Q2 What is the role of the gasification and melting furnace in MSW incineration facilities?
Types of MSW treatment facilities
The main method used for municipal solid waste treatment today is immediate landfill disposal (Pattern A) or incineration (Patterns B & C). When incineration is used (Pattern B), the landfill volume is reduced to about 10% of immediate lamdfill disposal (Pattern A). If ash melting or gasification and melting (Pattern C) is carried out, the landfill volume is reduced to about 2-3%.
If the incinerated ash is to be melted following incineration, an ash melting furnace is attached to the incinerator. Because high temperatures of over 1200°C are required to melt ash, the ash melting furnace needs to be powered by an energy source such as electricity or fuel. A gasification and melting system uses the energy of the waste itself, making it an integrated system for ash melting with minimum added energy.
Currently the mainstream methods in Japan use a stoker-type incinerator (+ ash melting furnace), fluidized-bed gasification and melting furnace, and shaft furnace-type gasification and melting furnace.
MSW treatment methods
| Incinerator | Stoker (Grate) type |
|---|---|
| Fluidized-bed type | |
| Rotary kiln |
| Ash melting furnace (auxiliary) |
Electric | AC arc |
|---|---|---|
| Electrical resistance | ||
| Plasma | ||
| Fuel burner | Surface melting | |
| Swirl-flow | ||
| Rotating type | ||
| Coke bed |
| Gasification and melting furnace | Fluidized-bed type |
|---|---|
| Shaft furnace type | |
| Kiln type |
The development and spread of gasification and melting systems in Japan
Dioxin emissions from MSW incineration facilities became a problem in Japan in the early 1990s. At the same time solutions were sought to prevent the leaching of heavy metals from incinerated ash into the ground, and also alleviate critical problem of shortage of landfill disposal site. The technology of melting MSW incinerated ash became of interest to the national government, as it promised to reduce the level of dioxins in incineration byproducts, prevent the leaching of heavy metals, and achieve both landfill volume reduction and effective energy use. In the latter part of the 1990s, dioxin decomposition was achieved through development of high-temperature melting technology, and the gasification and melting system gained attention for its ability to utilize the energy in the waste itself for melting. Various manufacturers built pilot facilities and developed them, and now there are approximately 100 gasification and melting facilities operating across Japan.
