Graphitization, that is, the heat treatment of graphite products, enables the originally disordered carbon atoms to be arranged in order through high temperature. The graphitization process is a process in which the carbon material changes from the two-dimensional structure of the carbon network to the three-dimensional ordered structure through the growth of “microcrystals” under the action of high temperature. Graphitization process is an important process for the production of carbon graphite materials, and graphitization degree is an important indicator of its processing materials.
The graphitization temperature can be roughly divided into two stages. The first stage is between 1000-1800 ° C, and the second stage is between 1800-3000 ° C. above 2000 ° C is the key stage of carbon atom microcrystalline structure change. Different graphite materials have different temperatures for graphitization.
Graphitization can be divided into direct method and indirect method according to heating mode, and can be divided into intermittent type and continuous type according to operation mode. To graphitize the material, we need to use the processing equipment – graphitization furnace.
Graphitization equipment can be divided into two categories according to different ways: direct heating furnace and indirect heating furnace. The direct heating furnace directly uses the material to be heated as the heating element; The indirect heating furnace is that the material is only the heat receiver, and the heat comes from the heating body around the material.
According to the operation design mode, it can be divided into five main types: Acheson graphitization furnace, inner string graphitization furnace, vacuum graphitization furnace, continuous graphitization furnace and box type graphitization furnace.
The graphitization processing cost is mainly affected by direct materials such as crucibles and resistance materials, labor costs, depreciation, and water and electricity costs, of which electricity accounts for the highest proportion, accounting for about 60% of the graphitization cost. Generally, 1 ton of graphitization capacity requires 12000-14000 kwh of electricity, and graphitization is a high-energy consumption process.
The graphitization production cycle and construction cycle are both long. Generally, the production cycle takes about one month, while the construction cycle takes at least half a year to one year. Therefore, the release cycle of graphitization capacity is long.
Due to the low unit electricity price, Inner Mongolia is an important gathering place of domestic graphitization capacity, accounting for about 46% of the national total capacity. The remaining capacity is distributed in Sichuan, Shanxi, Yunnan and other regions. Due to the energy consumption control policies of local governments, the pressure of environmental impact assessment, frequent power restrictions and the rise of electricity charges, the release and expansion of graphitization capacity are not as expected, and the operating rate of enterprises is also limited to a certain extent, resulting in a widening supply gap and a record high price.
Graphitization is a key process in the production of graphite electrode and artificial graphite negative electrode materials. The graphitization processing cost of the electrode is lower than that of the negative electrode. Through continuous price adjustment, the current large DC graphitization processing cost is 5200 yuan / ton, and the average graphitization processing cost of the negative electrode is 22000-26000 yuan / ton. There is still room for subsequent price increase.