Lignin extraction from black liquor will result in some operational changes in pulp mills. There is a lack of publically available experience in firing black liquor in a recovery boiler. This work will support full scale implementation of the technology. For combustion, important questions remain about the spraying of the black liquor into the recovery boiler and the heat and carbon distribution in the lower furnace. These variables are important to sulfate reduction, char burnout, sulfur release and the nitrogen chemistry.

In this work CFD modeling will be used to provide an understanding of how key variables such as black liquor spraying temperature and air distribution will affect the black liquor char distribution, carryover and how air distribution might need to be changed. We will use and existing CFD model for an existing Finnish recovery boiler. We will make calculations for one black liquor at two levels of lignin reduction. The levels of lignin reduction suggested are 10% and 20%, but will be agreed upon with SKY.