Turbulent flame propagation mechanism of polymethylmethacrylate particle cloud–ammonia co-combustion

Ammonia is a promising energy carrier for realizing a carbon-neutral society. In particular, solid particle cloud–ammonia co-combustion is considered as an efficient and feasible method to reduce CO2 emissions from the thermal power generation sector by using particle-fuel such as solid waste, biomass, and pulverized coal particles in combustors. However, the fundamental turbulent flame propagation mechanism of solid particle cloud–ammonia co-combustion remains unknow. Therefore, the present study intends to investigate and validate the general turbulent flame propagation mechanism of solid particle cloud–ammonia co-combustion. To achieve this aim, silica particle cloud–ammonia–oxygen–nitrogen mixing combustion, silica particle cloud–acetylene–air mixing combustion, and PMMA particle cloud–ammonia–oxygen–nitrogen co-combustion experiments were conducted. The results showed that the turbulent flame propagation velocity of silica particle cloud–gas-fuel–oxidizer mixing combustion is lower than that of pure gas-fuel–oxidizer combustion. However, the comparison of the turbulent flame propagation velocity of PMMA particle cloud–ammonia co-combustion and that of pure ammonia combustion, showed that whether the flame propagation of the co-combustion was higher than that of the pure ammonia combustion was dependent on the equivalence ratio of the ammonia-oxidizer. Therefore, the consistency of the results between the current study of PMMA particle cloud–ammonia co-combustion and the previous study for coal particle cloud–ammonia co-combustion indicates the turbulent flame propagation mechanism of solid particle cloud–ammonia co-combustion is dominated by the negative effect of the heat sink by unburned particles and the local equivalence ratio increment effect in the preheat zone of the flame front by the addition of the volatile matter, and that the positive effect of radiation from soot particles has little effect on the turbulent flame propagation of co-combustion for small-scale flames. Further, the influence of the heterogeneous combustion of char particles on the turbulent flame propagation of solid particle cloud–ammonia co-combustion is minor because of its slow combustion process. Based on the validated turbulent flame propagation mechanism of co-combustion, new numerical simulation models for solid particle cloud–ammonia co-combustion can be developed in the future.