COMBUSTION CHARACTERISTICS OF COAL AND COKE UNDER HIGH OXYGEN CONCENTRATION OXY-FUEL CFBC CONDITIONS

摘要

Oxy-fuel circulating fluidized bed combustion (CFBC) is one of the emerging technologies for reducing green house gas emissions from fossil fuel power generation. To improve the overall efficiency of an oxy-fuel CFBC plant and reduce the cost of CO_2 capture, high oxygen concentration combustion is desired, as it means a lower flue gas recycle ratio and a smaller combustion chamber. To support the study of high oxygen concentration oxy-fuel research, combustion characteristics of different fuels were determined in a thermogravimetric analyzer (TGA). The fuels tested include lignite, bituminous coal, anthracite, and petroleum coke. Results showed that under the conditions tested, oxygen concentrations had only weak effect on the ignition of all the fuels. However, higher oxygen levels, as expected, reduced the burnout time. It was noticed that at typical CFBC combustion temperatures (～900 ℃), direct reaction between CO_2 and carbon is negligible, even though the CO_2 concentrations in the gas mixtures were high.