CN107601496B - Nuclear graphite based on microcrystalline graphite as raw material and preparation method thereof - Google Patents
Nuclear graphite based on microcrystalline graphite as raw material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of microcrystalline graphite production, and discloses nuclear graphite based on microcrystalline graphite as a raw material and a preparation method thereof. Compared with various cokes in the prior art, the method can easily obtain the isotropic graphite with the isotropy ratio of 1.1-1.15 through isostatic pressing, and the green body thermal diffusivity of the microcrystalline graphite is far higher than that of the coke powder, so that the method is more favorable for roasting. The ash content and the boron equivalent in the nuclear graphite impurities prepared by the method meet the impurity requirements of the nuclear graphite.
Description
Technical Field
The invention relates to the technical field of microcrystalline graphite production, and particularly relates to nuclear graphite based on microcrystalline graphite as a raw material and a preparation method thereof.
Background
Graphite is a high-energy crystalline carbon material, and is widely applied to the fields of metallurgy, machinery, environmental protection, chemical industry, fire resistance, new energy, nuclear energy, electronics, medicine, military industry, aerospace and the like due to the unique structure and the characteristics of electric conduction, heat conduction, lubrication, high temperature resistance, stable chemical performance and the like.
The natural graphite in China has good forming geological conditions, wide distribution, rich resources and good quality, and reserves and yield are at the top of the world, so that the natural graphite is one of the dominant mineral products in China. Natural graphite can be divided into crystalline graphite and microcrystalline graphite according to different degrees of crystallization, wherein Chenzhou cryptocrystalline graphite accounts for about 74.7% of total reserves in China, and the cryptocrystalline graphite has good quality, high fixed carbon content and good isotropy.
However, for a long time, people pay attention to the exploitation and processing of crystalline graphite, neglect to develop and utilize microcrystalline graphite which occupies a large part of reserves, and the problems of low deep processing technology level and deep processing capability are not effectively solved for a long time. At present, raw ore and rough-machined products are mainly applied, resources cannot be fully utilized, even blind export is realized, and a large amount of mineral resources are lost and wasted.
Nuclear graphite is a graphite material used in the nuclear industry. There are neutron moderators for atomic reactors, reflecting agents, thermal column graphite for isotope production, spherical graphite and bulk graphite for high temperature gas cooled reactors, and the like. Currently commercialized nuclear graphite is produced from various coke types, and regarding the application of natural graphite, crystalline flake graphite has been successfully applied to HTR-spherical fuel elements, but there has been no report and research on the related use of cryptocrystalline graphite in the field of nuclear graphite.
Disclosure of Invention
Aiming at the problems that the existing natural microcrystalline graphite has good isotropy, the raw microcrystalline graphite generally has high fixed carbon content, but has complex impurity content, difficult purification, narrow application range and is not utilized for a long time, the invention takes the microcrystalline graphite as the raw material, improves the existing purification process, and fully reduces the energy consumption and the cost of purification, thereby providing the nuclear graphite preparation method based on the microcrystalline graphite as the raw material with low cost and low energy consumption.
