Division 1.10.1.3 SO2, HCl, and HF emissions

Dry powder or a suspension/solution of an alkaline reagent (e.g. lime or sodium bicarbonate) is introduced and dispersed in the off-gas stream. The material reacts with the acidic gaseous species (e.g. SO₂) to form a solid which is removed by filtration (bag filter or electrostatic precipitator). The use of a reaction tower improves the removal efficiency of the scrubbing system. Adsorption can also be achieved by the use of packed towers (e.g. coke filter).

For existing plants, the performance is linked to process parameters such as temperature (min. 60 °C), moisture content, contact time, gas fluctuations and to the capability of the dust filtration system (e.g. bag filter) to cope with the additional dust load

In the wet scrubbing process, gaseous compounds are dissolved in a scrubbing solution (e.g. an alkaline solution containing lime, NaOH, or H₂O₂). Downstream of the wet scrubber, the off-gases are saturated with water and a separation of the droplets is carried out before discharging the off-gases. The resulting liquid is further treated by a waste water process and the insoluble matter is collected by sedimentation or filtration.

For existing plants, this technique may require significant space availability