Needle coke as well as preparation method and application thereof

Abstract

The invention relates to the field of needle coke production, and discloses needle coke as well as a preparation method and application thereof. The strength of the needle coke is 25-34%; the thermal expansion coefficient of the needle coke is 0.8 * 10 <-6 > / DEG C to 1.2 * 10 <-6 > / DEG C; in the microstructure of the needle coke, the content of the mosaic structure is 0.1%-10%; the content of the small sheet structures is 10%-30%; the content of the large sheet structure is 15-40%; the content of the fine fiber structure is 10%-45%; and the content of the crude fiber structure is 10-45%. The needle coke provided by the invention has better optical structure, thermal expansion coefficient and strength, and is suitable for producing large-diameter and ultrahigh-power graphite electrodes and graphite electrode joints.

Description

Technical Field

[0001] The present invention relates to the field of needle coke production, and particularly to a needle coke, a preparation method thereof, and an application thereof. Background Art

[0002] As an important raw material in the carbon industry, needle coke is widely used in many fields such as aerospace and steelmaking. The graphite products made from it have the characteristics of high density, high strength, high purity, high crystallinity, high electrical and thermal conductivity, low thermal expansion coefficient, low ablation, etc., and are mainly used for the production of high-power and ultra-high-power graphite electrodes for electric arc furnace steelmaking.

[0003] The electrode current density used in high-power electric arc furnace steelmaking is much higher than that used in ordinary power electrodes, which requires the electrode to have high mechanical strength, high thermal conductivity, low resistivity, and low thermal expansion coefficient. Therefore, the steelmaking industry also uses the thermal expansion coefficient and true density of calcined needle coke as the basis for the grade and application range of needle coke. The graphitized products of needle coke have many advantages such as high thermal conductivity, high mechanical strength, small thermal expansion coefficient, and high chemical stability, and are high-quality aggregates for high-power and ultra-high-power electrodes for electric arc furnace steelmaking. The use of ultra-high-power steelmaking technology can reduce the smelting time by about 30%, save more than 50% of the power consumption per ton of steel, and have a small mass loss of the electrode, greatly improving the steelmaking efficiency and reducing energy consumption.

[0004] During the production process of ultra-high-power graphite electrodes, needle coke will experience processes such as kneading and extrusion molding. During this process, some needle coke is crushed, resulting in problems such as poor mechanical strength, high resistance, and low oxidation resistance of ultra-high-power graphite electrodes.

[0005] At present, the production of needle coke mostly adopts the delayed coking process. In the existing technology, its industrial production adopts a one-furnace two-tower process, that is, one heating furnace heats the raw materials for two coke towers, the heating furnace continuously heats the raw materials, and the two coke towers are alternately switched. And when heating the raw materials for one coke tower, the circulating oil needs to be changed in the later stage for pulling coke and drying. Its disadvantages are that part of the circulating oil cokes, the switching between the raw materials and the circulating oil is not clear, the operation is unstable, the pulling coke and drying time is short, etc., resulting in low product quality, mainly manifested as high thermal expansion coefficient (CTE), small particle size, and low strength, and it cannot reach the level of imported needle coke. In addition, the existing needle coke production process flow in China has problems such as complex actual operation, unstable operation, short service life of equipment, and low and unstable product quality. Summary of the Invention

[0006] The present invention aims to overcome the defects existing in the prior art, solve the problems of obtaining high-quality raw materials and improving the quality of needle coke, and provide a needle coke, a preparation method thereof, and an application thereof. The needle coke of the present invention has a better optical structure, thermal expansion coefficient, and strength, and is suitable for the production of large-diameter, ultra-high-power graphite electrodes and graphite electrode joints.

[0007] CN212559472U adds a third coke drum on the basis of the original one heating furnace and two coke drums, adopting the "one furnace and three drums" configuration. The coke pushing uses nitrogen circulating gas for coke pushing and a nitrogen heater for heating. The disadvantage is that the use of purchased nitrogen increases the cost.

[0008] CN102021005B, a method for producing needle coke. The needle coke raw material is heated through heat exchange and a heating furnace and then enters the coke drum. At a certain temperature, the produced needle coke remains in the coke drum, and the produced oil gas enters the fractionating tower to separate gas, naphtha fraction, diesel fraction, and wax oil fraction. One operating cycle of the coke drum is divided into four stages in chronological order. The first is the low-temperature stage; the second is the high-temperature stage; the third is the cooling stage; the fourth is the coke removal and tower warming stage. Corresponding to each stage, different operating conditions of the coke drum and feeds with different properties are adopted. The disadvantage is that the operating conditions change frequently, the device is unstable, and properties such as the thermal expansion coefficient of the needle coke are poor.

[0009] CN108587661A discloses a device and method for preparing needle coke based on the delayed coking process, belonging to the technical field of needle coke. The device includes a coking mixed oil system, a temperature raising and solidifying system, and a 1# coke drum, a 2# coke drum, and a 3# coke drum; the coking mixed oil system is respectively connected to the 1# coke drum, the 2# coke drum, and the 3# coke drum, and the temperature raising and solidifying system is respectively connected to the 1# coke drum, the 2# coke drum, and the 3# coke drum. In the process of preparing needle coke by the delayed coking process, this device and method separately control the process of generating mesophase and the coking process of the coking mixed oil in the coke drum to achieve two-step coking. The disadvantage is that the performance of the prepared needle coke needs to be further improved.

[0010] In order to achieve the above object, on the one hand, the present invention provides a kind of needle coke, the strength of the needle coke is 25%-34%; the thermal expansion coefficient of the needle coke is 0.8×10 -6 / ℃ - 1.2×10 -6 / ℃; in the microscopic structure of the needle coke: the content of the mosaic structure is 0.1%-10%; the content of the small flake structure is 10%-30%; the content of the large flake structure is 15%-40%; the content of the fine fiber structure is 10%-45%; the content of the coarse fiber structure is 10%-45%.

