August 2011

“Improving Electrostatic Precipitator Performance (Wet and Dry)” is “Hot Topic Hour” on Aug. 25, 2011

The Cross-State Air Pollution Rule that replaces and strengthens the 2005 Clean Air Interstate Rule (CAIR), (SO₂ and NO_x), Regional Haze (SO₂, NO_x, PM), NAAQS Revisions (PM_2.5, Ozone, SO₂, NO₂), the revisions to NSPS coming soon and the Utility MACT or Air Toxics Rule to be finalized in November (Hg, Acid Gases, Non-Hg Metallic HAPs, and Organic HAPs) will all act to drive total particulate emissions limits for coal-fired power plants to near detection levels.

Electrostatic precipitators (ESPs) have been proven to be effective and reliable particulate control devices for coal-fired power plants and generally capture 99.5 percent of the particles from the flue gas in terms of mass volume. However, this will probably not be adequate to meet the future regulations for PM_2.5. In addition, many of the ESPs in use today are old and undersized for the task at hand or are operating with a different fuel (low sulfur) and load than they were originally designed for. Other than general deterioration of the precipitator, several design factors can lead to less-than-desired performance. These can include small size and consequent short treatment time and low specific collection area, discharge electrode configuration, collecting plate spacing, non-uniform flow and inadequate electrical control systems.  Fortunately there is technology available that can be employed to increase the efficiency of an existing ESP short of complete replacement.

The following speakers will describe the various options for improving the performance of existing precipitators, new technologies that have been or are being developed to improve the performance of older and new ESPs, the performance of newly upgraded or retrofitted units relative to achieving the expected PM_2.5 emission limits, the advantages or disadvantages of the options for specific plant configurations and operating conditions and factors to consider when deciding whether to upgrade or replace an existing ESP.

Bruce Scherer, EPRI Project Manager for Program 76, Opacity and Particulate Control, will discuss the ongoing research effort to provide quantifiable and reliable performance enhancements to existing electrostatic precipitators to meet the upcoming, stringent EGU MACT particulate material regulations. Included will be flow control innovations, power supply and hardware upgrade assessments, research on high resistivity and biomass blend ash collection enhancement and upgrades to ESPM, EPRI's precipitator performance model.

Rob Kimberl, Vice-president for Operations & Technology at Clyde Bergemann EEC, will discuss improving the performance of existing precipitators. Whether it is to achieve existing standards or trying to achieve new standards, an existing precipitator can be part of your particulate control strategy.  Improving electrostatic precipitator performance can be as simple as performing routine maintenance to as complicated as adding a new chamber.  These concepts will be presented, along with their relative impacts on performance.

Paul Leanza, Senior Technical Engineer for Post Combustion Control Equipment at Pollution Control Services, Inc, will focus on evaluating existing precipitator’s ability to meet the proposed Utility MACT regulations.  The majority of existing ESPs are not operating under their original design basis.  Many existing ESPs have not been upgraded with modern operating philosophies or equipment.  Taking a holistic approach in evaluating the precipitator in its current operating parameters permit a viable plan forward as the operating parameters have been modified as additional post combustion control equipment like SO₃, NO_x, and Hg control have been incorporated over the last few years.

Randy Cook, Manager of Business Development at Alstom Power, Inc, will discuss options for improving existing ESPs to meet the coming emission limits. Contrary to the popular belief, many of the existing ESPs can be rebuilt to meet the stringent emission requirements of pending regulations. A combination of multiple technologies for mechanical and controls upgrade will have to be used in most installations depending on fuel, existing ESP sizing and configuration. Changing electrode geometry, installation of high frequency power supplies, optimized rapping, advanced controllers with opacity optimization, power down rapping, off flow rapping can achieve significant PM emission reduction without adding plate area or replacing the ESP by a FF. If upgrade of ESP alone cannot meet the emission requirement, it may be cost effective to install a downstream polishing FF.