Online sulfur supplementing system and sulfur supplementing method for low-sulfur raw oil hydrogenation device

Abstract

The invention discloses an online sulfur supplementing system of a low-sulfur raw oil hydrogenation device. The sulfur supplementing system comprises a sulfur injection homogenizing tank, wherein sulfur, sulfur supplementing purified oil and other components form a homogeneous vulcanizing agent; the sulfur injection pump is used for feeding the homogeneous vulcanizing agent into the sulfur injection mixer and / or the circulating reinjection sulfur homogenization tank; raw oil and a homogeneous vulcanizing agent are mixed in the sulfur injection mixer to form sulfur injection raw oil; the raw oil filter is used for filtering sulfur injection raw oil, and one stream of purified oil enters a downstream hydrogenation device; the heater is used for heating the recycled purified oil, and the heated recycled purified oil is respectively used as backwashing oil and is injected into the sulfur injection homogenizing tank; and the backwash oil filter is used for filtering the backwash oil containing the solid particles from the raw oil filter. According to the online sulfur supplementing system, sulfur serves as a vulcanizing agent, the vulcanizing agent is continuously and smoothly conveyed to the hydrogenation reactor, and stable operation of the sulfur supplementing process in production of the hydrogenation device is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of oil refining hydrogenation technology, and relates to an online sulfur replenishment system and method for a low-sulfur feedstock hydrogenation unit. Background Technology

[0002] The active metal components of the catalyst used in hydrogenation units exhibit high activity in their sulfide state; therefore, the catalyst must maintain this sulfide state during normal operation. When the sulfur on the catalyst reaches equilibrium with the hydrogen sulfide in the circulating hydrogen during hydrogenation, the high-valence metal sulfide on the catalyst is preserved. However, when the hydrogen sulfide content in the circulating hydrogen is too low (generally less than 300 ppm), the partial pressure of hydrogen sulfide decreases, disrupting this equilibrium. Hydrogen then reduces the metal sulfides on the catalyst to lower-valence metals, or even to elemental metals, causing the catalyst to lose activity and affecting the reaction efficiency. In the hydrogenation of low-sulfur feedstocks (such as low-sulfur coal tar and wax oil), the amount of hydrogen sulfide generated during hydrogenation is relatively small, resulting in extremely low hydrogen sulfide content in the circulating hydrogen. Therefore, to prevent the reduction of the catalyst metal sulfides, the reactor needs to continuously replenish the sulfiding agent to ensure sufficient hydrogen sulfide partial pressure in the circulating hydrogen, generally maintaining a hydrogen sulfide concentration of 300-500 ppm to achieve the desired hydrogenation reaction effect.

[0003] Commonly used sulfurizing agents include carbon disulfide, dimethyl disulfide, and elemental sulfur. Dimethyl disulfide and carbon disulfide are highly toxic, pose significant risks, and are expensive. In contrast, sulfur is less toxic, easier to transport and handle, has a higher safety factor, and is readily available and inexpensive. However, using sulfur as a sulfurizing agent presents several problems. First, sulfur is solid at room temperature and pressure and requires heating to above 119°C to become liquid and fluid. If the temperature drops, the sulfur will solidify, leading to blockages or pump damage. Second, sulfur injected into pipelines cannot mix thoroughly with the oil. The oil-insoluble sulfur aggregates into large droplets that sink within the pipeline, adhering to the pipe walls and slowly depositing to form sulfur clumps, causing blockages. Therefore, developing a safe, efficient, and reliable sulfur injection system and process for hydrogenation units, ensuring the continuous and smooth delivery of the sulfurizing agent to the hydrogenation reactor, is crucial for guaranteeing the performance of the hydrogenation catalyst and the long-term stable operation of the unit.

[0004] CN 106047403 B discloses a method and equipment for injecting sulfur additive into a hydrocracking reactor in a direct coal liquefaction process. In this method, intermediate feedstock hydrogen sulfide is directly injected into the hydrocatalytic cracking reactor as a sulfurizing agent during direct coal liquefaction, shortening the process, reducing energy consumption, and saving the amount of hydrogen consumed in existing technologies where elemental sulfur is used as a sulfur additive to react with hydrogen in the hydrocracking reactor to generate hydrogen sulfide. However, using hydrogen sulfide as a sulfurizing agent presents significant safety hazards in terms of operation and metering.

