Updated: July 2002

1. Purpose

Dioxins exhausted from the stack of municipal refuse incinerators, which is the mass occurring in the incinerator, are almost decomposed at the part of burning at elevated temperature of exhaust gas. But they recombine at the process of heat utilization facility because they are not decomposed completely. A heat exchange technique from exhaust gas with air-preheater is adopted generally as a method that recover heat at semi-continuous incinerator and mechanical batch incinerator. There is suspicion in this method that dioxins are decomposed in air preheater. But heat utilization at semi-continuous incinerator and mechanical batch incinerator is important subject. For meeting these subjects, an adsorption removal technique with activated carbon is adopted as a method that reduces dioxins. We have combustion control technique by fuzzy and second combustion technique, as elimination technique of dioxins, but these techniques are not enough to reduce dioxins concentration at B.F. outlet less than 0.1ng-TEQ/m³N. Absorption removal technique of dioxins with activated carbon injection is thus expected to be the solution for dioxins elimination while ensuring the heat utilization.

Fig.1 Injecting equipment

Fig.2 Outline plant

2. Characteristic and Performance of the System

Either existing or new incinerator can realize this system only with set up of the injecting point of activated carbon in front of B.F. The space of the injecting equipment is about 4m×3m×4mH.
Dioxins concentration at B.F. outlet can be reduced by 0.1ng-TEQ/m with 150-200mg/m³N injection volume. The property and injection volume are shown in the following.

3. Theory

Dioxins at gas-side are also adsorbed by the activated carbon, which are scattered in the solid deposit layer at the surface of B.F. filtering cloth, removed and recovered as collected dust.

4. Appropriate Field

- New Type Municipal Waste Incinerator
- Existing Type Municipal Waste Incinerator
- Various Industrial Waste Incinerator
- Melting furnace

5. Effect

1) Although the heat recovery quantity for preheating increase as much as possible, dioxins concentration at B.F. outlet can be reduced under 0.1ng-TEQ/m³N by the absorption process with injecting activated carbon. (The result is 0.03-0.08ng-TEQ/m³N.)
2) The necessity of reconstruction is little for existing type incinerator with B.F.
3) Dioxins in collected dust are reclaimed to final disposal site after disposed by ash solidification equipment. Dioxins are disposed stably there because they are insoluble in water.