Application of Tectonic Coal in the Preparation of Coal-based Graphite

Abstract

The present invention discloses an application of structural coal in the preparation of coal-based graphite, belonging to the field of structural coal application technology. It overcomes the technical prejudice in the prior art that various levels of bituminous coal have always been considered as non-graphitizable carbon. The application of structural coal in the preparation of coal-based graphite of the present invention is to first crush the structural coal, then grind and screen the obtained structural coal particles, and then deash the obtained structural coal powder. Finally, under vacuum conditions, the deashed structural coal powder is graphitized to obtain coal-based graphite, wherein the coal body structure type of the structural coal meets: any one or more of granular structural coal and mylonitic structural coal; the microscopic deformation degree of the structural coal meets: any one or more of brittle-ductile transition deformation and ductile deformation. The present invention realizes the direct graphitization of bituminous coal, which is considered as non-graphitizable carbon, without adding a catalyst, and expands the carbonaceous source and preparation method of coal-based graphite materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of tectonic coal application, and in particular relates to the application of tectonic coal in the preparation of coal-based graphite. Background Art

[0002] Graphite, a high-energy crystalline carbon material, possesses excellent properties such as high-temperature resistance, thermal shock resistance, electrical conductivity, lubricity, chemical stability, and plasticity. It is widely used in industries such as metallurgy, machinery, electrical engineering, chemical engineering, and defense. Natural graphite concentrate products remain expensive, so the search for alternative carbonaceous raw materials with broad availability, low cost, and high purity to produce high-quality artificial graphite has been a key research topic in the industry. my country boasts abundant coal reserves, a wide variety of coal types, and low cost. Anthracite, in particular, possesses abundant aromatic layers composed of parallel stacks of polycyclic aromatic hydrocarbons with distinct orientation, and naturally exhibits varying degrees of graphitization. However, not all anthracites yield high-quality graphite after pyrolysis at temperatures exceeding 2000°C in an airless environment. Some anthracites only produce disordered porous carbon or turbo-lamellar carbon even at 3000°C. Mechanistically, graphitizable anthracite has the unique property of nanoscale pore flattening (Oberlin A, Terriere G. Graphitization studies of anthracites by high resolution electron microscopy [J]. Carbon, 1975, 13 (5): 367-376.). High temperature conditions further cause the nanoscale micropores and ultramicropores of this type of anthracite to collapse, the pore spacing to shrink and disappear, the aromatic interlamellar spacing to decrease, and the aromatic structure to condense and eventually evolve into graphite. This typical characteristic of anthracite is believed to be the result of rock static pressure or tectonic stress promoting coal quality evolution (Blanche C, Rouzaud J, Dumas D. New data on anthracite graphitizibility [C]. American Carbon Society, 22 nd Currently, my country primarily uses this type of anthracite to produce coal-based graphite. However, anthracite is a scarce resource in China, and the mining of high-quality anthracite is restricted. Therefore, it is crucial to explore the use of other types of coal to produce coal-based graphite.

[0003] Bituminous coal is less metamorphic than anthracite and comes in many varieties. Its microstructure is porous and disordered, and the organic carbon in the coal is connected by a large number of different bridge bonds to form a three-dimensional structure, which inhibits the orderly arrangement of aromatic sheets. Therefore, bituminous coal of various metamorphic degrees has always been considered non-graphitizable carbon. However, in order to expand the high-value-added utilization of bituminous coal, some scholars are also trying to use special processes to prepare graphite from some special bituminous coals. For example, Chinese invention patent application number CN201410209453.5 discloses a method for graphitizing bituminous coal and its coal rock components. This method pulverizes Shenfu coal (high-volatile bituminous coal, metamorphic to fat coal) and its coal rock components, mixes them with a catalyst of ferric chloride or boric acid, and graphitizes them at a temperature between 2400°C and 2600°C, obtaining a graphitized product with a graphitization degree of not less than 75%. However, this method requires a higher graphitization temperature, and the prepared coal-based graphite contains more residual inorganic impurities. Currently, only this special bituminous coal meets the applicable conditions, and bituminous coal of other metamorphic degrees cannot be used to directly prepare graphite.

