Desalting – continued

The figure provided here illustrates a schematic diagram for an electrostatic desalter.

Notice the feed (unrefined crude) being fed to the system on the left hand side. The crude is heated and then mixed with process water, as shown.

Electrical desalting is the application of high-voltage electrostatic charge to concentrate the suspended water globules in the bottom of the settling tank.

Sometimes surfactants are also added, but only when the crude has a large amount of suspended solids. Both methods of desalting are continuous. A third and less-common process involves filtering heated crude using special filtering media.

In these processes, the feedstock crude oil is heated to between 150 and 350 deg F (65 – 175 deg C) to reduce its viscosity and surface tension for easier mixing and separation of the water.