This article describes the definition of cathode carbon block and its classification as well as the process flow of carbon block.
Key words: cathode carbon block; classification; process flow
Cathode carbon block is a carbon block made of high-quality anthracite, coke, graphite, etc. Used as the cathode of aluminum electrolytic cell. Including bottom carbon block, side carbon block, tamped carbon paste or carbon glue connected with carbon block and cathode steel rod, etc.
Bottom carbon block
It plays the dual role of conducting electricity and forming the inner lining of the electrolytic tank. It is built on the bottom of the electrolytic tank, and the outside is built with refractory materials and reinforced with a steel shell. It can be divided into ordinary cathode carbon blocks, semi-graphite cathode carbon blocks and graphite cathode carbon blocks.
* Ordinary cathode carbon block is made directly from ordinary calcined anthracite without graphitization process;
*Semi-graphite cathode carbon blocks, one is made of electric calcined anthracite or more graphite powder or even all graphite powder, and the formed green body is only roasted (roasting temperature does not exceed 1200 ℃), called semi-graphite Carbon block; the other uses easily graphitizable coke as a raw material, and after the green body is roasted, it is heat treated for graphitization (1800~2000°C), also known as semi-graphitic (chemical) cathode carbon block;
*Graphite cathode carbon block, with easy graphitization coke as raw material, its graphitization temperature should reach about 2500℃, also known as graphite cathode carbon blocks.
*The new type of bottom carbon blocks includes titanium boride coated carbon blocks, which is to apply a coating made of titanium boride to the surface of the cathode carbon blocks body, or directly press a layer of carbon paste containing titanium boride on the surface of the carbon blocks layer, followed by firing heat treatment. The bottom carbon blocks accounts for 60%~70% of the cathode material of the aluminum electrolytic cell.
Side carbon block
It is used to build the side of the aluminum electrolytic cell to form the main body of the side lining of the electrolytic cell. It can be divided into ordinary side carbon blocks and semi-graphitic side carbon blocks, and the production and preparation methods are similar to bottom carbon blocks. With the popularization and application of silicon nitride combined with silicon carbide block on the side of the aluminum electrolytic cell, the amount of carbon block on the side has been reduced.
The product that connects the cathode carbon blocks and the cathode busbar in the aluminum electrolytic cell to form the cathode circuit of the aluminum electrolytic cell. Divided into single-rod assembly (that is, a cathode carbon block is assembled with a cathode steel rod) and double-rod assembly (that is, two cathode steel rods are assembled at the end of a cathode carbon blocks).
The raw materials of the cathode carbon blocks are mainly anthracite, pitch coke, natural and artificial graphite and coal tar pitch, etc. The raw materials are calcined, crushed and screened into a certain particle size, and the binder is added to knead according to the formula, and the finished kneading is the finished cathode. paste. The kneaded paste is produced into a cathode carbon blocks through processes such as molding, roasting, even graphitization, and machining.