Purification system and microcrystalline graphite purification method

Abstract

The invention discloses a purification system and a microcrystalline graphite purification method. The microcrystalline graphite purification method comprises the following steps: contacting a microcrystalline graphite raw material with an oxygen-containing gas at a first temperature to at least convert at least a part of first impurities in the microcrystalline graphite raw material into a first volatile product and at least activate at least a part of second impurities in the microcrystalline graphite raw material to obtain pretreated microcrystalline graphite; and contacting the pretreated microcrystalline graphite with a halogen-containing gas at a second temperature so as to at least convert at least part of the activated second impurities in the pretreated microcrystalline graphite into a second volatile product, thereby obtaining purified microcrystalline graphite. The purification process is simple, easy to operate, low in energy consumption, safe and environment-friendly, the carbon content of the microcrystalline graphite can be remarkably improved, the crystallinity is remarkably improved, the impurity content is greatly reduced, and the application requirement of a battery negative electrode material is completely met.

Description

Technical Field

[0001] The present application specifically relates to a purification system and a method for purifying microcrystalline graphite. Technical Background

[0002] Natural microcrystalline graphite has smaller crystals than flake graphite, has a higher degree of disorder, and is isotropic between particles. Therefore, in theory, its lithium ion diffusion performance is much higher than that of flake graphite, making it a preferred raw material for negative electrode materials of lithium-ion power batteries. However, natural microcrystalline graphite has more impurities and is relatively difficult to purify, which is one of the main bottlenecks restricting its application.

[0003] At present, the commonly used methods for purifying microcrystalline graphite mainly include flotation, pickling, flotation-pickling combined method, high-temperature evaporation purification, etc. However, due to the small grain size of microcrystalline graphite and the difficulty of monomer dissociation, compared with flake graphite, microcrystalline graphite has poor floatability, and the purity after flotation can only reach 80% to 95%, which does not meet the requirements of graphite negative electrode materials for batteries. The pickling method requires the use of a large amount of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, etc., which is costly and causes serious environmental pollution. Moreover, it is still difficult for the purified microcrystalline graphite to reach battery-grade purity. Although the high-temperature evaporation purification method has the advantages of being environmentally friendly, it can only be operated intermittently, with a small processing volume and high energy consumption. Summary of the invention

[0004] The main purpose of the present application is to provide a purification system and a method for purifying microcrystalline graphite to overcome the deficiencies in the prior art.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted in this application includes:

[0006] The first aspect of the present application provides a purification system, which comprises:

[0007] A pretreatment unit, which is at least used to contact the microcrystalline graphite raw material with an oxygen-containing gas at a first temperature to at least convert at least a portion of first impurities in the microcrystalline graphite raw material into a first volatile product and at least activate at least a portion of second impurities in the microcrystalline graphite raw material to obtain pretreated microcrystalline graphite;

[0008] The purification unit is connected to the pretreatment unit and is used at least to contact the pretreated microcrystalline graphite with a halogen-containing gas at a second temperature to convert at least part of the activated second impurities in the pretreated microcrystalline graphite into a second volatile product to obtain purified microcrystalline graphite.

[0009] The second aspect of the present application provides a method for purifying microcrystalline graphite, which comprises the following steps:

[0010] S1, contacting a microcrystalline graphite raw material with an oxygen-containing gas at a first temperature to convert at least a portion of a first impurity in the microcrystalline graphite raw material into a first volatile product, and to activate at least a portion of a second impurity in the microcrystalline graphite raw material, to obtain pretreated microcrystalline graphite;

[0011] S2. Contacting the pretreated microcrystalline graphite with a halogen-containing gas at a second temperature to convert at least a portion of the activated second impurities in the pretreated microcrystalline graphite into a second volatile product to obtain purified microcrystalline graphite.

[0012] Compared with the prior art, the present application is based on fluidized bed technology. By first pre-treating the microcrystalline graphite raw material in an oxygen-containing atmosphere, the amorphous carbon and other carbon-containing impurities therein can be burned and converted into carbon dioxide and the like for removal, and heat can be generated, thereby reducing the energy consumption of the pretreatment process. At the same time, the impurities containing metal elements, silicon, etc. in the microcrystalline graphite raw material can be pre-converted (activated) to form substances that are easier to react with halogen-containing gases to form volatile products. The halogen-containing gas is then used to contact and react with the pretreated microcrystalline graphite, and the activated and unactivated impurities containing metal elements, silicon, etc. can be further converted into volatile substances for removal, so that the carbon content of the purified microcrystalline graphite finally obtained is significantly increased (up to 99.99%), the degree of graphitization is significantly improved (up to 97.2% or more), and the impurity content is greatly reduced (Fe element content <1ppm), which fully meets the application requirements of battery negative electrode materials.

[0013] The continuous purification process of the present application is easy to scale up for industrialization, has low energy consumption, is safe and environmentally friendly, and can significantly increase the carbon content and crystallinity of microcrystalline graphite. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The exemplary embodiments of the present application are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are only used to teach those skilled in the art how to implement the present application, and are not intended to exhaust all feasible methods of the present application, nor to limit the scope of protection of the present application.

[0015] Figure 1 is a schematic diagram of the structure of a purification system in Example 1 of the present application;

[0016] Figure 2 It is a schematic diagram of the structure of a purification system in Comparative Example 2 of the present application;

[0017] Figure 3 is a schematic diagram of the structure of a purification system in Example 3 of the present application;

[0018] Figure 4 It is a schematic diagram of the structure of a purification system in Example 4 of the present application. DETAILED DESCRIPTION

[0019] As mentioned above, in view of the defects of the existing microcrystalline graphite purification technology, the applicant has proposed the technical solution of the present application after long-term research and practice, thereby well overcoming the shortcomings of the existing technology. The technical solution of the present application will be described in detail below.

[0020] Some embodiments of the present application provide a purification system comprising:

[0021] A pretreatment unit, which is at least used to contact the microcrystalline graphite raw material with an oxygen-containing gas at a first temperature to at least convert at least a portion of first impurities in the microcrystalline graphite raw material into a first volatile product and at least activate at least a portion of second impurities in the microcrystalline graphite raw material to obtain pretreated microcrystalline graphite;

[0022] The purification unit is connected to the pretreatment unit and is used at least to contact the pretreated microcrystalline graphite with a halogen-containing gas at a second temperature to convert at least part of the activated second impurities in the pretreated microcrystalline graphite into a second volatile product to obtain purified microcrystalline graphite.

[0023] It should be noted that the reactivity of the activated second impurity when reacting with the halogen-containing gas is enhanced, and it is easier for the second impurity to react with the halogen-containing gas and be converted into a volatile product.

[0024] In one embodiment, the first impurities include carbon-containing impurities, and the second impurities include impurities containing at least metal elements and / or silicon elements, wherein the relationship between the oxygen content a in the oxygen-containing gas, the feed rate m (kg / h) of the microcrystalline graphite raw material, the average flow rate Q (kg / h) of the oxygen-containing gas, and the content x of the first impurity and the content μ of the second impurity in the microcrystalline graphite raw material satisfies the following formula:

[0025] aQ=αxm+βym

[0026] Among them, a=1V / V%~30V / V%, the first temperature T=800℃~1100℃, the contact time between the microcrystalline graphite raw material and the oxygen-containing gas at the first temperature t=10min~120min, α is the oxidation coefficient of the first impurity, α=1.0~3.0, β is the activation coefficient of the second impurity, β=0.01~0.05.

