The Desalter: Crude Oil's First Stop

The main purpose of a desalter is to remove salts from crude oil before it enters the distillation column. Salts that remain in the crude will cause corrosion of refinery equipment and can lead to plugging and fouling.

How It Works

Crude oil is mixed with wash water, which draws the salts out of the oil. An electric field is then applied to help the water droplets coalesce and settle out. Typical wash water rates are 5 to 8% of crude throughput. Two-stage electrical desalters can achieve a crude salt concentration as low as 0.1 pounds per thousand barrels of crude. [1]

Desalter Effluent

The water removed from the crude is called desalter effluent. It is one type of process water that must be treated in the refinery wastewater system. Three contaminants typically found in desalter effluent are free hydrocarbons, sulfides, and ammonia. Multiple stages of treatment are used to reduce these contaminant levels before the water can be discharged or reused.

Works Cited

[1] Handbook of Petroleum Refining Processes