ABSTRACT
This paper presents experiments on oxy-fuel combustion carried out within the ENCAP project. The experiments were performed in a coal-fired 20 kW unit and in a gas-fired 100 kW unit and the measurements focus on combustion and flame characteristics including emission formation, fuel burn-out, ash characterization and radiation characteristics. The 100 kW gas-fired experiments show that the temperature of the combusting flow is drastically decreased for the OF 21 case (21 vol. % O2 in the feed gas stream, the rest being CO₂) compared to air-fired conditions. The temperature reduction leads to a suppressed development of the OF 21 flame, which exhibits a poor burn-out rate compared to the reference flame as well as the OF 27 flame. In the OF 27 case (27 vol. % O₂ in the feed gas stream) the combustion temperatures approach those of the air fired reference case. In the OF 27 case, however, the flame radiation intensity increases with 25 to 30 %, indicating significantly higher flame emissivity than for the air-fired flame. The coal combustion tests in the 20 kW once through reactor unit shows that the NOx and SO₂ emissions are similar for the air and OF 27 case for both coals tested.