The purpose of the invention is realized by the following technical scheme:
the preparation method of the nuclear graphite based on the microcrystalline graphite as the raw material comprises the following steps:
s1, raw ore treatment: crushing microcrystalline graphite raw ore with the fixed carbon content of 75-80%, deeply grinding the microcrystalline graphite raw ore to obtain a material with the fineness of-0.074 mm, performing flotation on a raw ore sample with the grinding fineness of-0.074 mm and the content of the material accounting for 90%, performing once roughing and once scavenging for four times, and then drying and magnetically separating to obtain microcrystalline graphite with the fixed carbon content of 85-90%;
s2, acid leaching and purifying:
s21, carrying out heat treatment on the microcrystalline graphite powder obtained in the step S1 at 600-800 ℃ for 1-3 min;
s22, mixing the minerals subjected to heat treatment in the step S2 with an alkali solution while the minerals are hot, carrying out ultrasonic treatment for 30min at an ore pulp liquid-solid ratio of 10-12: 1, then carrying out pressurized alkali leaching at the temperature of 100-110 ℃ for 2-3 h, and washing and drying leaching residues to obtain alkali-leached graphite;
s23, uniformly mixing the alkaline leaching graphite obtained in the step S3 with acid, wherein the acid is hydrochloric acid or sulfuric acid, the solid-to-solid ratio of ore pulp is 10-12: 1, performing ultrasonic treatment for 30min, performing normal-pressure acid leaching at the temperature of 100-110 ℃ for 2-3 h, washing graphite by leaching residues with distilled water or deionized water until the washing solution is neutral, precipitating, filtering and drying to obtain graphite powder, and the fixed carbon content is more than 99%;
s3, high-temperature purification: directly loading graphite powder into a graphite crucible, heating the graphite powder in a purification furnace filled with inert gas and protective gas step by step, firstly heating the graphite powder to 2500-2700 ℃ for 20-30 min, then heating the graphite powder to 2750-3000 ℃ for 30-40 min, and then gradually cooling the graphite powder to room temperature to obtain high-purity microcrystalline graphite with the fixed carbon content of more than 99.993%;
s4, secondary crushing: ball milling and screening the high-purity microcrystalline graphite obtained in the step S3 again to obtain the median particle diameter D50High-purity microcrystalline graphite of 40 μm;
s5, isostatic pressing: putting the product obtained in the step S4 into a rubber mold, and then putting the rubber mold into an isostatic pressing forming machine for forming, wherein the pressure is 100-300 MPa;
s6, roasting: roasting the product obtained in the step S5 at 800-1000 ℃ in an inert gas atmosphere, and then increasing the density to 1.78g/m through impregnation and heavy doping3The above;
s7, graphitization: and (4) putting the product obtained in the step (S6) into a graphitization furnace, firstly heating to 1000 ℃ at a speed of 20-30 ℃/min, then heating to 2800 ℃ at a speed of 10 ℃/min, keeping for 10h, and then naturally cooling to room temperature to finally obtain the nuclear graphite based on the microcrystalline graphite as the raw material.
Preferably, the raw microcrystalline graphite is lutang graphite, wherein the water content is 2.4%, the volatile matter is 2.99%, the ash content is 18.37%, and the carbon content is 78.64%, further solving the problem that Chenzhou cryptocrystalline graphite is not developed and utilized for a long time.
Preferably, the alkali solution in step S22 is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 10-30%.
Preferably, in the step S22, the ratio of liquid to solid of the ore pulp is 11:1, the temperature is 105 ℃, the reaction time is 2.5 hours, and the pressure in the pressurizing alkaline leaching process is 0.6-0.8 MPa.
Preferably, the drying in the step S22 and the step S23 is drying at the temperature of 80-150 ℃ for 2-3 h, the pulp liquid-solid ratio in the step S23 is 11:1, the temperature is 115 ℃, and the reaction time is 2.5 h; the acid is hydrochloric acid or sulfuric acid, the concentration of the hydrochloric acid is 2-37%, and the concentration of the sulfuric acid is 7-98%.
Preferably, the pressure in step S5 is 200 MPa.
Preferably, the inert gas in step S6 is nitrogen.
Preferably, the calcination temperature in step S6 is 1000 ℃.
Preferably, in step S7, the heating is first carried out at 25 deg.C/min to 1000 deg.C.
The invention also provides the nuclear graphite prepared by the method.
Compared with the prior art, the invention has the beneficial effects that:
compared with various cokes in the prior art, the method can easily obtain the isotropic graphite with the isotropy ratio of 1.1-1.15 through isostatic pressing, and the green body thermal diffusivity of the microcrystalline graphite is far higher than that of the coke powder, so that the method is more favorable for roasting. The ash content and the boron equivalent in the nuclear graphite impurities prepared by the method meet the impurity requirements of the nuclear graphite.
Drawings
Figure 1 flotation scheme.
FIG. 2 Transmission Electron micrograph of cryptocrystalline graphite Lutang.
FIG. 3 shows structural schematic diagram of cryptocrystalline graphite of Lutang.
Detailed Description
The invention is further illustrated by the following specific examples. The following examples are illustrative only and are not to be construed as unduly limiting the invention which may be embodied in many different forms as defined and covered by the summary of the invention. Reagents, compounds and apparatus employed in the present invention are conventional in the art unless otherwise indicated.
