass 12 are arranged in each layer of spiral pipes, and the number of the heat exchange pipes of the first pipe pass 11 and the second pipe pass 12 is the same and alternately distributed in each layer of spiral pipes.

[0037] The input end of the first raw material oil bypass pipeline 51 is connected with the first raw material oil pipeline 21 and located between the inlet end of the first raw material oil pipeline 21 and the first valve 41 on the first raw material oil pipeline 21. The output end of the first raw material oil bypass pipeline 51 is connected with the outlet end of the first pipe pass 11. The input end of the second raw material oil bypass pipeline 52 is connected with the second raw material oil pipeline 22 and located between the inlet end of the second raw material oil pipeline 22 and the first valve 41 on the second raw material oil pipeline 22. The output end of the second raw material oil bypass pipeline 52 is connected with the outlet end of the second pipe pass 12. Meanwhile, the third valve 43 for controlling flow rate is arranged on the first raw material oil bypass pipeline 51 and the second raw material oil bypass pipeline 52.

[0038] The hydrogen heat exchange system of this embodiment has the above-mentioned hydrogen heat exchange assembly, the heating furnace 6, the hydrogenation reactor 7 and the heating furnace bypass pipeline 8.

[0039] The two routes of pipelines from the two pipe passes of the heat exchanger are combined into one route and connected with the input end of the heating furnace 6. The output end of the heating furnace 6 is connected with the input end of the hydrogenation reactor 7. The output end of the hydrogenation reactor 7 is connected with the inlet end of the shell pass of the heat exchange device 1. The outlet end of the shell pass of the heat exchange device 1 is connected with the downstream equipment. The downstream equipment is the prior art, including a hot high-pressure separation tank, a hot low-pressure separation tank, an air cooler, a cold low-pressure separation tank and the like, which will not be described here.

[0040] The input end of the heating furnace bypass pipeline 8 is connected to the pipeline between the input end of the heating furnace 6 and the outlet end of the tube pass of the heat exchange device 1, the output end is connected to the pipeline between the output end of the heating furnace 6 and the input end of the hydrogenation reactor 7, and the fourth valve 44 for controlling the flow rate is arranged on the pipeline between the input end of the heating furnace 6 and the outlet end of the tube pass of the heat exchange device 1 and on the pipeline of the heating furnace bypass pipeline 8. The fourth valve 44 on the pipeline between the input end of the heating furnace 6 and the outlet end of the tube pass of the heat exchange device 1 is arranged on the pipeline between the input end of the heating furnace 6 and the input end of the bypass pipeline 8.

[0041] The heat exchange process of the embodiment is as follows:

[0042] When the working load M in the spiral wound tube heat exchanger satisfies the first working condition of N 60%≤M≤N 110% between the design load N, each first valve 41 is opened, the raw oil and hydrogen gas are mixed and then pass through the two tube passes of the spiral wound tube heat exchanger, and the hydrogen oil ratio in each tube pass is 500-1100 Nm 3 / m 3 (the hydrogen oil ratio can be 500 Nm 3 / m 3 , 1100 Nm 3 / m 3 or any value between 500 and 1100, which is designed according to the actual working condition);

[0043] When the working load M in the spiral wound tube heat exchanger satisfies the second working condition of N 30%≤M<N 60% between the design load N, the first valve 41 on the first raw oil pipeline 21 is opened, the first valve 41 on the second raw oil pipeline 22 is closed, and the first valves 41 on the first and second hydrogen gas pipelines are closed, so that the hydrogen gas is divided into two routes, the first route of hydrogen gas is mixed with the raw oil and then passes through the first tube pass, and the hydrogen oil ratio in the first tube pass is 475-1050 Nm 3 / m 3 (the hydrogen oil ratio can be 475 Nm 3 / m 3 / m 3 or any value between 475 and 1050, which is designed according to the actual working condition); the second route of hydrogen gas passes through the second tube pass, and the flow rate of hydrogen gas in the second tube pass is not less than 0.1 m / s; the hydrogen oil ratio in the hydrogenation reaction is determined by the catalyst performance, when the catalyst performance is certain, the raw oil processing is reduced, and the hydrogen gas can be reduced synchronously. Compared with the first working condition, the flow rate of hydrogen gas changes little under the second working condition because the raw oil only passes through one tube pass.

