The acid content issue in oils
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The issue of acidity is often mentioned in relation to oils. What exactly is acidity, and what are its main components? What are the hazards, and how can they be eliminated?
[color=Red]It is mainly naphthenic acids and thiols. When the acid value is higher than 0.5 mgKOH/g, naphthenic acid corrosion becomes significantly more severe ； And when high-acid, high-sulfur crude oils are blended or processed alternately, the corrosion of the equipment becomes even more severe. Corrosion can be controlled by measures such as upgrading the material, adding an appropriate amount of alkali or switching to organic amines, incorporating high-temperature corrosion inhibitors, and controlling the process flow rate.
The acids present in refined petroleum products are mainly naphthenic acids in diesel; these can generally be removed through hydrogenation or alkaline treatment. The hazard of naphthenic acids lies in their corrosive effect on engines and their related systems.
Acidity (acid value) is a concept used to evaluate the content of organic acids in oils; it refers to the amount of KOH in mg required to neutralize the organic acids present in 1g or 1ml of oil. The unit is Xmg KOH/g or Xmg KOH/ml. Naphthenic acids make up the majority of these organic acids, so they are generally used as a representative. At present, naphthenic acids cannot be removed during the primary processing of crude oil; generally, high-temperature corrosion inhibitors are injected at the side streams or intermediate sections at temperatures of 250–350 degrees to reduce corrosion on the equipment, and it is also necessary to upgrade the material grade of such equipment. Naphthenic acids can be removed during the hydrogenation stage of secondary processing, improving the properties of the oil.