Causes and solutions for recovery boiler primary air port composite tube cracking

A number of black liquor recovery boilers in North America have experienced severe, localized cracking in the coextruded 304L stainless steel/SA210 carbon steel tubes at or near the bottom of primary air ports. Some of these cracks have been found to advance into the carbon steel. Studies have shown that excessive temperature fluctuations on the surface of the tubes are common to all tubes that experience this cracking. This project has …