Cathode carbon block is a carbon block made of high-quality anthracite, coke and graphite. Used as a cathode of an aluminum electrolytic cell. Including bottom carbon block, side carbon block, tamped carbon paste or carbon glue connected with carbon block and cathode steel rod.
1. Bottom carbon block. It plays the dual role of conducting electricity and forming the inner lining of the electrolytic cell. It is laid at the bottom of the electrolytic cell, and the refractory material is laid outside and reinforced with steel shell. It can be divided into ordinary cathode carbon block, semi graphite cathode carbon block and graphite cathode carbon block.
*Ordinary cathode carbon block is directly made from ordinary calcined anthracite without graphitization;
*Semi graphitic cathode carbon block: one kind of semi graphitic carbon block is made of electric calcined anthracite or more graphite chips or even all graphite chips, and the shaped green body is only roasted (the roasting temperature is not more than 1200 ℃), which is called semi graphitic carbon block; The other is graphitized (1800-2000 ℃) heat treatment with graphitized coke as raw material after green body roasting, which is also called semi graphitized cathode carbon block;
*Graphite cathode carbon block is made of graphitized coke, and its graphitization temperature should reach about 2500 ℃, also known as graphite cathode carbon block.
*The new type of bottom carbon block includes titanium boride coated carbon block, which is to coat the surface of cathode carbon block with coating made of titanium boride, or directly press a layer of carbon paste containing titanium boride on the surface of carbon block, and then conduct baking heat treatment. The bottom carbon block accounts for 60% ~ 70% of the cathode material of the aluminum reduction cell.
2. Side carbon block. It is used to build the side of the aluminum electrolytic cell and constitutes the lining body of the side of the electrolytic cell. It can be divided into ordinary side carbon block and semi graphite side carbon block. The production and preparation method is similar to the bottom carbon block. With the promotion and application of silicon nitride combined with silicon carbide block at the side of aluminum reduction cell, the amount of carbon block at the side is reduced.
3. Cathode steel bar. The products connecting the cathode carbon block and the cathode bus in the aluminum reduction cell form the cathode circuit of the aluminum reduction cell. It is divided into single rod assembly (i.e. one cathode steel rod is assembled on one cathode carbon block) and double rod assembly (i.e. two cathode steel rods are assembled on the end of one cathode carbon block).
The raw materials of cathode carbon block are mainly anthracite, bituminous coke, natural and artificial graphite and coal tar pitch. The raw materials are calcined, crushed and sieved into a certain particle size. After being measured according to the formula, the binder is added for kneading, and the finished cathode paste is obtained after kneading. The kneaded paste is produced into cathode carbon blocks through molding, baking, even graphitization, machining and other processes.