[0005] CN215312228U discloses a coal tar hydrogenation liquid sulfur injection device, including a shell, a heating steam coil and a condensate coil installed inside the shell, the heating steam coil and the condensate coil being connected together, a dosing port being provided at the top of the shell, a submersible pump and a stirrer being connected to the top of the shell, the lower end of the submersible pump extending into the shell, and the stirring blades at the lower end of the stirrer extending into the shell, ensuring continuous and stable operation of the sulfur injection system during production, but this technology cannot guarantee that the sulfur precipitation and crystallization problems caused by temperature difference will occur after the liquid sulfur is injected into the raw material oil pipeline.

[0006] CN113897211A and CN206204237U disclose sulfur injection systems and methods for biodiesel hydrogenation and anthracene oil hydrogenation, respectively. However, neither of them considers the potential precipitation and crystallization of sulfur in the feedstock oil transportation system after sulfur injection, which could very likely cause pipeline blockage and pump damage, affecting the continuous and stable operation of the device. Summary of the Invention

[0007] This invention proposes an online sulfur replenishment system and method for a low-sulfur feedstock hydrotreating unit. Using sulfur as a sulfurizing agent, the system continuously and smoothly delivers the sulfurizing agent to the hydrotreating reactor in an economical and efficient manner through a sulfur injection homogenization and blending system and a sulfur injection mixing and solids removal treatment. This ensures the stable operation of the sulfur replenishment process in the hydrotreating unit and extends the service life of the hydrotreating catalyst and the operating cycle of the hydrotreating unit.

[0008] According to the first objective of the present invention, the present invention provides an online sulfur replenishment system for a low-sulfur feedstock hydrotreating unit.

[0009] Specifically, the online sulfur replenishment system of the low-sulfur feedstock hydrotreating unit includes: A sulfur homogenization tank is used to receive liquid sulfur, a second-path purified oil, a first-path homogeneous sulfurizing agent, and backwash oil filtrate as feed, and to form a homogeneous sulfurizing agent therein; wherein, the sulfur homogenization tank includes a feed pipeline for receiving liquid sulfur, a feed pipeline for receiving the second-path purified oil, a circulation pipeline for receiving the first-path homogeneous sulfurizing agent, a feed pipeline for receiving the backwash oil filtrate, and a discharge pipeline for discharging the homogeneous sulfurizing agent. Sulfur injection pumps are used to feed homogeneous vulcanizing agents to sulfur injection mixers and / or circulating sulfur homogenization tanks. The sulfur injection mixer is used to receive and mix the feed oil and the second homogeneous sulfurizing agent to obtain the sulfur injection feed oil; it includes a feed oil inlet pipeline and a second homogeneous sulfurizing agent inlet pipeline; The raw material oil filter is used to filter the sulfur injection raw material oil; the raw material oil filter includes a sulfur injection raw material oil inlet pipeline, a backwashing pipeline for the filtered recycled purified oil, a removal pipeline for discharging the sulfur-replenished purified oil, and a discharge pipeline for discharging the backwashing oil containing solid particles. The heater is used to heat the recycled purified oil. The heated recycled purified oil is then used to backwash the switched-out raw material oil filter and injected into the sulfur injection homogenization tank to mix and homogenize with the raw material liquid sulfur. A backwash oil filter is used to receive and filter backwash oil containing solid particles from a feed oil filter; it includes a backwash oil feed line containing solid particles, a sludge discharge line, and a backwash oil filtrate discharge line.

[0010] Furthermore, the sulfur replenishment system also includes a sulfur injection regulating valve. This valve is located on the second sulfur injection agent pipeline at the outlet of the sulfur injection pump and is used to control the injection volume of homogeneous sulfurizing agent. The sulfur injection regulating valve controls the injection volume of homogeneous sulfurizing agent based on the data signal from the hydrogen sulfide detector in the circulating hydrogen of the hydrogenation unit.

[0011] Furthermore, when using solid sulfur, the sulfur injection system also includes a sulfur melting tank in which solid sulfur is heated and melted to obtain liquid sulfur.

[0012] Furthermore, the sulfur homogenization tank is equipped with heating and heat tracing facilities, and preferably a heating tank with a stirring device is provided.

