KINETICS OF LIGNITE CHAR GASIFICATION - RELATION TO CO2 ACCEPTOR PROCESS

The differential rates of formation of carbon oxides and methane in the gasification of a high sodium lignite char from North Dakota were examined at 1500° F. and total pressures from 11 to 20 atm. The inhibiting effects of the reaction products were determined, and the experimentally determined rates were satisfactorily correlated by semiempirical rate equations. The rate equations used were derived from “tentative” physical models as follows. The formation of carbon oxides proceeds by reaction of steam adsorbed on carbon with an adjacent vacant carbon site. The formation of methane proceeds by reaction of steam adsorbed on carbon with an adjacent carbon site containing adsorbed hydrogen. Integral rate data also were obtained in a continuously operated (1.5 to 5 pounds per hour) gasification unit for both lignite and subbituminous chars. The data at 1500° F. are in line with predictions made from the above correlation of the differential data. Comparative integral rate data were also obtained for a number of different lignite chars of varying sodium content. The effect of temperature on the integral gasification rate in the continuous unit was measured in the range of 1500° to 1600° F. The strong inhibition of both the rates of formation of carbon oxides and methane by carbon monoxide is noteworthy. © 1969, American Chemical Society. All rights reserved.