Diagnosis of High Temperature Cycling Associated with Primary Air Port Cracking inKraft Recovery Boilers

摘要

Initiation and growth of cracks in composite tubes that form primary air port openings of kraft recovery boilers have been linked to the magnitude and frequency of temperature cycling on the surface of the tubes. A specialized in situ videocamera system was used to document the fireside conditions in three North American recovery boilers that have experienced composite tube cracking. The recorded video and thermocouple data, where available, were subsequently analyzed to determine the factors contributing to the problematic temperature cycling. Sets of fireside conditions have been associated with low temperature and high temperature cycling. Differences between the two have implicated a combination of increased local combustion, and indirectly increased oxidation of sulphide, in the creation of high temperature cycling.