A catalytic slurry oil hydroprocessing process and a needle coke production method

Abstract

The application discloses a catalytic oil slurry hydrogenation treatment process and a needle coke production method. The catalytic oil slurry hydrogenation treatment process is characterized in that: first, catalytic oil slurry is cut to obtain first fraction oil slurry and second fraction oil slurry; the first fraction oil slurry is introduced into a hydrogenation refining reaction zone to react, and after separation, refined first fraction oil slurry is obtained; the refined first fraction oil slurry is mixed with the second fraction oil slurry to obtain hydrogenated oil slurry. The application further provides a needle coke production method, in which the obtained hydrogenated oil slurry is introduced into a delayed coking unit as feed to produce needle coke. The method can inhibit the generation of powder coke in the needle coke production process, and the obtained needle coke product has the advantages of low volatile content, high hardness and high wear resistance, and can improve the operation cycle of the whole device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of petroleum processing, and particularly relates to a catalytic cracking slurry oil hydroprocessing process and a needle coke production method. BACKGROUND

[0002] Catalytic cracking slurry is a by-product of catalytic cracking process. The annual processing capacity of catalytic cracking in China exceeds 150 million tons, and the yield of slurry accounts for about 3-5% of the processing capacity of catalytic cracking, and the yield of slurry shows a trend of increasing year by year. At present, catalytic cracking slurry is mainly used as boiler fuel oil or blending material for delayed coking, which is a rough processing method and does not fully utilize the value of slurry. Because slurry is rich in polycyclic aromatic hydrocarbons, it can be used as a potential high-quality raw material for producing high-value-added chemical products such as carbon black, carbon fiber and needle coke.

[0003] Needle coke is a kind of petroleum coke with excellent performance, which has the advantages of small thermal expansion coefficient, large particle density, small porosity and easy graphitization, and is mainly used for high-power and super-high-power graphite electrodes for electric furnace steelmaking and special carbon products. As a raw material for graphite electrodes, needle coke must have a low sulfur content. According to the coking mechanism of needle coke, the raw material for producing needle coke requires a high aromatic content and a low ash content. Catalytic cracking slurry is almost aromatic hydrocarbon with side chains, which is the best material for producing needle coke.

[0004] Due to the increasing quality and weight of crude oil, the sulfur content of catalytic cracking slurry is usually high, and needs to be treated by hydrodesulfurization. At the same time of hydrodesulfurization of catalytic cracking slurry, the aromatic hydrocarbons in the slurry should be as much as possible to be kept from being hydrogenated and saturated.

[0005] CN110628461A discloses a method for selectively hydrodesulfurizing oil slurry to retain aromatic hydrocarbons, which removes catalyst particles in the oil slurry by ultrasonic assisted centrifugal operation, and then separates gum, asphaltene and residual catalyst powder in the oil slurry from ideal components rich in aromatic hydrocarbons by vacuum distillation and double solvent extraction. The method has a long process flow and is difficult to be applied in large-scale industrial application. SUMMARY

[0006] Based on the above situation, the purpose of the present application is to provide a catalytic oil slurry hydroprocessing process and a needle coke production method, which can inhibit the generation of powdered coke in the production process of needle coke, and the obtained needle coke product has the advantages of low volatile content, high hardness and high wear resistance, so as to improve the operation cycle of the whole device.

[0007] The technical scheme provided by the present application includes the following aspects:

[0008] The present application first provides a catalytic oil slurry hydroprocessing process, which includes the following steps:

[0009] (1) the catalytic oil slurry is cut and separated to obtain first fraction oil slurry and second fraction oil slurry;

[0010] (2) the first fraction oil slurry obtained in step (1) is introduced into a hydrofining reaction zone, and is reacted with a hydrofining catalyst filled in the hydrofining reaction zone in the presence of hydrogen to obtain a hydrofining effluent, and the hydrofining effluent is separated into a refined first fraction oil slurry;

[0011] (3) the refined first fraction oil slurry obtained in step (2) is mixed with the second fraction oil slurry obtained in step (1) to obtain a hydroprocessing oil slurry.

