Comparison of Dioxin and Heavy Metal and Other Pollutants Emission Characteristics from Domestic Solid Waste Gasifiers in Typical Arid and Humid Regions

Abstract This study compares the emission characteristics of heavy metals, dioxins, and other pollutants from two small-scale gasification incinerators treating rural domestic waste in different regions of China. The results showed that Facility A exceeded the emission limits for NO x and total hydrocarbons (THC) in the flue gas, with maximum concentrations of 698 and 521 mg/Nm 3 , respectively, and significant fluctuations were observed during the monitoring period. The concentrations of heavy metals in the flue gas of Facility A were generally higher than those in Facility B, with Zn reaching a maximum of 449 µg/Nm 3 . On the first monitoring day at Facility B, the flue gas Tl concentration was 83.6 µg/Nm 3 , but it decreased rapidly over the following two days. Dioxin emission levels in the flue gas from both facilities were relatively low, ranging from 0.023 to 0.0512 ng TEQ/m 3 . In Facility A, 2,3,4,7,8-PeCDF accounted for the highest proportion (17.84%) of all dioxin congeners in the flue gas. The concentrations of Zn, Ba, and Mn were generally high in both the slag and fly ash of Facility A. Dioxins showed significant enrichment in the fly ash of Facility A, with the highest concentration reaching 26,833 ng TEQ/kg, far exceeding regulatory standards. Among the fly ash congeners, 2,3,4,7,8-PeCDF was the most predominant, accounting for 20.31%. Finally, thermodynamic equilibrium simulations for NO x and incomplete combustion gases were performed using HSC Chemistry software. Comparison with measured values confirmed that the operating conditions of the secondary combustion chamber are strongly correlated with the generation of NO x and unburned gases. These results confirm that such small-scale facilities have developed considerably in recent years, and technologies capable of controlling environmental risks at a lower level have already emerged.