CN114890793A - Preparation method of high-purity high-density graphite material - Google Patents
Preparation method of high-purity high-density graphite material Download PDFInfo
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- CN114890793A CN114890793A CN202210555270.3A CN202210555270A CN114890793A CN 114890793 A CN114890793 A CN 114890793A CN 202210555270 A CN202210555270 A CN 202210555270A CN 114890793 A CN114890793 A CN 114890793A
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- 239000007770 graphite material Substances 0.000 title claims abstract description 28
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 238000005087 graphitization Methods 0.000 claims abstract description 64
- 239000000654 additive Substances 0.000 claims abstract description 40
- 230000000996 additive effect Effects 0.000 claims abstract description 40
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 37
- 239000000463 material Substances 0.000 claims abstract description 32
- 238000000034 method Methods 0.000 claims abstract description 31
- 239000010426 asphalt Substances 0.000 claims abstract description 28
- 239000010439 graphite Substances 0.000 claims abstract description 25
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 25
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 24
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 24
- 239000011737 fluorine Substances 0.000 claims abstract description 24
- 239000012535 impurity Substances 0.000 claims abstract description 20
- 239000000843 powder Substances 0.000 claims abstract description 14
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 claims abstract description 11
- 238000000227 grinding Methods 0.000 claims abstract description 11
- 238000003825 pressing Methods 0.000 claims abstract description 6
- 238000004321 preservation Methods 0.000 claims description 24
- 238000004898 kneading Methods 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 17
- 239000002245 particle Substances 0.000 claims description 17
- 238000007598 dipping method Methods 0.000 claims description 14
- 238000007580 dry-mixing Methods 0.000 claims description 12
- 239000011331 needle coke Substances 0.000 claims description 11
- 238000000465 moulding Methods 0.000 claims description 10
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 claims description 10
- ORUIBWPALBXDOA-UHFFFAOYSA-L magnesium fluoride Chemical compound [F-].[F-].[Mg+2] ORUIBWPALBXDOA-UHFFFAOYSA-L 0.000 claims description 9
- 229910001635 magnesium fluoride Inorganic materials 0.000 claims description 9
- 150000002222 fluorine compounds Chemical group 0.000 claims description 7
- 238000000462 isostatic pressing Methods 0.000 claims description 7
- 238000009835 boiling Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- OYLGJCQECKOTOL-UHFFFAOYSA-L barium fluoride Chemical compound [F-].[F-].[Ba+2] OYLGJCQECKOTOL-UHFFFAOYSA-L 0.000 claims description 5
- 229910001632 barium fluoride Inorganic materials 0.000 claims description 5
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 5
- 229910001634 calcium fluoride Inorganic materials 0.000 claims description 5
- 238000000354 decomposition reaction Methods 0.000 claims description 5
- 235000013024 sodium fluoride Nutrition 0.000 claims description 5
- 239000011775 sodium fluoride Substances 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 5
- 238000000748 compression moulding Methods 0.000 claims description 4
- 229910001512 metal fluoride Inorganic materials 0.000 claims description 4
- 239000003245 coal Substances 0.000 claims description 3
- 239000000571 coke Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 238000005086 pumping Methods 0.000 claims description 2
- 238000000746 purification Methods 0.000 abstract description 15
- 230000000694 effects Effects 0.000 abstract description 8
- 239000002994 raw material Substances 0.000 abstract description 5
- 238000002309 gasification Methods 0.000 abstract description 3
- 230000007547 defect Effects 0.000 abstract description 2
- 239000000047 product Substances 0.000 description 67
- 239000007789 gas Substances 0.000 description 23
- 238000002791 soaking Methods 0.000 description 20
- 229910052736 halogen Inorganic materials 0.000 description 8
- 150000002367 halogens Chemical class 0.000 description 8
- 239000007788 liquid Substances 0.000 description 8
- 238000005070 sampling Methods 0.000 description 7
- 239000011300 coal pitch Substances 0.000 description 6
- 230000000630 rising effect Effects 0.000 description 6
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 5
- 229910052801 chlorine Inorganic materials 0.000 description 5
- 239000000460 chlorine Substances 0.000 description 5
- 238000011049 filling Methods 0.000 description 5
- 238000007796 conventional method Methods 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 239000012467 final product Substances 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- 239000012466 permeate Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000011280 coal tar Substances 0.000 description 1
- 238000004939 coking Methods 0.000 description 1
- 238000007723 die pressing method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000006253 pitch coke Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
- C04B35/528—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components
- C04B35/532—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components containing a carbonisable binder
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- C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
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- C04B2235/30—Constituents and secondary phases not being of a fibrous nature