[0012] Further, as a specific embodiment, the cutting temperature of the first fraction oil slurry and the second fraction oil slurry in step (1) is 410-500°C, preferably 430-475°C, and further preferably 450-470°C.

[0013] Further, as a specific embodiment, the catalytic oil slurry in step (1) is preferably subjected to a solid impurity removal treatment before being cut, and the solid impurity removal treatment can adopt any one of the existing solid impurity removal treatments in the art, such as a filtration method, and the filtration device for purification can adopt at least one of a metal screen, an inorganic membrane filter, a hollow fiber membrane filter, etc.; the solid content of the catalytic oil slurry after the solid impurity removal treatment is less than 50 mg / L.

[0014] Further, as a specific embodiment, the hydrofining reaction zone in step (2) is provided with one or more hydroprocessing reactors, and the hydroprocessing reactor preferably adopts a fixed bed hydroprocessing reactor.

[0015] Further, as a specific embodiment, the hydrofining catalysts used in the hydrofining reaction zone in step (2) generally include a carrier and a hydrogenation metal component, the hydrogenation metal includes a metal in Group VIB and a metal in Group VIII in the Periodic Table of Elements, wherein the metal in Group VIB can be W and / or Mo, the content of the metal in Group VIB is 2wt% to 25wt% in terms of metal oxide, preferably 3wt% to 18wt%; the metal in Group VIII can be Co and / or Ni, the content of the metal in Group VIII is 0.5wt% to 6wt% in terms of metal oxide, preferably 1wt% to 4wt%. The hydrofining catalysts should be pre-sulfurized before use to ensure that the hydrogenation active metals are in a sulfided state during the reaction. The carrier used in the hydrofining catalysts is generally selected from one or more inorganic refractory oxides, such as at least one selected from alumina, amorphous silica-alumina, silica, titania, etc. The hydrofining catalysts can be selected from commercially available ordinary commercial catalysts in the field, or can be prepared according to general knowledge in the field. Commercial catalysts that can be selected include YJ-8, YJ-9, YJ-10, HSDS-8, HSDS-9, and HSDS-10 hydrofining catalysts developed and produced by SINOPEC (Dalian) Petroleum Chemical Research Institute (FRIPP).

[0016] Further, as a specific embodiment, the hydrofining reaction zone in step (2) is also filled with a hydrogenation guard catalyst, and the hydrogenation guard catalyst and the hydrofining catalyst are sequentially filled in the direction of the liquid phase material flow.

[0017] Further, as a specific embodiment, the hydrogenation guard catalyst used in the hydrofining reaction zone can be an FZC series guard catalyst developed and produced by SINOPEC (Dalian) Petroleum Chemical Research Institute (FRIPP), or can be prepared according to prior art. The hydrogenation guard catalyst generally uses a porous refractory inorganic oxide such as alumina as a carrier, and oxides of metals in Group VIB and / or Group VIII such as W, Mo, Co, Ni, etc. as active components, and can also optionally add other various additives such as elements P, Si, F, B, etc.

[0018] Further, as a specific embodiment, the reaction conditions of the hydrofining reaction zone in step (2) are as follows: the reaction pressure is 2.0MPa to 8.0MPa, preferably 3.0MPa to 6.0MPa; the reaction temperature is 250°C to 450°C, preferably 300°C to 400°C; the hydrogen / oil volume ratio is 50:1 to 1200:1, preferably 200:1 to 1000:1; the volume space velocity is 0.1h -1 -1 to 1.2h -1 .

[0019] Further, as a specific embodiment, the mixing ratio of the refined first fraction oil slurry in step (3) and the second fraction oil slurry obtained in step (1) is generally controlled to be 100-120:10-40, and the mixing ratio ensures that the sulfur content of the hydrogenation catalytic oil slurry is not greater than 0.5wt%.

