Oil-based isotropic coke and isotropic graphite material and preparation method thereof

Abstract

The invention provides an oil-based isotropic coke and isotropic graphite material and a preparation method thereof. The preparation method of the oil isotropic coke comprises the steps of raw material preparation, impurity removal, raw material blending, raw material modification, pyrolysis and the like. The preparation method of the isotropic graphite material comprises the following steps: mixing and kneading oil-based isotropic coke and a binder, crushing, preparing a blank, roasting for the first time, impregnating with asphalt, roasting for the second time, and graphitizing to obtain the isotropic graphite material. The oil-based isotropic coke and isotropic graphite material disclosed by the invention are prepared by the method disclosed by the invention. The isotropic degree, the strength, the purity, the high-temperature shrinkage performance and the like of the isotropic coke are improved, and the isotropic graphite material with excellent strength, electrical conductivity, thermal conductivity, volume density, isotropy, uniformity and the like is obtained.

Description

Technical Field

[0001] The invention relates to oil-based isotropic coke and isotropic graphite material and a preparation method thereof, belonging to the technical field of isotropic graphite materials. Background Art

[0002] Isotropic coke is a high-quality raw material for producing isotropic graphite. It can be processed into graphite electrodes for electrospark machining, mechanical seals under high temperature and high pressure, graphite crucibles and heating elements for single and polycrystalline silicon, nuclear graphite, an energy absorbing material in the nuclear reaction process, aircraft brake pads that withstand impact, friction and wear, and missile nozzle throat liners, and graphitized cathodes for aluminum.

[0003] In the production and application of isotropic coke, companies such as Dahu, Mitsubishi, New Nichia, and Shanjing have been able to produce a variety of isotropic coke products, and carbon products made from them have been widely used. However, the particle strength, resistivity, impurity content, etc. of the pitch coke products produced by most companies currently cannot meet the quality requirements of isotropic graphite products.

[0004] CN104293366A discloses a method for preparing isotropic coke by catalytic carbonization. The method uses coal tar (or coal pitch) as raw material, and adds a certain proportion of Lewis acid catalyst such as AlCl 3 、FeCl 3 or HF / BF 3 , after uniform mixing, placed in an autoclave, and catalytic carbonization is carried out at a certain temperature and pressure to obtain isotropic coke. In this method, the Lewis acid aluminum and iron used will remain in the reaction product. These metals affect the application of the product in high-end carbon materials in the form of ash. In addition, HF is a highly corrosive acid, which not only has high requirements on the reaction device, but also requires the entire transmission and recovery device to be corrosion-resistant. The equipment investment is large and the safety risks are high.

[0005] CN109735361A discloses a method for preparing high microscopic strength mosaic structure asphalt coke. The method specifically uses heavy asphalt as raw material, undergoes oxidative polymerization, and then undergoes deep polycondensation to prepare high microscopic strength mosaic structure asphalt coke.

[0006] CN1306070A discloses a method for preparing isotropic coke. The method uses coal tar or petroleum residue distillate as raw material, heats it to 120°C, starts stirring and introduces oxygen-containing gas, the gas flow rate is 5L / h-45L / h per 100 grams of raw material, the reaction temperature is 260-430°C, after reaching the reaction temperature, the temperature is kept constant, the reaction time is 5-15 hours, and oxidized coal tar or petroleum residue distillate is obtained; the oxidized coal tar or petroleum residue distillate is coked at a temperature of 460-500°C, a pressure of 0.1-1Mpa, and nitrogen protection to generate isotropic coke. The method converts the distillate into a substance similar to asphalt by condensation and cross-linking chemical reactions after removing a part of the evaporation, and then cokes to obtain isotropic coke. Since coal tar and petroleum residue are components rich in polycyclic aromatic hydrocarbons with high viscosity, the effect of the contact reaction between air and these large molecular polycyclic aromatic hydrocarbons is limited by gas-liquid mass transfer, the actual degree of cross-linking reaction is low, and it is difficult for aromatic rings and side chain alkyls to undergo large-scale free radical reactions. Therefore, the further coking reaction of the obtained asphalt-like substances has a certain amount of streamline structure other than the mosaic structure.

[0007] CN106987262A discloses a method for producing isotropic pitch coke. The method atomizes molten coal tar to obtain atomized pitch; the atomized pitch is contacted with high-temperature gas for pyrolysis to obtain isotropic pitch coke, and the temperature of the high-temperature gas is between 500-1400°C. Since the atomized pitch particles are small and the contact time with the high-temperature gas is short, the particle size and particle strength cannot meet the requirements of the special graphite industry for raw coke.

[0008] CN103849411A discloses a method for preparing isotropic coke. The method obtains isotropic coke by adjusting the content of quinoline insolubles in coal tar raw materials and adjusting the heating rate, reaction temperature and constant temperature time in polymerization reaction and carbonization reaction to control the number and particle size of small spheres. Usually, quinoline insolubles contain a large amount of inorganic impurities, resulting in a high ash content in the product, and the obtained special graphite product has the problems of cracking and high resistivity.

[0009] Most of the above existing technologies use coal tar or coal tar pitch or their blending products as raw materials to produce asphalt coke. Although a certain proportion of mosaic structure exists in the structure, the use of either additives or catalysts will eventually lead to a high impurity content in the product coke, limiting its scope of use.

[0010] Isotropic coke needs to solidify quickly when aromatics form mesophase globules before coking to ensure that they are not absorbed and grown by the surrounding isotropic asphalt aromatic molecules, nor are they fused with the surrounding mesophase globules, and are not deformed by the light component airflow generated by the pyrolysis reaction, but keep the mosaic structure small and uniform. At the same time, the size, distribution and concentration of the small spheres formed at the beginning need to be considered. If the concentration of the small spheres is low at the initial stage of formation, and the proportion of isotropic asphalt is large, the subsequent coking process of isotropic asphalt will easily form large pieces or streamlined structures. If the size of the small spheres is uneven, the mosaic structure in the subsequent coke will also be unevenly distributed.

[0011] CN116444274A discloses a method for preparing an ultrafine structured isotropic graphite material. The raw materials used in the method include 5-15% raw petroleum coke, 5-10% semi-petroleum coke, 5-10% mesophase carbon microspheres, 50-60% petroleum coke, and 10-25% asphalt coke; the above raw materials are crushed to less than 5 μm to obtain a raw material mixture, graphene oxide is added to the asphalt organic solution to form a uniform slurry, and then the raw material mixture is mixed with the slurry and heated, dried, crushed, sieved, formed, roasted, impregnated and graphitized to obtain an isotropic graphite material. The method does not solve the problems existing in the prior art from the perspective of the structural uniformity of petroleum coke, and there are many types of raw coke, and it is difficult to ensure the consistency of the ratio and the uniformity of mixing in actual operation, and batch instability is prone to occur. In addition, the surface properties of coke and its fusion with asphalt are adjusted by adding graphene oxide. Since the nanometer size of graphene is difficult to be uniformly dispersed in the asphalt viscous liquid, it is easy to have the problem of local inhomogeneity of the product. Summary of the invention

[0012] In order to solve the above technical problems, the purpose of the present invention is to provide an oil-based isotropic coke and isotropic graphite material and a preparation method thereof. The oil-based isotropic coke and isotropic graphite material provided by the present invention have excellent comprehensive properties.

[0013] In order to achieve the above object, the first aspect of the present invention provides a method for preparing oil-based isotropic coke, which comprises the following steps:

[0014] S1. Raw material preparation:

[0015] The petroleum crude oil, ethylene tar and biomass tar are subjected to atmospheric distillation and vacuum distillation respectively to obtain at least 370-400°C and above 450°C petroleum crude oil fractions, 350°C and above ethylene tar fractions, and 270-300°C and above 350°C biomass tar fractions;

[0016] S2. Impurity removal and raw material preparation:

[0017] S201, mixing petroleum crude oil distillate above 450° C. and petroleum crude oil distillate at 370-400° C., and then removing impurities to obtain a purified crude oil component;

[0018] S202, removing impurities from ethylene tar fraction oil above 350° C. to obtain purified ethylene tar pitch;

[0019] S203, mixing the purified crude oil component and the purified ethylene tar asphalt to obtain a primary mixed oil;

[0020] S204, mixing the biomass tar fraction oil above 350° C. and the biomass tar fraction oil at 270-300° C., and then removing impurities to obtain purified biomass tar pitch;

[0021] S3. Raw material modification:

[0022] S301, mixing a stabilizer and the purified biomass tar pitch to obtain a purified biomass tar pitch containing a stabilizer;

[0023] S302, mixing the primary mixed oil and the purified biomass tar pitch containing a stabilizer to obtain a modified raw material;

[0024] S4, Pyrolysis:

[0025] The modified raw material is pyrolyzed to obtain green coke, which is the oil-based isotropic coke.

[0026] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S1, the petroleum crude oil includes naphthenic crude oil and / or intermediate-naphthenic crude oil. Intermediate crude oil and paraffinic crude oil are not suitable for the present invention because the residual aromatic side chains obtained from intermediate crude oil and paraffinic crude oil are relatively long, and the molecular structure and reaction activity of ethylene tar and biomass tar are greatly different, and the coking process is difficult to control.

[0027] In the above-mentioned method for preparing oil-based isotropic coke, in step S1, it should be noted that the ethylene tar is a by-product obtained by steam cracking of cracked raw materials in the ethylene production process, and the cracked raw materials include a mixture of several of naphtha, ethane, propane, diesel, etc. The biomass tar may include one or a mixture of several of primary biomass tar, secondary biomass tar and tertiary biomass tar.

[0028] In the above-mentioned method for preparing oil-based isotropic coke, preferably, step S1 specifically comprises:

[0029] After removing the light fraction below 370°C by normal pressure distillation of the crude oil, vacuum distillation is performed under the condition of 5-10Kpa to obtain three kinds of crude oil distillates at 370-400°C, 400-450°C and above 450°C;

[0030] After the ethylene tar and the biomass tar are subjected to normal pressure distillation to cut off the light fraction below 260°C, they are subjected to reduced pressure distillation under the condition of 10-15Kpa to obtain three kinds of ethylene tar fraction oils at 270-300°C, 300-350°C and above 350°C, and three kinds of biomass tar fraction oils at 270-300°C, 300-350°C and above 350°C, respectively.

[0031] In the above-mentioned method for preparing oil-based isotropic coke, preferably, step S201 specifically comprises: mixing petroleum crude oil distillate above 450°C and petroleum crude oil distillate at 370-400°C in a weight ratio of 10:3-5, and then removing metal impurities through an electric field separation device to obtain a purified crude oil component.

[0032] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S201, the petroleum crude oil distillate above 450°C and the petroleum crude oil distillate at 370-400°C are mixed by using a pipeline static mixer with a linear speed of 0.3-0.5 m / s.

[0033] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S201, the electric field separation device includes a composite space of an electric field and a flow field containing filler balls, the filler balls include ceramic balls prepared from one or more of barium titanate, lead titanate, lead zirconate titanate and lead magnesium niobate, etc., the diameter of the filler balls is 200-1000 μm, the intensity of the electric field is 3-10KV, the electric field separation device is designed as an uneven electric field, and the power supply mode of the electric field separation device is intermittent power supply. More preferably, step S201 further includes backwashing the electric field separation device, the backwashing oil is the 370-400°C petroleum crude oil distillate obtained in step S1, the ash content in the oil after backwashing is 2-3%, and the contaminated backwashing oil can be returned to the catalytic cracking unit.

[0034] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S201, the ash content of the purified crude oil component is 10-20 ppm.

[0035] In the above-mentioned method for preparing oil-based isotropic coke, preferably, step 202 specifically comprises: filtering ethylene tar fraction oil above 350° C. through a sintered metal mesh to remove impurities, thereby obtaining purified ethylene tar pitch.

[0036] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S202, the absolute filtration accuracy of the sintered metal mesh is 5-10 μm, and the filtration temperature is 330-340°C.

[0037] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S202, the ash content in the purified ethylene tar pitch is 5-10 ppm, the softening point is 80-120°C, the toluene insoluble matter content is 10-15% (weight percentage), and the coking value is 25-35%.

[0038] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step 203, the mixing weight ratio of the purified crude oil component and the purified ethylene tar pitch is 1:2-4.

[0039] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S203, the purified crude oil component and the purified ethylene tar pitch are mixed by using a pipeline static mixer with a linear speed of 0.3-0.5 m / s.

[0040] In the above-mentioned method for preparing oil-based isotropic coke, preferably, step 204 specifically includes: mixing biomass tar fraction oil above 350°C and biomass tar fraction oil at 270-300°C in a weight ratio of 10:1-3, and then removing inorganic impurities by centrifugal filtration to obtain purified biomass tar pitch.

[0041] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S204, the biomass tar fraction oil above 350°C and the biomass tar fraction oil at 270-300°C are mixed by using a pipeline static mixer with a linear velocity of 0.2-0.4 m / s.

[0042] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S204, the rotation speed of the centrifuge used for the centrifugal filtration is 30000-80000 r / min, and the operating temperature is 140-160°C.

[0043] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S204, the ash content in the purified biomass tar pitch is 30-50 ppm.

[0044] In the above-mentioned method for preparing oil-based isotropic coke, preferably, step S301 specifically comprises: mixing the stabilizer and the purified biomass tar pitch at a weight ratio of 0.1-1:100 at 190-200° C. to obtain purified biomass tar pitch containing the stabilizer. The mixing is preferably stirred, and the stirring rate is preferably 50-100 r / min.

[0045] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S301, the stabilizer is prepared by the following process: distilling and rectifying biomass tar to obtain 190-210°C biomass tar fraction oil, reacting the 190-210°C biomass tar fraction oil with isobutylene in the presence of a sulfonic acid resin to obtain the stabilizer. Specifically, the 190-210°C biomass tar fraction oil can be obtained by the following process: distilling biomass tar to obtain fraction oil below 330°C, then rectifying to obtain a light fraction below 210°C, and then further rectifying to remove fraction oil below 190°C to obtain 190-210°C biomass tar fraction oil.

[0046] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S301, the mass ratio of the 190-210°C biomass tar fraction oil to the isobutylene is 1.9-2.1:1.

