ABSTRACT
This paper presents an experimental study on flame characteristics of O₂/CO₂ recycle combustion (or oxy-fuel combustion) with emphasis on radiative heat transfer and burnout behaviour. Measurements were carried out in a 100 kWth test unit which facilitates O₂/CO₂ combustion with real flue gas recycle. The tests comprises a reference test in air and two O₂/CO₂ test cases with different recycled feed gas mixture concentrations of O₂ (21 and 27 vol %) and CO₂ (79 and 73vol %). In-furnace gas concentration, temperature and total radiation (uni-directional) profiles are presented and discussed. The results show that the fuel burn-out is delayed for the OF 21 case compared to air-fired conditions as a consequence of the reduced temperature levels. Instead, the OF 27 case results in more similar combustion behaviour compared to the reference conditions in terms of in-flame temperature and gas concentration levels, but with significantly increased flame radiation intensity. The change in total emissivity and gas emissivity of the O2/CO2 environment is discussed by means of available models. The results suggest that the increased radiation intensity of the OF 27 case can partly, but not solely, be explained by an increased gas emissivity.