Revealing the Mechanism of Dioxin Formation from Municipal Solid Waste Gasification in a Reducing Atmosphere

Abstract

Gasification is an effective technology for the thermal disposal of municipal solid waste (MSW) with lower dioxin emission compared to the prevailing incineration process. Nevertheless, the mechanism of dioxin formation in the reducing atmosphere during the gasification process was seldomly explored. Herein, the effects of the atmosphere, temperature, and chlorine source were systematically investigated in terms of dioxin distribution. With CO2 and H2O as gasification agents, a reducing reaction atmosphere was formed with abundant H2 which effectively suppressed the generation of C–Cl, contributing to a substantial decrease of dioxin concentration by ∼80% compared to the incineration process. The formation of dioxin was favored at temperatures below 700 °C with its peak concentration achieved at 500 °C. It was unveiled that inorganic chlorine played a dominant role in the reducing atmosphere, with a lower proportion of C–O–C/O–CO on residual slag compared to an oxidizing atmosphere. Additionally, the generated H2 reduced the concentration of dioxins by attacking C–Cl and inhibiting the crucial Deacon reaction for dioxin formation, validated by density functional theory calculation. Eventually, the formation route paradigm and the reaction mechanism of dioxin formation from MSW gasification were revealed, facilitating and rationally guiding the control of dioxin emission.

Reimagining plastics waste as energy solutions: challenges and opportunities

“…Others, including China, India, Thailand, Turkey, and Mexico, are beginning to explore similar avenues. Nevertheless, the process is not without controversies due to excessive dioxin 30 and CO 2 emissions. Stringent exhaust treatment and CO 2 capture and storage (CCS) are necessary to curb these emissions.…”

Br-to-Cl Transformation Guided the Formation of Polyhalogenated Dibenzo-p-dioxins/Dibenzofurans

“…The ratios of PXDDs to PXDFs (D/F) ranged from 0.12 to 0.27 for PCDD/Fs and 0. 08 to 0.37 for PBDD/Fs (Figure S2b), presenting the formation characteristics of PXDD/Fs during combustion systems, with D/F ratios <1 . Specifically, PCDFs are predominantly composed of high-chlorinated congeners, such as 1,2,3,4,6,7,8-HpCDF (accounting for 19.6–23.2%) and OCDF (accounting for 15.8–20.2%) (Figure c).…”

“…08 to 0.37 for PBDD/Fs (Figure S2b), presenting the formation characteristics of PXDD/Fs during combustion systems, with D/F ratios <1. 27 Specifically, PCDFs are predominantly composed of high-chlorinated congeners, such as 1,2,3,4,6,7,8-HpCDF (accounting for 19.6−23.2%) and OCDF (accounting for 15.8−20.2%) (Figure 2c). Among PBDD/Fs, low-brominated PBDFs, such as 2,3,7,8-TBDF, are the dominant PBDF contribution of total concentrations (Figure 2d).…”

Adsorption Behaviors of H2S and CO2 on the Synergistic Removal of HCl and Hg0 in Pyrolytic Waste Plastic Gas on 4Ca-1Co/CA

“…However, organic solid wastes containing elements such as chlorine and mercury (such as polyvinyl chloride and biomass) would generate various pollutants such as HCl and gaseous mercury during pyrolysis. HCl would corrode equipment, pipelines, and valves, causing huge risk. , High Hg 0 concentrations could destroy aluminum compression and purification devices through metal embrittlement.…”