An overview of naphthenic acid corrosion in a vacuum distillation plant

After 5 years processing about 6500 m3/day of reduced crude oil with an average total acid number of 1.2 mg KOH/g and total sulfur content of 0.8 wt%, a vacuum distillation plant had its operations interrupted to suffer maintenance and inspection. Following theoretical considerations, this work shows the inspection outcome and tries to stress the several morphologies resulting from the naphthenic acid attack as well as different types of action by which the naphthenic acid corrosion occurs in a vacuum distillation plant.

Different kinds of corrosion morphologies connected to the naphthenic acid attack. Region 1 is the IMPT random packing (pitting attack promoted by acid condensate), region 2 is the tray and bubble caps (NAC assisted by mechanical component), region 3 is the column wall flash zone (NAC assisted by impingement), region 4 is the support grid (NAC pitting attack), and region 5 is the transfer line (flow regime affects the fluid corrosivity).Figure optionsDownload as PowerPoint slideHighlights
► This work describes the naphthenic acid corrosion in a vacuum distillation plant.
► Different morphologies were produced by naphthenic attack on different conditions.
► Naphthenic corrosion assisted by mechanical component was identified.
► Naphthenic corrosion where the flow regime affects the fluid corrosivity occurred.