Black liquor gasification process

Abstract

A process for recovering the energy and chemical content of an aqueous black liquor utilizing a reactor containing a drying zone located above a gasification zone. The reactor contains a bed of porous solid carbonaceous material in the gasification zone. Heat losses are restricted, preferably from both zones, by the provision of a layer of insulating material about the reactor. An oxygen-containing gas is introduced into the gasification zone in an amount less than about 60% of that required for complete combustion of the black liquor such that there is produced partial combustion and gasification reactions sufficient to maintain the temperature at an upper surface of the bed in the range of from about 870.degree. to 1200.degree. C. and to form a hot combustible gas which rises from the gasification zone. A concentrated black liquor containing alkali metal, oxysulfur compounds is introduced into the drying zone and the water contained therein evaporated by contact with the hot gases rising from the gasification zone. In the drying zone there is produced a reduced temperature product gas and dry black liquor solids which fall onto the surface of the bed in the gasification zone. The dried black liquor solids are converted into the hot combustible gas which rises from the gasification zone and alkali metal salts which melt and permeate through the bed. The product gases are withdrawn from an upper portion of the drying zone, and a melt in which the sulfur content is about 80% in the form of alkali metal sulfide is withdrawn from a lower portion of the gasification zone.