Computational and Experimental Studies on Combustion and Co-Combustion of Wood Pellets with Waste Glycerol

The shortage of fossil fuels and their rising prices, as well as the global demand for renewable energy and the reduction in greenhouse gas (GHG) emissions, result in an increased interest in the production of alternative biofuels, such as biodiesel or biomass pellets. In this study, the possibility of utilizing waste glycerol, as an addition to pine pellets intended for heating purposes, has been investigated. The usefulness of pellets containing glycerol additions has been compared in terms of applicable quality standards for wood pellets. The highest values of moisture (4.58%), ash (0.5%) and bulk density (650 kg/m³) were observed for pellets without glycerin waste. The addition of waste glycerol slightly increases the calorific value of the pellet (17.94 MJ/kg for 7.5% additive). A 10-kW domestic biomass boiler has been employed to burn the tested pellets. The consumption of analyzed fuels during boiler operation was determined. The concentration of CO, CO₂ and NO_x in exhaust gases has also been examined. It was observed that the addition of 7.5% of waste glycerol contributes to the reduction in NO_x concentrations by 30 ppm and CO₂ by 0.15%. The obtained experimental results were compared with the numerical calculations made with the use of ANSYS Chemkin-Pro. The conducted research indicates the legitimacy of utilizing waste glycerol as an additive to wood pellets. In addition, this type of addition has a positive effect on, among others, the increase in calorific value, as well as lower emissions of combustion products such as NO_x and CO₂.