NH3/O2 premixed combustion in a single bubble of fluidized bed

Abstract

As a carbon - free, economical and safe energy carrier, ammonia is favoured and has been used in many different applications for combustion. However, there are few reports of NH3 being burned in a fluidized bed. This investigation of the premixed combustion of NH3 and O2 in a single bubble inside a fluidized bed was done both experimentally and with CFD-DEM simulations incorporating a skeletal mechanism of 98 elementary reactions. The results show that premixed combustion of NH3 and O2 occurred in a growing bubble. Quenching became evident at a bubble's edge. Combustion became unstable at low equivalence ratios. In addition, the equivalence ratio significantly affected the ignition delay, flame's propagation velocity, as well as the concentrations of gaseous species in the bubble and emulsion phases. Increasing bed temperature reduced the ignition delay. Nitrogen, as the background fluidising gas, exerted a negative impact on combustion, because of N2 diffusing from the emulsion to the bubble phase. The combustion of NH3/air in the bubble phase of a fluidized bed was difficult to happen in the absence of a catalyst or co-combustion with an inflammable fuel.