DEVELOPMENT OF CONTINUOUS SOLVENT EXTRACTION PROCESSES FOR COAL DERIVED CARBON PRODUCTS

The purpose of this DOE-funded effort is to develop continuous processes for solvent extraction of coal for the production of carbon products. These carbon products include materials used in metals smelting, especially in the aluminum and steel industries, as well as porous carbon structural material referred to as ''carbon foam'' and carbon fibers. There are a number of parameters which are important for the production of acceptable cokes, including purity, structure, density, electrical resistivity, thermal conductivity etc. From the standpoint of a manufacturer of graphite electrodes such as GrafTech, one of the most important parameters is coefficient of thermal expansion (CTE). Because GrafTech material is usually fully graphitized (i.e., heat treated at 3100 C), very high purity is automatically achieved. The degree of graphitization controls properties such as CTE, electrical resistivity, thermal conductivity, and density. Thus it is usually possible to correlate these properties using a single parameter. CTE has proven to be a useful index for the quality of coke. Pure graphite actually has a slightly negative coefficient of thermal expansion, whereas more disordered carbon has a positive coefficient