Oxycombustion process in pulverized coal-fired boilers: a promising technology for CO_2 capture

摘要

This paper describes a promising oxygen-based process (oxycombustion process) enabling CO_2 capture from coal-fired power plants. The technology involves the replacement of the combustion air by pure oxygen diluted in recirculated flue gases, and will be applicable with limited required adaptations to existing designs of pulverized coal-fired boilers. Oxycombustion performance using PRB coal with flue gas recirculation (O_2/CO_2 environment) has been successfully demonstrated and characterized on a 1.5 MWth plant and compared to those previously measured in operations using air as the oxidant. Optimization of the boiler parameters was performed to obtain maximum benefits from the oxygen/flue gas configuration. An important parameter impacting the combustion performance was the flue gas recirculation flow rate. The overall combustion characteristics were comparable to the air firing case. The NO_X emissions from oxycombustion tests were significantly lower by nearly 70% than the air-fired case, and the CO_2 content in flue gas was increased from 15% in air-fired case to eventually 80% in O_2-fired modes. The flue gas volume exiting the boiler has been shown to reduce by nearly 70%, thereby improving the economics of efficient capture, reuse, and sequestration of carbon dioxide. Economic studies indicate that the cost of electricity produced via oxycombustion of coal is potentially 20% lower than conventional technology when CO_2-capture is taken into consideration.