Division 1.6.3 SOx emissions

The technique involves the addition of an absorbent in dry form directly into the kiln (fed or injected) or in dry or wet form (e.g. hydrated lime or sodium bicarbonate) into the flue-gases in order to remove SO_x emissions. When absorbent is injected into the flue-gases, a sufficient residence time between the injection point and the dust collector (fabric filter or ESP) must be provided in order to obtain an efficient absorption.

For rotary kilns, absorption techniques may include:

• Use of fine limestone: At a straight rotary kiln fed with dolomite, significant reductions in SO₂ emissions can occur with feedstones which either contain high levels of finely divided limestone or are prone to break up on heating. The finely divided limestone calcines are entrained in the kiln gases and remove SO₂ en route to, and in, the dust collector.

• Lime injection into the combustion air: A patented technique (EP 0 734 755 A1) which removes SO₂ emissions from rotary kilns by injecting finely divided quick or hydrated lime into the air fed into the firing hood of the kiln