The LNG carriers are undergoing a period of rapid and profound change, with much larger size ships and novel propulsion systems emerging for fulfilling the market trends of LNG shipping industry. There are various proposed propulsion solutions for LNG carriers, ranging from the conventional steam turbine and dual fuel diesel electric propulsion, until more innovative ideas such as slow speed dual fuel diesel engine, combined gas turbine electric & steam system, and hybrid propulsion based on steam turbine and gas engine. Since propulsion system significantly influenced the ship's capital, emission regulation compliance and navigation safety, the selection of a proper propulsion option with technical feasibility and economic viability for LNG carriers is currently a major concern from the shipping industry and thus must be comprehensively assessed. In this context, this chapter investigated the main characteristics of these propulsion options in terms of BOG treatment, fuel consumption, emission standards compliance, and plant reliability. Furthermore, comparisons among different propulsion system were also carried out and related evaluation was presented.
The maritime industry is getting prepared for using ammonia as a fuel to meet the decarbonization goal. However, ammonia is toxic, corrosive, and flammable, which poses specific safety challenges during bunkering compared with conventional fuels.The corrosion can be prevented by selecting suitable materials. However, the impact of toxic gas dispersion and fire has high uncertainties, thus risk assessment should be conducted. Currently, there are insufficient risk assessment guidelines for ammonia bunkering available. Therefore, this paper proposes a Bayesian network (BN) based quantitative risk assessment framework to investigate the potential risks of ammonia in ship-to-ship bunkering considering the toxicity and flammability. The study validates the utility of the proposed framework and demonstrates the BN as an efficient model in performing the probabilities calculations and flexible in conducting causal diagnosis. The results show that toxicity has the greatest impact on the risks of ammonia bunkering compared with flammability. The main innovation of this work is realizing the efficient quantification of risks for ammonia ship-to-ship bunkering by using the BN.
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