In order to mitigate global warming induced by enormous amounts of carbon dioxide emission, RITE(Chemical CO2 fixation project)investigated and evaluated renewable energy transporting system which synthesizes methanol by catalytic hydrogenation for separated and recovered CO2. This system is called ¡ÇCO2 global recycle system¡Ç which is composed of four processes: CO2 separation and liquefaction process, methanol synthesis process, water electrolysis for hydrogen production and supply process, and transportation process. For the optimization of the total system, case studies of the total system have been conducted, and also energy conservation and efficiency improvement of each process have been studied.
In this paper, we developed the simulation model for the total system, and evaluated the optimum conditions from several criterions, that is, energy efficiency, methanol production cost, CO2 reduction rate. We also analyzed the factors and characteristics that mainly affect the optimum conditions. We figured out with the simulation analysis that the optimum conditions much depend on the selection of criterion, and that the methanol production cost is an appropriate criterion for total system design. We can conclude that the several processes that compose a large-scaled system such as the CO2 global recycle system should be designed taking the total system performance into account even though each process can be independently operated.