Inhibition of Hazardous Substances Formation in a Combustion Furnace by Centrifugation and Recombustion Method of Fly Unburned Matters at High Temperatures

Experiments to inhibit the formation of hazardous substances such as benzenes and dioxins in a combustion furnace were carried out by the centrifugation and recombustion method of fly unburned matters (fly carbonaceous matters (C*)) in an exhaust gas at high temperatures. Total dioxin’s and Cl5 benzene’s concentrations in the exhaust gas have a good correlation with the number of the fly C* remaining in the exhaust gas, and their concentrations increase as the number of the fly C* rises. Total dioxin’s and Cl5 benzene’s concentrations after the centrifugation and recombustion with the present cyclone reduce to 10% and 20% of their initial concentrations in the exhaust gas from combustion furnace, respectively, in proportion to the decrease in the fly C*. On the other hand, in the case of low dioxin’s and benzene’s concentrations in the exhaust gas under the complete combustion conditions their reduction ratios become worse. The reason why their reduction ratios decrease is considered a decrease in the partial separation efficiency for fine particles in the present cyclone, which is attributed to the increase in the relative ratio of the fly C* with the sizes smaller than 2μm under the complete combustion conditions. The predictive equation of the partial separation efficiency at high temperatures obtained for the present cyclone of a small size indicates that the reduction ratios of dioxins and benzenes are much improved by using the cyclone of larger sizes and increasing in the inlet velocity of the exhaust gas to the cyclone. The present centrifugation and recombustion method of the exhaust gas at high temperatures is expected to be useful for the actual incineration plants.