[0020] The present application also provides a method for producing needle coke, comprising the following steps:

[0021] S1: preparing a refined first fraction oil slurry, comprising the following steps:

[0022] (1) obtaining a first fraction oil slurry and a second fraction oil slurry by cutting and separating the catalytic oil slurry;

[0023] (2) feeding the first fraction oil slurry obtained in step (1) into a hydrofining reaction zone, and allowing the first fraction oil slurry to react with a hydrofining catalyst filled in the hydrofining reaction zone in the presence of hydrogen, and then separating the reaction effluent to obtain a refined first fraction oil slurry;

[0024] S2: feeding the refined first fraction oil slurry obtained in step (2) and the second fraction oil slurry obtained in step (1) into a delayed coking unit as feed to produce needle coke, and separating the coking reaction product to obtain gas, light fraction oil, heavy fraction oil and tail oil.

[0025] Further, as a specific embodiment, the delayed coking unit in step S2 comprises at least one heating furnace, one fractionating column and two coke towers, and at least one coke tower is always kept in a reaction stage and at least one coke tower is kept in a decoking stage.

[0026] Further, as a specific embodiment, the heavy fraction oil obtained in step S2 can be divided into two streams, one of which is recycled back to the hydrofining reaction zone to mix with the first fraction oil slurry for hydrogenation reaction, and the other of which is fed into the coke tower of the delayed coking unit as needle coke raw material for coking reaction, and the ratio of the heavy fraction oil recycled back to the hydrofining reaction zone to the heavy fraction oil as needle coke raw material can be adjusted according to the load of the device.

[0027] Further, as a specific embodiment, the outlet temperature of the heating furnace is 470-550°C, preferably 490-505°C; the overhead pressure of the coke tower is 0.01-2.5MPa, preferably 0.2-1.0MPa, and the coke tower is operated at constant pressure or variable pressure, and when variable pressure is adopted, the pressure change rate is 0.01-50MPa / h, preferably 0.2-5MPa / h; the recycle weight ratio is 0.05-1.0, preferably 0.2-0.7; and the reaction cycle is 10-38h, preferably 16-27h. The recycle weight ratio refers to the weight ratio of the tail oil recycled back to the coke tower to the heavy fraction oil fed into the coke tower.

[0028] Further, as a specific embodiment, in step S2, the refined first fraction oil slurry obtained in step (2) can be mixed with the second fraction oil slurry obtained in step (1) and then heated by a heating furnace in a delayed coking unit before entering a coke drum.

[0029] Further, as a specific embodiment, in step S2, the refined first fraction oil slurry obtained in step (2) is heated by a heating furnace in a delayed coking unit before entering a coke drum, and the second fraction oil slurry obtained in step (1) directly enters a fractionating tower in the delayed coking unit without being heated by the heating furnace.

[0030] Further, as a specific embodiment, in step S2, the refined first fraction oil slurry obtained in step (2) is further subjected to cutting treatment, and the fraction less than 350℃ is removed before being used as a raw material for producing needle coke.

[0031] Further, as a specific embodiment, in step S2, the cutting temperature points of the light fraction oil and the heavy fraction oil are 330-380℃, and preferably 345-355℃.

[0032] Further, as a specific embodiment, in step S2, the cutting temperature points of the heavy fraction oil and the tail oil are the cutting temperature points of the first fraction and the second fraction of the oil slurry, 410-500℃, preferably 430-475℃, and further preferably 450-470℃.

[0033] Compared with the prior art, the catalytic oil slurry hydroprocessing process and the needle coke production method provided by the present application have one or a combination of several advantages, which are embodied in the following aspects:

[0034] (1) In the process method of the present application, the catalytic oil slurry is first subjected to appropriate cutting treatment, and then the first fraction oil slurry is separately subjected to hydroprocessing. On the one hand, compared with full fraction oil slurry, this can reduce the severity of hydroprocessing operation, reduce operating costs and operating difficulty. On the other hand, the second fraction oil slurry is not subjected to hydroprocessing, which can avoid the loss of polycyclic aromatic hydrocarbons in the oil slurry. Since the second fraction oil slurry is not subjected to hydrorefining treatment, the phenomenon of a large shift in distillation range of the second fraction oil slurry due to hydrogenation can be avoided. When the refined first fraction oil slurry and the second fraction oil slurry are used as needle coke raw materials to produce needle coke, the proportion of light components produced by cracking and gasification during coke drum reaction is reduced, which can effectively reduce the linear velocity of the coke drum, reduce the amount of entrainment, and reduce the amount of foam and powdered coke in the tower.

