Electrostatic Precipitators: Clean Air Technology Group 5: Brian Cholvin Diane Lomeli Michael Obradovitch Magaly Vazquez

Overview Introduction Introduction Separation Process Separation Process Classification of Electrostatic Precipitators Classification of Electrostatic Precipitators Applications Applications Governing Equations Governing Equations Competing Technology Competing Technology Conclusion Conclusion

Introduction Electrostatic Precipitation (ESP) has a wide variety of industrial applications in Air Pollution Prevention and Control. Electrostatic Precipitation (ESP) has a wide variety of industrial applications in Air Pollution Prevention and Control. Applications of the principle can be found in electronic air cleaners Applications of the principle can be found in electronic air cleaners An electrostatic precipitator is a device which removes particles from a gas stream. An electrostatic precipitator is a device which removes particles from a gas stream. It consists of a theoretically simple four stage separation process. It consists of a theoretically simple four stage separation process.

Separation Process It accomplishes particle separation by the use of an electric field which It accomplishes particle separation by the use of an electric field which Ionization Ionization imparts a positive or negative charge to the particleimparts a positive or negative charge to the particle Acceleration and Collection of Particles Acceleration and Collection of Particles attracts the particle to an oppositely charged plate or tubeattracts the particle to an oppositely charged plate or tube

Separation Process Continue Particle Stripping (“Rapping”) Particle Stripping (“Rapping”) Removes the particle by vibrating or rapping the collection surfaceRemoves the particle by vibrating or rapping the collection surface Particulate Collection and Disposal Particulate Collection and Disposal Moved from the collection surface to a hopper.Moved from the collection surface to a hopper.

General Classification of Electrostatic Precipitators Cold-Sided Precipitators Cold-Sided Precipitators Cooler temps for low resistivity particles Hot-Sided Precipitators Hot-Sided Precipitators Higher temps for higher resistivity Wet Precipitators Wet Precipitators H2O cleans collection plates results in higher efficiency

Applications to ESP Air Pollution Control Air Pollution Control Coal-burning plantsCoal-burning plants IncineratorsIncinerators Home air cleanersHome air cleaners Reducing Mercury EmissionsReducing Mercury Emissions

Fundamental Relations -Voltage applied to Electrode -> Corona Onset field Ec = * 106 [dr (dr/rw)] -Integrate to get Voltage Vc = Ec*r*w*ln(d/rw)

Particle Charging Total Charge is Diffusion plus Field Charge Total Charge is Diffusion plus Field Charge Diffusion charging from Kinetic EnergyDiffusion charging from Kinetic Energy qd(t) = rkT/e ln(1 + τ) qd(t) = rkT/e ln(1 + τ) Field charge from electric field lines.Field charge from electric field lines. qf(t) = qsθ/(θ + τ’) qf(t) = qsθ/(θ + τ’) qtot(t) = qd(t) + qf(t)

Competing Technologies There is a “laundry list” of competing technologies that alone or in combination with different technologies can lower pollutant levels. There is a “laundry list” of competing technologies that alone or in combination with different technologies can lower pollutant levels. Some of these clean air technologies include: cyclones, momentum separators, Venturi scrubbers, catalytic incinerators, fabric filters and zeolites Some of these clean air technologies include: cyclones, momentum separators, Venturi scrubbers, catalytic incinerators, fabric filters and zeolites Each method has its advantages and disadvantages depending on applications and under circumstances of use. Each method has its advantages and disadvantages depending on applications and under circumstances of use.

Venturi Scrubbers Venturi scrubbers are part of a group of air pollution prevention devices commonly referred to as “wet scrubbers” Venturi scrubbers are part of a group of air pollution prevention devices commonly referred to as “wet scrubbers” These devices remove air pollutants via internal and diffusional interception These devices remove air pollutants via internal and diffusional interception Venturi scrubbers are generally used when it is necessary to obtain high collection efficiencies for “fine particulate” matter Venturi scrubbers are generally used when it is necessary to obtain high collection efficiencies for “fine particulate” matter Expensive to operate. Expensive to operate.

Wet Scrubber

Fabric Filtration Fabric filters are control devices that capture and dispose of particulate matter, they can be used in almost any process where dust is generated and stored to a central location. Fabric filters are control devices that capture and dispose of particulate matter, they can be used in almost any process where dust is generated and stored to a central location. They are most commonly used for applications which have dense pollutants such as utility boilers, metal processing and mineral products. They are most commonly used for applications which have dense pollutants such as utility boilers, metal processing and mineral products. "Baghouse" performance is dependent on many variables such as cleaning frequency, methods and particulate characteristics "Baghouse" performance is dependent on many variables such as cleaning frequency, methods and particulate characteristics Main disadvantage is that this technology cannot be used in moist environments. Main disadvantage is that this technology cannot be used in moist environments.

Fabric-filter Baghouse

Conclusion There is a wide market for clean air technology products There is a wide market for clean air technology products Electrostatic precipitators are the most readily accepted and established clean air technology Electrostatic precipitators are the most readily accepted and established clean air technology For Governmental ApplicationsFor Governmental Applications Industrial ApplicationsIndustrial Applications Commercial ApplicationsCommercial Applications

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