Transient gasification and syngas formation from coal particles in a fixed-bed reactor

An experimental investigation on gasification and syngas formation from coal particles in a fixed-bed reactor is conducted; particular attention is paid to the transient reaction dynamics. Three different coals, including two high-volatile coals and a low-volatile coal, are taken into consideration. In the initial reaction period, a two-stage reaction is clearly observed; specifically, an exothermic reaction followed by an endothermic reaction is exhibited. Meanwhile, seeing that the devolatilization and pyrolysis reactions are pronounced. the initial concentrations of H-2 and CH4 are relatively high, especially for the former. With increasing time, the interaction between coal and char particles is dominated by the latter, the concentrations of CO and CO, thus become higher. From the observation of syngas combustion, the entire gasification intensity proceeds from intensified growth, rapid decay, and then to progressive decay with increasing reaction time. For the two high-volatile coals, the mass depletion is enhanced markedly once the reaction temperature is as high as 1000 degrees C, whereas it is insensitive to the temperature for the low-volatile coal. Nevertheless, it is found that, based on the weights of moisture and volatile matter, their relative release ratio from the low-volatile coal is better than that from the high-volatile coals. This implies that the final devolatilization and pyrolysis extent is not determined by coal grade. Copyright (C) 2006 John Wiley & Sons, Ltd.