[0013] Furthermore, the sulfur homogenization tank is equipped with a liquid level detection device and a weight detection device.

[0014] Furthermore, the sulfur injection mixer is a liquid-liquid mixer, preferably a pipeline mixer.

[0015] Furthermore, the raw oil filter is a filter with a backwashing function.

[0016] Furthermore, the feedstock oil filter is preferably provided in two or more sets, such as feedstock oil filter I and feedstock oil filter II. The two or more sets of crude oil filters are used interchangeably, with one set filtering the sulfur injection feedstock oil and the other set using the sulfur replenishment purification oil (as reuse purification oil) from other feedstock oil filters for backwashing.

[0017] Furthermore, the first pipeline at the outlet of the feedstock oil filter is preferably connected to the inlet pipeline of the feedstock oil hydrotreating booster pump.

[0018] According to a second objective of the present invention, the present invention provides an online sulfur replenishment method for a low-sulfur feedstock hydrogenation unit, wherein the sulfur replenishment system for the hydrogenation unit described above is applied.

[0019] Specifically, the online sulfur replenishment method for the low-sulfur feedstock hydrogenation unit includes the following steps: (1) Liquid sulfur first enters the sulfur homogenization tank and is fully mixed with the sulfur replenishment and purification oil to form a homogeneous sulfurizing agent. Then, after being pressurized by the sulfur injection pump, it is divided into two paths: the first path is circulated back into the sulfur homogenization tank to enhance the mixing and homogenization effect of liquid sulfur and purification oil; the second path enters the sulfur injection mixer through the sulfur injection regulating valve to control the flow rate. (2) After the homogeneous sulfurizing agent and the feed oil are mixed in the sulfur injection mixer, they enter the feed oil filter for treatment. The particulate impurities in the feed oil and some of the sulfur that precipitates during cooling are intercepted by the filter. The filtered and purified oil (i.e., the sulfur supplement feed oil) is divided into two paths. The first path enters the subsequent hydrogenation process, and the second path enters the purified oil heater for heating. The heated purified oil is divided into two paths. The first path enters the switched feed oil filter for backwashing, and the second path is injected as the sulfur supplement purified oil into the sulfur injection homogenization tank to mix and homogenize with liquid sulfur. (3) The particles trapped in the raw material oil filter in step (2) are periodically backwashed with purified oil. The flushing liquid enters the backwash oil filter. The trapped material in the backwash oil filter is treated as sludge discharge. The filtrate is returned to the sulfur injection homogenization tank for recycling.

[0020] Furthermore, when solid sulfur is used as the sulfur source in step (1), a sulfur melting tank needs to be set up before the sulfur injection homogenization tank. The solid sulfur is first liquefied and then enters the sulfur injection homogenization tank.

[0021] Furthermore, the operating temperature of the sulfur homogenization tank in step (1) is 130-160℃.

[0022] Furthermore, the mass ratio of purified oil to sulfur in step (1) is 2 / 1 to 20 / 1.

[0023] Furthermore, in step (1), the second-path sulfur injection regulating valve is controlled by the feedback signal of the hydrogen sulfide content in the circulating hydrogen of the reaction system to maintain the hydrogen sulfide content in the circulating hydrogen of the reaction system at 300-1000 ppm, preferably 300-500 ppm.

[0024] Furthermore, the filtration accuracy of the raw oil filter in step (2) is 1 to 100 μm, preferably 2 to 50 μm.

[0025] Furthermore, the purified oil in step (2) is heated to a temperature of 120-160°C after being treated by the heater.

[0026] Furthermore, in step (2), it is preferable to have two or more sets of raw oil filters, which are switched according to the pressure difference between the inlet and outlet of the filter. When the pressure difference reaches the set value, the cut-off raw oil filter is backwashed, and the sulfur-added raw oil is switched to another raw oil filter. The pressure difference set value is generally an inlet and outlet pressure difference ≥ 0.05 MPa, preferably 0.05 to 0.5 MPa.

[0027] Furthermore, the particles intercepted in the raw oil filter in step (3) are particulate impurities in the raw oil and are treated as waste oil sludge; the filtrate in the raw oil filter is purified oil and liquid sulfur, which are returned to the sulfur injection homogenization tank for recycling.

