Improvements in or relating to the process of making gas from carbonaceous solid fuels

摘要

673,170. Gasifying carbonaceous materials; gas mixtures. ROLLINSON, E. W. (Pittsburgh Consolidation Coal Co.). Jan. 5, 1950, No. 305/50. Classes 55 (i) and 55 (ii). Steam is passed into a mixture of carbonaceous fuel and calcium oxide (100 parts carbon to 120-300 lime) at 1430-1800‹ F. and a pressure such that the overall reaction, i.e. both between steam-carbon and carbon dioxidelime, is thermally self-sufficient. The methane: hydrogen ratio in the product gases increases with increase of pressure which may range from 5-40 atmospheres and is at least equal to 3.40 - 1.89 X 10-2(t‹F - 1430) + 4.48 X 10-4 (t0F- 1430)2 atmospheres. In a preferred embodiment a mixture of " char," a low temperature distillation residue of hydrocarbonaceous fuel, and lime in a vessel is initially heated by combustion of a small amount of the fuel, steam then replacing air introduced for this purpose and the bed temperature being maintained by the heat of the carbon dioxidelime reaction, until most of the fuel is consumed, a valve in the gas outlet being regulated to provide the pressure required for the composition of gas desired. To regenerate the lime air is again admitted in order to burn the remaining fuel, and the lime is separated from ash as by elutriation. In another embodiment in which regeneration is effected in a fluidized bed, a series of superposed beds 79 are supplied with steam through conduits 82, product gas escaping through a line 94. One or more zones may be cut out of operation and the contents discharged for regeneration by fluidizing the material by increasing the steam velocity and withdrawing it through conduits 88 into a steam or flue gas conduit 102. Regeneration is effected in a fluidizing vessel 116 to which it is admitted from a storage vessel 107 by an air stream through a line 114. Modified apparatus provides for fluidization of the gas making bed and for an additional vessel in which a fluidized bed of lime and carbon monoxide conversion catalyst is utilized to increase the hydrogen content and remove both carbon monoxide and dioxide, the final gas consisting e.g. of H 2 84.7 p.c., CH 4 13.4 p.c., CO 1.2 p.c., CO 2 0.7 p.c. In a further modification, in which an increased yield of methane is obtained by causing the product gases to pass through a second bed of solids at a slightly lower temperature, the reaction vessel has three superposed fluidized beds with a descending flow of material and a temperature decreasing upwardly from 1670-1770‹ F. in the bottom bed to 1430-1600‹ F. in the top. The gas may comprise 52.1 p.c. H 2 , 44.1 p.c. CH 4 , 0.6 p.c. CO 2 . Coal, lignite, oil shale, tar sands, coke and petroleum pitch coke may be employed and gases produced with a H 2 : CO ratio suitable for hydrocarbon synthesis.