- C04B2235/44—Metal salt constituents or additives chosen for the nature of the anions, e.g. hydrides or acetylacetonate
- C04B2235/444—Halide containing anions, e.g. bromide, iodate, chlorite
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Abstract
The invention discloses a preparation method of a high-purity high-density graphite material, relates to the technical field of graphite materials, and aims to solve the problem that the existing purification method for preparing the high-purity high-density graphite product needs to be improved; the method comprises the steps of preparing coke powder, asphalt and a primary additive into materials according to a certain proportion, wherein the primary additive can generate fluorine gas in the products during primary graphitization for removing impurities and purifying the products, and the prepared materials are uniformly mixed; grinding the uniformly mixed materials into fine powder and pressing and forming, and sequentially carrying out primary roasting and primary graphitization on a formed green body; after the primary graphitized product is impregnated, secondary roasting and secondary graphitization are sequentially carried out to obtain a high-purity high-density graphite product; according to the invention, the fluoride is mixed into the raw material and uniformly distributed in the product, and the fluorine gas is decomposed and generated in the high-temperature graphitization process, is combined with impurities for gasification and escapes from the product, so that the defect of different internal and external purities of the traditional ventilating and purifying product is overcome, and the effect of uniform purification is achieved.
Description
Technical Field
The invention relates to the technical field of graphite materials, in particular to a preparation method of a high-purity high-density graphite material.
Background
The high-purity high-density graphite belongs to a high-end product in the field of graphite materials, has a very excellent application prospect, but the production of the material faces serious challenges, which is mainly reflected in that the existing high-purity graphite is always required to be purified, the most effective mode is to introduce halogen gases such as fluorine, chlorine and the like in a graphitization stage, and the fluorine and the chlorine are combined with impurities at high temperature and volatilized to achieve the purification purpose, and the invention patent with the publication number of CN105271216A and the name of 'a preparation method of high-purity graphite' discloses the common purification method.
However, the purification method of introducing halogen gas such as fluorine, chlorine and the like into the high-purity high-density graphite in the graphitization stage has the following problems: firstly, halogen gas is input from the outside, permeates into the interior from the surface through the open pores of the graphite product, and as the specification of the graphite product is increased, the permeation of the gas in the graphite product is very difficult, so that impurities on the surface and in the product are in gradient distribution, the purity of the product is uneven, and the using effect of the product is seriously affected; secondly, the impurities are gasified at high temperature and the halogen gas and the impurities are combined and gasified to escape, so that the internal pores of the product are enlarged or increased, the compactness of the final product is reduced, and the high-density material is likely to crack and the yield is seriously reduced; in addition, when large-sized graphite products are prepared, because of the difficulty in removing impurities, in order to ensure the purity of the large-sized products, coke powder with a large particle size is generally selected as a raw material to prepare a graphite material, so that the purification effect is improved, the compactness of the material is reduced, the high-purity high-density graphite product is difficult to prepare by the conventional method, and particularly, the preparation method of the large-sized high-purity high-density graphite product needs to be improved, so that a preparation method of the high-purity high-density graphite material is urgently needed to solve the problem.
Disclosure of Invention
The invention aims to provide a preparation method of a high-purity high-density graphite material, which aims to solve the problem that the existing purification method for preparing the high-purity high-density graphite product needs to be improved.
In order to achieve the purpose, the invention provides the following technical scheme: a preparation method of a high-purity high-density graphite material comprises the following steps: preparing coke powder, asphalt and a primary additive into materials according to a certain proportion, wherein the primary additive can generate fluorine gas in the products during primary graphitization for removing impurities and purifying the products, and the prepared materials are uniformly mixed; grinding the uniformly mixed materials into fine powder and pressing and forming, and sequentially carrying out primary roasting and primary graphitization on a formed green body; and after the primary graphitized product is impregnated, secondary roasting and secondary graphitization are sequentially carried out to obtain a high-purity high-density graphite product.
Preferably, the primary additive is a fluoride, and the boiling point of the remaining material is not higher than the primary graphitization temperature after decomposition to generate fluorine gas during graphitization.
