7-02-09

Particulate Choices for Low Sulfur Coal include both ESPs and Bagfilters say Presenters at Hot Topic Hour Yesterday

In the Hot Topic double seminar yesterday cases were made for both ESPs and bagfilters as ways to meet stringent PM_2.5 requirements when burning low sulfur coal.

Mick Chambers of Southern Environmental stated that recent performance test results from ESP retrofits and upgrades indicate that these devices, using modern equipment and technology, can provide very low particulate emissions at a relatively modest cost for PRB coal applications. Several units, with and without SO₃ conditioning, have produced emissions results comparable to fabric filters. These results, together with several built-in advantages of ESPs, now place this technology squarely in the mix when considering particulate control options for PRB-fired boilers. At a cost of less than 50 percent of a new unit, new internals can be inserted and efficiencies greatly improved. Duck Creek 3 is one such example.

Chet Moon of Toray discussed four fiber combinations. Toray PPS TORCON^® is the most suitable fiber to meet most of the filtration needs of coal-fired boilers. Due to the potential use of bromine compounds for mercury oxidation Tefaire may be a logical choice because of its chemical resistance. Toray is actively seeking new developments to improve filtration performance.

Tom Anderson of TDC Filter (MFRI) pointed out the regulatory challenges. PM_2.5 rules are likely to be stringent in California and many other states. Therefore efficient media will be a necessity. High efficiency ePTFE membranes show significant reduction in average residual pressure drop vs. high low ePTFE membranes. Stack Efficiencies of 99.9983% have been achieved with media evaluated under the EPA/ETV’s testing protocol. Minimizing use of compressed air results in significant energy savings. The right media selection can reduce the amount of air required for cleaning the bags.

Anne Minga of Kuttner warned of the significant impact of condensibles on total particulate emission. Furthermore different test methods are not showing the same quantities. Mercury is being efficiently removed in a foundry with a baghouse and sodium bicarbonate injection.

Greg Carleton of Pollution Control Services explained that a holistic approach is necessary. He predicted that all coal-fired power plants will have particulate, NO_x and SO₂ removal systems, so it is necessary to address all the needs simultaneously. A plan should also address the likelihood of CO₂ reduction as well. Well operated baghouses or precipitators should meet stringent PM_2.5 requirements. Precipitator excursions are minimized by modern controls and internal design.

Sam Mitra of Beltran described the wet ESPs furnished to CESC in India. Multi–cyclones reduce the flyash from 7000 mg/Nm³ to 1500 mg/NM³ at the wet precipitator inlet. More than 99 percent removal is achieved in the WESP. A discussion relative to the application of this technology for small U.S. coal plants ensued. An SO₂ scrubber and vertical WESP can be combined in one tower. This may be an alternative to the spray drier/baghouse. Sam indicated that a major U.S. utility will be piloting a WESP following a dry ESP.

John Darrow of W.L. Gore championed the advantages of surface filtration as opposed to depth filtration. Membranes with surface filtration have advantages. CP Crane, Big Stone, Tolk, Nixon, Drake, Arapaho, AB Brown, Culley, Springerville, Antelope Valley, Wateree, and Pawnee have already opted for membranes and other coal-fired power plants are considering this option. It is a misconception that membranes will not hold the carbon cake necessary for mercury removal. As long as there is air flow the cake will be retained.

The bios, abstracts and photos can be viewed as follows: July 2, 2009 BIOS, ABSTRACTS, PHOTOS.htm

The individual slides are in the Particulate Decision Tree and can be viewed as follows:

Mick Chambers – Southern Environmental

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