Example 1
The embodiment provides a preparation method of nuclear graphite based on microcrystalline graphite as a raw material, which comprises the following steps:
s1, raw ore treatment: crushing microcrystalline graphite raw ore, deeply grinding the microcrystalline graphite raw ore to obtain a material with the fineness of-0.074 mm, performing flotation on a raw ore sample with the grinding fineness of-0.074 mm and the content of the material accounting for 90 percent, performing once roughing and four times of fine selection and once scavenging flow, and then drying and magnetically separating to obtain microcrystalline graphite with the fixed carbon content of 90 percent;
in the embodiment, the raw microcrystalline graphite ore in the raw ore treatment is lutang graphite, wherein the water content is 2.4%, the volatile matter is 2.99%, and the ash content is 18.37% and the carbon content is 78.64%;
s2, acid leaching and purifying:
s21, carrying out heat treatment on the microcrystalline graphite powder obtained in the step S1 at 500-600 ℃ for 1 min;
s22, mixing the minerals subjected to heat treatment in the step S2 with an alkali solution while the minerals are hot, carrying out ultrasonic treatment for 30min at an ore pulp liquid-solid ratio of 10:1, then carrying out pressurized alkali leaching at the temperature of 100 ℃ for 2h, and washing and drying leaching residues to obtain alkali-leached graphite;
s23, uniformly mixing the alkaline leaching graphite obtained in the step S3 with acid, performing ultrasonic treatment for 30min by adopting hydrochloric acid or sulfuric acid with the pulp liquid-solid ratio of 10:1, performing normal-pressure acid leaching at the temperature of 100 ℃ for 2h, washing graphite by using distilled water or deionized water for leaching residues until the washing solution is neutral, precipitating, filtering and drying to obtain graphite powder with the fixed carbon content of 99.23%;
the alkali solution in this embodiment is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 10%; the pressure in the pressure alkaline leaching process is 0.6MPa, the acid is hydrochloric acid or sulfuric acid, the concentration of the hydrochloric acid is 2%, and the concentration of the sulfuric acid is 7%.
In the present embodiment, the drying in step S22 and step S23 is performed at a temperature of 80-150 ℃ for 2-3 h.
S3, high-temperature purification: directly loading graphite powder into a graphite crucible, heating the graphite powder in a purification furnace filled with inert gas and protective gas step by step, firstly heating the graphite powder to 2500-2700 ℃ for 20-30 min, then heating the graphite powder to 2750-3000 ℃ for 30-40 min, and then gradually cooling the graphite powder to room temperature to obtain high-purity microcrystalline graphite with the fixed carbon content of 99.993%;
s4, secondary crushing: ball milling and screening the high-purity microcrystalline graphite obtained in the step S3 again to obtain the median particle diameter D50High-purity microcrystalline graphite of 40 μm;
s5, isostatic pressing: putting the product obtained in the step S4 into a rubber mold, and then putting the rubber mold into an isostatic pressing forming machine for forming, wherein the pressure is 100 MPa;
s6, roasting: roasting the product obtained in the step S5 at 800 ℃ in an inert gas atmosphere, and then increasing the density to 1.78g/m by impregnation and heavy doping3The above;
s7, graphitization: and (4) putting the product obtained in the step (S6) into a graphitization furnace, firstly heating to 1000 ℃ at a speed of 20 ℃/min, then heating to 2800 ℃ at a speed of 10 ℃/min, keeping for 10h, and then naturally cooling to room temperature to finally obtain the nuclear graphite based on the microcrystalline graphite as the raw material.
Step S1, firstly, crushing and grinding the raw ore by using a microcrystalline stone mill, matching with a first rough concentration and four fine concentration of flotation and a first scavenging process, improving the purity of the raw ore by using a physical method to the maximum extent (if the grade of microcrystalline graphite with the fixed carbon content of 85-90 percent is further improved, the flotation method is technically or economically difficult to realize), reducing the grain size of the microcrystalline graphite, increasing the specific surface area of the microcrystalline graphite, being beneficial to subsequent acid leaching purification and gasification, and reducing the energy consumption and the cost of subsequent purification.
