Desalting Purpose

Crude oil contains dissolved salts, suspended water, and sediments. Salts cause corrosion and fouling in furnaces, heat exchangers, and distillation towers. Desalters remove 90-99% of salts by extracting water containing dissolved minerals before processing.

Process Operation

Crude mixes with fresh water dissolving salts from oil phase into water. Chemical demulsifiers destabilize emulsion. Electric field coalesces water droplets. Large drops settle by gravity to bottom. Clean oil exits overhead. Brine drains containing removed salts.

Vessel Design

Horizontal pressure vessel with crude-water inlet after mixing, electric grid creating field zone, oil collection section, brine settling zone with water outlet, and cleaned crude outlet. Electrodes span vessel width creating uniform field.

Electric Field

High-voltage AC or DC field between 10-35 kV polarizes water droplets. Charged drops attract and coalesce into larger droplets. Large drops separate faster by gravity. Electrostatic treatment reduces retention time and vessel size versus gravity alone.

Operating Conditions

Pressure typically 50-150 psig, temperature 110-150C for optimal emulsion breaking. Warm temperature reduces oil viscosity improving separation. Design handles crude throughput from 10,000 to 200,000 BPD.

Material Selection

Carbon steel vessel construction. Electrode materials resist corrosion from brine. High-voltage insulators prevent electrical leakage. Internal coatings protect brine contact zones. Design accommodates corrosive environment.

Chemical Injection

Demulsifiers break tight emulsions chemical treatment cannot separate alone. Dosage 5-50 ppm depending on crude properties. Proper chemical selection critical for efficiency. Injection upstream allows mixing time before desalter.

Water Management

Fresh wash water dilutes salts extracting from oil phase. Water-to-oil ratio typically 3-10% by volume. Separated brine contains dissolved salts for disposal or treatment. Water quality affects desalting efficiency.

Interface Control

Level instruments maintain oil-water boundary. Improper interface causes water in oil outlet or oil loss in brine. Careful control critical for performance. Automated systems manage varying throughput.

Performance Benefits

Reduces crude salt content from 30-300 PTB to under 5-10 PTB meeting refinery limits. Prevents corrosion saving millions in maintenance. Protects catalysts in downstream units. Essential crude preparation for safe refining.

Construction Standards

Design per ASME Section VIII for pressure service. Electrical systems per applicable codes for hazardous areas. Materials for corrosive crude and brine. Complete documentation with desalting guarantees.

ERGIL electrodynamic desalters protect refinery equipment through efficient crude oil salt and water removal in petroleum processing.