EFFECTIVE THERMAL-CONDUCTIVITY OF ISOTROPIC FORMED GREEN CARBON DURING CARBONIZATION PROCESS

Temperature dependency of the effective thermal conductivity of isotropic formed green carbon during carbonization is estimated of the basis on that of packed green carbon before forming. The formed green carbon is regarded as a porous material containing micropores. The packed green carbon during carbonization successively changes its structure from that of a packed bed of particles initially to that of a porous body after going through that of a consolidated body. The thermal conductivity of gaseous tar, which is necessary to determine that of gas phase, is obtained from some physical properties of the gas species of which liquid tar is composed. Porosity of the specimen and molar fractions of the gases released by pyrolysis are experimentally determined. The effective thermal conductivity is measured by using the hot-wire method while the specimen is heated from room temperature to about 1000 K at a constant heating rate of 1 K/min. Estimated effective thermal conductivity for two kinds of formed green carbons agrees well with the respective measured values over a wide range of temperature.