Fuel Switching Systems with NH₃, Methanol & Hydrogen

The New Era of Marine Fuel Switching

The maritime sector is entering a transition phase. In the coming decade, ships will increasingly switch between conventional fuels and new low-carbon alternatives such as ammonia (NH₃), methanol and hydrogen. These fuel types enable cleaner operations in coastal waters, ports and emission-controlled zones. However, they also introduce new safety challenges, new emission risks and stricter requirements for handling purge gases and vented residues produced by the Fuel Supply and Return System (FSRS).

During every fuel switch – whether from HFO to MGO, or from marine gas oil to NH₃ – the fuel line must be purged. The resulting gas mixture can contain ammonia slip, methanol vapour, formaldehyde, trace fuel residues, aromatics, VOCs or even hydrogen-enriched gas streams. These cannot simply be released to atmosphere. Ports and classification societies require controlled treatment.

This is exactly where modern Marine Fuel Switching Scrubbers provide value. They ensure safe, compliant and efficient purification of vented gases before discharge or recirculation.

Why Scrubbers Are Essential for Fuel Switching

While ship exhaust scrubbers for HFO compliance are now common, fuel switching applications demand a different level of engineering. The gas composition is entirely different, the concentrations are higher, and the systems operate in closed, safety-critical environments.

A tailored wet gas scrubber captures and neutralizes these components, ensuring safe handling and fully controlled disposal. For ammonia, this means acid washing. For methanol and VOCs, water-based absorption followed by oxidation or biological treatment. For formaldehyde, peroxide scrubbing provides excellent results. For H₂S, alkaline oxidative scrubbing is the safest route.

Typical Marine Fuel Switching Process Flow

Below is a simplified representation of a modern fuel switching line incorporating FSRS, valve trains and a dedicated scrubber unit.

The scrubber sits at the critical point where vented gas must be stripped of hazardous components before discharge. This makes it an essential safety and compliance component during low-carbon fuel transitions.

Scrubber Design for NH₃, Methanol and Hydrogen

1. Ammonia (NH₃) Fuel Switching

Ammonia offers zero-carbon combustion but introduces aggressive toxicity risks. Fuel switching results in concentrated ammonia slip that must be carefully neutralized. A packed-bed scrubber with acid wash (usually diluted H₂SO₄) captures >99% of ammonia at minimal pressure drop. Sensors and redundant monitoring ensure full safety during operation.

2. Methanol Fuel Switching

Methanol is easier to handle but volatile and flammable. During switching, methanol vapour and formaldehyde can be released. Water scrubbing removes the methanol, while peroxide (H₂O₂) or bisulfite can treat formaldehyde. A corrosion-resistant design is essential because methanol condensate can be reactive.

3. Hydrogen Fuel Switching

Hydrogen purging produces mixtures that may contain trace hydrocarbons or oxygen depending on system design. While hydrogen itself is not scrubbed, contaminants must be removed before controlled venting. The scrubber ensures the vent gas is inert and below LEL limits before discharge.

Benefits for Ship Owners and System Integrators

Why Shipyards Choose Ravebo

Ravebo specializes in high-end wet scrubbers for industrial and maritime applications. Our systems are not generic “EGCS” units; they are engineered to match the precise chemistry and process conditions of the fuel switching environment. With decades of experience in emissions control, BTEX removal, odor control and hazardous gas scrubbing, our solutions offer reliability, safety and long operational lifespan.

Whether you are designing a retrofit package, a newbuild fuel system, or a hybrid fuel arrangement, Ravebo supports you from early engineering to commissioning and lifecycle maintenance.