TREATMENT OF FLY ASH

摘要

A method and a plant for treatment of fly ash are described, wherein heavy metals are separated and wherein there is formed a leaching resistant slag. The treatment takes place in a reactor (2) and the fly ash is introduced into an oxidizing gas stream which is heated to at least 2500 DEG C in a plasma generator (1). The fly ash melts and forms liquid drops of slag. A carbonaceous or hydrocarbonaceous material is added to the gas stream. This burns and supplies extra energy to the process. The ratio of oxygen and carbon is regulated in such a manner that the ratio CO2/CO + CO2 is kept within the limits 0.4 - 0.9. Heavy metals in the fly ash such as zinc and lead are thereby reduced and pass into the gas phase. The gas is discharged from the reactor (2), cooled and washed and metal oxides are separated. The gas will also contain chlorine and sulphur which are separated in a gas scrubber. The slag is collected in the bottom of the reactor (3) and can be continuously tapped via a slag lock (9). The slag's content of CaO and SiO2 can be regulated by the admixture of a slag-forming material with a high content of SiO2. A slag is thereby obtained with excellent leaching resistance.