RADIATION HEAT-TRANSFER IN A LABORATORY-SCALE, PULVERIZED COAL-FIRED REACTOR

This article reports local gas and particle temperature and radiant and total heat flux measurements made in a 0.8-m-diameter cylindrical down-fired laboratory-scale reactor fired at approximately 0.1 MW(t) with a high-volatile bituminous coal pulverized to a mass mean diameter of 55 mum. Spatially resolved gas temperatures were measured using a triply shielded suction pyrometer and particle cloud temperatures with a specially designed two-color pyrometer. Hemispherical wall radiant heat fluxes were measured using an ellipsoidal radiometer and total (convective plus radiative) heat fluxes with a plug-type heat flux meter. The particle and gas temperature profiles exhibit a strong spatial dependence due to reactor fluid dynamics. Additionally, the difference between the gas and particle temperatures varies significantly with location relative to the burner inlet streams and recirculation zones. Maximum radiant fluxes of 110 kW/m2 were observed, with differences between radiative and total heat flux being less than 10% at all axial locations. Maximum heat fluxes occur downstream from the location of the maximum gas and particle temperatures and exhibit a generally decreasing trend as distance from the flame increases. Predictions of the radiation heat transfer in the reactor were carried out using the discrete ordinates method. Both spectral and gray radiative transfer calculations were performed. Predicted radiant fluxes agree well with the experimental data. The sensitivity of the model predictions to the uncertainties in the input data is explored.