Abstract
Highly concentrated NH4HS causes significant corrosion. In high pressure plants such as hydrodesulfurization units operated under NH4HS environments, leakage caused by corrosion could result in catastrophic disaster. Therefore, in the design phase, corrosion prevention techniques should be considered. In this study, based on the severe NH4HS corrosion observed selectively in the vapor phase inside air cooled heat exchanger tubes, the NH4HS concentrating model was developed to discern the difference in NH4HS concentration between the vapor phase and the liquid phase. We elucidated that NH4HS concentration in the condensed area in the vapor phase can be much higher than the liquid phase due to the difference of the heat transfer coefficient. This result quantitatively demonstrated the cause of corrosion observed in the air cooled heat exchanger tubes. In addition, this study indicated that the design of the air cooled heat exchanger tube where NH4HS corrosion shall be concerned should consider a flow regime, air temperature or predicted NH4HS concentration in the condensed area in the vapor phase.
