Effect of various drying methods and levels on the conversion of low-rank coals. [Low severity]
The liquefaction conversion of three low-rank coals (LRC) were determined using three drying methods and varying process severity. The low-rank coals used in this study were Wyodak (Wyoming) subbituminous, Indian Head (North Dakota) lignite, and Morwell (Australian) brown coal. The coals were dried using air, hot solvent, and hot water methods so that the feed coal was either completely dry (100% dried) or had a moisture content half that of the as-received coal (50% dried). Under mild-severity liquefaction conditions, both the Wyodak subbituminous and Indian Head lignite coals showed decreased overall conversion with drying, irrespective of drying method. The brown coal showed an increase in reactivity for all cases except at 100% dryness. The largest decreases in reactivity were observed when air or oil drying was extreme (100% dryness) or when hot-water drying was used. When Wyodak and the Indian Head coals were completely dried in air and oil, and then moisture was added to a level equivalent to that of the as-received coal, the reactivity was restored to that of the original coal. This supports data obtained at UNDERC during hydrothermal treatment for LRC-water slurry preparation, which showed that temperatures in excess of about 270/sup 0/C, pyrolysis conditions, were necessary to yield a product that did not reabsorb moisture to its equilibrium level. Under severe liquefaction conditions, drying increased overall conversion, but the yield of liquid product remained nearly constant. The product slurry contained higher ratios of distillate to soluble residuum as the water content increased although the total liquid product yield remained constant. 6 refs.
- Research Organization:
- North Dakota Univ., Grand Forks (USA). Energy Research Center
- DOE Contract Number:
- FC21-83FE60181
- OSTI ID:
- 6481373
- Report Number(s):
- DOE/FE/60181-146; CONF-8511136-1; ON: DE86003769
- Country of Publication:
- United States
- Language:
- English
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