GB659213A - Improvements in or relating to method of distilling and fluidizing solids - Google Patents

Abstract

659,213. Distilling carbonaceous materials. PITTSBURGH CONSOLIDATION COAL CO. April 27, 1949, No. 11183. Convention date, May 15, 1948. '[Class 55(i)] Finely divided coal, oil shale &c. is circulated downwardly through a distillation zone in intimate contact with gas descending at a lower velocity and maintaining the coal in a dense fluid state ; solids and vaporous products are withdrawn at the bottom of the zone. For the low temperature distillation of high volatile bituminous coal, finely. divided coal from a hopper 14 is charged into a vertical retort 12 together with a high velocity stream of hot recycled residue delivered by a feeder 22 from a separator 44 the resulting temperature of the mixture ranging from 800‹ to 1400‹F. The relative amounts of coal and residue are adjusted so as to reduce the density of the solids in the retort to less than 75 per cent of that of the packed solids unmixed with gas and a valve 26 at the foot of the retort discharging into a separator 28 is regulated to produce a flow such that evolved gases are carried down with the solids but at a lower speed so that their upward superficial velocity in relation to the solids effects their fluidization. This velocity may range from 0.1 to 6 feet per second or move according to the size of the particles. Part of the residue is withdrawn through a conduit 32 and the remainder is passed with air through a combustion tube 40 in which a portion is burnt to provide heat for the distillation. Flue gas may be stripped from the recycled residue by inert gas introduced into separator 44. Gas may be introduced into the retort through a pipe 49 to supplement the fluidizing effect of the volatiles or build up pressure in the system which may reach 200-500 lbs. per square inch. In a modification the recycled residue is fiuidized with air, recycled gas, steam, or nitrogen, in a vessel above the retort and fresh coal is introduced at an intermediate point. Another apparatus provides two retorts in series with a narrower conduit connecting the bottom of one with the top of the other. Fresh coal may be introduced at a succession of inlets to minimize agglomerating tendencies, and air &c. may similarly be injected to maintain the temperature. To promote mixing of the solid streams they may be caused to swirl by return bends &c. in the conduits, or a mechanical agitator may be located at a right-angle bend.