Deterioration of economizer tube in utility boiler

Steam generation from intermediate petroleum products of different hydrocarbon processes ensures zero waste in oil and gas industries. The generated steam is again used for production of refinery final products. Although, zero waste increases refinery margin, there is downside associated with tube failure in utility boiler. Fire side corrosion occurred on economizer tube and failure was systematically analysed. A series of characterization techniques were conducted to find out the root cause of failure. Visual inspection, mechanical characterization, plant data collection, morphology investigation of scales using SEM, elemental analysis using EDX, and microstructural analysis were employed. Sulfur content was precisely determined on fire side scale deposits. Steam side feed water and steam products were analysed as well. Characterization of fire side deposits revealed iron oxide scales with severe sulfur concentration as well. The results revealed that failure was primarily owing to acid dew point corrosion and sulfur came from intermediate fuel oil (IFO). The failure mechanisms were discussed and good engineering practices were put forward to combat and mitigate acid dew point corrosion.