What is graphitization? The so-called graphitization refers to the transformation of non graphite carbon into graphite carbon with a three-dimensional regular ordered structure after high-temperature heat treatment. Originating from the carbon product industry, it is a necessary process for producing graphite electrodes. The graphitization process is aimed at improving the thermal and electrical conductivity of carbon materials, enhancing their thermal shock resistance and chemical stability, giving them lubrication and wear resistance, and improving their purity. The use of high-temperature heat treatment provides energy for atomic rearrangement and structural transformation, which requires a significant amount of energy consumption. Electricity is the main energy consumed in graphitization production. Generally, electric heating is used to heat semi-finished products to above 2800 ℃, which results in a large scale and long time consumption of electricity. According to statistics, the cost of graphitization accounts for approximately 55% of the manufacturing cost of artificial graphite negative electrodes.

The graphitization process can be divided into direct and indirect methods according to heating methods, and intermittent and continuous methods according to operating methods. Common negative electrode graphitization furnaces include Acheson graphitization furnace, internal series graphitization furnace, grid box graphitization furnace, etc.

1. Mixing of volatile components during furnace loading

During the period when the temperature inside the graphitization furnace rises to 200-1000 ℃, a large amount of volatile matter will be discharged from the negative electrode inside the furnace. If not discharged in time, it may cause the accumulation of volatile matter and lead to safety accidents in the spray furnace. When a large amount of volatile matter escapes, insufficient combustion of volatile matter can produce a large amount of black smoke, causing environmental pollution or accidents. Therefore, the following points should be noted when loading the furnace:

(1) When installing the negative electrode in the furnace, it is necessary to match it reasonably according to the content of volatile matter, to avoid excessive concentration and concentrated escape of high volatile matter during the power transmission process;

(2) Appropriate ventilation holes should be installed on the top insulation material to facilitate the effective escape of volatile matter;

(3) When designing the power transmission curve, it is necessary to fully consider the stage of concentrated emission of volatile matter. The curve should be slowed down appropriately, so that the volatile matter is slowly discharged and fully burned;

(4) Reasonably select auxiliary materials, ensure the particle size composition of auxiliary materials, reduce the amount of 0-1mm powder in auxiliary materials, generally accounting for ≤ 10%.

2. Uniform furnace resistance is required during furnace loading

When the distribution of negative electrodes and resistance materials in the furnace is uneven, the current will flow through the areas with low resistance, causing a bias phenomenon and affecting the graphitization effect of the entire furnace negative electrode. Therefore, when installing the furnace, the following points need to be noted:

(1) When installing the furnace, the resistance material should be discharged from the head of the furnace to the tail of the furnace to avoid the concentration of small or large particles;

(2) When new and old crucibles are loaded into the same furnace, a reasonable combination is also necessary. It is forbidden to load a new crucible with one layer and an old crucible with one layer;

(3) Avoid exposing the resistance material to the side wall material.