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Electrostatic Precipitator

Introduction to Precipitators:

An electrostatic precipitator is a large, industrial emission-control unit. It is designed to trap and

remove dust particles from the exhaust gas stream of an industrial process. Precipitators are used

in these industries:

Power/Electric

Cement

Chemicals

Metals

Paper

In many industrial plants, particulate matter created in the industrial process is carried as dust in

the hot exhaust gases. These dust-laden gases pass through an electrostatic precipitator that

collects most of the dust. Cleaned gas then passes out of the precipitator and through a stack to

the atmosphere. Precipitators typically collect 99.9% or more of the dust from the gas stream.

Basic Principles:

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

http://www.neundorfer.com/FileUploads/RichTextboxImages/Image/precipitator_b.jpg

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Theory:

Corona discharge:

In electricity , a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor that is electrically energized. The discharge will occur

when the strength ( potential gradient ) of the electric field around the conductor is high

enough to form a conductive region, but not high enough to cause electrical breakdown

or arcing to nearby objects. It is often seen as a bluish (or other color) glow in the air

adjacent to pointed metal conductors carrying high voltages. Spontaneous corona

discharges are undesirable where they waste power in high-voltage systems or where the

high chemical activity in a corona discharge creates objectionable or hazardous

compounds, such as ozone .

In Blast furnace gas cleaning system the fine particles are removed in electrostatic

precipitator. The gas containing fine particles are introduced from gas hole. A very high

potential difference is applied between solid plate and thin wire. The wire is negatively

charged while plate is positively charged. The gas particles acquire negative charge and

are attracted toward positive plate where they stick to it. The water is flown on these

plates so particles are removed in slurry form. Clean gas is send to stoves. Now gas hasless than 0.1 g/m3 of particles. It is 99 % pure now.

http://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Electrical_dischargehttp://en.wikipedia.org/wiki/Electrical_dischargehttp://en.wikipedia.org/wiki/Electrical_dischargehttp://en.wikipedia.org/wiki/Ionizationhttp://en.wikipedia.org/wiki/Ionizationhttp://en.wikipedia.org/wiki/Ionizationhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Conductor_(material)http://en.wikipedia.org/wiki/Conductor_(material)http://en.wikipedia.org/wiki/Conductor_(material)http://en.wikipedia.org/wiki/Potential_gradienthttp://en.wikipedia.org/wiki/Potential_gradienthttp://en.wikipedia.org/wiki/Potential_gradienthttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electrical_breakdownhttp://en.wikipedia.org/wiki/Electrical_breakdownhttp://en.wikipedia.org/wiki/Electrical_breakdownhttp://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Electrical_breakdownhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Potential_gradienthttp://en.wikipedia.org/wiki/Conductor_(material)http://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Ionizationhttp://en.wikipedia.org/wiki/Electrical_dischargehttp://en.wikipedia.org/wiki/Electricity

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figure 2