Numerical study of preheating primary air on pinewood and corn straw co-combustion in a fixed bed using Eulerian-Eulerian approach

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The effect of preheating primary air on the co-combustion characteristics of a 50–50% blend of pinewood and corn straw in a fixed bed. The primary air temperatures were assessed from 20 to 130 °C. The co-combustion characteristics were included the co-combustion behaviors and emissions. In order to reveal the features of the combustion process in the porous bed, a two-dimensional unsteady state model was employed to investigate the combustion process in a fixed bed of blended biomass on the combustion process in a fixed bed reactor. Conservation equations of the bed were implemented to describe the combustion process. The gas phase turbulence was modeled using the k-ε turbulent model and the particle phase was modeled using the kinetic theory of granular flow. Results showed that by increasing primary air temperature the residual mass on bed decreased, while the average burning rates and ignition front propagation velocity increased At the primary air temperature of 85 °C the smallest unburned carbon was left in the ash, and the emissions of nitrogen-compounds were relatively small. In contrast, the primary air temperature of 85 °C was found to be well-operating condition, which can be suggested for industrial boiler during blend co-combustion. The simulation results were then compared with experimental data for different temperature, which shows that the combustion process in the fixed bed is reasonably simulated. The simulation results of solid temperature, gas species and process rate in the bed are accordant with experimental data.