Experimental investigations of pulverized coal char reactions with oxygen, carbon dioxide and steam

Predictive modeling of the performance of a coal-fired boiler under oxy-fuel conditions is de-pendent on fundamental data of how coal chars burn in these environments. An oxy-fuel boiler will contain much higher concentrations of carbon dioxide and steam than a traditional air-fired boiler. Higher concentrations of oxygen are also required to match the combustion tempera-ture and heat transfer rates of a traditional boiler. In this work, chars are generated from two bituminous and one sub-bituminous coals and combusted in different environments in Sanda's optical entrained ow reactor. Oxygen concentrations range from 24-60 vol-%, steam concen-trations range from 10-16 vol-%, and both nitrogen and carbon dioxide are used as a diluent. The coal chars burn hotter when N₂ is the diluent rather than CO₂, at lower steam concentration, and at higher oxygen concentration. Photographs also suggest that faster conversion is achieved at higher oxygen and/or steam concentrations. Implications of these observations are discussed, including differing transport properties and the importance of gasification reactions in an oxy-fuel environment.