[0004] Tectonic coal is a type of coal that has been subjected to intense geological tectonic stress, compression and shearing, and has undergone significant changes in its primary structure, pore structure and macromolecular structure (Ju Yiwen, Jiang Bo, Hou Quanlin, et al. Relationship between nano-scale deformation of coal rock structure and metamorphic deformation environment [J]. Science Bulletin, 2005, 50(17): 1884-1892.). It is widely developed in coal-bearing strata in my country (Ju Yiwen, Li Xiaoshi. New progress in the study of tectonic coal ultrastructure [J]. Progress in Natural Science, 2009, 19(2): 131-140.). Coal of different metamorphic degrees, such as high-volatile bituminous coal, medium-volatile bituminous coal, low-volatile bituminous coal, and anthracite, can all develop into tectonic coal. In contrast, coal that has not been damaged or has been slightly damaged and still retains its original structure is called primary structural coal (Zhang Xiaobing, Wang Wei, Zhang Yugui, et al. Discussion on the mechanism of oriented growth of microcrystals in tectonic coal [J]. Journal of China Coal Society, 2016, 41(3):712-718.). Tectonic coal and primary structural coal are always layered or interlayered. The typical characteristics of tectonic coal are that the nano-scale pores are highly compressed and the organic macromolecular structure evolves into the graphite stage in advance (Ju Yiwen, Lin Hong, Li Xiaoshi, et al. Tectonic deformation and dynamic metamorphism of coal rocks [J]. Earth Science Frontiers, 2009, 16(1):158-166.). Based on the structural changes caused by shear stress, tectonic coal can be divided into three series and ten categories at the microscopic deformation level: brittle deformation (including broken coal, broken spot coal, broken granular coal, broken pulverized coal, flaky coal and thin coal), brittle-ductile transition (including scaly coal) and ductile deformation (including wrinkled coal, mylonitic coal and heterogeneous structural coal) (Ju Yiwen, Jiang Bo, Hou Quanlin, et al. A new classification of tectonic coal structure-genesis and its geological significance [J]. Journal of China Coal Society, 2004, 29(5): 513-517.). Researchers have conducted a lot of research on tectonic coal, but no research reports on the preparation of coal-based graphite from tectonic coal have been found. This may be because the vast majority of tectonic coal is bituminous coal at a metamorphic level, and bituminous coal has always been considered to be non-graphitizable carbon. In addition, due to the superposition of different degrees of deformation, the organic structure and pore structure of tectonic coal are extremely complex. Therefore, research on the graphitization of tectonic coal is still a blank. Summary of the Invention

[0005] This invention overcomes the prior art bias that various degrees of metamorphic bituminous coal have long been considered non-graphitizable carbon. It provides the use of tectonic coal in the production of coal-based graphite. This application utilizes tectonic coal with microdeformation levels reaching the brittle-ductile transition or ductile deformation level as raw material. This allows direct graphitization of bituminous coal, previously considered non-graphitizable carbon, without the addition of a catalyst. This contributes to the high added value and graded, quality-based utilization of coal resources, particularly bituminous coal, reducing industrial costs and expanding the carbonaceous sources and production pathways for coal-based graphite materials.

[0006] The technical solutions adopted by the present invention to solve the above technical problems are as follows.

[0007] The present invention provides an application of tectonic coal in preparing coal-based graphite, comprising the following steps:

[0008] Step 1: crushing the tectonic coal to obtain tectonic coal particles;

[0009] Step 2: crushing and screening the tectonic coal particles to obtain tectonic coal powder;

[0010] Step 3: Deashing the tectonic coal powder to obtain deashed tectonic coal powder;

[0011] Step 4: graphitizing the deashed structural coal powder under vacuum conditions to obtain coal-based graphite;

[0012] The coal body structure type of the tectonic coal satisfies any one or more of the following: crushed-grained coal, mylonitic coal, etc.

[0013] The microscopic deformation degree of the tectonic coal satisfies any one or more of brittle-ductile transition deformation and ductile deformation;

[0014] The graphitization treatment includes a vacuum carbonization process and a vacuum graphitization process; the treatment temperature of the vacuum carbonization process is 1000-1800° C. and the treatment time is 0.5-1.0 h; the treatment temperature of the vacuum graphitization process is 1800-3000° C. and the treatment time is 1.5-4.0 h.

[0015] Preferably, in step 1, the coal body structure type of the tectonic coal complies with any one or more of the crushed-grained structure coal and mylonitic structure coal specified in the national standard GB / T30050-2013.

[0016] Preferably, in step 1, the metamorphic degree of the tectonic coal satisfies any one or more of medium volatile bituminous coal, low volatile bituminous coal, semi-anthracite coal, and anthracite, and the maximum reflectance of the vitrinite (R o,max )≥1.1%.

[0017] Preferably, in step 1, the organic element content of the tectonic coal satisfies: organic sulfur element content (S o，daf )<1%.

[0018] Preferably, in step one, the tectonic coal is crushed to a particle size of ≤3 mm to obtain tectonic coal particles.

[0019] Preferably, in step 2, the tectonic coal particles are crushed and sieved through a sieve with a pore size of ≤75 μm to obtain tectonic coal powder with a particle size of ≤75 μm.

