Catalytic slurry oil hydrotreating process and needle coke production method

Abstract

The invention discloses a catalytic slurry oil hydrotreating process and a needle coke production method. The catalytic slurry oil hydrotreating process comprises the following steps: firstly, cutting catalytic slurry oil to obtain first distillate slurry oil and second distillate slurry oil; the first distillate oil slurry enters a hydrofining reaction zone for reaction, and refined first distillate oil slurry is obtained after separation; and mixing the refined first distillate oil slurry with the second distillate oil slurry to obtain hydrogenated oil slurry. The invention also provides a production method of the needle coke. The obtained hydrogenated slurry oil is used as a feed to enter a delayed coking unit to produce the needle coke. The method can inhibit the generation of coke breeze in the needle coke production process, the obtained needle coke product has the advantages of low volatile component content, high hardness and high wear resistance, and the operation cycle of the whole device can be prolonged.

Description

Technical Field

[0001] The invention belongs to the field of petroleum processing, and in particular relates to a catalytic cracking oil slurry hydrogenation treatment process and a needle coke production method. Background Art

[0002] Catalytic cracking slurry is a by-product of the catalytic cracking process. The annual processing volume of catalytic cracking in my country exceeds 150 million tons, and the output of slurry accounts for about 3% to 5% of the catalytic cracking processing volume, and the output of slurry shows an increasing trend year by year. At present, catalytic cracking slurry is mainly used as a blending material for boiler fuel oil or delayed coking raw materials. This rough processing method does not give full play to the value of slurry, because slurry is rich in polycyclic aromatic hydrocarbons and can be used as a potential high-quality raw material for the production of 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. It has the advantages of small thermal expansion coefficient, large particle density, small porosity, easy graphitization, etc. It is mainly used for high-power and ultra-high-power graphite electrodes and special carbon products for electric furnace steelmaking. Needle coke, as the raw material of graphite electrode, must have a low sulfur content. According to the coking mechanism of needle coke, the raw materials for producing needle coke are required to have a high aromatic content and a low ash content. Catalytic cracking slurry is almost all aromatics with side chains, which is the best material for producing needle coke.

[0004] As crude oil becomes increasingly inferior and heavier, the sulfur content of catalytic cracking slurry is usually high and needs to be treated with hydrodesulfurization. While hydrodesulfurizing the catalytic cracking slurry, it is also necessary to ensure that the aromatics in the slurry are not overly saturated with hydrogen.

[0005] CN110628461A discloses a method for selective hydrodesulfurization of oil slurry to retain aromatics, wherein the catalyst particles in the oil slurry are removed by ultrasonic-assisted centrifugation operation, and then the colloid, asphaltenes and residual catalyst powder in the oil slurry are separated from the ideal components enriched in aromatics by vacuum distillation and dual solvent extraction. The method has a lengthy process and is difficult to be applied on a large scale in industry. Summary of the invention

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

[0007] The technical solution provided by the present invention includes the following aspects:

[0008] The present invention first provides a catalytic oil slurry hydrotreating process, comprising the following steps:

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

[0010] (2) the first fraction oil slurry obtained in step (1) enters a hydrotreating reaction zone, and in the presence of hydrogen, contacts and reacts with a hydrotreating catalyst loaded therein, and the hydrotreating effluent obtained by the reaction is subjected to gas-liquid separation to obtain a refined first fraction oil slurry;

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

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

[0013] Furthermore, as a specific implementation method, the catalytic oil slurry in step (1) is preferably subjected to a solid-removal treatment before cutting. The solid-removal treatment may adopt any of the existing solid-removal and purification methods in the art, such as a filtration method. The filtration device for purification may adopt at least one of a metal wire mesh, an inorganic membrane filter, a hollow fiber membrane filter, etc.; the solid content of the catalytic oil slurry after the solid-removal treatment is less than 50 mg / L.

[0014] Furthermore, as a specific implementation, one or more hydrogenation reactors are provided in the hydrotreating reaction zone in step (2), and the hydrogenation reactor is preferably a fixed bed hydrogenation reactor.

