The shipping industry has reached a higher level of maturity in terms of its knowledge and awareness of decarbonization challenges. Carbon-free or carbon-neutralized green fuel, such as green hydrogen, green ammonia, and green methanol, are being widely discussed. However, little attention has paid to the green fuel pathway from renewable energy to shipping. This paper, therefore, provides a review of the production methods for green power (green hydrogen, green ammonia, and green methanol) and analyzes the potential of green fuel for application to shipping. The review shows that the potential production methods for green hydrogen, green ammonia, and green methanol for the shipping industry are (1) hydrogen production from seawater electrolysis using green power; (2) ammonia production from green hydrogen + Haber–Bosch process; and (3) methanol production from CO₂ using green power. While the future of green fuel is bright, in the short term, the costs are expected to be higher than conventional fuel. Our recommendations are therefore as follows: improve green power production technology to reduce the production cost; develop electrochemical fuel production technology to increase the efficiency of green fuel production; and explore new technology. Strengthening the research and development of renewable energy and green fuel production technology and expanding fuel production capacity to ensure an adequate supply of low- and zero-emission marine fuel are important factors to achieve carbon reduction in shipping.

The gradual opening of the Arctic shipping route has made navigation possible. However, the harm caused by ship exhaust emissions is increasingly severe. Therefore, it is necessary to study the diffusion characteristics of ship exhaust plumes during Arctic navigation. The study focuses on a merchant vessel as the subject of investigation, employing computational fluid dynamics (CFD) simulation techniques to analyze the diffusion characteristics of particulate matter (PM) within ship exhaust plumes under Arctic environmental conditions. The diffusion law of ship exhaust plume PM is clarified, and the influence of three factors, synthetic wind speed, yaw angle and chimney angle, on the PM diffusion is analyzed. It was found that after the PM was discharged from the chimney, the majority of the PM dispersed directly backward along with the external flow field, while a minor fraction lingered at the stern of the ship for an extended period before eventually diffusing backward. Among them, 1235 particles were captured within a range of 200 m from the stern, with a capture rate of 0.6%. When the synthetic wind shows a yaw angle, the capture rate of PM in the interval increases rapidly with the increase of yaw angle, while other factors have less influence on the capture rate of PM. This study provides foundational guidance for predicting PM diffusion from ship exhaust plumes in Arctic environments, thereby enabling more effective strategies for managing such emissions.

LNG is a potential alternative fuel for ships. Generating H₂ through exhaust reforming is an effective method to improve the performance of the LNG engine and reduce its pollutant emissions. It is necessary to study the mechanism of methane exhaust reforming to guide the design of the reformer. Based on the detailed mechanism, the characteristics of methane reforming reaction were studied for a marine LNG engine. Firstly, the reforming characteristics of exhaust were studied. The results show that methane reforming requires a lean oxygen environment, and the hydrogen production reaction will not occur when the O₂ concentration is too high. Then, the effects of the O₂/CH₄ ratio (0.2–1) and H₂O/CH₄ ratio (0–2) on the reforming reaction were studied. The results show that under O₂/CH₄ = 0.4, the molar fraction of hydrogen at the outlet of the reactor decreases with the increase in the H₂O/CH₄ ratios. Finally, a mechanism analysis was conducted. The results show that an oxidation reaction occurs first and then the steam reforming reaction occurs on palladium-based catalysts.

In the operation of a high-pressure selective catalytic reduction (HP-SCR) system, variations in the internal exhaust gas flow speed result in non-uniform pressure and temperature distribution within the reactor. These fluctuations, which are neither constant nor linear, can affect the safe and reliable operation of the high-pressure selective catalytic reduction (HP-SCR) system, so the strength simulation analysis is necessary. Based on the high-pressure selective catalytic reduction system of a thermo-fluid-solid coupling marine diesel engine as the research object, this study constructs a calculation model using Space Claim and utilizes computational fluid dynamics (CFD) and computer-aided engineering (CAE) numerical simulation methods to analyze the strength of the high-pressure selective catalytic reduction (HP-SCR) reactor. The results show that the overall pressure drop of the selective catalytic reduction system is 5500 Pa, and the overall temperature rise of the reactor is 24 °C, which mainly occurs in the first layer catalyst, accounting for 62.5%. The pressure and temperature load of the reactor change along the axial direction, and the axial deformation gradient of the cylinder is more. The maximum deformation of the reactor under thermal load is 15 times that under mechanical load, and 97% of the deformation is axial.