[0027] In one embodiment, the pretreatment unit includes at least one pretreatment fluidized bed, which is used to provide an environment for the microcrystalline graphite raw material to contact with an oxygen-containing gas at a first temperature. The purification unit includes at least one purification fluidized bed, which is used to provide an environment for the pretreated microcrystalline graphite to contact with a halogen-containing gas at a second temperature. The pretreatment fluidized bed and the purification fluidized bed are arranged in series.

[0028] In one embodiment, the pretreatment unit comprises a plurality of pretreatment fluidized beds, and the plurality of pretreatment fluidized beds are arranged in series and / or in parallel.

[0029] Exemplarily, in some cases, a plurality of pretreatment fluidized beds may be arranged in series, that is, the microcrystalline graphite raw material is pretreated in each level of pretreatment fluidized beds in turn, which is beneficial to improving the removal rate of the first impurity and the activation rate of the second impurity in the microcrystalline graphite raw material. In other cases, a plurality of pretreatment fluidized beds may be arranged in parallel, so that the microcrystalline graphite raw material may be pretreated using a plurality of pretreatment fluidized beds at the same time, which helps to reduce the bed height and improve the fluidization stability of the fluidized bed device. In some other cases, some of the pretreatment fluidized beds in the plurality of pretreatment fluidized beds may be arranged in series, and then arranged in parallel with other pretreatment fluidized beds, so as to take into account the improvement of the microcrystalline graphite impurity removal rate and the fluidization stability of the fluidized bed device.

[0030] In one embodiment, the purification unit comprises a plurality of purification fluidized beds, and the plurality of purification fluidized beds are arranged in series and / or in parallel.

[0031] Exemplarily, in some cases, multiple purification fluidized beds can be arranged in series, that is, the pretreated microcrystalline graphite is purified in each level of purification fluidized bed in turn, which is beneficial to improving the removal rate of the second impurity in the microcrystalline graphite raw material. In other cases, multiple purification fluidized beds can be arranged in parallel, so that the microcrystalline graphite can be purified by using multiple purification fluidized beds at the same time, reducing the bed height, which helps to improve the fluidization stability of the fluidized bed device. In some other cases, some of the pretreatment fluidized beds in the multiple pretreatment fluidized beds can be arranged in series, and then arranged in parallel with other pretreatment fluidized beds, so as to take into account the improvement of the microcrystalline graphite impurity removal rate and the fluidization stability of the fluidized bed device.

[0032] In one embodiment, the microcrystalline graphite inlet of the pretreatment fluidized bed is connected to the purified microcrystalline graphite outlet of the purification fluidized bed. With this design, when the content of the second impurity in the purified microcrystalline graphite output from the purification fluidized bed does not meet the standard, the purified microcrystalline graphite can be re-input into the purification fluidized bed and purified again, and then by repeating this process once or multiple times, the content of the second impurity in the purified microcrystalline graphite output from the purification fluidized bed can meet the set requirements.

[0033] In one embodiment, the purification system further comprises at least one or more of a primary raw material feed tank, a first cyclone separation device, a first return device, a second return device, a third return device, a metal impurity collector or an absorption tower.

[0034] In one embodiment, the pretreatment fluidized bed comprises a pretreatment fluidized bed body and a first pretreatment cyclone separation device, a second pretreatment cyclone separation device, a first pretreatment return device, a second pretreatment return device, a third pretreatment return device, and a pretreatment intermediate tank;

[0035] The microcrystalline graphite inlet of the pretreatment fluidized bed body is connected to the raw material feed tank, and the microcrystalline graphite outlet of the pretreatment fluidized bed body is connected to the pretreatment intermediate tank.

[0036] The first pre-treatment cyclone separation device is arranged in the pre-treatment fluidized bed body and is at least used to collect solid particles in the tail gas generated in the pre-treatment fluidized bed body, the second pre-treatment cyclone separation device is arranged outside the pre-treatment fluidized bed body, the second pre-treatment cyclone separation device is also connected in series with the first pre-treatment cyclone separation device, and the second pre-treatment cyclone separation device is at least used to collect solid particles in the tail gas output by the first pre-treatment cyclone separation device;

[0037] The first pretreatment return device is arranged outside the pretreatment fluidized bed body, and is respectively connected to the microcrystalline graphite outlet and the microcrystalline graphite inlet of the pretreatment fluidized bed body, and returns at least part of the microcrystalline graphite output from the microcrystalline graphite outlet of the pretreatment fluidized bed body back into the pretreatment fluidized bed body. The second pretreatment return device is arranged inside the pretreatment fluidized bed body, and is connected to the first pretreatment cyclone separation device, and is used to return the solid-phase material of the first pretreatment cyclone separation device back to the pretreatment reaction zone of the pretreatment fluidized bed body. The third pretreatment return device is arranged outside the pretreatment fluidized bed body, and is respectively connected to the second pretreatment cyclone separation device and the pretreatment fluidized bed body, and is used to return the solid-phase material of the second pretreatment cyclone separation device back to the pretreatment reaction zone of the pretreatment fluidized bed body.

[0038] Further, the raw material feed tank is connected to the microcrystalline graphite inlet of the pretreatment fluidized bed body. With this design, the microcrystalline graphite enters the pretreatment fluidized bed through the two-stage series-connected raw material feed tanks, which is beneficial to improving the continuity and stability of the feed and the feed rate. In other cases, two raw material feed tanks can be arranged in parallel, so that the two raw material feed tanks can be used to feed alternately or simultaneously, which is beneficial to improving the continuity and stability of the feed and the feed rate. In some other cases, multiple raw material feed tanks can be arranged in series and then arranged in parallel with other raw material feed tanks, which is further beneficial to the continuity and stability of the feed and the improvement of the feed rate.

[0039] Furthermore, the microcrystalline graphite inlet of the pretreatment fluidized bed body is connected to the pretreatment microcrystalline graphite outlet through the first pretreatment return device. With this design, when the content of the first impurity and / or the activation rate of the second impurity in the pretreatment microcrystalline graphite output by the pretreatment fluidized bed does not meet the standard, the pretreatment microcrystalline graphite can be re-input into the pretreatment fluidized bed body and pretreated again, and then by repeating this process once or multiple times, the content of the first impurity and / or the activation rate of the second impurity in the pretreatment microcrystalline graphite output by the pretreatment fluidized bed can meet the set requirements.

[0040] Furthermore, the first pretreatment cyclone separation device is arranged in the main body of the pretreatment fluidized bed, and is at least used to collect solid particles in the tail gas generated in the main body of the pretreatment fluidized bed. With this design, the fine powder particles entrained into the expanded section space of the pretreatment fluidized bed can be collected and fed to the second pretreatment return device, which is beneficial to improving the product yield and pretreatment effect. In other cases, two first pretreatment cyclone separation devices can be arranged in parallel or in series, so as to improve the subdivision collection efficiency, which is beneficial to improving the product yield and pretreatment effect. In some other cases, multiple first pretreatment cyclone separation devices can be arranged in series, and then arranged in parallel with other first pretreatment cyclone separation devices, which is further beneficial to improving the product yield and pretreatment effect.

