(125e) Naphthenic Acids and Sulfur Compounds - Corrosive Interactions at High Temperature

One of the constant challenges confronting the oil refining industry is naphthenic acid (NAP) corrosion that became very important as refineries began processing increased volumes of low quality oils with high NAP content. Low quality oils processed in refineries at elevated temperatures (300 - 350°C) when NAP acids are present cause corrosive attack, damaging the inner walls of distillation towers and their connecting transfer lines. NAP acid corrosion can be enhanced or mitigated by some sulfur compounds that may be inherently present in crude oil fractions. These sulfur compounds react with the metal exposed to the oil stream and generate iron sulfide deposits, as thin scale on the inner surfaces. The iron sulfide scale formed on metal surfaces can offer some protection against the NAP corrosive attack but this protection is limited under the constant NAP acid attack and high velocity flow conditions encountered in the transfer lines. The research being presented focused on evaluating the properties and structure of scales formed on steel samples in crude oil fractions of different sulfur and acidic content and exposed to NAP acid attack under high temperature and high velocity conditions. The structure and morphology of the scales formed in crude fractions were investigated using scanning electron microscopy coupled with energy dispersive X-ray diffraction (SEM/EDS).