Optimization of the Air Distribution in a Biomass Grate-Fired Furnace

Abstract

This study utilized a combination of FLIC(1D3.2C) and FLUENT(2021R2) software to optimize the primary air distribution along the grate and the performance of a straw briquette combustion furnace of a 7 MW unit in China used to produce hot air for drying grain. Three air distribution modes, namely front-enhanced, uniform, and rear-enhanced modes, were analyzed to determine their effect on the flue gas components above the grate, the temperature field in the furnace, and the nitrogen oxide concentration at the furnace outlet. The results of the calculations showed that the NOx emissions for the front-enhanced, uniform, and rear-enhanced modes were 133.5 mg/Nm3, 104.4 mg/Nm3, and 76.6 mg/Nm3, respectively. It was found that the rear-enhanced mode can expand the biomass drying, devolatilization, and combustion zone, thus improving the furnace combustion performance and decreasing NOx emissions. These findings can provide useful guidance for optimizing biomass chain-grate-firing furnaces.