Feasibility study of forest residue use as fuel through co-firing with pellet

Co-firing is a useful technology for reclaiming waste biomass as fuel. This article studies the use of three different forest residues (Eucalyptus, pine and pine bark) with pellet based on a mixture of fuels prior to combustion. Several combustion configurations, such as the basic configuration (only preheated primary air supply) and other especially developed configurations, such as secondary air and gas recirculation, are studied and optimized. Due to feeding problems, a co-firing feeding hopper was specially developed and honed in order to assure a precise feeding rate of different fuel materials. The experimental results suggest that the pine bark has the best feed performance. Overall, a lower efficiency was achieved compared with pellet-only combustion. Co-firing of these blends is financially viable due to the lower price of the treated pine bark. High percentages of pine bark (50%) reduce efficiency significantly. This is improved with secondary air and recirculation. Pine bark of around 25% is the most suitable configuration.