Combustion of Poplar and Pine Pellet Blends in a 50 kW Domestic Boiler: Emissions and Combustion Efficiency

Poplar pellets with and without Ca, Mg-lignosulphonate and three poplar and pine pellet blends (with three different percentages of pine5, 45 and 95 wt.%) were burned in a 50 kW domestic boiler in order to evaluate their suitability as fuels. The boiler efficiency and emissions were analyzed and compared with those from tests with poplar pellet. It was found that the adequate adjustment of excess air and of flowrate of secondary air according to the fuel properties improve the combustion efficiency. The results show an improvement in CO and NOx emissions and combustion efficiency when either Ca, Mg-lignosulphonate or pine were blended with poplar. However, the use of Ca, Mg-lignosulphonate is discouraged due to the observed increase in SOx emissions. No operational problems related with unburned matter or ash were observed for any of the pellet blends tested.