Ash system
The burnt out sterile bottom ash leaves the grate through a refractory lined clinker outlet. Standard cooling is achieved in a water tank, equipped with a steel belt conveyor or pusher system transporting the bottom ash from the tank. The water tank also achieves an air-tight seal between the hot furnace chamber and the cold and clean ambient air in the building.
Grate siftings and the conveyor system
Some ash and heavy, fine particles such as stone, sand, glass and molten metals (called grate siftings) fall down through the air gaps in the grate surface into the combustion air hoppers under the grate. This small quantity of grate siftings is similar in properties to the bottom ash, and the grate siftings are normally mixed into the bottom ash and transported out from the plant via a common conveyor system.
Magnetic separators and rotating screens remove scrap iron and over-size ingredients
Scrap iron and over-size items are removed from the bottom ash by means of magnetic separators and rotating screens. The resulting quality of the bottom ash permits its use as secondary aggregate building material, for example as road or parking lot foundation.
The bottom ash is normally aerated and carbonised in big piles by atmospheric air for several months before recycling.
