Noboru Tanikawa* and Kohei Urano**

* Tokyo Metropolitan Research Institute for Waste Management
** Laboratory of Safety and Environmental Engineering, Faculty of Engineering, Yokohama National University

+ Correspondence should be addressed to Noboru Tanikawa:
(2 Aomi, Koto-ku, Tokyo 135-0064 Japan)

Abstract

The reduction effect on mercury emission by the decrease of mercury content of dry batteries and the removal methods of HCl and SO2 were investigated at municipal incinerators. Changes of the removed amounts of mercury were estimated in the ward areas of Tokyo from 1986 to 1996 and all over Japan in 1992. By comparing concentrations of mercury in flue gas from a municipal incinerator in 1986 and 1993 which had adopted the powder CaCO3 injection method and the electrostatic precipitator (EP), we found that the mean concentration of mercury had gone down from 0.25 mg/m3N to 0.08 mg/m3N and the appearance frequency of high concentration peak of mercury had decreased remarkably. Mercury was removed by the treatment methods of HCl and SO2. The mercury removal efficiencies for the CaCO3 powder injection method, the wet scrubber method, the wet scrubber method added to a chelate compound which was adopted with EP, and the filter method were estimated to be 35, 65, 90, and 75 %, respectively. In the ward areas of Tokyo, the emitted amount of mercury in 1996 decreased to about one sixth of that in 1986 because of the decrease of mercury content of dry batteries and the adoption of removal methods of HCl and SO2, though the incinerated amount of waste increased by 1.27 times. In overall Japan, the emitted amount of mercury was estimated to be 17t/y and the removed amount of mercury by the flue gas treatment was estimated to be 9t/y, in 1992.

Key words: municipal waste incineration, mercury, emission, flue gas treatment, reduced amount, dry battery