[0015] Further, as a specific embodiment, the hydrorefining reaction zone in step (2) is filled with a hydrorefining catalyst, which generally includes a carrier and a hydrogenation metal component. Based on the weight of the catalyst, the hydrogenation metal includes a VIB group metal and a VIII group metal in the periodic table, wherein the VIB group metal may be W and / or Mo, and the VIB group metal content is 2wt% to 25wt% in terms of metal oxide, preferably 3wt% to 18wt%; the VIII group metal may be Co and / or Ni, and the VIII group metal content is 0.5wt% to 6wt% in terms of metal oxide, preferably 1wt% to 4wt%. The hydrorefining catalyst should be pre-sulfurized before use to ensure that the hydrogenation active metal is in a sulfurized state during the reaction. The carrier used for the hydrorefining catalyst is generally selected from one or more inorganic refractory oxides, such as at least one selected from alumina, amorphous silica-alumina, silicon oxide, titanium oxide, etc. The hydrotreating catalyst can be selected from common commercial catalysts in the field, or it 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 hydrotreating catalysts developed and produced by Sinopec (Dalian) Research Institute of Petrochemicals Co., Ltd. (FRIPP).

[0016] Furthermore, as a specific implementation, the hydrotreating reaction zone in step (2) is also filled with a hydrotreating protective agent, and the hydrotreating protective agent and the hydrotreating catalyst are sequentially filled in the direction of flow of the liquid phase material.

[0017] Further, as a specific implementation, the hydrogenation protective agent used in the hydrofining reaction zone can be the FZC series protective agent developed and produced by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. (FRIPP), or can be prepared according to the prior art. The hydrogenation protective agent generally uses a porous refractory inorganic oxide such as alumina as a carrier, and oxides of Group VIB and / or Group VIII metals such as W, Mo, Co, Ni, etc. as active components, and various other additives such as P, Si, F, B, etc. can also be selectively added.

[0018] Further, as a specific embodiment, the reaction conditions of the hydrofining reaction zone in step (2) are: reaction pressure of 2.0 to 8.0 MPa, preferably 3.0 to 6.0 MPa; reaction temperature of 250 to 450° C., preferably 300 to 400° C.; hydrogen to oil volume ratio of 50:1 to 1200:1, preferably 200:1 to 1000:1; volume space velocity of 0.1 to 1.2 h -1 , preferably 0.3~1.0h -1 .

[0019] Furthermore, as a specific implementation, 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] Another aspect of the present invention 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) The catalytic slurry oil is cut and separated to obtain a first fraction slurry oil and a second fraction slurry oil;

[0023] (2) the first fraction oil slurry obtained in step (1) enters a hydrotreating reaction zone, and in the presence of hydrogen, contacts and reacts with a hydrotreating catalyst loaded therein, and the hydrotreating effluent obtained by the reaction is subjected to gas-liquid separation to obtain a refined first fraction oil slurry;

[0024] S2: The refined first fraction oil slurry obtained in step (2) and the second fraction oil slurry obtained in step (1) are used as feed to enter a delayed coking unit to produce needle coke, and the coking reaction products are separated 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 includes at least one heating furnace, one distillation tower and two coke towers, and at least one coke tower is always kept in the reaction stage and at least one coke tower is in the decoking stage.

[0026] Furthermore, as a specific implementation method, the heavy distillate oil obtained in step S2 can be divided into two streams, one of which is circulated back to the hydrotreating reaction zone to be mixed with the first distillate oil slurry for hydrogenation reaction, and the other stream is used as a needle coke feedstock to enter the coke tower of the delayed coking unit for coking reaction. The ratio of the heavy distillate oil circulated back to the hydrotreating reaction zone to the heavy distillate oil used as the needle coke feedstock 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℃, preferably 490℃~505℃; the pressure at the top of the coke tower is 0.01MPa~2.5MPa, preferably 0.2MPa~1.0MPa, constant pressure operation or variable pressure operation, when variable pressure operation is adopted, the pressure change rate is 0.01MPa / h~50MPa / h, preferably 0.2MPa / h~5MPa / h; the circulation weight ratio is 0.05~1.0, preferably 0.2~0.7; the reaction period is 10h~38h, preferably 16h~27h. The circulation weight ratio refers to the weight ratio of the tail oil circulating back to the coking tower to the coke tower feed.

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

[0029] Furthermore, as a specific implementation, in step S2, the refined first fraction oil slurry obtained in step (2) is heated in the heating furnace in the delayed coking unit and then enters the coke tower, and the second fraction oil slurry obtained in step (1) directly enters the distillation tower in the delayed coking unit without being heated in the heating furnace.

[0030] Furthermore, as a specific implementation, in step S2, the refined first fraction oil slurry obtained in step (2) is further cut to remove the fraction with a temperature less than 350°C and then used as a raw material for producing needle coke.

