In the rapidly changing LNG market, securing a stable energy source has become a very important part due to political instability in the Middle East and Africa and the after-effects of the nuclear power crisis in Japan amid the continuous rise in oil prices in 2013. Accordingly, in Korea, stable LNG supply and demand is in progress through long-term LNG contract projects with the US and Australia. In the initial project stage, the size and number of vessels were determined according to the LNG cargo contract volume, and the performance characteristics of each propulsion system that can be mounted on the LNG carrier were compared and reviewed. In addition, the economics, eco-friendly, and ship operation stability in consideration of the CAPEX, OPEX, and fuel consumption were analyzed together. Through the analysis results, it was verified that the economics and eco-friendly evaluation results were different according to the difference in fuel consumption in the design stage and the operating ship.
As a result of analyzing fuel consumption for economic evaluation of the propulsion system, TLDFE showed similar fuel consumption as a result of the design and the operating ship analysis. And TLDFE was consumed a fuel about 230-240% less fuel than UST and FMDFE.
Air pollutant emission, which is an eco-friendly evaluation factor, showed relative emission in a similar pattern at the design stage and the ship in operation. As for the amount of CO2 emission, UST with the lowest fuel efficiency showed the highest amount, and as for NOx emission, TLDFE, which uses a lot of liquid fuel as pilot oil, showed the highest. In the case of NOx, the newly changed emission factors for each engine type were applied in the operating ship. The factors from the IMO are in consideration of the characteristics of dual-fuel engines using LNG. The derived value was reduced than the results which are applied the emission factors for each fuel type. And the SOx was analyzed as the highest in TLDFE, which also uses a lot of liquid fuel.
In terms of stability, FMDFE has an advantage over other engines in that, although there is a risk of periodic generator maintenance, FMDFE is possible to conFig a redundant system to prepare for the loss of propulsion due to major equipment of the ship. Due to the characteristics of the engine, the UST has a large engine room, so UST was difficult to realize the duplication of the propulsion system. Many repair work due to leakage in the operating ship for TLDFE with the high-pressure gas(300 bar) injection method, which was a potential risk factor analyzed during the design stage.