[0020] Preferably, in step 1, the crushing is performed by a crusher or manually, and the crusher is any one of a jaw crusher, a hammer crusher, and a roller crusher.

[0021] Preferably, in step 2, the pulverization is performed by a pulverizer or manually, and the pulverizer is any one of a steel rod mill, a steel ball mill, and a sealed grinder.

[0022] Preferably, in step 2, the screening uses a standard square hole sieve, and the screening is performed by a screening machine or manual screening.

[0023] Preferably, in step three, the deashing process is: soaking the tectonic coal powder in a hydrochloric acid solution for more than 24 hours at a temperature below 60°C, and filtering out the hydrochloric acid solution; then soaking the tectonic coal powder in a hydrofluoric acid solution for more than 24 hours at a temperature below 60°C, and filtering out the hydrofluoric acid solution; washing with deionized water to a pH of 7, and finally vacuum drying at a temperature below 60°C for more than 24 hours to obtain the deashed tectonic coal powder.

[0024] More preferably, the ratio of the tectonic coal powder, hydrochloric acid solution and hydrofluoric acid solution is 10-15 g: 70-90 ml: 70-90 ml, the concentration of the hydrochloric acid solution is 4-6 mol / L, and the concentration of the hydrofluoric acid solution is 30-50 wt%.

[0025] It is particularly preferred that the ratio of the tectonic coal powder, hydrochloric acid solution and hydrofluoric acid solution is 10-15 g:80 ml:80 ml, the concentration of the hydrochloric acid solution is 5 mol / L, and the concentration of the hydrofluoric acid solution is 40 wt%.

[0026] More preferably, the vacuum drying equipment is a vacuum drying oven.

[0027] Preferably, in step 4, the equipment used for the graphitization treatment is a graphitization furnace.

[0028] The principle of the present invention is that it has been confirmed in the laboratory that shear stress can provide strain energy for further flattening of coal pores, promote the connection of adjacent pores and the parallelization of aromatic sheets through pore aggregation and pore wall rupture, thereby promoting the directional extension and stacking of aromatic sheets and accelerating the development of graphitization (Noda T, Kato H. Heat treatment of carbon under high pressure. Carbon, 1965, 3 (3): 289-290, IN11, 291-297.) (Bustin RM, Ross JV, Rouzaud J N. Mechanisms of graphite formation from kerogen: experimental evidence [J]. International Journal of Coal Geology, 1995, 28 (1): 1-36.). However, this requires additional high temperature conditions of at least 600 ° C in the laboratory. However, for industrial large-scale production of coal-based graphite, it is not realistic to apply a high temperature of 600 ° C and shear stress to all coal raw materials in advance for a period of time and then carry out graphitization treatment. Considering the natural extrusion and shearing characteristics of tectonic coal, which is subjected to geological tectonic stress, not only are its nanoscale pores highly compressed during this process, but tectonic deformation also generates frictional heat within the coal body and on fracture surfaces, providing thermal energy and a high-temperature environment for the advanced evolution of the tectonic coal's macromolecular structure. Based on this fact, the present invention directly produces tectonic coal-based graphite by collecting tectonic coal of varying degrees of metamorphism and deformation and utilizing the naturally flattened nanoscale pores of tectonic coal without the addition of a catalyst.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. Based on extensive research on the pore structure, macromolecular structure, and aromatic structure of tectonic coal, the present invention uses tectonic coal of different metamorphic and deformation degrees stripped from coal seams as raw materials, explores the effects of metamorphism, deformation, and temperature on the high-temperature graphitization of tectonic coal, and focuses on achieving direct graphitization of bituminous coal, which is considered to be non-graphitizable carbon, without adding a catalyst. A new technology for preparing high-quality graphite powder from tectonic coal without adding a catalyst has been developed, providing new possibilities for the high added value and graded and quality-based utilization of coal resources, especially bituminous coal, and expanding the carbon sources and preparation methods of coal-based graphite materials.

[0031] 2. The present invention does not require the addition of a catalyst and fully utilizes the flattened pore structure characteristics of tectonic coal to achieve autonomous graphitization transformation under high temperature conditions. The prepared coal-based graphite does not contain impurities, and the industrial cost is significantly reduced.

[0032] Graphitization is a highly energy-intensive process, consuming up to 15,000 kWh of electricity per ton of graphitization capacity. This invention, based on the principle that geological shear stress reduces the graphitization temperature, achieves a minimum graphitization temperature of tectonic coal of only 1800°C without the addition of a catalyst. This temperature is even lower than the minimum graphitization temperature of conventional anthracite with the addition of a catalyst, significantly reducing energy consumption, costs, and increasing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 These are the macroscopic and microscopic deformation characteristics of the ductile deformed coal (mylonitic coal) and ductile deformed coal (wrinkled coal) of fat coal grades 1 to 2 in Examples 1 and 2 of the present invention.

