A preliminary safety assessment of fuel gas supply system in the engine room of the ammonia fuelled ship

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Ammonia is a promising option for hydrogen storage, offering high density, low-pressure storage, and stability. Ammonia engines are increasingly adopted in vessels like ferries and cargo ships, showing promise for emissions reduction and economic benefits. However, its toxic, flammable, and corrosive nature poses safety challenges compared to other fuels. The study is identified risks associated with the release, dispersion, and hazardous zones of ammonia. A standardised procedure for assessing the risk of ammonia release in the engine room is established. The case study involves the unintentional release of ammonia in the engine room of a 299 GT general cargo ship. The FLACS-CFD 22.2 is employed to model the leakage of ammonia in the engine room under various leakage scenarios. The study examines the influence of leak rates (0.05 , 1 kg/s, 10 kgs and 50 kg/s), leak directions (longitual, transverse and vertical leaks), and hole size (0.05, 0.5, 5 mm) on the dispersion behaviour of ammonia. The findings indicate that vapour cloud dispersion of ammonia tends to accumulate in the direction of the leakage, particularly at the corner formed by equipment, and surrounds the outlet ventilation. Two crucial factors affecting the dispersion and safety considerations in the engine room are the toxicity and flammable limits of ammonia. It is recommended to implement effective ventilation to reduce the harmful effects of ammonia release. This study contributes to the ongoing efforts in adopting ammonia as a viable alternative fuel in the maritime sector, contributing to reduced airborne exhaust emissions and environmental impact. Abbreviations: AER: Air exchange rate; ACH: Air changes per hour; BLEVE: Boiling liquid expanding vapour explosion; CFD: Computational Fluid Dynamics; DWT: Deadweight tonnage; EEOI: Energy Efficiency Operational Indicator; ESD: Emergency Shutdown; EEDI: Energy Efficiency Design Index; FGSS: Fuel gas supply system; GHG: Greenhouse gas emission; GT: Gross tonnage; HCN: Hydrogen cyanide gases; HP: Horse power; IMO: International Maritime Organization; ICE: Internal combustion engine; ISO: International Organization for Standardization; IGF Code: The International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels; LNG: Liquefied Natural Gas; LPG: Liquefied Petroleum Gas; MARPOL: The International Convention for the Prevention of Pollution from Ships; PPE: Personal protective equipment; PFP: Power to fuel to power; PRA: Probabilistic Risk Assessment; PPM: Parts per million; SEEMP: Ship Energy Efficiency Management Plan; SGMF: Society for Gas as a Marine Fuel; QRA: Quantitative risk assessment.