The Structural Analysis of Rapid Preheated Coal Using ESR Spectroscopy

Abstract

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.