[0044] When the working load M in the coiled tube heat exchanger and the design load N satisfy the third working condition of M>N 110%, each first valve 41 is opened, the raw oil and hydrogen are mixed and then pass through two tube passages of the coiled tube heat exchanger, and the hydrogen-oil ratio in each tube passage is 450-1000 Nm / m 3 / m 3 ( The hydrogen-oil ratio can be 450 Nm / m 3 / m 3 , 1000 Nm / m 3 / m 3 or any value between 450 and 1000, which is specifically designed according to the actual working condition). In the third working condition, in order to fully exchange heat, the raw oil bypass will be closed, and at this time the hydrogen-oil ratio decreases.

[0045] In the present application, the working load in the coiled tube heat exchanger can be determined from the ratio of the amount of raw oil processed to the design value. In each working condition, the pressure and temperature of the raw oil are generally slightly higher than those of hydrogen.

[0046] In the heat exchanger of the present application, the tube passage inlet temperature is 110-160℃, the tube passage outlet temperature is 320-380℃, the shell passage inlet temperature is 360-420℃, the shell passage outlet temperature is 220-260℃, and the operating pressure is 5-20 MPa.

[0047] When the coiled tube heat exchanger is switched from high load (≥N 60%) to low load (<N 60%), the first tube passage 11 is cleaned first, as follows: all raw oil and most of the hydrogen are passed into the first tube passage 11, a small part of hydrogen with a flow rate of 0.1 m / s is passed into the second tube passage 12 (note that, in addition to ensuring that there is low flow rate hydrogen of 0.1-0.7 m / s in the second tube passage, all other hydrogen is passed into the first tube passage, and the temperature and pressure of the raw oil and hydrogen remain unchanged), and after maintaining for 48-72 h, all hydrogen is passed into the first tube passage 11, all raw oil is input into the second tube passage 12, and after maintaining for 12-24 h, the cleaning of the first tube passage 11 is completed.

[0048] Then the second tube passage is cleaned, as follows: all raw oil and most of the hydrogen are passed into the second tube passage 12, a small part of hydrogen with a flow rate of 0.1-0.7 m / s is passed into the first tube passage 11 (note that, in addition to ensuring that there is low flow rate hydrogen of 0.1-0.7 m / s in the first tube passage, all other hydrogen is passed into the second tube passage, and the temperature and pressure of the raw oil and hydrogen remain unchanged), and after maintaining for 48-72 h, the cleaning of the second tube passage 12 is completed.

[0049] Example Two:

[0050] As Figure 2The image shows a preferred embodiment of a hydrogenation heat exchange component and a hydrogenation heat exchange system having the component according to the present invention. This embodiment is basically the same as the first embodiment, except that in this embodiment, the outlet end of the first tube 11 and the outlet end of the second tube 12 are independently separated to form two paths. The two paths are connected to the input end of the heater 6 through their respective pipelines, and both pipelines are equipped with the aforementioned fourth valve 44. There are also two heater bypass pipelines 8, each equipped with a fourth valve 44. The input ends of the two heater bypass pipelines 8 are respectively connected to the corresponding two pipelines, and the output ends are connected to the pipeline between the output end of the heater 6 and the input end of the hydrogenation reactor 7.

[0051] Example 3:

[0052] like Figure 3 As shown, this is a preferred embodiment three of a hydrogenation heat exchange component and a hydrogenation heat exchange system having the component according to the present invention. This embodiment is basically the same as the first embodiment, except that in this embodiment, the outlet end of the first tube 11 and the outlet end of the second tube 12 are combined into one line, and the combined line is connected to the main feed oil pipeline 2 through a third feed oil bypass line 53, and a third valve 43 is provided on the third feed oil bypass line 53.

Claims

1. A hydrogenation heat exchange assembly comprising a heat exchange device (1), a raw oil main line (2) for conveying raw oil, a hydrogen main line (3) for conveying hydrogen, characterized in that: an output end of the raw oil main line (2) is connected with a first raw oil line (21) and a second raw oil line (22); an output end of the hydrogen main line (3) is connected with a first hydrogen line (31) and a second hydrogen line (32); a first valve (41) for controlling flow rate is arranged on each of the first raw oil line (21), the second raw oil line (22), the first hydrogen line (31) and the second hydrogen line (32); the heat exchange device (1) is a spiral wound tube heat exchanger having one shell side and two tube sides, the two tube sides being a first tube side (11) and a second tube side (12), an inlet end of the first tube side (11) being in communication with an outlet end of the first raw oil line (21) and an outlet end of the first hydrogen line (31), an inlet end of the second tube side (12) being in communication with an outlet end of the second raw oil line (22) and an outlet end of the second hydrogen line (32); the outlet end of the first tube side (11) and the outlet end of the second tube side (12) are independently separated to form two paths; the hydrogenation heat exchange assembly further comprises: a first raw oil bypass line (51), an input end of which is in communication with the first raw oil line (21) and is located between an inlet end of the first raw oil line (21) and a first valve (41) on the first raw oil line (21), and an output end of which is in communication with the outlet end of the first tube side (11); a second raw oil bypass line (52), an input end of which is in communication with the second raw oil line (22) and is located between an inlet end of the second raw oil line (22) and a first valve (41) on the second raw oil line (22), and an output end of which is in communication with the outlet end of the second tube side (12); a third valve (43) for controlling flow rate is arranged on each of the first raw oil bypass line (51) and the second raw oil bypass line (52).

