A systematic study was conducted to examine the cause of severe cracking of SS304L/SA210 composite waterwalltubes at primary air ports in the recovery boiler at the Irving Pulp & Paper - Saint John mill. The results show thatthe severity of the cracking problem was strongly related to the frequency and the magnitude of tube temperatureexcursions at the air ports. The cracking problem has been significantly reduced by operating the boiler at a lowerblack liquor solids content and at a higher primary air flow. These operating conditions appear to keep the char bedaway from the air ports and help reduce tube temperature excursions.
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