Abstract: In order to obtain the design principle of oxy-fuel boiler. The heat transfer of 200 MW boilers adopting oxy-fuel combustion is calculated and analyzed in this paper. The result shows that compared with air-firing, the radiant heat transfer of oxy-fuel combustion will be enhanced in high flue gas temperature zone due to the higher concentration of CO2 and H2O. While in the low flue gas temperature zone, the convective heat transfer will weaken due to the decrease of flue gas volume flow rate. Based on the analysis of heat transfer characteristics, the design optimization method on flue gas flow section and heat transfer areas for oxy-fuel combustion boiler is proposed. Under the condition of the oxygen concentration at 26%, the flow section area in oxy-fuel combustion boiler can be reduced by 15%~21% in dry cycles and 13%~24% in wet cycles. And at the same time, the heat transfer area can be decreased by 9%~32% in dry cycles and 7%~35% in wet cycles. In oxy-fuel combustion boilers, the flue gas flow velocity can soon meet the design requirements with the heat transfer consistent with air-firing boilers. This work is supported by Shenhua Group Technology Innoration Project No.[2011]368.

Key words: boiler, oxy-fuel combustion, dry cycle, wet cycle, heat transfer characteristics, design optimization