CFD Modeling of Bubbling Fluidized Bed Combustor Michael M. Choi, Troy Robinson, Larry Baxter

1. CFD Modeling of Bubbling Fluidized Bed Combustor Michael M. Choi, Troy Robinson, Larry Baxter Chemical Engineering Department, BYU, Provo, UT February 2003 Accomplishments During the past few months, we developed a 1D model of a fluidized bed (version 0.1). The model predicts fluidized bed height, reactant concentration leaving the bed, and bubble rise velocity based on the bubble diameter, minimum fluidization velocity (in the emulsion phase), air flow-rate from the bottom, and the original bed height. Objective Our objective is to develop a CFD model of bubbling fluidized bed combustor. We are using object-oriented programming with OpenGL and Visual C++. What is a Fluidized Bed Combustor? A fluidized bed is similar to a conventional boiler except that fluidized bed suspend solid-fuels, sands, and catalysts (dolomite, limestone) on upward blowing jets of air. The fuels trapped in the bed are burned. Significant reductions of SO2, NOx, and combustion of lower quality fuels can be achieved with fluidized bed boilers. Stage of Fluidization Pictures – Different views of the model version 0.1 with different input data. The calculated results are shown on the right. Future works The current model is being modified to predict: • pressure drop • concentration gradient • min. fluidization velocity • temperature gradient Better graphical interface and user interactive features are being added currently. An unfinished model of fluidized bed is shown on the right. A significant improvement has been made in object-oriented programming. The model has a zooming/rotating capability that can be easily controlled with a mouse, plus changing variables are made easier with a dialog box. Theoretical pressure drop within the bed has been calculated and will be compared with the experimental data with the fluidized bed at BYU. HYBEX™ - Bubbling fluidized bed boiler Kymin Voima, Kuusankoski, Finland Fuels: Bark, forest residue, sludge, peat, gas, oil Steam: 269 MWth, 107 kg/s 114 bar, 541 °C Start-up: 2002 CYMIC™ - Circulating fluidized bed boiler Alholmens Kraft, Pietarsaari, Finland Fuels: Wood, peat, coal Steam: 550 MWth,194/179 kg/s, 165/40 bar, 545/545 °C Start-up: 2001 Acknowledgement: Special thanks to Keijo Salmenoja, AKER KVAERNER, who provided the pictures above