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The rapid development of the shipping industry has made energy consumption and environmental problems of traditional ships increasingly prominent. Considering the carbon peaking and carbon neutralization goals and the Initial IMO Strategy on Reduction of GHG Emissions from Ships, ammonia-hydrogen powered marine ships will become an important development direction for waterway transportation vehicles. This study explores the demand for and the international development status of ammonia-hydrogen powered marine ships and analyzes the key technologies, involving ship safety, fuel filling, hydrogen production from ammonia reforming, power production from ammonia and hydrogen, hydrogen production from renewable energy, ammonia synthesis based on renewable energy, and treatment of harmful pollutant discharge. Moreover, staged goals and upper/mid/lower-stream industrial elements are examined based on China’s national conditions. To promote the sustainable and innovative development of ammoniahydrogen powered marine ships in China, we propose the following suggestions: (1) implementing special plans for an ammonia and hydrogen fuel supply system and the infrastructure construction of ammonia-hydrogen powered marine ships, (2) strengthening the maintenance of supportive service facilities, and (3) accumulating engineering experience to provide support for the subsequent large-scale industrial chain and infrastructure construction.

To meet the requirement of reducing greenhouse gas (GHG) emissions, the application of carbon-free fuel ammonia in marine engines has gained importance. However, the use of ammonia as fuel leads to low thermal efficiency and high emissions of pollutants in engines. Increasing the rate of combustion of the fuel mixture in the engine helps to solve this problem. Therefore, the influence of hydrogen volume fraction (XH2) and oxygen volume fraction (XO2) in the main chamber, via numerical simulations, on the combustion and emission characteristics of a marine ammonia engine featuring a pre-chamber. Further analysis was conducted via adjustments in the start of ignition (SOI) to optimize both engine performance and emissions. The results showed that the increase of both XH2 and XO2 contributed to the improvement of indicated thermal efficiency (ITE) and the reduction of N2O emissions. However, this is usually accompanied by higher NOx emissions, especially in the case of high XO2. In addition, adjusting the SOI resulted in the engine ITE is greater than 47.6% in each case and reduces GHG emissions by about 80% (<40 ppm N2O). Finally, chemical kinetic analysis showed that oxygen-enriched or hydrogen-enriched conditions did not change the main reaction pathway. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Pollutants such as nitrogen oxides (NOx), sulfur oxides (SO2), and particulate matter (PM) in ship exhaust have a great impact on human health, environment and climate conditions. Combined selective catalytic reduction technology and dry exhaust gas cleaning technology, a test rig (SCR-DryEGCS system) for WD10C195-15 marine four-stroke high speed diesel engine was established to analyse the removal effect of NOx, SO2, and PM from exhaust gas. The SCR-DryEGCS system removed 89.03%, 99%, and 96% of NOx, SO2, and PM respectively. And also compared with low sulfur oil combined SCR method to verify the feasibility of the SCR-DryEGCS method. It shows that the SCR-DryEGCS system has its own advantages and has a good effect on the removal of NOx, SOx, and PM at the same time. [ABSTRACT FROM AUTHOR]