[0035] Figure 2 These are the macroscopic and microscopic deformation characteristics of the ductile deformation coal (mylonitic coal) and the brittle-ductile transition coal (flake coal) of coking coal grade 3 to 4 in Examples of the present invention.

[0036] Figure 3 These are the macroscopic and microscopic deformation characteristics of the ductile deformation coal (mylonitic coal) and the brittle-ductile transition coal (scaly coal) of the lean coal grades 5 to 6 of Examples 5 and 6 of the present invention.

[0037] Figure 4 These are the macroscopic and microscopic deformation characteristics of the ductile deformation coal (mylonitic coal) and the brittle-ductile transition coal (flake coal) of the anthracite in Examples 7 to 8 of the present invention.

[0038] Figure 5 This is the XRD spectrum of the ductile deformed coal (mylonitic coal) and ductile deformed coal (wrinkled coal) of the fat coal grade in Examples 1 and 2 of the present invention after high-temperature graphitization at 2500°C.

[0039] Figure 6 This is the XRD spectrum of the ductile deformed coal (mylonite coal) and brittle ductile transition coal (flake coal) of coking coal grade 3 to 4 of Examples of the present invention after high-temperature graphitization at 2500°C.

[0040] Figure 7 This is the XRD spectrum of the ductile deformed coal (mylonite coal) and brittle ductile transition coal (flake coal) of the lean coal grade in Examples 5 to 6 of the present invention after high-temperature graphitization at 2500°C.

[0041] Figure 8These are the XRD spectra of the ductile deformed coal (mylonite coal) of the anthracite in Examples 7, 9, and 10 of the present invention after high-temperature graphitization at 2500°C, 1800°C, and 2800°C, as well as the XRD spectrum of the brittle and ductile transition coal (flake coal) of the anthracite in Example 8 after high-temperature graphitization at 2500°C. DETAILED DESCRIPTION

[0042] In order to further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0043] The application of the structural coal of the present invention in preparing coal-based graphite comprises the following steps:

[0044] Step 1: crushing the tectonic coal to obtain tectonic coal particles;

[0045] Step 2: crushing and screening the tectonic coal particles to obtain tectonic coal powder;

[0046] Step 3: Deashing the tectonic coal powder to obtain deashed tectonic coal powder;

[0047] Step 4: Under vacuum conditions, graphitize the deashed structural coal powder to obtain coal-based graphite.

[0048] In the above technical solution, in step 1, the tectonic coal is the tectonic coal collected from the tectonic coal development part of the coal seam according to the national standard GB / T482-2008. Specifically, the deformation degree of the tectonic coal meets any one or more of the following: brittle-ductile transition deformation (including flaky coal), ductile deformation (including crumpled coal, mylonitic coal and heterogeneous structural coal). The metamorphic degree of the tectonic coal meets any one or more of the following: medium-volatile bituminous coal (fat coal with volatile matter ≤30% daf), low-volatile bituminous coal (fat coal, coking coal with volatile matter ≤22% daf), semi-anthracite (lean coal, poor coal), and anthracite, and the metamorphic degree of the tectonic coal also needs to meet the following: the maximum reflectance R of the vitrinite o,max ≥1.1%. The organic element content of tectonic coal meets the following requirements: organic sulfur element content (S o，daf )<1%.

[0049] In the above technical solution, in step 1, the tectonic coal is preferably first crushed to a particle size of ≤3 mm to obtain tectonic coal particles. Crushing is performed using a crusher or manual crushing. The crusher is preferably a jaw crusher, a hammer crusher, or a double-roll crusher. However, it should be noted that other crushers known to those skilled in the art are also suitable for use in the present invention.

[0050] In the above technical solution, in step 2, the structural coal particles are preferably crushed and sieved through a sieve with a pore size of ≤75μm, and the obtained structural coal powder particle size satisfies: D95≤75μm. The crushing is performed by a crusher or manual crushing, and the crusher is preferably any one of a steel rod mill, a steel ball mill, and a sealed grinder; however, it should be noted that other grinders well known to those skilled in the art are also applicable to the present invention. A standard square hole sieve is used for screening, and screening is performed by a screening machine or manual screening. However, it should be noted that other screening equipment well known to those skilled in the art are also applicable to the present invention.

