Crude desalting in the oil & gas industry

The purpose of desalting is to remove undesirable impurities in the crude oil: these are salts, water and base sediments, which can all cause problems later in the refining process. Water is present in the oil, in an emulsion mixture: salts such as calcium, sodium and magnesium chlorides are dissolved in the water. At the higher temperatures used in the refinery these could later create hydrochloric acid, which leads to corrosion in the plant. Deposits of the sediments can foul heat exchangers and cause plugging. Also metals like sodium and arsenic can poison the catalysts used in later stages.

The crude desalting process uses a demulsifying agent, which is a combination of chemicals injected into the oil to break and separate the emulsion, and there is a fresh water wash to extract the impurities. This is typically repeated to ensure dilution of the impurity concentrations. The desalter operates at around 150oC, and crude oil desalting instrumentation such as interface level measurement systems control the separation process. The wash water is discharged to a wastewater treatment plant.

KROHNE supplies flowmeters to measure the flow of crude oil and wash water both to and from the desalter. Also, TDR radar level measurement equipment to control the oil/water interface in the separators used in the desalting process is available from KROHNE.