Experimental study on the optimisation of staged air supply in the retort pellet burner
Riga Technical University, Institute of Energy Systems and Environment, Kronvalda blvd. ¹, Riga, LV-¹0¹0, Latvia;
The use of biofuels for heating purposes is beneficial from a greenhouse gas emissionpoint of view. But combustion of solid biofuels typically is related with high emission rates of CO, NOx, PAHs, VOCs and particle matter. The most important factor that is affecting the formation of harmful emissions is the way thecombustion process is organised. The amount of air injected and approach for the air supplysystem, are the most important factors affecting combustion process. Air staging is one of themost effective technical solutions for achieving complete combustion and low emissions. Themain idea of air staging is to inject air into different zones of a combustion process. The maingoal of this study is to optimise pellet combustion process in a ⁵00 kW boiler with staged airsupply. The research is based on on-site experiments and application of scientific instrumentation. Fly-away unburned fuel particles were discovered during the on-site experiments. Reduction of theamount of fly-away particles was set as a target function for the optimisation. The amount ofemissions (CO, NOx and particle matter) and the amount of incombustibles in fly ashes wereidentified. Two different solutions with applied secondary air supply nozzles were analysed. The results of the study show that even small changes in the way the combustion air is injectedcan significantly affect the combustion process.