Oxy-fuel combustion of coal and biomass blends

The ignition temperature, burnout and NO emissions of blends of a semi-anthracite and a high-volatile bituminous coal with 10 and 20 wt.% of olive waste were studied under oxy-fuel combustion conditions in an entrained flow reactor (EFR). The results obtained under several oxy-fuel atmospheres (21%O-2-79% CO2, 30%O-2-70%CO2 and 35%O-2-65%CO2) were compared with those attained in air. The results indicated that replacing N-2 by CO2 in the combustion atmosphere with 21% of O-2 caused an increase in the temperature of ignition and a decrease in the burnout value. When the O-2 concentration was increased to 30 and 35%, the temperature of ignition was lower and the burnout value was higher than in air conditions. A significant reduction in ignition temperature and a slight increase in the burnout value was observed after the addition of biomass, this trend becoming more noticeable as the biomass concentration was increased. The emissions of NO during oxy-fuel combustion were lower than under air-firing. However, they remained similar under all the oxy-fuel atmospheres with increasing O-2 concentrations. Emissions of NO were significantly reduced by the addition of biomass to the bituminous coal, although this effect was less noticeable in the case of the semi-anthracite. (C) 2012 Elsevier Ltd. All rights reserved.