Oxidative scrubber

Removal of volatile sulphur compounds:

• H₂S
• dimethyl sulphide CH₃SCH₃
• dimethyl disulphide CH₃S₂CH₃
  ...

Removal of formaldehyde CH₂O

Removal of nitrogen oxides NOₓ

Gas absorption and oxidation mechanisms

Oxidative gas scrubbing usually implies a transfer of volatile components from the gas phase to the liquid phase (water) with a subsequent chemical oxidation of the dissolved compounds. This oxidation is most often realised using sodium hypochlorite (NaOCl) or hydrogen peroxide (H₂O₂) as an oxidant.

When ozone (O₃) is used as an oxidant, the actual oxidation usually takes place in the gas phase before the scrubber, while the (partially) oxidised compounds are retained in the scrubber.

Process control, safety considerations and performance

Sodium hypochlorite (NaOCl) is most often used as an oxidant in oxidative scrubbers because of its high oxidising capacity and its easy availability. Oxidative scrubbing implicates an automated control of both the redox (ORP) and the pH value of the scrubbing water. Control of the pH is crucial in order to optimise kinetics, minimise chemical consumption, prevent chemical depositions and minimise the emission of unwanted compounds. Next to that, a refreshment of scrubbing liquid based on the electrical conductivity (EC) is needed.

In order to prevent the formation of toxic chloramines in the oxidative scrubber, NH₃ and amines should be removed from the waste gas in an upstream acid scrubber.

Removal efficiency

Under optimal conditions, very high (> 99%) removal efficiencies can be obtained in an oxidative scrubber for compounds as e.g. H₂S and CH₃SCH₃.