Everything you Wanted to Know About Electrostatic Precipitators

You can also reference terms with our Electrostatic Precipitator Glossary

What is an Electrostatic Precipitator?

An Electrostatic Precipitator or ESP is a device that removes particles from a gas stream.

Why would you do this?

The goal is to reduce pollutants emitted into the atmosphere to preserve the environment.

How efficient are ESPs?

Electrostatic precipitators typically can remove up to and even more than 99% of the particles in exhaust.

What’s the main advantages of an ESP say vs. a bag house filter – Or when would you choose an ESP over a baghouse?

ESPs work without having to force the air through a filter. So fan energy is minimized. Filters require periodic replacement. Also an ESP can work with higher heat applications that a bag house fabric would not be able to withstand. ESPs are more expensive from an initial capital cost point of view.

What is their principal of operation – ie how do they work?

When the gas stream laden with particulate such as dust or ash passes through the area where the very high high voltage electrodes are housed, the high voltage electrodes transfer electrons to the particulate. In other words, the electrodes transfer a negative electrical charge to the particles or mist being carried within the airstream.

As the particles in the gas stream continue downstream towards the stack exit, they next pass through the area where positively charged plates reside. In this area the particles are attracted by these positively charged plates and the particulate or mist end up sticking to the metallic plates.

Do you need to clean the plates?

Yes. If not periodically cleaned off the particulate would build an insulating layer and stop the accumulation of particulate. The positive plates have a rapper mechanism that shakes off the accumulate material that is more like a cake at this point.

Does the rapper mechanism resemble 50 Cent with like a hammer?

No.

How much of charge do you need to have for an ESP.

80,000 Volts is typical.

Wouldn’t that consume a lot of electrical energy?

No, not really. Because Power = Volts x Amps, so although the voltage is very high, the charge or amperage is very low. So an ESP is very energy efficient and operating costs work out to a few dollars per hour.

What are the main types of ESPs?

There are really two types wet and dry ESPs.

When would you use a dry ESP?

Dry precipitators are used whenever particles in the airstream are dry such as ash or cement dust.

When would you use a wet ESP?

Wet precipitators are used to remove wet particulate such as resins or paint or acids.

Is the construction different?

Yes. Wet precipitators have to be made out of corrosion resistant material such as stainless steel. So they generally have a higher first cost. Wet ESP do not have a rapping system for cleaning. Instead it has a flushing system on the top.

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