Pulverized Coal Combustion. Final Report, December 17, 1981-June 17, 1983

摘要

Coal oxidation studies have been performed with Montana Rosebud, Illinois No. 6, Utah Bituminous coals, and a char derived from the Utah coal. These experiments were conducted in a flow tube reactor wtih gas temperatures between 1100 and 2000 exp 0 K and oxygen concentrations between 0 and 20%. In several experiments, ignition was visibly apparent in less than 10 msec and complete burnout was obtained before 100 msec. For a given gas temperature, devolatilization rates in the presence of oxygen were much greater than those observed in an inert atmosphere at Stanford and by others. Energy from the oxidizing volatiles is fed back to the coal particles, further increasing its temperature and volatile release rate, and volatile yield. A flame sheet model, analogous to the single droplet combustion model, predicts devolatilization rates that are in good agreement with experimentally measured rates. Particle size inhomogeniety plays an important role in determining the overall devolatilization profile even for relatively narrow size distributions. Solid samples of partially reacted coal were collected and subsequently analyzed for CO sub 2 surface area, true density, bulk density and C/H and ash fractions. Physical data obtained on samples taken in the char burnout phase were used as inputs to the pore-tree model for char combustion developed by Simon and Finson. The predicted reactivity was compared to the experimentally derived reactivity and generally showed good agreement. Bulk density determinations on samples at high burnoff (> 90%) showed a steep upturn, indicating particle breakup in the final stages of combustion. 53 references, 111 figures, 1 table. (ERA citation 08:050595)