A NEW APPROACH TO PREVENT CORROSION OF THE REACTOR EFFLUENT SYSTEM IN HDS UNITS

摘要

In recent years, unexpected incidents of corrosion caused by chlorides have increased presumably because many refiners diversify the crude oils to be processed. The problems associated with chlorides are not limited to a crude distillation unit. Chlorides can be carried over downstream by being entrained in feed stock for each unit. In the case of a hydroprocessing unit, the chloride corrosion is usually caused by deposition of ammonium chloride (NH_4Cl) especially at the reactor effluent air cooler (REAC) and associated piping. In our new gas oil deep hydrodesulfurization (HDS) unit also, serious corrosion under NH_4Cl deposit was experienced. The inlet piping and tubes of the REAC were severely corroded despite the unit was designed based on conventionally applied designing criteria on fluid velocity, amount of aqueous water remained at the injection point and so on. In the present paper, successful mitigation using the Computational Fluid Dynamics (CFD) to optimize the water injection procedure where NH_4Cl deposition is inevitable inside the tube and pipe shall be discussed.