[0041] Further, the second pretreatment return device is arranged inside the pretreatment fluidized bed body, the second pretreatment return device is connected to the first pretreatment cyclone separation device, and is used to return the solid phase material of the first pretreatment cyclone separation device to the pretreatment reaction zone (i.e., fluidized bed reaction zone) of the pretreatment fluidized bed body. With this design, the fine powder particles collected by the first pretreatment cyclone separation device can be returned to the fluidized bed reaction zone, which is beneficial to improving the product yield and pretreatment effect. In other cases, two first pretreatment cyclone separation devices can be arranged in parallel or in series, and respectively matched with the second pretreatment return device or a second pretreatment return device can be used together, so as to improve the fine powder return efficiency, which is beneficial to improving the product yield and pretreatment effect. In some other cases, N first pretreatment cyclone separation devices can be arranged in series, and then arranged in parallel with other M first pretreatment cyclone separation devices, and matched with 1 to M + N second pretreatment return devices, so as to further benefit the improvement of product yield and pretreatment effect.

[0042] Further, the second pretreatment cyclone separation device is arranged outside the pretreatment fluidized bed body, the second pretreatment cyclone separation device is also connected in series with the first pretreatment cyclone separation device, the second pretreatment cyclone separation device is at least used to collect solid particles in the tail gas output by the first pretreatment cyclone separation device, and the third pretreatment return device is arranged outside the pretreatment fluidized bed body, the third pretreatment return device is connected to the second pretreatment cyclone separation device and the pretreatment fluidized bed body respectively, and is used to return the solid phase material of the second pretreatment cyclone separation device to the fluidized bed reaction zone of the pretreatment fluidized bed body; using this design, the fine powder particles in the tail gas of the pretreatment fluidized bed can be collected and fed to the third pretreatment return device, which is beneficial to improving the product yield and pretreatment effect. In other cases, two second pretreatment cyclone separation devices can be arranged in parallel or in series, so as to improve the subdivision collection efficiency, which is beneficial to improving the product yield and pretreatment effect. In some other cases, a plurality of second pretreatment cyclone separation devices may be arranged in series and then arranged in parallel with other second pretreatment cyclone separation devices, thereby further benefiting the improvement of product yield and pretreatment effect.

[0043] In one embodiment, the pretreatment unit also includes feed weighing, vacuum feeding, mass flow meter, temperature sensor, pressure sensor, tail gas detection, ball valve and other equipment to achieve safe, stable and continuous operation of the pretreatment fluidized bed.

[0044] In one embodiment, the purification fluidized bed comprises a purification fluidized bed body and a first purification cyclone separation device, a second purification cyclone separation device, a first purification return device, a second purification return device, a third purification return device, and a purification intermediate tank;

[0045] The microcrystalline graphite inlet of the purification fluidized bed body is connected to the raw material feed tank, and the microcrystalline graphite outlet of the purification fluidized bed body is connected to the purification intermediate tank.

[0046] The first purification cyclone separation device is arranged in the purification fluidized bed body, and is at least used to collect solid particles in the tail gas generated in the purification fluidized bed body; the second purification cyclone separation device is arranged outside the purification fluidized bed body, and the second purification cyclone separation device is also connected in series with the first purification cyclone separation device, and the second purification cyclone separation device is at least used to collect solid particles in the tail gas output by the first purification cyclone separation device;

[0047] The first purification return device is arranged outside the purification fluidized bed body, and is respectively connected to the microcrystalline graphite outlet and the microcrystalline graphite inlet of the purification fluidized bed body, and returns at least part of the microcrystalline graphite output from the microcrystalline graphite outlet of the purification fluidized bed body back into the purification fluidized bed body. The second purification return device is arranged inside the purification fluidized bed body, and is connected to the first purification cyclone separation device, and is used to return the solid-phase material of the first purification cyclone separation device back to the purification reaction zone of the purification fluidized bed body. The third purification return device is arranged outside the purification fluidized bed body, and is respectively connected to the second purification cyclone separation device and the purification fluidized bed body, and is used to return the solid-phase material of the second purification cyclone separation device back to the purification reaction zone of the purification fluidized bed body.

[0048] It should be noted that the structure and advantages of the purification fluidized bed are substantially the same as those of the pretreatment fluidized bed, and will not be described in detail herein.

[0049] In one embodiment, the purification unit also includes feed weighing, vacuum loading, mass flow meter, temperature sensor, pressure sensor, tail gas detection, ball valve and other equipment to achieve safe, stable and continuous operation of the purification fluidized bed.

[0050] In one embodiment, the purification system further comprises a condensation tank and an absorption tower, the tail gas discharge port of the pretreatment unit is directly connected to the absorption tower, the tail gas discharge port of the purification unit is connected to the condensation tank, and the condensation tank is connected to the absorption tower. With this design, metal salts can be collected by quenching the condensation tank, and the tail gas can be purified by the absorption tower.

[0051] In one embodiment, the continuous purification system further comprises at least one of a desorption unit and a temperature reduction unit.

[0052] Furthermore, the desorption unit is connected to the purification unit and is used to remove at least part of the second volatile product adsorbed on the purified microcrystalline graphite.

[0053] Furthermore, the desorption unit comprises at least one desorption fluidized bed, which is used to remove residual metal impurities and halogens, and the desorption fluidized bed is arranged in series with the purification fluidized bed.

[0054] In some cases, the desorption unit includes a plurality of desorption fluidized beds, and the plurality of desorption fluidized beds are arranged in series and / or in parallel, thereby increasing the processing capacity and improving the desorption effect.

[0055] In one embodiment, the desorption fluidized bed comprises a desorption fluidized bed body and a first desorption cyclone separation device, a second desorption cyclone separation device, a first desorption return device, a second desorption return device, a third desorption return device, and a desorption intermediate tank;

[0056] The microcrystalline graphite inlet of the desorption fluidized bed body is connected to the raw material feed tank, and the microcrystalline graphite outlet of the desorption fluidized bed body is connected to the desorption intermediate tank.

[0057] The first desorption cyclone separation device is arranged in the desorption fluidized bed body, and is at least used to collect solid particles in the tail gas generated in the desorption fluidized bed body, the second desorption cyclone separation device is arranged outside the desorption fluidized bed body, the second desorption cyclone separation device is also connected in series with the first desorption cyclone separation device, and the second desorption cyclone separation device is at least used to collect solid particles in the tail gas output by the first desorption cyclone separation device;

[0058] The first desorption return device is arranged outside the desorption fluidized bed body, and is respectively connected to the microcrystalline graphite outlet and the microcrystalline graphite inlet of the desorption fluidized bed body, and returns at least part of the microcrystalline graphite output from the microcrystalline graphite outlet of the desorption fluidized bed body back into the desorption fluidized bed body. The second desorption return device is arranged inside the desorption fluidized bed body, and is connected to the first desorption cyclone separation device, and is used to return the solid-phase material of the first desorption cyclone separation device back to the desorption reaction zone of the desorption fluidized bed body. The third desorption return device is arranged outside the desorption fluidized bed body, and is respectively connected to the second desorption cyclone separation device and the desorption fluidized bed body, and is used to return the solid-phase material of the second desorption cyclone separation device back to the desorption fluidized bed body.

[0059] It should be noted that the structure and advantages of the desorption fluidized bed are substantially the same as those of the pretreatment fluidized bed, and will not be described in detail herein.

[0060] In other cases, the desorption unit may also include equipment such as a vacuum pump, and the desorption effect can be further improved under high vacuum conditions.

[0061] Furthermore, the cooling unit is at least connected to the pretreatment unit and / or the purification unit, and is at least used to recover the heat in the gas phase material and / or solid phase material output by the pretreatment unit and / or the purification unit. In one embodiment, the pretreatment unit, the purification unit, the desorption unit, and the cooling unit are connected in sequence.

[0062] In one embodiment, the cooling unit comprises one or more cooling fluidized beds, and a plurality of the cooling fluidized beds are arranged in series and / or in parallel.

