Coal was heat-treated up to the softening temperature under the 2 types of heating conditions (10°C/min, 104°C/min). Spin concentration by high temperature Iusitu ESR, and the saturation behavior of the ESR spectrum were measured. Based on that result, effect of rapid preheating on coal molecular structure was examined. (1) Because the change in coal chemical structure by the cracking reaction is taking place, spin concen-tration of slow preheated coal is higher than that of rapidly preheated coal and raw coal. At 300°C or more, the spin concentration of rapidly preheated coal is same profile as raw coal. In the case of rapid preheating, it is indicated that the degree of coal structure change by cracking reaction is small. (2) The following results were obtained as the saturation power of ESR was measured. At 250°C or more, the saturation power of slow preheated coal declines as the temperature rises. One side, it confirmed that the saturation power of rapidly preheated coal became large at 370°C. The increase in saturation power indicates that the relaxation of coal structure progressed about coal molecular structure part that can be observed with ESR.
To understand behavior of trace elements in high temperature coal gasification accompanied with molten ash, the chemical compounds were estimated by thermodynamic equilibrium calculation. The calculation results were compared with the test results of a high temperature and pressurized coal gasification pilot plant with partial combustion. As for distribution of trace elements in slag discharged from pre-combustor, in the char separated by char collector and the product gas containing the fly ash, the estimated results for almost of non-volatile and some of volatile elements were corresponding to the test results well and those for semi-volatile elements as Mn, Cr, Pb, As and volatile elements as Hg and F were not well. The equilibrium calculation results of chemical compounds related to the semi-volatile elements suggested that the slagliquid phase exists together with solid phase in the char and the fly ash while the compounds in the molten slag discharged from the high-temperature gasifier over 1600°C were all slag-liquid phases. Furthermore, study on influence of operating condition on the chemical compounds suggested that increasing temperature of pre-combustor decreased the semi-volatile elements such as Pb in slag and increased it in char. Pressure increased it in slag and decreased it in other discharged. Gas cooling temperature strongly influenced the behavior, increased the semi-volatile elements in product gas and decreased it in slag and char.