Purification method of high-volatile cryptocrystalline graphite

Abstract

The invention relates to the technical field of graphite purification, in particular to a purification method of high-volatile cryptocrystalline graphite. The purification method comprises the following steps: pre-roasting, crushing and pelletizing, roasting, grinding, water leaching, acid leaching, washing and drying. In the step of crushing and pelletizing, the cryptocrystalline graphite 1 is ground to be less than 45 microns, and is mixed and stirred with a sodium hydroxide solution with the concentration of 60-70% for 1-2 minutes to obtain cryptocrystalline graphite small-particle spheres; in the step of acid leaching, the cryptocrystalline graphite 3 obtained in the step of water leaching is subjected to acid leaching for 2-3 h under the conditions that the liquid-solid ratio is 14-16 and the acid leaching temperature is 55-65 DEG C, and the cryptocrystalline graphite 4 is obtained. The high-grade cryptocrystalline graphite with the cryptocrystalline graphite content larger than or equal to 99.0% is obtained through the processes of pre-roasting, smashing and pelletizing, roasting, grinding, water leaching and acid leaching by taking the cryptocrystalline graphite with the fixed carbon content of 80-90% as the raw material, no additive is added, the purification cost can be effectively reduced, and the purposes of saving energy and reducing consumption are achieved.

Description

Technical Field

[0001] The present application relates to the technical field of graphite purification, and in particular to a method for purifying high-volatile cryptocrystalline graphite. Background Art

[0002] Graphite has many excellent properties such as high temperature resistance, thermal conductivity, electrical conductivity, chemical stability, lubricity and plasticity. It is widely used in metallurgy, machinery, nuclear industry, aerospace, electronic information, new energy vehicles and other fields. It is an emerging strategic mineral resource. For a long time, people have only paid attention to the mining and processing of crystalline graphite (large crystal size, usually millimeter level or larger), and ignored the development and utilization of cryptocrystalline graphite (the crystal structure is very fine, and it is difficult to observe obvious crystal morphology under the naked eye or ordinary microscope, usually micrometer level or smaller). Cryptocrystalline graphite is mainly used as raw ore and rough processed products. In some places, it is even burned as coal, resulting in a large loss and waste of mineral resources. Therefore, it is of great practical significance to conduct research on the chemical purification of cryptocrystalline graphite.

[0003] In the prior art, the following contents are disclosed regarding the chemical purification of cryptocrystalline graphite:

[0004] (1) The invention patent with publication number CN 108358201 A discloses a method for purifying graphite, wherein cryptocrystalline graphite with a fixed carbon content of 65-73% is used as a raw material, ground to a particle size of less than 45 μm, and then sodium hydroxide, sodium metaborate and water are added. The cryptocrystalline graphite after alkali fusion is subjected to 2-3 h of alkali fusion in a reaction kettle at 150-260° C., and the alkali fused cryptocrystalline graphite is washed to a pH of 7.5-7.8, and sulfuric acid with a volume concentration of 2-5% is added and stirred, and then allowed to stand for 1-1.5 h to obtain high-grade cryptocrystalline graphite with a cryptocrystalline graphite content of ≥99.0%.

[0005] (2) The invention patent with publication number CN 104495797 A discloses a method for purifying natural cryptocrystalline graphite, which comprises taking natural cryptocrystalline graphite as raw material, adding sodium hydroxide, auxiliary agents (sodium metaborate and sodium diisobutylnaphthalene sulfonate) and water, heating at 150-300°C, stirring for 1-2h, washing, filtering and drying to obtain alkali-washed graphite, then adding the alkali-washed graphite, soluble fluoride salt and nitric acid into a reaction container, heating at 60-90°C for 2-6h, washing, precipitating, filtering and drying to obtain graphite with a carbon content of more than 99.90%.

[0006] (3) The invention patent with publication number CN 102502608 A discloses a method for purifying natural cryptocrystalline graphite. Natural cryptocrystalline graphite with a fixed carbon content of 80-85% is used as raw material. Soluble fluoride salt, hydrochloric acid or sulfuric acid is added to a reaction container. After stirring and impregnating at 60-90°C for 5-8h, the mixture is washed, filtered and dried to obtain cryptocrystalline graphite with a carbon content of more than 99%.

