Ignition behavior of coal and biomass blends under oxy‐firing conditions with steam additions

The ignition behavior of coal and biomass blends was assessed in air and oxy‐firing conditions in an entrained flow reactor. Four coals of different rank, an anthracite, a semi‐anthracite, and two high‐volatile bituminous coals, were tested in air and O 2 /CO 2 (21–35% O 2 ) environments. For all the coals, deterioration in ignition properties was observed in the 21%O 2 /79%CO 2 atmosphere in comparison with air. However, the ignition properties were enhanced when the oxygen concentration in the O 2 /CO 2 mixture was increased. Coal and biomass blends of a semi‐anthracite and a high‐volatile bituminous coal with 10 and 20 wt% of olive residue were also used in the ignition experiments under air and oxy‐firing conditions. The ignition behavior of the coals improved as the additions of biomass increased both in air and oxy‐firing conditions. In particular, the effect of biomass blending was more noticeable in the ignition of the high rank coal. Since industrial oxy‐coal combustion with a wet recycle would result in higher concentrations of H 2 O(v), the effect of steam addition on ignition behavior was also studied. A worsening in ignition behavior was observed when steam was added to the oxy‐fuel combustion atmospheres, although an increase in the steam concentration from 10 to 20% did not produce any significant difference in the ignition characteristics of the fuels.