ABSTRACT
This paper highlights the results of experiments carried out during oxy-fuel combustion in a once through, electrically heated 20 kW PF test facility and modifications being carried out in a 500 kW PF combustor for oxy-fuel combustion with flue-gas recirculation.
In the once through 20 kW furnace, investigations were carried out for combustion with air as well as oxy-coal combustion with different concentration of oxygen. First, emissions at the end of the furnace with different concentration of oxygen during O₂/CO₂ firing are compared with air-firing. Then, in-flame profile measurements during air combustion and oxy-coal combustion with 27% O₂/73% CO₂ were performed to investigate and compare the combustion progress and emission formation of the different technologies. Further research topic addressed in the paper is the fuel NOx reduction potential during oxy-coal combustion with the application of oxidant-staging by utilising over-fire oxidant. Oxidant staging during oxy-coal combustion with 27% O₂/73% CO₂ demonstrated higher effectiveness in terms of NOx reduction when compared to air-staged combustion. Finally, formation and reduction of fuel NOX during oxidant staging is evaluated. In-flame emission profile measurement including HCN and NH₃ using FTIR were carried out. Results so far have indicated that fuel NOX formation and destruction in fuel rich condition during oxy-coal combustion is similar to air combustion. Concerning NOx formation and reduction mechanisms further detailed investigations are required.
Finally, future plans for Oxy-fuel research activities at IVD using a 500 kW coal combustion facility will be described, which will be one of the first coal and gas-fired pf oxy-fuel plants of this scale in Europe.