[0007] As can be seen from the above, in the purification methods disclosed in the invention patents with publication numbers CN 108358201 A and CN 104495797 A, additives such as sodium metaborate are often needed to be added during alkali melting or alkali washing, which will increase the cost of drugs and the cost of purification. In the purification methods disclosed in the invention patents with publication numbers CN 104495797 A and CN 102502608A, soluble fluoride salts need to be added first during acid leaching, and then hydrochloric acid, sulfuric acid or nitric acid is added for acid leaching. The leaching process will produce hydrofluoric acid or fluoride to pollute the environment. In addition, the volatile matter in cryptocrystalline graphite is relatively high, and there is often 2-3% of volatile matter after acid leaching. Summary of the invention

[0008] The present application provides a method for purifying high-volatile cryptocrystalline graphite.

[0009] The method for purifying cryptocrystalline graphite provided in the present application uses cryptocrystalline graphite with a fixed carbon content of 80-90% as raw material, without adding auxiliary agents, and obtains high-grade cryptocrystalline graphite with an cryptocrystalline graphite content of ≥99.0% through a pre-roasting-crushing ball making (alkali fusion)-roasting-grinding-water leaching-acid leaching process, which can effectively reduce the purification cost and achieve the purpose of energy saving and consumption reduction.

[0010] In the first aspect, the present application provides a method for purifying high-volatile cryptocrystalline graphite, using the following technical solution:

[0011] A method for purifying high-volatile cryptocrystalline graphite, the method comprising the following steps: pre-baking, crushing and balling, baking, grinding, water leaching, acid leaching and washing and drying;

[0012] In the crushing and ball-making step, the cryptocrystalline graphite 1 is ground to less than 45 μm, and mixed with a sodium hydroxide solution with a concentration of 60-70% and stirred for 1-2 minutes to obtain cryptocrystalline graphite small particle spheres; wherein the cryptocrystalline graphite 1 is cryptocrystalline graphite with a fixed carbon content of 80-90%; the weight ratio of the cryptocrystalline graphite 1 to the sodium hydroxide is 1; (0.75-1);

[0013] In the acid leaching step, the cryptocrystalline graphite 3 obtained in the water leaching step is subjected to acid leaching for 2-3 hours at a liquid-to-solid ratio of 14-16 and an acid leaching temperature of 55-65° C. to obtain cryptocrystalline graphite 4; wherein the acid leaching uses a mixed acid obtained by mixing 5% sulfuric acid and 5% hydrochloric acid in a weight ratio of (4-2):1.

[0014] Optionally, in the pre-baking step, the cryptocrystalline graphite is calcined at 750-800° C. for 10-15 min to remove volatiles, thereby obtaining cryptocrystalline graphite 1.

[0015] Optionally, in the calcining step, the cryptocrystalline graphite small particle spheres are calcined at 200-250° C. for 0.5-1.5 h to obtain cryptocrystalline graphite 2.

[0016] Optionally, the cryptocrystalline graphite small particle spheres are placed in a muffle furnace for calcination.

[0017] Optionally, in the grinding step, the cryptocrystalline graphite 2 is ground to less than 45 μm to obtain cryptocrystalline graphite powder.

[0018] In the present application, cryptocrystalline graphite 2 is ground to less than 45 μm to accelerate the dissolution of sodium hydroxide and silicate minerals in water.

[0019] Optionally, in the water immersion step, water is added to the cryptocrystalline graphite powder, and the powder is immersed in water for 1-2 hours and then filtered to obtain cryptocrystalline graphite 3.

[0020] Optionally, the weight ratio of the cryptocrystalline graphite powder to the water is 1:(4-6).

[0021] Optionally, the water immersion temperature is 65-75°C.

[0022] In summary, the present application includes at least one of the following beneficial technical effects:

[0023] (1) The present invention bakes the cryptocrystalline graphite in advance, thereby removing the volatile matter in the cryptocrystalline graphite, enhancing the hydrophilicity of the surface of the cryptocrystalline graphite, making it easier to adsorb the sodium hydroxide solution, and shortening the stirring time.

[0024] (2) When adding sodium hydroxide in the present application, a sodium hydroxide solution is pre-configured. When the cryptocrystalline graphite is mixed with NaOH, the sodium hydroxide is more evenly attached to the surface of the cryptocrystalline graphite and the surface of impurities, thereby reducing the waste of reagents.