2. A hydrogenation heat exchange assembly comprising a heat exchange device (1), a raw oil main line (2) for conveying raw oil, a hydrogen main line (3) for conveying hydrogen, characterized in that: an output end of the raw oil main line (2) is connected with a first raw oil line (21) and a second raw oil line (22); an output end of the hydrogen main line (3) is connected with a first hydrogen line (31) and a second hydrogen line (32); a first valve (41) for controlling flow rate is arranged on each of the first raw oil line (21), the second raw oil line (22), the first hydrogen line (31) and the second hydrogen line (32); The heat exchange device (1) is a spiral wound tube heat exchanger with one shell side and two tube sides, the two tube sides being a first tube side (11) and a second tube side (12), the inlet end of the first tube side (11) being in communication with the outlet end of a first raw oil pipeline (21) and the outlet end of a first hydrogen pipeline (31), the inlet end of the second tube side (12) being in communication with the outlet end of a second raw oil pipeline (22) and the outlet end of a second hydrogen pipeline (32); The outlet end of the first tube side (11) and the outlet end of the second tube side (12) are merged into one pipeline; The hydrogenation heat exchange assembly further comprises: A third raw oil bypass pipeline (53) having an input end in communication with the raw oil main pipeline (2) and an output end in communication with the one pipeline formed after the outlet end of the first tube side (11) and the outlet end of the second tube side (12) are merged; And the third raw oil bypass pipeline (53) is provided with a third valve (43).

3. Hydrogenation heat exchange assembly according to claim 1 or 2, characterized in that: The heat exchange tubes of the spiral wound tube heat exchanger are spirally wound into multiple layers of spiral tubes from the inside to the outside, each layer of spiral tube has heat exchange tubes of the first tube side (11) and the second tube side (12), and the heat exchange tubes of the first tube side and the second tube side are uniformly distributed in each layer of spiral tube.

4. The hydrogenation heat exchange assembly according to claim 1 or 2, characterized in that: The raw oil main pipeline (2) and the hydrogen main pipeline (3) are each provided with a second valve (42) for controlling flow.

5. A hydrogenation heat exchange system comprising a heating furnace (6) and a hydrogenation reactor (7) connected to the output end of the heating furnace (6), characterized in that The hydrogenation heat exchange assembly of claim 1 or 2, the outlet end of the first tube side (11) and the outlet end of the second tube side (12) are in communication with the input end of the heating furnace (6), the inlet end of the shell side of the heat exchange device (1) is in communication with the output end of the hydrogenation reactor (7), and the outlet end of the shell side of the heat exchange device (1) is connected to downstream equipment.

6. The hydrogenation heat exchange system of claim 5, wherein: The heating furnace bypass pipeline (8) has an input end connected to a pipeline between the input end of the heating furnace (6) and the outlet end of the tube side of the heat exchange device (1), and an output end connected to a pipeline between the output end of the heating furnace (6) and the input end of the hydrogenation reactor (7); and the heating furnace bypass pipeline (8) and the pipeline between the input end of the heating furnace (6) and the outlet end of the tube side of the heat exchange device (1) are each provided with a fourth valve (44) for controlling flow.

7. The hydrogenation heat exchange system of claim 6, wherein: The outlet end of the first tube side (11) and the outlet end of the second tube side (12) are in a state of being independently separated into two pipelines, the two pipelines are in communication with the input end of the heating furnace (6) through respective pipelines, and the fourth valve (44) is provided on both pipelines, the heating furnace bypass pipeline (8) also has two pipelines, and each is provided with a fourth valve (44), the input ends of the two heating furnace bypass pipelines (8) are in communication with the corresponding two pipelines, and the output ends are connected to a pipeline between the output end of the heating furnace (6) and the input end of the hydrogenation reactor (7).

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