GASIFICATION OF BLACK LIQUOR CHAR WITH CO2 AT ELEVATED PRESSURES

The kinetics of gasification of black liquor chars with carbon dioxide were studied under pressurized conditions (1-30 bar) and 600-800-degrees-C. The rate of gasification was found to be slightly less than first order in CO2, and the rate of gasification was strongly inhibited by CO. As pressure was increased, CO inhibition more than offset the effect of CO2 on the gasification rate. The net impact was that the rate of gasification at constant CO/CO2 ratio decreases by a factor of 4.6-6 as total pressure increases from 1 bar to 30 bar. The rate of gasification with CO2 is temperature sensitive, increasing by more than a factor of 10 with a 100-degrees-C increase in temperature. The reactivity of different kraft chars is not the same. In experiments with chars from three liquors, the rate varied by a factor of two at identical gasification conditions.