Failure of Alloy 20 nozzles used for spraying sulfuric acid in an incineration furnace

• Alloy 20 nozzles were used for spraying 98.5% sulfuric acid in an incineration furnace at approximately 1453 K.
• The nozzles failed within 7 days of service by erosion corrosion instead of high temperature degradation.
• Five-step mechanisms were proposed to explain the failure of nozzles.
• SiC or Si3N4 was recommended as materials of fabrication or coating for nozzles.

Alloy 20 nozzles, which were used for spraying sulfuric acid into an incineration furnace of a petrochemical plant, failed prematurely after 7 days of service at approximately 1453 K. The material for manufacturing the nozzles complied with Alloy 20 (ASTM B473 UNS N08020) specification. Investigation by optical microscopy, scanning electron microscopy and metallographic analysis showed that the nozzles failed by erosion corrosion action of concentrated sulfuric acid. Five-step mechanisms of erosion corrosion damage were proposed. Using SiC or Si3N4 as materials for coating or fabricating the nozzle part could potentially alleviate erosion corrosion problem.