VOLATILES AND CHAR CARBON YIELDS DURING BLACK LIQUOR PYROLYSIS

The volatiles and char carbon yields for spent pulping liquors were measured by pyrolyzing single liquor droplets in N2/CO atmospheres at 600-1200-degrees-C, weighing the droplet residue, and analyzing the residue for carbon content. For a kraft black liquor, the volatiles yield in these experiments increased from 33% to 75% over the temperature range investigated. The carbon content of the char residue decreased from 65% to 12% of the carbon initially in the droplets over the same temperature range. Droplet mass had no effect on volatiles or char carbon yield over the range studied In experiments with six kraft liquors at 800-degrees-C, the volatiles yield ranges from 35-47% of the dry liquor solids while the carbon the char ranged from 26-48% of the carbon originally in the black liquor solids. Both yields were higher for NSSC liquors. Additional measurements with a larger number of liquors need to be made to better define the range of variation among liquors.