[0063] In one embodiment, the cooling fluidized bed comprises a cooling fluidized bed body and a first cooling cyclone separation device, a second cooling cyclone separation device, a first cooling return device, a second cooling return device, a third cooling return device, and a cooling intermediate tank;

[0064] The microcrystalline graphite inlet of the cooling fluidized bed body is connected to the raw material feed tank, and the microcrystalline graphite outlet of the cooling fluidized bed body is connected to the cooling intermediate tank.

[0065] The first cooling cyclone separation device is arranged in the cooling fluidized bed body, and is at least used to collect solid particles in the tail gas generated in the cooling fluidized bed body, the second cooling cyclone separation device is arranged outside the cooling fluidized bed body, the second cooling cyclone separation device is also connected in series with the first cooling cyclone separation device, and the second cooling cyclone separation device is at least used to collect solid particles in the tail gas output by the first cooling cyclone separation device;

[0066] The first cooling and returning device is arranged outside the cooling fluidized bed body, and is respectively connected to the microcrystalline graphite outlet and the microcrystalline graphite inlet of the cooling fluidized bed body, and returns at least part of the microcrystalline graphite output from the microcrystalline graphite outlet of the cooling fluidized bed body back into the cooling fluidized bed body. The second cooling and returning device is arranged inside the cooling fluidized bed body, and is connected to the first cooling cyclone separation device, and is used to return the solid-phase material of the first cooling cyclone separation device to the cooling reaction zone of the cooling fluidized bed body. The third cooling and returning device is arranged outside the cooling fluidized bed body, and is respectively connected to the second cooling cyclone separation device and the cooling fluidized bed body, and is used to return the solid-phase material of the second cooling cyclone separation device back to the cooling fluidized bed body.

[0067] It should be noted that the structure and advantages of the cooling fluidized bed are basically the same as the structure and advantages of the pretreatment fluidized bed, and will not be repeated here.

[0068] Furthermore, the cooling unit may also include equipment such as a heat exchanger and a gas purifier, and inert gases such as nitrogen and / or argon carry the recovered heat energy from the cooling unit back to the pretreatment unit and / or the purification unit and / or the desorption unit.

[0069] In the present application, the first impurity includes amorphous carbon, and the second impurity includes oxides or silicates or carbonates or chlorides or nitrates or fluorides containing at least one element of iron, calcium, aluminum, magnesium, potassium, and sodium. Specifically, the second impurity is mainly quartz, feldspar, mica, calcite, kaolin, etc.

[0070] In the present application, the first volatile product includes pyrolysis gas and / or tar product; the second volatile product includes metal halide and / or silicon halide.

[0071] In the present application, the pyrolysis gas includes any one or more combinations of hydrogen, carbon dioxide, carbon monoxide, alkane gas, hydrogen sulfide, water, and nitrogen.

[0072] Some embodiments of the present application also provide a method for purifying microcrystalline graphite, which comprises the following steps:

[0073] S1, contacting a microcrystalline graphite raw material with an oxygen-containing gas at a first temperature to convert at least a portion of a first impurity in the microcrystalline graphite raw material into a first volatile product, and to activate at least a portion of a second impurity in the microcrystalline graphite raw material, to obtain pretreated microcrystalline graphite;

[0074] S2. Contacting the pretreated microcrystalline graphite with a halogen-containing gas at a second temperature to convert at least a portion of the activated second impurities in the pretreated microcrystalline graphite into a second volatile product to obtain purified microcrystalline graphite.

[0075] In one embodiment, the first impurities include carbon-containing impurities, and the second impurities include impurities containing at least metal elements and / or silicon elements, wherein the relationship between the oxygen content a in the oxygen-containing gas, the feed rate m (kg / h) of the microcrystalline graphite raw material, the average flow rate Q (kg / h) of the oxygen-containing gas, and the content x of the first impurity and the content y of the second impurity in the microcrystalline graphite raw material satisfies the following formula:

[0076] aQ=αxm+βym

[0077] Among them, a=1V / V%~30V / V%, the first temperature T=800℃~1100℃, the contact time between the microcrystalline graphite raw material and the oxygen-containing gas at the first temperature t=10min~120min, α is the oxidation coefficient of the first impurity, α=1.0~3.0, β is the activation coefficient of the second impurity, β=0.01~0.05.

[0078] In one embodiment, the method specifically includes: using the pretreated microcrystalline graphite or the purified microcrystalline graphite as the microcrystalline graphite raw material, and repeatedly performing the operation of step S1 more than once until the first impurity content in the obtained pretreated microcrystalline graphite is lower than a first threshold value.

[0079] In one embodiment, the method specifically includes: using the purified microcrystalline graphite as the pretreated microcrystalline graphite, and repeatedly performing the operation of step S2 more than once until the second impurity content in the purified microcrystalline graphite is lower than a second threshold value.

[0080] In one embodiment, step S1 specifically includes: when the microcrystalline graphite raw material is contacted with the oxygen-containing gas at the first temperature, part of the microcrystalline graphite in the microcrystalline graphite raw material is also burned to generate heat, so that the corresponding reaction environment is maintained at the first temperature. Through this operation, the first impurity can be removed, and part of the coated second impurity is exposed, which is conducive to the removal of the second impurity. At the same time, heat for maintaining the reaction temperature can also be provided, which is conducive to uniform temperature in the fluidized bed.

[0081] In one embodiment, the method further comprises:

[0082] S3. Contacting the purified microcrystalline graphite with a desorption gas at a third temperature, thereby removing at least a portion of the second volatile product adsorbed on the purified microcrystalline graphite.

[0083] In one embodiment, the method specifically comprises: performing the operation of step S1 in at least one pretreatment fluidized bed; and / or performing the operation of step S2 in at least one purification fluidized bed.

[0084] In one embodiment, the method further comprises:

[0085] S4, exchanging heat between the microcrystalline graphite raw material and / or the oxygen-containing gas and the gaseous phase material and / or the solid phase material output from the pretreatment fluidized bed / or the purification fluidized bed to preheat the microcrystalline graphite raw material and / or the oxygen-containing gas, and then inputting the preheated microcrystalline graphite raw material and / or the oxygen-containing gas into the pretreatment fluidized bed to perform step S1.

[0086] In one embodiment, the method further comprises:

[0087] S4, exchanging heat between the pretreated microcrystalline graphite and / or the halogen-containing gas and the gaseous phase material and / or the solid phase material output from the pretreatment fluidized bed and / or the purification fluidized bed to preheat the pretreated microcrystalline graphite and / or the halogen-containing gas, and then inputting the preheated pretreated microcrystalline graphite and / or the halogen-containing gas into the purification fluidized bed to perform step S2, wherein the halogen-containing gas includes at least one of chlorine, fluorine, hydrogen chloride, and Freon.

[0088] In the present application, the first impurity includes amorphous carbon, the second impurity includes oxides or silicates or carbonates or chlorides or nitrates or fluorides containing at least one element of iron, calcium, aluminum, magnesium, potassium, and sodium, the first volatile product includes pyrolysis gas and / or tar products, and the second volatile product includes metal halides and / or silicon halides.

[0089] In the present application, the pyrolysis gas includes any one or more combinations of hydrogen, carbon dioxide, carbon monoxide, alkane gas, hydrogen sulfide, water, and nitrogen.

