Effect of oxy-fuel combustion with steam and biomass addition on coal burnout in an entrained flow reactor

The coal burnout of a semi-anthracite was studied under oxy-firing conditions in an entrained flow reactor. The results obtained under oxy-fuel conditions were compared with those attained in air. The replacement of CO2 by 10 and 20% of steam in the oxyfuel combustion atmospheres was also evaluated in order to study the wet recirculation of flue gas. The results showed a decrease on coal burnout when N2 was replaced by CO2 for the same oxygen concentration (21%). Although when the oxygen concentration in the CO2 mixture was increased to 30 and 35%, the burnout value was higher than in air conditions. A worsening on coal burnout was observed when steam was added though no relevant differences between the different steam concentrations were detected. Also, coal and biomass blends of a semi-anthracite with 10 and 20% of olive residue were used in both air and oxy-firing combustion experiments. A significant increase in the burnout value was observed after the addition of biomass, this trend becoming more noticeable as the biomass concentration was increased.