The central importance of devolatilization (pyrolysis) in any coal utilization process has been established. Volatile matter evolution is governed by a complex scheme of coupled kinetic and transport phenomena which are not fully understood. A more fundamental description of these chemical and physical mechanisms, particularly with respect to secondary reactions internal to the pyrolyzing coal particle, would provide a valuable tool for process design. Existing experimental data strongly support a consecutive reaction network with intraparticle secondary reactions in competition with mass transport. Several models exist to describe this network for the case of non-softening coals. Models have also been developed to treat extraparticle secondary reactions and the details of bubble dynamics during softening coal pyrolysis. The present goal is to generate a simplified mass transfer description and apply it in a transient model of devolatilization of softening coals that would be suitable for practical engineering applications. This would then be combined with descriptions of other transport phenomena in a global model of coal pyrolysis. The screen heater reactor has provided important experimental data regarding the global kinetics and product distributions from rapid devolatilization. This apparatus has been adapted to study the influence of several process conditions: temperature history (particularly initial heating rate), particle size, and pressure. The specific objectives of the proposed study are summarized below. 29 refs., 5 figs.