[0028] The online sulfur replenishment system and method for low-sulfur crude oil hydrotreating units proposed in this invention can be used for sulfur replenishment during the production process of hydrotreating units, and is especially suitable for sulfur replenishment operations during the production process of low-sulfur or low-sulfur high-nitrogen feedstock hydrotreating units, such as coal tar hydrotreating, wax oil hydrotreating, and anthracene oil hydrotreating units.

[0029] The technical principle of online sulfur replenishment in the hydrogenation unit proposed in this invention is as follows: Based on extensive experimental research, the inventors of this application discovered that feedstock oil has a certain solubility for sulfur. For the low-sulfur and high-nitrogen feedstock oil system such as coal tar, wax oil, and anthracene oil described in this invention, the solubility of sulfur in the feedstock oil at different temperatures was measured to be 0.5–8 g (sulfur) / 100 g (feedstock oil). To maintain the hydrogen sulfide content in the circulating hydrogen of the subsequent hydrogenation unit reaction system at 300–1000 ppm, only 0.06–0.21 g (sulfur) / 100 g (feedstock oil) needs to be injected to meet production requirements. Therefore, the sulfur-dissolving capacity of the feedstock oil can meet the actual sulfur demand. However, complete sulfur dissolution requires a certain amount of time, and when liquid sulfur at temperatures above 120°C is injected into a low-temperature (approximately 50°C) feedstock oil system, even with a high solubility in the feedstock oil, a certain proportion of sulfur will still precipitate out due to rapid cooling. Therefore, this invention, on the one hand, regulates the amount of sulfur injected through a sulfur injection homogenization and blending system to ensure that the amount of sulfur dissolved in the feed oil meets the sulfur replenishment requirements of the hydrotreating unit; on the other hand, through sulfur injection mixing and solids removal treatment, the low-temperature sulfur that has precipitated is first filtered by the feed oil filter, and then the feed oil filter is backwashed with high-temperature recycled purified oil to reuse the retained sulfur. This economically and efficiently delivers sulfur to the hydrotreating reactor in dissolved form continuously and smoothly, ensuring the long-term stable operation of the sulfur replenishment process in the hydrotreating unit.

[0030] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses sulfur as a sulfurizing agent. Through a sulfur injection homogenization and blending system and sulfur injection mixing and solids removal treatment, the sulfurizing agent is delivered to the hydrogenation reactor in an economical and efficient manner, ensuring the stable operation of the online sulfur replenishment process of the hydrogenation unit and effectively extending the service life of the hydrogenation catalyst and the operating cycle of the hydrogenation unit.

[0031] 2. This invention utilizes a crude oil filter to first trap particulate impurities and sulfur that precipitates during cooling in the feed oil. Then, purified oil is used for backwashing, discharging the particulate impurities and precipitated sulfur from the feed oil through the pipeline to the backwash filter. In the backwash filter, the precipitated sulfur is heated and liquefied, and together with the purified oil, it is returned to the sulfur injection homogenization tank for recycling. This process resolves the issue of solid particulate impurities in the feed oil while preventing lumpy sulfur from entering subsequent systems, ensuring long-term continuous and stable operation of the unit.

[0032] 3. This invention enables precise online real-time sulfur replenishment of the hydrogenation unit by real-time monitoring of the hydrogen sulfide concentration in the circulating hydrogen and controlling the injection amount of the sulfiding agent, thus avoiding the risk of hydrogenation catalyst reduction by hydrogen. Compared with traditional periodic sulfur replenishment, this invention has the advantages of flexible and accurate operation. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the sulfur replenishment system of the low-sulfur feedstock hydrogenation unit of the present invention.

[0034] In the diagram, the numbers correspond to the following: 1-Sulfur injection pipeline, 2-Sulfur injection homogenization tank, 3-Sulfur injection pump, 4-Sulfur injection mixer, 5-Purified oil heater, 6-1# feed oil filter, 7-2# feed oil filter, 8-Backwash oil filter, 9-Sulfur injection regulating valve, 10-Feed oil pipeline, 11-Purified oil pipeline, 12-Sulfur replenishment feed oil pipeline (into subsequent feed oil pipeline), 13-Purified oil reuse pipeline, 14-First purified oil pipeline, 15-Second purified oil pipeline, 16-First sulfur injection agent pipeline, 17-Second sulfur injection agent pipeline, 18-Backwash oil filtrate pipeline, 19-Sludge discharge pipeline. Detailed Implementation

[0035] The online sulfur replenishment system and method of the low-sulfur feedstock hydrogenation unit of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but this does not limit the present invention. Example 1

[0036] This embodiment provides a detailed description of the sulfur replenishment system of the low-sulfur feedstock hydrogenation unit of the present invention.

