Radiative heat transfer in a circulating fluidized bed coal combustor

In order to investigate the contribution of radiative heat transfer to total heat transfer in a circulating fluidized bed coal combustor, heat transfer experiments were carried out. The test facility has the dimension of 6.0 m in height and 0.2 m X 0.2 m rectangular cross-section. Anthracite coal was used for the fuel, and the heat transfer tubes were installed near the wall at three different axial locations. The radiation probe for the direct measurement of radiative heat flux from the bed was installed at the middle of the combustor. The bed temperature was in the range of 650-850 degrees C, superficial gas velocity was 3.0-5.0 m/s and measured suspension density was 20-30 kg/m(3). The heat transfer coefficients obtained in this operating range were about 200-300 W/m(2) K. The suspension emissivity determined from the radiation probe was in the range of 0.7-0.98 and the contribution of radiative component to total heat flux was found to be 15-36% at the operating temperature ranges. (C) 1999 Elsevier Science S.A. All rights reserved.