[0025] (3) The present application does not add any additives during alkali melting. By preparing cryptocrystalline graphite-NaOH mixed particles, the melting of impurities in the cryptocrystalline graphite is enhanced, and the consumption of the reagent dosage is reduced.

[0026] (4) Use a low concentration mixed acid (volume ratio of sulfuric acid / hydrochloric acid is (4-2):1) to prevent precipitation of iron and aluminum ions during the filtering and washing process.

[0027] (5) The method for purifying cryptocrystalline graphite provided in the present application uses cryptocrystalline graphite with a fixed carbon content of 80-90% as raw material, without adding any additives, and obtains high-grade cryptocrystalline graphite with an cryptocrystalline graphite content of ≥99.0% through a process of pre-roasting - crushing and ball making (alkali fusion) - roasting - grinding - water leaching - acid leaching, which can effectively reduce the purification cost and achieve the purpose of energy saving and consumption reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention provides a flow chart of a method for purifying high-volatile cryptocrystalline graphite. DETAILED DESCRIPTION

[0029] Before describing the embodiments of the present application in detail, it should be understood that the terms used herein are only used for the purpose of describing specific embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by ordinary technicians in the field to which the terms belong.

[0030] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0031] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0032] In the present application, the terms "comprise" or "include" are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0033] The present application provides a method for purifying high-volatile cryptocrystalline graphite. Figure 1 , the purification method specifically comprises the following steps:

[0034] (1) Pre-calcination: calcining the cryptocrystalline graphite at 750-800°C for 10-15 min to remove volatiles to obtain cryptocrystalline graphite 1;

[0035] (2) Grinding and balling: Grinding cryptocrystalline graphite 1 to less than 45 μm, and putting it into a mixer together with a sodium hydroxide solution with a concentration of 60-70%, stirring for 1-2 minutes, to obtain cryptocrystalline graphite small particle spheres; wherein the cryptocrystalline graphite 1 is cryptocrystalline graphite with a fixed carbon content of 80-90%; the weight ratio of cryptocrystalline graphite 1 to sodium hydroxide is 1; (0.75-1);

[0036] (3) Calcination: placing the cryptocrystalline graphite small particle spheres in a muffle furnace and calcining them to obtain cryptocrystalline graphite 2; wherein the calcination time is 0.5-1.5 h and the calcination temperature is 200-250° C.;

[0037] (4) Grinding: Grinding the cryptocrystalline graphite 2 to less than 45 μm to obtain cryptocrystalline graphite powder;

[0038] (5) Water immersion: Add tap water to the cryptocrystalline graphite powder, immerse for 1-2 hours, and then filter to obtain cryptocrystalline graphite 3. The weight ratio of cryptocrystalline graphite powder to water is 1:(4-6), and the immersion temperature is 65-75°C;

[0039] (6) Acid leaching: The cryptocrystalline graphite 3 is acid-leached for 2-3 hours at a liquid-to-solid ratio of 14-16 and an acid leaching temperature of 55-65° C. to obtain cryptocrystalline graphite 4; wherein the acid leaching uses a mixed acid (5% sulfuric acid: 5% hydrochloric acid = (4-2): 1).

[0040] (7) Washing and drying: The cryptocrystalline graphite 4 is filtered, washed and dried to obtain high-grade cryptocrystalline graphite with a fixed carbon content greater than 99%.

[0041] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. The embodiments described below are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present application.

[0042] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0043] The present application is further described in detail below in conjunction with the embodiments and test results.

[0044] Example

[0045] Example 1

[0046] This embodiment provides a method for purifying high-volatile cryptocrystalline graphite.

