Updated: July 2002

1. Description of the System

The system decomposes and removes dioxins in exhaust gases using a catalyst in a relatively low temperature zone, (200ºC or lower). Adding ammonia means selective reduction of nitrogen oxides can be performed at the same time.
The chemical reaction is as follows:
- Decomposition reaction of dioxins for T4CDD is:
C12H4Cl 4O2+11O2 -> 12CO2+4HCl
- Selective reduction of nitrogen oxides for NO is:
4NO+4NH3+O2 -> 4N2+6H2O
The system is installed after precipitators such as bag filters for stable performance.

Flow Sheet

2. Characteristics

1. Uses a catalyst that is based on conventional SCR catalysts which improve activation in relatively low temperature zones (200ºC or lower). This achieves superior processing of dioxins in low temperature zones.
2. Since decomposition and removal are in low temperature zones, the amount of steam used for re-heating is reduced, and it is even possible to configure a system without a re-heater.
3. Uses an adapted honeycomb catalyst that is not easily clogged with dust.

The honeycomb catalyst

3. Performance

Decomposition rate of dioxins is shown as follows:
Decomposition rate measured in the low temperature zone (160ºC to 180ºC) and at SV value 3000 to 4000 [m³N/m²h] is approximately 90%.

Dioxin decomposition

De-NOx is shown as follows: the De-NOx rate tends to become lower in low temperature zones. Therefore, for the De-NOx rate, the SV value is adjusted according to the applied temperature.

DeNOx

4. Adaptive Field and Objects to be Treated

1) Exhaust gases from waste incineration plants
2) Exhaust gases from gasifier and melting furnace plants
3) Exhaust gases from ash-melting furnace plants

5. Others

Delivered plants using this system
Municipal waste incineration plants: 3 plants
Industrial waste incineration plants: 2 plants