Coal combustion: Effect of process conditions on char reactivity. Quarterly technical report, October 1, 1994--December 31, 1994

Abstract

The project will quantify the effect of the following pyrolysis conditions on the macropore structure and on the subsequent reactivity of chars: (a) pyrolysis heating rate; (b) final heat treatment temperature (HTT); (c) duration of heat treatment at HTT (or soak time); (d) pyrolysis atmosphere (N{sub 2} or O{sub 2}/N{sub 2} mixtures); (e) coal particle size (100--1000 {mu}m in diameter); (f) sulfur-capturing additives (limestone); and (g) coal rank. Pyrolysis experiments will be carried out for three coals from the Argonne collection: (1) a high-volatile bituminous coal with high ash content (Illinois No. 6), (2) a bituminous coal with low ash content (Utah Blind Canyon) and (3) a lower rank subbituminous coal (Wyodak-Anderson seam). A systematic parametric study was carried out in the past quarter to quantify the effect of different process parameters on the ignition phenomena. Using the mathematical model presented in the previous quarterly report, we investigated how char properties (porosity, particle size, macropore surface area, and micropore radius) and operating conditions (oxygen concentration, flow rate) affect ignition phenomena. In every case, we clearly identified the temperature range in which thermal ignitions may be expected. Model predictions will next be compared to experimental results to validate our theoretical model.