Comparison of Secondary Air System Arrangements in a Recovery Boiler Using CFD Modeling Techniques, 2010 TAPPI/PAPTAC International Chemical Recovery Conference

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The quest for the next generation of air system designs on recovery boilers has resulted in some developments by different boiler designers in an effort to provide updated “state-of-the-art” air designs for improved black liquor combustion. Improvements in recovery boiler design using CFD modeling has been a proven technique in the development of air system designs and has helped to provide an understanding of the methods of improved black liquor combustion.

The work in this paper reviews various air system configurations in a recovery boiler for comparison of the merits of one design versus others. The development of air systems has involved increasing the number of levels of air within the different zones in the boiler in an effort to optimize black liquor combustion, increase control of the combustion process and provide flexibility due to changes in fuel conditions. Simulations were performed on a traditional two-level air design with enhanced air jet configurations utilizing additional air levels below the black liquor firing elevation. CFD modeling results are presented comparing single and dual level air streams, specifically at the secondary air level above the char bed where the interaction of the combustion air plays an important role in the overall combustion.