CN-117658125-B - Method for preparing battery grade graphite by utilizing aluminum electrolysis waste cathode

Abstract

The invention provides a method for preparing battery grade graphite by utilizing an aluminum electrolysis waste cathode, which comprises the steps of mixing crushed and ground waste cathode carbon powder with an alkaline solution to prepare mixed slurry, performing hydrothermal reaction, filtering to obtain an alkaline leaching waste cathode and alkaline filtrate, mixing a dried alkaline leaching waste cathode with an acidic solution to prepare mixed slurry, performing heating reaction, filtering to obtain an acid leaching waste cathode and acidic filtrate, and roasting and graphitizing the dried acid leaching waste cathode to obtain purified graphite carbon powder. According to the method, the economic value of the aluminum electrolysis waste cathode calcined carbon block can be effectively improved, after the remaining impurities and graphitization are reasonably removed, graphite carbon powder meeting the I-level standard of the graphite type negative electrode material artificial graphite of the lithium ion battery can be obtained, and alkali liquor and acid liquor can be recycled in the reaction process, so that the method is a new environment-friendly process technology with high economic benefit, can effectively solve the problem that the waste cathode in the aluminum electrolysis industry of China is difficult to utilize currently, and provides a new artificial graphite approach for the lithium ion battery.

Inventors

• YANG JIYUAN

Assignees

• 中科浩鼎科技集团股份有限公司

Dates

Publication Date

20260512

Application Date

20231211

Claims (4)

1. 1. I, mixing crushed and ground waste cathode carbon powder with alkaline solution to prepare mixed slurry, performing hydrothermal reaction, and filtering to obtain alkaline leaching waste cathode and alkaline filtrate; II, mixing the dried alkaline leaching spent cathode with an acid solution to prepare mixed slurry, heating for reaction, and filtering to obtain an acid leaching spent cathode and an acid filtrate; III, roasting and graphitizing the dried acid leaching waste cathode to obtain purified graphite carbon powder; The waste cathode carbon powder is a product of waste cathode carbon blocks subjected to anaerobic roasting defluorination treatment at a temperature of more than 1500 ℃, the carbon content is more than or equal to 85wt% and the fluorine content is less than or equal to 0.3wt%; The hydrothermal reaction temperature in the step I is 160-260 ℃ and the reaction time is 1-6 h; the acid in the acid solution in the step II is one or more of hydrochloric acid, nitric acid, sulfuric acid, carbonic acid and phosphoric acid; the reaction temperature in the step II is 30-90 ℃ and the reaction time is 1-6 h; The roasting temperature in the step III is 1900-3000 ℃, and the roasting time is 30-300 min; and in the step III, the graphitization degree of the purified graphite carbon powder is more than or equal to 90%, and the fixed carbon content is more than or equal to 99.7wt%.
2. 2. The method for preparing battery grade graphite by utilizing the aluminum electrolysis waste cathode according to claim 1, wherein the alkaline substance in the alkaline solution in the step I is one or more of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide.
3. 3. The method for preparing battery grade graphite by utilizing the aluminum electrolysis waste cathode as claimed in claim 1, wherein the alkaline solution in the mixed slurry in the step I is mixed with waste cathode carbon powder according to the mass ratio of (3-12)..1, and the concentration of alkali liquor is 1-12 mol/L.
4. 4. The method for preparing battery grade graphite by utilizing the aluminum electrolysis waste cathode as claimed in claim 1, wherein the acid solution in the mixed slurry in the step II is mixed with waste cathode carbon powder according to the mass ratio of (3-20)..1, and the concentration of the acid solution is 1-6 mol/L.

Description

Method for preparing battery grade graphite by utilizing aluminum electrolysis waste cathode Technical Field The invention belongs to the field of solid waste treatment, and particularly relates to a method for preparing battery grade graphite by utilizing an aluminum electrolysis waste cathode. Background The cathode of the aluminum electrolysis cell is continuously eroded by substances such as high-temperature molten salt, molten aluminum, sodium metal and the like in the operation process, the cathode crack is generated, the conductivity is changed, the damage of the electrolysis cell is caused, the cell is required to be stopped and overhauled after 3-10 years, and the generated solid waste is the waste cathode of the aluminum electrolysis. The problem of high-value utilization of valuable carbonaceous materials in the waste cathode and the problem of environmental pollution caused by a large amount of toxic substances fluoride and cyanide become bottleneck problems of the aluminum electrolysis industry which restrict the rapid development of China. The existing treatment process of the spent cathode mainly comprises wet treatment and pyrogenic treatment. Chinese patent CN200810231562.1 discloses a harmless treatment and recovery process of cyanide and fluoride in aluminum electrolysis overhaul slag, waste cathode is mixed with soluble calcium/magnesium salt, calcium hypochlorite/magnesium/sodium salt can be respectively dissolved in water, filtrate is recycled after solid-liquid separation, and solid can be used as an additive in a building material or a third party production process, and the technology has the problems of low economic utilization value and difficulty in popularization. Chinese patent CN202211690488.6 discloses a method for comprehensively recycling aluminium electrolysis waste cathode water leaching-pressurizing purification, which comprises the steps of heating and leaching waste cathode, water and hydrogen peroxide, leaching the filtered solid with concentrated sulfuric acid under high pressure, adding concentrated sulfuric acid, concentrated hydrochloric acid, hydrogen peroxide and aqueous solution into the filtered residue after solid-liquid separation, mixing, and carrying out second high pressure acid leaching, wherein the solid-liquid separation can obtain artificial graphite with 97% of fixed carbon content, but the requirement of 99.7% of fixed carbon content of battery grade graphite is not met, and further purification and utilization are needed. Chinese patent CN202211734447.2 discloses a method for preparing graphite material and intermediate frequency roasting furnace in ultra-high temperature reducing atmosphere, which comprises the steps of placing waste cathode material into intermediate frequency roasting furnace, carrying out ultra-high temperature roasting under inert atmosphere, producing crude graphite product after multi-stage treatment of a first stokehold, a second stokehold, a preheating section, a high temperature section, a cooling section, a water cooling section and a discharger, purifying and magnetically separating, wherein the process flow is complicated, and the fixed carbon content in graphitization is still only about 97%. CN200610086890.8 discloses a method for treating waste refractory materials of aluminum electrolysis cells, which comprises the steps of mixing and grinding waste cathodes, sand, lime and fly ash, sintering for 30-60min at 1000-1250 ℃, cooling, adding magnesia, mixing and grinding to obtain powdery anti-penetration refractory materials containing calcium fluoride, calcium aluminosilicate and the like. The method fully utilizes carbon sites in the waste cathode, and the generated refractory material has low added value. The industry starts from 1946, and a great deal of research and development work is done in various countries, especially the united states, and various waste cathode carbon block treatment processes are developed. The related research work in China starts later, starts from about the 90 th century of the 20 th century, is mainly in the laboratory research stage at present, and has few industrialized and semi-industrialized treatment processes. The aluminum electrolysis waste cathode is listed as hazardous waste in national hazardous waste directory published by the national environmental protection agency in 2016. The green mining development concept is an important part of sustainable development of industrial health in China, and the important part is that we need to reasonably utilize valuable tailings wastes in the mineral processing process. Therefore, the development of a new harmless high-value utilization of the aluminum electrolysis waste cathode has important significance. Disclosure of Invention The invention provides a method for preparing battery grade graphite by utilizing an aluminum electrolysis waste cathode, which comprises the steps of carrying out hydrothermal reaction on waste cathode carbon b