[0037] like Figure 1 As shown, the present invention provides a sulfur replenishment system for a low-sulfur feedstock hydrotreating unit. The sulfur replenishment system includes a sulfur injection homogenization tank 2, a sulfur injection pump 3, a sulfur injection mixer 4, a purified oil heater 5, a No. 1 feedstock oil filter 6, a No. 2 feedstock oil filter 7, a backflushing oil filter 8, and a sulfur injection regulating valve 9.

[0038] The inlet of the sulfur homogenizing tank 2 is connected to the sulfur injection pipeline 1, and the outlet of the sulfur homogenizing tank 2 is connected to the inlet of the sulfur injection pump 3. The outlet of the sulfur injection pump 3 is divided into two paths: one path goes through the first sulfur injection agent pipeline 16 and is connected to the sulfurizing agent circulation inlet of the sulfur homogenizing tank 2, and the other path goes through the second sulfur injection agent pipeline 17 and is connected to the sulfurizing agent inlet of the sulfur injection mixer 4.

[0039] The feed oil inlet of the sulfur injection mixer 4 is connected to the feed oil pipeline 10. The outlet of the sulfur injection mixer 4 is divided into two paths after passing through the feed oil filter 6 or 7: the first path enters the subsequent hydrogenation process through the sulfur replenishment feed oil pipeline 12, and the second path is connected to the inlet of the purified oil heater 5 through the purified oil reuse pipeline 13 for purified oil reuse.

[0040] The outlet of the purified oil heater 5 is divided into two paths. The first purified oil pipeline 14 is connected to the backwash inlet of the raw material oil filter 6 and 7, and the second purified oil pipeline 15 is connected to the purified oil inlet of the sulfur injection homogenization tank 2.

[0041] The backwash outlets of the raw material oil filters 6 and 7 are connected to the inlet of the backwash oil filter 8. The filtrate outlet of the backwash oil filter 8 is connected to the sulfur homogenization tank 2 via the backwash oil filtrate pipeline 18. The filter residue outlet of the backwash oil filter 8 is connected to the sludge discharge pipeline 19. The sulfur injection regulating valve 9 is installed on the second sulfur injection agent pipeline 17 at the outlet of the sulfur injection pump 3, and is used to control and regulate the injection amount of homogeneous sulfurizing agent. The sulfur injection regulating valve 9 controls the injection amount of sulfurizing agent based on the data signal from the hydrogen sulfide detector in the circulating hydrogen. Example 2

[0042] This embodiment provides a detailed description of the online sulfur replenishment method for the low-sulfur feedstock hydrogenation unit of the present invention.

[0043] Combination Figure 1 The working process of the sulfur replenishment method for the hydrogenation device provided by the present invention is as follows: (1) Liquid sulfur first enters the sulfur homogenization tank 2 and mixes thoroughly with the purified oil to form a homogeneous sulfurizing agent at 120-160℃. Then, after being pressurized by the sulfur injection pump 3, it is divided into two paths: one path is circulated back into the sulfur homogenization tank 2 through the first sulfur injection agent pipeline 16 to enhance the mixing and homogenization effect of liquid sulfur and purified oil; the other path flows through the second sulfur injection agent pipeline 17 and enters the sulfur injection mixer 4 through the sulfur injection regulating valve 9 to control the flow rate. (2) The homogeneous sulfurizing agent (temperature of 120-160℃) entering the sulfur injection mixer 4 is mixed with the raw material oil (temperature of about 50℃) to obtain the sulfur injection raw material oil, which is then processed by the raw material oil filter 6. The particulate impurities in the raw material oil and some of the sulfur that precipitates during cooling are intercepted by the raw material oil filter. The filtered and purified oil is divided into two streams: one stream flows through the sulfur replenishment raw material oil pipeline 12 into the subsequent hydrogenation process, and the other stream flows through the purified oil reuse pipeline 13 into the purified oil heater 5 for heating treatment and is heated to 120-160℃. The heated reuse purified oil (temperature of 120-160℃) is divided into two paths: the first path enters the cut-out raw material oil filter 7 through the first purified oil pipeline 14 for backwashing operation, and the second path enters the second purified oil pipeline 15 as the sulfur replenishment purified oil and is injected into the sulfur injection homogenization tank 4 to mix and homogenize with the raw material liquid sulfur. (3) The particles trapped in the raw material oil filter 6 are periodically backwashed with purified oil. The backwashing liquid enters the backwash oil filter 8. The trapped material in the backwash oil filter 8 is discharged as sludge oil through the sludge oil discharge pipeline 19. The filtrate is returned to the sulfur injection homogenization tank 2 for recycling through the backwash oil filtrate pipeline 18.