[0011] The second aspect of the present invention provides a method for preparing needle coke, which includes: (1) hydrogenating and separating coking raw materials to obtain hydrogenated light oil and hydrogenated heavy oil; (2) subjecting material A containing the hydrogenated heavy oil to a mesophase growth reaction to obtain mesophase spheres and coking reaction separation oil; (3) subjecting the mesophase spheres to a needle-pulling and coking reaction in the presence of a needle-pulling medium containing the hydrogenated light oil; the needle-pulling medium further includes a reinforcing agent, and the reinforcing agent includes two-dimensional carbon materials; in the needle-pulling medium, the content of the reinforcing agent is 0.003-1 wt%.

[0012] The third aspect of the present invention provides needle coke prepared by the method of the present invention.

[0013] The fourth aspect of the present invention provides the application of the needle coke of the present invention in the production of large-diameter, ultra-high power graphite electrodes and graphite electrode joints.

[0014] The needle coke of the present invention has better optical structure, thermal expansion coefficient and strength, and is suitable for the production of large-diameter, ultra-high power graphite electrodes and graphite electrode joints.

[0015] The method of the present invention is simple and effectively utilizes all raw materials. Description of the Drawings

[0016] Figure 1 is a production flow chart of the needle coke of the present invention. Detailed Embodiments

[0017] The endpoints and any values disclosed in the ranges herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0018] The present invention provides a needle coke, the strength of the needle coke is 25%-34%; the thermal expansion coefficient of the needle coke is 0.8×10 -6 / °C - 1.2×10 -6 / °C; in the microscopic structure of the needle coke: the content of the mosaic structure is 0.1%-10%; the content of the small sheet structure is 10%-30%; the content of the large sheet structure is 15%-40%; the content of the fine fiber structure is 10%-45%; the content of the coarse fiber structure is 10%-45%.

[0019] In the present invention, the inlay structure, small piece structure, large piece structure, fine fiber structure, and thick fiber structure are technical terms well-known in the art. The specific parameter indicators are shown in the following table. Refer to the literature: Changchun Shan, Chunfa Liu, Xiuyun Zhang, et al. Analysis and Research on the Optical Microstructure of Needle Coke [J]. Fuel & Chemical Processes, 2008, (01): 35-38.

[0020]

[0021] According to a preferred embodiment of the present invention, in the microstructure of needle coke: the content of the fiber structure is 20%-90%. For example, in the microstructure of needle coke: the content of the fiber structure is 30%, 40%, 50%, 60%, 70%, 80%.

[0022] The needle coke of the present invention has a better optical structure, thermal expansion coefficient, and strength, and is suitable for the production of large-diameter, ultra-high-power graphite electrodes and graphite electrode joints.

[0023] In the present invention, the needle coke having the aforementioned composition can achieve the purpose of the present invention, and there is no special requirement for the preparation method of the needle coke. A preferred embodiment is demonstrated below, but this does not limit the scope of the present invention. According to a preferred embodiment of the present invention, a method for preparing needle coke includes: (1) separating the coking raw material after hydrogenation to obtain hydrogenated light oil and hydrogenated heavy oil; (2) performing a mesophase growth reaction on the material A containing the hydrogenated heavy oil to obtain mesophase spheres and coking reaction separation oil; (3) performing a pulling-coking and coking reaction on the mesophase spheres in the presence of a pulling-coking medium containing the hydrogenated light oil; the pulling-coking medium further includes a reinforcing agent, and the reinforcing agent includes two-dimensional carbon materials; in the pulling-coking medium, the content of the reinforcing agent is 0.003-1 wt%.

[0024] According to a preferred embodiment of the present invention, the preparation method of the needle coke further includes: fractionating the coking reaction separation oil to obtain coking gas, coking naphtha, coking diesel, coking wax oil, and bottom tower oil; the fractionation conditions of the coking reaction separation oil do not affect the properties of the prepared needle coke, and the fractionation conditions can be operated according to the prior art. For example, the fractionation conditions include: the bottom tower temperature is 300-360°C, the pressure is 0.05-0.2 MPa, and the side line withdrawal temperatures of fractions such as coking naphtha, coking diesel, and coking wax oil can be operated according to the prior art, and will not be elaborated in the present invention.

[0025] In the present invention, in the preparation method of the needle coke, there is no special requirement for the properties of the coking wax oil. A preferred embodiment is demonstrated below, but this does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the 5% distillation temperature of the coking wax oil is 260-350°C, and the 95% distillation temperature of the coking wax oil is 370-440°C.

[0026] In the present invention, in the preparation method of needle coke, the optional range of the composition of the coke-drawing medium is relatively wide. The following is a demonstration, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the method further includes: circulating the coker gas oil back to step (3) and combining it with the hydrotreated light oil as the coke-drawing medium, and the weight ratio of the coker gas oil to the hydrotreated light oil is 1-5:1. By adopting the foregoing technical solution, the prepared needle coke has better optical structure, thermal expansion coefficient and strength, and is suitable for producing large-diameter, ultra-high-power graphite electrodes and graphite electrode joints.

[0027] In the present invention, in the preparation method of needle coke, those skilled in the art know that in order to improve the utilization rate of raw materials, during the reaction, the bottom tower oil can be circulated back to step (2) and combined with the hydrotreated heavy oil as the composition of material A for the mesophase growth reaction. In material A, the composition of the hydrotreated heavy oil and the bottom tower oil does not affect the properties of the prepared needle coke, and the present invention does not make special requirements.

[0028] In the present invention, in the preparation method of needle coke, the optional range of the size of the two-dimensional carbon material is relatively wide. A preferred embodiment is demonstrated, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, along the direction of the plane of the two-dimensional carbon material, the equivalent diameter of the sheet size of the two-dimensional carbon material is 20 μm - 100 μm; the number of carbon atom layers of the two-dimensional carbon material is 1 - 30 layers, for example, the number of carbon atom layers is 5, 10, 15, 20 or 25.

[0029] In the present invention, in the preparation method of needle coke, the optional range of the type of the two-dimensional carbon material is relatively wide. A preferred embodiment is demonstrated, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the two-dimensional carbon material is selected from graphene and / or graphite.