S2 the acid leaching purification firstly carries out high temperature pretreatment to the processed raw ore, then carries out acid-base method to purify the microcrystal graphite ore when it is hot, in the conventional process of acid-base method, the invention uses sulfuric acid or hydrochloric acid to replace HF, and uses pressurized alkali leaching to replace high temperature calcination, and simultaneously matches with the microcrystal graphite grinding ore after heat treatment to reduce the alkali leaching temperature in the acid-base method purification process, improve the alkali leaching efficiency, reduce the energy consumption, and simultaneously improve the graphite recovery rate, in addition, the invention also creatively optimizes the pulp liquid-solid ratio before the acid-base method reaction, adds ultrasonic treatment to further separate the microcrystal graphite and impurities, thereby improving the fixed carbon content, and simultaneously, the scrubbing action of ultrasonic wave makes the particle surface become smooth, the main principle is that the mechanical pulverization action and cavitation action in the ultrasonic process can pulverize the microcrystal graphite particles, part of impurities wrapped in the aggregate participate in the reaction, so that the reaction rate of the impurities and acid and alkali is accelerated, the content of fixed carbon is further improved, the subsequent gasification process is facilitated, and the purification energy consumption and cost are reduced.
Compared with the traditional high-temperature purification method, the high-temperature purification method in the step S3 directly raises the temperature to the highest temperature, a step-by-step heating mode is adopted, firstly, the temperature is lower than 2750 ℃ (the boiling point of silicate minerals), so that part of impurities with low melting points are gasified and removed firstly, the impurities remaining in the acid-base method are further discharged, then, the temperature is raised to be higher than 2750 ℃ to further gasify the silicate minerals, the step-by-step heating mode can avoid that the highest heating temperature is lower than that of microcrystalline graphite for heating from beginning to end, the energy consumption of graphite purification is reduced, and the influence of the temperature mutation of the temperature from the highest temperature to the room temperature after purification on the mechanical or chemical properties of.
Example 2
The embodiment provides a preparation method of nuclear graphite based on microcrystalline graphite as a raw material, which comprises the following steps:
s1, raw ore treatment: crushing microcrystalline graphite raw ore, deeply grinding the microcrystalline graphite raw ore to obtain a material with the fineness of-0.074 mm, performing flotation on a raw ore sample with the grinding fineness of-0.074 mm and the content of the material accounting for 90 percent, performing once roughing and four times of fine selection and once scavenging flow, and then drying and magnetically separating to obtain microcrystalline graphite with the fixed carbon content of 90 percent;
in the embodiment, the raw microcrystalline graphite ore in the raw ore treatment is lutang graphite, wherein the water content is 2.4%, the volatile matter is 2.99%, and the ash content is 18.37% and the carbon content is 78.64%;
s2, acid leaching and purifying:
s21, carrying out heat treatment on the microcrystalline graphite powder obtained in the step S1 at 600-800 ℃ for 3 min;
s22, mixing the minerals subjected to heat treatment in the step S2 with an alkali solution while the minerals are hot, carrying out ultrasonic treatment for 30min at an ore pulp-liquid-solid ratio of 11:1, then carrying out pressurized alkali leaching at the temperature of 105 ℃ for 2.5h, and washing and drying leaching residues to obtain alkali-leached graphite;
s23, uniformly mixing the alkaline leaching graphite obtained in the step S3 with acid, performing ultrasonic treatment for 30min by adopting hydrochloric acid or sulfuric acid with the pulp liquid-solid ratio of 11:1, performing normal-pressure acid leaching at the temperature of 115 ℃ for 2.5h, washing graphite by using distilled water or deionized water for leaching residues until the washing solution is neutral, precipitating, filtering and drying to obtain graphite powder with the fixed carbon content of 99.56%;
the alkali solution in this embodiment is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 20%; the pressure in the pressurizing alkaline leaching process is 0.6-0.8 MPa, the acid is hydrochloric acid or sulfuric acid, the concentration of the hydrochloric acid is 24%, and the concentration of the sulfuric acid is 98%.
In the present embodiment, the drying in step S22 and step S23 is performed at a temperature of 80-150 ℃ for 2-3 h.
