Monday, March 23, 2009: 4:10 PM
C308 (Georgia World Congress Center)
Composite tubes have been typically used to construct the lower-furnace waterwalls of high-pressure (8,000 kPa or less) black liquor recovery boilers currently operated in North America . While these composite tubes have been very successful in resisting sulphidation corrosion, they have experienced unanticipated problems with the exterior layer, namely cracking, and, to a lesser extent, preferential corrosion of port opening tubes. In an attempt to evaluate the suitability of other alternative composite tube alloys, a lab-based testing program was conducted to evaluate the corrosion resistance of ferritic stainless steels (Types 430 and 446) and nickel-based alloys (Alloys 600 and 690) in simulated black liquor recovery boiler lower-furnace environments. An effort was made to utilize simulated environments that are believed to reproduce the key features of the various damage modes typically observed in the lower-furnace sections of high-pressure recovery boilers. This report documents the major findings of this effort.
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