سال انتشار: ۱۳۹۱
محل انتشار: دومین همایش مشعل و کوره های صنعتی
تعداد صفحات: ۸
Hamed Abbasfard – Department of Chemical Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
Sattar Ghader – Department of Chemical Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
Hasan Hashemipour Rafsanjani – Department of Chemical Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
Amin Ghasemib – Department of Material Science Engineering, Azad university of Najafabad, Najafabad, Iran
Repeated failures have been observed in the outlet region of a few super heater tubes made of 1Cr–۰٫۵Mo steel integrated in waste heat boiler thermally coupled in an ammonia oxidation reactor. The tube hardness measurements were carried out on the selected super heater tubes including those of ruptured, unruptured and headers. The relatively high value of hardness, 260 HV, of ruptured part in comparison to other parts indicates that some phase transformation probably occurred for such a low-alloy 1Cr–۰٫۵Mo steel. A simple lumped dynamic mathematical model considering free convection and radiation was presented to show the temperature changes in case of shutdown of unit. It is found that the main cause of repeated failure of the super heater tubes were widespread sudden overheating and then rapid cooling of the super heater tubes due to sudden stoppage of operation (shutdown) and decreasing the thermal resistance of tubes. Shutdown of unit rooted in the blockage of steam flow inside connecting tubes which ended to tube overheating.