[0047] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S301, the temperature of the reaction of the 190-210°C biomass tar fraction oil and the isobutylene in the presence of the sulfonic acid resin is 90-100°C and the pressure is 0.1-0.12Mpa. Specifically, the reaction can be carried out in a fixed bed reactor, and the sulfonic acid resin is filled in the fixed bed reactor.

[0048] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S302, the mixing weight ratio of the primary mixed oil and the purified biomass tar pitch containing the stabilizer is 10:2-4.

[0049] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S302, the primary mixed oil and the purified biomass tar pitch containing the stabilizer are mixed by using a pipeline static mixer with a linear velocity of 0.2-0.4 m / s.

[0050] In the above-mentioned method for preparing oil-based isotropic coke, preferably, step S4 specifically comprises:

[0051] The modified raw material is heated in a preheating furnace, and then enters the coking reactor from the bottom of the coking reactor to carry out a first-stage reaction, and the generated oil and gas flows out from the top of the coking reactor and enters a fractionation tower for fractionation; the 320-380°C distillate oil obtained by the fractionation tower is heated alone or mixed with 380-450°C distillate oil, and then enters the coking reactor from the bottom of the coking reactor to carry out a second-stage reaction to obtain a coke precursor, and the generated oil and gas flows out from the top of the coking reactor and enters a fractionation tower for fractionation; then the 320-380°C distillate oil obtained by the fractionation tower is heated again in a heating furnace, and continues to enter the coking reactor from the bottom of the coking reactor to carry out a third-stage reaction, and the generated oil and gas flows out from the top of the coking reactor and enters a fractionation tower for fractionation, and the coke obtained after the reaction is completed is the oil-based isotropic coke.

[0052] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S4, three coking reactors are used to perform the first stage reaction, the second stage reaction and the third stage reaction in an alternating cycle, and the alternating cycle method includes: when the first coking reactor is performing the first stage reaction, the second coking reactor is performing the second stage reaction, and the third coking reactor is performing the third stage reaction; when the first coking reactor finishes the first stage reaction and performs the second stage reaction, the second coking reactor finishes the second stage reaction and performs the third stage reaction, and the third coking reactor finishes the third stage reaction and performs the first stage reaction; when the first coking reactor finishes the second stage reaction and performs the third stage reaction, the second coking reactor finishes the third stage reaction and performs the first stage reaction, and the third coking reactor finishes the first stage reaction and performs the second stage reaction.

[0053] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S4, the outlet temperature of the preheating furnace is 420-440° C. The outlet temperature of the preheating furnace can be kept constant at a temperature in the range of 420-440° C., or can be increased from 420° C. to above 420° C.-440° C. by a suitable heating rate.

[0054] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S4, in the first stage reaction, the bottom feed temperature of the coking reactor is 410-430°C, the pressure in the coking reactor is 0.15-0.5Mpa, and the time of the first stage reaction is 12-24 hours.

[0055] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S4, the pressure of the fractionation tower is 0.12-0.45Mpa, the bottom temperature is 370-390°C, the top temperature is 110-130°C, the non-condensable gas is separated and discharged through the top of the fractionation tower, the water and oil are separated by cooling, the small molecular gas hydrocarbons are collected, and the side line of the fractionation tower obtains distillate oils of 130-200°C, 200-320°C, 320-380°C, 380-450°C and greater than 450°C respectively, the 130-200°C distillate oil is produced and collected through the top circulation, the 200-320°C distillate oil, the 320-380°C distillate oil and the 380-450°C distillate oil are produced and collected, and the distillate oil greater than 450°C is circulated at the bottom of the fractionation tower to provide the heat required for the fractionation tower.

[0056] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S4, the 320-380° C. distillate oil and the 380-450° C. distillate oil are mixed in a weight ratio of 1-10:10.

[0057] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S4, the outlet temperature of the heating furnace is 490-520° C. The outlet temperature of the heating furnace can be kept constant at a temperature in the range of 490-520° C., or can be increased from 490° C. to above 490° C.-520° C. by a suitable heating rate.

[0058] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S4, in the second stage reaction, the bottom feed temperature of the coking reactor is 485-515°C, the pressure in the coking reactor is 0.5-0.8Mpa, and the time of the second stage reaction is 12-24 hours.

[0059] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S4, in the third stage reaction, the bottom feed temperature of the coking reactor is 485-515°C, the pressure in the coking reactor is 0.15-0.5Mpa, and the time of the third stage reaction is 12-24 hours.

[0060] It should be noted that the reaction conditions of the three stages of the first coking reactor, the second coking reactor and the third coking reactor are the same.

[0061] In the above-mentioned method for preparing oil-based isotropic coke, preferably, the mosaic structure ratio of the green coke is 80-90%, the carbon microcrystalline structure size is 1-20 μm, and the true density is 1.385-1.430 g / cm 3, the Hardgrove grindability index is 20-30%; based on the total weight of the green coke, the ash content is 10-50ppm, the volatile content is 5-10%, the sulfur content is 0.2-0.4%, the nitrogen content is 0.1-0.2%, and the water content is 8-12%. It should be noted that the optical structure of the green coke, except for the mosaic structure, is generally a large sheet structure and / or a streamline structure.

[0062] According to a specific embodiment of the present invention, preferably, the method for preparing the oil-based isotropic coke further comprises step S5: calcining the green coke at a high temperature to obtain cooked oil-based isotropic coke.

[0063] In the above-mentioned method for preparing oil-based isotropic coke, preferably, step S5 specifically comprises: drying the green coke to obtain dehydrated green coke, crushing and screening, selecting green coke particles with a particle size of less than 10 mm and green coke particles with a particle size of 10-20 mm, mixing the two, and sending them into a calcining furnace for calcining, and after cooling, obtaining oil-based isotropic coke cooked coke.

[0064] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S5, the water content of the dehydrated green coke is 3-5% (weight percentage).

[0065] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S5, the mixing weight ratio of coke particles with a particle size of less than 10 mm and coke particles with a particle size of 10-20 mm is 1:2-3.

[0066] In the above-mentioned method for preparing oil-based isotropic coke, preferably, in step S5, the inlet temperature of the calcining furnace is 200-300°C, the heating rate is 30-40°C / min, the calcining zone temperature is 1300-1600°C, the residence time of the mixed green coke particles in the calcining furnace is 1-3 hours, and the cooling rate is 40-50°C / min.

[0067] In the above-mentioned preparation method of oil-based isotropic coke, preferably, the ratio of mosaic structure of the oil-based isotropic coke is 85-95%, the size of carbon microcrystalline structure is 5-20 μm, and the true density is 2.052-2.153 g / cm 3 , the Hardgrove grindability index is 20-30%; based on the total weight of the cooked coke, the ash content is 10-50ppm, the volatile matter content is 0.1-0.3%, the sulfur content is 0.1-0.3%, the nitrogen content is 0.05-0.1%, and the water content is less than 0.1%.

[0068] The second aspect of the present invention provides an oil-based isotropic coke, which is prepared by the above-mentioned method for preparing the oil-based isotropic coke.

[0069] According to a specific embodiment of the present invention, preferably, the ratio of the mosaic structure of the oil-based isotropic coke is 80-90%, the size of the carbon microcrystalline structure is 1-20 μm, and the true density is 1.385-1.430 g / cm 3 , the Hardgrove grindability index is 20-30%; based on the total weight of the green coke, the ash content is 10-50ppm, the volatile matter content is 5-10%, the sulfur content is 0.2-0.4%, the nitrogen content is 0.1-0.2%, and the water content is 8-12%.

[0070] According to a specific embodiment of the present invention, preferably, the mosaic structure ratio of the oil-based isotropic coke is 85-95%, the carbon microcrystalline structure size is 5-20 μm, and the true density is 2.052-2.153 g / cm 3 , the Hardgrove grindability index is 20-30%; based on the total weight of the cooked coke, the ash content is 10-50ppm, the volatile matter content is 0.1-0.3%, the sulfur content is 0.1-0.3%, the nitrogen content is 0.05-0.1%, and the water content is less than 0.1%.

[0071] The third aspect of the present invention provides a method for preparing an isotropic graphite material, which comprises the following steps: kneading, crushing, blanking, first calcination, asphalt impregnation, second calcination, and graphitization of the above-mentioned oil-based isotropic coke and binder to obtain the isotropic graphite material.

[0072] In the above-mentioned method for preparing isotropic graphite material, preferably, the mixing ratio of the oil-based isotropic coke and the binder is: the mixing weight ratio of green coke and cooked coke is 1:1-10, and the amount of the binder is 35-45% of the total weight of the green coke and cooked coke.

[0073] In the above-mentioned method for preparing the isotropic graphite material, preferably, the particle size of the green coke and the cooked coke is 3-15 μm.

[0074] In the above-mentioned method for preparing the isotropic graphite material, preferably, the particle size of the binder is 2-3 μm.

[0075] In the above-mentioned preparation method of isotropic graphite material, preferably, the binder is prepared by at least the following steps: molecular distillation of purified ethylene tar pitch, operating pressure of 2-5pa, temperature of 280-300°C, to obtain light components and heavy components, the light components are collected by condensation, and the heavy components are cooled to obtain the binder. Wherein, the purified ethylene tar pitch can be the purified ethylene tar pitch obtained in step S202 of the above-mentioned preparation method of oil-based isotropic coke. The ash content of the purified ethylene tar pitch is 5-10ppm, the softening point is 80-120°C, the toluene insoluble content is 10-15%, and the coking value is 25-35%. Wherein, after cooling, the heavy component can be sliced ​​again, and then enter the air flow mill for pulverization to obtain a binder with a particle size of 2-3μm.

[0076] In the above-mentioned method for preparing isotropic graphite material, preferably, the softening point of the binder is 200-280° C., the content of quinoline insoluble matter is 30-40% (weight percentage), the coking value is 70-75%, and the polarizing structure is isotropic.

[0077] In the above-mentioned method for preparing the isotropic graphite material, preferably, the kneading operation is performed at 230-330°C.

[0078] In the above-mentioned method for preparing the isotropic graphite material, preferably, the particle size of the particles obtained after the crushing is 4-16 μm.

[0079] In the above-mentioned method for preparing isotropic graphite material, preferably, the blank making is to put the crushed particles into a mold and perform isostatic pressing to obtain a green blank. More preferably, the pressure of the isostatic pressing is 180-240 MPa.

[0080] In the above-mentioned method for preparing the isotropic graphite material, preferably, the first calcination process comprises:

[0081] Heating stage: heating from room temperature to 190-210°C at a heating rate of 8-10°C / hr, heating from 190-210°C to 290-310°C at a heating rate of 4-7°C / hr, heating from 290-310°C to 390-410°C at a heating rate of 3-6°C / hr, heating from 390-410 to 590-610°C at a heating rate of 2-4°C / hr, keeping at 590-610°C for 15-24 hours, heating from 590-610°C to 890-910°C at a heating rate of 5-8°C / hr, heating from 890-910°C to 1050-1150°C at a heating rate of 10-15°C / hr, keeping at 1050-1150°C for 8-15 hours;

[0082] Cooling stage: cool down from 1050-1150℃ to 890-910℃ at a cooling rate of 4-7℃ / hr, cool down from 890-910℃ to 590-610℃ at a cooling rate of 8-12℃ / hr, cool down from 590-610℃ to 390-410℃ at a cooling rate of 12-17℃ / hr, cool down from 390-410℃ to 90-110℃ at a cooling rate of 18-22℃ / hr, end the first roasting and obtain the initial carbon blank.

[0083] During the first roasting process, there are processes such as the discharge of volatiles, the coking of the binder, and the volume shrinkage of the green body. The temperature program has a great influence on the physical and chemical properties, porosity, volume density, resistivity, and mechanical strength of the initial carbon green body. The present invention controls the first roasting process so that the initial carbon green body has excellent overall performance.

[0084] In the above-mentioned preparation method of isotropic graphite material, preferably, the pitch impregnation specifically includes: heating the initial carbon blank to 180-200°C, placing it in an impregnation tank and sealing it, evacuating it to a vacuum degree of 5-20Kpa and maintaining it for 2-4 hours, then adding the preheated impregnating agent, completely immersing the carbon blank, passing an inert gas (such as argon) and pressurizing it to 1-2Mpa and maintaining the pressure for 1-3 hours before taking it out. More preferably, the impregnating agent is purified ethylene tar pitch. The purified ethylene tar pitch can be the purified ethylene tar pitch obtained in step S202 of the above-mentioned preparation method of oil-based isotropic coke. The ash content in the purified ethylene tar pitch is 5-10ppm, the softening point is 80-120°C, the toluene insoluble content is 10-15%, and the coking value is 25-35%.

[0085] In the above-mentioned method for preparing the isotropic graphite material, preferably, the second calcination process comprises:

[0086] Heating stage: heating from room temperature to 90-110°C at a heating rate of 8-10°C / hr, heating from 90-110°C to 240-260°C at a heating rate of 4-7°C / hr, heating from 240-260°C to 390-410°C at a heating rate of 3-6°C / hr, heating from 390-410°C to 590-610°C at a heating rate of 2-4°C / hr, keeping at 590-610°C for 20-28 hours, heating from 590-610°C to 890-910°C at a heating rate of 5-8°C / hr, heating from 890-910°C to 1150-1250°C at a heating rate of 10-15°C / hr, keeping at 1150-1250°C for 8-16 hours;

[0087] Cooling stage: cool down from 1150-1250℃ to 890-910℃ at a cooling rate of 4-7℃ / hr, cool down from 890-910℃ to 590-610℃ at a cooling rate of 8-12℃ / hr, cool down from 590-610℃ to 390-410℃ at a cooling rate of 12-17℃ / hr, cool down from 390-410℃ to 90-110℃ at a cooling rate of 18-22℃ / hr, and end the second roasting.

[0088] The properties of the impregnating agent used for asphalt impregnation are significantly different from the binder initially used in the preparation step. Therefore, the present invention adopts a second roasting step and controls the roasting process so that the carbon blank obtained after the second roasting has excellent comprehensive properties.

