Air Heater Operation has Major impact on Efficiency - Hot Topic Hour January 22

John Guffre of Paragon was the featured speaker in the Hot Topic Webinar conducted on January 22. John described his recent trip to India where he found air heater leakage of 40 percent or more in boilers burning Indian coal. This coal has lots of highly abrasive ash.

John documented the dramatic increases in boiler output which can be obtained by using better seals in the air-preheater. The in-leakage increases the flow across the precipitator and reduces efficiency. He cited one case where the design 600 SCA was reduced to 450. With the new awareness of global warming there is even more reason to improve the efficiency and reduce the net CO₂/ MWh.

A discussion of air preheaters and their changing role was led by Bob McIlvaine. As we add FGD and mercury control we increase the penalties of in-leakage. Innovative ways should be considered to minimize the problem. Tubular air heaters are one option. One of the problems is real estate.  How do you make enough room? One suggestion is to use the CAIRtech concept.  A complete FGD system was designed to fit inside an 80 ft. diameter by 400 ft. high grain elevator. Could this concept be utilized to create a large vertical heat exchanger?

Another possibility is to take out the dust ahead of the air preheater. 3M has Nextel ceramic fibers. Madison Filter has their own version of a hot gas filter. In fact, in partnership with Haldor Topsoe they can also combine the filter with a NO_x reduction catalyst. Indigo has an agglomerator to make the hot side ESP work better. So there are ways to take out the dust ahead of the air preheater.  This would allow re-design to eliminate much of the leakage in a regenerative design and would allow use of other designs which are not suitable for high dust conditions.

Hitachi submitted a paper jointly prepared with Ameren revealing results with their Clean Energy Recuperator (CER). This is a finned tube gas cooler located upstream of the ESP to reduce the flue gas temperature and aid in SO₃ removal. Tests were run with a slip stream from the Ameren Duck Creek plant where a 2.79 percent sulfur coal is burned. Without the CER the SO₃ at the scrubber outlet was 11 ppm. With the CER the SO₃ was reduced to less than 1 ppm.

The CER improves the ability of activated carbon to capture mercury by eliminating the SO₃ interference. A venturi scrubber was placed ahead of the SO₂ scrubber. It was operated at low pH. It captured most of the mercury and therefore eliminates gypsum contamination.

The Paragon power points are in the FGD Decision Tree and can be viewed as follows:

John Guffre - Paragon

FGD Continuing Decision Process For: Products

Air Heater Leakage. Presented by John Guffre. Hot Topic Hour January 22, 2009.

http://www.mcilvainecompany.com/FGD_Decision_Tree/subscriber/Tree/DescriptionTextLinks/John Guffre - Paragon Airheater Technologies.pdf

The Hitachi paper has also been posted at

FGD Continuing Decision Process For: Products

Clean Energy Recuperator submitted by Hitachi and Ameren for Hot Topic Hour January 22, 2009.

Hitachi-AmerenPaperJanuary22,2009.pdf