LNG and steam turbines

Discussion in 'Diesel Engines' started by lbdm, Dec 1, 2019.

  1. lbdm
    Joined: Jul 2019
    Posts: 9
    Likes: 0, Points: 1
    Location: BR

    lbdm Junior Member


    I could not find a more appropriated section!

    I've reading about LNG Carries switching from steam turbines to dual-fuel reciprocating engines since a while due to the economical advantages of adding HFO as a fuel etc.

    This is all quite clear but I couldn't find if in a 'Pure LNG' (or ever LNG + diesel) setup that advantage would hold, specially when using these more advanced/efficient steam turbines like MHI UST series.

    That said, in a context of a 'Pure LNG' large vessel using the most efficient available equipment, how the "steam turbine vs reciprocating engine" efficiency would be?

    PS. This is more a matter of curiosity.

    Thank you. :)
  2. fredrosse
    Joined: Jan 2005
    Posts: 433
    Likes: 76, Points: 38, Legacy Rep: 56
    Location: Philadelphia PA

    fredrosse USACE Steam

    Even with the most advanced steam cycles for marine propulsion, they are slightly lower overall efficiency than dual fuel reciprocating engines. Modern dual fuel recips, with very high pressure common rail fuel injection injecting a very small amount of fuel oil, are more efficient as well as avoiding the costs and complications of a marine steam plant.
  3. jehardiman
    Joined: Aug 2004
    Posts: 3,369
    Likes: 776, Points: 113, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Actually, I don't think it has anything at all to do with fuel efficiency of the main plant. Steam was generally selected in 1970s-1990s LNG construction because it could use low-cost boil-off while the cost of fuel oil was high. As dual fuel engines improved and the cost ratio between LNG and fuel oil changed, the economics of manning, lack of marine steam support in the industry, and the maintenance lay-days has forced steam into its little niche market. In terms of overall oil usage (which includes LO), steam still excels over reciprocating engines at the higher horsepowers, as well as having volumetric, weight, and arrangement advantages. However, the reduced manning, ability to do at sea maintenance, and less costly lay-days drive the over-all economics.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.