[0030] In the present invention, in the preparation method of needle coke, the two-dimensional carbon materials that meet the foregoing technical characteristics can all achieve the purpose of the present invention. The optional range of the size of graphene and / or graphite is relatively wide. The following is a demonstration, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the equivalent diameter of the sheet size of the graphene is 20 μm - 80 μm, and the number of carbon atom layers of the graphene is 1 - 3 layers; the equivalent diameter of the sheet size of the graphite is 40 μm - 80 μm, and the number of carbon atom layers of the graphite is 10 - 30 layers.

[0031] In the present invention, in the preparation method of needle coke, the optional range of the coking raw material is relatively wide. The following is a demonstration, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the coking raw material is selected from one or more of catalytic oil slurry, residue oil, tar, crude oil, fuel oil and asphalt.

[0032] In the present invention, in the method for preparing needle coke, the range of selectable properties of the coking raw material is relatively wide. The following is a demonstration, but it does not limit the scope of the present invention thereby. According to a preferred embodiment of the present invention, the properties of the coking raw material include: the density is 0.90 g / cm 3 -1.15 g / cm 3 ;

[0033] According to a preferred embodiment of the present invention, the properties of the coking raw material include: the viscosity is 120 mm 2 / s - 150 mm 2 / s (50 °C).

[0034] According to a preferred embodiment of the present invention, the properties of the coking raw material include: H / C is 0.9 - 1.6:1.

[0035] According to a preferred embodiment of the present invention, the properties of the coking raw material include: based on the mass of sulfur element, the sulfur content in the coking raw material is 0.6% - 1.5%.

[0036] According to a preferred embodiment of the present invention, the properties of the coking raw material include: based on the mass of metal elements, the metal content in the coking raw material is 10 - 50 μg / g.

[0037] According to a preferred embodiment of the present invention, the properties of the coking raw material include: the ash content is 30 μg / g - 70 μg / g.

[0038] According to a preferred embodiment of the present invention, the properties of the coking raw material include: among the four components of the coking raw material, the content of saturated components is 5 wt% - 25 wt%.

[0039] According to a preferred embodiment of the present invention, the properties of the coking raw material include: among the four components of the coking raw material, the content of aromatic components is 60 wt% - 80 wt%.

[0040] According to a preferred embodiment of the present invention, the properties of the coking raw material include: among the four components of the coking raw material, the content of resin is 3 wt% - 20 wt%.

[0041] According to a preferred embodiment of the present invention, the properties of the coking raw material include: among the four components of the coking raw material, the content of asphaltene is 0.5 wt% - 10 wt%. By adopting the foregoing technical solution, the prepared needle coke has a better optical structure, thermal expansion coefficient and strength, and is suitable for the production of large-diameter, ultra-high power graphite electrodes and graphite electrode joints.

[0042] In the present invention, in the preparation method of needle coke, the coking raw material is hydrogenated and then the light fraction is cut off to obtain hydrogenated heavy oil. The optional range of the properties of the hydrogenated heavy oil is relatively wide. For illustrative purposes only and not limiting the scope of the present invention thereby, according to a preferred embodiment of the present invention, the properties of the hydrogenated heavy oil include: the density is 1.01 g / cm 3 -1.25 g / cm 3 .

[0043] According to a preferred embodiment of the present invention, the properties of the hydrogenated heavy oil include: the viscosity is 140 mm 2 / s - 200 mm 2 / s (50 °C).

[0044] According to a preferred embodiment of the present invention, the properties of the hydrogenated heavy oil include: H / C is 1.0 - 1.6.

[0045] According to a preferred embodiment of the present invention, the properties of the hydrogenated heavy oil include: calculated by the mass of sulfur element, the sulfur content in the hydrogenated heavy oil is 0.1% - 0.3%.

[0046] According to a preferred embodiment of the present invention, the properties of the hydrogenated heavy oil include: calculated by the mass of metal elements, the metal content in the hydrogenated heavy oil is 1 - 30 μg / g.

[0047] According to a preferred embodiment of the present invention, the properties of the hydrogenated heavy oil include: the ash content is 20 μg / g - 60 μg / g.

[0048] According to a preferred embodiment of the present invention, the properties of the hydrogenated heavy oil include: among the four components of the hydrogenated heavy oil, the content of saturates is 10 wt% - 30 wt%.

[0049] According to a preferred embodiment of the present invention, the properties of the hydrogenated heavy oil include: among the four components of the hydrogenated heavy oil, the content of aromatics is 60 wt% - 80 wt%.

[0050] According to a preferred embodiment of the present invention, the properties of the hydrogenated heavy oil include: among the four components of the hydrogenated heavy oil, the content of resins is 5 wt% - 15 wt%.

[0051] According to a preferred embodiment of the present invention, the properties of the hydrogenated heavy oil include: among the four components of the hydrogenated heavy oil, the content of asphaltenes is 0.1 wt% - 5 wt%.

[0052] According to a preferred embodiment of the present invention, the properties of the hydrotreated heavy oil include: the 5% distillation temperature of the hydrotreated heavy oil is 300-350°C. With the foregoing technical solution, the prepared needle coke has a better optical structure, coefficient of thermal expansion and strength, and is suitable for the production of large-diameter, ultra-high power graphite electrodes and graphite electrode joints.

[0053] In the present invention, in the preparation method of needle coke, the optional range of the properties of the hydrotreated light oil is relatively wide. For illustrative purposes only and not to limit the scope of the present invention thereby, according to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: the density is 0.65 g / cm 3 -0.85 g / cm 3 .

[0054] According to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: the viscosity is 10 mm 2 / s - 100 mm 2 / s (50°C).

[0055] According to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: H / C is 0.8 - 1.1.

[0056] According to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: based on the mass of sulfur element, the sulfur content in the hydrotreated heavy oil is 0.1% - 0.29%.

[0057] According to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: based on the mass of metal elements, the metal content in the hydrotreated light oil is 0.1 - 5 μg / g.