Preferably, the coke powder is needle coke or asphalt coke, the average particle size is 5-50 μm, and the mass accounts for 60-80% of the total mass of the material; the asphalt is medium-temperature coal asphalt, and the mass of the asphalt accounts for 20-40% of the total mass of the material; the primary additive is fluoride, and the mass of the primary additive accounts for 0.1-1.0% of the total mass of the material.
Preferably, a secondary additive accounting for 0.1-0.5% of the mass of the impregnant is added into the impregnant, the secondary additive is fluoride, after the fluoride is decomposed and generated during graphitization, the boiling point of the residual substance is not higher than the secondary graphitization temperature, and the secondary additive can generate the fluoride inside a product during graphitization for removing impurities and purifying the impregnant and the product; the dipping temperature is 200-260 ℃, the dipping time is 2-6 h, the vacuum pumping is carried out before the dipping, and the pressure is maintained at 2-5 MPa in the dipping process.
Preferably, the primary graphitization and the secondary graphitization both adopt a direct heating method, and the graphitization furnace adopts an internal heat series furnace with the maximum temperature of 2800-3000 ℃.
Preferably, the materials are mixed and kneaded by a kneading machine, the coke powder and the primary additive are added firstly and are dry-mixed for 10-30 min at the dry-mixing temperature of 60-120 ℃, the asphalt is added and is wet-mixed for 20-40 min at the kneading temperature of 150-220 ℃.
Preferably, the average particle size of the fine powder is 10-80 μm, the maximum particle size is not more than 200 μm, the compression molding mode is mould pressing or isostatic pressing, the molding pressure is 160-250 MPa, and the pressure maintaining time is 5-30 min.
Preferably, the primary roasting temperature is 800-1000 ℃, the heating rate is 1-10 ℃/h, and the heat preservation is carried out for 10-20 h at the highest temperature.
Preferably, the secondary roasting is high-pressure roasting, the pressure is 1.0-3.0 MPa, the maximum temperature is 700-900 ℃, the heating rate is 1-10 ℃/h, and the heat preservation is carried out for 10-20 h at the maximum temperature.
Preferably, the fluoride is a metal fluoride including, but not limited to, one or more of magnesium fluoride, barium fluoride, calcium fluoride, and sodium fluoride.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the preparation method of the high-purity high-density graphite material, the fluoride is mixed into the raw material and is uniformly distributed in the product, the fluorine gas is generated through decomposition in the high-temperature graphitization process and is combined with impurities for gasification and escapes from the product, the defect that the internal and external purities of the traditional ventilating purification product are different is overcome, and the effect of uniform purification is achieved.
2. The preparation method of the high-purity high-density graphite material comprises the steps of impregnating a primary graphitized product, filling up holes left by gasification escape of volatile components and impurities of the raw material after primary graphitization after impregnation, and further improving the compactness of the product through high-pressure secondary roasting.
3. According to the preparation method of the high-purity high-density graphite material, the fluoride is added into the impregnant, so that the effect of uniformly purifying and impregnating the pitch coke is achieved in the secondary graphitization process, the product is further purified, and the purity of the product is improved while the product is ensured to be densified.
4. The preparation method of the high-purity high-density graphite material has simple and effective process, is particularly suitable for the preparation of the high-purity high-density graphite material, and is suitable for industrial popularization.
Detailed Description
The inventor finds that the purification method of introducing halogen gas such as fluorine, chlorine and the like into the high-purity high-density graphite in the graphitization stage has the following problems: firstly, halogen gas is input from the outside, permeates into the interior from the surface through the open pores of the graphite product, and as the specification of the graphite product is increased, the permeation of the gas in the graphite product is very difficult, so that impurities on the surface and in the product are in gradient distribution, the purity of the product is uneven, and the using effect of the product is seriously affected; secondly, the impurities are gasified at high temperature and the halogen gas and the impurities are combined and gasified to escape, so that the internal pores of the product are enlarged or increased, the compactness of the final product is reduced, and the high-density material is likely to crack and the yield is seriously reduced; in addition, when large-sized graphite products are prepared, because of the impurity removal difficulty problem, in order to ensure the purity of the large-sized products, coke powder with larger grain diameter is generally selected as a raw material to prepare the graphite material, so that the purification effect is improved, and the material compactness is reduced.