[0031] Further, as a specific implementation, the cutting temperature point of the light fraction oil and the heavy fraction oil in step S2 is 330-380°C, preferably 345-355°C.

[0032] Further, as a specific implementation, the cutting temperature point of the heavy fraction oil and tail oil in step S2 is the cutting temperature point of the first fraction and the second fraction of the slurry oil, 410-500°C, preferably 430-475°C, and more preferably 450-470°C.

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

[0034] (1) In the process of the present invention, the catalytic oil slurry is first subjected to appropriate cutting treatment, and then the first fraction oil slurry is subjected to hydrogenation treatment alone. On the one hand, compared with the whole fraction oil slurry, the severity of the hydrogenation operation can be reduced, and the operating cost and difficulty of the operation can be reduced. On the other hand, the second fraction oil slurry is not subjected to hydrogenation treatment, which can avoid the loss of polycyclic aromatic hydrocarbons in the oil slurry. Since the second fraction oil slurry is not subjected to hydrogenation refining treatment, the phenomenon that the distillation range of the second fraction oil slurry is greatly shifted forward 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, when the coke is produced in the coke tower reaction, the proportion of light components produced by cracking and gasification is reduced, which can effectively reduce the linear speed of the coke tower, reduce the amount of mist entrainment, and reduce the amount of foam and powder coke in the tower.

[0035] (2) In the process of the present invention, since the condensation degree of the second fraction oil slurry itself is relatively high, the energy consumption of the coking process is small, which is conducive to keeping the coke tower at a higher temperature, thereby effectively increasing the condensation reaction depth of the coking feed, reducing the volatile content in the needle coke product, and improving the hardness and wear resistance of the needle coke product. At the same time, since the increase in the temperature of the coke tower can reduce the height and amount of the foam layer in the tower, the formation of powdered coke can be further inhibited.

[0036] (3) In the process of the present invention, since the heavy component oil slurry is not subjected to hydrotreating, the operating severity of the hydrotreating reaction zone can be greatly reduced, and the coking phenomenon of the hydrotreating catalyst caused by the excessively high content of heavy component colloidal asphaltene in the catalytic oil slurry can be avoided, thereby greatly improving the service life of the hydrotreating catalyst and extending the stable operation period of the oil slurry hydrogenation unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention provides a schematic diagram of the catalytic cracking oil slurry hydroprocessing process flow.

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

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

[0040] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0041] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0042] In this document, for the convenience of description, spatial relative terms such as "below", "below", "down", "above", "above", "upper", etc. may be used to describe the relationship between one element or feature and another element or feature in the accompanying drawings. It should be understood that the spatial relative terms are intended to include different orientations of the object in use or operation in addition to the orientation depicted in the figure. For example, if the object in the figure is turned over, the element described as being "below" or "below" other elements or features will be oriented "above" the element or feature. Therefore, the exemplary term "below" can include both the below and above directions. Objects may also have other orientations (e.g., rotated 90 degrees or other orientations) and the spatial relative terms used in this document should be interpreted accordingly.

[0043] In this document, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to limit a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second", etc. can also be interchangeable.

[0044]

[0043] All numerical values ​​for parameters (eg, amounts or conditions) herein are to be understood as being modified in all instances by the term "about," whether or not "about" actually appears before the numerical value.

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

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

[0047] In this paper, the polarizing microscope used was Zeiss Axio Scope.A1.

[0048] In this article, the various catalysts involved can be selected from commercial catalysts according to their properties, or they can be prepared according to the knowledge in the field. The hydrogenation protection agent in the hydrorefining process can be selected from commercial catalysts such as FZC-100, FZC-102A, FZC-103 and other hydrogenation protection agents developed and produced by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd.; the hydrorefining catalyst in the hydrorefining reaction zone can be selected from commercial catalysts such as YJ-8, YJ-9, YJ-10, HSDS-8, HSDS-9 and HSDS-10 and other hydrorefining catalysts developed and produced by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd.

