Mercury Behaviour in Flue Gases

Abstract

Mercury in the flue gas from waste incineration is predominantly in the vapour phase at temperatures down to 140 °C. Only a small portion of the mercury is metallic Hg°, most of it is oxidized, which has a high vapour pressure at these gas temperatures. Oxidized mercury is absorbed by fly ash and will be captured on fabric filters. By injecting fly ash and lime before a fabric filter a high degree of collection can be achieved, both for hydrochloric acid and for mercury. Up to 90% of the mercury can become attached to the dust. By optimizing the operation and with efficient dust removal it is therefore possible to limit mercury emissions to less than 0.3 g ton-1 of incinerated waste.