Wärtsilä Corporation has received an order to supply four 6L50DF dual-fuel engines to power a 75,000 m3 LNG (liquefied natural gas) carrier. Due for delivery in 2004, this new vessel is breaking away from traditional practices in the propulsion of LNG carriers. It will be the first LNG carrier to be powered by electric propulsion, and one of a few to have internal-combustion engines instead of the more usual steam turbine plant. The four dual-fuel engine generating sets, each developing 5700 kW at 514 rev/min, will meet all the ship’s propulsion and shipboard electrical requirements.

Compared with the alternative power plants, the Wärtsilä 50DF engines offer distinctive benefits in LNG carriers. Whilst making maximum use of the gas fuel (boil-off from the cargo of liquefied natural gas) to develop useful power, the high efficiency of these engines calls for a much lower overall fuel consumption and thus lower operating costs than the conventional steam turbine plant. The Wärtsilä 50DF engines also have much lower stack emissions than a steam plant. Their low NOx emissions are about one-tenth those of the equivalent diesel engines.

The combination of the engines’ low fuel consumption and their maximum use of natural gas means the 50DF engines also have low CO2 emissions. The 50DF engines can operate alternatively in gas mode or liquid fuel mode and engines are capable of switching over from gas to liquid fuel (marine diesel oil) automatically should the gas supply be interrupted, while continuing to deliver full power.