Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Retrofitting coal power stations to minimize carbon dioxide emissions

Carbon dioxide emissions could be eliminated from coal power stations if the carbon dioxide were to be collected and liquefied when the fuel is burnt using oxygen enrichment and flue gas recirculation techniques. However, extensive practical and modelling studies carried out in this project have shown that the technique is technically feasible but too expensive to be considered under present economic conditions.

Laboratory tests were performed with oxygen enrichment and flue gas recirculation (for cooling purposes) in a 140 kW(th) burner to establish maximum carbon dioxide enrichment levels, carbon dioxide levels and fouling. Measurements were taken of efficiency, pollutants, and suitability for installation. Using mathematical and physical modelling techniques, a 35 MW(th) low carbon dioxide demonstration burner was then developed that was considered to be representative of the majority of current conventional coal burners. The main issues associated with retrofit conversion of an existing coal-fired boiler were identified, including boiler start-up and change-over, retrofit changes to boiler configuration and equipment, and air leakage into the furnace. This last was found to be the most significant practical obstacle to successful oxygen/flue gas recirculation operation. Ultra low air ingress levels are needed to maintain carbon dioxide concentrations high enough for efficient operation of the flue gas liquefaction process. Existing balanced draught boilers cannot deliver such low ingress levels unless they are modified to pressurised furnace operation, which would cause significant financial and technical repercussions. Overall thermal efficiency was predicted to fall from 37 % for a conventional system to 23 %, mainly because of the power consumption of the oxygen separation and carbon dioxide liquefaction plants.


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