This paper describes a promising oxygen-based process (oxy-combustion process) enabling CO_2 capture from coal-fired power plants. The technology involves the replacement of the combustion air by pure oxygen diluted in recycled flue gases, and will be applicable with minimal pressure-part modification to existing pulverized coal-fired boilers. The oxygen and recycled flue gas levels are adjusted to achieve flame and furnace temperatures compatible with today's materials. Oxy-combustion performance using PRB coal with flue gas recirculation has been successfully demonstrated on a 5-million Btu/hr pilot combustor. The results were compared to air-blown combustion. Various burner parameters were varied to obtain maximum benefits from the oxygen/flue gas configuration. The overall combustion characteristics were comparable to air firing. The NO_x emissions from oxy-combustion tests were significantly lower by nearly 65% when compared to the air-blown combustion, and the CO_2 content in flue gas was increased from 15% to 80% in O_2-fired mode. The flue gas volume exiting the boiler was reduced by nearly 70%, thereby improving the economics of efficient capture, reuse, and sequestration of carbon dioxide. This paper describes the experimental results of oxy-combustion from the pilot-scale boiler simulator. Various aspect of oxy-combustion such as flame shape, length, temperature, and emissivity will be discussed. Heat transfer from the flame in the boiler and in the convection pass will be reviewed.
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