Clean Air
Energy & Biomass Industry

Alkaline scrubber in the energy and biomass industry

In order to generate energy in a sustainable way, biomass is often fermented (e.g. manure, VGF waste, vegetable oil and wood). During the fermentation process biogas is produced, but also often unpleasant odours such as hydrogen sulphide (H₂S), for example. This is a strong smelling poisonous gas that is mainly known as the smell of rotten eggs. Because of its toxicity, even breathing in low concentrations of hydrogen sulphide for a longer period of time is dangerous. Hydrogen sulphide can, depending on other sulphur bound pollutants (mercaptans for example), be well removed from an air stream in an alkaline scrubber, sometimes an odour scrubber is an even better solution.

An alkaline gas scrubber can also remove acidic components from an air stream. By adding a base (lye), the pH of the washing water is raised and the acid forming components are neutralized by the lye, whereby salts are formed. The dosing of the base is done by means of a pH control, in most cases the pH value of the washing water varies between 7 and 12.

Depending on the salt formed, more or less washing water is discharged, this is measured on the basis of density and/or conductivity. The drainage can contain up to 15 % of salts and is discharged or evaporated for reuse.

Usually caustic soda (NaOH) is added as a base to the washing water. Often an alkaline scrubber is designed in combination with an odour scrubber. Besides caustic soda, a chlorine solution is dosed to oxidize all odour components. For more information please refer to the odour scrubber.