[0090] The technical solution of the present application will be explained in more detail below in conjunction with several embodiments, but these specific descriptions are only used to teach those skilled in the art how to implement the present application, rather than to exhaust all feasible methods of the present application, nor to limit the scope of the present application. Unless otherwise specified, the various raw materials in the following examples and comparative examples can be obtained from commercial sources, etc., and the test methods and test equipment used are also commonly used in the art.

[0091] Example 1

[0092] See also Figure 1 The purification system provided in this embodiment is a four-stage structure of pretreatment, purification, desorption and cooling, which specifically includes:

[0093] A two-stage raw material feed tank 100, a pretreatment fluidized bed 1, a purification fluidized bed 2, a desorption fluidized bed 3, a cooling fluidized bed 4, a condensation tank 5 and an absorption tower 6. The two-stage feed tank 100 is connected to the microcrystalline graphite inlet of the pretreatment fluidized bed 1. The pretreatment fluidized bed 1, the purification fluidized bed 2, the desorption fluidized bed 3 and the cooling fluidized bed 4 are connected in series in sequence. The tail gas discharge ports of the pretreatment fluidized bed 1 and the cooling fluidized bed 4 are directly connected to the absorption tower 6, the tail gas discharge ports of the purification fluidized bed 2 and the desorption fluidized bed 3 are connected to the condensation tank 5, the condensation tank 5 is also connected to the absorption tower 6, and the tail gas discharge port of the cooling fluidized bed 4 is also connected to the air inlets of the pretreatment fluidized bed 1, the purification fluidized bed 2 and the desorption fluidized bed 3, respectively.

[0094] In this embodiment, the pretreatment fluidized bed 1 includes a pretreatment fluidized bed body, a pretreatment fluidized bed air intake structure 101, a first pretreatment cyclone separation device 102, a second pretreatment cyclone separation device 105, a first pretreatment return device, a second pretreatment return device 103, a third pretreatment return device 106, and a pretreatment intermediate tank 104; the microcrystalline graphite inlet of the pretreatment fluidized bed body is connected to the two-stage raw material feed tank 100, the microcrystalline graphite outlet of the pretreatment fluidized bed body is connected to the pretreatment intermediate tank 104, the pretreatment fluidized bed air intake structure 101 is connected to the air inlet of the pretreatment fluidized bed body, and the first pretreatment return device is arranged outside the pretreatment fluidized bed body, and is respectively connected to the microcrystalline graphite outlet of the pretreatment fluidized bed body. The first pretreatment cyclone separation device 102 is connected to the inlet of the microcrystalline graphite, the first pretreatment cyclone separation device 102 is arranged in the settling area of ​​the pretreatment fluidized bed body, one end of the second pretreatment return device 103 is connected to the first pretreatment cyclone separation device 102, and the other end is arranged in the reaction area of ​​the pretreatment fluidized bed body, the second pretreatment cyclone separation device 105 and the third pretreatment return device 106 are arranged outside the pretreatment fluidized bed body, the second pretreatment cyclone separation device 105 is also connected in series with the first pretreatment cyclone separation device 102, the third pretreatment return device 106 is respectively connected to the second pretreatment cyclone separation device 105 and the reaction area of ​​the pretreatment fluidized bed body, and the tail gas discharge port of the second pretreatment cyclone separation device 105 is also connected to the absorption tower 6;

[0095] The purification fluidized bed 2 comprises a purification fluidized bed body, a purification fluidized bed air intake structure 201, a first purification cyclone separation device 202, a second purification cyclone separation device 205, a first purification return device, a second purification return device 203, a third purification return device 206, and a purification intermediate tank 204; the microcrystalline graphite inlet of the purification fluidized bed body is connected to the pretreatment intermediate tank 104, the microcrystalline graphite outlet of the purification fluidized bed body is connected to the purification intermediate tank 204, the purification fluidized bed air intake structure 202 is connected to the air inlet of the purification fluidized bed body, and the first purification return device is arranged outside the purification fluidized bed body, and is respectively connected to the microcrystalline graphite outlet, the microcrystalline graphite outlet and the third purification return device of the purification fluidized bed body. The first purification cyclone separation device 202 is arranged in the settling area of ​​the purification fluidized bed body, one end of the second purification return device 203 is connected to the first purification cyclone separation device 202, and the other end is arranged in the reaction area of ​​the purification fluidized bed body, the second purification cyclone separation device 205 and the third purification return device 206 are arranged outside the purification fluidized bed body, the second purification cyclone separation device 205 is also connected in series with the first purification cyclone separation device 202, the third purification return device 206 is respectively connected to the second purification cyclone separation device 205 and the reaction area of ​​the purification fluidized bed body, and the tail gas discharge port of the second purification cyclone separation device 205 is also connected to the condensation tank 5;

[0096] The desorption fluidized bed 3 comprises a desorption fluidized bed body, a desorption fluidized bed air inlet structure 301, a first desorption cyclone separation device 302, a second desorption cyclone separation device 305, a first desorption return device, a second desorption return device 303, a third desorption return device 306, and a desorption intermediate tank 304; the microcrystalline graphite inlet of the desorption fluidized bed body is connected to the purification intermediate tank 204, the microcrystalline graphite outlet of the desorption fluidized bed body is connected to the desorption intermediate tank 304, the desorption fluidized bed air inlet structure 302 is connected to the air inlet of the desorption fluidized bed body, the first desorption return device is arranged outside the desorption fluidized bed body, and is respectively connected to the microcrystalline graphite outlet, the microcrystalline graphite outlet and the desorption intermediate tank 304 of the desorption fluidized bed body. The inlet is connected, the first desorption cyclone separation device 302 is arranged in the sedimentation area of ​​the desorption fluidized bed body, one end of the second desorption return device 303 is connected to the first desorption cyclone separation device 302, and the other end is arranged in the reaction area of ​​the desorption fluidized bed body, the second desorption cyclone separation device 305 and the third desorption return device 306 are arranged outside the desorption fluidized bed body, the second desorption cyclone separation device 305 is also connected in series with the first desorption cyclone separation device 302, the third desorption return device 306 is respectively connected to the second desorption cyclone separation device 305 and the reaction area of ​​the desorption fluidized bed body, and the tail gas discharge port of the second desorption cyclone separation device 305 is also connected to the condensation tank 5;

[0097] The cooling fluidized bed 4 includes a cooling fluidized bed body, a cooling fluidized bed air intake structure 401, a first cooling cyclone separation device 402, a second cooling cyclone separation device 405, a first cooling return device, a second cooling return device 403, a third cooling return device 406, and a cooling intermediate tank 404; the microcrystalline graphite inlet of the cooling fluidized bed body is connected to the pretreatment intermediate tank 104, the microcrystalline graphite outlet of the cooling fluidized bed body is connected to the desorption intermediate tank 304, the cooling fluidized bed air intake structure 402 is connected to the air inlet of the cooling fluidized bed body, the first cooling return device is arranged outside the cooling fluidized bed body, and is respectively connected to the microcrystalline graphite outlet and the microcrystalline graphite inlet of the cooling fluidized bed body, the first cooling cyclone separation device 402 is arranged in the sedimentation area of ​​the cooling fluidized bed body, the third cooling return device 406 is connected to the desorption intermediate tank 304, the cooling fluidized bed air intake structure 402 is connected to the air inlet of the cooling fluidized bed body One end of the second cooling and returning material device 403 is connected to the first cooling cyclone separation device 402, and the other end is arranged in the reaction zone of the cooling fluidized bed body. The second cooling cyclone separation device 405 and the third cooling and returning material device 406 are arranged outside the cooling fluidized bed body. The second cooling cyclone separation device 405 is also connected in series with the first cooling cyclone separation device 402. The third cooling and returning material device 406 is respectively connected to the second cooling cyclone separation device 405 and the reaction zone of the cooling fluidized bed body. The tail gas discharge port of the second cooling cyclone separation device 405 is also connected to the absorption tower 6, and the tail gas discharge port of the second cooling cyclone separation device 405 is also respectively connected to the pretreatment fluidized bed air inlet structure 101, the purification fluidized bed air inlet structure 201, and the desorption fluidized bed air inlet structure 301.