[0058] According to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: the ash content is 3 μg / g - 30 μg / g.

[0059] According to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: among the four components of the hydrotreated light oil, the content of saturated components is 55 wt% - 75 wt%.

[0060] According to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: among the four components of the hydrotreated light oil, the content of aromatic components is 15 wt% - 35 wt%.

[0061] According to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: among the four components of the hydrotreated light oil, the content of gum is 0.5 wt% - 5 wt%.

[0062] According to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: among the four components of the hydrotreated light oil, the content of asphaltene is 0.05 wt% - 0.5 wt%.

[0063] According to a preferred embodiment of the present invention, the properties of the hydrotreated light oil include: the 95% distillation temperature of the hydrotreated light oil is 310 - 360 °C. By adopting the foregoing technical solution, the prepared needle coke has a better optical structure, coefficient of thermal expansion and strength, and is suitable for the production of large-diameter, ultra-high power graphite electrodes and graphite electrode joints.

[0064] In the present invention, in the preparation method of needle coke, the optional range of the conditions of the coking-drawing and coking reaction in step (3) is relatively wide. The following is a demonstration, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the conditions of the coking-drawing and coking reaction in step (3) include: the temperature is 460 °C - 520 °C.

[0065] According to a preferred embodiment of the present invention, the conditions of the coking-drawing and coking reaction in step (3) include: the pressure is 0.2 MPa - 1 MPa.

[0066] According to a preferred embodiment of the present invention, the conditions of the coking-drawing and coking reaction in step (3) include: the time is 24 h - 36 h.

[0067] According to a preferred embodiment of the present invention, the conditions of the coking-drawing and coking reaction in step (3) include: the coking gas velocity of the composite coking medium is 0.01 - 0.2 m / s.

[0068] According to a preferred embodiment of the present invention, the conditions of the coking-drawing and coking reaction in step (3) include: the weight ratio of the coking medium to the material A is 1 - 3:1. By adopting the foregoing technical solution, the prepared needle coke has a better optical structure, coefficient of thermal expansion and strength, and is suitable for the production of large-diameter, ultra-high power graphite electrodes and graphite electrode joints.

[0069] In the present invention, in the preparation method of needle coke, the optional range of the conditions of the mesophase growth reaction in step (2) is relatively wide. The following is a demonstration, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the conditions of the mesophase growth reaction in step (2) include: the temperature is 370 °C - 470 °C.

[0070] According to a preferred embodiment of the present invention, the conditions of the mesophase growth reaction in step (2) include: the pressure is 0.2 MPa - 1 MPa.

[0071] According to a preferred embodiment of the present invention, the conditions for the mesophase growth reaction in step (2) include: the time is 24 h - 36 h. By adopting the foregoing technical solution, the prepared needle coke has better optical structure, thermal expansion coefficient and strength, and is suitable for the production of large-diameter, ultra-high power graphite electrodes and graphite electrode joints.

[0072] In the present invention, in the preparation method of needle coke, the optional range of the conditions for hydrogenation in step (1) is relatively wide. For illustrative purposes only, but not to limit the scope of the present invention thereby. According to a preferred embodiment of the present invention, the conditions for hydrogenation in step (1) include: the hydrogen pressure is 1.5 MPa - 7 MPa.

[0073] According to a preferred embodiment of the present invention, the conditions for hydrogenation in step (1) include: the temperature is 330 °C - 400 °C.

[0074] According to a preferred embodiment of the present invention, the conditions for hydrogenation in step (1) include: the volume space velocity is 0.5 h -1 -1 h -1 。

[0075] According to a preferred embodiment of the present invention, the conditions for hydrogenation in step (1) include: the volume ratio of hydrogen to coking raw material is 500 - 1500:1.

[0076] In the present invention, in the preparation method of needle coke, the optional range of the conditions for separation in step (1) is relatively wide. For illustrative purposes only, but not to limit the scope of the present invention thereby. According to a preferred embodiment of the present invention, the conditions for separation in step (1) include: the fractionating tower operates at atmospheric pressure, the bottom temperature of the tower is 320 - 360 °C, and the top temperature is 120 - 200 °C. By adopting the foregoing technical solution, the prepared needle coke has better optical structure, thermal expansion coefficient and strength, and is suitable for the production of large-diameter, ultra-high power graphite electrodes and graphite electrode joints.

[0077] In the preparation method of the present invention, hydrogenation of the coking raw material enables inferior high-sulfur slurry to be used for the production of needle coke, expanding the raw material source. After hydrogenation, the sulfur and metal contents are reduced, which is beneficial to the homogeneous nucleation reaction. At the same time, after hydrogenation, the H / C of the material increases and the system viscosity decreases, ensuring the full development of the mesophase. Moreover, hydrogenated light oil is used for pulling coke, and the pulling coke medium also includes a reinforcing agent, which can ensure a significant improvement in the pulling coke effect while reducing the system viscosity, being beneficial to the improvement of the needle coke strength, the reduction of the thermal expansion coefficient and the shaping of the fiber structure. Hydrogenation of the raw material improves the homogeneity and stability of the raw material, which is beneficial to the product homogeneity. At the same time, it improves the operation stability of the device, is beneficial to the overall stable operation of the device, and prolongs the production cycle.

[0078] In the present invention, in the preparation method of needle coke, there are no special requirements for the devices used. For example, a two-furnace and three-column device can be used. The production flow chart of the coking reaction device with two furnaces and three columns as shown in Figure 1 is used to exemplarily illustrate the advantages of the present invention.

