Investigation of Non-thermal Plasma Assisted Combustion of Solid Biomass Fuels: Effects on Flue Gas Composition and Efficiency

Abstract

Interest in biomass is increasing due to the environmental benefits compared to fossil fuels. This study investigates a non-thermal plasma (NTP) device that has the potential to reduce dry flue gas loss (DFGL) from biomass combustion. DFGL is an efficiency loss in combustion processes, caused by unutilized heated excess air in the flue gas. Reducing DFGL is complicated by a narrow range of optimum operating conditions for combustion of biomass. In this study, a NTP reactor is integrated with a 150 kWth furnace to investigate the effects of the NTP-generated ozone (produced via high voltages at resonant frequency) on the combustion of biomass and coal. The ozonolysis of the volatile organic compounds (VOC) is also simulated with thermodynamic equilibrium models using FactSage 7.2. The DFGL is determined from the corresponding flue gas compositions. For biomass combustion, increasing NTP intensity from 50 to 224 W decreases the DFGL by 0.2–1.0%. For coal combustion, DFGL increases by 4.6–6.3% with increasing NTP intensity. Simulation results show that with an increase in ozone (10–20 g), the ozonolysis of alkanes and aromatics (0.2 kg respectively) results in a constant or increase in CO2 content by 0.0003%, a reduction in the residual O2 content by 0.002%, consequently decreasing DFGL. Ozonolysis of alkenes increases DFGL as the CO2 content decreases by 0.002% as the amount of ozone increases. The experimental and simulation results indicate that the VOC emitted from the coal in this study is likely to be composed of more alkenes than alkanes.