CFD Combustion Modelling - A Comparison of Secondary Air System Designs, 1992 Engineering Conference Proceedings

ABB Combustion Systems Canada has recently developed a three-dimensional computer modelling program that enables a comprehensive numerical simulation of the combustion process that takes place within a kraft recovery furnace. Simulation of the combustion process requires the use of a computational fluid dynamics (CFD) computational code, that models the processes of mass, momentum, and energy transport within a combustion chamber. Using this program two simulations of a recent contract were developed. The first is an exact model of the geometry of the "as-sold" Crestbrook Forest Industries recovery furnace, utilizing our latest air system design. The second simulation is identical except for the secondary air system, which is based on an older design. A description of both of these models is provided, along with a detailed presentation of the flow fields obtained. The results of these two simulations predict a dramatic improvement in combustion behaviour that has been obtained using the HMZ TM (Horizontal Mixing Zone) secondary air system. The benefits include: a 75% reduction in particulate carryover, increased lower furnace temperatures, a 160 degrees F decrease in the lower furnace outlet temperatures, more uniform gas flow and temperatures, and a reduction in CO at the furnace exit.