Co-firing coal with biomass in oxygen- and carbon dioxide-enriched atmospheres for CCS applications

• Biomass cofiring investigated at TGA and 20 kW scale.
• Oxygen- and carbon dioxide-enriched atmospheres tested.
• TGA results not directly scaleable to larger experiments
• Cofiring can reduce NO and SO2 in oxyfuel conditions.
• Cofiring in enriched conditions increased carbon burnout.

Biomass combustion and carbon capture and storage (CCS) individually represent significant options for decarbonising the power generation sector and when combined may permit a carbon–neutral or even carbon-negative process. Despite this potential, little research has been published that examines the combustion of biomass in atmospheres with application in CCS processes. This work reports on bench- and laboratory-scale testing of biomass and coal combustion in atmospheres enriched in O2 and CO2 which are relevant for retrofitting power stations for oxyfuel combustion. At bench-scale, thermogravimetric analysis shows substituting N2 as the combustion diluent with CO2 has little impact on the combustion properties of the fuels but that increasing the O2 concentration accelerates combustion of coal and biomass chars. Results from cofiring three biomasses with coal at 20 kW scale suggest substitution of N2 with CO2 significantly reduces temperatures, carbon burnout and emissions of NO while combustion in O2-enriched conditions has the opposite effects. Emissions of NO and SO2 were found to reduce compared to air in combustion atmospheres enriched with O2 and CO2 while combustion temperatures and carbon burnout slightly increased.