Performance and validation of a radiation model coupled with a transient bubbling fluidized bed combustion model

None of the transient bubbling fluidized bed combustor (BFBC) models couples the solution of radiative transfer equation with the solution of conservation equations of other transport processes although thermal radiation is of considerable importance in such systems, as such an objective requires both accurate and computationally efficient methods for not only the solution of radiative transfer but also the estimation of radiative properties of particle-laden combustion gases. Therefore, in this study, a 1-D transient comprehensive system model for combustion of lignite is coupled with a 3-D radiation model based on method of line solution of discrete ordinates method utilizing one gas spectral line-based weighted sum of gray gases for spectral gas properties, Mie theory for gray particle properties, and gray wall properties. Predictive accuracy of the model is validated against (i) predictions of a computationally inefficient spectral radiation model and (ii) measurements of transient temperature and concentrations of the species O2 and CO obtained from METU 0.3 MWt atmospheric bubbling fluidized bed combustion test rig firing lignite. The outcome of this study provides a comprehensive, accurate, and computationally efficient tool for simulation of transient BFBCs and highlights the significant impact of radiative heat transfer in modeling of industrial boilers. •Transient BFBC model and radiation model are coupled for lignite combustion in BFBC.•SLW-1 model provides sufficiently accurate radiative heat transfer predictions.•Using radiation model improves temperature predictions of BFBCs bounded by cold wall.•Coupling of radiation and BFBC models remarkably affect CO concentration predictions.•Radiation significantly contributes to heat transfer in BFBCs bounded by cold wall.