Abstract
Corrosion problems related to crude refining became a dominant concern as crude oil refining expanded to serve global energy demands with concomitant economic benefits in the petroleum industry, and more so with the availability of ‘opportunity crudes'. Reducing oil production costs have continuously forced refineries to look for so-called “opportunity” or “alternate” crudes, which are usually lower quality, higher corrosivity crude oils with higher levels of naphthenic acids and sulfur compounds. Processing of these high acid, high sulfur crudes has engendered significant corrosion concerns in hot oil distillation units and associated piping systems.
Mitigating ‘opportunity crude' corrosivity involves several strategies including improvement of the refining process of blending crudes, injection of inhibitors, de-acidification, utilization of materials with higher corrosion resistance, control of flow velocity and associated wall shear stress produced by the flow media, and finally optimization of in-service inspection and monitoring in oil refineries. This paper details a review, based on the experience of the authors in developing extensive naphthenic acid corrosivity data from a comprehensive Joint Industry Program (JIP), which investigates the influence of crude oil chemistry on naphthenic acid and sulfidic corrosion. Contributions of reactive sulfur chemistry to protectiveness and FeS scale formation, and the ability to resist naphthenic acid corrosion utilizing beneficial sulfur speciation as well as acid molecular weight, molecular structure, molecular boiling point as well as operational parameters of temperature, shear stress, and alloy metallurgy are addressed.
