| A marine energy system have been synthesized from state-of-the-art technology to convert nuclear derived electricity into liquefied methane. In the first part of the process, the on-board process, liquid methane is burned in a combined gas turbine-steam turbine system to provide propulsion power and the carbon dioxide created during combustion recovered. In the second part of the process, the fuel regeneration process, the methane is regenerated in a centralized land-based facility by the reaction of the recovered carbon dioxide with hydrogen obtained from nuclear-powered electrolysis of water. The system was analyzed by combining thermodynamic available energy analysis and an approximate preliminary design. The available energy analysis of the combined system established the thermodynamic feasibility of the methane-carbon dioxide cycle and resulted in various process improvements because of the inefficiencies disclosed by the analysis.;The more critical on-board process was analyzed and developed further by a capital cost optimization and ranking alternate process options by their available energy consumptions. The analysis was conducted by developing a flexible APL process simulator supplemented by various equipment performance models, including one developed for a pressure swing adsorber used in the carbon dioxide recovery step. The use of simplified models to characterize the process behavior emphasized the importance of monotonicity in optimizing constrained objective functions. The monotonic nature of the process cost with respect to the gas turbine inlet pressure and temperature, the steam turbine inlet pressure, and the carbon dioxide adsorber diameter and desorption pressure led to an optimal design in which these variables attained either their highest or lowest allowable values. The optimal on-board process, whose capital cost is 16% less than the preliminary design, has an effectiveness of 47% and the fuel regeneration process an effectiveness of 56%. It was also found that the process cost was proportional to the horsepower raised to the seven-tenths power. |
