Validation of Combustion and Fume Formation Models for an Operating Kraft Recovery Boiler, 1996 Engineering Conference Proceedings

Richard A. Wessel & Christopher L. Verrill

Babcock & Wilcox Company

Models for black liquor combustion and fume formation were previously developed and implemented into a kraft recovery furnace model. Reaction mechanisms for black liquor combustion and alkali release are limited by heating rate, mass transfer, internal pore diffusion, and chemical kinetics. These mechanisms simulate combustion of the black liquor spray as well as deposits on the furnace walls and char bed. The furnace model was used to predict the performance of an operating kraft recovery boiler before and after changes were made to firing strategy and air distribution. In this paper, modeling results for flow, combustion and fume formation are presented and compared to performance test data. Trends in performance resulting from changes in operation are correctly predicted by the model. The pre-dicted quantity and composition of dust leaving the furnace are also in reasonable agreement with operating data. The sources of inorganic aerosol are identified, and relative importance of various reaction mechanisms for alkali release are evaluated. Further improvements to the model are planned and addit-ional model validation is needed. However, these results demonstrate that the model is useful for qualitatively understanding and evaluating how changes in operation affect boiler performance and cleanliness.