Coal structure and Caking Property of Coal Oxidized at 373-673K

摘要

Caking properties of coal are strongly affected by low-temperature oxidation. In this study, the low-temperature oxidations of four coals ranging from brown coal to bituminous coal were investigated. The coal oxidation was carried out using ~(16)O_2 or ~(18)O_2. The caking properties extremely decreased by an increase in the oxygen content of only less than 1wt%. Isotope ~(18)O_2 was used for the oxidation experiment of coal to clarify the release behavior of oxygen-containing gases during the devolatilization of oxidized coal. During the oxidation of coal and the temperature-programmed heat-treatment of oxidized coal, CO (m/z=28,30), CO_2 (m/z=44,46,48) and H2O (m/z=18,20) were analyzed with a quadrupole mass spectrometer. It was found that the gas release profiles were depended on the coal rank. When the oxidized bituminous coal was pyrolyzed at 10°C /min up to 500°C, much more C~(18)O~(18)O, C~(19)O~(18)O, H_2 ~(18)O were released than those from raw coal just before softening temperature of raw coal. The coal structure changes that may be due to cross-linking and the decrease in hydrogen donor ability of oxidized coal strongly affected the caking property of coal.