desalters

Desalters, or desalting units, are refinery equipment designed to remove dissolved inorganic salts and entrained water from crude oil before it enters the downstream processing train. By reducing salt content and free water, desalters help prevent corrosion, fouling, and catalyst poisoning in heat exchangers, boilers, and catalytic units.

Most desalters operate by blending incoming crude with wash water and a chemical demulsifier, heating the mixture, and then passing it through an electrostatic separation stage. An electric field charges and coalesces water droplets, promoting phase separation in a settler. The water or brine phase settles at the bottom and is drained, while the desalted crude exits from the top for further processing. Wash water is typically circulated from refinery water sources or produced water. The dosage of demulsifier and the amount of wash water are adjusted to achieve the desired salt removal and low water content in the oil.

Desalting performance depends on crude quality, temperature, emulsion stability, and the effectiveness of the electric field and chemical treatment. Typical outcomes are significant reductions in dissolved salts and free water, with salt content in the treated crude reduced to tens of parts per million and water content minimized to a fraction of a percent by volume. Desalters can be configured as single-stage or multi-stage units to handle different crudes and salinities.

Variations include preheating, multi-stage configurations, and different separator arrangements. Maintenance focuses on ensuring proper electrical field operation, inspecting electrodes, monitoring wash-water quality, and preventing emulsion buildup. The desalting process is a standard early step in most refinery crude streams, essential for protecting downstream equipment and improving overall process reliability.