Novel Development of Asset Integrity Management for Refinery Equipment: Theory, Application and Effect of Setting Critical Operational Tan and Sulfur Level for Distillation Units

Nowadays, refineries are continuously challenged by the low-grade crudes with increased concentration of sulfur and naphthenic acid. Operators need to know the limits of Total Acid Number (TAN) and sulfur content for their distillation units to avoid unexpected accelerated corrosion, which may lead to fires, explosions and toxic releases. New concepts and theory of critical TAN (Total Acid Number) and sulfur level was discussed, and the procedure of such MI project was reviewed by using a successful case. Critical operational TAN and sulfur level were determined on the basis of comprehensive evaluation of high temperature corrosion risk for every important part of distillation units. A corrosion model, which included main factors such as TAN / sulfur content, materials of construction, and temperature, has been developed for this assessment. Historical corrosion inspection data was used to validate the accuracy of the model. Experience of setting TAN and sulfur limits for 11 refineries over last 10 years was summarized. Comments and recommendations to improve this technology were made. The benefit of such MI project was widely acknowledged for the increased reliability of crude distillation units where it was implemented.