Experimental investigation of the carbon dioxide effect on the devolatilization and combustion of a coal and sugarcane bagasse

This study investigates the CO2 influence on thermal decomposition of sugarcane bagasse and a low-rank coal. Experiments at low and high heating rates were performed under different ratios of CO2/O-2/N-2 atmospheres to evaluate devolatilization, char combustion, burnout, SO2, NO and CO emissions. When N-2 was replaced by CO2, the coal combustion was enhanced and the kinetic study presented lower initial activation energy, the devolatilization yield was higher and the CO2-char presented higher reactivity compared to N-2-char. The results obtained for sugarcane bagasse presented opposite behavior, and lower conversions and char reactivity were observed. The kinetic study showed a negative influence on sugarcane bagasse devolatilization and the activation energy was significantly higher under CO2 than under N-2 (189 kJ mol(-1) and 86 kJ mol(-1), respectively). The difference between the fuels can be attributed to the higher volatiles content of the sugarcane bagasse, in which the suppression caused by CO2 partial pressure under 80% CO2 atmosphere was more pronounced for biomass than for coal, confirmed during devolatilization in the DTA results. Regarding the pollutant emissions, the NO formation decreased and the CO formation increased when N-2 was replaced by CO2. No conclusive trend was observed for the SO2 species. (C) 2020 Elsevier Ltd. All rights reserved. (AU)