[0051] In the above technical solution, in step 2, the deashing process is preferably as follows: immersing the coal powder in a hydrochloric acid solution for more than 24 hours at a temperature below 60°C, and filtering out the hydrochloric acid solution; then immersing the coal powder in a hydrofluoric acid solution for more than 24 hours at a temperature below 60°C, and filtering out the hydrofluoric acid solution; washing with deionized water until the pH is 7, and finally vacuum drying at a temperature below 60°C for more than 24 hours to obtain the deashed structural coal powder. The ratio of coal powder, hydrochloric acid solution, and hydrofluoric acid solution is preferably 10-15 g: 70-90 ml: 70-90 ml, more preferably 10-15 g: 80 ml: 80 ml, the concentration of the hydrochloric acid solution is preferably 4-6 mol / L, more preferably 5 mol / L, and the concentration of the hydrofluoric acid solution is preferably 30-50 wt%, more preferably 40 wt%. The vacuum drying equipment is preferably a vacuum drying oven. However, it should be noted that other vacuum drying equipment well known to those skilled in the art is also applicable to the present invention.

[0052] In the above technical solution, in step three, the graphitization treatment includes a vacuum carbonization process and a vacuum graphitization process; the treatment temperature of the vacuum carbonization process is 1000-1800°C, and the treatment time is 0.5-1.0h; the treatment temperature of the vacuum graphitization process is 1800-3000°C, and the treatment time is 1.5h-4.0h.

[0053] In the above technical solution, in step 3, the equipment used is a graphitization furnace, and the graphitization degree of the obtained graphite is not less than 70%.

[0054] The terms used in the present invention generally have the meanings commonly understood by those skilled in the art, unless otherwise specified. In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the embodiments.

[0055] In the following examples, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, devices, instruments, equipment, etc. used in the following examples can be obtained from commercial sources.

[0056] The present invention is further described below with reference to the examples.

[0057] Example 1

[0058] Step 1: Select the fat coal-grade tectonic coal development site 1 meter away from the fault plane in the footwall of the ZF3 reverse fault in the No. 10 coal seam of Zhuxianzhuang Mine in Huaibei Coalfield, and sample the mylonitic coal that has reached the ductile deformation level according to the national standard GB / T482-2008 (sample number FM).

[0059] Step 2: Use a jaw crusher to crush the collected fat coal-grade mylonitic coal into coal particles with a particle size of less than 3 mm;

[0060] Step 3: Grind the coal particles in a planetary ball mill for 60 seconds to obtain coal powder;

[0061] Step 4: Using a standard square hole sieve with a sieve aperture of 0.0750 mm, the pulverized coal prepared in step 3 is sieved using a vibrating sieve machine to obtain pulverized coal with a particle size satisfying D99 ≤ 75 μm;

[0062] Step 5: Soak the sieved coal powder prepared in step 4 in a hydrochloric acid solution at a temperature below 60° C. for 24 hours, and filter out the hydrochloric acid solution; then soak the coal powder in a hydrofluoric acid solution at a temperature below 60° C. for 24 hours, and filter out the hydrofluoric acid solution; wash with deionized water until the pH value is 7, and finally vacuum dry at 60° C. for 24 hours to obtain deashed structural coal powder;

[0063] The ratio of coal powder, hydrochloric acid solution and hydrofluoric acid solution is preferably 15 g:80 ml:80 ml, the concentration of hydrochloric acid solution is 5 mol / L, and the concentration of hydrofluoric acid solution is 40 wt %. The vacuum drying equipment is preferably a vacuum drying oven;

[0064] Step 6: Using a medium frequency induction graphitization furnace, the deashed coal powder prepared in step 5 is graphitized (vacuum carbonization process and vacuum graphitization process) under vacuum conditions to obtain coal-based graphite, wherein the treatment temperature of the vacuum carbonization process is 1000°C and the treatment time is 1.0h; the treatment temperature of the vacuum graphitization process is 2500°C and the treatment time is 3h.

[0065] Example 2

[0066] The only difference between this example and Example 1 is that in step 1, a location with rich tectonic coal development was selected, located 2.4 meters from the fault plane in the footwall of the ZF3 reverse fault in the No. 10 coal seam of the Zhuxianzhuang Mine in the Huaibei Coalfield. Crumpled coal reaching the ductile deformation level was sampled (sample number FR) in accordance with the national standard GB / T482-2008. All other aspects were the same as in Example 1.

[0067] Example 3

[0068] The only difference between this embodiment and embodiment 1 is that: in step 1, eight mines in Pingdingshan mining area are selected. 15 The coking coal grade structural coal was developed at the location of the Renzhuang fault 0.8 meters away from the fault plane. Mylonitic coal reaching the ductile deformation level was sampled according to the national standard GB / T482-2008 (sample number JM). Other parts were the same as in Example 1.