[0047] The specific steps include:

[0048] (1) Pre-calcination: The cryptocrystalline graphite is calcined at 750°C for 10 min to remove volatiles, thereby obtaining cryptocrystalline graphite 1;

[0049] (2) Grinding and balling: Grind cryptocrystalline graphite 1 to less than 45 μm, and put it into a mixer together with a sodium hydroxide solution with a concentration of 60%, and stir for 1 minute to obtain cryptocrystalline graphite small particle balls; wherein the cryptocrystalline graphite 1 is cryptocrystalline graphite with a fixed carbon content of 82%; the weight ratio of cryptocrystalline graphite 1 to sodium hydroxide is 1:0.75;

[0050] (3) Calcination: Place the cryptocrystalline graphite small particle spheres in a muffle furnace and calcine to obtain cryptocrystalline graphite 2; wherein the calcination time is 0.5 h and the calcination temperature is 250° C.;

[0051] (4) Grinding: Grinding the cryptocrystalline graphite 2 to less than 45 μm to obtain cryptocrystalline graphite powder;

[0052] (5) Water immersion: Add tap water to the cryptocrystalline graphite powder, immerse it in water for 1 hour, and then filter it to obtain cryptocrystalline graphite 3. The weight ratio of cryptocrystalline graphite powder to water is 1:5, and the immersion temperature is 70°C;

[0053] (6) Acid leaching: The cryptocrystalline graphite 3 was acid-leached for 2.5 h at a liquid-to-solid ratio of 15 and an acid leaching temperature of 60° C. to obtain cryptocrystalline graphite 4; wherein the acid leaching used a mixed acid (5% sulfuric acid: 5% hydrochloric acid = 4:1).

[0054] (7) Washing and drying: The cryptocrystalline graphite 4 is filtered, washed and dried to obtain high-grade cryptocrystalline graphite with a fixed carbon content greater than 99.34%.

[0055] Example 2

[0056] This embodiment provides a method for purifying high-volatile cryptocrystalline graphite. The difference between this embodiment and embodiment 1 is that the weight ratio of cryptocrystalline graphite 1 to sodium hydroxide is 1:1.

[0057] The specific steps include:

[0058] (1) Pre-calcination: The cryptocrystalline graphite is calcined at 750°C for 10 min to remove volatiles, thereby obtaining cryptocrystalline graphite 1;

[0059] (2) Grinding and balling: Grinding cryptocrystalline graphite 1 to less than 45 μm, and putting it into a mixer together with a sodium hydroxide solution with a concentration of 60%, stirring for 1 minute, to obtain cryptocrystalline graphite small particle balls; wherein the cryptocrystalline graphite 1 is cryptocrystalline graphite with a fixed carbon content of 82%; the weight ratio of cryptocrystalline graphite 1 to sodium hydroxide is 1:1;

[0060] (3) Calcination: Place the cryptocrystalline graphite small particle spheres in a muffle furnace and calcine to obtain cryptocrystalline graphite 2; wherein the calcination time is 0.5 h and the calcination temperature is 250° C.;

[0061] (4) Grinding: Grinding the cryptocrystalline graphite 2 to less than 45 μm to obtain cryptocrystalline graphite powder;

[0062] (5) Water immersion: Add tap water to the cryptocrystalline graphite powder, immerse it in water for 1 hour, and then filter it to obtain cryptocrystalline graphite 3. The weight ratio of cryptocrystalline graphite powder to water is 1:5, and the immersion temperature is 70°C;

[0063] (6) Acid leaching: The cryptocrystalline graphite 3 was acid-leached for 2.5 h at a liquid-to-solid ratio of 15 and an acid leaching temperature of 60° C. to obtain cryptocrystalline graphite 4; wherein the acid leaching used a mixed acid (5% sulfuric acid: 5% hydrochloric acid = 4:1).

[0064] (7) Washing and drying: The cryptocrystalline graphite 4 is filtered, washed and dried to obtain high-grade cryptocrystalline graphite with a fixed carbon content greater than 99.44%.

[0065] Example 3

[0066] This embodiment provides a method for purifying high-volatile cryptocrystalline graphite. The difference between this embodiment and embodiment 1 is that the concentration of the sodium hydroxide solution is 70%.