[0089] In the above-mentioned method for preparing the isotropic graphite material, preferably, the process of the pitch impregnation and the second calcination is repeated 1-3 times.

[0090] In the above-mentioned method for preparing isotropic graphite material, preferably, the temperature of the graphitization treatment is 2800-3000°C, and the holding time is 2-5 hours. More preferably, the graphitization treatment process includes: heating from room temperature to 1150-1250°C at a heating rate of 23-27°C / hr, heating from 1150-1250°C to 1350-1450°C at a heating rate of 21-25°C / hr, heating from 1350-1450°C to 1550-1650°C at a heating rate of 20-24°C / hr, heating from 1550-1650°C to 1700-1800°C at a heating rate of 19-23°C / hr. The temperature is raised from 50-1650℃ to 1950-2050℃, and then from 1950-2050℃ to 2350-2450℃ at a heating rate of 21-25℃ / hr. Then from 2350-2450℃ to 2800-3000℃ at a heating rate of 18-22℃ / hr. Keep at 2800-3000℃ for 2-5 hours. After the heat preservation, cool down to 100℃ at a cooling rate of 20-30℃ / hr.

[0091] A fourth aspect of the present invention provides an isotropic graphite material, which is prepared by the above-mentioned method for preparing the isotropic graphite material.

[0092] According to a specific embodiment of the present invention, preferably, the volume density of the isotropic graphite material is 1.88-1.92 mg / m 3 , resistivity is 7-9μΩ·m, flexural strength is 75-80Mpa, compressive strength is 90-95Mpa, elastic modulus is 7-8Gpa, thermal expansion coefficient is 4×10 -6 Up to 6×10 -6 K -1(Room temperature to 600°C), thermal conductivity is 100-120W / (m·K).

[0093] The technical solution of the present invention achieves at least the following beneficial effects:

[0094] 1. In view of the problem that the improvement of the existing isotropic graphite material preparation technology has limited improvement in product uniformity, strength, conductivity and yield rate, and cannot meet the use requirements of isotropic graphite high-purity, large-scale silicon crystal growth equipment graphite components, large electrodes, and core nuclear graphite materials, the present invention starts from improving the source raw materials for preparing isotropic graphite and the isotropic coke structure, strength, purity and other properties, fundamentally improving the comprehensive properties of isotropic graphite such as strength, volume density, conductivity, isotropy, uniformity, etc., and can meet the use requirements of photovoltaic silicon growth and large-size graphite in nuclear reactors.

[0095] The raw coke used in the existing isotropic graphite is mostly prepared from ordinary petroleum coke and coal-based asphalt coke. Its microstructure is mainly composed of streamlined fiber structure, flaky structure and mosaic structure of different sizes. The proportion of each structure fluctuates and is inconsistent due to the selection of raw materials and different process conditions, which affects the uniformity of the properties of isotropic graphite and the performance of mechanical and thermal conductivity, or the improper operation of the isotropic graphite processing process causes the graphite products to crack, the yield rate decreases, and the cost increases. In addition to the physical properties usually tested, the interaction between isotropic coke and the impregnant and binder has a great influence on the porosity, strength and resistance of the graphite products after roasting and graphitization. The coal-based impregnant asphalt, binder asphalt and petroleum coke are usually prepared by doping elements such as nitrogen or using heavy coal tar asphalt. Due to the high content of impurity elements and metals, lattice defects will be brought about after later heat treatment or graphitization, affecting the performance of capacity, and it will also bring certain environmental problems. When using petroleum raw materials, due to the high molecular fluidity, it is easy to form a streamlined structure, and it is difficult to obtain petroleum coke with the same structure.

[0096] The inventors of this case regulated the raw material composition of isotropic coke, used appropriate purification methods for different raw materials, made full use of the reactivity of different fraction oils, used the characteristics of biomass tar to provide coking stabilizing components, and prepared isotropic coke using delayed coking technology, thus solving the problem of insufficient performance of existing raw material coke.

[0097] Based on the above-mentioned innovative improvements, the inventors of this case provide an oil-based isotropic coke, the mosaic structure ratio of which is 80-90%, the carbon microcrystalline structure size is 1-20 μm, and the true density is 1.385-1.430 g / cm 3, the Hardgrove grindability index is 20-30%; based on the total weight of the raw coke, the ash content is 10-50ppm, the volatile content is 5-10%, the sulfur content is 0.2-0.4%, the nitrogen content is 0.1-0.2%, and the water content is 8-12%. By using this specific isotropic coke combined with the preparation process of isotropic graphite, the graphite products have excellent comprehensive properties such as strength, electrical conductivity, and thermal conductivity.

[0098] 2. The preparation of isotropic coke is a difficult point in the research of this field. From the perspective of the design of the reaction principle of the mesophase theory, when the impurities in the heavy aromatic components are removed and the content is low, the condensed aromatic molecules are easy to form large-sized carbon microcrystals, and then grow and develop into large crystal structures, and cannot generate small and uniform mosaic structures. When the non-carbon elements such as metals and non-metallic elements in the raw materials are high, the generated petroleum coke will affect the strength of the graphite products due to the escape of non-carbon elements after subsequent heat treatment and graphitization. The key problem is that cracking and pores lead to preparation failure. After in-depth research and creative practice, the inventors of this case strictly control the content of metal and non-metallic element impurities from the perspective of the reaction activity of the raw aromatic components of isotropic coke, and control the type of heavy oil, ash removal method, aromatic component structure and content, and introduce stabilizers to control the structure and strength of isotropic coke in view of the difficulty of continuous operation of the coking process of heavy aromatics. Specifically, specific fractions of petroleum crude oil, ethylene tar and biomass tar are used as raw materials. After purification and impurity removal, aromatic molecular design (pyrolysis), and adjustment of the microcrystalline structure size and distribution of the coke, the various steps and parameters are coordinated with each other, and finally high-strength, high-purity, structurally uniform isotropic coke is produced, and the preparation process can achieve continuous production.

[0099] 3. The preparation method of isotropic graphite material provided by the present invention adopts isotropic coke and cooked coke in combination with each other. The impregnating agent and adhesive required in the preparation process of isotropic graphite are consistent with the raw material source of coke, which promotes the increase of the bonding force between coke and asphalt during high-temperature treatment. The roasting and graphitization procedures are set according to the properties of the raw materials, so that the preparation process of isotropic graphite can achieve synchronous shrinkage, reduce the formation of cracks and pores in the heat treatment process, and improve the comprehensive properties of isotropic graphite such as strength, volume density, electrical conductivity, thermal conductivity, isotropy, uniformity and yield rate.

[0100] In summary, the present invention provides an oil-based isotropic coke and an isotropic graphite material and methods for preparing the same. The oil-based isotropic coke provided by the present invention fundamentally solves the problem that the existing special graphite made from petroleum coke or asphalt coke cannot meet the demand for isotropic graphite, and improves the isotropy, strength, purity, high-temperature shrinkage performance, etc. of the isotropic coke. In addition, the present invention matches the isotropic coke raw coke and cooked coke with each other, and combines the selection of impregnants and binders and the temperature control procedure in the preparation process of isotropic graphite to obtain an isotropic graphite material with excellent performance in various aspects such as strength, electrical conductivity, thermal conductivity, bulk density, isotropy, and uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Figure 1 This is a polarizing microscope photograph of the raw coke of the oil-based isotropic coke prepared in Example 1 of the present invention.

[0102] Figure 2 This is a polarizing microscope photograph of the raw coke of the oil-based isotropic coke prepared in Example 2 of the present invention.

[0103] Figure 3 A schematic structural diagram of a system for preparing oil-based isotropic coke and isotropic graphite material provided for a specific embodiment of the present invention.

[0104] Figure 4 This is a polarizing microscope photograph of the petroleum coke prepared in Comparative Example 1.

[0105] Figure 5 This is a polarizing microscope photograph of the pitch coke prepared in Comparative Example 2.

[0106] Description of Figure Numbers:

[0107] 1- atmospheric distillation device; 2- vacuum distillation device; 3- electric field separation device; 4- centrifuge; 5- sintered metal mesh filter; 6- four pipeline static mixers; 7- stirring mixer; 8- first distillation tower; 9- second distillation tower; 10- fixed bed reactor; 11- buffer tank; 12- preheating furnace; 13- heating furnace; 14- first coking reactor; 15- second coking reactor; 16- third coking reactor; 17- fractionation tower; 18- drying machine; 19- calcining furnace; 20- crushing device; 21- mixer; 22- roller mill; 23- isostatic pressing machine; 24- roasting furnace; 25- impregnation tank; 26- graphitization device; 27- molecular distillation device. DETAILED DESCRIPTION

[0108] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0109] In the following examples and comparative examples, if no specific experimental steps or conditions are specified, the experiments were carried out according to the conventional experimental steps or conditions in the art. The reagents or instruments used, if no manufacturer is specified, are all conventional products that can be purchased commercially.

[0110] Example 1

[0111] This embodiment provides an oil-based isotropic coke, and the preparation method thereof comprises the following steps:

[0112] S1. Raw material preparation:

[0113] After cutting off the light fraction below 370°C by normal pressure distillation of naphthenic crude oil, vacuum distillation is performed at 5Kpa to obtain three types of crude oil fractions at 370-400°C, 400-450°C and above 450°C;

[0114] After removing the light fraction below 260°C from ethylene tar and secondary biomass tar by normal pressure distillation, vacuum distillation is performed at 10Kpa to obtain three ethylene tar fractions of 270-300°C, 300-350°C and above 350°C, and three biomass tar fractions of 270-300°C, 300-350°C and above 350°C, respectively;

[0115] S2. Impurity removal and raw material preparation:

[0116] S201, mixing petroleum crude oil distillate above 450°C and petroleum crude oil distillate at 370-400°C in a weight ratio of 10:3, using a pipeline static mixer with a linear speed of 0.3 m / s, and then removing metal impurities through an electric field separation device to obtain a purified crude oil component, wherein the ash content of the purified crude oil component is 10 ppm; the electric field separation device used is a composite space of an electric field and a flow field containing filler balls, the filler balls are ceramic balls prepared from barium titanate, the sphere diameter is 200 μm, the electric field strength is 3 KV, the electric field separation device is designed as an uneven electric field, intermittent power supply and backwashing, the backwashing oil is 370-400°C petroleum crude oil distillate, the ash content in the oil after backwashing is 2%, and the contaminated backwashing oil can be returned to the catalytic cracking unit;

[0117] S202, filtering the ethylene tar fraction oil above 350° C. through a sintered metal mesh to remove impurities, with an absolute filtration accuracy of 5 μm and a filtration temperature of 330° C., to obtain purified ethylene tar pitch, wherein the ash content is 5 ppm, the softening point is 80° C., the toluene insoluble content is 10% (weight percentage), and the coking value is 25%;

[0118] S203, mixing the purified crude oil component and the purified ethylene tar asphalt in a weight ratio of 1:2, using a pipeline static mixer at a linear speed of 0.3 m / s to obtain a primary mixed oil;

[0119] S204, mixing the biomass tar fraction oil above 350°C and the biomass tar fraction oil at 270-300°C in a weight ratio of 10:1, using a pipeline static mixer with a linear velocity of 0.2 m / s, and then removing inorganic impurities by centrifugal filtration, the speed of the centrifuge used is 40000 r / min, the centrifugal filtration operating temperature is 150°C, and a purified biomass tar pitch is obtained, the ash content of which is 30 ppm;

[0120] S3. Raw material modification:

[0121] S301, mixing the stabilizer and the purified biomass tar pitch at a weight ratio of 0.1:100 at 190° C. by stirring at a stirring rate of 50 r / min to obtain purified biomass tar pitch containing the stabilizer;

[0122] The stabilizer is prepared by the following steps: distilling the secondary biomass tar under normal pressure to obtain a fraction oil below 330°C, then rectifying it to obtain a light fraction below 210°C, and then rectifying it to remove the fraction oil below 190°C to obtain a biomass tar fraction oil of 190-210°C, reacting the biomass tar fraction oil of 190-210°C with isobutylene in a fixed bed reactor filled with sulfonic acid resin at a mass ratio of 2:1, and the air velocity is 3h -1 , the reaction temperature is 90-100°C, the pressure is 0.1Mpa, and the stabilizer is obtained;

[0123] S302, mixing the primary mixed oil and the purified biomass tar pitch containing a stabilizer in a weight ratio of 10:4, using a pipeline static mixer at a linear speed of 0.3 m / s to obtain a modified raw material;

[0124] S4, Pyrolysis:

[0125] The modified raw material is buffered in a buffer tank and then enters a preheating furnace for heating. The outlet temperature of the preheating furnace is kept constant at 420° C. Then, the modified raw material enters the coking reactor from the bottom of the coking reactor to carry out a first-stage reaction. The bottom feed temperature of the coking reactor is 410° C. The pressure in the coking reactor is 0.3 MPa. The first-stage reaction time is 24 hours. The generated oil and gas flows out from the top of the first coking reactor and enters a fractionation tower for fractionation.