[0035] (2) In the process of the present invention, since the second distillate oil slurry has a relatively high degree of condensation, the energy consumption of the coking process is small, which is conducive to maintaining the coking tower at a high temperature. This can effectively increase the condensation reaction depth of the coking feed, reduce the volatile content in the needle coke product, and improve the hardness and abrasion resistance of the needle coke product. At the same time, the increase in the temperature of the coking tower can reduce the height and amount of foam in the tower, which can further inhibit the formation of powdered coke.

[0036] (3) In the process method of the present invention, since the heavy component oil slurry is not hydrorefined, the operating severity of the hydrorefining reaction zone can be greatly reduced. At the same time, the coking phenomenon caused by the high content of heavy component gum asphaltenes in the catalytic oil slurry can be avoided, thereby greatly improving the service life of the hydrorefining catalyst and extending the stable operation cycle of the oil slurry hydrorefining unit. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the catalytic cracking slurry hydrotreating process provided by the present invention.

[0038] Figure 2 This is a polarizing microscope image of the needle-shaped coke product obtained in Example 1 of the present invention.

[0039] Figure 3 This is a polarizing microscope image of the needle-shaped coke product prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0040] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0041] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0042] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (e.g., rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0043] In the present text, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to define a particular position or relative relationship. In other words, in some embodiments, the terms "first", "second", etc. can also be interchanged with each other.

[0044] In the present text, all numerical values of parameters (e.g. quantities or conditions) should be understood as being modified in all cases by the term "about", whether or not the term "about" actually appears before the numerical value.

[0045] In the present text, the sulfur content is determined by the method of GB / T 24526; the Hardgrove grindability index is determined by the method of GBT 2565; the particle strength is determined by the method of Appendix B in T / ZGTS 002; and the volatile matter content is determined by the method of YB / T 5189.

[0046] In the present text, the powder coke rate is the ratio of the mass of coke powder passing through a 10-mesh sieve to the total mass of coke after sieving.

[0047] In the present text, the polarizing microscope used is a Zeiss Axio Scope.A1 model.

[0048] In the present text, the various catalysts involved can be selected from commercial catalysts according to their properties, or can be prepared according to the knowledge in the art. The hydrogenation guard catalysts of the hydrofining process can be selected from commercial catalysts such as FZC-100, FZC-102A, FZC-103, etc. hydrogenation guard catalysts developed and produced by Sinopec (Dalian) Petroleum Chemical Research Institute Co., Ltd.; the hydrofining catalysts of the hydrofining reaction zone can be selected from commercial catalysts such as YJ-8, YJ-9, YJ-10, HSDS-8, HSDS-9 and HSDS-10, etc. hydrofining catalysts developed and produced by Sinopec (Dalian) Petroleum Chemical Research Institute Co., Ltd.

[0049] As Figure 1As shown, the purified catalytic oil slurry 1 enters the fractionating column 2, and after fractionation, the first fraction oil slurry 3 and the second fraction oil slurry 4 are obtained. The first fraction oil slurry 3 is mixed with the recycled hydrogen 5 and the fresh hydrogen 6 to obtain a hydrogenation feed, which enters the refining reaction zone 7 to contact with the hydrogenation catalyst for hydrogenation reaction. The obtained hydrogenation refined effluent 8 enters the separation system 9 (which generally includes a high-pressure separator, a low-pressure separator and a stripping column) for separation, and after separation, the hydrogen-rich gas 10 and the refined first fraction oil slurry 12 are obtained; wherein the hydrogen-rich gas 10 obtained by separation enters the purification unit 11 to remove impurities (such as hydrogen sulfide) therein, and then returns to the hydrogenation refining reaction zone 7 as the recycled hydrogen 5 for further use. The refined first fraction oil slurry 12 separated out is mixed with the second fraction oil slurry 4 to obtain the needle coke raw material 13, which is heated by the heating furnace 14 and then enters the coking tower 15 to obtain needle coke and coking oil gas 16. The coking oil gas 16 enters the coking fractionating column 17, and the gas component 18, the light fraction oil 19, the heavy fraction oil 20 and the tail oil 21 are separated out. The tail oil 21 is heated by the heating furnace 14 again and then enters the coking tower 15 for coking treatment. The heavy fraction oil 20 can be divided into two streams, one of which is recycled to the hydrogenation refining reaction zone to be mixed with the first fraction oil slurry for treatment, and the other of which is heated by the heating furnace 14 and then enters the coke tower 15 of the delayed coking unit for coking reaction.

