Air staging strategies in biomass combustion-gaseous and particulate emission reduction potentials

Gaseous and particulate emissions have been investigated with different air staging strategies over a wide range of secondary air flow rates. Laboratory scale wood pellet combustor, supplied by an underfeed fuel bed input, is used. The air staging strategies have been employed to study burning rate, temperature in primary and post combustion zones, and NO, CO and PM emissions, taking into account the air to fuel stoichiometric ratio. 50% CO reduction and 9 times less particle mass concentration than non-staged combustion are achieved by deploying a uniform secondary air module in a higher position from the bed. The minimum NO (37% reduction than non-staged) measured in the non-uniform air distribution module at the higher flow rate with lower distance from the fuel bed. The results demonstrate a trade-off between NO and CO, PM emissions but also significant potential for reducing particulate and gaseous emissions by deploying air staging in the pellet combustor