[0044] In the above process, the homogeneous sulfur injection agent is prepared by mixing purified oil and sulfur at a mass ratio of 2 / 1 to 20 / 1. The amount of sulfur injection agent is adjusted by the sulfur injection regulating valve 9 according to the hydrogen sulfide concentration data detected in the circulating hydrogen of the hydrogenation unit, so as to maintain the hydrogen sulfide content in the circulating hydrogen of the hydrogenation system at the operating requirement of 300 to 1000 ppm.

[0045] The above process utilizes the solubility of sulfur in feedstock oil. Through a sulfur injection homogenization and blending system and sulfur injection mixing and solids removal treatment, the amount of dissolved sulfur meets the sulfur replenishment requirements of the hydrogenation catalyst, while solving problems such as blockage caused by sulfur agglomeration during the sulfur injection process. This allows for the continuous and smooth delivery of sulfurizing agent to the hydrogenation reactor in an economical and efficient manner, ensuring the stable operation of the sulfur replenishment process in the hydrogenation unit and extending the service life of the hydrogenation catalyst and the operating cycle of the hydrogenation unit.

[0046] Comparative Example 1 Sulfur is used as a sulfiding agent and injected into the feedstock oil pipeline after melting treatment. The feedstock oil after sulfur injection is then pumped into the subsequent hydrogenation unit system. Liquid sulfur at 120-160°C is directly injected into the feedstock oil system at about 50°C. Due to the sudden temperature difference, some sulfur crystals will precipitate. The injected sulfur cannot be supplied to the subsequent hydrogenation unit smoothly. Furthermore, since there is no solids removal facility during the transportation process, the sulfur crystals will sink in the pipeline and slowly accumulate into lumps during long-term operation, causing blockage or even damage to the feedstock oil booster pump, affecting the long-term continuous and stable operation of the unit.

Claims

1. A low sulfur feed oil hydroprocessing plant on-line sulfur make-up system characterized by, The system comprises: a sulfur injection homogenizing tank for receiving liquid sulfur, second-pass purified oil, first-pass homogeneous sulfurizing agent and backwash oil filtrate as feed, and forming homogeneous sulfurizing agent therein; wherein the sulfur injection homogenizing tank comprises a feed line for receiving liquid sulfur, a feed line for receiving second-pass purified oil, a circulation line for receiving first-pass homogeneous sulfurizing agent, a feed line for receiving backwash oil filtrate, and a discharge line for discharging homogeneous sulfurizing agent; a sulfur injection pump for feeding homogeneous sulfurizing agent to a sulfur injection mixer and / or circulating back to the sulfur injection homogenizing tank; a sulfur injection mixer for receiving raw oil and second-pass homogeneous sulfurizing agent and mixing to obtain sulfur-injected raw oil; the sulfur injection mixer comprises a raw oil feed line and a second-pass homogeneous sulfurizing agent feed line; a raw oil filter for filtering sulfur-injected raw oil; the raw oil filter comprises a sulfur-injected raw oil feed line, a backwash filtrate line for backwashing filtered recycled purified oil, a removal line for discharging sulfur-supplemented purified oil, and a discharge line for discharging solid particle-containing backwash oil; a heater for heating recycled purified oil; the heated recycled purified oil is used for backwashing the switched-out raw oil filter and mixing with raw liquid sulfur in the sulfur injection homogenizing tank; a backwash oil filter for receiving and filtering solid particle-containing backwash oil from the raw oil filter; the backwash oil filter comprises a solid particle-containing backwash oil feed line, a dirty oil discharge line and a backwash oil filtrate discharge line.

