Simple removal of dioxins by injecting combustion gas into water

• Published in: Journal of material cycles and waste management Vol. 9; no. 1; pp. 80 - 89
• Main Authors: Kawabata, Hirotoshi, Yabunaka, Bokka, Tanabe, Masayuki, Usui, Tateo, Marukawa, Katsukiyo, Hara, Shigeta, Tanaka, Toshihiro
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.03.2007
• Subjects: Bubbles; Combustion; Dioxins; Emissions; Exhaust emissions; Furans; Gases; Heat treating; Incinerators; Injection; Pesticides; Polyvinyl chloride; Surface area
• ISSN: 1438-4957; 1611-8227
• DOI: 10.1007/s10163-006-0162-9

A simple, low-cost method for suppression of dioxins/furans (hereinafter referred to as dioxins) is required because many middle- and, especially, small-scale incinerators have fallen into disuse or have been dismantled because of the high running and system costs of measures for the suppression of dioxins. Therefore, the purpose of the present study was to develop a simple removal method for dioxins from combustion gas and to evaluate the basic removal rate of dioxins. The removal method for suspended matter in a gas mixture (cold model) and dioxins in exhaust gases (hot model) has been investigated by means of gas injection into water, the mechanism of which is that the suspended matter in the gas gathers at the gas-liquid interface. In the cold model, the removal ratio of fine particles (R^sub P^) by gas injection into water was reproduced well by the following equation: R^sub P^ (%) = 100 × {1-exp(-0.8·S^sub S^·t^sub C^)}, where S^sub S^ (cm^sup 2^/cm^sup 3^) is the specific surface area of bubbles and t^sub C^ (s) is the residence time of bubbles in water. The removal ratio of fine particles increased as the product S^sub s^·t^sub C^ increased. In a hot model using the exhaust gas from combustion experiments of polyvinyl chloride, the removal ratio of dioxins (R^sub D^) by injecting the exhaust gas into water was estimated by the following equation: R^sub D^ (%) = 100 × {1-exp(-0.8·S^sub S^·t^sub C^·C^sub D0^ ^sup 0.07^)}, where C^sub D0^ [ng/cm^sup 3^ (at standard temperature and pressure)] is the dioxins concentration in the exhaust gas before injection into water. R^sub D^ depends greatly on the specific surface area of bubbles and the residence time of the bubbles in water, and only weakly on the dioxins concentration in the exhaust gas. Injection of the exhaust gas into water has been shown to be effective and was evaluated as a simple method for the removal of dioxins from exhaust gas.[PUBLICATION ABSTRACT]