[0126] The 320-380°C distillate oil obtained from the fractionation tower is mixed with the 380-450°C distillate oil in a weight ratio of 1:1, and then heated in a heating furnace. The outlet temperature of the heating furnace is kept constant at 510°C, and then enters the coking reactor from the bottom of the coking reactor to carry out the second stage reaction. The bottom feed temperature of the coking reactor is 500°C, the pressure in the coking reactor is 0.6Mpa, and the second stage reaction time is 24 hours to obtain a coke precursor. The generated oil and gas flows out from the top of the first coking reactor and enters the fractionation tower for fractionation;

[0127] The 320-380°C distillate oil obtained by the fractionation tower is heated separately by a heating furnace, and the outlet temperature of the heating furnace is kept constant at 490°C, and then enters the coking reactor from the bottom of the coking reactor to carry out the third stage reaction. The bottom feed temperature of the coking reactor is 485°C, the pressure in the coking reactor is 0.15Mpa, and the third stage reaction time is 24 hours. The generated oil and gas flows out from the top of the coking reactor and enters the fractionation tower for fractionation;

[0128] Three coking reactors are used to perform the first stage reaction, the second stage reaction and the third stage reaction in an alternating cycle. The alternating cycle includes: when the first coking reactor performs the first stage reaction, the second coking reactor performs the second stage reaction, and the third coking reactor performs the third stage reaction; when the first coking reactor finishes the first stage reaction and performs the second stage reaction, the second coking reactor finishes the second stage reaction and performs the third stage reaction, and the third coking reactor finishes the third stage reaction and performs the first stage reaction; when the first coking reactor finishes the second stage reaction and performs the third stage reaction, the second coking reactor finishes the third stage reaction and performs the first stage reaction, and the third coking reactor finishes the first stage reaction and performs the second stage reaction;

[0129] After the third stage reaction of each coking reactor is completed, steam and water are introduced into the coking reactor to cool it down, and oil-based isotropic coke is obtained by discharging the material from the bottom of the coking reactor;

[0130] The pressure of the distillation tower is 0.12Mpa, the temperature at the bottom of the tower is 370°C, the temperature at the top of the tower is 110°C, the non-condensable gas is separated and discharged through the top of the distillation tower, the water and oil are separated by cooling, the small molecular gas hydrocarbons are collected, and the side line of the distillation tower respectively obtains distillate oils of 130-200°C, 200-320°C, 320-380°C, 380-450°C and above 450°C, the 130-200°C distillate oil is produced and collected through the top circulation, the 200-320°C distillate oil, the 320-380°C distillate oil and the 380-450°C distillate oil are produced and collected, and the distillate oil above 450°C is circulated at the bottom of the distillation tower to provide the heat required by the distillation tower.

[0131] The results show that the ratio of the mosaic structure of the oil-based isotropic coke prepared in this embodiment is 83%, the size of the carbon microcrystalline structure is 14-18 μm, and the true density is 1.397 g / cm 3 , the Hardgrove grindability index is 30%; based on the total weight of the green coke, the ash content is 20ppm, the volatile content is 9%, the sulfur content is 0.3%, the nitrogen content is 0.12%, and the water content is 10%. The polarizing microscope photo of the green coke is as follows Figure 1 shown.

[0132] The method for preparing the oil-based isotropic coke of this embodiment further comprises:

[0133] S5. Calcination:

[0134] The green coke is passed through a dryer to remove part of its moisture, and the water content of the dehydrated green coke is 3% (weight percentage). Then, after primary crushing and screening, green coke particles with a particle size of less than 10 mm and green coke particles with a particle size of 10-20 mm are selected and mixed in a weight ratio of 1:2, and then sent to a calcining furnace for calcination. The furnace entry temperature is 200°C, the heating rate is 40°C / min, the calcination zone temperature is 1400°C, the residence time is 2 hours, and then cooled at a cooling rate of 50°C / min to obtain oil-based isotropic coke.

[0135] The results show that the ratio of the mosaic structure of the oil-based isotropic coke prepared in this embodiment is 86%, the size of the carbon microcrystalline structure is 14-18 μm, and the true density is 2.137 g / cm 3 , the Hardgrove grindability index is 28%; based on the total weight of the cooked coke, the ash content is 28ppm, the volatile matter content is 0.3%, the sulfur content is 0.12%, the nitrogen content is 0.09%, and the water content is less than 0.1%.

[0136] This embodiment also provides an isotropic graphite material, and the preparation method thereof comprises the following steps:

[0137] (1) The green coke and cooked coke prepared in this example are crushed into particles with a D50 of 3 μm, the crushed green coke and cooked coke are mixed in a weight ratio of 1:10, and a binder with a D50 of 2 μm accounting for 40% of the total weight of the green coke and cooked coke is added and kneaded at an operating temperature of 230° C. to obtain a paste;

[0138] The binder is prepared by the following steps: using the purified ethylene tar pitch obtained in the above step S202 as a raw material, subjecting it to molecular distillation at an operating pressure of 2 Pa and a temperature of 280° C. to obtain a light component and a heavy component, collecting the light component by condensation, and slicing the heavy component after cooling to obtain the binder; after testing, the softening point of the binder is 200° C., the content of quinoline insoluble matter is 30% (weight percentage), the coking value is 70%, and the polarized structure is isotropic; the binder enters a jet mill to control its particle size D50 at 2 μm;

[0139] (2) After the paste is cooled, it is put into a roller mill for secondary crushing to control the particle size D50 to 4 μm, and then the particles after secondary crushing are loaded into a mold, vibrated and compacted to extract the gas, and then isostatically pressed at a pressure of 180 MPa to obtain a rectangular green body;

[0140] (3) After the embryo is taken out, the first roasting is carried out. The process of the first roasting is as follows:

[0141] Heating stage: from room temperature to 200°C at a heating rate of 8°C / hr, from 200°C to 300°C at a heating rate of 4°C / hr, from 300°C to 400°C at a heating rate of 3°C / hr, from 400°C to 600°C at a heating rate of 2°C / hr, and kept at 600°C for 24 hours, from 600°C to 900°C at a heating rate of 8°C / hr, from 900°C to 1100°C at a heating rate of 15°C / hr, and kept at 1100°C for 8 hours;

[0142] Cooling stage: cooling from 1100°C to 900°C at a cooling rate of 4°C / hr, cooling from 900°C to 600°C at a cooling rate of 8°C / hr, cooling from 600°C to 400°C at a cooling rate of 17°C / hr, and cooling from 400°C to 100°C at a cooling rate of 22°C / hr, ending the first roasting to obtain an initial carbon blank;

[0143] (4) After heating the initial carbon blank to 200° C., place it in an impregnation tank, seal it, evacuate it to a vacuum degree of 5 Kpa and keep it for 2 hours, then add the preheated impregnating agent to completely immerse the carbon blank, introduce argon gas and pressurize it to 2 MPa, keep the pressure for 1 hour, and then take it out;

[0144] Wherein, the impregnating agent is the purified ethylene tar pitch obtained in step S202;

[0145] (5) The carbon blank impregnated with asphalt is subjected to a second roasting. Considering the difference in properties between the impregnant and the binder, the second roasting process is as follows:

[0146] Heating stage: from room temperature to 100°C at a heating rate of 8°C / hr, from 100°C to 250°C at a heating rate of 4°C / hr, from 250°C to 400°C at a heating rate of 3°C / hr, from 400°C to 600°C at a heating rate of 2°C / hr, and kept at 600°C for 24 hours, from 600°C to 900°C at a heating rate of 5°C / hr, from 900°C to 1200°C at a heating rate of 10°C / hr, and kept at 1200°C for 12 hours;

[0147] Cooling stage: cooling from 1200°C to 900°C at a cooling rate of 4°C / hr, cooling from 900°C to 600°C at a cooling rate of 8°C / hr, cooling from 600°C to 400°C at a cooling rate of 12°C / hr, cooling from 400°C to 100°C at a cooling rate of 18°C / hr, and ending the second roasting;

[0148] (6) Repeating the asphalt impregnation and second calcination process of step (4) and step (5) three times to obtain a final carbon blank;

[0149] (7) The obtained carbon blank is graphitized, and the graphitization process is as follows: heating from room temperature to 1200°C at a heating rate of 25°C / hr, heating from 1200°C to 1400°C at a heating rate of 23°C / hr, heating from 1400°C to 1600°C at a heating rate of 22°C / hr, heating from 1600°C to 2000°C at a heating rate of 21°C / hr, heating from 2000°C to 2400°C at a heating rate of 23°C / hr, heating from 2400°C to 2800°C at a heating rate of 20°C / hr, keeping at 2800°C for 5 hours, and after the end of the keeping period, cooling to 100°C at a cooling rate of 25°C / hr to obtain the isotropic graphite material.

[0150] The volume density of the isotropic graphite material prepared in this embodiment is 1.89 mg / m 3 , resistivity is 9μΩ·m, flexural strength is 75Mpa, compressive strength is 91Mpa, elastic modulus is 8Gpa, thermal expansion coefficient is 4.7×10 - 6 K -1 (Room temperature to 600°C), thermal conductivity is 103W / (m·K).

[0151] Example 2

[0152] This embodiment provides an oil-based isotropic coke, and the preparation method thereof comprises the following steps:

[0153] S1. Raw material preparation:

[0154] After removing the light fraction below 370°C from the intermediate-cycloalkyl crude oil by normal pressure distillation, vacuum distillation is performed at 10Kpa to obtain three types of crude oil fractions at 370-400°C, 400-450°C and above 450°C;

[0155] After removing the light fraction below 260°C from ethylene tar and tertiary biomass tar by normal pressure distillation, vacuum distillation is performed at 15Kpa to obtain three ethylene tar fractions of 270-300°C, 300-350°C and above 350°C, and three biomass tar fractions of 270-300°C, 300-350°C and above 350°C, respectively;

[0156] S2. Impurity removal and raw material preparation:

[0157] S201, mixing petroleum crude oil distillate above 450°C and petroleum crude oil distillate at 370-400°C in a weight ratio of 10:4, using a pipeline static mixer with a linear speed of 0.5 m / s, and then removing metal impurities through an electric field separation device to obtain a purified crude oil component, wherein the ash content of the purified crude oil component is 10 ppm; the electric field separation device used is a composite space of an electric field and a flow field containing filler balls, the filler balls are ceramic balls prepared from lead zirconate titanate, the sphere diameter is 800 μm, the electric field strength is 10 KV, the electric field separation device is designed as an uneven electric field, intermittent power supply and backwashing, the backwashing oil is 370-400°C petroleum crude oil distillate, the ash content in the oil after backwashing is 2.3%, and the contaminated backwashing oil can be returned to the catalytic cracking unit;

[0158] S202, filtering the ethylene tar fraction above 350° C. through a sintered metal mesh to remove impurities, with an absolute filtration accuracy of 10 μm and a filtration temperature of 330-340° C., to obtain purified ethylene tar pitch, wherein the ash content is 10 ppm, the softening point is 90° C., the toluene insoluble content is 12% (weight percentage), and the coking value is 28%;

[0159] S203, mixing the purified crude oil component and the purified ethylene tar asphalt in a weight ratio of 1:4, using a pipeline static mixer at a linear speed of 0.5 m / s to obtain a primary mixed oil;

[0160] S204, mixing the biomass tar fraction oil above 350°C and the biomass tar fraction oil at 270-300°C in a weight ratio of 10:3, using a pipeline static mixer with a linear velocity of 0.4 m / s, and then removing inorganic impurities by centrifugal filtration, the speed of the centrifuge used is 80000 r / min, the centrifugal filtration operating temperature is 160°C, and a purified biomass tar pitch is obtained, the ash content of which is 50 ppm;

[0161] S3. Raw material modification:

[0162] S301, mixing the stabilizer and the purified biomass tar pitch at a weight ratio of 0.3:100 at 190-200° C. by stirring at a stirring rate of 100 r / min to obtain purified biomass tar pitch containing the stabilizer;

[0163] The stabilizer is prepared by the following steps: distilling the tertiary biomass tar under normal pressure to obtain a fraction oil below 330°C, then rectifying it to obtain a light fraction below 210°C, and then rectifying it to remove the fraction oil below 190°C to obtain a biomass tar fraction oil of 190-210°C, reacting the biomass tar fraction oil of 190-210°C with isobutylene in a fixed bed reactor filled with sulfonic acid resin at a mass ratio of 1.9:1, and the air velocity is 2h -1 , the reaction temperature is 100° C., the pressure is 0.12 MPa, and the stabilizer is obtained;

[0164] S302, mixing the primary mixed oil and the purified biomass tar pitch containing a stabilizer in a weight ratio of 10:4, using a pipeline static mixer at a linear speed of 0.4 m / s to obtain a modified raw material;

[0165] S4, Pyrolysis:

[0166] The modified raw material is buffered in a buffer tank and then enters a preheating furnace for heating. The outlet temperature of the preheating furnace is increased from 420° C. to 430° C. after 20 minutes. Then, the modified raw material enters the coking reactor from the bottom of the coking reactor to carry out the first stage reaction. The bottom feed temperature of the coking reactor is 420° C. The pressure in the coking reactor is 0.25 MPa. The first stage reaction time is 18 hours. The generated oil and gas flows out from the top of the first coking reactor and enters a fractionation tower for fractionation.

[0167] The 320-380°C distillate oil obtained from the fractionation tower is mixed with the 380-450°C distillate oil in a weight ratio of 1:10, and then heated in a heating furnace. The outlet temperature of the heating furnace is increased from 490°C to 520°C after 45 minutes, and then enters the coking reactor from the bottom of the coking reactor to carry out the second stage reaction. The bottom feed temperature of the coking reactor is 515°C, the pressure in the coking reactor is 0.58Mpa, and the second stage reaction time is 18 hours to obtain a coke precursor. The generated oil and gas flows out from the top of the first coking reactor and enters the fractionation tower for fractionation;

[0168] The 320-380°C distillate oil obtained by the fractionation tower is heated separately in a heating furnace. The outlet temperature of the heating furnace is raised from 490°C to 520°C after 45 minutes. Then, it enters the coking reactor from the bottom of the coking reactor to carry out the third stage reaction. The bottom feed temperature of the coking reactor is 515°C. The pressure in the coking reactor is 0.3Mpa. The third stage reaction time is 18 hours. The generated oil gas flows out from the top of the coking reactor and enters the fractionation tower for fractionation.

[0169] Three coking reactors are used to perform the first stage reaction, the second stage reaction and the third stage reaction in an alternating cycle. The alternating cycle includes: when the first coking reactor performs the first stage reaction, the second coking reactor performs the second stage reaction, and the third coking reactor performs the third stage reaction; when the first coking reactor finishes the first stage reaction and performs the second stage reaction, the second coking reactor finishes the second stage reaction and performs the third stage reaction, and the third coking reactor finishes the third stage reaction and performs the first stage reaction; when the first coking reactor finishes the second stage reaction and performs the third stage reaction, the second coking reactor finishes the third stage reaction and performs the first stage reaction, and the third coking reactor finishes the first stage reaction and performs the second stage reaction;

[0170] After the third stage reaction of each coking reactor is completed, steam and water are introduced into the coking reactor to cool it down, and oil-based isotropic coke is obtained from the bottom of the coking reactor;

[0171] The pressure of the distillation tower is 0.2Mpa, the temperature at the bottom of the tower is 390°C, the temperature at the top of the tower is 120°C, the non-condensable gas is separated and discharged through the top of the distillation tower, the water and oil are separated by cooling, the small molecular gas hydrocarbons are collected, and the side line of the distillation tower respectively obtains distillate oils of 130-200°C, 200-320°C, 320-380°C, 380-450°C and above 450°C, the 130-200°C distillate oil is produced and collected through the top circulation, the 200-320°C distillate oil, the 320-380°C distillate oil and the 380-450°C distillate oil are produced and collected, and the distillate oil above 450°C is circulated at the bottom of the distillation tower to provide the heat required by the distillation tower.

