Submerged Combustion Vaporizers (SCVs) FOR LNG system - Working Principle

Submerged Combustion Vaporizers (SCVs) for LNG are highly efficient heat exchangers that use a burner to combust fuel gas (often natural gas) directly into a water bath. The hot exhaust gas heats the water, which in turn vaporizes LNG flowing through stainless-steel coil tubes submerged in the bath, providing rapid start-up and reliable, consistent operation.

Key Working Principles

• Fuel Combustion: A submerged burner creates hot exhaust gases, typically using natural gas as fuel.
• Direct Heat Transfer: The hot exhaust gases pass through a distributor/sparger, releasing heat directly into the water bath, ensuring fast heating.
• LNG Vaporization: LNG travels through a submerged coil tube bundle. The hot water rapidly heats the cryogenic LNG, causing it to turn into gaseous natural gas.
• High Efficiency & Agitation: The sparged air bubbles stir the water bath (agitation), enhancing heat transfer coefficients.
• Temperature Control: The large water bath volume maintains a stable, controlled temperature that prevents the LNG coils from freezing (typically, water bath temperature is kept around 20°C to 50°C).

Working Principle

• Fuel Combustion: Fuel gas (typically natural gas or boil-off gas) is mixed with air and burned in a downward-facing burner.
• Submerged Exhaust: The hot combustion gases (flue gas) are discharged directly into a water bath through a sparger or distributor located below the water level.
• Heat & Mass Transfer: The hot gases bubble through the water, transferring heat directly to it. This creates a highly turbulent, two-phase (gas-water) mixture.
• Agitation & Lift: The bubbling action creates a "pneumatic lift" effect, causing the water to circulate rapidly around the LNG tube bundles.
• LNG Vaporization: LNG flows through stainless steel tube coils submerged in this heated, turbulent water. The heat from the water vaporizes the LNG inside the tubes as it moves from the inlet to the outlet.
• Exhaust: The cooled flue gas is discharged through an exit stack.

Key Components

• Burner & Sparger: Submerged system for combustion and exhaust distribution.
• Water Bath/Tank: A stainless-steel tank or concrete pit holding water.
• Heat Exchanger Tubes: Stainless-steel coils where LNG is vaporized.
• Sparger/Distributor: A series of perforated pipes that release hot flue gas into the water.
• Stack: Releases the cooled exhaust gases safely.

Advantages in LNG Systems

• Fast Response: Capable of quick startup, shutdown, and handling rapid load changes, making them ideal for peak shaving.
• Reliability: The large water bath acts as a thermal buffer, reducing the risk of ice formation on tubes.
• Compact Footprint: Often smaller than atmospheric vaporizers, saving space.