Condensation occurs when a saturated vapour comes into contact with a surface whose temperature is below the saturation temperature.
Condensation techniques are best suited for hydrocarbons and organic compounds having relatively high boiling points and high vapour phase concentrations These are commonly used in the web-offset printing, coating and textile industries where machine or knitting oils, plastisol’s and high boiling point printing inks are used. The visible emissions from these processes are often the cause of local resident complaints and are due to the high boiling point hydrocarbons and oils, which on discharge to atmosphere will condense to form sub-micron droplets creating a highly visible emission. The abatement system favoured is a combination of Exhaust Gas Cooling (to condense the condensable components using a film condensing technique); the ‘Eurokleen’ moving bed filter/coalescer (to coalesce the submicron droplets into larger droplets, collect and remove from the air stream) and a system to remove any remaining carry-over of droplets. Each of these techniques complements the other for the successful and cost effective removal of the visible emissions.
Any low boiling point VOC’s unlikely to fully condense at room temperature will not be removed with this abatement technique. In the event they are present and cause an odour problem to local residents then an adsorption technique is required to be included for the removal of these components – see description of this technique below.