Like cathode carbon block, the aggregate of cathode paste mainly uses high-quality electric calcined anthracite as raw material. At present, it mainly uses anthracite of high quality in Taixi Town, Ruqigou, Shizuishan City, Ningxia, which is called Taixi Coal. Taixi Coal has the characteristics of “three bottoms and six highs” (bottom ash, bottom sulfur, bottom phosphorus, high calorific value, high specific resistance, high lump coal rate, high chemical activity, high clean coal recovery rate, and high mechanical strength), which is the highest quality coal in China. There are also those who use high-quality electric calcined (generally not using gas calcined) anthracite from other regions as aggregate, but Taixi Coal is the first to be used as aggregate.
In Table 1, the paste is divided into two categories: semi graphite and high graphite according to the different graphite content (in some data reports, the high graphite cold rammed paste is made of 25% graphite). In actual production and use, it is necessary for steel bar paste and carbon paste to contain graphite, but it is not necessary for the surrounding paste to contain graphite. The paste around the international standard cold rammed paste is not mixed with graphite material.
In addition to using different raw materials for different pastes, the most important thing is to use different binders. Generally, coal tar pitch is used as the binder for hot ramming paste, which can meet the requirements of electrolytic cell as long as it is correctly operated according to the regulations during construction. The cold ramming paste uses specially refined high-quality coal tar as the binder, but the binder used by most domestic enterprises to manufacture the cold ramming paste is to add anthracene oil or coal tar into the coal tar, and adjust the softening point of the coal tar to the temperature required by the cold ramming paste or warm ramming paste respectively. This method of preparing binder is because these manufacturers do not master the technology of Cold ramming binder. Because the softening point of coal tar pitch can be reduced by adding anthracene oil or coal tar, not only the environmental protection index can not meet the requirements, but also the shrinkage of the paste increases due to the evaporation of anthracene oil and coal tar during baking, which increases the risk of aluminum leakage in the electrolytic cell. The author believes that the paste of the electrolytic cell is either hot rammed paste or cold rammed paste produced by using a binder not mixed with anthracene oil and coal tar. The so-called “warm mashing” is also undesirable.