ESTIMATING THE COMBUSTIBILITY OF VARIOUS COALS BY TG-DTA

To estimate the combustibility of 12 different coals involving anthrac ite, bituminous, and lignite, experiments of the, coal combustion were carried out by using thermogravimetry (TG) and differential thermal a nalysis (DTA). High-reactivity combustibles region and low-reactivity combustibles region were observed during coal char combustion process. Also, two reaction rate constants (k(1) and k(2)) for these two combu stibles were determined. The value of the reaction rate constant of th e low-reactivity combustibles (k(2)) is much smaller than that of the high-reactivity combustibles (k(1)) in each coal and also ka shows low er temperature dependence. These are reasons why 5-10% unburned carbon remains in the ash discharged from most of the coal-fired power plant s. The ignition temperature increases with decreasing volatile matter content of coal. Three ranks of coals as anthracite, bituminous, and l ignite show the different ignition ways.