Prediction of heat transfer in the kraft recovery boiler superheater region

Accurate prediction of tube surface temperature is important for determining whether accelerated superheater corrosion will occur in kraft recovery boilers. A heat transfer model, which combines an iterative numerical solution scheme with a more realistic flue-gas flow field obtained from a CFD code FLUENT, has been developed to predict the tube, steam, and flue-gas temperatures in the superheater region. Results of tests performed for a recovery boiler show that temperatures predicted by the model are in good agreement with actual temperatures measured using thermocouples. The presence of a large flue-gas recirculation zone above the bullnose is shown to have an adverse effect on the heat transfer in the superheater region.This work is part of the research on “Recovery Boiler Fireside Deposits,” supported by ABB Combustion Systems, Ahlstrom Corp., Aracruz Cellulose SA, Babcock & Wilcox Co., Champion International Corp., Diamond Power Specialty Co., E. B. Eddy Forest Products Ltd., Gotaverken Energy Systems, Jansen Combustion and Boiler Technologies Inc., James River Corp., Tampella Power Corp., Union Camp Corp., Westvaco Corp., Weyerhaeuser Co., Willamette Industries, and the Ontario Ministry of Colleges and Universities through its URIF program