[0098] This embodiment also uses the purification system to purify the microcrystalline graphite raw material, and the composition of the microcrystalline graphite raw material is shown in Table 2. The method specifically includes:

[0099] S1. Preprocessing.

[0100] Materials and pretreatment gas are introduced into the pretreatment fluidized bed:

[0101] Process operation: Microcrystalline graphite with 90% fixed carbon content is input into the pretreatment fluidized bed to remove highly active amorphous carbon; at the same time, metal impurities are pretreated to facilitate further purification. Process conditions in the pretreatment fluidized bed: reaction temperature: 900°C, powder residence time: 90min; feed rate: 40kg / h, pretreatment gas introduction rate 33kg / h, pretreatment gas includes air and water vapor, with volume concentrations of 60% and 40% respectively. a is 12.6%, extended fluidized bed characteristics, the diameter of the pretreatment fluidized bed body is 0.3m, the fluidization speed is 0.12m / s, the physical and chemical characteristics of extended microcrystalline graphite, the particle size of microcrystalline graphite D50 = 20μm, the particle density is 1500kg / m 3 .

[0102] S2. Purification treatment.

[0103] The material enters the purification fluidized bed from the pretreatment fluidized bed through the two-stage pretreatment intermediate tank. The reaction temperature in the purification fluidized bed is 1100℃, and it is operated at normal pressure or negative pressure. The halogen-containing mixed gas is introduced, and the introduction rate of N2 is 54.4kg / h, and the introduction rate of C12 is 8.7kg / h. The diameter of the purification fluidized bed body is 300mm.

[0104] S3. Desorption treatment.

[0105] The material enters the desorption fluidized bed through the purification intermediate tank of the purification fluidized bed. The reaction temperature in the desorption fluidized bed is 1150°C, and it is operated at normal pressure or negative pressure. N2 is introduced at a rate of 40kg / h. The diameter of the desorption fluidized bed body is 300mm.

[0106] S4. Cooling treatment.

[0107] The material enters the cooling fluidized bed from the desorption fluidized bed through the desorption intermediate tank. The temperature is controlled at normal pressure and N2 is introduced into the cooling fluidized bed body at a rate of 100-200 kg / h. The diameter of the desorption fluidized bed body is 500 mm. The bed material temperature drops from high temperature to below 200°C, and the tail gas in the cooling stage from high temperature to 300°C is returned to the pretreatment fluidized bed and / or purification fluidized bed and / or desorption fluidized bed, and the tail gas below 300°C is discharged into the absorption tower.

[0108] Comparative Example 1

[0109] The method for purifying microcrystalline graphite provided in this comparative example is basically the same as that in Example 1, except that:

[0110] S1. Preprocessing.

[0111] Materials and pretreatment gas are introduced into the pretreatment fluidized bed:

[0112] Process operation: Microcrystalline graphite with 90% fixed carbon content is fed into the pretreatment fluidized bed to remove highly active amorphous carbon; at the same time, metal impurities are pretreated to facilitate further purification. The process conditions in the pretreatment fluidized bed are: reaction temperature: 900°C, powder residence time: 90min; feed rate: 40kg / h, pretreatment gas introduction rate: 28kg / h, pretreatment gas includes air and water vapor, with volume concentrations of 25% and 75% respectively. Oxygen concentration is 5.3%, a is 12.6%, extended fluidized bed characteristics, the diameter of the pretreatment fluidized bed body is 0.3m, the fluidization speed is 0.12m / s, the physical and chemical characteristics of extended microcrystalline graphite, the particle size of microcrystalline graphite D50 = 20μm, the particle density is 1500kg / m 3 .

[0113] Example 2

[0114] The purification system used in this example is the same as that in Example 1.

[0115] The composition of the microcrystalline graphite raw material in this embodiment is shown in Table 2. The microcrystalline graphite purification method in this embodiment is basically the same as that in Example 1, except that:

[0116] S1. Preprocessing.

[0117] Materials and pretreatment gas are introduced into the pretreatment fluidized bed:

[0118] Process operation: Microcrystalline graphite with 98% fixed carbon content is input into the pretreatment fluidized bed to remove highly active amorphous carbon; at the same time, metal impurities are pretreated to facilitate further purification.

[0119] Process conditions in the pretreatment fluidized bed: reaction temperature: 950℃, powder residence time: 60min; feed rate: 60kg / h, pretreatment gas introduction rate of 48kg / h, pretreatment gas includes N2, O2 and water vapor, with volume concentrations of 41.2%, 8.8% and 50% respectively. Among them, a is 8.8%, extended fluidized bed characteristics, pretreatment fluidized bed body diameter 0.3m, fluidization speed 0.18m / s, extended microcrystalline graphite physicochemical characteristics, microcrystalline graphite particle size D50 = 20μm, particle density 1500kg / m 3 .

[0120] Comparative Example 2

[0121] The method for purifying microcrystalline graphite provided in this comparative example is basically the same as that in Example 2, except that: the purification system used in Comparative Example 2 is as follows Figure 2 As shown, the system does not include a pretreatment fluidized bed, and accordingly, the pretreatment process is omitted in the process section.

[0122] Example 3

[0123] The method for purifying microcrystalline graphite provided in this embodiment is basically the same as that in embodiment 2, except that: the purification system used in embodiment 3 is as follows Figure 3 As shown, the system does not include a desorption fluidized bed, and accordingly, the desorption treatment process is omitted in the process section.

[0124] Example 4

[0125] This embodiment provides a purification system comprising only a pretreatment fluidized bed, such as Figure 4 As shown, this embodiment adopts batch processing, and pretreatment, purification, desorption and cooling treatment are successively carried out in the pretreatment fluidized bed.

[0126] The raw materials and operating process in this embodiment are the same as those in Example 2.

[0127] The equipment in this embodiment is simplified, requiring only one fluidized bed, and the production efficiency is obviously greatly reduced. At the same time, it is difficult to avoid the microcrystalline graphite with substandard purity adhering to the wall of the reactor from mixing into the purified product, making it difficult to ensure the stability of the product purity.

[0128] Table 1 Test results of purified microcrystalline graphite products obtained in the examples and comparative examples of the present application

[0129]

[0130] Table 2 Raw material test results

[0131]

[0132] Negative electrode application test case

[0133] The above high-purity microcrystalline graphite samples were processed by asphalt coating, carbonization and other processes to obtain graphite negative electrode materials, and the electrochemical performance was tested. The samples were used as positive electrodes and lithium sheets were used as negative electrodes to build simulated half-cells, and the first-week charge-discharge specific capacity and first-time efficiency of 0.1C charge and discharge were tested.

[0134] Table 3 Electrochemical performance test

[0135]

[0136] Although the present application has been described with reference to illustrative embodiments, it will be appreciated by those skilled in the art that various other changes, omissions, and / or additions may be made and that elements of the described embodiments may be substituted with substantial equivalents without departing from the spirit and scope of the present application. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present application without departing from the scope of the present application. Therefore, it is not intended herein to limit the present application to the disclosed specific embodiments for carrying out the present application, but rather it is intended that the present application will include all embodiments within the scope of the appended claims.

