LNG-capable supply vessel gears up for ammonia conversion

Finnish engine maker Wärtsilä has started the ammonia retrofit of an LNG-capable offshore platform supply vessel chartered by Equinor.

IMAGE: The offshore platform supply vessel Viking Energy. Eidesvik Offshore

The offshore platform supply vessel, Viking Energy, is owned by the Norwegian shipping company Eidesvik Offshore.

As part of the retrofit, Wärtsilä will install an ammonia dual-fuel engine, a fuel gas supply system and an exhaust after-treatment system onboard the vessel.

The four-stroke ammonia dual-fuel engine will use selective catalytic reduction (SCR) technology to reduce nitrogen oxide emissions produced during ammonia combustion.

The fuel supply system includes a purge gas treatment system to remove residual ammonia from fuel lines, tanks and other components where gas may accumulate. The process typically uses nitrogen to flush out the remaining fuel from the piping.

Since nitrogen does not easily react with other substances, it helps stabilise the system and reduce the risk of fires or other safety incidents.

The engine also includes an additional safety feature known as an "ammonia release mitigation system”, which is designed to protect against ammonia leaks. Wärtsilä explains that this system breaks down leaked ammonia emissions into nitrogen and water, reducing ammonia emissions to less than 30 parts per million (ppm).

“Due to the need for high cleanliness of the fuel, proper filtering upstream is installed and embedded in the system,” Wärtsilä added.

Need for pilot fuel

Ammonia as a fuel requires a pilot fuel, such as diesel, for ignition because its high auto-ignition temperature makes it difficult to burn readily or sustain combustion. Wärtsilä said engine load tests confirmed pilot fuel consumption of around 5-10% across multiple load conditions.

By Konica Bhatt

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