Decomposition of organochlorine compounds in flue gas from municipal solid waste incinerators using natural and activated acid clays

Abstract

High-temperature particle control (HTPC) using a ceramic filter is a dust collection method without inefficient cooling and reheating of flue gas treatment; thus, its use is expected to improve the energy recovery efficiency of municipal solid waste incinerators (MSWIs). However, there are concerns regarding de novo synthesis and a decrease in the adsorptive removal efficiency of dioxins (DXNs) at approximately 300°C. In this study, the effect of natural and activated acid clays on the decomposition of monochlorobenzene (MCB), one of the organochlorine compounds in MSW flue gas, was investigated. From the results of MCB removal tests at 30–300°C, the clays were classified as adsorption, decomposition, and low removal types. More than half of the clays (four kinds of natural acid clays and two kinds of activated acid clays) were of the decomposition type. In addition, the presence of Cl atoms detached from MCB was confirmed by washing the clay used in the MCB removal test at 300°C. Activated acid clay was expected to have high dechlorination performance because of its proton-rich-composition, but only two clays were classed as decomposition type. Conversely, all the natural acid clays used in this work were of the decomposition type, which contained relatively higher di- and trivalent metal oxides such as Al2O3, Fe2O3, MgO, and CaO. These metal oxides might contribute to the catalytic dechlorination of MCB at 300°C. Therefore, natural and activated acid clays can be used as alternatives for activated carbon at 300°C to remove organochloride compounds such as DXNs. Their utilization is expected to mitigate the latent risks related to the adoption of HTPC, and also to contribute to the improvement of energy recovery efficiency of MSWI.ImplicationsThe effect of natural and activated acid clays on MCB decomposition was investigated to evaluate their suitability as materials for the removal of organochlorine compounds, such as DXNs, from MSWI flue gas at approximately 300°C. More than half of the clays used in this study showed the decomposition characteristics of MCB. The presence of Cl atoms in the clay used in the MCB removal test at 300°C proved the occurrence of MCB decomposition. The results of this study suggest a novel flue gas treatment method to establish high-energy efficient MSWI systems.