2019 de Vries C-Job Safe and effective application of ammonia as a marine fuel

Ammonia can be safely and effectively applied as a marine fuel to reduce harmful emissions in the maritime industry according to new research published today (12 June) by C-Job Naval Architects, the largest independent ship design and engineering company in the Netherlands.

The ground-breaking research uses a new concept design, an ammonia carrier fuelled by its own cargo, to study the concept of using ammonia as a marine fuel and achieve a significant reduction in greenhouse gas emissions in shipping. It shows ammonia can be used as marine fuel if a number of safety measures are included in the design.    

Niels de Vries, Lead Naval Architect at C-Job Naval Architects and research lead, says: “Reviewing all ammonia power generation options, the Solid Oxide Fuel Cell (SOFC) is clearly the most efficient. However, it does have practical challenges as the power density and load response capability are not on an acceptable level yet.

“Therefore, in the short term applying the internal combustion engine is the way to go.”

With the International Maritime Organisation goals to reduce total annual GHG emissions by at least 50% by 2050 compared to 2008 and eventually fully eliminate harmful emissions, it is of the utmost importance that the global maritime industry looks into renewable fuels like hydrogen, ammonia and methanol.


‘Safe and effective application of ammonia as a marine fuel’ research key findings

  • To realise ammonia as a marine fuel, a stepwise implantation could accelerate the application of ammonia as a marine fuel with in the first stage ammonia with marine diesel in an (Compression Ignition) Internal Combustion Engine (ICE). The second stage is an ICE using ammonia hydrogen mixtures followed by the third and final stage an SOFC using ammonia.
  • Reviewing all remaining options (ICE, Proton Exchange Membrane Fuel Cell (PEMFC), Alkaline Fuel Cell (AFC) and SOFC) the SOFC is clearly the most efficient with a system efficiency of 53.9%. However, the SOFC does have practical challenges as the power density and load response capability are not at an acceptable level yet. Furthermore, despite the higher efficiency of the SOFC the total cost of ownership (ΔTCO) is still higher than the ICE based on these guidelines and estimations. The (two-stroke, low speed) internal combustion engine is second in efficiency with a system efficiency of 49.4% and therefore more efficient than the PEMFC and the AFC with a system efficiency of 44.5% and 44.8% respectively. Furthermore, the ICE is less expensive, more robust and has acceptable power density and load response capability. In the future further development of fuel cell technology might change the outcome of this evaluation. Based on the comparison the ICE is currently selected as best option for this project.
  • Comparing the ammonia ICE option with the conventional fossil fuelled ICE option the technical performance is similar on power density, load response, part load performance, coping with marine environment and system efficiency. However, the conventional option has significantly more harmful emissions (with NOx assumed to be similar). Studying the cost based on equal range the ammonia powered option is clearly more expensive, about 3.2 times the expenses of the conventional option. This follows from a basic cost scenario of 850 euro per ton ammonia and 500 euro per ton low sulphur 0.5% HFO. Looking into future scenarios the ammonia powered option can be in similar cost range as the conventional option. This is the case when using 400 euro per ton ammonia, based on low electricity cost, combined with either a 500 euro per ton HFO with 100 euro per ton CO2 taxation or 811 euro per ton HFO without CO2 taxation.
  • To safely handle ammonia (and hydrogen) as a fuel, spaces containing fuel lines should be equipped with ammonia (and hydrogen) detection combined with ventilation. Furthermore, in case of leakages remote operated shut-off valves should be installed to isolate the leakage and limit its impact. In line with this mitigation, redundancy in the fuel supply line should be arranged to ensure sufficient fuel supply for continuous operation in case part of the fuel supply is shut-off. In addition, in case of a blackout the main remote operated isolation valves should be installed with a fail close so when there is a loss of power the valves close automatically. As ammonia exposure to humans and the environment should be limited as much as possible, fuel lines should be routed with a sufficient distance from the shell, for example B/5 from the side. Where possible, fuel lines should be located in separate unmanned spaces. Where impossible, for example in the engine room, double-walled piping with pressure transmitters should be applied.
  • The ammonia fuel treatment room and similar to other fuel systems, the engine room, should be equipped with fire detection and a fire fighting system. Furthermore, to monitor the conditions of the fuel, pressure transmitters, temperature transmitters and flow detectors should be added. In addition, to cope with overpressure a pressure relieve system should be installed.
  • The main ship design consequences of the mitigations are on the arrangement due to the required separate spaces for the redundant fuel supply lines covering fuel trunks and fuel treatment rooms. Furthermore, the ventilation of the spaces containing fuel supply lines also require space for the intake and exhaust of air. The requirement of routing with sufficient distance from the side also impacts the effective use of available space of the vessel. All these factors increase the cost, especially the redundancy requirement. Therefore, implementation of 2 x 50% system capacity instead of 2 x 100% is considered to be important to limit these additional costs. The system design indicating the consequences on the arrangement is available separately upon request or can be found in the appendix of the link below.
  • As an ammonia carrier is used for the ammonia fuel system the main issue of ammonia fuel storage is not addressed as it was covered by existing regulations. Therefore, it is recommended to further investigate ammonia fuel storage so it can be applied on other ship types as well.
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