Inhibition of PM2.5 Emission from the Combustion of Waste Materials

Combustion is the main source of particulate matter with a diameter of 2.5 mu m or less (PM2.5). Thus, effective and economical combustion control methods are necessary. In our previous research, we observed that certain waste may exhibit an inhibitory effect on PM2.5 emission. The current research aims to identify the types of waste with an inhibitory effect and to determine their mechanism. We conducted co-combustion experiments in which plastic was mixed with paper, rag, sawdust, food waste, and glass. Among these materials, paper exhibited the most effective inhibitory effect, with a reduction of 4.35 mg/g, followed by rag (3.91 mg/g) and sawdust (2.07 mg/g). In contrast, food waste could increase the PM2.5 yield of the co-combustion system, whereas glass presented no evident inhibitory or stimulative effect. The inhibitory effects of paper and rag could be attributed to Ca in paper and Mg in rag. The addition of CaCO3 and representative Mg salts during combustion proved their inhibitory effects. MgSO4, CaCO3, and Mg(NO3)(2) could reduce the PM2.5 yield by 49.7, 32.9, and 18.9%, respectively, in the mix combustion system. The morphological analysis clearly showed the collision or coating between PM2.5 particles. This finding could account for the increase in the particulate size, which led to PM2.5 reduction.