Effect of co-firing on emissions and deposition during fluidized bed oxy-combustion

The relevance of coal oxy-firing in fluidized bed reactors has increased during the last years as an alternative for the development of CO2 capture technologies. The addition of biomass in the fuel blend is well-known in conventional combustion, but few experiences are found under oxy-combustion conditions. This paper discusses the results obtained when oxy-firing anthracite and corn stover in a lab-scale fluidized bed, paying attention to pollutant emissions, deposition rates and composition of the ashes. While SO2 emissions are affected by the chlorine content supplied with the biomass, NOx are much more dependent on operating conditions in a similar way to conventional combustion. As concerns the ash composition, chlorine is detected in fly ashes while the bed solids are mostly composed by aluminosilicates. Oxy-firing increases the chlorine detected in fly ashes in comparison to the air-fired tests. Deposition rates are barely modified by the O2/CO2 atmosphere; severe deposition is only detected for the blend with the highest chlorine content. Mixed Ca-K sulfates are found in deposits, minimizing the risk of chlorine-induced corrosion.