S3, high-temperature purification: directly loading graphite powder into a graphite crucible, heating the graphite powder in a purification furnace filled with inert gas and protective gas step by step, firstly heating the graphite powder to 2500-2700 ℃ for 20-30 min, then heating the graphite powder to 2750-3000 ℃ for 30-40 min, and then gradually cooling the graphite powder to room temperature to obtain high-purity microcrystalline graphite with the fixed carbon content of 99.998%;
s4, secondary crushing: ball milling and screening the high-purity microcrystalline graphite obtained in the step S3 again to obtain the median particle diameter D50High-purity microcrystalline graphite of 40 μm;
s5, isostatic pressing: putting the product obtained in the step S4 into a rubber mold, and then putting the rubber mold into an isostatic pressing forming machine for forming, wherein the pressure is 200 MPa;
s6, roasting: putting the product obtained in the step S5 in an inert gas atmosphere for 90 DEGRoasting at 0 deg.C, and increasing the density to 1.78g/m by impregnation and heavy doping3The above;
s7, graphitization: and (4) putting the product obtained in the step (S6) into a graphitization furnace, firstly heating to 1000 ℃ at a speed of 25 ℃/min, then heating to 2800 ℃ at a speed of 10 ℃/min, keeping for 10h, and then naturally cooling to room temperature to finally obtain the nuclear graphite based on the microcrystalline graphite as the raw material.
Example 3
The embodiment provides a preparation method of nuclear graphite based on microcrystalline graphite as a raw material, which comprises the following steps:
s1, raw ore treatment: crushing microcrystalline graphite raw ore, then carrying out deep grinding on the microcrystalline graphite raw ore, obtaining a material with the fineness of-0.074 mm by grinding, carrying out flotation on a raw ore sample with the grinding fineness of-0.074 mm and the content of the material accounting for 90%, as shown in figure 1, adopting a once roughing and four times of fine selection and a once scavenging flow, and then drying and carrying out magnetic separation to obtain microcrystalline graphite with the fixed carbon content of 90%;
in the embodiment, the raw microcrystalline graphite ore in the raw ore treatment is lutang graphite, wherein the water content is 2.4%, the volatile matter is 2.99%, and the ash content is 18.37% and the carbon content is 78.64%;
s2, acid leaching and purifying:
s21, carrying out heat treatment on the microlite ink powder obtained in the step S1 at 800-1000 ℃ for 3 min;
s22, mixing the minerals subjected to heat treatment in the step S2 with an alkali solution while the minerals are hot, carrying out ultrasonic treatment for 30min at an ore pulp liquid-solid ratio of 12:1, then carrying out pressurized alkali leaching at the temperature of 110 ℃ for 3h, and washing and drying leaching residues to obtain alkali-leached graphite;
s23, uniformly mixing the alkaline leaching graphite obtained in the step S3 with acid, performing ultrasonic treatment for 30min by adopting hydrochloric acid or sulfuric acid with the pulp liquid-solid ratio of 12:1, performing normal-pressure acid leaching at the temperature of 110 ℃ for 3h, washing graphite by using distilled water or deionized water for leaching residues until the washing solution is neutral, precipitating, filtering and drying to obtain graphite powder with the fixed carbon content of 99.78%;
the alkali solution in this embodiment is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 30%; the pressure in the pressurizing alkaline leaching process is 0.6-0.8 MPa, the acid is hydrochloric acid or sulfuric acid, the concentration of the hydrochloric acid is 37%, and the concentration of the sulfuric acid is 98%.
In the present embodiment, the drying in step S22 and step S23 is performed at a temperature of 80-150 ℃ for 2-3 h.
S3, high-temperature purification: directly loading graphite powder into a graphite crucible, heating the graphite powder in a purification furnace filled with inert gas and protective gas step by step, firstly heating the graphite powder to 2500-2700 ℃ for 20-30 min, then heating the graphite powder to 2750-3000 ℃ for 30-40 min, and then gradually cooling the graphite powder to room temperature to obtain high-purity microcrystalline graphite with the fixed carbon content of 99.998%;
s4, secondary crushing: ball milling and screening the high-purity microcrystalline graphite obtained in the step S3 again to obtain the median particle diameter D50High-purity microcrystalline graphite of 40 μm;
s5, isostatic pressing: putting the product obtained in the step S4 into a rubber mold, and then putting the rubber mold into an isostatic pressing forming machine for forming, wherein the pressure is 300 MPa;
s6, roasting: roasting the product obtained in the step S5 at 1000 ℃ in an inert gas atmosphere, and then increasing the density to 1.78g/m by impregnation and heavy doping3The above;
s7, graphitization: and (4) putting the product obtained in the step (S6) into a graphitization furnace, firstly heating to 1000 ℃ at 30 ℃/min, then heating to 2800 ℃ at 10 ℃/min, keeping for 10h, and then naturally cooling to room temperature to finally obtain the nuclear graphite based on the microcrystalline graphite as the raw material.
