August 2011

“Filter Media Selection for Dry FGD and Particulate Control” is Hot Topic Hour on August 11, 2011

The Cross-State Air Pollution Rule, that replaces and strengthens the 2005 Clean Air Interstate Rule (CAIR), (SO₂ and NO_x); the Regional Haze Rule (SO₂, NO_x, PM); NAAQS Revisions (PM_2.5, Ozone, SO₂, NO₂); the revisions to New Source Performance Standards (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 SO₂/SO₃ and total particulate emissions limits for coal-fired power plants to near detection levels. Many power plants already have wet or dry FGDs in place to meet the current SO₂ and particulate limits and many others will be installed over the next few years to meet the future limits. Although many believe that wet FGD is the best choice considering the particulate control also required, plant engineers will be looking closely at dry FGD because of water use and disposal issues. Power plants that currently have dry FGD systems will likely need to improve their particulate collection and power plants considering dry FGD will also need to consider particulate emissions at the same time.  Addition of a fabric filter after the FGD will be one of the more important technologies utilized by utilities to achieve the reductions in fine particulate emissions soon to be mandated.

The following speakers will discuss their current experience with particulate control at power plants utilizing dry FGDs with and without fabric filters and address the advantages or disadvantages of the various fabric filter options available to reduce fine particulate emissions to the soon to be mandated limits for specific applications and site conditions. They will also address capital and operating costs and factors to consider when selecting a particular control strategy.

Tom Anderson, Vice President for Pleated Products at Midwesco/TDC, will discuss matching the appropriate element/media to specific applications and developing pleated bag applications/conversions as a solution to collector operation problems.

Zachary Arndt, Environmental Associate with Sargent & Lundy LLC, will discuss the Sargent & Lundy approach to selecting the appropriate baghouse fabric filter bags when high temperatures, oxygen concentrations, and chemical agents are present in the inlet gas flow. These heightened factors need to be properly addressed to ensure that bag life warranties and emission guarantees are met for each and every client.

Terry Wanta, Pristyne® Filter Media Business Leader at W. L. Gore & Associates, Inc., will discuss the impact a dry injection system or dry scrubber can have on the filter media, the various filter material choices available, and how ePTFE membrane media may improve operations while meeting the required regulatory limits.

Dry flue gas scrubbers or dry injection systems are options to control acid gases (SO_x and HCl). Adding a dry scrubber upstream of an existing baghouse will change the operating conditions. In some cases, the existing filter media will provide acceptable performance under these new conditions; in other cases the baghouse performance will suffer. ePTFE membrane bags are capable of handling a wide range of gas and dust conditions. The attributes of membrane filtration can provide plant personnel with more flexibility in overall operations.

G. Keith Ogilvie, Jr. of Hamon Research-Cottrell.