HTH Recording

October 25, 2007

Air Preheaters and Heat Exchangers Play an Important Role in Efficiency and Air Quality - Hot Topic Hour on October 25

A very interactive two-hour session yesterday started with a presentation by Bob Eklund of the players in the air preheater business. Bob provided some background on the companies and the industry and some of the people. He singled out some of the experts among the participants e.g. Wayne Neuroth of Detroit Edision. Here is his summary of the companies and their products.

Air Preheater OEMS

Ø Alstom Air Preheater Co. USA

Wellsville, NY 14895

§ Lungström Air Preheaters

Ø Balcke-Dürr-Rothemühle

Wenden, Germany 57482

§ Lungström Air Preheaters

§ Rothemühle Air Preheaters

Ø Balcke-Dürr-Rothemühle USA

Clearwater, FL 33762

§ Lungström Air Preheaters

§ Rothemühle Air Preheaters

Ø Howden Group Ltd.

Renfro, UK

§ Lungström Air Preheaters

Ø Howden Buffalo Inc. USA

Camden, SC 29020

§ Lungström Air Preheaters

Air Preheater Suppliers

Ø Air Heater Seal Company

Waterford, OH 45786

§ Air heater seals

§ Louver dampers

§ Guillotine slidegates

Ø Air Preheater Technologies

Brunswick, ME 04011

§ Ljungström^® tech service

§ Rothemühle tech service

§ Outage inspections

§ National servicer

Ø Babcock & Wilcox

Barberton, OH 44203

§ Rothemühle APH support only

§ Replacement parts

§ Replacement element

§ Global supplier

Ø GIW Industries

Grovetown, GA 30813-2842

§ Cast iron seal shoes

§ Mill pulverizers

§ Direct/indirect sales

§ Global supplier

Ø Kingsbury, Inc.

Philadelphia, PA 19154

§ Patented thrust bearing

§ Alstom authorized servicer

Ø Mahoney, R.E. Company

Wrentham, MA 02093

§ Design, Engineering, and Technical Services

§ Basketed element

§ Replacement parts

§ Inspection/Evaluation Service

Ø Paragon Airheater Technologies, Inc.

Corona, CA 92883

§ High performance seals

§ Basketed element

§ Installation service

§ Inspection/evaluation

John Guffre of Paragon drew upon his many years of experience on both the operating and supplier side to talk about the advancements that Paragon has made. John described the DuraMax™ radial seal which is self adjusting and provides constant contact. Baskets are offered for both Lungström and Rothemühle air heaters. Coated baskets provide resistance to sulfuric acid.

Bill Ellison, Ellison Consultants, pointed out the drawbacks and remedy for low level heat recovery.

Air Preheaters: Potential Drawbacks Accompanying Their Essential Use in Low-Level Heat Recovery
- Brings about (by site-specific design) localized cooling of highly flyash-laden flue gas to below the sulfuric acid dewpoint temperature.
- Condensation of acid, apart from that beneficially sorbed by gas-borne flyash, wets heat transfer surfaces and causes progressive fly ash fouling of the air preheater, impacting unit reliability and performance.
- Is therefore a most awkward location at which to collect SO₃/H₂SO₄(v)
- With firing of medium/high sulfur U.S. bituminous coal, i.e. coal ash/sulfur ratio less than approximately eight, the desirable sorption of SO₃ by gas-borne flyash becomes a problem. With major SO₃ uptake, the fly ash will be rendered sticky, leading to highly intensified fly-ash fouling of the air preheater.

A Universal Remedy: Efficient Removal of SO₃/H₂SO₄ (v) Upstream of the Air Preheater

§ Mitigates all of the above causes of air preheater fouling ….as well as the potential impact of ammonia slip from high-dust SCR in its low-temperature reaction with SO₃/H₂SO₄ (v) to form adherent ammonium bisulfate sludge.

§ Eases constraints on SCR design/operation and catalyst formulation so far as amount of:

o Catalytic oxidation of SO₂ to SO₃/H₂SO₄ (v)

o Ammonia slip

§ Eases limits on ammonia slip concentration in design/operation of alternative SNCR means of secondary deNO_x

§ Supports reworking of heat recovery function of the economizer and air preheater, (and limiting the use of steam coil air preheater at low-load or in cold-weather operation), to lower exit flue gas temperature (to below 300°F) and enhance boiler thermal efficiency.

Both sides of the ocean were represented in the Balcke-Dürr presentation. Voelker Habe presented from Germany and was supported by Rainer Harteneck who was participating from Florida. He is spearheading sales of parts in the U.S. The company has a relatively new plant in Wuxi, China to supply the U.S. needs.

How about this as an example of globalization: You have a U.S. company (SPX) that owns a German subsidiary who manufactures in China and ships product to the U.S. On the other hand you have the proto-typical U.S. company, Kingsbury, as described by Neal Hulse. They have been making parts for regenerative air heaters forever and manufacture these parts in the U.S.

Jim Klausner of the University of Florida talked about heating up seawater using waste heat from a coal-fired power plant. You then blow air through hot seawater which is flowing downward through packing. The humidified air is then cooled. Distilled water is condensed from the air stream. The system is admittedly inefficient. However, if the heat source is otherwise wasted it becomes more energy efficient than reverse osmosis or conventional thermal desalination. The reason this subject was included in the heat exchanger Hot Topic Hour is the potential to extract more heat from the flue gas prior to the scrubber. Hitachi and Mitsubishi already do this in Japan. By using the combination of low pressure steam and the additional extracted flue gas heat the process would be more efficient.

There was a brief discussion of the Mitsubishi power points already in the FGD Decision Tree which show that placing a second heat exchanger prior to the precipitator improves fine particulate and SO₃ removal as much as using a wet precipitator after the scrubber. The problem is that you need enough particulate to absorb any sulfuric acid. This may work in Japan where low sulfur coal is burned. But can it be applied in the U.S.? What if lime or limestone is injected prior to the air heater in sufficient quantity? Couldn’t flue gas enter the precipitator at 195°F?

You can go directly to the power points in the FGD Decision Tree as follows.

Bob Eklund - Consultant

Start

►

Scrub

►

Physical

►

Multi-pollutant Requirements

►

Gases

►