M. T. Z. Butt
University of the Punjab, Pakistan
Title: Failure analysis of a waste heat recovery boiler thermally coupled to ammonia oxidation Reactor
Biography
Biography: M. T. Z. Butt
Abstract
Waste heat recovery boiler (WHRB) is an essential component in the fertilizer industry. The repeated failure of waste heat recovery boiler (WHRB) coupled with ammonia oxidation reactor in a fertilizer plant is investigated in this study. Failure was observed in the boiler shell where thickness was 14mm constructed with 0.5Mo (SA 204 Grade A) steel. A failure was observed at the upper vessel section and working at temperature 500 - 600oC and internal pressure of 5.5kg/cm2. Air/ammonia mixture was being fed in the reactor coupled with WHRB and as a result of the exothermic reaction of ammonia oxidation the temperature was raised to 800oC in reactor. The temperature raised during NOx production was reduced to 280oC and pressure 5 kg/cm2 by the introduction of steam to recover the waste heat. The scale thickness on the inner side of the boiler shell was calculated to estimate Larson Miller Parameter (LMP) which in turn was used to predict the temperature of the shell at the time of failure. The decarburization and triple point cracks were observed in the microstructures present study. Metallography, mechanical and corrosion testing was performed on the samples. It was found that the failure occurred in the upper section of WHRB shell corresponded to prolong heating and overheating beyond the design limits