Corrosion Damage And Protection Research Of Heat Exchanger In Desulfurization Unit

This paper is based on the corrosion and leakage problem of the lean-rich amine liquid heat exchanger tube bundle of a petrochemical refinery desulfurization unit,and mainly studies the corrosion mechanism of the tube bundle and the factors affecting the tube bundle corrosion.Due to the characteristics of high temperature and high flow rate of the medium,the tube bundle has corroded leakage and scouring leakage.The tube bundle of the lean-rich amine liquid heat exchanger of a petrochemical refinery desulfurization plant suffered serious corrosion and perforation,which seriously affected the normal and safe operation of the desulfurization plant.In this study,the corrosion rate of steel of different materials under working conditions was analyzed by on-site coupons,and then the polarization behavior of steel 20 in amine solution was studied by electrochemical testing method.The results showed that steel in amine solution It is very stable,and it is determined by comparison that the corrosion may be caused by hydrogen sulfide in the rich amine solution.In order to determine the corrosion mechanism of the tube bundle,sampling the on-site corroded tube bundle,with the help of scanning electron microscope（SEM）,energy spectrum analysis（EDS）and X-ray diffraction analysis（XRD）,it was determined that the corrosion of the tube bundle was mainly due to the high temperature release of the rich amine solution in the tube.Caused by absorbed hydrogen sulfide,hydrogen penetration into the steel is the main cause of sulfide stress cracking,hydrogen-induced cracking and hydrogen bubbling on the surface of the heat exchange tube.By using FLUENT software to simulate the flow and heat transfer of the shell side fluid,it can be found that fluids with different flow rates make the temperature in the shell side change,which in turn affects the temperature change in the tube.The high temperature rise makes the rich amine liquid release hydrogen sulfide.The main cause of corrosion.Therefore,the higher the flow rate,the more obvious the temperature rise in the pipe and the more serious the corrosion.High-velocity fluid has an erosion effect on the unstable protective film formed on the surface of the tube bundle,accelerates the decomposition of the protective film,and promotes corrosion.By simulating the thermal flow field of fluids with different flow rates at the baffle,tube sheet and tube bundle at different positions,it can be found that the temperature rise in the tube from the shell side entrance to the tube sheet is obvious,and the tube bundle is prone to corrosion and leakage in this range.By simulating the erosion of heat exchanger tube bundle,it can be found that the erosion of tube bundle is mainly concentrated near the inlet of vertical shell side.At the entrance of shell side,the velocity of fluid is larger than that of deviation from the entrance of shell side,and the kinetic energy of particles is larger at high velocity.The more serious the erosion of tube bundle is.With the increase of the mass flow rate,the surface area of the tube bundle is larger and larger,but the maximum erosion increases first and then decreases.This is due to the larger the mass flow rate,the more particles the fluid carries and the more serious the erosion per unit area.