Hydrocarbon Research, Inc.

Clarence A Johnson

William Volk

John Shen

The gasification of coal to produce a methane-rich product gas is accomplished through the controlled slow heating of particulate coal in a gasifier comprising two or more zones, whereby any significant decrease in the density of the coal particles is minimized and particle swelling and friability are significantly reduced, while the carryover of fines and deposition of tars in the product gas conduit are thereby minimized. The particulate coal heating rate in the gasifier zones is usually between about 10.degree. and 200.degree. F per minute. When the particulate coal is to be fed to the gasifier at elevated temperature, further improvements are achieved with swelling type caking coals through their pretreatment by preheating the coal at a slow rate between 10.degree. and 100.degree. F per minute up to about 800.degree. F in multiple fluidized beds. Any carryover of fines in the product gas stream from the uppermost zone of the gasifier is further reduced by utilizing either a solids separation step or a scrubbing step in the gas stream. The coal particles and/or tars thus recovered are returned to a high temperature zone of the gasifier.

Process for the multiple zone gasification of coal

Low rank coals such as subbituminous or lignites containing more than about 10 wt. % moisture are first dried and then passed to a fluidized bed where the coal is passivated against reabsorption of moisture by coating the warm coal particles with a heavy liquid hydrocarbon material. Such coating substantially prevents the reabsorption of moisture in the coal, and thereby prevents autogenous heating and possible spontaneous ignition during subsequent transportation or storage of the passivated coal.

Coal drying and passivation process

Low rank coals such as subbituminous or lignites containing more than about 10 weight percent moisture are dried and passivated against reabsorption of moisture in a fluidized bed by heating the particulate coal with a warm inert gas passing upwardly through the bed and simultaneously coating the warm particulate coal with a heavy liquid hydrocarbon material. Such coating aids in the removal of the moisture and prevents the reabsorption of moisture by the coal and thereby prevents consequential heating and possibly spontaneous ignition of the coal during its subsequent transportation or storage.

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Princeton, NJ, United States of America

Clarence A Johnson