The future of natural gas as a fuel in marine gas turbine for LNG carriers

Abstract

This paper discusses the suitability of using natural gas as a fuel for marine gas turbine electric propulsion (DFGE), utilizing natural boil-off gas and forced boil-off gas, as well as investigating its economical and environmental beneﬁts over other propulsion options. The benchmark ship chosen for this study has a capacity of 150,000 m³ and is powered by conventional steam propulsion. For this purpose a spreadsheet model was developed to determine the liquefied natural gas carrier operating costs for different propulsion options. This is in addition to a sensitivity analysis to study the effect of varying range, heavy fuel oil (HFO) and natural gas prices on ship operating cost. Recently, about 40% of the new orders shifted to slow speed diesel engines with re-liquefaction plant and dual fuel diesel electric propulsion. To date, marine gas turbines are not used in liquefied natural gas carriers.

It was found that using natural gas as a fuel with the proposed marine gas turbine cycle at current HFO and natural gas prices provides the highest cost saving for a distance less than 4000 nautical miles (NM). With the expected changes in fuel prices, the proposed cycle achieves cost saving of 3% per round trip, and this saving is directly proportional to increasing fuel prices, compared to other options.

Keywords

Natural gas marine gas turbine liquefied natural gas carriers

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