[0079] Figure 1 A device for preparing needle coke as shown. The device includes: a hydrogenation unit, and the hydrogenation unit includes: at least one hydrogenation reactor and a reaction product separation device, which are used to hydrogenate the coking raw material and then separate it to obtain hydrogenated light oil and hydrogenated heavy oil;

[0080] A coking unit, and the coking unit includes: 3 parallel coke drums, which are used to carry out mesophase growth reaction on the combined oil containing the hydrogenated heavy oil to obtain mesophase spheres and coking reaction separation oil; and in the presence of a composite coke-drawing medium containing coker gas oil and hydrogenated light oil, the mesophase spheres carry out coke-drawing and coking reactions; when the inlet of the coke drum is connected to the outlet of the raw material heating furnace, the mesophase growth reaction is carried out; when the inlet of the coke drum is connected to the outlet of the coke-drawing medium heating furnace, the coke-drawing and coking reactions are carried out; the outlet of the coke drum is connected to the inlet 1 of the fractionating tower; the 3 coke drums alternately carry out mesophase growth reaction, coke-drawing and coking reactions, and coke cleaning treatment periodically, which is a known technology in the art and will not be described in detail here;

[0081] At least one fractionating tower, and the fractionating tower is used to fractionate the coking reaction separation oil to obtain coking gas, coker naphtha, coker diesel, coker gas oil and bottom combined oil. The inlet 1 of the fractionating tower is used to receive the coking reaction separation oil from the coke drum, and the inlet 2 of the fractionating tower is used to receive the hydrogenated heavy oil from the hydrogenation unit. The hydrogenated heavy oil and / or the bottom combined oil obtained by fractionation flow out from the outlet of the fractionating tower, and after being heated by the raw material heating furnace, enter the coke drum;

[0082] At least 1 raw material heating furnace, the inlet of the raw material heating furnace is connected to the outlet of the fractionating tower, and the outlet of the raw material heating furnace is connected to the inlet of the coke drum;

[0083] At least 1 coke-drawing medium heating furnace, the inlet of the coke-drawing medium heating furnace is connected to the outlet of the coke-drawing oil tank, and the outlet of the coke-drawing medium heating furnace is connected to the inlet of the coke drum;

[0084] At least 1 coke-drawing oil tank: The coke-drawing oil tank is used to mix the coker gas oil and the hydrogenated light oil to obtain a composite coke-drawing medium. The inlet of the coke-drawing oil tank is used to receive the hydrogenated light oil from the hydrogenation unit and the coker gas oil from the fractionating tower. The coke-drawing oil tank can also be provided with an inlet for receiving other components, such as reinforcing agents, etc.

[0085] Specifically, the coking unit includes three coke drums, two sets of heating furnaces, a fractionating tower, and a coke pulling oil tank. The three coke drums are respectively denoted as Coke Drum A, Coke Drum B, and Coke Drum C; the two sets of heating furnaces are respectively denoted as Furnace a and Furnace b. Any coke drum is connected to the two sets of heating furnaces. The top of any coke drum is connected to the lower inlet of the fractionating tower through a pipeline. The lower part of the fractionating tower is also provided with an inlet (for receiving hydrogenated heavy oil); the bottom outlet of the fractionating tower is connected to Furnace a to heat the coking raw material to the feed temperature of the coke drum. The fractionating tower is provided with a side line for the extraction of fractionated oil, and the wax oil fraction enters the coke pulling oil tank d. The outlet of the coke pulling oil tank d is connected to the inlet of Furnace b through a pipeline, and the pulled tar is heated to the coke pulling feed temperature of the coke drum by Furnace b. Furnace a and Furnace b are respectively connected to Coke Drum A, Coke Drum B, and Coke Drum C through four-way valves. When the coke drum is connected to Furnace a, it is in the mesophase stage; when the coke drum is connected to Furnace b, it is in the coke pulling stage; when the coke drum is disconnected from Furnaces a and b, it is in the decoking stage.

[0086] Coke Drums A, B, and C periodically and alternately carry out mesophase reaction, coke pulling reaction, and decoking treatment:

[0087] (1) After the mesophase reaction in Coke Drum A reaches the preset time, terminate its combined oil feed; then simultaneously start the coke pulling medium feed of Coke Drum A and the combined oil feed of Coke Drum B. During the feeding, Coke Drum A immediately undergoes the coke pulling reaction, and Coke Drum B immediately undergoes the mesophase reaction;

[0088] (2) After the mesophase reaction in Coke Drum B reaches the preset time, terminate the coke pulling medium feed of Coke Drum A and the combined oil feed of Coke Drum B; then simultaneously start the coke pulling medium feed of Coke Drum B and the combined oil feed of Coke Drum C. During the feeding, Coke Drum B immediately undergoes the coke pulling reaction, and Coke Drum C immediately undergoes the mesophase reaction;

[0089] (3) Carry out decoking treatment on Coke Drum A to obtain needle coke products;

[0090] (4) After the mesophase reaction in Coke Drum C reaches the preset time, terminate the coke pulling medium feed of Coke Drum B and the combined oil feed of Coke Drum C; then simultaneously start the coke pulling medium feed of Coke Drum C and the combined oil feed of Coke Drum A. During the feeding, Coke Drum C immediately undergoes the coke pulling reaction, and Coke Drum A immediately undergoes the mesophase reaction;

[0091] (5) Carry out decoking treatment on Coke Drum B to obtain needle coke products;

[0092] (6) After the mesophase reaction in Coke Drum A reaches the preset time again, terminate the combined oil feed of Coke Drum A and the coke pulling medium feed of Coke Drum C; then simultaneously start the coke pulling medium feed of Coke Drum A and the combined oil feed of Coke Drum B;

[0093] (7)Perform decoking treatment on the coke drum C to obtain needle coke products;

[0094] (8)Repeat steps (2)-(7) to continuously obtain needle coke products.

[0095] In the present invention, a coking production cycle includes hydrogenation, mesophase growth reaction, pulling coke - coking reaction, and decoking treatment. According to a preferred embodiment of the present invention, the time of a coking production cycle is 48h - 96h.

[0096] The coking reaction device with two furnaces and three towers described above has the following advantages:

[0097] First: The severity of the heating furnace is reduced and it is beneficial for long - term operation

[0098] Under the traditional process of "one furnace and two towers", during the production operation of needle coke, frequent temperature change operations are required, and the temperature change in the heating furnace needs to be strictly controlled. Especially at the end of the coking period, the outlet temperature of the heating furnace is high, which may cause coking in the radiant furnace tubes. In the present invention, two independent heating furnaces for mesophase and pulling coke are respectively set, the temperature conditions of the heating furnace are milder, and the temperature change of the heating furnace is smaller.

