3-DIMENSIONAL KRAFT RECOVERY FURNACE MODEL - IMPLEMENTATION AND RESULTS OF IMPROVED BLACK-LIQUOR COMBUSTION MODELS

A three-dimensional mathematical model of a kraft recovery furnace was improved by developing better models of black-liquor combustion. Thes e new models-which describe combustion of black-liquor drops and black -liquor deposits on the furnace walls and char bed-include mechanisms for sodium sulfate reduction and carbon removal by CO2 and H2O gasific ation. Black-liquor combustion is fully coupled to the solution for ga s-phase combustion and turbulent flow in the furnace. Predicted black- liquor combustion patterns are presented for a commercial-scale recove ry furnace, including chemical species distributions, temperature maps , and component reaction rates for char burning and smelt reduction. C arbon removal rates for gasification, oxidation, and sulfate reduction are compared and evaluated for entrained particles, furnace walls, an d the char bed. Predicted smelt-reduction efficiencies are compared wi th commercial performance.