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

The ignition temperature and burnout of a semi-anthracite and a high-volatile bituminous coal were studied under oxy-fuel combustion conditions in an entrained flow reactor (EFR). The results obtained under oxy-fuel atmospheres (21%O(2)-79%CO(2), 30%O(2)-70% O(2) and 35%O(2)-65%CO(2)) were compared with those attained in air. The replacement of CO(2) by 5, 10 and 20% of steam in the oxy-fuel combustion atmospheres was also evaluated in order to study the wet recirculation of flue gas. For the 21%O(2)-79% CO(2) atmosphere, the results indicated that the ignition temperature was higher and the coal burnout was lower than in air. However, when the O(2) concentration was increased to 30 and 35% in the oxy-fuel combustion atmosphere, the ignition temperature was lower and coal burnout was improved in comparison with air conditions. On the other hand, an increase in ignition temperature and a worsening of the coal burnout was observed when steam was added to the oxy-fuel combustion atmospheres though no relevant differences between the different steam concentrations were detected. (C) 2011 Elsevier Ltd. All rights reserved.