Analysis of the naphthenic acids corrosion in a vacuum distillation tower of the Brazilian national oil refinery system

Naphthenic acids are a mixture of carboxylic acids that are present in the composition of several types of petroleum. Such acids cause naphthenic corrosion in oil processing and refining units, which is commonplace in distillation units and particularly in vacuum distillation towers. This work analyzed the inspection process carried out during a scheduled maintenance shutdown in 2019 in a vacuum distillation tower of a Brazilian oil refinery, which processes about 6,500 cubic meters of crude oil per day. The formation process, the most affected materials, the most relevant operational parameters, the ways to mitigate this type of damage and the images obtained from the corrosive process by naphthenic acids in the different regions or sections of the vacuum distillation tower were shown and discussed. At the bottom of the tower, the synergistic effect of sulfur corrosion, aggravated by the high temperature and the presence of naphthenic acids, was also identified. Thus, it is expected that this work will contribute to the debate of this corrosive mechanism extremely active in the oil refining industry.