In order to solve the problems, the inventor finally provides a preparation method of a high-purity and high-density graphite material through repeated tests and multiple demonstrations, coke powder, asphalt and a primary additive are prepared into materials according to a certain proportion, wherein the primary additive can generate fluorine gas in the products during primary graphitization for removing impurities and purifying the products, and the prepared materials are uniformly mixed; grinding the uniformly mixed materials into fine powder and pressing and forming, and sequentially carrying out primary roasting and primary graphitization on the formed green body; and finally, after the primary graphitized product is impregnated, sequentially carrying out secondary roasting and secondary graphitization to obtain a high-purity high-density graphite product.
The preferable materials and the mixture ratio are as follows: the coke powder is needle coke or asphalt coke, the average particle size is 5-50 mu m, and the mass accounts for 60-80% of the total mass of the material; the asphalt is medium-temperature coal asphalt, and the mass of the asphalt accounts for 20-40% of the total mass of the material; the primary additive is fluoride, and the mass of the primary additive accounts for 0.1-1.0% of the total mass of the material.
To realize the generation of fluorine gas in the product during the primary graphitization by the primary additive, the following scheme can be adopted: the primary additive adopts fluoride, and after fluorine gas is generated by decomposition during graphitization, the boiling point of the residual substance is not higher than the primary graphitization temperature.
In addition, a secondary additive with the mass of 0.1-0.5% of that of the impregnant can be added into the impregnant, the secondary additive is fluoride, the boiling point of the residual substances is not higher than the secondary graphitization temperature after the fluorine gas is generated by decomposition during graphitization, the fluorine gas can be generated inside a product during graphitization by the secondary additive and used for removing impurities and purifying the impregnant and the product, and the purification effect is further improved; in the scheme, the dipping temperature is preferably 200-260 ℃, the dipping time is preferably 2-6 h, the vacuum is pumped before dipping, and the pressure is preferably maintained at 2-5 MPa in the dipping process.
The material mixes preferably and adopts the kneader kneading, and is specific: adding the coke powder and the primary additive, dry-mixing for 10-30 min at 60-120 ℃, adding the asphalt, wet-mixing for 20-40 min at 150-220 ℃.
Further optionally, the primary roasting temperature is 800-1000 ℃, the heating rate is 1-10 ℃/h, and the heat preservation is carried out for 10-20 h at the highest temperature; and high-pressure roasting is preferably adopted for secondary roasting, the pressure is 1.0-3.0 MPa, the maximum temperature is 700-900 ℃, the heating rate is 1-10 ℃/h, the heat preservation is carried out for 10-20 h at the maximum temperature, and the high-pressure roasting is favorable for improving the coking value of the asphalt, so that the product density is further improved.
The fluoride in the primary additive and the secondary additive is preferably metal fluoride, such as one or more of magnesium fluoride, barium fluoride, calcium fluoride, sodium fluoride and the like, the graphitized product is powered on, the fluoride is decomposed in the graphitizing process by utilizing the principle that the metal fluoride is melted at high temperature and decomposed under the passage of current to generate fluorine gas, the fluorine gas is released from the interior of the product, and the product is uniformly purified from inside to outside, so that the introduction of halogen gas such as fluorine, chlorine and the like in the graphitizing stage is avoided, and impurities on the surface and in the product are in gradient distribution, so that the product purity is not uniform.
In a preferred embodiment, the average particle size of the uniformly mixed materials is preferably 10-80 μm, the maximum particle size is not more than 200 μm, the compression molding mode is die pressing or isostatic pressing, the molding pressure is 160-250 MPa, and the pressure maintaining time is 5-30 min.
The primary graphitization and the secondary graphitization can adopt a direct heating method, the graphitization furnace adopts an internal heat series furnace, preferably, the highest temperature of the graphitization furnace and the internal heat series furnace is 2800-3000 ℃, wherein the temperature rising rate of the primary graphitization is 10-60 ℃/h, the heat preservation is carried out for 8-16 h at the highest temperature, and the temperature reduction rate is not more than 90 ℃/h; the temperature rising rate of the secondary graphitization is 10-60 ℃/h, the heat preservation is carried out for 6-15 h at the highest temperature, and the temperature reduction rate is not more than 90 ℃/h.
Example 1:
75 parts of needle coke with the average particle size of 10 mu m, 24.5 parts of medium-temperature coal pitch and 0.5 part of additive magnesium fluoride are prepared according to the parts by weight. And (3) preferentially adding the prepared needle coke and magnesium fluoride into a kneading machine for dry mixing for 20min at a dry mixing temperature of 100 ℃, adding asphalt for wet mixing for 30min at a kneading temperature of 200 ℃, pouring out and cooling after kneading is finished, thus obtaining the kneaded paste.