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

[0050] Example 1

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

[0052] Example 2

[0053] Purified slurry A is used as raw material, and the specific properties of purified slurry A are shown in Table 1. The cutting temperature of the first fraction slurry and the second fraction slurry is 460°C, the hydrotreating reaction zone is filled with hydrogenation protective agent FZC-103 and hydrotreating catalyst HSDS-8, the process conditions of the hydrotreating 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] Purified slurry B is used as raw material, and the specific properties of purified slurry B are shown in Table 1. The cutting temperature of the first fraction slurry and the second fraction slurry is 445°C, the hydrotreating reaction zone is filled with hydrogenation protective agent FZC-103 and hydrotreating catalyst YJ-9, the process conditions of the hydrotreating 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] Purified slurry B is used as raw material, and the specific properties of purified slurry B are shown in Table 1. The cutting temperature of the first fraction slurry and the second fraction slurry is 455°C, the hydrotreating reaction zone is filled with hydrogenation protective agent FZC-103 and hydrotreating catalyst YJ-8, the process conditions of the hydrotreating 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 materials and catalyst loading scheme as in Example 1 were used, except that the purified slurry oil A was not cut, and all of its whole fraction purified slurry oil A entered the hydrofining reaction zone, and the whole fraction slurry oil after hydrofining was used as the needle coke raw material. The process conditions of the hydrofining 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 made from the needle coke raw material is observed under a polarizing microscope.

[0060] Comparative Example 2

[0061] The same raw materials and catalyst loading scheme as in Example 2 were used, except that no fractionation tower was used to cut out the light component oil slurry and the heavy component oil slurry, and the whole fraction purified oil slurry was all fed into the hydrofining reaction zone, and the whole fraction oil slurry after hydrofining was used as the product needle coke feed. 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 materials and the same catalyst loading scheme as in Example 2 were used, except that the cut first fraction slurry oil was not fed into the hydrotreating reaction zone, but the second fraction slurry oil was fed into the hydrotreating reaction zone, and the hydrotreating second fraction slurry oil was mixed with the unrefined first fraction slurry oil as the raw material for producing needle coke. The process conditions of the hydrotreating 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 of the embodiment

[0068] project Example 1 Example 2 Example 3 Example 4 Hydrotreating reaction zone Pressure, MPa 3 5 4 6 Reaction temperature, °C 335 355 360 385 <![CDATA[Air speed, h -1 > 0.35 0.7 0.4 0.6 Hydrogen to oil volume ratio 800 400 800 400 Delayed coking unit Heating furnace outlet temperature, ℃ 490 505 490 505 Coking tower pressure, MPa 1.0 0.2 1.0 0.2 Cycle weight ratio 0.2 0.7 0.4 0.6 Coking cycle, h 24 24 24 24

[0069] Table 3 Process conditions of comparative example

[0070] project Comparative Example 1 Comparative Example 2 Comparative Example 3 Hydrotreating reaction zone Pressure, MPa 3 5 5 Reaction temperature, °C 335 355 355 <![CDATA[Air speed, h -1 > 0.35 0.7 0.7 Hydrogen to oil volume ratio 800 400 400 Delayed coking unit Heating furnace outlet temperature, ℃ 490 505 Coking tower pressure, MPa 1.0 0.2 Cycle weight ratio 0.2 0.7 Coking cycle, h 24 24

[0071] Table 4 Example product properties

[0072] project 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 Coke 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 Comparative Example Product Properties

[0074] project Comparative Example 1 Comparative Example 2 Comparative Example 3 Needle coke raw material properties Sulfur content, wt% 0.42 0.45 0.61 Total aromatics, wt% 89.2 88.7 90.1 Needle coke properties Coke 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 did not meet the requirements for needle coke production because the sulfur content was greater than 0.5, and the coking experiment was not carried out because the raw material properties were unqualified. Through the above description and comparative analysis of the embodiments and comparative examples, it is found that the present invention can achieve excellent desulfurization effect of slurry hydrogenation, and at the same time, it can retain heavy aromatics in the slurry to the greatest extent while minimizing the loss of total aromatics in the slurry, meeting the requirements for the production of high-quality needle coke raw materials. The obtained needle coke product has the advantages of low volatile content, high hardness and wear resistance.

Claims

1. A catalytic oil slurry hydrotreating process comprising the following steps: (1) The catalytic oil slurry is cut and separated to obtain a first fraction oil slurry and a second fraction oil slurry; (2) The first fraction oil slurry obtained in step (1) enters the hydrotreating reaction zone, and in the presence of hydrogen, contacts and reacts with the hydrotreating catalyst loaded therein, and the hydrotreating effluent obtained by the reaction is separated into gas and liquid to obtain a refined first fraction oil slurry; (3) The refined first fraction slurry oil obtained in step (2) is mixed with the second fraction slurry oil obtained in step (1) to obtain hydrogenated slurry oil.

