Electrostatic Precipitators: Clean Air Technology

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

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

3. Introduction • 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 • An electrostatic precipitator is a device which removes particles from a gas stream. • It consists of a theoretically simple four stage separation process.

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

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

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

7. Applications to ESP • Air Pollution Control • Coal-burning plants • Incinerators • Home air cleaners • Reducing Mercury Emissions

9. Fundamental Relations -Voltage applied to Electrode -> Corona Onset field Ec = 3.126 * 106 [dr + 0.0301(dr/rw)] -Integrate to get Voltage Vc = Ec*r*w*ln(d/rw)

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

11. There is a “laundry list” of competing technologies that alone or incombination 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 Each method has its advantages and disadvantages depending on applications andunder circumstances of use. Competing Technologies

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

13. Wet Scrubber

14. 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. • 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 • Main disadvantage is that this technology cannot be used in moist environments.

15. Fabric-filter Baghouse

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

17. Bibliography • Buonicore, A.J.; Davis, W. T. (2000).  Air Pollution Engineering Manual , VanNostrand Reinhold, New York, NY • Cooper, D. (September 2002).  Air pollution control particulate matter. Retrieved November 14, 2003, fromhttp://www.continuingeducation.com/engineers/airpollutionpm/ • Davidson, J.H. (2000).  Electrostatic precipitators.  Retrieved November 15,2003, fromhttp://www.me.umn.edu/courses/me5115/notes/ESPnotes.pdf • Green Force Engineers Pvt. ltd. (2002).  Controlling air pollution.  RetrievedNovember 14, 2003, from http://www.sugarudyog.com/pollution.htm • US Army. (2000).  Electrostatic precipitators.  Retrieved November 16, 2003,fromhttp://www.hnd.usace.army.mil/techinfo/UFC/UFC3-430-03/TM58151/chap8.pdf • U.S. Environmental Protection Agency (2003).  Air pollution control technologyfact sheet.  Retrieved November 16, 2003, fromhttp://www.epa.gov/ttn/catc/dir1/fventuri.pdf • U.S. Environmental Protection Agency (2003).  Air pollution control technologyfact sheet.  Retrieved November 16, 2003, fromhttp://www.epa.gov/ttn/catc/dir1/ff-pulse.pdf