Emission Control of Unintentionally Produced POPs at Low Temperature in Aluminum Alloy Smelting Plants

Abstract

This study examined emissions of unintentionally produced persistent organic pollutants (POPs) from fabric filters in aluminum alloy smelting plants. The results are expected to indicate means of reducing these emissions from sources, such as metal smelting furnaces, where emission control by existing exhaust gas treatments is insufficient. Measurement of dioxins and polychlorinated biphenyl (PCB) concentrations in fabric filters revealed their formation at around 100℃, at which temperatures these by-products were presumed to be formed only slightly. In laboratory experiments using fly ash collected from fabric filters, formation was confirmed below 100℃ by long-term heating of more than 18 hr or preheating above the set temperature. This heating was regarded as necessary for reactivation of the catalysts in fly ash. Comparison of fly ash samples collected from three plants elucidated that water-soluble chlorides such as potassium chloride were the principal source of chlorine during formation at low temperatures. This comparison led to the inference that water spraying of flue gas is effective for reducing dioxins and PCB emissions from aluminum alloy smelting plants.