[0172] The results show that the ratio of the mosaic structure of the oil-based isotropic coke prepared in this embodiment is 90%, the size of the carbon microcrystalline structure is 5-10 μm, and the true density is 1.430 g / cm 3 , Hardgrove grindability index is 22%; based on the total weight of the green coke, the ash content is 40ppm, the volatile content is 7%, the sulfur content is 0.4%, the nitrogen content is 0.2%, and the water content is 9%. The polarizing microscope photo of the green coke is as follows Figure 2 shown.

[0173] The method for preparing the oil-based isotropic coke of this embodiment further comprises:

[0174] S5. Calcination:

[0175] The green coke is passed through a dryer to remove part of its moisture, and the water content of the dehydrated green coke is 4% (weight percentage). Then, after primary crushing and screening, green coke particles with a particle size of less than 10 mm and green coke particles with a particle size of 10-20 mm are selected and mixed in a weight ratio of 1:2, and then sent to a calcining furnace for calcination. The furnace entry temperature is 300°C, the heating rate is 40°C / min, the calcination zone temperature is 1600°C, the residence time is 2 hours, and then cooled at a cooling rate of 50°C / min to obtain oil-based isotropic coke.

[0176] The results show that the ratio of the mosaic structure of the oil-based isotropic coke prepared in this embodiment is 91%, the size of the carbon microcrystalline structure is 5-10 μm, and the true density is 2.147 g / cm 3 , the Hardgrove grindability index is 20%; based on the total weight of the cooked coke, the ash content is 50ppm, the volatile matter content is 0.1%, the sulfur content is 0.25%, the nitrogen content is 0.1%, and the water content is less than 0.1%.

[0177] This embodiment also provides an isotropic graphite material, and the preparation method thereof comprises the following steps:

[0178] (1) The green coke and cooked coke prepared in this example are crushed into particles with a D50 of 5 μm, the crushed green coke and cooked coke are mixed in a weight ratio of 1:2, and a binder with a D50 of 3 μm accounting for 35% of the total weight of the green coke and cooked coke is added and kneaded at an operating temperature of 300° C. to obtain a paste;

[0179] The binder is prepared by the following steps: using the purified ethylene tar pitch obtained in the above step S202 as a raw material, subjecting it to molecular distillation at an operating pressure of 5 pa and a temperature of 300° C. to obtain a light component and a heavy component, collecting the light component by condensation, and slicing the heavy component after cooling to obtain the binder; after testing, the softening point of the binder is 280° C., the content of quinoline insoluble matter is 40% (weight percentage), the coking value is 75%, and the polarized structure is isotropic; the binder enters a jet mill to control its particle size D50 at 3 μm;

[0180] (2) After the paste is cooled, it is put into a roller mill for secondary crushing to control the particle size D50 to 6 μm, and then the particles after secondary crushing are loaded into a mold, vibrated and compacted to extract the gas, and then isostatically pressed at a pressure of 240 MPa to obtain a rectangular green body;

[0181] (3) After the embryo is taken out, the first roasting is carried out. The process of the first roasting is as follows:

[0182] Heating stage: from room temperature to 200°C at a heating rate of 10°C / hr, from 200°C to 300°C at a heating rate of 7°C / hr, from 300°C to 400°C at a heating rate of 6°C / hr, from 400°C to 600°C at a heating rate of 4°C / hr, and kept at 600°C for 24 hours, from 600°C to 900°C at a heating rate of 8°C / hr, from 900°C to 1100°C at a heating rate of 15°C / hr, and kept at 1100°C for 15 hours;

[0183] Cooling stage: cooling from 1100°C to 900°C at a cooling rate of 7°C / hr, cooling from 900°C to 600°C at a cooling rate of 12°C / hr, cooling from 600°C to 400°C at a cooling rate of 17°C / hr, and cooling from 400°C to 100°C at a cooling rate of 22°C / hr, ending the first roasting to obtain an initial carbon blank;

[0184] (4) The initial carbon blank is heated to 180° C. and then placed in an impregnation tank, sealed, and evacuated to a vacuum degree of 20 KPa for 2 hours. Subsequently, the preheated impregnating agent is added to completely immerse the carbon blank, and argon gas is introduced to pressurize the carbon blank to 1 MPa and maintained for 3 hours before being taken out;

[0185] Wherein, the impregnating agent is the purified ethylene tar pitch obtained in step S202;

[0186] (5) The carbon blank impregnated with asphalt is subjected to a second roasting. Considering the difference in properties between the impregnant and the binder, the second roasting process is as follows:

[0187] Heating stage: from room temperature to 100°C at a heating rate of 10°C / hr, from 100°C to 250°C at a heating rate of 7°C / hr, from 250°C to 400°C at a heating rate of 6°C / hr, from 400°C to 600°C at a heating rate of 4°C / hr, and kept at 600°C for 24 hours, from 600°C to 900°C at a heating rate of 8°C / hr, from 900°C to 1200°C at a heating rate of 15°C / hr, and kept at 1200°C for 12 hours;

[0188] Cooling stage: cooling from 1200°C to 900°C at a cooling rate of 7°C / hr, cooling from 900°C to 600°C at a cooling rate of 8°C / hr, cooling from 600°C to 400°C at a cooling rate of 12°C / hr, cooling from 400°C to 100°C at a cooling rate of 22°C / hr, ending the second roasting to obtain the final carbon blank;

[0189] (6) The obtained carbon blank is graphitized, and the graphitization process is as follows: heating from room temperature to 1200°C at a heating rate of 25°C / hr, heating from 1200°C to 1400°C at a heating rate of 23°C / hr, heating from 1400°C to 1600°C at a heating rate of 22°C / hr, heating from 1600°C to 2000°C at a heating rate of 23°C / hr, heating from 2000°C to 2400°C at a heating rate of 20°C / hr, heating from 2400°C to 2800°C at a heating rate of 18°C / hr, keeping at 3000°C for 2 hours, and after the end of the heat preservation, cooling to 100°C at a cooling rate of 25°C / hr to obtain the isotropic graphite material.

[0190] The volume density of the isotropic graphite material prepared in this embodiment is 1.92 mg / m 3 , resistivity is 8μΩ·m, flexural strength is 78Mpa, compressive strength is 93Mpa, elastic modulus is 8Gpa, thermal expansion coefficient is 5.8×10 - 6 K -1 (Room temperature to 600°C), thermal conductivity is 113W / (m·K).

[0191] Example 3

[0192] This embodiment provides an oil-based isotropic coke, and the preparation method thereof comprises the following steps:

[0193] S1. Raw material preparation:

[0194] After cutting off the light fraction below 370°C by normal pressure distillation of naphthenic crude oil, vacuum distillation is performed at 8Kpa to obtain three types of crude oil fractions at 370-400°C, 400-450°C and above 450°C;

[0195] After removing the light fraction below 260°C from ethylene tar and primary biomass tar by normal pressure distillation, vacuum distillation is performed at 12Kpa to obtain three ethylene tar fractions of 270-300°C, 300-350°C and above 350°C, and three biomass tar fractions of 270-300°C, 300-350°C and above 350°C, respectively;

[0196] S2. Impurity removal and raw material preparation:

[0197] S201, mixing petroleum crude oil distillate above 450°C and petroleum crude oil distillate at 370-400°C in a weight ratio of 10:5, using a pipeline static mixer with a linear speed of 0.4 m / s, and then removing metal impurities through an electric field separation device to obtain a purified crude oil component, wherein the ash content of the purified crude oil component is 10 ppm; the electric field separation device used is a composite space of an electric field and a flow field containing filler balls, the filler balls are ceramic balls prepared from lead titanate, the sphere diameter is 1000 μm, the electric field strength is 10 KV, the electric field separation device is designed as an uneven electric field, intermittent power supply and backwashing, the backwashing oil is 370-400°C petroleum crude oil distillate, the ash content in the oil after backwashing is 2.53%, and the contaminated backwashing oil can be returned to the catalytic cracking unit;

[0198] S202, filtering the ethylene tar fraction oil above 350° C. through a sintered metal mesh to remove impurities, with an absolute filtration accuracy of 5 μm and a filtration temperature of 340° C., to obtain purified ethylene tar pitch, wherein the ash content is 5 ppm, the softening point is 110° C., the toluene insoluble content is 13% (weight percentage), and the coking value is 30%;

[0199] S203, mixing the purified crude oil component and the purified ethylene tar asphalt in a weight ratio of 1:4, using a pipeline static mixer at a linear speed of 0.3 m / s to obtain a primary mixed oil;

[0200] S204, mixing the biomass tar fraction oil above 350°C and the biomass tar fraction oil at 270-300°C in a weight ratio of 10:1, using a pipeline static mixer with a linear velocity of 0.4 m / s, and then removing inorganic impurities by centrifugal filtration, the speed of the centrifuge used is 40000 r / min, the centrifugal filtration operating temperature is 140°C, and obtaining a purified biomass tar pitch with an ash content of 34 ppm;

[0201] S3. Raw material modification:

[0202] S301, mixing the stabilizer and the purified biomass tar pitch at a weight ratio of 0.1:100 at 190° C. by stirring at a stirring rate of 80 r / min to obtain purified biomass tar pitch containing the stabilizer;

[0203] The stabilizer is prepared by the following steps: distilling the primary biomass tar under normal pressure to obtain a fraction oil below 330°C, then rectifying it to obtain a light fraction below 210°C, and then rectifying it to remove the fraction oil below 190°C to obtain a biomass tar fraction oil of 190-210°C, reacting the biomass tar fraction oil of 190-210°C with isobutylene in a fixed bed reactor filled with sulfonic acid resin at a mass ratio of 2.1:1, and the air velocity is 3h -1 , the reaction temperature is 90-100°C, the pressure is 0.11Mpa, and the stabilizer is obtained;

[0204] S302, mixing the primary mixed oil and the purified biomass tar pitch containing a stabilizer in a weight ratio of 10:2, using a pipeline static mixer at a linear speed of 0.2 m / s to obtain a modified raw material;

[0205] S4, Pyrolysis:

[0206] The pyrolysis process is the same as in Example 1, and oil-based isotropic coke is obtained.

[0207] The results show that the ratio of the mosaic structure of the oil-based isotropic coke prepared in this embodiment is 88%, the size of the carbon microcrystalline structure is 8-12 μm, and the true density is 1.397 g / cm 3 , the Hardgrove grindability index is 29%; based on the total weight of the green coke, the ash content is 25ppm, the volatile matter content is 10%, the sulfur content is 0.35%, the nitrogen content is 0.2%, and the water content is 12%.

[0208] The method for preparing the oil-based isotropic coke of this embodiment further comprises:

[0209] S5. Calcination:

[0210] The green coke is passed through a dryer to remove part of its moisture, and the water content of the dehydrated green coke is 5% (weight percentage). Then, after primary crushing and screening, green coke particles with a particle size of less than 10 mm and green coke particles with a particle size of 10-20 mm are selected and mixed in a weight ratio of 1:3, and then sent to a calcining furnace for calcination. The calcination conditions are the same as those in Example 1, and oil-based isotropic coke is obtained.

[0211] The results show that the ratio of the mosaic structure of the oil-based isotropic coke prepared in this embodiment is 89%, the size of the carbon microcrystalline structure is 8-12 μm, and the true density is 2.141 g / cm 3 , the Hardgrove grindability index is 26%; based on the total weight of the cooked coke, the ash content is 30ppm, the volatile matter content is 0.3%, the sulfur content is 0.23%, the nitrogen content is 0.1%, and the water content is less than 0.1%.

[0212] This embodiment also provides an isotropic graphite material, and the preparation method thereof comprises the following steps:

[0213] The green coke and cooked coke prepared in this embodiment are crushed into particles with a D50 of 6 μm, the crushed green coke and cooked coke are mixed in a weight ratio of 1:1, and a binder with a D50 of 2-3 μm accounting for 40% of the total weight of the green coke and the cooked coke is added and kneaded at an operating temperature of 230-330°C to obtain a paste; the paste is subjected to a process of crushing, blanking, first calcination, asphalt impregnation, second calcination, asphalt impregnation and second calcination repeated 3 times, and graphitization treatment to obtain an isotropic graphite material, and these steps are the same as those in Example 1.

[0214] The volume density of the isotropic graphite material prepared in this embodiment is 1.90 mg / m 3 , resistivity is 7μΩ·m, flexural strength is 76Mpa, compressive strength is 92Mpa, elastic modulus is 8Gpa, thermal expansion coefficient is 4.5×10 - 6 K -1 (Room temperature to 600°C), thermal conductivity is 110W / (m·K).

[0215] Example 4

[0216] This embodiment provides an isotropic graphite material, which is prepared using the oil-based isotropic coke green coke and cooked coke prepared in Example 2 as raw materials.

