BOG Reliquefaction with Hydro Puls Direct-Drive (HPDD)

Transforming Costly Boil-Off Vapor into 100% Liquid Yield

An application devised by Bandhan Udeshi

The BOG Problem

During storage and transport of liquefied natural gas (LNG), external thermal ingress and vessel motion cause continuous product vaporization: Boil-Off Gas (BOG). Traditional management methods — continuous flaring, burning BOG in auxiliary boilers, or operating complex multi-stage compressor trains — lead to substantial revenue loss, elevated carbon intensity, and severe maintenance burdens.

Revenue Loss

Vaporized cargo is burned or vented rather than recovered as saleable LNG.

Carbon Intensity

Flaring and combustion raise emissions under tightening IMO and MARPOL standards.

Maintenance Burden

Complex rotating machinery demands constant upkeep and costly downtime.

Key Challenges of Conventional Reliquefaction

Bulky Rotating Turbomachinery

Multi-stage centrifugal or reciprocating compressors require heavy gearboxes, complex oil-free sealing systems, and massive vibration foundations that consume scarce deck space.

Severe Part-Load Penalties

BOG generation rates vary widely across sea states and operations. Conventional compressors suffer drastic thermodynamic penalties when throttled or placed on bypass recycle.

Tightening Maritime Regulations

Under evolving IMO, MARPOL, and FuelEU Maritime standards, methane venting and unnecessary combustion face severe regulatory penalties and emissions taxation.

Introducing HPDD: A Paradigm Shift

The HPDD Principle

Hydro Puls Direct-Drive (HPDD) replaces mechanical rotating drivetrains with direct reactive pulse dynamics, producing deep cryogenic cooling at -180°C as an intrinsic, zero-parasitic byproduct — reliquefying vaporized gas with unmatched energy efficiency.

From Liability to Asset

HPDD transforms BOG management from an operational liability into a closed-loop, highly efficient recovery cycle. Every kilogram of boil-off is converted back into saleable or usable liquid fuel — zero flaring, zero methane slip.

Conventional vs. HPDD: Technical Comparison

HPDD delivers 99% reliability, 30% lower Capex, a compact modular skid, and a fully gearless design — eliminating the complexity and wear of conventional multi-stage systems.

Direct Condensation Without Compression Trains

The cold BOG stream is drawn directly into a compact Printed Circuit Heat Exchanger (PCHE) core cooled by the -180°C pulse sink. This returns pure liquid LNG to cargo tanks without the overhead of auxiliary multi-stage compressor skids — simplifying the system and eliminating a major failure point.


Exceptional Turndown Flexibility

The Challenge

Transient boil-off spikes and changing weather conditions demand a system that can respond instantly without thermodynamic penalty — something conventional compressors cannot achieve.

The HPDD Solution

HPDD manages variable BOG purely by modulating pulse stroke frequency rather than choking flow through valves, keeping specific energy consumption flat across the entire operating envelope.

Zero Flaring. Zero Methane Slip.

100% Liquid Yield

HPDD retains the full energy density of the cargo by converting every kilogram of boil-off back into saleable or usable liquid fuel — eliminating both flaring losses and methane slip emissions entirely.

-180°C

Pulse Sink Temperature

Deep cryogenic cooling produced as a zero-parasitic byproduct.

99%

System Reliability

Gearless, direct-drive design with no rotating wear components.

30%

Lower Capex

Compact modular skid versus conventional large-footprint installations.

Optimized for Floating & Bunkering Assets

The ultra-compact skid geometry eliminates heavy rotating mass and vibration dampening frames, optimizing deck area, center of gravity, and structural payload limits on floating assets.

FLNG Vessels

Minimal footprint suits space-constrained floating liquefaction platforms.

FSRUs

Ideal for floating storage and regasification units requiring reliable BOG control.

Bunkering Vessels

Compact design supports LNG bunkering operations with zero methane slip.

Contact Engineering

To evaluate mass-energy balance models, process flow diagrams, and battery-limit integrations for your specific vessel profile or terminal inventory, reach out to the HPDD engineering team.

Mass-Energy Balance Models

Tailored thermodynamic analysis for your BOG generation profile.

Process Flow Diagrams

Full system integration mapping for vessel or terminal configurations.

Get in Touch

Contact us at [email protected] to begin your engineering evaluation.