Claims

1. A purification system, characterized in that: include: A pretreatment unit, which is at least used to contact the microcrystalline graphite raw material with an oxygen-containing gas at a first temperature, so as to convert at least a portion of first impurities in the microcrystalline graphite raw material into a first volatile product at least through an oxidation reaction, and at least activate at least a portion of second impurities in the microcrystalline graphite raw material, so as to obtain pretreated microcrystalline graphite; The purification unit is connected to the pretreatment unit and is used at least to contact the pretreated microcrystalline graphite with a halogen-containing gas at a second temperature to convert at least part of the activated second impurities in the pretreated microcrystalline graphite into a second volatile product to obtain purified microcrystalline graphite.

2. The purification system according to claim 1, characterized in that: The pretreatment unit includes at least one pretreatment fluidized bed, which is used to provide an environment for the microcrystalline graphite raw material to contact with an oxygen-containing gas at a first temperature. The purification unit includes at least a purification fluidized bed, which is used to provide an environment for the pretreated microcrystalline graphite to contact with a halogen-containing gas at a second temperature. The pretreatment fluidized bed and the purification fluidized bed are arranged in series.

3. The purification system according to claim 2, characterized in that: The pretreatment unit comprises a plurality of pretreatment fluidized beds, and the plurality of pretreatment fluidized beds are arranged in series and / or in parallel; And / or, the purification unit comprises a plurality of purification fluidized beds, and the plurality of purification fluidized beds are arranged in series and / or in parallel; and / or, the pretreated microcrystalline graphite outlet of the pretreatment fluidized bed is communicated with the purified microcrystalline graphite inlet of the purification fluidized bed; And / or, the pretreatment fluidized bed comprises a pretreatment fluidized bed body and a first pretreatment cyclone separation device, a second pretreatment cyclone separation device, a first pretreatment return device, a second pretreatment return device, a third pretreatment return device, and a pretreatment intermediate tank; The microcrystalline graphite inlet of the pretreatment fluidized bed body is connected to the raw material feed tank, and the microcrystalline graphite outlet of the pretreatment fluidized bed body is connected to the pretreatment intermediate tank. The first pre-treatment cyclone separation device is arranged in the pre-treatment fluidized bed body and is at least used to collect solid particles in the tail gas generated in the pre-treatment fluidized bed body, the second pre-treatment cyclone separation device is arranged outside the pre-treatment fluidized bed body, the second pre-treatment cyclone separation device is also connected in series with the first pre-treatment cyclone separation device, and the second pre-treatment cyclone separation device is at least used to collect solid particles in the tail gas output by the first pre-treatment cyclone separation device; The first pretreatment return device is arranged outside the pretreatment fluidized bed body, and is respectively connected to the microcrystalline graphite outlet and the microcrystalline graphite inlet of the pretreatment fluidized bed body, and returns at least part of the microcrystalline graphite output from the microcrystalline graphite outlet of the pretreatment fluidized bed body back into the pretreatment fluidized bed body; the second pretreatment return device is arranged inside the pretreatment fluidized bed body, and is connected to the first pretreatment cyclone separation device, and is used to return the solid phase material of the first pretreatment cyclone separation device back to the pretreatment reaction zone of the pretreatment fluidized bed body; the third pretreatment return device is arranged outside the pretreatment fluidized bed body, and is respectively connected to the second pretreatment cyclone separation device and the pretreatment fluidized bed body, and is used to return the solid phase material of the second pretreatment cyclone separation device back to the pretreatment fluidized bed body; And / or, the purification fluidized bed comprises a purification fluidized bed body and a first purification cyclone separation device, a second purification cyclone separation device, a first purification return device, a second purification return device, a third purification return device, and a purification intermediate tank; The microcrystalline graphite inlet of the purification fluidized bed body is connected to the raw material feed tank, and the microcrystalline graphite outlet of the purification fluidized bed body is connected to the purification intermediate tank. The first purification cyclone separation device is arranged in the purification fluidized bed body, and is at least used to collect solid particles in the tail gas generated in the purification fluidized bed body; the second purification cyclone separation device is arranged outside the purification fluidized bed body, and the second purification cyclone separation device is also connected in series with the first purification cyclone separation device, and the second purification cyclone separation device is at least used to collect solid particles in the tail gas output by the first purification cyclone separation device; The first purification return device is arranged outside the purification fluidized bed body, and is respectively connected to the microcrystalline graphite outlet and the microcrystalline graphite inlet of the purification fluidized bed body, and returns at least part of the microcrystalline graphite output from the microcrystalline graphite outlet of the purification fluidized bed body back into the purification fluidized bed body; the second purification return device is arranged inside the purification fluidized bed body, and is connected to the first purification cyclone separation device, and is used to return the solid phase material of the first purification cyclone separation device back to the purification reaction zone of the purification fluidized bed body; the third purification return device is arranged outside the purification fluidized bed body, and is respectively connected to the second purification cyclone separation device and the purification fluidized bed body, and is used to return the solid phase material of the second purification cyclone separation device back into the purification fluidized bed body; And / or, the purification system further comprises a condensation tank and an absorption tower, the tail gas discharge port of the pretreatment unit is directly connected to the absorption tower, the tail gas discharge port of the purification unit is connected to the condensation tank, and the condensation tank is connected to the absorption tower.

4. The purification system according to claim 1, characterized in that: The first impurities include carbon-containing impurities, and the second impurities include impurities containing at least metal elements and / or silicon elements, wherein the relationship between the oxygen content a in the oxygen-containing gas, the feed rate m (kg / h) of the microcrystalline graphite raw material, the average flow rate Q (kg / h) of the oxygen-containing gas, the content x of the first impurity in the microcrystalline graphite raw material, the content y of the second impurity, the oxidation coefficient α of the first impurity, and the activation coefficient β of the second impurity satisfies the following formula: aQ=αxm+βym.

5. The purification system according to claim 4, characterized in that: a=1V / V%~30V / V%, the first temperature T=800°C~1100°C, the contact time between the microcrystalline graphite raw material and the oxygen-containing gas at the first temperature t=10min~120min, α=1.0~3.0, β=0.01~0.

05.

