Safe Processing of Naphthenic Acid Opportunity Crudes Using Chemical Inhibition and Online Monitoring

Abstract Continuing economic pressures on the refining industry are forcing more refiners to evaluate the possibilities of processing lower priced, opportunity crudes to improve margins. These crudes are often considerably more corrosive than more expensive crudes, containing potentially higher levels of naphthenic acid. The processing of naphthenic acid containing crudes introduces significant challenges to the refiner, with the risk of high temperature naphthenic acid corrosion being one of the primary concerns. If refiners are to take full advantage of these discounted opportunity crudes, these challenges need to be addressed to avoid margin attrition caused by decreased equipment reliability and run length. Refiners must assess, monitor and mitigate naphthenic acid corrosion and other processing impacts associated with these crudes. One of the most critical aspects of this risk management methodology is the implementation of a corrosion monitoring program robust enough to ensure corrosion rates are not excessive when the Total Acid Number (TAN) levels are increased. Permanently mounted ultrasonic thickness measuring sensors that can operate at the high temperatures where naphthenic acid attack occurs provide the refiner with a cost effective, reliable means to install a rigorous corrosion monitoring program that provides comprehensive coverage of the areas identified to be at elevated risk of naphthenic acid corrosion. With a rigorous monitoring program in place, the applied corrosion control strategies can be optimised to ensure corrosion rates are not excessive and asset reliability and integrity is not compromised. This paper provides an overview of the risk assessment methodology and how it is applied to assess and monitor the risks in conjunction with a rigorous corrosion monitoring program comprising of multiple ultrasonic sensor placements. Various case studies are presented.