Coal gasification pilot plant support studies. Subtask 1-1. Effects of process variables on the initial gasification reactions of noncaking coals. Topical report, April 1978-April 1980

Abstract

The primary objective of this investigation was to develop the necessary fundamental kinetic information needed to predict the yields of devolatilization products during the initial stages of hydrogasification of noncaking coals. 56 devolatilization tests were conducted with three different subbituminous coals: Colorado subbituminous B (CSB), Wyodak (W-38), and Adaville (W-16). All three are low-sulfur, Western coals that were chosen for this study mainly because they are abundant in reserve and have a low O/C atomic ratio. The devolatilization tests were conducted over a temperature range of 800/sup 0/ to 1400/sup 0/F at 35 atmospheres in either helium or hydrogen. Both isothermal and nonisothermal experiments were conducted. The limiting yield parameters of these coals were obtained from the experimental results using a previously developed procedure. The previously developed kinetic model described the devolatilization behavior of the three coals satisfactorily with respect to CO, CO/sub 2/, CH/sub 4/, C/sub 2/H/sub 6/, and H/sub 2/O yields. The model was unable to predict the yield of heavy hydrocarbons. Correlations were developed for determining the limiting yields of the oxygenated species, CO, CO/sub 2/, and H/sub 2/O, from all coals using only the atomic O/C ratio of the raw coal. In general, the kinetic model works well for subbituminous and lignite coals. However, additional work with higher ranked coals will expand the applicability of the model. Also, much effort is needed to improve the prediction of heavy hydrocarbons and oils. Studies aimed at determining the origin of the devolatilization products from the raw coal will be a great help in understanding the mechanism of devolatilization and will doubtedly yield valuable kinetic information.