Flash Separation Principle

High-pressure liquid contains dissolved light components. Pressure reduction vaporizes these dissolved gases creating two-phase mixture. Flash vessel provides residence time allowing vapor-liquid disengagement by gravity. Vapor exits overhead while liquid flows to next process step.

Vessel Configuration

Vertical or horizontal drum depending on vapor-to-liquid ratio. Inlet from pressure reduction valve, vapor space for disengagement, liquid collection zone, vapor outlet to compression or recovery, and liquid outlet to downstream equipment. Sizing based on retention time and vapor velocity limits.

Pressure Reduction

Flash pressure selected balancing vapor recovery against liquid loss. Too low wastes liquid flashing to gas. Too high leaves recoverable components in liquid. Optimization depends on economics and downstream requirements.

Operating Applications

Rich amine flash removing dissolved hydrocarbons before regeneration. Condensate flash recovering light ends. Hot oil flash in delayed coking. Flashed steam in geothermal power. Any process using pressure reduction for separation.

Material Selection

Carbon steel for hydrocarbon service. Stainless steel for corrosive fluids or high-purity applications. Design handles operating temperature which may be elevated from upstream process. Materials resist both liquid and vapor phases.

Vapor Recovery

Flashed vapor routes to compression, fuel gas, or flare depending on composition and facility requirements. Recovery captures value from dissolved components. Some systems use multi-stage flash with progressively lower pressures maximizing recovery.

Level Control

Level instruments regulate liquid discharge maintaining inventory. Controllers coordinate with downstream equipment. High-level protection prevents vapor line flooding. Low-level alarm indicates upstream flow problems.

Flash Efficiency

Proper retention time allows vapor-liquid equilibrium. Typically 2-5 minutes depending on fluid properties. Adequate vapor space prevents liquid entrainment. Mist eliminator captures remaining droplets in some applications.

Performance Factors

Temperature affects vapor-liquid equilibrium. Higher temperature increases vaporization. Pressure differential drives flash. Liquid composition determines which components vaporize. Design accounts for specific process conditions.

Construction Standards

Design per ASME Section VIII for operating pressure. Materials suitable for both phases. Relief protection for thermal expansion or blocked outlets. Complete documentation with flash calculations and equilibrium data.

ERGIL flash vessels provide efficient vapor-liquid separation through controlled pressure reduction recovering valuable components in refining and chemical processes.