An electrostatic precipitator is a filtration device that removes fine particles, such as dust, smoke and liquid droplets, from an exhaust air stream using the force of an induced electrostatic charge minimally impeding the flow of gases through the unit.
In contrast to other techniques which apply energy directly to the flowing fluid medium, an ESP applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy in the form of electricity.
A wet electrostatic precipitator operates with saturated air streams. They are commonly used to remove liquid droplets such as sulphuric acid mist from industrial process air streams as well as for gases high in moisture content, contain combustible particulate, or having particles that are sticky in nature. The preferred and most modern type of wet ESP is a down-flow tubular design. This design allows the collected moisture and particulate to form a moving slurry that helps to keep the collection surfaces clean.
This ESP technique is ideal for the removal of high boiling point VOC’s such as machine or knitting oils, plastisol’s and web-offset printing inks in the printing, coating and textile industries. 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’ Coalescer (to coalesce the submicron droplets into larger droplets), a Tubular ‘wet’ Electrostatic Precipitator technique (designed to remove the liquid droplets from the air stream) and finally 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.