Liquefied natural gas (LNG) is increasingly viewed as a promising fuel for dual-fuel ships due to its cost-effectiveness, low emissions, and alignment with regulatory requirements. However, the high methane content of LNG, ranging from 85% to 95%, presents a significant challenge because of the phenomenon of methane slip whereby unburned methane escapes from the engine’s combustion chamber and other parts of the storage and transportation systems. Methane slip, which peaks at low ship speeds and decreases at higher speeds, can lead to substantial environmental pollution if it is not properly managed. This study rigorously examines the impact of sailing speed on methane slip rates and recognizes the complexities of fuel usage in dual-fuel ships. We develop a nonlinear mixed-integer programming model designed for container shipping companies that aims to optimize fleet composition, sailing speed, and fuel usage strategies. The objective of the model is to minimize total operational costs, including fuel expenses and taxes related to carbon emissions and methane slip. To address the computational challenges posed by the model’s nonlinearity, we propose a tailored solution method that uses sailing time as a proxy for speed, discretizing these times for effective implementation. The validity of this method is supported by theoretical guarantees and demonstrated through numerical experiments. Our computational results indicate that accounting for methane slip in the operational management of dual-fuel ships can help mitigate financial losses under certain conditions.

中文翻译：

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考虑甲烷泄漏优化双燃料船舶运营

液化天然气 （LNG） 因其成本效益、低排放和符合监管要求而越来越被视为双燃料船舶的一种有前途的燃料。然而，液化天然气的甲烷含量高达 85% 至 95%，这带来了重大挑战，因为甲烷逃逸现象使未燃烧的甲烷从发动机的燃烧室和储存和运输系统的其他部分逸出。甲烷滑移在低船速时达到峰值，在较高速度时减少，如果管理不当，可能会导致严重的环境污染。本研究严格研究了航行速度对甲烷滑移率的影响，并认识到双燃料船舶燃料使用的复杂性。我们开发了一个专为集装箱航运公司设计的非线性混合整数规划模型，旨在优化船队组成、航行速度和燃料使用策略。该模型的目标是最大限度地降低总运营成本，包括燃料费用以及与碳排放和甲烷泄漏相关的税收。为了解决模型非线性带来的计算挑战，我们提出了一种量身定制的求解方法，该方法使用航行时间作为速度的代理，将这些时间离散化以实现。该方法的有效性得到了理论保证的支持，并通过数值实验得到了证明。我们的计算结果表明，在某些情况下，在双燃料船舶的运营管理中考虑甲烷逃逸有助于减轻财务损失。