Experimental Study of Combustion Characteristics of Bituminous Char Derived under Mild Pyrolysis Conditions

摘要

The combustion characteristics of chars derived from a bituminous coal (Datung, also denoted as DT) at different pyrolysis temperatures were studied via simultaneous thermal analysis (STA). The chars were obtained at pyrolysis temperatures of 550,650,750, and 850 ℃. The carbon structure of chars and the parent coal were characterized using X-ray diffraction. Pore structures of chars and parent coal were measured by nitrogen adsorption. Based on the thermogravimetric analysis results, the ignition behavior and reactivity of the chars and the parent coal, as well as those of Yangquan (YQ) anthracite, were compared. The ignition temperature (T_i) and weighted mean apparent activation energy (E_m) were obtained and used to evaluate reactivity. The results show that the ignition type of the bituminous parent coal and chars derived at 550, 650, and 750 ℃ is predominately hetero-homogeneous, whereas that of char derived at 850 ℃ and the YQ anthracite is heterogeneous. Thermal deactivation was observed under the pyrolysis conditions in this work. The reactivity of all chars is lower than that of the parent coal but higher than that of Yangquan anthracite. Moreover, the char that was derived at 650 ℃ has the highest reactivity among all chars. Carbon structure ordering contributes more to the thermal deactivation at high temperatures than at low temperatures. Changes in pore structure and material composition affect the reactivity for chars derived from both low and high temperatures.