[0050] Example 1

[0051] The purified oil slurry A was used as the raw material, and the specific properties of the purified oil slurry A are shown in Table 1. The cutting temperature of the first fraction oil slurry and the second fraction oil slurry was 450°C, the hydrogenation refining reaction zone was filled with the hydrogenation guard FZC-103 and the hydrogenation refining catalyst HSDS-9, the process conditions of the hydrogenation refining reaction zone and the delayed coking unit are shown in Table 2, and the product properties are shown in Table 4. Figure 2 The fiber structure of the prepared needle coke product observed under a polarizing microscope.

[0052] Example 2

[0053] The purified oil slurry A was used as the raw material, and the specific properties of the purified oil slurry A are shown in Table 1. The cutting temperature of the first fraction oil slurry and the second fraction oil slurry was 460°C, the hydrogenation refining reaction zone was filled with the hydrogenation guard FZC-103 and the hydrogenation refining catalyst HSDS-8, the process conditions of the hydrogenation refining reaction zone and the delayed coking unit are shown in Table 2, and the product properties are shown in Table 4.

[0054] Example 3

[0055] The purified oil slurry B was used as raw material, and the specific properties of the purified oil slurry B are shown in Table 1. The cutting temperature of the first fraction oil slurry and the second fraction oil slurry was 445°C, the hydrogenation protection agent FZC-103 and the hydrogenation refining catalyst YJ-9 were filled in the hydrogenation refining reaction zone, and the process conditions of the hydrogenation refining reaction zone and the delayed coking unit are shown in Table 2, and the product properties are shown in Table 4.

[0056] Example 4

[0057] The purified oil slurry B was used as raw material, and the specific properties of the purified oil slurry B are shown in Table 1. The cutting temperature of the first fraction oil slurry and the second fraction oil slurry was 455°C, the hydrogenation protection agent FZC-103 and the hydrogenation refining catalyst YJ-8 were filled in the hydrogenation refining reaction zone, and the process conditions of the hydrogenation refining reaction zone and the delayed coking unit are shown in Table 2, and the product properties are shown in Table 4.

[0058] Comparative Example 1

[0059] The same raw material and the same catalyst filling scheme as in Example 1 were used, and the difference was that the purified oil slurry A was not cut, and the whole fraction purified oil slurry A was all fed into the hydrogenation refining reaction zone, and the whole fraction oil slurry after hydrogenation refining was used as the needle coke raw material. The process conditions of the hydrogenation refining reaction zone and the delayed coking unit are shown in Table 3, and the product properties are shown in Table 5. Figure 3 The fiber structure of the needle coke product prepared using the needle coke raw material was observed under a polarizing microscope.

[0060] Comparative Example 2

[0061] The same raw material and the same catalyst filling scheme as in Example 2 were used, and the difference was that the light component oil slurry and the heavy component oil slurry were not cut using the fractionating column, and the whole fraction purified oil slurry was all fed into the hydrogenation refining reaction zone, and the whole fraction oil slurry after hydrogenation refining was used as the product needle coke feedstock. The process conditions of the hydrogenation process are shown in Table 3, and the product properties are shown in Table 5.

