With high quality anthracite, coke, graphite as raw materials made of carbon block. Used as cathode of aluminium electrolytic cell. It is built at the bottom of the electrolytic cell, also known as the bottom carbon block. The cathode carbon block plays a dual role of conducting electricity and forming the inner lining of the electrolytic cell. The cathode carbon block is required to have high temperature resistance in aluminum electrolysis production, resistant to molten salt erosion, good electrical and thermal conductivity, high mechanical strength, good thermal shock resistance and strong corrosion resistance of sodium, which is conducive to energy saving and tank life improvement in the production of aluminum electrolysis.
According to the quality requirements of the products, the raw materials selected and the technological conditions used, the cathode carbon blocks in China are basically divided into three categories: ordinary cathode carbon blocks, semi-graphitic carbon blocks and graphitic carbon blocks. Anthracite calcined at 1250 ~ 1350℃ is used as the main raw material for common cathode carbon block. The half graphite carbon block is divided into two kinds according to the different production process.
Another kind of coke with more easy graphitization as aggregate, raw products after roasting and then into graphitization furnace at 1800 ~ 2000℃ temperature for heat treatment, this kind of carbon block is called half graphite (chemical) carbon block.
The former has higher strength and hardness, while the latter has better conductive property and overall effect. Graphite carbon block, with easy graphitization coke as raw material, graphitization treatment temperature should reach about 2500℃.The difference between half graphitic carbon block and graphite carbon block lies in the degree of orderly arrangement of the crystal lattice of the products, that is, the degree of graphitization is different. The degree of graphitization can be indicated by the resistivity of the product. The lattice of the graphite carbon block is almost in the state of ordered arrangement, and the resistivity is less than 15μΩm;The degree of graphitization of semi-graphitized carbon blocks is low or only partly graphitized, and the resistivity is 15 ~ 45μΩM.The maximum heat treatment temperature of half graphitic carbon block is about 2000℃, and the graphitic treatment temperature of graphitic carbon block is 2500 ~ 2800℃.
Common cathode carbon block, resistivity 50 ~ 60μΩM.Graphitized cathode is a conductive material used for cathode of aluminum electrolytic cell, which represents the development direction of electrolytic aluminum industry. With the technological progress and development of electrolytic aluminum industry, the electrolytic cell is developing towards a large capacity of more than 300kVA, and the requirements for cathode materials are higher. The main advantages of graphitized cathode are to strengthen current, improve current efficiency, achieve the purpose of increasing production and saving energy, and make the electrolytic cell run stably. The larger the cell type is, the more obvious the operation stability effect is, and the more obvious the improvement of current efficiency is. The unit capacity of aluminum electrolytic cell using graphitized cathode is increased by 10-15%, and the power saving per ton of aluminum is more than 600kWh.Graphite cathode aluminum electrolytic cell is one of the priority materials in the electrolytic aluminum industry due to the obvious effect of energy saving, consumption reduction and emission reduction.