[0217] The preparation method of the isotropic graphite material of this embodiment comprises the following steps:

[0218] (1) The green coke and cooked coke prepared in Example 2 were crushed into particles with a D50 of 5 μm, the crushed green coke and cooked coke were mixed in a weight ratio of 1:5, and a binder with a D50 of 2 μm accounting for 37% of the total weight of the green coke and cooked coke was added and kneaded at an operating temperature of 280° C. to obtain a paste;

[0219] The binder is prepared by the following steps: using the purified ethylene tar pitch obtained in step S202 of Example 2 as a raw material, performing molecular distillation at an operating pressure of 2 Pa and a temperature of 280° C. to obtain a light component and a heavy component, collecting the light component by condensation, and slicing the heavy component after cooling to obtain the binder; after testing, the softening point of the binder is 262° C., the content of quinoline insoluble matter is 35% (weight percentage), the coking value is 72%, and the polarized structure is isotropic; the binder enters a jet mill to control its particle size D50 at 2 μm;

[0220] (2) After the paste is cooled, it is put into a roller mill for secondary crushing to control the particle size D50 to 6 μm, and then the particles after secondary crushing are loaded into a mold, vibrated and compacted to extract the gas, and then isostatically pressed at a pressure of 180 MPa to obtain a rectangular green body;

[0221] (3) After the embryo is taken out, the first roasting is carried out. The process of the first roasting is as follows:

[0222] Heating stage: from room temperature to 200°C at a heating rate of 10°C / hr, from 200°C to 300°C at a heating rate of 5°C / hr, from 300°C to 400°C at a heating rate of 5°C / hr, from 400°C to 600°C at a heating rate of 2°C / hr, and kept at 600°C for 20 hours, from 600°C to 900°C at a heating rate of 8°C / hr, from 900°C to 1100°C at a heating rate of 10°C / hr, and kept at 1100°C for 10 hours;

[0223] Cooling stage: cooling from 1100°C to 900°C at a cooling rate of 6°C / hr, cooling from 900°C to 600°C at a cooling rate of 8°C / hr, cooling from 600°C to 400°C at a cooling rate of 12°C / hr, and cooling from 400°C to 100°C at a cooling rate of 20°C / hr, ending the first roasting to obtain an initial carbon blank;

[0224] (4) After heating the initial carbon blank to 200° C., place it in an impregnation tank, seal it, evacuate it to a vacuum degree of 10 KPa and keep it for 4 hours, then add the preheated impregnating agent to completely immerse the carbon blank, introduce argon gas and pressurize it to 2 MPa, keep the pressure for 1 hour, and then take it out;

[0225] Wherein, the impregnating agent is the purified ethylene tar pitch obtained in step S202 of Example 2;

[0226] (5) The carbon blank impregnated with asphalt is subjected to a second roasting. Considering the difference in properties between the impregnant and the binder, the second roasting process is as follows:

[0227] Heating stage: from room temperature to 100°C at a heating rate of 10°C / hr, from 100°C to 250°C at a heating rate of 5°C / hr, from 250°C to 400°C at a heating rate of 5°C / hr, from 400°C to 600°C at a heating rate of 4°C / hr, and kept at 600°C for 24 hours, from 600°C to 900°C at a heating rate of 7°C / hr, from 900°C to 1200°C at a heating rate of 10°C / hr, and kept at 1200°C for 12 hours;

[0228] Cooling stage: cooling from 1200°C to 900°C at a cooling rate of 7°C / hr, cooling from 900°C to 600°C at a cooling rate of 10°C / hr, cooling from 600°C to 400°C at a cooling rate of 15°C / hr, cooling from 400°C to 100°C at a cooling rate of 20°C / hr, and ending the second roasting;

[0229] (6) Repeating the asphalt impregnation and second calcination process of step (4) and step (5) twice to obtain a final carbon blank;

[0230] (7) The obtained carbon blank is graphitized, and the graphitization process is as follows: heating from room temperature to 1200°C at a heating rate of 25°C / hr, heating from 1200°C to 1400°C at a heating rate of 23°C / hr, heating from 1400°C to 1600°C at a heating rate of 22°C / hr, heating from 1600°C to 2000°C at a heating rate of 21°C / hr, heating from 2000°C to 2400°C at a heating rate of 23°C / hr, heating from 2400°C to 2800°C at a heating rate of 20°C / hr, heating from 2800°C to 2900°C at a heating rate of 18°C / hr, keeping at 2900°C for 5 hours, and after the end of the keeping period, cooling to 100°C at a cooling rate of 25°C / hr to obtain the isotropic graphite material.

[0231] The volume density of the isotropic graphite material prepared in this embodiment is 1.91 mg / m 3 , resistivity is 7μΩ·m, flexural strength is 79Mpa, compressive strength is 93Mpa, elastic modulus is 8Gpa, thermal expansion coefficient is 5.2×10 - 6 K -1 (Room temperature to 600°C), thermal conductivity is 115W / (m·K).

[0232] The structure of the preparation system of the oil-based isotropic coke and isotropic graphite material used in the above embodiments is as follows: Figure 3 As shown, the system includes: three atmospheric distillation devices 1 and three vacuum distillation devices 2, which are used to perform atmospheric distillation and vacuum distillation on crude oil, ethylene tar and biomass tar respectively; an electric field separation device 3; a centrifuge 4; a sintered metal mesh filter 5; four pipeline static mixers 6; a stirring mixer 7; a first distillation tower 8; a second distillation tower 9; a fixed bed reactor 10; a buffer tank 11; a preheating furnace 12; a heating furnace 13; a first coking reactor 14; a second coking reactor 15; a second coking reactor 16; a fractionating tower 17; a drying machine 18; a calcining furnace 19; a pulverizing device 20; a mixer 21; a roller mill 22; an isostatic pressing machine 23; a roasting furnace 24; an impregnation tank 25; a graphitization device 26; and a molecular distillation device 27 (such as a scraped film evaporator).

[0233] Comparative Example 1

[0234] This comparative example provides a petroleum coke, and its preparation method comprises the following steps:

[0235] S1. Raw material preparation:

[0236] After removing the light fraction below 370°C by normal pressure distillation of paraffin-based crude oil, vacuum distillation is performed at 10Kpa to obtain petroleum crude oil distillate above 450°C;

[0237] S2. Pyrolysis:

[0238] The petroleum crude oil fraction above 450° C. is buffered in a buffer tank and then enters a heating furnace for heating. The outlet temperature of the heating furnace is kept constant at 495° C., and then enters a coking reactor from the bottom of the coking reactor for reaction. The bottom feed temperature of the coking reactor is 480° C. The pressure in the coking reactor is 0.2 MPa. The coking reaction time is 36 hours. The generated oil and gas flows out from the top of the coking reactor and enters a fractionation tower for fractionation. After the reaction is completed, water vapor and water are introduced into the coking reactor for cooling. Then, raw coke is obtained by discharging the material from the bottom of the coking reactor.

[0239] The pressure of the distillation tower is 0.18Mpa, the temperature at the bottom of the tower is 380°C, the temperature at the top of the tower is 120°C, the non-condensable gas is separated and discharged through the top of the distillation tower, the water and oil are separated by cooling, the small molecular gas hydrocarbons are collected, and the side line of the distillation tower respectively obtains distillate oils of 130-200°C, 200-320°C, 320-380°C, 380-450°C and above 450°C, the 130-200°C distillate oil is produced and collected through the top circulation, the 200-320°C distillate oil, the 320-380°C distillate oil and the 380-450°C distillate oil are produced and collected, and the distillate oil above 450°C is circulated at the bottom of the distillation tower to provide the heat required by the distillation tower.

[0240] The results show that the ratio of mosaic structure of the green coke prepared in this comparative example is 33%, the size of carbon microcrystalline structure is 20-1000 μm, and the true density is 1.379 g / cm 3 , Hardgrove grindability index is 90%; based on the total weight of the green coke, the ash content is 1300ppm, the volatile content is 12%, the sulfur content is 0.6%, the nitrogen content is 0.2%, and the water content is 10%. The polarizing microscope photo of the green coke is as follows Figure 4 shown.

[0241] The preparation method of the petroleum coke of this comparative example further comprises:

[0242] S3. Calcination:

[0243] The green coke is passed through a dryer to remove part of its moisture. The water content of the dehydrated green coke is 4% (weight percentage). Then, after primary crushing, the green coke is sent to a calcining furnace for calcination. The furnace entry temperature is 400°C, the heating rate is 50°C / min, the calcination zone temperature is 1500°C, the residence time is 2 hours, and then it is cooled at a cooling rate of 100°C / min to obtain cooked coke.

[0244] The results show that the ratio of mosaic structure of the cooked coke prepared in this comparative example is 22%, the size of carbon microcrystalline structure is 20-1000μm, and the true density is 2.135g / cm 3 , the Hardgrove grindability index is 60%; based on the total weight of the cooked coke, the ash content is 2000ppm, the volatile matter content is 0.3%, the sulfur content is 0.4%, the nitrogen content is 0.13%, and the water content is less than 0.1%.

[0245] This comparative example also provides an isotropic graphite material, and its preparation method comprises the following steps:

[0246] (1) The cooked coke prepared in this comparative example was crushed into particles with a D50 of 7-9 μm, and a binder with a D50 of 5 μm in an amount of 30% of the total weight of the cooked coke was added and kneaded at an operating temperature of 140° C. to obtain a paste;

[0247] The binder is coal tar modified asphalt (commercially available), the softening point of the binder is 110-120°C, the content of quinoline insoluble matter is 14% (weight percentage), the coking value is 57%, and the polarized structure contains anisotropic mesophase beads; the binder enters a jet mill to control its particle size D50 at 5 μm;

[0248] (2) After the paste is cooled, it is put into a roller mill for secondary crushing to control the particle size D50 to 9-10 μm, and then the particles after secondary crushing are loaded into a mold, vibrated and compacted to extract the gas, and then isostatically pressed at a pressure of 180 MPa to obtain a rectangular green body;

[0249] (3) After the embryo is taken out, the first roasting is carried out. The process of the first roasting is as follows:

[0250] Heating stage: heating from room temperature to 1100°C at a rate of 25°C / hr, and keeping at 1100°C for 10 hours;

[0251] Cooling stage: cooling from 1100°C to 400°C at a cooling rate of 25°C / hr, and from 400°C to 100°C at a cooling rate of 50°C / hr, to end the first roasting and obtain the initial carbon blank;

[0252] (4) After heating the initial carbon blank to 200° C., place it in an impregnation tank, seal it, evacuate it to a vacuum degree of 30 Kpa and keep it for 4 hours, then add the preheated impregnating agent to completely immerse the carbon blank, introduce argon gas and pressurize it to 2 MPa, keep the pressure for 1 hour, and then take it out;

[0253] Wherein, the impregnating agent is coal-based impregnating agent asphalt (commercially available), the ash content of the impregnating agent is 600ppm, the softening point is 89°C, the toluene insoluble content is 12% (weight percentage), and the coking value is 47%;

[0254] (5) The carbon blank impregnated with asphalt is subjected to a second roasting, and the process of the second roasting is as follows:

[0255] Heating stage: heating from room temperature to 1200°C at a rate of 25°C / hr, and keeping at 1200°C for 12 hours;

[0256] Cooling stage: cooling from 1200°C to 400°C at a rate of 25°C / hr, and from 400°C to 100°C at a rate of 20°C / hr, to end the second roasting;

[0257] (6) Repeating the asphalt impregnation and second calcination process of step (4) and step (5) twice to obtain a final carbon blank;

[0258] (7) The obtained carbon blank is graphitized, and the graphitization process is as follows: heating from room temperature to 1200°C at a heating rate of 25°C / hr, heating from 1200°C to 1400°C at a heating rate of 23°C / hr, heating from 1400°C to 1600°C at a heating rate of 22°C / hr, heating from 1600°C to 2000°C at a heating rate of 21°C / hr, heating from 2000°C to 2400°C at a heating rate of 23°C / hr, heating from 2400°C to 2800°C at a heating rate of 20°C / hr, heating from 2800°C to 3000°C at a heating rate of 18°C / hr, keeping at 3000°C for 5 hours, and after the end of the keeping period, cooling to 100°C at a cooling rate of 25°C / hr to obtain the isotropic graphite material.

[0259] The volume density of the isotropic graphite material prepared in this comparative example is 1.73 mg / m 3 , resistivity is 18μΩ·m, flexural strength is 32Mpa, compressive strength is 45Mpa, elastic modulus is 14Gpa, thermal expansion coefficient is 3.5×10 -6 K -1 (Room temperature to 600°C), thermal conductivity is 98W / (m·K).

[0260] Comparative Example 2

[0261] This comparative example provides a pitch coke, the preparation method of which comprises the following steps:

[0262] S1. Raw material preparation:

[0263] After removing the light fraction below 260°C from ethylene tar by atmospheric distillation, vacuum distillation is performed at 20Kpa to obtain ethylene tar pitch above 300°C;

[0264] S2. Pyrolysis:

[0265] The ethylene tar pitch at a temperature of more than 300° C. is buffered in a buffer tank and then enters a heating furnace for heating. The outlet temperature of the heating furnace is kept constant at 480° C., and then enters a coking reactor from the bottom of the coking reactor for reaction. The bottom feed temperature of the coking reactor is 465° C. The pressure in the coking reactor is 0.3 MPa. The coking reaction time is 36 hours. The generated oil and gas flows out from the top of the coking reactor and enters a fractionation tower for fractionation. After the reaction is completed, water vapor and water are introduced into the coking reactor for cooling. Then, raw coke is obtained by discharging the material from the bottom of the coking reactor.

[0266] The pressure of the distillation tower is 0.25Mpa, the temperature at the bottom of the tower is 380°C, the temperature at the top of the tower is 120°C, the non-condensable gas is separated and discharged through the top of the distillation tower, the water and oil are separated by cooling, the small molecular gas hydrocarbons are collected, and the side line of the distillation tower respectively obtains distillate oils of 130-200°C, 200-320°C, 320-380°C, 380-450°C and above 450°C, the 130-200°C distillate oil is produced and collected through the top circulation, the 200-320°C distillate oil, the 320-380°C distillate oil and the 380-450°C distillate oil are produced and collected, and the distillate oil above 450°C is circulated at the bottom of the distillation tower to provide the heat required by the distillation tower.

[0267] The results show that the ratio of the mosaic structure of the green coke prepared in this comparative example is 35%, the size of the carbon microcrystalline structure is 10-800 μm, and the true density is 1.342 g / cm 3 , Hardgrove grindability index is 95%; based on the total weight of the green coke, the ash content is 1000ppm, the volatile content is 17%, the sulfur content is 0.2%, the nitrogen content is 0.1%, and the water content is 10%. The polarizing microscope photo of the green coke is as follows Figure 5 shown.

