8/3/2019 Desalter Application and System

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Desalter application

It is all too easy to forget that the primary function of the desalting system is the removal of

chlorides, solids and other water-soluble compounds from crude oil. This presentation

demonstrates how a typical Desalter operates and shows what difficulties it contains.

Desalter system:

i. The function of the desalter is to remove suspended salt and water in the crude feed.ii. Salts are naturally present in oil when it is produced. When oil is distilled at a

refinery, it is heated to over 800*F, causing the salts to become very corrosive.

iii. To remove the salts, wash water is added to the crude in the incoming crude feed. Theoil and water are run through a mix valve which brings the salts in contact with the

water droplets.

iv. The emulsion created by the mix valve must then be quickly separated inside adesalter. Brine is discharged from the botton of the desalter.v. The oil discharged from the desalter must be less than 0.5% water. Otherwise, whenheated, it could over-pressurize the distillation column.

vi. To ensure oil dehydration, electrostatic grids are added to optimize coalescence.vii. However, if too much water reaches the grids, it will cause them to electrically

overload and shut down.

viii. To prevent this, emulsion breaking chemicals are added to the incoming crude toassist in oil/water separation.

ix. The water discharge from the desalter should be as clean as possible. However thewater quality is secondary to the quality of the oil. If necessary, the water quality will

be sacrificed to ensure the oil quality.x. The continuous change of oil/water concentrations makes it very difficult to optimize

the process. If salts reach a distillation column, corrosion damage could be extensive.