51313-02210-Extending the Life of FGD Inlet Ducts with UNS N06059

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Product Number: 51313-02210-SG

ISBN: 02210 2013 CP

Author: Larry Paul

Publication Date: 2013

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Flue Gas Desulfurization (FGD) systems are used to remove sulfur and other pollutants from the flue gas of coal fired power plants. These systems have been prone to variety of corrosion issues over the years. As a result the use of corrosion resistant materials is required throughout the entire system. One of the most demanding areas of the system is the inlet duct that feeds the raw un-scrubbed gases into the FGD system. This area is where hot flue gases first encounter the liquid scrubbing media (typically either a limestone or ammonia water slurry). Therefore this is the hottest wetted area of the FGD system and has always been an area where high corrosion rates have been seen on materials. Sulfuric and sulfurous acids form in this region that also can contain high levels of chlorides fluorides and other corrosive species (dependent on coal chemistry being burned in the boiler) this coupled with the high temperatures is responsible for the observed corrosive conditions.

Traditionally UNS N10276 has been used to line the ducting in this region to resist corrosion. While this has worked very well in most systems there are still some systems where the conditions are corrosive enough to limit the life of even this very corrosion resistant material. Laboratory and field testing has show that the UNS N06059 alloy can give improved life in this region of the FGD system. In actual field tests the life improvement factors of UNS N06059 are about 3 times that seen for UNS N10276. Laboratory and field data are shown in this paper that demonstrates the improvements for the UNS N06059.