Reduced Pollutant Emissions and Slagging Rate of Biomass Pellet Combustion by Optimizing the Multilayer Distribution of Secondary Air

Abstract

The utilization of coal and other fossil fuels is becoming increasingly restricted. Biomass, as a clean and renewable energy, plays a significant role in achieving zero carbon emissions. However, biomass is prone to slagging in the combustion process due to its high alkali metal content. The ash slagging rate and pollutant emission level of flue gas can be reduced by optimizing the air distribution, in order to decrease the fuel layer temperature in the combustion chamber. The results reveal opposite change trends of CO and NOx concentrations in the flue gas. The NOx emissions of corn stalk combustion under the multilayer secondary air distribution are obvious compared with those of rice husk combustion. The slagging rate of corn stalks is highly correlated with temperature T1 of the fuel bed. The silica ratio (G), alkali/acid ratio (B/A), Na content index (Na (index)), and alkaline index (Alc) cannot accurately predict the slagging tendency when temperature T1 changes. Therefore, the modified predictive index (Gt) was proposed to predict the slagging tendency of corn stalks with the combustion zone temperature T1 effectively. The experimental results can contribute to the efficient combustion and low pollutant emissions of biomass.