Kinetics of coal gasification

This work reports on a kinetic study on the gasification of Brazilian mineral coal with steam using a thermobalance. The coal is a high ash content (>50 wt %) subbituminous, run of mine coal (Charqueadas). Isothermal runs were made at temperatures between 800 and 1000/degree/C and at atmospheric pressure, using -14 +20 mesh Tyler size particles. The coal was devolatilized before the gasification. Initially, the influence of the particle size of coal and the flow of steam were studied in order to determine if diffusive effects are important. For certain conditions these effects are negligible and chemical reaction is the rate controlling step. The experimental results are well described by the unreacted core model above 850/degree/C and by the continuous model below this temperature. The gaseous products were determined at different times and temperatures and contained essentially H/sub 2/, CO, and CO/sub 2/. Comparison of the results with other data published shows that this coal is highly reactive. 15 refs.