Transient model of a moving-bed coal gasifier

A transient model for air- and oxygen-blown, moving-bed coal gasifiers has been developed, and the use of the model shows good agreement with available steady-state data. It was found that the major factors affecting transient performance are the amount of thermal energy stored in the coal bed, and the rate of drying and devolatilization of the raw coal near the top of the gasifier. It was also found that the gas-heating value rapidly increases as the rate of blast input decreases. The scope of this study was limited to obtaining transient response of the output gas, when changes are made in input blast conditions. Since the model is not intended to produce detailed information of processes occurring within the gasifier, many of the complicated processes are approximated. Two major approximations of this model are that extremely short-duration transient effects are approximated as instantaneous, and long-duration effects are approximated as being constant. 2 refs.