[0062] Comparative Example 3

[0063] The same raw material and the same catalyst filling scheme as in Example 2 were used, and the difference was that the first fraction oil slurry cut was not fed into the hydrogenation refining reaction zone, but the second fraction oil slurry was fed into the hydrogenation refining reaction zone, and the second fraction oil slurry after hydrogenation refining was mixed with the unrefined first fraction oil slurry to be used as the needle coke raw material. The process conditions of the hydrogenation refining reaction zone and the delayed coking unit are shown in Table 3, and the product properties are shown in Table 5.

[0064] Table 1 Raw material properties

[0065]

[0066]

[0067] Table 2 Process conditions for examples

[0068] Item Example 1 Example 2 Example 3 Example 4 Hydrofining reaction zone Pressure, MPa 3 5 4 6 Reaction temperature, °C 335 355 360 385 airspeed, h -1 ]]> 0.35 0.7 0.4 0.6 Hydrogen to oil volume ratio 800 400 800 400 Delayed coking unit Heater outlet temperature, °C 490 505 490 505 Coker drum pressure, MPa 1.0 0.2 1.0 0.2 Recycle weight ratio 0.2 0.7 0.4 0.6 Coking cycle, h 24 24 24 24

[0069] Table 3 Process conditions for comparative examples

[0070] Item Comparative Example 1 Comparative Example 2 Comparative Example 3 Hydrofining reaction zone Pressure, MPa 3 5 5 Reaction temperature, °C 335 355 355 airspeed, h -1 ]]> 0.35 0.7 0.7 Hydrogen to oil volume ratio 800 400 400 Delayed coking unit Heater outlet temperature, °C 490 505 Coker drum pressure, MPa 1.0 0.2 Recycle weight ratio 0.2 0.7 Coking cycle, h 24 24

[0071] Table 4 Product properties for examples

[0072] Item Example 1 Example 2 Example 3 Example 4 Needle coke feed properties Sulfur content, m% 0.43 0.45 0.45 0.46 Total aromatics, m% 90.1 89.6 91.7 90.6 Needle coke properties Fines rate, m% 20.6 21.2 22.8 22.3 Volatile matter, m% 3.85 3.94 3.88 4.02 Hardgrove grindability index, HGI 75 72 76 74

[0073] Table 5 Product properties for comparative examples

[0074] Item Comparative Example 1 Comparative Example 2 Comparative Example 3 Needle coke feed properties Sulfur content, wt% 0.42 0.45 0.61 Total aromatics, wt% 89.2 88.7 90.1 Needle coke properties Fines rate, wt% 36.8 37.4 - Volatile matter, wt% 6.44 6.65 - Hardgrove grindability index, HGI 120 119 -

[0075] The needle coke raw material obtained in Comparative Example 3 does not meet the requirement for producing needle coke because the sulfur content is greater than 0.5, and the coking experiment is not performed because the raw material properties are unqualified. Through the comparative analysis of the above description and the examples and comparative examples, it is found that the present application can achieve excellent desulfurization effect of oil slurry hydrogenation, and at the same time, the heavy aromatic hydrocarbons in the oil slurry can be retained to the maximum extent while the total aromatic hydrocarbon loss of the oil slurry is as little as possible, thereby meeting the requirement for producing high-quality needle coke raw material. The needle coke product prepared has the advantages of low volatile content, high hardness and high wear resistance.

Claims

1. A method for producing needle coke, comprising the following steps: S1: Preparation of refined first fraction oil slurry, including the following steps; (1) The catalytic oil slurry is cut and separated to obtain the first fraction oil slurry and the second fraction oil slurry; the cutting temperature of the first fraction oil slurry and the second fraction oil slurry is 410-500℃; (2) The first fraction oil slurry obtained in step (1) enters the hydrorefining reaction zone and reacts with the hydrorefining catalyst packed therein in the presence of hydrogen. The hydrorefining effluent obtained from the reaction is separated into gas and liquid to obtain the refined first fraction oil slurry. S2: The refined first fraction slurry obtained in step (2) and the second fraction slurry obtained in step (1) are fed into the delayed coking unit to produce needle coke. The coking reaction products are separated to obtain gas, light distillate oil, heavy distillate oil and tail oil; among which... The mixing ratio of the refined first fraction oil slurry obtained in step (2) to the second fraction oil slurry obtained in step (1) is controlled to be 100-120:10-40.