2. The on-line sulphur make-up system according to claim 1, characterized in that The sulfur injection system further comprises a sulfur injection regulating valve arranged on the second-pass sulfur injection agent line at the outlet of the sulfur injection pump, for controlling the injection amount of homogeneous sulfurizing agent.

3. The on-line sulphur make-up system according to claim 2, characterised in that, The sulfur injection regulating valve controls the injection amount of homogeneous sulfurizing agent according to the hydrogen sulfide detection data signal in the hydrogen circulation of the hydrogenation device.

4. The on-line sulfur make-up system of claim 1 wherein, The sulfur injection system further comprises a molten sulfur tank for heating and melting solid sulfur to obtain liquid sulfur.

5. The on-line sulfur make-up system of claim 1 wherein, The sulfur injection homogenizing tank is provided with heating and heat tracing facilities, and / or The sulfur injection homogenizing tank is provided with liquid level detection equipment and weight detection equipment.

6. The on-line sulfur make-up system of claim 1 wherein, The sulfur injection mixer is a pipeline mixer.

7. The on-line sulfur make-up system of claim 1 wherein, The raw oil filter is provided with two or more groups of filters which are used in turn.

8. The on-line sulfur make-up system of claim 1 wherein, The sulfur-supplemented raw oil line at the outlet of the raw oil filter is connected to the inlet line of the raw oil hydrogenation booster pump.

9. A method for on-line sulfur make-up in a low sulfur feed hydroprocessing unit, characterized by, The low-sulfur raw oil hydrogenation device on-line sulfur supplement system of any one of claims 1-8 is applied.

10. The on-line sulfur make-up process of claim 9 wherein, The method comprises the following steps: (1) Liquid sulfur first enters the sulfur injection homogenizing tank, is fully mixed with sulfur-supplemented purified oil to form homogeneous sulfurizing agent, and is then pressurized by the sulfur injection pump and divided into two passes: the first pass is circulated back to the sulfur injection homogenizing tank to strengthen the mixing and homogenizing effect of liquid sulfur and purified oil; the second pass is controlled by the sulfur injection regulating valve to enter the sulfur injection mixer; (2) The homogeneous vulcanizing agent is mixed with the raw oil in a sulfur injection mixer, and then is introduced into a raw oil filter for treatment. The particulate impurities in the raw oil and the sulfur precipitated during cooling are intercepted by the filter. The filtered oil is divided into two streams. The first stream is introduced into the subsequent hydrotreating process, and the second stream is introduced into a purified oil heater for heating. The heated purified oil is also divided into two streams. The first stream is introduced into the switched-out raw oil filter for backwashing, and the second stream is introduced into the sulfur injection homogenizing tank as a sulfur supplement and is mixed with liquid sulfur. (3) The intercepted particles in the raw oil filter in step (2) are periodically treated by backwashing with the purified oil. The backwashing liquid is introduced into a backwash oil filter. The intercepted particles in the backwash oil filter are treated as waste oil, and the filtrate is returned to the sulfur injection homogenizing tank for recycling.

11. The on-line sulphur make-up process according to claim 10, c h a r a c t e r i s e d b y, The operating temperature of the sulfur injection homogenizing tank in step (1) is 120-160°C.

12. The on-line sulfur make-up process of claim 10 wherein, The mass ratio of the purified oil to the liquid sulfur in step (1) is 2 / 1-20 / 1.

13. The on-line sulfur make-up process of claim 10 wherein, The sulfur injection regulating valve in the second stream in step (1) is controlled by feedback of the hydrogen sulfide content in the reaction system circulating hydrogen, so as to maintain the hydrogen sulfide content in the reaction system circulating hydrogen at 300-1000 ppm.

14. The on-line sulfur make-up process of claim 10 wherein, The filtering accuracy of the raw oil filter in step (2) is 1-100 μm.

15. The on-line sulfur make-up process of claim 10 wherein, The raw oil filter in step (2) is provided with two or more groups, and is switched according to the pressure difference between the inlet and outlet of the filter.

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