After the industrial revolution, air pollutant exhausted to the earth due to a lot of usage of fossil fuel has seriously affected the global environment and humans. According to increase of concentration of green house gas such as CO2 and methane in the atmosphere, the average temperature of surface of the earth has been increased gradually. IMO adapted Regulations in Annex VI - Prevention of Air Pollution from Ships (applicable from May 19th, 2005) sets limits to the emission of harmful pollutants such as sulphur oxide(Regulation 13), nitrogen oxide(Regulation 14) and particulate matter(PM). The IMO provides a provision for nations to specify areas with more stringent exhaust limits compared to MARPOL Annex VI. These areas are designated as Emission Controls Areas (ECAs).
In order to reduce CO2 as main source of global warming, IMO MEPC adapted EEDI(Energy Efficiency Design Index for new ships) and SEEMP(Ship Energy Efficiency Management Plan) as technical and operational measures to MARPOL Annex VI for inclusion of regulations on energy efficiency for ships (resolution MEPC.203(62)) in August 2011. The Energy Efficiency Operational Index (EEOI) has been introduced as IMO′s initiative for monitoring fuel consumption and CO2 emissions (CO2-Index) for ships in operation.
From an environmental point of view, natural gas has many benefits. As it contains no sulphur, it doesn't produce any SOx emissions. Since it is a gas fuel, there are almost no particles produced in the combustion process as well. When natural gas is burned in a low pressure lean burn engine, NOx emissions are reduced by up to 90% compared to oil fuelled engines. When natural gas is burned in a high pressure dual fuel engine, NOx emissions are reduced by about 13% compared to operating the same engine with fuel oil. CO2 emissions are also reduced when natural gas is burned instead of burning fuel oil with equivalent energy content, due to the optimal carbon to hydrogen ratio of natural gas. As one of measures to meet IMO requirement on NOx, SOx and CO2, Shipyards and manufacturers have been developing LNG fuelled ship with LNG fuel supply system. Some shipyards in Korea have developed LNG fuelled ship and the engines and fuel supply system with LNG as a fuel have been installed on board.
In this study, the fuel gas supply system for gas fuelled ship has been studied and the operational characteristics such as gas pressure, gas temperature, flow quantity and tank capacity for four different operation cases using HYSYS simulation program on Econuri ship in operation with gas fuelled propulsion system has been investigated. And system stability for gas fuel supply ship has been assessed.