[0069] Example 4

[0070] The only difference between this embodiment and embodiment 3 is that: in step 1, eight mines in Pingdingshan mining area are selected. 15 The tectonic coal of coking coal grade was developed at the fault plane 2.4 meters away from the fault plane of the coal seam Renzhuang. According to the national standard GB / T482-2008, the scale coal with the deformation degree reaching the brittle-ductile transition deformation was sampled (sample number JL). Other parts are the same as those in Example 3.

[0071] Example 5

[0072] The only difference between this embodiment and Example 1 is that in step 1, a region of poor-grade structural coal development located 0.5 meters from the fault plane on the F29 hanging wall of the No. 21 coal seam in the Yi'an Mine of the Xin'an Coalfield was selected. Mylonitic coal reaching the ductile deformation level was sampled (sample number PM) in accordance with the national standard GB / T482-2008. All other aspects were the same as in Example 1.

[0073] Example 6

[0074] The only difference between this embodiment and Example 5 is that in step 1, a location with a rich, lean, tectonic coal was selected from the F29 fault hanging wall of the No. 21 coal seam in the Yi'an Mine, Xin'an Coalfield, 2.0 meters from the fault plane. Scaling coal reaching the brittle-to-ductile transition deformation level was sampled (sample number PL) in accordance with national standard GB / T482-2008. All other aspects are the same as in Example 5.

[0075] Example 7

[0076] The only difference between this example and Example 1 is that in step 1, an anthracite-grade tectonic coal development site located 0.5 meters from the fault plane in the footwall of the F1 reverse fault in the No. 5 coal seam of the Baichong Coal Mine in the Hanpo'ao mining area was selected. Mylonitic coal reaching the ductile deformation level (sample number WM-25) was sampled in accordance with the national standard GB / T482-2008. All other aspects are the same as in Example 1.

[0077] Example 8

[0078] The only difference between this embodiment and Example 7 is that in step 1, an anthracite-grade tectonic coal development site located 2.2 meters from the fault plane in the footwall of the F1 reverse fault in the No. 5 coal seam of the Xiaofalu Coal Mine was selected. Scaly coal reaching the brittle-to-ductile transition deformation level was sampled (sample number WL) in accordance with the national standard GB / T482-2008. All other aspects are the same as in Example 7.

[0079] Example 9

[0080] The only difference between this embodiment and embodiment 7 is that in step 6, the deashed pulverized coal prepared in step 5 is graphitized under vacuum conditions using a medium-frequency induction graphitization furnace (vacuum carbonization process and vacuum graphitization process). The vacuum carbonization process is performed at a temperature of 1000°C for 1.0 h; the vacuum graphitization process is performed at a temperature of 1800°C for 3 h (sample number WM-18). All other aspects are the same as those of embodiment 7.

[0081] Example 10

[0082] The only difference between this embodiment and embodiment 7 is that in step 6, the deashed pulverized coal prepared in step 5 is graphitized under vacuum conditions using a medium-frequency induction graphitization furnace (vacuum carbonization process and vacuum graphitization process). The vacuum carbonization process is performed at a temperature of 1000°C for 1.0 h; the vacuum graphitization process is performed at a temperature of 2800°C for 3 h (sample number WM-28). All other aspects are the same as those of embodiment 7.

[0083] The following research and analysis are conducted on the application of the above-mentioned structural coal in the preparation of coal-based graphite.

[0084] (1) Morphological characteristics of tectonic coal:

[0085] The metamorphic deformation degrees of the tectonic coal used in Examples 1 to 10 of the present invention are fat coal (mylonitc coal), fat coal (wrinkled coal), coking coal (mylonitc coal), coking coal (flake coal), lean coal (mylonitc coal), lean coal (flake coal), anthracite (mylonitc coal), anthracite (flake coal), anthracite (mylonitc coal), and anthracite (mylonitc coal), respectively. Figures 1 to 4 The following are the macroscopic appearance and microscopic optical microscope photos of the coal samples used in Examples 1 to 10 respectively. Figures 1 to 4It can be seen that the typical characteristic of mylonitic coal in tectonic coal is that the coal body develops under strong shear stress or plastic rheological conditions, and is affected by both wrinkling and fragmentation. Macroscopically, the coal body is broken, the particle size becomes finer, and it has enhanced foliation, lineation or other ductile deformation structures. Microscopically, the coal particles are directional arranged along the stress direction; the typical characteristic of wrinkled coal in tectonic coal is that the coal body is subjected to geological tectonic stress for a long time under a certain temperature and pressure, resulting in strong ductile wrinkling deformation and fold development. The coal body deformation is controlled by alternating and continuously directional adjustable cracks, and arc-shaped bending and wrinkling deformation are generated along the crack sliding surface; the typical characteristic of scaly coal in tectonic coal is that the coal body is subjected to strong geological shear to form scaly, lens-shaped or willow-shaped structures. Both brittle deformation and ductile deformation can be seen in scaly coal. Therefore, scaly coal is a typical brittle-ductile transitional deformation coal, and being wrapped by sliding surfaces and having scaly structures are its typical characteristics.

