Combustion and heat transfer characteristics in a square internally circulating fluidized bed combustor with draft tube

The effects of bed temperature (800-950 degrees C) and gas velocity to the draft tube (0.26-0.37 m/s) on the heat transfer coefficient and the overall combustion efficiency have been determined in a square internally circulating fluidized bed combustor (0.28 m width x 2.6 m height) with an orifice-type square draft tube (0.1 m width x 0.9 m height). The overall combustion efficiency increases with increasing the excess air and the bed temperature. At a given aeration rate to the moving bed, the heat transfer coefficient goes through a maximum value with increasing gas velocity in the fluidized bed. The heat transfer coefficients in the moving bed and in the freeboard increase with increasing gas velocity to the fluidized bed and bed temperature. (C) 2008 Elsevier Ltd. All rights reserved.