Carbon and char residue yields from rapid pyrolysis of kraft black liquor

The yields of char residue, fixed carbon and inorganic carbonate were measured for oxidized black liquor char residues produced in a laboratory laminar entrained-flow reactor (LEFR) at heating rates of 4000-13 000 degreesC/s. The char residue yields at the end of devolatilization thus obtained decreased nearly linearly with temperature, from 75% at 700 degreesC to 58% at 1100 degreesC. There were explainable differences in the char residue yields from the liquor used in this study and those used in other studies. Char residue yields seemed to depend mainly on the temperature to which the particles or droplets were exposed and were not very sensitive to heating rate. Fixed carbon yields behaved similarly to those of the char residue. The fixed carbon remaining at the end of devolatilization decreased from 67% at 700 degreesC to about 45% at 1100 degreesC. The carbonate content in black liquor changed very little before and after devolatilization. (C) 2001 Elsevier Science Ltd. All rights reserved.