[0086] (2) Industrial analysis and elemental analysis of tectonic coal:

[0087] The industrial analysis data of the coal samples in Examples 1 to 10 are shown in Table 1, and the elemental analysis data are shown in Table 2.

[0088] Table 1 Degree of metamorphism and industrial analysis of coal samples in Examples 1 to 10

[0089]

[0090] Note: The symbols in Table 1 represent: R o,max Vitrinite maximum reflectance; M ad Air dried basis moisture, A d Ash content on dry basis, V daf Volatile matter on dry ash-free basis, S t.d Total sulfur content on a dry basis.

[0091] Table 2 Elemental analysis data of coal samples in Examples 1 to 10

[0092]

[0093] Note: The symbols in Table 2 represent: C daf 、H daf 、N daf 、S o,daf are the C, H, N, organic S element contents on a dry ash-free basis, and O daf It is the O element content on a dry ash-free basis calculated by subtraction.

[0094] (3) Analysis of nano-scale pore structure of bituminous-grade structural coal:

[0095] The nanoscale pore volume and specific surface area results of the coal samples in Examples 1 to 10 are shown in Tables 3 and 4.

[0096] Table 3 Nanoscale pore volume of coal samples in Examples 1 to 10

[0097]

[0098] Note: V4 = 15 ~ 100nm; V5 = 5 ~ 15nm; V6 = 2.5 ~ 5nm; V7 < 2.5nm; V 5～7 =V5+V6+V7; V t The WM-18, WM-25, and WM-28 use the same sample WM to measure the nano-scale pore volume.

[0099] Table 4 Nanopore specific surface area of ​​coal samples in Examples 1 to 10

[0100]

[0101]

[0102] Note: S4=15~100nm; S5=5~15nm; S6=2.5~5nm; S7<2.5nm; S 5～7 =S5+S6+S7; S t The WM-18, WM-25, and WM-28 samples were tested using the same WM sample to determine the nanopore specific surface area.

[0103] (4) XRD analysis of coal-based graphite prepared from bituminous grade structural coal:

[0104] The XRD patterns of the coal-based graphites prepared from the coal samples in Examples 1 to 10 are as follows: Figures 5 to 8 As shown. Figures 5 to 8 The measured microcrystalline structural parameters of coal-based graphite with tectonic coal as the carbon source are shown in Table 5.

[0105] Table 5 Microcrystalline structure parameters of coal-based graphite in Examples 1 to 10

[0106]

[0107] Note: The symbols in Table 5 represent: θ 002 is the diffraction angle corresponding to the 002 peak, in degrees; d 002 is the average interlayer spacing of graphite crystallites, which can be obtained according to the Bragg formula: 002 =λ / 2sinθ 002 ,λ is the X-ray wavelength,λ=0.154056nm;FWHM 002 is the half-peak width corresponding to the 002 peak, obtained by XRD analysis software JADE, and the unit is °; L c is the average stacking height of microcrystals in the c-axis direction, and the calculation formula is as follows: Where: β002 is the half-peak width of the 002 peak, θ 002 is the diffraction angle corresponding to the 002 peak position, in degrees; Where: β 100 is the half-peak width of 100, θ 100 is the diffraction angle corresponding to the 100 peak position, in degrees; G is the degree of graphitization, G = [(0.3440-d 002 ) / (0.3440-0.3354)×100%, where 0.3440 nm is the interlayer spacing of completely non-graphitized carbon materials, and 0.3354 nm is the interlayer spacing of ideal single crystal graphite.

[0108] Tables 1 and 2 show that the mined tectonic coal fully meets the requirements of the present invention for metamorphic degree, organic sulfur content, and other factors. Table 3 shows that, as the degree of deformation increases, the pore volume of micropores (5-15 nm) and below in the low-metamorphic bituminous coal increases significantly, while the specific surface area of ​​submicropores (2.5-5 nm) and ultramicropores (<2.5 nm) increases significantly. Correspondingly, the pore volume and specific surface area of ​​transitional pores (15-100 nm) decrease significantly.

