experimental and numerical investigations on a swirl oxycoal flame

the oxyfuel combustion technology has gained increased interest as a promising option for carbon capture and storage (ccs) in the last few years. the substitution of air by a mixture of recylced flue gas (rfg) and oxygen, however, is followed by changes in the process of pulverized fuel (pf) combustion as well as in the heat transfer inside the furnace. at rwth aachen university, research was conducted to investigate the underlying mechanisms governing the pf oxy-combustion and the impact of this process on burner and furnace designs with respect to industrial applications. starting with experiments using a pulverized coal swirl burner designed for air combustion, measures were developed for an aerodynamical stabilization of an oxycoal swirl flame. computational fluid dynamics (cfd), based on adapted models for pf oxy-combustion, was used as a design tool for development of swirl burner which was successfully tested in the oxycoal test facility at rwth aachen. this burner allows a stable oxyfuel combustion within wide range of oxygen content in the o₂/rfg mixture (from 18 to > 30 vol.-%). further numerical simulations of a 1210 mw_th industrial boiler oxy-firing bituminous pulverized coal were performed with respect to retrofit. comparisons made between air-firing and oxy-firing mode show that the radiative heat flux to the wall of a utility boiler is significantly influenced due to the changed optical properties of flue gases inside the oxy-firing utility furnace. a special focus was given to the oxygen concentration that is required to achieve similar heat transfer conditions as for conventional air fired furnaces.