[0099] Second: The stability of the fractionating tower is improved and the operation difficulty is reduced

[0100] Under the traditional process of "one furnace and two towers", the raw materials and temperature entering the fractionating tower change greatly, and the material composition and calorific value of each fraction will also change to a certain extent. During the actual operation of the fractionating tower, the temperature fluctuates greatly, and the gas and liquid loads in the fractionating tower fluctuate frequently. In this process, independent raw material heating furnace and pulling coke furnace are adopted, the material and heat fluctuations of the coke drum are small, the fractionating tower has a stable feed, and the production is controllable.

[0101] Third, the heat regulation and intensity improvement effects are remarkable

[0102] In the present invention, in the traditional needle coke process of one furnace and two towers, the quality of the coke formed from the feed at the end stage is poor, so the feed rate is controlled to be a little less. In the present invention, a separate pulling coke heating furnace is used to provide heat for the coke drum, the temperature and time are controllable, which is beneficial to the control of the strength of needle coke, and the pulling tar can be recycled, truly achieving low - cost and zero pollution.

[0103] The present invention provides the needle coke prepared by the method described in the present invention.

[0104] The present invention provides the application of the needle coke described in the present invention in the production of graphite electrodes and graphite electrode joints.

[0105] The needle coke of the present invention has better optical structure, thermal expansion coefficient and strength, and is suitable for the production of large - diameter, ultra - high - power graphite electrodes and graphite electrode joints.

[0106] The present invention will be described in detail below with reference to embodiments.

[0107] In the following examples and comparative examples,

[0108] Testing methods for the properties of coking feedstock, hydrotreated heavy oil, and hydrotreated light oil:

[0109] The density was measured by the method of GB / T 1884-2000;

[0110] The viscosity was measured by the method of GB / T 11137-1989;

[0111] H / C was measured by the method of SH / T 0656-2017;

[0112] The sulfur content was measured by the method of GB / T17040-2008;

[0113] The metal content was measured by the method of SN / T1829-2006;

[0114] The ash content was measured by the method of GB / T 508-1985;

[0115] The contents of four components: saturates, aromatics, resins, and asphaltenes were measured by the method of SH / T 0509-2010;

[0116] The testing method for the distillation range (5% distillation temperature, 95% distillation temperature, etc.) of hydrotreated heavy oil, hydrotreated light oil, and coker gas oil was measured by the method of ASTM D1160.

[0117] Evaluation and analysis methods:

[0118] The obtained needle coke was green coke, and the green coke was calcined at 1350 °C for 5 h to obtain calcined coke. Strength testing and microscopic structure content testing were carried out. After the calcined coke was made into a test body electrode and graphitized, the thermal expansion property (CTE) was tested:

[0119] The strength test was carried out in accordance with T / ZGS002-2019;

[0120] The CTE test was carried out in accordance with GB3074.4-2016;

[0121] Microscopic structure: The contents of mosaic structure, small piece structure, large piece structure, fine fiber structure, and coarse fiber structure were measured by the method of LEICA DM4P optical polarized light microscope;

[0122] The coking feedstock was filtered catalytic slurry, and Table 1 lists the main properties of the filtered slurry used in Example 1.

[0123] Table 1

[0124]

[0125]

[0126] Reinforcing agent I is graphene: It is prepared by exfoliating graphite. The number of carbon atom layers of graphene is 60% with 1 layer and 40% with 2 layers. The equivalent diameter of the sheet size of graphene is 50 ± 20 μm;

[0127] Reinforcing agent II is graphite: Graphite with 30% of the number of carbon atom layers being 10 - 12 layers and 70% being 24 - 26 layers, and the equivalent diameter of the sheet size being 60 ± 10 μm is obtained by exfoliation.

[0128] In the following examples and comparative examples:

[0129] Figure 1 It is the production flow chart of Example 1 of the present invention. The material at the inlet of the heating furnace (a) is called combined oil, and the material at the inlet of the heating furnace (b) is called pulled tar oil.

[0130] The filtered slurry enters the separation device after hydrodesulfurization: Among them, the conditions for hydrogenation include: hydrogen pressure is 6 MPa, temperature is 380 °C, volume space velocity is 0.8 h -1 , and the volume ratio of hydrogen to coking raw material is 1000:1; the separation conditions include: the fractionating tower operates at atmospheric pressure, the bottom temperature of the tower is 340 °C, and the top temperature is 130 °C.

[0131] In Example 1, the 5% distillation temperature of coker gas oil is 300 °C, and the 95% distillation temperature of coker gas oil is 410 °C. The 5% distillation temperature and 95% distillation temperature of coker gas oil in the remaining examples and comparative examples are similar to those in Example 1.