Comparative example 1
The comparative example provides a preparation method of a nuclear graphite material, which adopts petroleum coke powder as a raw material for comparing aphanitic graphite and comprises the following steps:
s1, putting 30-60 parts by weight of petroleum coke powder and 70-45 parts by weight of asphalt powder into a kneading machine for kneading for 0.5-2 hours at the temperature of 100-200 ℃, then crushing to obtain a product with the particle size of not more than 40 mu m, putting the product into a rubber mold, and then putting the rubber mold into an isostatic pressing forming machine for forming at the pressure of 100-300 MPa;
s2, introducing halogen or halogen into the product obtained in the step S1Roasting in an atmosphere furnace for replacing hydrocarbon, wherein the treatment temperature is 800-1100 ℃, and the density is increased to 1.78g/m by adopting asphalt for multiple times of impregnation3The above;
s3, graphitizing the product obtained in the step S2 in a graphitizing furnace at the temperature of 2700-3200 ℃ for 10 hours to obtain a final nuclear graphite block finished product.
Characterization and results of Performance
The present invention adopts Chenzhou lutang microcrystalline graphite, the particles of which are composed of a plurality of graphite microcrystals smaller than 1 μm, and the diffraction pattern of the microcrystalline graphite in figure 2 shows that the microcrystals are randomly oriented, so that the microcrystalline graphite particles are isotropic, and the structure of the microcrystalline graphite particles is schematically shown in figure 3.
The material properties of examples 1 to 3 and comparative examples were tested, specifically shown in table 1, and the impurity content is shown in table 2.
TABLE 1
TABLE 2
As can be seen from Table 1, the nuclear graphite prepared by adopting the aphanitic graphite has high thermal conductivity, high graphitization, low isotropy ratio and higher bending strength compared with petroleum coke powder, compared with the prior art, the isotropic graphite with the isotropy ratio of 1.1-1.15 can be easily obtained by isostatic pressing, and the thermal diffusivity of the green compact of the microcrystalline graphite is far higher than that of the green compact of the coke powder, so that the roasting is more favorable.
As can be seen from table 2, the impurities of the nuclear graphite produced by the present invention are lower than those of comparative example 1, and the ash and boron equivalents meet the impurity requirements of the nuclear graphite.
Claims (9)
1. A preparation method of nuclear graphite based on microcrystalline graphite as a raw material is characterized by comprising the following steps:
s1, raw ore treatment: crushing microcrystalline graphite raw ore with the fixed carbon content of 75-80%, deeply grinding the microcrystalline graphite raw ore to obtain a material with the fineness of-0.074 mm, performing flotation on a raw ore sample with the grinding fineness of-0.074 mm and the content of the material accounting for 90%, performing once roughing and once scavenging for four times, and then drying and magnetically separating to obtain microcrystalline graphite with the fixed carbon content of 85-90%;
s2, acid leaching and purifying:
s21, carrying out heat treatment on the microcrystalline graphite powder obtained in the step S1 at 600-800 ℃ for 1-3 min;
s22, mixing the minerals subjected to heat treatment in the step S2 with an alkali solution while the minerals are hot, carrying out ultrasonic treatment for 30min at an ore pulp liquid-solid ratio of 10-12: 1, then carrying out pressurized alkali leaching at the temperature of 100-110 ℃ for 2-3 h, and washing and drying leaching residues to obtain alkali-leached graphite;
s23, uniformly mixing the alkaline leaching graphite obtained in the step S3 with acid, wherein the acid is hydrochloric acid or sulfuric acid, the solid-to-solid ratio of ore pulp is 10-12: 1, performing ultrasonic treatment for 30min, performing normal-pressure acid leaching at the temperature of 100-110 ℃ for 2-3 h, washing graphite by leaching residues with distilled water or deionized water until the washing solution is neutral, precipitating, filtering and drying to obtain graphite powder, and the fixed carbon content is more than 99%;
s3, high-temperature purification: directly loading graphite powder into a graphite crucible, heating the graphite powder in a purification furnace filled with inert gas and protective gas step by step, firstly heating the graphite powder to 2500-2700 ℃ for 20-30 min, then heating the graphite powder to 2750-3000 ℃ for 30-40 min, and then gradually cooling the graphite powder to room temperature to obtain high-purity microcrystalline graphite with the fixed carbon content of more than 99.993%;
s4, secondary crushing: performing ball milling and screening on the high-purity microcrystalline graphite obtained in the step S3 again to obtain high-purity microcrystalline graphite with a median particle size of D5040 mu m;
s5, isostatic pressing: putting the product obtained in the step S4 into a rubber mold, and then putting the rubber mold into an isostatic pressing forming machine for forming, wherein the pressure is 100-300 MPa;
s6, roasting: roasting the product obtained in the step S5 at 800-1000 ℃ in an inert gas atmosphere, and then increasing the density to 1.78g/m through impregnation and heavy doping3The above;
s7, graphitization: and (4) putting the product obtained in the step (S6) into a graphitization furnace, firstly heating to 1000 ℃ at a speed of 20-30 ℃/min, then heating to 2800 ℃ at a speed of 10 ℃/min, keeping for 10h, and then naturally cooling to room temperature to finally obtain the nuclear graphite based on the microcrystalline graphite as the raw material.