6. The purification system according to claim 1, characterized in that: The continuous purification system further comprises at least one of a desorption unit and / or a temperature reduction unit; The desorption unit is connected to the purification unit and is used at least to remove at least part of the second volatile product adsorbed on the purified microcrystalline graphite; The cooling unit is at least connected to the pretreatment unit and / or the purification unit, and is at least used to recover the heat in the gas phase material and / or the solid phase material output by the pretreatment unit and / or the purification unit; And / or, the pretreatment unit, the purification unit, the desorption unit, and the cooling unit are connected in sequence; And / or, the tail gas discharge port of the desorption unit is also connected to the condensation tank, and the tail gas discharge port of the cooling unit is also connected to the absorption tower; And / or, the desorption unit comprises one or more desorption fluidized beds, and a plurality of the desorption fluidized beds are arranged in series and / or in parallel; And / or, the desorption fluidized bed comprises a desorption fluidized bed body and a first desorption cyclone separation device, a second desorption cyclone separation device, a first desorption return device, a second desorption return device, a third desorption return device, and a desorption intermediate tank; The microcrystalline graphite inlet of the desorption fluidized bed body is connected to the raw material feed tank, and the microcrystalline graphite outlet of the desorption fluidized bed body is connected to the desorption intermediate tank. The first desorption cyclone separation device is arranged in the desorption fluidized bed body, and is at least used to collect solid particles in the tail gas generated in the desorption fluidized bed body, the second desorption cyclone separation device is arranged outside the desorption fluidized bed body, the second desorption cyclone separation device is also connected in series with the first desorption cyclone separation device, and the second desorption cyclone separation device is at least used to collect solid particles in the tail gas output by the first desorption cyclone separation device; The first desorption return device is arranged outside the desorption fluidized bed body, and is respectively connected to the microcrystalline graphite outlet and the microcrystalline graphite inlet of the desorption fluidized bed body, and returns at least part of the microcrystalline graphite output from the microcrystalline graphite outlet of the desorption fluidized bed body back into the desorption fluidized bed body; the second desorption return device is arranged inside the desorption fluidized bed body, and is connected to the first desorption cyclone separation device, and is used to return the solid-phase material of the first desorption cyclone separation device back to the desorption reaction zone of the desorption fluidized bed body; the third desorption return device is arranged outside the desorption fluidized bed body, and is respectively connected to the second desorption cyclone separation device and the desorption fluidized bed body, and is used to return the solid-phase material of the second desorption cyclone separation device back to the desorption fluidized bed body; And / or, the cooling unit comprises one or more cooling fluidized beds, and a plurality of the cooling fluidized beds are arranged in series and / or in parallel; And / or, the cooling fluidized bed comprises a cooling fluidized bed body and a first cooling cyclone separation device, a second cooling cyclone separation device, a first cooling return device, a second cooling return device, a third cooling return device, and a cooling intermediate tank; The microcrystalline graphite inlet of the cooling fluidized bed body is connected to the raw material feed tank, and the microcrystalline graphite outlet of the cooling fluidized bed body is connected to the cooling intermediate tank. The first cooling cyclone separation device is arranged in the cooling fluidized bed body, and is at least used to collect solid particles in the tail gas generated in the cooling fluidized bed body, the second cooling cyclone separation device is arranged outside the cooling fluidized bed body, the second cooling cyclone separation device is also connected in series with the first cooling cyclone separation device, and the second cooling cyclone separation device is at least used to collect solid particles in the tail gas output by the first cooling cyclone separation device; The first cooling and returning device is arranged outside the cooling fluidized bed body, and is respectively connected to the microcrystalline graphite outlet and the microcrystalline graphite inlet of the cooling fluidized bed body, and returns at least part of the microcrystalline graphite output from the microcrystalline graphite outlet of the cooling fluidized bed body back into the cooling fluidized bed body. The second cooling and returning device is arranged inside the cooling fluidized bed body, and is connected to the first cooling cyclone separation device, and is used to return the solid-phase material of the first cooling cyclone separation device to the cooling reaction zone of the cooling fluidized bed body. The third cooling and returning device is arranged outside the cooling fluidized bed body, and is respectively connected to the second cooling cyclone separation device and the cooling fluidized bed body, and is used to return the solid-phase material of the second cooling cyclone separation device back to the cooling fluidized bed body.

7. The purification system according to claim 1, characterized in that: The first impurity includes amorphous carbon, the second impurity includes oxides or silicates or carbonates or chlorides or nitrates or fluorides containing at least one element of iron, calcium, aluminum, magnesium, potassium, and sodium, the first volatile product includes pyrolysis gas and / or tar products; the second volatile product includes metal halides and / or silicon halides.

8. A method for purifying microcrystalline graphite, characterized in that: The steps include: S1, contacting the microcrystalline graphite raw material with an oxygen-containing gas at a first temperature to convert at least a portion of the first impurities in the microcrystalline graphite raw material into a first volatile product, and to activate at least a portion of the second impurities in the microcrystalline graphite raw material, to obtain a pretreated microcrystalline graphite. S2. Contacting the pretreated microcrystalline graphite with a halogen-containing gas at a second temperature to convert at least a portion of the activated second impurities in the pretreated microcrystalline graphite into a second volatile product to obtain purified microcrystalline graphite.

9. The method for purifying microcrystalline graphite according to claim 8, characterized in that: The first impurities include carbon-containing impurities, and the second impurities include impurities containing at least metal elements and / or silicon elements, wherein the relationship between the oxygen content a in the oxygen-containing gas, the feed rate m (kg / h) of the microcrystalline graphite raw material, the average flow rate Q (kg / h) of the oxygen-containing gas, the content x of the first impurity in the microcrystalline graphite raw material, the content y of the second impurity, the oxidation coefficient α of the first impurity, and the activation coefficient β of the second impurity satisfies the following formula: aQ=αxm+βym.

10. The method for purifying microcrystalline graphite according to claim 9, characterized in that: a=1V / V%~30V / V%, the first temperature T=800°C~1100°C, the contact time between the microcrystalline graphite raw material and the oxygen-containing gas at the first temperature t=10min~120min, α=1.0~3.0, β=0.01~0.

05.

11. The method for purifying microcrystalline graphite according to claim 8, characterized in that: Specifically include: Using the pretreated microcrystalline graphite or the purified microcrystalline graphite as the microcrystalline graphite raw material, and repeatedly performing the operation of step S1 once or more, until the first impurity content in the obtained pretreated microcrystalline graphite is lower than a first threshold value; And / or, the purified microcrystalline graphite is used as the pretreated microcrystalline graphite, and the operation of step S2 is repeatedly performed one or more times until the second impurity content in the purified microcrystalline graphite is lower than a second threshold value.

12. The method for purifying microcrystalline graphite according to claim 8, characterized in that: Step S1 specifically includes: when the microcrystalline graphite raw material is brought into contact with the oxygen-containing gas at the first temperature, part of the microcrystalline graphite in the microcrystalline graphite raw material is combusted to generate heat.

13. The method for purifying microcrystalline graphite according to claim 8, characterized in that: Also includes: S3. Contacting the purified microcrystalline graphite with a desorption gas at a third temperature to remove at least a portion of the second volatile product adsorbed on the purified microcrystalline graphite.

14. The method for purifying microcrystalline graphite according to any one of claims 11 to 13, characterized in that: Specifically include: The operation of step S1 is performed in at least one pretreatment fluidized bed; and / or the operation of step S2 is performed in at least one purification fluidized bed.

15. The method for purifying microcrystalline graphite according to claim 14, characterized in that: Also includes: S4, exchanging heat between the microcrystalline graphite raw material and / or the oxygen-containing gas and the gaseous phase material and / or the solid phase material output from the pretreatment fluidized bed / or the purification fluidized bed to preheat the microcrystalline graphite raw material and / or the oxygen-containing gas, and then inputting the preheated microcrystalline graphite raw material and / or the oxygen-containing gas into the pretreatment fluidized bed to perform step S1; And / or, the pretreated microcrystalline graphite and / or the halogen-containing gas are heat exchanged with the gaseous substance and / or solid-phase substance output from the pretreatment fluidized bed and / or the purification fluidized bed to preheat the pretreated microcrystalline graphite and / or the halogen-containing gas, and then the preheated pretreated microcrystalline graphite and / or the halogen-containing gas are input into the purification fluidized bed to perform step S2.

16. The method for purifying microcrystalline graphite according to claim 8, characterized in that: The first impurity includes amorphous carbon, the second impurity includes oxides or silicates or carbonates or chlorides or nitrates or fluorides containing at least one element of iron, calcium, aluminum, magnesium, potassium, and sodium, the first volatile product includes pyrolysis gas and / or tar products; the second volatile product includes metal halides and / or silicon halides.

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