Tackling ammonia slip and NOx emissions

Finnish engine maker W?rtsil? will retrofit an offshore platform supply vessel owned by Norwegian shipping company Eidesvik Offshore to run on ammonia. W?rtsil? will provide an ammonia dual-fuel engine, a fuel gas supply system and an exhaust after-treatment system for the retrofit, which is scheduled to be completed in 2026.

There are currently 25 ammonia-capable vessels on order for delivery by 2027, according to DNV. But before ammonia can be commercially deployed as a bunker fuel, stringent regulations must be implemented for handling and storing it. Equally important is the need to mitigate stray ammonia emissions, known as ammonia slip, and nitrogen oxide (NOx) emissions from burning ammonia.

Ammonia itself is highly toxic. Nitrous oxide, a major component of NOx, has a global warming potential (GWP) that is approximately 264 times greater than CO2 over a 20-year period, according to the Intergovernmental Panel on Climate Change's (IPCC) Fifth Assessment Report. As a result, marine engine manufacturers working on ammonia dual-fuel engines are prioritising both safety measures to prevent ammonia slip and emissions control technologies to limit NOx release.

Engine makers like W?rtsil?, MAN Energy Solutions and Winterthur Gas & Diesel (WinGD) are developing ammonia engines with technologies such as ammonia release mitigation, selective catalytic reduction (SCR) and nitrogen purging. Norwegian ammonia firm Azane Fuel Solutions recently got its ammonia release mitigation system approved by DNV.

An ammonia release mitigation system captures possible ammonia leaks from fuel supply and engine systems, and breaks down ammonia into nitrogen and water. Azane claims the system is compatible with multiple vessel designs, though it has not specified the extent of the emission reductions.

W?rtsil? says its mitigation system reduces ammonia emissions to less than 30 parts per million (ppm). "In fact, in most cases, NH3 emissions are close to 0 ppm," the company claims.

Selective catalytic reduction (SCR) technology lowers NOx emissions by injecting a reducing agent, typically ammonia or urea, which reacts to form nitrogen and water. Nitrogen purging technology helps to flush out residual ammonia in the fuel piping. As an inert gas, nitrogen helps stabilise the fuel supply system and reduces the risk of dangerous incidents.

WinGD claims its ammonia engines will feature “leak detection systems, emergency shutdown systems, double-wall barriers, ventilation, and fire suppression systems” to limit ammonia slip and NOx emissions while preventing leaks from engines and fuel supply systems.

Singapore, a major bunker hub, has also supported efforts to reduce NOx emissions and enhance safety measures against onboard ammonia leaks.

Earlier this year, the Maritime and Port Authority of Singapore (MPA) trialled ammonia as a bunker fuel on a Fortescue vessel. The vessel was equipped with a nitrogen purging system and an ammonia treatment system. It underwent rigorous testing of its storage systems, piping, fuel delivery system and retrofitted engines to ensure safe operations for the port, crew members and engineers. The MPA also noted that NOx emissions from the trial remained within local regulatory limits.

In other news, Swedish e-fuel company Liquid Wind will develop and build a 100,000 mt/year e-methanol plant for German energy supplier Uniper. The fuel produced will primarily be supplied to the shipping and chemical sectors, according to Uniper.

A group of Japanese companies has launched a joint study to establish standard specifications and designs for liquid CO2 carriers. They aim for Japanese shipyards to build these carriers, and will also look to design and build ships capable of running on ammonia.

The UAE and the International Parcel Tankers Association (IPTA) have proposed a new formula for Carbon Intensity Indicator (CII) calculations. The formula adds an assumed value for equivalent transport work into the denominator, which will adjust for fuel losses. This is because of factors beyond the ship’s control, and it will estimate how far the ship could have sailed with that extra fuel under ideal conditions.

By Konica Bhatt

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