Grinding the kneaded paste into fine powder with the average particle size of 20 mu m, filling the fine powder into a die, carrying out isostatic pressing for molding at the molding pressure of 220MPa for 15min, and demoulding after molding. And then, carrying out primary roasting on the molded green body, wherein the roasting temperature is 1000 ℃ at the highest temperature, the heating rate is 5 ℃/h, and the heat preservation is carried out for 15h at the highest temperature. Graphitizing after primary roasting, wherein the graphitizing maximum temperature is 3000 ℃, the temperature rising rate is 20 ℃/h, the heat preservation is carried out for 8h at the maximum temperature, and the temperature reduction rate is not more than 90 ℃/h.
And (3) soaking the primary graphitized product in asphalt liquid, adding 0.2% of magnesium fluoride into the soaking liquid, at the soaking temperature of 220 ℃, for 4 hours, vacuumizing before soaking, and under the soaking pressure of 3 MPa.
And (3) carrying out secondary roasting on the dipped product, wherein high-pressure roasting is adopted, the pressure is 2.0MPa, the maximum temperature is 800 ℃, the heating rate is 6 ℃/h, and the heat preservation is carried out for 15h at the maximum temperature. And (3) performing secondary graphitization after roasting, wherein the graphitization maximum temperature is 2900 ℃, the temperature rise rate is 60 ℃/h, the heat preservation is performed for 10h at the maximum temperature, the temperature reduction rate is not more than 90 ℃/h, finally, a high-purity and high-density graphite product is obtained, and the purity and the density of the product are detected by sampling at a plurality of different depths.
Example 2
70 parts of needle coke with the average particle size of 5 mu m, 29 parts of medium-temperature coal pitch and 1.0 part of additive barium fluoride are prepared according to the parts by weight. And (3) preferentially adding the prepared needle coke and magnesium fluoride into a kneading machine for dry mixing for 10min at a dry mixing temperature of 120 ℃, adding asphalt for wet mixing for 40min at a kneading temperature of 220 ℃, pouring out and cooling after kneading is finished, thus obtaining the kneaded paste.
Grinding the kneaded paste into fine powder with the average particle size of 50 mu m, filling the fine powder into a die for isostatic pressing, wherein the forming pressure is 250MPa, the forming time is 10min, and demoulding is finished after the forming. And then, carrying out primary roasting on the molded green body, wherein the roasting temperature is 900 ℃ at the highest temperature, the heating rate is 2 ℃/h, and the heat preservation is carried out for 10h at the highest temperature. Graphitizing after primary roasting, wherein the graphitizing maximum temperature is 3000 ℃, the temperature rising rate is 30 ℃/h, the heat preservation is carried out for 12h at the maximum temperature, and the temperature reduction rate is not more than 90 ℃/h.
And (3) soaking the primary graphitized product in asphalt liquid, adding 0.4% of barium fluoride into the soaking liquid, at the soaking temperature of 240 ℃, for 5 hours, and vacuumizing before soaking under the soaking pressure of 4 MPa.
And (3) carrying out secondary roasting on the dipped product, wherein high-pressure roasting is adopted, the pressure is 3.0MPa, the maximum temperature is 900 ℃, the heating rate is 4 ℃/h, and the heat preservation is carried out for 10h at the maximum temperature. And (3) performing secondary graphitization after roasting, wherein the graphitization highest temperature is 2900 ℃, the temperature rise rate is 30 ℃/h, the heat preservation is performed for 6h at the highest temperature, the temperature reduction rate is not more than 90 ℃/h, and finally, a high-purity and high-density graphite product is obtained, and the purity and the density of the product are detected by sampling at a plurality of different depths.
Example 3
80 parts of needle coke with the average particle size of 50 mu m, 19.6 parts of medium-temperature coal pitch and 0.4 part of additive calcium fluoride are prepared according to the parts by weight. And (3) preferentially adding the prepared needle coke and magnesium fluoride into a kneading machine for dry mixing for 10min at the dry mixing temperature of 100 ℃, adding asphalt for wet mixing for 30min at the kneading temperature of 180 ℃, and pouring out and cooling after kneading to obtain the kneaded paste.