[0132] Example 1

[0133] Using the filtered catalytic slurry as raw material, the properties are shown in Table 1. After hydrodesulfurization, the filtered slurry enters the separation unit. The hydrotreated heavy oil enters the fractionating tower, exchanges heat, and then enters the coking tower (A). The combined bottom oil is withdrawn from the bottom of the fractionating tower, heated by the heating furnace (a), and then enters the coking tower (A). The outlet temperature of the heating furnace (a) is controlled at a constant temperature, and the furnace outlet temperature is 400 - 460 °C. The top pressure of the coking tower is 0.2 - 0.7 MPa. The generated oil and gas enter the fractionating tower through the coking large oil gas pipeline. The bottom temperature of the fractionating tower is 300 - 360 °C, and the pressure of the fractionating tower is 0.1 MPa. Coking gas, coker naphtha, coker diesel, coker wax oil, and combined bottom oil are separated. The coker wax oil and hydrotreated light oil are mixed in the coke pulling tank (d), and the weight ratio of coker wax oil to hydrotreated light oil is 1:1. When the heating furnace (a) feeds the coking tower (A) for 24 hours, the top pressure of the coking tower (A) remains unchanged. Then, the heating furnace (a) is switched to feed the coking tower (B) for the same time. Meanwhile, the pulled tar in the coke pulling tank (d) is heated by the heating furnace (b) and fed to the coking tower (A). The feeding time of the heating furnace (b) to the coking tower (A) is 24 hours, and the outlet temperature of the heating furnace (b) is 460 - 510 °C. At this time, the coking tower (A) is pulling coke. The mass ratio of pulled tar to combined oil is 1.5:1. Reinforcing agent I is added to the pulled tar, and the weight ratio of reinforcing agent I to pulled tar is 1:100. The coke pulling gas velocity is 0.05 m - 0.2 / s. After the heating furnace (a) finishes feeding the coking tower (B), the heating furnace (a) is switched to feed the coking tower (C). Meanwhile, the heating furnace (b) pulls coke from the coking tower (B), and the coking tower (A) undergoes decoking treatment including small blowing, large blowing, water injection, and coke removal. The decoking treatment time is 24 hours. Each coking tower repeats the operation process of the coking tower (A) to obtain the needle coke product. The properties are shown in Table 2, and the microscopic structure is shown in Table 3.

[0134] Example 2

[0135] According to the method of Example 1, needle coke is produced using the filtered catalytic slurry as raw material. The difference is that the weight ratio of coker wax oil to hydrotreated light oil is 3:1, the weight ratio of pulled tar to combined oil is 1.5:1, reinforcing agent I is added to the pulled tar, and the weight ratio of reinforcing agent I to pulled tar is 1:1000. The obtained needle coke product has properties shown in Table 2 and a microscopic structure shown in Table 3.

[0136] Example 3

[0137] According to the method of Example 1, needle coke is produced using the filtered catalytic slurry as raw material. The difference is that the weight ratio of coker wax oil to hydrotreated light oil is 5:1, the weight ratio of pulled tar to combined oil is 1.5:1, reinforcing agent I is added to the pulled tar, and the weight ratio of reinforcing agent I to pulled tar is 1:30000. The obtained needle coke product has properties shown in Table 2 and a microscopic structure shown in Table 3.

[0138] Example 4

[0139] Using the filtered catalytic slurry oil as raw material, needle coke was produced according to the method of Example 1, except that the weight ratio of coker wax oil to hydrotreated light oil was 3:1, the weight ratio of pulled tar to combined oil was 1:1, reinforcing agent II was added to the pulled tar, and the weight ratio of reinforcing agent II to pulled tar was 1:100. The properties of the obtained needle coke product are shown in Table 2, and the microstructures are shown in Table 3.

[0140] Example 5

[0141] Using the filtered catalytic slurry oil as raw material, needle coke was produced according to the method of Example 1, except that the weight ratio of coker wax oil to hydrotreated light oil was 3:1, the weight ratio of pulled tar to combined oil was 1:1, reinforcing agent II was added to the pulled tar, and the weight ratio of reinforcing agent II to pulled tar was 1:1000. The properties of the obtained needle coke product are shown in Table 2, and the microstructures are shown in Table 3.

[0142] Example 6

[0143] Using the filtered catalytic slurry oil as raw material, needle coke was produced according to the method of Example 1, except that the weight ratio of coker wax oil to hydrotreated light oil was 3:1, the weight ratio of pulled tar to combined oil was 1:1, reinforcing agent II was added to the pulled tar, and the weight ratio of reinforcing agent II to pulled tar was 1:30000. The properties of the obtained needle coke product are shown in Table 2, and the microstructures are shown in Table 3.

[0144] Comparative Example 1

[0145] Same as Example 1, the raw material passed through the hydrogenation-separation unit, but only coker wax oil was used as the pulled tar, and no reinforcing agent was added. The properties of the obtained needle coke product are shown in Table 2, and the microstructures are shown in Table 3.

[0146] Comparative Example 2

[0147] Using the filtered catalytic slurry oil as raw material, needle coke was produced according to the method of Example 1, except that the weight ratio of coker wax oil to hydrotreated light oil was 3:1, the mass ratio of pulled tar to combined oil was 1:1, and no reinforcing agent was added. The properties of the obtained needle coke product are shown in Table 2, and the microstructures are shown in Table 3.

[0148] Comparative Example 3

[0149] Using the filtered catalytic slurry oil as raw material, needle coke was produced according to the method of Example 1, except that the weight ratio of coker wax oil to hydrotreated light oil was 3:1, the weight ratio of pulled tar to combined oil was 1.5:1, and no reinforcing agent was added. The properties of the obtained needle coke product are shown in Table 2, and the microstructures are shown in Table 3.

[0150] Table 2

[0151] Product properties <![CDATA[CTE, 10 -6 / ℃]]> Particle strength, % Example 1 0.9 29.4 Example 2 0.9 29.8 Example 3 1 27.7 Example 4 1 27.5 Example 5 1 26 Example 6 1 25.6 Comparative example 1 1.3 21.6 Comparative example 2 1.2 23.5 Comparative example 3 1.1 24.5

[0152] Table 3

[0153]

[0154]

[0155] It can be seen from the results of Table 2 and Table 3 that the needle coke products obtained by using the embodiments of the present invention have a rich fiber structure, high strength and low coefficient of thermal expansion, and obviously have better effects.

[0156] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A needle coke, characterized in that the strength of the needle coke is 25%-34%; The coefficient of thermal expansion of needle coke is 0.8×10 -6 / °C - 1.2×10 -6 / °C; In the microscopic structure of the needle coke: the content of the mosaic structure is 0.1%-10%; the content of the small flake structure is 10%-30%; the content of the large flake structure is 15%-40%; the content of the fine fiber structure is 10%-45%; the content of the coarse fiber structure is 10%-45%.

2. The needle coke according to claim 1, characterized in that in the microscopic structure of the needle coke: the content of the fiber structure is 20%-90%.