[0268] The preparation method of the pitch coke of this comparative example further comprises:

[0269] S3. Calcination:

[0270] The green coke is passed through a dryer to remove part of its moisture. The water content of the dehydrated green coke is 4% (weight percentage). Then, after primary crushing, the green coke is sent to a calcining furnace for calcination. The furnace entry temperature is 400°C, the heating rate is 50°C / min, the calcination zone temperature is 1500°C, the residence time is 2 hours, and then it is cooled at a cooling rate of 100°C / min to obtain cooked coke.

[0271] The results show that the ratio of mosaic structure of the cooked coke prepared in this comparative example is 37%, the size of carbon microcrystalline structure is 10-800 μm, and the true density is 2.131 g / cm 3 , the Hardgrove grindability index is 47%; based on the total weight of the cooked coke, the ash content is 2300ppm, the volatile matter content is 0.3%, the sulfur content is 0.13%, the nitrogen content is 0.07%, and the water content is less than 0.1%.

[0272] This comparative example also provides an isotropic graphite material, and its preparation method comprises the following steps:

[0273] (1) The cooked coke prepared in this comparative example was crushed into particles with a D50 of 7-9 μm, and a binder with a D50 of 4 μm accounting for 34% of the total weight of the cooked coke was added and kneaded at an operating temperature of 170° C. to obtain a paste;

[0274] The binder is coal tar modified asphalt (commercially available), the softening point of the binder is 110-120°C, the quinoline insoluble content is 14% (weight percentage), the coking value is 57%, and the polarized structure contains anisotropic mesophase beads; the binder enters a jet mill to control its particle size D50 at 4 μm;

[0275] (2) After the paste is cooled, it is put into a roller mill for secondary crushing to control the particle size D50 to 8-10 μm, and then the particles after secondary crushing are loaded into a mold, vibrated and compacted to extract the gas, and then isostatically pressed at a pressure of 180 MPa to obtain a rectangular green body;

[0276] (3) After the embryo is taken out, the first roasting is carried out. The process of the first roasting is as follows:

[0277] Heating stage: heating from room temperature to 1100°C at a rate of 25°C / hr, and keeping at 1100°C for 10 hours;

[0278] Cooling stage: cooling from 1100°C to 400°C at a cooling rate of 25°C / hr, and from 400°C to 100°C at a cooling rate of 50°C / hr, to end the first roasting and obtain the initial carbon blank;

[0279] (4) After heating the initial carbon blank to 200° C., place it in an impregnation tank, seal it, evacuate it to a vacuum degree of 30 Kpa and keep it for 4 hours, then add the preheated impregnating agent to completely immerse the carbon blank, introduce argon gas and pressurize it to 2 MPa, keep the pressure for 1 hour, and then take it out;

[0280] Wherein, the impregnating agent is coal-based impregnating agent asphalt (commercially available), the ash content of the impregnating agent is 600ppm, the softening point is 89°C, the toluene insoluble content is 12% (weight percentage), and the coking value is 47%;

[0281] (5) The carbon blank impregnated with asphalt is subjected to a second roasting, and the process of the second roasting is as follows:

[0282] Heating stage: heating from room temperature to 1200°C at a rate of 25°C / hr, and keeping at 1200°C for 12 hours;

[0283] Cooling stage: cooling from 1200°C to 400°C at a rate of 25°C / hr, and from 400°C to 100°C at a rate of 20°C / hr, to end the second roasting;

[0284] (6) Repeating the asphalt impregnation and second calcination process of step (4) and step (5) twice to obtain a final carbon blank;

[0285] (7) The obtained carbon blank is graphitized, and the graphitization process is as follows: heating from room temperature to 1200°C at a heating rate of 25°C / hr, heating from 1200°C to 1400°C at a heating rate of 23°C / hr, heating from 1400°C to 1600°C at a heating rate of 22°C / hr, heating from 1600°C to 2000°C at a heating rate of 21°C / hr, heating from 2000°C to 2400°C at a heating rate of 23°C / hr, heating from 2400°C to 2800°C at a heating rate of 20°C / hr, heating from 2800°C to 3000°C at a heating rate of 18°C / hr, keeping at 3000°C for 5 hours, and after the end of the keeping period, cooling to 100°C at a cooling rate of 25°C / hr to obtain the isotropic graphite material.

[0286] The volume density of the isotropic graphite material prepared in this comparative example is 1.76 mg / m 3 , resistivity is 24μΩ·m, flexural strength is 30Mpa, compressive strength is 43Mpa, elastic modulus is 13Gpa, thermal expansion coefficient is 3.1×10 -6 K -1 (Room temperature to 600°C), thermal conductivity is 95W / (m·K).

[0287] Comparative Example 3

[0288] This comparative example provides an isotropic coke, and its preparation method is basically the same as that of Example 1, except that: in step S3, no stabilizer is used, and instead the primary mixed oil and purified biomass tar pitch are mixed in a weight ratio of 10:4 and used as the raw material for pyrolysis in step S4.

[0289] The raw coke prepared in this comparative example was found to have a non-uniform structure. In addition, coking occurred in the heating furnace tube in the second half of the feeding process. The reaction was stopped and the generated raw coke was analyzed. The bottom raw coke was found to have a mosaic structure ratio of 47%, a carbon microcrystalline structure size of 2-40 μm, and a true density of 1.362 g / cm 3 , the Hardgrove grindability index is 95%; based on the total weight of the green coke, the ash content is 13ppm, the volatile matter content is 18%, the sulfur content is 0.2%, the nitrogen content is 0.14%, and the water content is 9%.

[0290] The results show that the ratio of mosaic structure of the cooked coke prepared in this comparative example is 43%, the size of carbon microcrystalline structure is 2-40 μm, and the true density is 2.014 g / cm 3 , the Hardgrove grindability index is 70%; based on the total weight of the cooked coke, the ash content is 17ppm, the volatile content is 0.3%, the sulfur content is 0.3%, the nitrogen content is 0.2%, and the water content is less than 0.1%. This comparative example also provides an isotropic graphite material, which uses the green coke and cooked coke prepared in this comparative example as raw materials, and the specific preparation method is the same as that of Example 1.

[0291] The isotropic graphite material prepared in this comparative example cracked and the data could not be tested.

[0292] Comparative Example 4

[0293] This comparative example provides a kind of isotropic coke, and its preparation method is basically the same as that of Example 1, except that: the pyrolysis process of step S4 is different. Step S4 of this comparative example includes: without the second and third stage reactions, the modified raw material is buffered in the buffer tank and then enters the heating furnace for heating, the outlet temperature of the heating furnace is constant at 510°C, and then enters the coking reactor from the bottom of the coking reactor for reaction, the bottom feed temperature of the coking reactor is 500°C, the pressure in the coking reactor is 0.3Mpa, the coking reaction time is 24 hours, the generated oil and gas flows out from the top of the coking reactor and enters the fractionation tower for fractionation, after the reaction is completed, water vapor and water are introduced into the coking reactor for cooling operation, and then the raw coke is obtained by discharging from the bottom of the coking reactor.

[0294] The results show that the ratio of mosaic structure of the green coke prepared in this comparative example is 42%, the size of carbon microcrystalline structure is 2-50 μm, and the true density is 1.378 g / cm 3, the Hardgrove grindability index is 80%; based on the total weight of the green coke, the ash content is 10ppm, the volatile matter content is 16%, the sulfur content is 0.32%, the nitrogen content is 0.12%, and the water content is 11%.

[0295] The results show that the ratio of the mosaic structure of the cooked coke prepared in this comparative example is 39%, the size of the carbon microcrystalline structure is 2-50 μm, and the true density is 2.036 g / cm 3 , the Hardgrove grindability index is 55%; based on the total weight of the cooked coke, the ash content is 15ppm, the volatile matter content is 0.3%, the sulfur content is 0.35%, the nitrogen content is 0.2%, and the water content is less than 0.1%.

[0296] This comparative example also provides an isotropic graphite material, which uses the green coke and cooked coke prepared in this comparative example as raw materials, and the specific preparation method is the same as that of Example 1.

[0297] The volume density of the isotropic graphite material prepared in this comparative example is 1.74 mg / m 3 , resistivity is 12μΩ·m, flexural strength is 47Mpa, compressive strength is 51Mpa, elastic modulus is 6Gpa, thermal expansion coefficient is 3.4×10 -6 K -1 (Room temperature to 600°C), thermal conductivity is 72W / (m·K).

[0298] Comparative Example 5

[0299] This comparative example provides an isotropic graphite material, which uses only the cooked coke prepared in Example 1 as a raw material (without using green coke), and the specific preparation method is the same as that in Example 1.

[0300] The volume density of the isotropic graphite material prepared in this comparative example is 1.82 mg / m 3 , resistivity is 25μΩ·m, flexural strength is 42Mpa, compressive strength is 56Mpa, elastic modulus is 7Gpa, thermal expansion coefficient is 3.1×10 -6 K -1 (Room temperature to 600°C), thermal conductivity is 80W / (m·K).

[0301] Comparative Example 6

[0302] This comparative example provides an isotropic graphite material, and its preparation method is basically the same as that of Example 1, except that: the binder and the impregnant are different. The binder used in this comparative example is coal tar modified asphalt (commercially available), the softening point of the binder is 110-120°C, the quinoline insoluble content is 14% (weight percentage), the coking value is 57%, and the polarized structure contains anisotropic mesophase globules; the impregnant used is coal-based impregnant asphalt (commercially available), the ash content of the impregnant is 600ppm, the softening point is 89°C, the toluene insoluble content is 12% (weight percentage), and the coking value is 47%.

[0303] The volume density of the isotropic graphite material prepared in this comparative example is 1.78 mg / m 3 , resistivity is 37μΩ·m, flexural strength is 63Mpa, compressive strength is 72Mpa, elastic modulus is 3Gpa, thermal expansion coefficient is 4.3×10 -6 K -1 (Room temperature to 600°C), thermal conductivity is 75W / (m·K).

[0304] The properties of the isotropic graphite materials prepared in the above embodiments and comparative examples are shown in Tables 1 and 2 below.

[0305] Table 1

[0306] Example 1 Example 2 Example 3 Example 4 <![CDATA[Volume density mg / m 3 > 1.89 1.92 1.90 1.91 Resistivity μΩ·m 9 8 7 7 Flexural strengthMpa 75 78 76 79 Compressive strengthMpa 91 93 92 93 Elastic modulus Gpa 8 8 8 8 <![CDATA[Coefficient of thermal expansion × 10 -6 / K (from room temperature to 600 °C)]]> 4.7 5.8 4.5 5.2 Thermal conductivity W / (m·K) 103 113 110 115

[0307] Table 2

[0308]

[0309] It can be seen from the data in Table 1 and Table 2 that the present invention regulates the aromatic hydrocarbon composition and impurities of the oil-based raw materials, and after using the stabilizer produced by biomass tar to blend, the biomass tar fraction oil has a great ability to adjust the structure and performance of the coke produced by the original petroleum-based raw materials. After the modified raw coke and cooked coke are mixed in a specific ratio and matched with a suitable isotropic graphite preparation process, the volume density of isotropic graphite can be increased, the resistivity can be reduced, and the bending and compressive strengths can be increased. At the same time, since the heavy oil-based raw materials, especially ethylene tar pitch, are easy to block the pipeline due to heating during the delayed coking feeding process, the coke obtained using the low-temperature coking temperature has low strength and high volatile content, which can easily cause the problems of low strength and low yield of the graphite product in the later isotropic graphite process.

[0310] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing oil-based isotropic coke, wherein The following steps are involved: S1. Raw material preparation: The petroleum crude oil, ethylene tar and biomass tar are subjected to atmospheric distillation and vacuum distillation respectively to obtain at least 370-400°C and above 450°C petroleum crude oil fractions, 350°C and above ethylene tar fractions, and 270-300°C and above 350°C biomass tar fractions; S2. Impurity removal and raw material preparation: S201, mixing petroleum crude oil distillate above 450° C. and petroleum crude oil distillate at 370-400° C., and then removing impurities to obtain a purified crude oil component; S202, removing impurities from ethylene tar fraction oil above 350° C. to obtain purified ethylene tar pitch; S203, mixing the purified crude oil component and the purified ethylene tar asphalt to obtain a primary mixed oil; S204, mixing the biomass tar fraction oil above 350° C. and the biomass tar fraction oil at 270-300° C., and then removing impurities to obtain purified biomass tar pitch; S3. Raw material modification: S301, mixing a stabilizer and the purified biomass tar pitch to obtain a purified biomass tar pitch containing a stabilizer; S302, mixing the primary mixed oil and the purified biomass tar pitch containing a stabilizer to obtain a modified raw material; S4, Pyrolysis: The modified raw material is pyrolyzed to obtain green coke, which is the oil-based isotropic coke.

2. The method for preparing oil-based isotropic coke according to claim 1, in, In step S1, the petroleum crude oil includes naphthenic crude oil and / or intermediate-naphthenic crude oil; Preferably, step S1 specifically includes: After removing the light fraction below 370°C by normal pressure distillation of the crude oil, vacuum distillation is performed under the condition of 5-10Kpa to obtain three kinds of crude oil distillates at 370-400°C, 400-450°C and above 450°C; After the ethylene tar and the biomass tar are subjected to normal pressure distillation to cut off the light fraction below 260°C, they are subjected to reduced pressure distillation under the condition of 10-15Kpa to obtain three kinds of ethylene tar fraction oils at 270-300°C, 300-350°C and above 350°C, and three kinds of biomass tar fraction oils at 270-300°C, 300-350°C and above 350°C, respectively.

