Solvent scrubber

Removal of volatile organic compounds

• chloromethane (CH₃Cl), bromomethane (CH₃Br)
• carbon disulphide (CS₂)
• formaldehyde (CH₂O), butyraldehyde (C₄H₈O)
• aliphatic hydrocarbons

For some volatile compounds where acid, caustic, oxidative or reductive scrubbing is impossible, other chemical reactions can be induced in the scrubbing liquid upon the addition of specific chemicals. For the removal of some halogenated compounds and aldehydes, for example, a non-volatile and water-soluble amine-based solvent (R-NH2) can be added to the scrubbing liquid, inducing a chemical reaction (e.g. nucleophilic substitution) that converts the volatile compound into a non-volatile and biodegradable compound. It should be noted that kinetics strongly depend on the type of pollutant to be removed. Meaning e.g. that the kinetics of the nucleophilic substitution reaction for C1-compounds as bromomethane and chloromethane is much higher than for C2- and higher organohalogens.

Solvent selection and process control

The scrubber can be operated in a batch mode or with an automated dosing control system. Control of the pH is often crucial in order to optimise kinetics, minimise chemical consumption and prevent possible chemical depositions. The pH can be controlled by adding additional solvent (or in some cases NaOH). Next to that, a refreshment of scrubbing liquid based on the electrical conductivity (EC) is needed.

For the removal of e.g. aliphatic hydrocarbons, silicone oil or vegetable oils can be used as a scrubber liquid. Regeneration of the scrubbing liquid can be done by distillation or e.g. stripping towards a biotechnique.