2. The method for producing needle coke according to claim 1, characterized in that: The delayed coking unit in step S2 includes at least one heating furnace, one fractionation tower and two coke towers, with at least one coke tower always in the reaction stage and at least one coke tower in the decoking stage.

3. The method for producing needle coke according to claim 1, characterized in that: The heavy distillate oil obtained in step S2 is divided into two streams. One stream is recycled back to the hydrorefining reaction zone and mixed with the first distillate oil slurry for hydrorefining. The other stream is used as needle coke feedstock and enters the coke tower of the delayed coking unit for coking.

4. The method for producing needle coke according to claim 2, characterized in that: The outlet temperature of the heating furnace is 470℃~550℃, the top pressure of the coke tower is 0.01MPa~2.5MPa, the circulation weight ratio is 0.05~1.0, and the reaction cycle is 10h~38h.

5. The method for producing needle coke according to claim 2, characterized in that: The outlet temperature of the heating furnace is 490℃~505℃, the top pressure of the coke tower is 0.2MPa~1.0MPa, the circulation weight ratio is 0.2~0.7, and the reaction cycle is 16h~27h.

6. The method for producing needle coke according to claim 1, characterized in that: In step S2, the refined first fraction oil slurry obtained in step (2) is mixed with the second fraction oil slurry obtained in step (1) and then heated together in the heating furnace in the delayed coking unit before entering the coke tower.

7. The method for producing needle coke according to claim 1, characterized in that: In step S2, the refined first fraction slurry obtained in step (2) is heated by the heater in the delayed coking unit and then enters the coking tower. The second fraction slurry obtained in step (1) directly enters the coking tower in the delayed coking unit without being heated by the heater.

8. The method for producing needle coke according to claim 1, characterized in that: In step S2, the refined first fraction oil slurry obtained in step (2) is further processed by cutting to remove fractions with a temperature lower than 350°C before being used as raw material for the production of needle coke.

9. The method for producing needle coke according to claim 1, characterized in that: The cutting temperature of the first and second fraction oil slurries in step (1) is 430-475℃.

10. The method for producing needle coke according to claim 1, characterized in that: The cutting temperature of the first and second fraction oil slurries in step (1) is 450-470℃.

11. The method for producing needle coke according to claim 1, characterized in that: Before cutting the catalytic slurry in step (1), a solids removal treatment is performed, and the solid content of the catalytic slurry after the solids removal treatment is less than 50 mg / L.

12. The method for producing needle coke according to claim 1, characterized in that: The mixing ratio of the refined first fraction oil slurry obtained in step (2) and the second fraction oil slurry obtained in step (1) is such that the sulfur content of the mixed oil slurry is not greater than 0.5 wt%.

13. The method for producing needle coke according to claim 1, characterized in that: In step (2), one or more hydrogenation reactors are set up in the hydrogenation refining reaction zone. The hydrogenation reactors are fixed-bed hydrogenation reactors.

14. The method for producing needle coke according to claim 1, characterized in that: The hydrorefining reaction zone in step (2) is filled with a hydrorefining catalyst and a hydroprotectant. The hydroprotectant and the hydrorefining catalyst are filled sequentially according to the direction of liquid material flow.

15. The method for producing needle coke according to claim 1, characterized in that: The reaction conditions in the hydrorefining reaction zone in step (2) are as follows: reaction pressure 2.0–8.0 MPa, reaction temperature 250–450 °C, hydrogen-to-oil volume ratio 50:1–1200:1, and volume hourly space velocity 0.1–1.2 h⁻¹. -1 .

16. The method for producing needle coke according to claim 1, characterized in that: The reaction conditions in the hydrorefining reaction zone in step (2) are as follows: reaction pressure 3.0–6.0 MPa, reaction temperature 300–400 °C, hydrogen-to-oil volume ratio 200:1–1000:1, and volume hourly space velocity 0.3–1.0 h⁻¹. -1 .

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