3. The method for preparing oil-based isotropic coke according to claim 1, in, Step S201 specifically includes: mixing petroleum crude oil distillate above 450° C. and petroleum crude oil distillate at 370-400° C. in a weight ratio of 10:3-5, and then removing metal impurities through an electric field separation device to obtain a purified crude oil component; Preferably, in step S201, the electric field separation device comprises a composite space of an electric field and a flow field containing filler balls, the filler balls comprise ceramic balls made of one or more of barium titanate, lead titanate, lead zirconate titanate and lead magnesium niobate, the diameter of the filler balls is 200-1000 μm, the intensity of the electric field is 3-10 KV, the electric field is designed to be a non-uniform electric field, and the energization mode of the electric field separation device is intermittent energization; Preferably, in step S201, the ash content of the purified crude oil component is 10-20 ppm; Preferably, step 202 specifically includes: filtering the ethylene tar fraction oil above 350° C. through a sintered metal mesh to remove impurities, thereby obtaining purified ethylene tar pitch; Preferably, in step S202, the ash content of the purified ethylene tar pitch is 5-10 ppm, the softening point is 80-120° C., the toluene insoluble content is 10-15%, and the coking value is 25-35%; Preferably, in step 203, the mixing weight ratio of the purified crude oil component and the purified ethylene tar asphalt is 1:2-4; Preferably, step 204 specifically comprises: mixing the biomass tar fraction oil above 350° C. and the biomass tar fraction oil at 270-300° C. in a weight ratio of 10:1-3, and then removing inorganic impurities by centrifugal filtration to obtain purified biomass tar pitch; Preferably, in step S204, the rotation speed of the centrifuge used in the centrifugal filtration is 30000-80000 r / min, and the operating temperature is 140-160° C.; Preferably, in step S204, the ash content in the purified biomass tar pitch is 30-50 ppm.

4. The method for preparing oil-based isotropic coke according to claim 1, in, Step S301 specifically includes: mixing the stabilizer and the purified biomass tar pitch at a weight ratio of 0.1-1:100 at 190-200° C. to obtain purified biomass tar pitch containing the stabilizer; Preferably, in step S301, the stabilizer is prepared by the following process: distilling and rectifying biomass tar to obtain 190-210°C biomass tar fraction oil, reacting the 190-210°C biomass tar fraction oil with isobutylene in the presence of a sulfonic acid resin to obtain the stabilizer; Preferably, in step S301, the mass ratio of the 190-210°C biomass tar fraction oil to the isobutylene is 1.9-2.1:1; Preferably, in step S301, the temperature of the reaction of the 190-210°C biomass tar fraction oil and the isobutylene in the presence of the sulfonic acid resin is 90-100°C and the pressure is 0.1-0.12Mpa; Preferably, in step S302, the mixing weight ratio of the primary mixed oil and the purified biomass tar pitch containing the stabilizer is 10:2-4.

5. The method for preparing oil-based isotropic coke according to claim 1, in, Step S4 specifically includes: The modified raw material is heated by a preheating furnace, and then enters the coking reactor from the bottom of the coking reactor to carry out a first-stage reaction, and the generated oil and gas flow out from the top of the coking reactor and enter the fractionation tower for fractionation; the 320-380°C distillate oil obtained by the fractionation tower is heated by a heating furnace alone or mixed with a 380-450°C distillate oil, and then enters the coking reactor from the bottom of the coking reactor to carry out a second-stage reaction to obtain a coke precursor, and the generated oil and gas flow out from the top of the coking reactor and enter the fractionation tower for fractionation; then the 320-380°C distillate oil obtained by the fractionation tower is heated by a heating furnace again, and continues to enter the coking reactor from the bottom of the coking reactor to carry out a third-stage reaction, and the generated oil and gas flow out from the top of the coking reactor and enter the fractionation tower for fractionation, and the raw coke obtained after the reaction is the oil-based isotropic coke; Preferably, in step S4, three coking reactors are used to perform the first stage reaction, the second stage reaction and the third stage reaction in an alternating cycle, and the alternating cycle includes: when the first coking reactor is performing the first stage reaction, the second coking reactor is performing the second stage reaction, and the third coking reactor is performing the third stage reaction; when the first coking reactor finishes the first stage reaction and performs the second stage reaction, the second coking reactor finishes the second stage reaction and performs the third stage reaction, and the third coking reactor finishes the third stage reaction and performs the first stage reaction; when the first coking reactor finishes the second stage reaction and performs the third stage reaction, the second coking reactor finishes the third stage reaction and performs the first stage reaction, and the third coking reactor finishes the first stage reaction and performs the second stage reaction.

6. The method for preparing oil-based isotropic coke according to claim 5, in, In step S4, the outlet temperature of the preheating furnace is 420-440°C; Preferably, in step S4, in the first stage reaction, the bottom feed temperature of the coking reactor is 410-430° C., the pressure in the coking reactor is 0.15-0.5 MPa, and the first stage reaction time is 12-24 hours; Preferably, in step S4, the pressure of the fractionation tower is 0.12-0.45Mpa, the bottom temperature is 370-390°C, the top temperature is 110-130°C, the non-condensable gas is separated and discharged through the top of the fractionation tower, the water and oil are separated by cooling, the small molecular gas hydrocarbons are collected, and the side line of the fractionation tower respectively obtains distillate oils of 130-200°C, 200-320°C, 320-380°C, 380-450°C and greater than 450°C, the 130-200°C distillate oil is produced and collected through the top circulation, the 200-320°C distillate oil, the 320-380°C distillate oil and the 380-450°C distillate oil are produced and collected, and the distillate oil greater than 450°C is circulated at the bottom of the fractionation tower to provide the heat required by the fractionation tower; Preferably, in step S4, the 320-380°C distillate oil and the 380-450°C distillate oil are mixed in a weight ratio of 1-10:10; Preferably, in step S4, the outlet temperature of the heating furnace is 490-520°C; Preferably, in step S4, in the second stage reaction, the bottom feed temperature of the coking reactor is 485-515° C., the pressure in the coking reactor is 0.5-0.8 MPa, and the second stage reaction time is 12-24 hours; Preferably, in step S4, in the third stage reaction, the bottom feed temperature of the coking reactor is 485-515° C., the pressure in the coking reactor is 0.15-0.5 MPa, and the time of the third stage reaction is 12-24 hours.

7. The method for preparing oil-based isotropic coke according to claim 1, in, The method for preparing the oil-based isotropic coke further comprises step S5: calcining the green coke at high temperature to obtain cooked oil-based isotropic coke; Preferably, step S5 specifically comprises: drying the green coke to obtain dehydrated green coke, crushing and screening, selecting green coke particles with a particle size of less than 10 mm and green coke particles with a particle size of 10-20 mm, mixing the green coke particles, and sending the green coke particles into a calcining furnace for calcining, and cooling the green coke to obtain oil-based isotropic coke cooked coke; Preferably, in step S5, the water content of the dehydrated green coke is 3-5%; Preferably, in step S5, the mixing weight ratio of the coke particles with a particle size of less than 10 mm and the coke particles with a particle size of 10-20 mm is 1:2-3; Preferably, in step S5, the inlet temperature of the calcining furnace is 200-300°C, the heating rate is 30-40°C / min, the calcining zone temperature is 1300-1600°C, the residence time of the mixed green coke particles in the calcining furnace is 1-3 hours, and the cooling rate is 40-50°C / min.

8. An oil-based isotropic coke prepared by the method for preparing the oil-based isotropic coke according to any one of claims 1 to 7.

9. The oil-based isotropic coke according to claim 8, in, The ratio of mosaic structure of oil-based isotropic coke is 80-90%, the size of carbon microcrystalline structure is 1-20μm, and the true density is 1.385-1.430g / cm 3 , the Hardgrove grindability index is 20-30%; based on the total weight of the green coke, the ash content is 10-50ppm, the volatile matter content is 5-10%, the sulfur content is 0.2-0.4%, the nitrogen content is 0.1-0.2%, and the water content is 8-12%.

10. The oil-based isotropic coke according to claim 8, in, The mosaic structure ratio of oil-based isotropic coke is 85-95%, the carbon microcrystalline structure size is 5-20μm, and the true density is 2.052-2.153g / cm 3 , the Hardgrove grindability index is 20-30%; based on the total weight of the cooked coke, the ash content is 10-50ppm, the volatile matter content is 0.1-0.3%, the sulfur content is 0.1-0.3%, the nitrogen content is 0.05-0.1%, and the water content is less than 0.1%.

11. A method for preparing an isotropic graphite material, The following steps are involved: The isotropic graphite material is obtained by kneading, crushing, forming, first calcination, asphalt impregnation, second calcination and graphitization of the oil-based isotropic coke and the binder as described in any one of claims 8 to 10.

12. The method for preparing the isotropic graphite material according to claim 11, in, The mixing ratio of the oil-based isotropic coke and the binder is: the mixing weight ratio of the green coke to the cooked coke is 1:1-10, and the amount of the binder is 35-45% of the total weight of the green coke and the cooked coke; Preferably, the particle size of the green coke and the cooked coke is 3-15 μm; Preferably, the particle size of the binder is 2-3 μm.

13. The method for preparing the isotropic graphite material according to claim 11, in, The binder is prepared by at least the following steps: molecular distilling purified ethylene tar pitch at an operating pressure of 2-5 Pa and a temperature of 280-300° C. to obtain a light component and a heavy component, collecting the light component by condensation, and cooling the heavy component to obtain the binder; Preferably, the ash content of the purified ethylene tar pitch is 5-10 ppm, the softening point is 80-120° C., the toluene insoluble content is 10-15%, and the coking value is 25-35%; Preferably, the softening point of the binder is 200-280° C., the content of quinoline insoluble matter is 30-40%, the coking value is 70-75%, and the polarizing structure is isotropic.

14. The method for preparing the isotropic graphite material according to claim 11, in, The kneading operation is 230-330°C; Preferably, the particle size of the particles obtained after the crushing is 4-16 μm; Preferably, the blank making is to load the crushed particles into a mold and perform isostatic pressing to obtain a green blank; more preferably, the pressure of the isostatic pressing is 180-240 MPa.

15. The method for preparing the isotropic graphite material according to claim 11, in, The process of the first roasting comprises: Heating stage: heating from room temperature to 190-210°C at a heating rate of 8-10°C / hr, heating from 190-210°C to 290-310°C at a heating rate of 4-7°C / hr, heating from 290-310°C to 390-410°C at a heating rate of 3-6°C / hr, heating from 390-410 to 590-610°C at a heating rate of 2-4°C / hr, keeping at 590-610°C for 15-24 hours, heating from 590-610°C to 890-910°C at a heating rate of 5-8°C / hr, heating from 890-910°C to 1050-1150°C at a heating rate of 10-15°C / hr, keeping at 1050-1150°C for 8-15 hours; Cooling stage: cool down from 1050-1150℃ to 890-910℃ at a cooling rate of 4-7℃ / hr, cool down from 890-910℃ to 590-610℃ at a cooling rate of 8-12℃ / hr, cool down from 590-610℃ to 390-410℃ at a cooling rate of 12-17℃ / hr, cool down from 390-410℃ to 90-110℃ at a cooling rate of 18-22℃ / hr, end the first roasting and obtain the initial carbon blank.

16. The method for preparing the isotropic graphite material according to claim 15, in, The asphalt impregnation specifically includes: heating the initial carbon blank to 180-200°C, placing it in an impregnation tank, sealing it, evacuating it to a vacuum degree of 5-20Kpa and maintaining it for 2-4 hours, then adding the preheated impregnating agent, completely immersing the carbon blank, passing inert gas and pressurizing it to 1-2Mpa, maintaining the pressure for 1-3 hours, and then taking it out; Preferably, the impregnating agent is purified ethylene tar pitch; the ash content of the purified ethylene tar pitch is 5-10 ppm, the softening point is 80-120° C., the toluene insoluble matter content is 10-15%, and the coking value is 25-35%.

17. The method for preparing the isotropic graphite material according to claim 11, in, The process of the second roasting comprises: Heating stage: heating from room temperature to 90-110°C at a heating rate of 8-10°C / hr, heating from 90-110°C to 240-260°C at a heating rate of 4-7°C / hr, heating from 240-260°C to 390-410°C at a heating rate of 3-6°C / hr, heating from 390-410°C to 590-610°C at a heating rate of 2-4°C / hr, keeping at 590-610°C for 20-28 hours, heating from 590-610°C to 890-910°C at a heating rate of 5-8°C / hr, heating from 890-910°C to 1150-1250°C at a heating rate of 10-15°C / hr, keeping at 1150-1250°C for 8-16 hours; Cooling stage: cool down from 1150-1250℃ to 890-910℃ at a cooling rate of 4-7℃ / hr, cool down from 890-910℃ to 590-610℃ at a cooling rate of 8-12℃ / hr, cool down from 590-610℃ to 390-410℃ at a cooling rate of 12-17℃ / hr, cool down from 390-410℃ to 90-110℃ at a cooling rate of 18-22℃ / hr, and end the second roasting.

18. The method for preparing the isotropic graphite material according to claim 11, in, The process of the bitumen impregnation and the second roasting is repeated 1-3 times.

19. The method for preparing the isotropic graphite material according to claim 11, in, The temperature of the graphitization treatment is 2800-3000°C, and the insulation time is 2-5 hours; Preferably, the graphitization process comprises: heating from room temperature to 1150-1250°C at a heating rate of 23-27°C / hr, heating from 1150-1250°C to 1350-1450°C at a heating rate of 21-25°C / hr, heating from 1350-1450°C to 1550-1650°C at a heating rate of 20-24°C / hr, heating from 1550-1450°C to 1550-1650°C at a heating rate of 19-23°C / hr, The temperature was raised from 0-1650℃ to 1950-2050℃, and then from 1950-2050℃ to 2350-2450℃ at a heating rate of 21-25℃ / hr, and then from 2350-2450℃ to 2800-3000℃ at a heating rate of 18-22℃ / hr, and then kept at 2800-3000℃ for 2-5 hours. After the end of the heat preservation, the temperature was reduced to 100℃ at a cooling rate of 20-30℃ / hr.

20. An isotropic graphite material, which is prepared by the method for preparing an isotropic graphite material according to any one of claims 11 to 19; Preferably, the volume density of the isotropic graphite material is 1.88-1.92 mg / m 3 , resistivity is 7-9μΩ·m, flexural strength is 75-80Mpa, compressive strength is 90-95Mpa, elastic modulus is 7-8Gpa, thermal expansion coefficient is 4×10 -6 Up to 6×10 -6 K -1 , thermal conductivity is 100-120W / (m·K).

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