[0067] The specific steps include:

[0068] (1) Pre-calcination: The cryptocrystalline graphite is calcined at 750°C for 10 min to remove volatiles, thereby obtaining cryptocrystalline graphite 1;

[0069] (2) Grinding and balling: Grind cryptocrystalline graphite 1 to less than 45 μm, and put it into a mixer together with a sodium hydroxide solution with a concentration of 70%, and stir for 1 minute to obtain cryptocrystalline graphite small particle balls; wherein the cryptocrystalline graphite 1 is cryptocrystalline graphite with a fixed carbon content of 82%; the weight ratio of cryptocrystalline graphite 1 to sodium hydroxide is 1:0.75;

[0070] (3) Calcination: Place the cryptocrystalline graphite small particle spheres in a muffle furnace and calcine to obtain cryptocrystalline graphite 2; wherein the calcination time is 0.5 h and the calcination temperature is 250° C.;

[0071] (4) Grinding: Grinding the cryptocrystalline graphite 2 to less than 45 μm to obtain cryptocrystalline graphite powder;

[0072] (5) Water immersion: Add tap water to the cryptocrystalline graphite powder, immerse it in water for 1 hour, and then filter it to obtain cryptocrystalline graphite 3. The weight ratio of cryptocrystalline graphite powder to water is 1:5, and the immersion temperature is 70°C;

[0073] (6) Acid leaching: The cryptocrystalline graphite 3 was acid-leached for 2.5 h at a liquid-to-solid ratio of 15 and an acid leaching temperature of 60° C. to obtain cryptocrystalline graphite 4; wherein the acid leaching used a mixed acid (5% sulfuric acid: 5% hydrochloric acid = 4:1).

[0074] (7) Washing and drying: The cryptocrystalline graphite 4 is filtered, washed and dried to obtain high-grade cryptocrystalline graphite with a fixed carbon content greater than 99.51%.

[0075] From the above, it can be seen that the method for purifying cryptocrystalline graphite provided in the present application uses cryptocrystalline graphite with a fixed carbon content of 80-90% as raw material, without adding auxiliary agents, and obtains high-grade cryptocrystalline graphite with an cryptocrystalline graphite content of ≥99.0% through a pre-calcination-crushing ball-making-calcination-grinding-water leaching-acid leaching process, which can effectively reduce the purification cost and achieve the purpose of energy saving and consumption reduction.

[0076] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for purifying high-volatile cryptocrystalline graphite, characterized in that: The purification method specifically comprises the following steps: pre-roasting, crushing and balling, roasting, grinding, water leaching, acid leaching and washing and drying; In the crushing and ball-making step, the cryptocrystalline graphite 1 is ground to less than 45 μm, and mixed with a sodium hydroxide solution with a concentration of 60-70% and stirred for 1-2 minutes to obtain cryptocrystalline graphite small particle spheres; wherein the cryptocrystalline graphite 1 is cryptocrystalline graphite with a fixed carbon content of 80-90%; the weight ratio of the cryptocrystalline graphite 1 to the sodium hydroxide is 1; (0.75-1); In the acid leaching step, the cryptocrystalline graphite 3 obtained in the water leaching step is subjected to acid leaching for 2-3 hours at a liquid-to-solid ratio of 14-16 and an acid leaching temperature of 55-65° C. to obtain cryptocrystalline graphite 4; wherein the acid leaching uses a mixed acid obtained by mixing 5% sulfuric acid and 5% hydrochloric acid in a weight ratio of (4-2):

1.

2. The purification method according to claim 1, characterized in that In the pre-baking step, the cryptocrystalline graphite is placed in an environment of 750-800° C. and baked for 10-15 minutes to remove volatiles, thereby obtaining cryptocrystalline graphite 1.

3. The purification method according to claim 1, characterized in that In the calcining step, the cryptocrystalline graphite small particle spheres are placed in an environment of 200-250° C. and calcined for 0.5-1.5 h to obtain cryptocrystalline graphite 2.

4. The purification method according to claim 3, characterized in that The cryptocrystalline graphite small particle spheres are placed in a muffle furnace for calcination.

5. The purification method according to claim 3, characterized in that: In the grinding step, the cryptocrystalline graphite 2 is ground to less than 45 μm to obtain cryptocrystalline graphite powder.

6. The purification method according to claim 5, characterized in that In the water immersion step, water is added to the cryptocrystalline graphite powder, and the powder is immersed in water for 1-2 hours and then filtered to obtain cryptocrystalline graphite 3.

7. The purification method according to claim 6, characterized in that: The weight ratio of the cryptocrystalline graphite powder to the water is 1:(4-6).

8. The purification method according to claim 6, characterized in that: The water immersion temperature is 65-75°C.

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