Weight Loss and Tar Evolution during Coal Devolatilization at Various Heating Rates

Temperature-resolved weight loss and tar yield during atmospheric devolatilization of pulverized coal have been obtained on a wire mesh reactor (WMR), which imposes prescribed thermal histories covering a wide range of heating rates on coals from lignite to anthracite. The accuracy of measurements has been improved by diminishing non-isothermality in the sample, ensuring independence of yields on loading density, and the development of a convenient tar collection method that inhibits secondary pyrolysis but also secures capture completeness. We reconfirm the continuous rank effects in terms of reaction dynamics and partitioning between tar and non-condensables but at disparate heating rates of 5 and 1000 K/s. In addition, we depict the constant variation in gas evolution histories among various coals before the cessation of tar release, whereas since the end of tar evolution, variations in gas formation kinetics for different coals gradually shrink with increasing temperatures. A larger fraction of total gases is found expelled after tar evolution by coals of higher rank. The sensitivity of the tar yield to heating rate is maintained the same over the range of 5–1000 K/s but varies with rank, being greatest for lignites and low-volatile bituminous coals but exhibiting a minimum for high-volatile bituminous coals