Co-combustion strategy of waste energetic materials with pine sawdust for efficient NOx emissions reduction

Abstract

Excessive NOx emissions during incineration of waste energetic materials (EMs) is harmful to the environment. Co-combustion technologies with biomass have demonstrated remarkable advantages in reducing NOx emissions. Herein, the co-combustion characteristics and NOx emission behaviors of waste double-base propellant (DP) and pine sawdust (PS) were investigated via thermogravimetric (TG) and fixed-bed experiments firstly. Meanwhile, the general full factorial design (GFFD) was performed to explore the effects of different factors on the NOx emissions of co-combustion. The interaction mechanism between DP and PS was discussed as well. Moreover, the interaction of three other typical waste EMs (RDX, TNT, and triple-base propellant) co-combustion with PS in NOx emissions was studied utilizing orthogonal experiments. The kinetics under air atmosphere indicated that the mixing of PS slightly diminished the combustion reactivity of DP, conversely, the remaining residue of DP combustion promoted the combustion of PS. Oxygen concentration, temperature and mixing ratio all had significant effects on NOx emissions of co-combustion between DP and PS, the degree of effect decreased in turn. Overall, the mixing of PS all suppressed the NOx emissions with significant synergistic effects, optimal synergistic effect at 20 wt% of PS mixing. The synergistic effect in oxygen environment was lower than that in oxygen-free environment. Meanwhile, increasing temperature contributed to enlarging the synergistic effect. Additionally, there was synergistic effect of TNT and PS co-combustion, whereas RDX, TP exerted inhibition effect of co-combustion with PS. Therefore, the co-combustion strategy of waste EMs with PS provides reliable data support and guidance for the control of NOx emissions during the incineration of waste EMs.