Effect of distributing combustion in the boiler on controlling flue gas temperature in pressurized oxy-fired systems with low flue gas recirculation

Pressurized oxy-combustion (POC) is introduced to minimize the energy penalty of the oxy-fired plants by allowing the latent heat recovery of the flue gas moisture. However, it is found that lowering the energy penalty highly depends on lowering flue gas recirculation (FGR) rate which can put the system under risk of high flue gas temperature. In this paper, the impact of distributing the combustion process along the height of boiler on controlling the peak flue gas temperature and peak heat flux is studied. It is found that distributing the combustion process is successful in lowering the flue gas temperature and wall heat flux while utilizing low FGR. The new system lowers exergy loss in the boiler and provides uniform and effective heat transfer to the working medium which in turn has the potential to reduce the cost of material usage. Finally, a practical design for a POC boiler under 30 % FGR is suggested.