3. A method for preparing needle coke, characterized in that, The method includes: (1) Hydrogenating and separating the coking raw material to obtain hydrogenated light oil and hydrogenated heavy oil; (2) Performing a mesophase growth reaction on the material A containing the hydrogenated heavy oil to obtain mesophase spheres and coking reaction separated oil; (3) Performing a coking-forming reaction on the mesophase spheres in the presence of a coking medium containing the hydrogenated light oil; The coking medium further includes a reinforcing agent, and the reinforcing agent includes a two-dimensional carbon material; in the coking medium, the content of the reinforcing agent is 0.003-1 wt%.

4. The method according to claim 3, wherein The method further includes: fractionating the coking reaction separated oil to obtain coking gas, coking naphtha, coking diesel, coking wax oil, and bottom tower oil, the 5% distillation temperature of the coking wax oil is 260-350°C, and the 95% distillation temperature of the coking wax oil is 370-440°C.

5. The method according to claim 4, characterized in that, The method further includes: recycling the coking wax oil back to step (3) and combining it with the hydrogenated light oil as the coking medium, and the weight ratio of the coking wax oil to the hydrogenated light oil is 1-5:1; and / or recycling the bottom tower oil back to step (2) and combining it with the hydrogenated heavy oil as a component of the material A to perform the mesophase growth reaction.

6. The method according to claim 3, characterized in that along the direction of the plane of the two-dimensional carbon material, the equivalent diameter of the sheet size of the two-dimensional carbon material is 20 μm-100 μm; the number of carbon atom layers of the two-dimensional carbon material is 1-30 layers.

7. The method according to claim 6, characterized in that the two-dimensional carbon material is selected from graphene and / or graphite; the equivalent diameter of the sheet size of the graphene is 20 μm-80 μm, and the number of carbon atom layers of the graphene is 1-3 layers; the equivalent diameter of the sheet size of the graphite is 40 μm-80 μm, and the number of carbon atom layers of the graphite is 10-30 layers.

8. The method according to claim 3, characterized in that the coking raw material is selected from one or more of catalytic oil slurry, residue oil, tar, crude oil, fuel oil, and asphalt; The properties of the coking raw material include: The density is 0.90 g / cm 3 -1.15 g / cm 3 ; The viscosity is 120 mm 2 / s - 150 mm 2 / s; H / C is 0.9-1.6:1; calculated by the mass of sulfur element, the sulfur content in the coking raw material is 0.6%-1.5%; calculated by the mass of metal element, the metal content in the coking raw material is 10-50 μg / g; the ash content is 30 μg / g-70 μg / g; and / or in the four components of the coking raw material, the content of the saturates is 5 wt%-25 wt%, the content of the aromatics is 60 wt%-80 wt%, the content of the resins is 3 wt%-20 wt%, and the content of the asphaltenes is 0.5 wt%-10 wt%.

9. The method according to claim 3, characterized in that the properties of the hydrogenated heavy oil include: Density is 1.00 g / cm 3 -1.25 g / cm 3 ; The viscosity is 140 mm 2 / s - 200 mm 2 / s; H / C is 1.0 - 1.6; based on the mass of sulfur element, the sulfur content in the hydrogenated heavy oil is 0.1% - 0.3%; based on the mass of metal elements, the metal content in the hydrogenated heavy oil is 1 - 30 μg / g; the ash content is 20 μg / g - 60 μg / g; and / or among the four components of the hydrogenated heavy oil, the content of saturates is 10 wt% - 30 wt%, the content of aromatics is 60 wt% - 80 wt%, the content of resins is 5 wt% - 15 wt%, and the content of asphaltenes is 0.1 wt% - 5 wt%; and / or the 5% distillation temperature of the hydrogenated heavy oil is 300 - 350 °C.

10. The method according to claim 3, characterized in that the properties of the hydrogenated light oil include: The density is 0.65 g / cm 3 - 0.85 g / cm 3 ; The viscosity is 10 mm 2 / s - 100 mm 2 / s; H / C is 0.8 - 1.1; based on the mass of sulfur element, the sulfur content in the hydrogenated light oil is 0.1% - 0.29%; based on the mass of metal elements, the metal content in the hydrogenated light oil is 0.1 - 5 μg / g; the ash content is 3 μg / g - 30 μg / g; and / or among the four components of the hydrogenated light oil, the content of saturates is 55 wt% - 75 wt%, the content of aromatics is 15 wt% - 35 wt%, the content of resins is 0.5 wt% - 5 wt%, and the content of asphaltenes is 0.05 wt% - 0.5 wt%; and / or the 95% distillation temperature of the hydrogenated light oil is 310 - 360 °C.

11. The method according to claim 3, characterized in that the conditions of the coke pulling - coking reaction in step (3) include: the temperature is 460 °C - 520 °C; the pressure is 0.2 MPa - 1 MPa; the time is 24 h - 36 h; the coke pulling gas velocity of the coke pulling medium is 0.01 - 0.2 m / s; the weight ratio of the coke pulling medium to the material A is 1 - 3:

1.

12. The method according to claim 3, characterized in that the conditions of the mesophase growth reaction in step (2) include: the temperature is 370 °C - 470 °C; the pressure is 0.2 MPa - 1 MPa; the time is 24 h - 36 h.

13. The method according to claim 3, characterized in that the conditions of the hydrogenation in step (1) include: the hydrogen pressure is 1.5 MPa - 7 MPa; the temperature is 330 °C - 400 °C; The space velocity is 0.5 h -1 -1 h -1 ; the volume ratio of hydrogen to the coking raw material is 500 - 1500:1; the conditions of the separation in step (1) include: atmospheric pressure, the bottom temperature of the tower is 320 - 360 °C, and the top temperature of the tower is 120 - 200 °C.

14. The method according to claim 3, characterized in that, The device for preparing needle coke is a two - furnace and three - tower device.

15. Needle coke prepared by the method according to any one of claims 3 - 14.

16. The application of the needle coke according to claim 1, 2 or 15 in the production of graphite electrodes and graphite electrode joints.

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