(155c) Tracking Down Organic Acids and Sulfides from Petroleum Fluids: An Application of Real Molecule-Based Crude Assay Characterization and Segment-Based PC-SAFT

As global crudes being depleted, more interest and concern have been shown on heavy crudes with larger total acid number (TAN) and higher sulfur content. To process such crudes, aggressive corrosive attack should be expected at elevated temperature (300 - 350 °C)¹. Naphthenic acid (NAPA) corrosion is known to be a non-aqueous corrosion process, which may occur inside units including pipelines and distillation columns. Sulfides on the other hand, are also corrosive, but may offset NAPA’s corrosion to some extent by forming metal sulfide scales on the equipment surfaces. However, neither TAN nor total sulfur content correlates well with corrosivity of engineering alloys.² The present work provides specific molecular structure and composition of NAPA and sulfides by applying real molecule-based characterization to the crude assay. Furthermore, segment-based PC-SAFT as an equation of state is used to calculate vapor-liquid equilibrium of the petroleum, and simulate atmospheric distillation column to precisely track down the molecules of interest.

1. Bota, G. M.; Qu, D.; Nesic, S.; Wolf, H. A., Naphthenic Acid Corrosion of Mild Steel in the Presence of Sulfide Scales formed in Crude Oil Fractions at High Temperature. In NACE International: 2010.
2. Dettman, H. D.; Li, N.; Luo, J., Refinery Corrosion, Organic Acid Structure, and Athabasca Bitumen. In NACE International: 2009.