Grinding the kneaded paste into fine powder with the average particle size of 60 mu m, filling the fine powder into a die, carrying out isostatic pressing for molding, wherein the molding pressure is 160MPa, the molding time is 30min, and demoulding is finished after molding. And then, carrying out primary roasting on the molded green body, wherein the roasting temperature is 800 ℃ at the highest temperature, the heating rate is 10 ℃/h, and the heat preservation is carried out for 20h at the highest temperature. Graphitizing after primary roasting, wherein the graphitizing maximum temperature is 2800 ℃, the temperature rising rate is 60 ℃/h, the heat preservation is carried out for 10h at the maximum temperature, and the temperature reduction rate is not more than 90 ℃/h.
And (3) soaking the primary graphitized product in asphalt liquid, adding 0.4% of calcium fluoride into the soaking liquid, at the soaking temperature of 250 ℃, for 6 hours, and vacuumizing before soaking under the soaking pressure of 5 MPa.
And (3) carrying out secondary roasting on the dipped product, wherein high-pressure roasting is adopted, the pressure is 2.0MPa, the highest temperature is 700 ℃, the heating rate is 3 ℃/h, and the heat preservation is carried out for 15h at the highest temperature. And (3) performing secondary graphitization after roasting, wherein the graphitization maximum temperature is 2800 ℃, the temperature rise rate is 10 ℃/h, the heat preservation is performed for 6h at the maximum temperature, the temperature reduction rate is not more than 90 ℃/h, finally, a high-purity and high-density graphite product is obtained, and the purity and the density of the product are detected by sampling at a plurality of different depths.
Example 4
According to the weight portion, 65 portions of needle coke with the average grain size of 30 mu m, 34.4 portions of medium temperature coal tar and 0.6 portion of additive magnesium fluoride are respectively prepared. And (3) preferentially adding the prepared needle coke and sodium fluoride into a kneading machine for dry mixing for 30min at the dry mixing temperature of 100 ℃, adding asphalt for wet mixing for 0min at the kneading temperature of 200 ℃, pouring out and cooling after kneading to obtain the kneaded paste.
And grinding the kneaded paste into fine powder with the average particle size of 80 mu m, filling the fine powder into a die, carrying out isostatic pressing for forming at the forming pressure of 190MPa for 15min, and demoulding after the forming is finished to obtain a large-size green body with the size phi 900 x 1500 mm. And then, carrying out primary roasting on the molded green body, wherein the roasting temperature is 900 ℃ at the highest temperature, the heating rate is 10 ℃/h, and the heat preservation is carried out for 10h at the highest temperature. Graphitizing after primary roasting, wherein the graphitizing maximum temperature is 3000 ℃, the temperature rising rate is 20 ℃/h, the heat preservation is carried out for 8h at the maximum temperature, and the temperature reduction rate is not more than 90 ℃/h.
And (3) soaking the primary graphitized product in asphalt liquid, adding 0.3% of sodium fluoride into the soaking liquid, at the soaking temperature of 210 ℃, for 5 hours, vacuumizing before soaking, and at the soaking pressure of 4 MPa.
And (3) carrying out secondary roasting on the dipped product, wherein high-pressure roasting is adopted, the pressure is 2.5MPa, the maximum temperature is 800 ℃, the heating rate is 6 ℃/h, and the heat preservation is carried out for 8h at the maximum temperature. And after roasting, carrying out secondary graphitization, wherein the graphitization maximum temperature is 3000 ℃, the temperature rise rate is 20 ℃/h, the heat preservation is carried out for 9h at the maximum temperature, the temperature reduction rate is not more than 90 ℃/h, finally obtaining a high-purity high-density graphite product, and sampling and detecting the purity and the density of the product at a plurality of different depths.
Comparative example 1:
the same proportion as that of the example 4 is adopted, the additive is replaced by medium-temperature coal pitch, the same method as that of the example 4 is adopted for kneading, grinding, compression molding, roasting and graphitization, and fluorine gas is continuously introduced for purification by adopting a conventional method in the graphitization process without impregnation, secondary roasting and secondary graphitization; and sampling and detecting the purity and the density of the obtained product at a plurality of different depths.
Comparative example 2:
the same proportion as that of example 4 is adopted, the additive is replaced by medium-temperature coal pitch, the same method as that of example 4 is adopted for kneading, grinding, profiling, roasting, primary graphitization, dipping, secondary roasting and secondary graphitization, and fluorine gas is continuously introduced for purification in the graphitization process by adopting a conventional method; and sampling and detecting the purity and the density of the obtained product at a plurality of different depths.