[0109] It can be seen from Tables 3 and 4 that tectonic deformation and metamorphic degree lead to a significant increase in the pore volume and specific surface area of ​​micropores (5-15nm), submicropores (2.5-<5nm), and ultramicropores (<2.5nm) in coal, indicating that tectonic stress significantly affects the nanoscale pore structure in coal, and the stress effect of nanoscale deformation is very obvious.

[0110] Table 5 shows that tectonic coal can be directly converted into graphite under vacuum and high-temperature conditions without the addition of a catalyst. Under the same temperature conditions, for tectonic coal of the same metamorphic degree, the greater the degree of deformation, the higher the graphitization degree of the coal-based graphite. Similarly, for tectonic coal of the same deformation degree, the higher the degree of metamorphism, the higher the graphitization degree of the coal-based graphite. Furthermore, for the same tectonic coal, increasing the graphitization temperature can significantly improve the graphitization degree of the coal-based graphite.

[0111] All of the above fully proves that brittle-ductile transition deformation or ductile deformation promotes the flattening of tectonic coal pores by compressing the nanopore diameter, which is the fundamental reason for inducing the preferential orientation of the aromatic structure of tectonic coal above 1800℃ and forming coal-based graphite.

[0112] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the embodiments. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. Application of structural coal in the preparation of coal-based graphite, characterized in that: The following steps are involved: Step 1: crushing the tectonic coal to obtain tectonic coal particles; Step 2: crushing and screening the tectonic coal particles to obtain tectonic coal powder; Step 3: Deashing the tectonic coal powder to obtain deashed tectonic coal powder; Step 4: graphitizing the deashed structural coal powder under vacuum conditions to obtain coal-based graphite; The coal body structure type of the tectonic coal satisfies any one or more of the following: crushed-grained coal, mylonitic coal, etc. The microscopic deformation degree of the tectonic coal satisfies any one or more of the following: brittle-ductile transition, ductile deformation; The graphitization process includes a vacuum carbonization process and a vacuum graphitization process; the processing temperature of the vacuum carbonization process is 1000-1800°C, and the processing time is 0.5-1.0h; the processing temperature of the vacuum graphitization process is 1800-3000°C, and the processing time is 1.5h-4.0h; Among them, in step one, the metamorphic degree of the tectonic coal meets: any one or more of medium-volatile bituminous coal and low-volatile bituminous coal, and the maximum reflectance of the vitrinite is ≥1.1%; the tectonic coal is crushed to a particle size of ≤3 mm to obtain tectonic coal particles; in step two, the tectonic coal particles are crushed and sieved through a sieve with an aperture of ≤75 μm to obtain tectonic coal powder with a particle size of ≤75 μm.

2. The use of structural coal in the preparation of coal-based graphite according to claim 1, characterized in that: In step 1, the coal body structure type of the tectonic coal complies with any one or more of the crushed-grained structure coal and mylonitic structure coal specified in the national standard GB / T 30050-2013.

3. The use of structural coal in the preparation of coal-based graphite according to claim 1, characterized in that: In step 1, the organic element content of the tectonic coal satisfies the following requirement: the organic sulfur content on a dry ash-free basis is less than 1%.

4. The use of structural coal in the preparation of coal-based graphite according to claim 1, characterized in that: In step 1, the crushing is carried out by a crusher or manually, and the crusher is any one of a jaw crusher, a hammer crusher, and a roller crusher.

5. The use of structural coal in the preparation of coal-based graphite according to claim 1, characterized in that: In step 2, the pulverization is performed by a pulverizer or manually, and the pulverizer is any one of a steel rod mill, a steel ball mill, and a sealed grinder; In step 2, the screening is performed using a standard square hole sieve, and the screening is performed using a screening machine or manual screening.

6. The use of structural coal in the preparation of coal-based graphite according to claim 1, characterized in that: In step 3, the deashing process is as follows: soaking the pulverized coal in a hydrochloric acid solution at a temperature below 60° C. for more than 24 hours, and filtering to remove the hydrochloric acid solution; Then, the tectonic coal powder is immersed in a hydrofluoric acid solution at a temperature below 60° C. for more than 24 hours, and the hydrofluoric acid solution is filtered out; the tectonic coal powder is washed with deionized water until the pH value is 7, and finally vacuum dried at a temperature below 60° C. for more than 24 hours to obtain the deashed tectonic coal powder.

7. The use of structural coal in the preparation of coal-based graphite according to claim 6, characterized in that: The ratio of the tectonic coal powder, hydrochloric acid solution and hydrofluoric acid solution is 10-15 g: 70-90 ml: 70-90 ml, the concentration of the hydrochloric acid solution is 4-6 mol / L, and the concentration of the hydrofluoric acid solution is 30-50 wt%.

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