Mathematical model for stratified downdraft gasifiers

A pyrolysis model is described which yields gas temperature and composition for both air and oxygen. The results of this model are then input into a separate char gasification model which utilizes no adjustable parameters to predict design parameters and gasifier process conditions. The two models yield realistic temperature profiles of the solid and gas phases down the reactor. Predictions compare very well laboratory data. The CO/CO/sub 2/ ratio predicted agree well with laboratory data. The model shows an essentially linear correlation between throughput and char conversion for a given reactor length, predicts equivalent conversions of char for various surface to volume ratios of the same feedstock, and demonstrates the buffering effect of the endothermic gasification reactions in keeping down the char temperature in an oxygen gasifier. (1 table, 6 figs., 4 refs.)