Comparative example 3
The same proportion as that of example 4 is adopted, the secondary additive is replaced by medium-temperature coal pitch, the same method as that of example 4 is adopted for kneading, grinding, profiling, roasting, primary graphitization, dipping, secondary roasting and secondary graphitization, and fluorine gas is continuously introduced for purification in the secondary graphitization process by adopting a conventional method; and sampling and detecting the purity and the density of the obtained product at a plurality of different depths.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are also included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope defined by the claims.
The present invention is not described in detail, but is known to those skilled in the art.
Claims (10)
1. The preparation method of the high-purity high-density graphite material is characterized by comprising the following steps of:
preparing coke powder, asphalt and a primary additive into materials according to a certain proportion, wherein the primary additive can generate fluorine gas in the products during primary graphitization for removing impurities and purifying the products, and the prepared materials are uniformly mixed;
grinding the uniformly mixed materials into fine powder and pressing and forming, and sequentially carrying out primary roasting and primary graphitization on a formed green body;
and after the primary graphitized product is impregnated, secondary roasting and secondary graphitization are sequentially carried out to obtain a high-purity high-density graphite product.
2. The method for preparing a high-purity high-density graphite material according to claim 1, wherein: the primary additive is fluoride, and after fluorine gas is generated by decomposition during graphitization, the boiling point of the residual substance is not higher than the primary graphitization temperature.
3. The method for preparing a high-purity high-density graphite material according to claim 1, wherein: the coke powder is needle coke or asphalt coke, the average particle size is 5-50 mu m, and the mass accounts for 60-80% of the total mass of the material; the asphalt is medium-temperature coal asphalt, and the mass of the asphalt accounts for 20-40% of the total mass of the material; the primary additive is fluoride, and the mass of the primary additive accounts for 0.1-1.0% of the total mass of the material.
4. The method for preparing a high-purity high-density graphite material according to claim 1, wherein: adding a secondary additive accounting for 0.1-0.5% of the mass of the impregnant into the impregnant, wherein the secondary additive is fluoride, the boiling point of the residual substance is not higher than the secondary graphitization temperature after the secondary additive is decomposed to generate fluorine gas during graphitization, and the secondary additive can generate fluorine gas inside a product during graphitization for removing impurities and purifying the impregnant and the product; the dipping temperature is 200-260 ℃, the dipping time is 2-6 h, the vacuum pumping is carried out before the dipping, and the pressure is maintained at 2-5 MPa in the dipping process.
5. The method for preparing a high-purity high-density graphite material according to claim 1, wherein: the primary graphitization and the secondary graphitization both adopt a direct heating method, and the graphitization furnace adopts an internal heat series furnace with the maximum temperature of 2800-3000 ℃.
6. The method for preparing a high-purity high-density graphite material according to claim 1, wherein: the materials are mixed and kneaded by a kneading machine, the coke powder and the primary additive are firstly added for dry mixing for 10-30 min at the dry mixing temperature of 60-120 ℃, the asphalt is then added for wet mixing for 20-40 min, and the kneading temperature is 150-220 ℃.
7. The method for preparing a high-purity high-density graphite material according to claim 1, wherein: the average particle size of the fine powder is 10-80 mu m, the maximum particle size is not more than 200 mu m, the compression molding mode is mould pressing or isostatic pressing, the molding pressure is 160-250 MPa, and the pressure maintaining time is 5-30 min.
8. The method for preparing a high-purity high-density graphite material according to claim 1, wherein: the primary roasting temperature is 800-1000 ℃, the heating rate is 1-10 ℃/h, and the heat preservation is carried out for 10-20 h at the highest temperature.
9. The method for preparing a high-purity high-density graphite material according to claim 1, wherein: the secondary roasting adopts high-pressure roasting, the pressure is 1.0-3.0 MPa, the maximum temperature is 700-900 ℃, the heating rate is 1-10 ℃/h, and the heat preservation is carried out for 10-20 h at the maximum temperature.
10. The method for producing a high purity and high density graphite material according to any one of claims 2 to 4, wherein: the fluoride is a metal fluoride including but not limited to one or more of magnesium fluoride, barium fluoride, calcium fluoride and sodium fluoride.
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