A Precipitator is a device that captures particulates from a gas stream.

In the simplest terms, a precipitator is a large box. The particulate laden gases are drawn into one side of the box using perforated plate and diffusers to evenly distribute the gas. Inside, high voltage electrodes impart a negative charge to the particles entrained in the gas. These negatively charged particles are then attracted to a grounded collecting surface, which is positively charged. The gas then leaves the box, up to 99.9% cleaner than when it entered.

Inside the box, the particles from the continuing flow of dust build up on the collection plates or tubes. At periodic intervals, the plates in a Dry ESP are rapped, and the tubes in a Wet ESP are flushed, causing the particles to fall into the collection hopper. In a Dry ESP the particles are usually removed from the hopper by a rotary screw arrangement. In a WET ESP the hoppers are designed to gravity drain or pump the flush water to designated treatment or disposal.

Wet electrostatic precipitator ( ESP ) particulate control system designs can be either up flow or down flow relative to where polluted air enters the ESP during the particulate control process. Turning vanes and perforated plate evenly distribute the gas flow inside of the wet electrostatic precipitator.

Assuming a down flow design:

The gas then enters the wet electrostatic precipitator ( ESP ) device’s round collection tubes, which are bundled, between two tube sheets in a honeycomb type arrangement. Above the collection tubes are two sets of spray headers. The first spray header continually mists the collection tubes with small water droplets, which are immediately charged and flow down the tube, in the direction of the gas flow. This continually wets the tubes to prevent sticky particulates from adhering to the tubes during the particulate control process. The second spray header is the flushing header, which periodically sprays a larger amount of water to flush the collected precipitate out of the collection tubes into the lower plenum, during the particulate control process.

In the middle of each ESP collection tube is a rigid pin corona-generating electrode. Each electrode suspends from an alignment rack, which is supported by insulators located out of the gas stream. A 65-80 KV transformer rectifier energizes the electrode rack with an automatic controller.
As the dust and aerosol particles enter the collection tubes, located inside of the wet electrostatic precipitator, they become charged from a bombardment of negatively charged electrons. The negatively charged particles adhere to the wetted collection tube and are periodically flushed into the electrostatic precipitator’s lower plenum.

The lower plenum is designed to demist the gas stream and drain all of the collected precipitate to the collection system, completing the particulate control process.

Electrostatic precipitation removes particles from the exhaust gas stream of an industrial process. Often the process involves combustion, but it can be any industrial process that would otherwise emit particles to the atmosphere. Six activities typically take place:

• Ionization - Charging of particles
• Migration - Transporting the charged particles to the collecting surfaces
• Collection - Precipitation of the charged particles onto the collecting surfaces
• Charge Dissipation - Neutralizing the charged particles on the collecting surfaces
• Particle Dislodging - Removing the particles from the collecting surface to the hopper
• Particle Removal - Conveying the particles from the hopper to a disposal point 
• The major precipitator components that accomplish these activities are as follows (with links to more in-depth information): (links to appropriate Product pages)
• Discharge Electrodes
• Power Components
• Precipitator Controls
• Rapping Systems
• Purge Air Systems
• Flue Gas Conditioning