2. The method for preparing nuclear graphite based on microcrystalline graphite as raw material according to claim 1, wherein the microcrystalline graphite raw ore is lutang graphite with 2.4% moisture, 2.99% volatile matter, 18.37% ash and 78.64% carbon content in step S1.
3. The method for preparing nuclear graphite from microcrystalline graphite as a raw material according to claim 1, wherein the alkali solution in step S22 is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 10-30%.
4. The method for preparing nuclear graphite based on microcrystalline graphite as a raw material according to claim 1, wherein the slurry liquid-solid ratio in step S22 is 11:1, the temperature is 105 ℃, the reaction time is 2.5 hours, and the pressure in the pressure alkaline leaching process is 0.6-0.8 MPa.
5. The method for preparing nuclear graphite based on microcrystalline graphite as a raw material according to claim 1, wherein the drying in the steps S22 and S23 is drying at 80-150 ℃ for 2-3 h, the slurry liquid-solid ratio in the step S23 is 11:1, the temperature is 115 ℃, and the reaction is carried out for 2.5 h; the acid is hydrochloric acid or sulfuric acid, the concentration of the hydrochloric acid is 2-37%, and the concentration of the sulfuric acid is 7-98%.
6. The method for preparing nuclear graphite based on microcrystalline graphite as a raw material according to claim 1, wherein the pressure in step S5 is 200 MPa.
7. The method for preparing nuclear graphite based on microcrystalline graphite as a raw material according to claim 1, wherein the inert gas is nitrogen in step S6.
8. The method for preparing nuclear graphite based on microcrystalline graphite as a raw material according to claim 1, wherein the roasting temperature in the step S6 is 1000 ℃.
9. The method for preparing nuclear graphite based on microcrystalline graphite as a raw material according to claim 1, wherein the step S7 is first heated to 1000 ℃ at 25 ℃/min.
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| CN101823707A (en) * | 2010-04-28 | 2010-09-08 | 四川广汉士达炭素股份有限公司 | Technical method for producing isostatic pressure graphite |
| CN102502595A (en) * | 2011-10-14 | 2012-06-20 | 上海理工大学 | Preparation method of isotropic graphite |
| CN102502603A (en) * | 2011-11-01 | 2012-06-20 | 雅安恒圣高纯石墨科技有限责任公司 | Production process of large isotropic and isostatic high purity graphite with fine particles |
| CN104401982A (en) * | 2014-11-13 | 2015-03-11 | 东莞市翔丰华电池材料有限公司 | Nuclear graphite material preparation method |
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| CN101823707A (en) * | 2010-04-28 | 2010-09-08 | 四川广汉士达炭素股份有限公司 | Technical method for producing isostatic pressure graphite |
| CN102502595A (en) * | 2011-10-14 | 2012-06-20 | 上海理工大学 | Preparation method of isotropic graphite |
| CN102502603A (en) * | 2011-11-01 | 2012-06-20 | 雅安恒圣高纯石墨科技有限责任公司 | Production process of large isotropic and isostatic high purity graphite with fine particles |
| CN104401982A (en) * | 2014-11-13 | 2015-03-11 | 东莞市翔丰华电池材料有限公司 | Nuclear graphite material preparation method |
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