2. The catalytic oil slurry hydrotreating process according to claim 1, characterized in that: In step (1), the cutting temperature of the first fraction slurry oil and the second fraction slurry oil is 410-500°C, preferably 430-475°C, and more preferably 450-470°C.

3. The catalytic oil slurry hydrotreating process according to claim 1, characterized in that: The catalytic oil slurry in step (1) is subjected to a solid-removal treatment before cutting, and the solid content of the catalytic oil slurry after the solid-removal treatment is less than 50 mg / L.

4. The catalytic oil slurry hydrotreating process according to claim 1, characterized in that: The hydrotreating reaction zone in step (2) is provided with one or more hydrogenation reactors, and the hydrogenation reactor is a fixed bed hydrogenation reactor.

5. The catalytic oil slurry hydrotreating process according to claim 1, characterized in that: The hydrotreating reaction zone in step (2) is filled with a hydrotreating catalyst and an optional hydrotreating protective agent. When the hydrotreating protective agent is filled, the hydrotreating protective agent and the hydrotreating catalyst are sequentially filled in the direction of flow of the liquid phase material.

6. The catalytic oil slurry hydrotreating process according to claim 1, characterized in that: The reaction conditions of the hydrofining reaction zone in step (2) are as follows: reaction pressure of 2.0 to 8.0 MPa, preferably 3.0 to 6.0 MPa; reaction temperature of 250 to 450°C, preferably 300 to 400°C; hydrogen to oil volume ratio of 50:1 to 1200:1, preferably 200:1 to 1000:1; volume space velocity of 0.1 to 1.2 h -1 , preferably 0.3~1.0h -1 .

7. The catalytic oil slurry hydrotreating process according to claim 1, characterized in that: The mixing ratio of the refined first fraction oil slurry in step (3) and the second fraction oil slurry obtained in step (1) is 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%.

8. A method for producing needle coke, comprising the following steps: S1: preparing a refined first fraction oil slurry, comprising the following steps; (1) The catalytic oil slurry is cut and separated to obtain a first fraction oil slurry and a second fraction oil slurry; (2) The first fraction oil slurry obtained in step (1) enters the hydrotreating reaction zone, and in the presence of hydrogen, contacts and reacts with the hydrotreating catalyst loaded therein, and the hydrotreating effluent obtained by the reaction is separated into gas and liquid to obtain a refined first fraction oil slurry; S2: The refined first fraction oil slurry obtained in step (2) and the second fraction oil slurry obtained in step (1) are used as feed to enter a delayed coking unit to produce needle coke. The coking reaction products are separated to obtain gas, light fraction oil, heavy fraction oil and tail oil.

9. The method for producing needle coke according to claim 8, characterized in that: The delayed coking unit in step S2 includes at least one heating furnace, one fractionating tower and two coke towers, and at least one coke tower is always kept in a reaction stage and at least one coke tower is always kept in a decoking stage.

10. The method for producing needle coke according to claim 8, characterized in that: The heavy fraction oil obtained in step S2 is divided into two streams, one of which is circulated back to the hydrotreating reaction zone to be mixed with the first fraction oil slurry for hydrogenation reaction, and the other is used as needle coke raw material to enter the coke drum of the delayed coking unit for coking reaction.

11. The method for producing needle coke according to claim 9, characterized in that: The outlet temperature of the heating furnace is 470°C to 550°C, preferably 490°C to 505°C; the top pressure of the coke tower is 0.01MPa to 2.5MPa, preferably 0.2MPa to 1.0MPa; the circulation weight ratio is 0.05 to 1.0, preferably 0.2 to 0.7; and the reaction period is 10h to 38h, preferably 16h to 27h.

12. The method for producing needle coke according to claim 8, 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 the mixture is heated together in a heating furnace in a delayed coking unit and then enters a coke drum.

13. The method for producing needle coke according to claim 8, characterized in that: In step S2, the refined first fraction oil slurry obtained in step (2) is heated in the heating furnace in the delayed coking unit and then enters the coke drum, and the second fraction oil slurry obtained in step (1) directly enters the distillation tower in the delayed coking unit without being heated in the heating furnace.

14. The method for producing needle coke according to claim 8, characterized in that: In step S2, the refined first fraction oil slurry obtained in step (2) is further cut to remove the fraction with a temperature less than 350°C and then used as a raw material for producing needle coke.

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