Author(s)

K. SUZUKI, S. NAGANO & S. FUJITA

Abstract

Hydroxyl sodalite (Na8Al6Si6O24(OH)2) and hydrogrossular (Ca3Al2(SiO4)0.8(OH)8.8) were investigated for the purpose of developing new ecofunctional ceramics with removal performance for toxic substances present in waste combustion gas. It was found that these materials had functions of chlorine fixation, copper fixation and the control of dioxin formation. Hydroxyl sodalite had nanometer-sized micropores (β-cage) in the structure, and the chloride ions were fixed in the pores above 400◦C. The amount of chlorine that was fixed increased with increasing reaction temperature and was greatest, 7.3 wt%, at 800◦C. The fixation of the copper progressed by the substitution with sodium ion, and the substitution quantity increased with increasing reaction temperature. The amount of copper fixed as CuO at 900◦C was 10.5 wt%. On the other hand, hydrogrossular changed to the mayenite phase (Ca12Al10Si4O35) after heating to above 700◦C. Mayenite had micropores in the structure, which were fixed by the chloride ions. A drastic decrease in the concentration of dioxins was confirmed by introducing the ecofunctional ceramics, hydroxyl sodalite and hydrogrossular, in the municipal solid waste incineration.

Keywords

chlorine, copper fixation, dioxin, hydrogrossular, hydroxyl sodalite, oxidative catalyst, waste combustion gas