LPG or LNG engine on a tug boat - will it work?

Discussion in 'Inboards' started by yodani, Nov 10, 2014.

  1. AndySGray
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    AndySGray Senior Member

    The other benefit other than cost is it would be a much cleaner exhaust - no diesel odour, and you're not going to contaminate waterways like happens when re-fuelling on diesel - even a cupfull spilled leaves a sheen on the water for a hundred yards.

    This is a good foundation for eco-friendly marketing strategy.
     
  2. missinginaction
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    missinginaction Senior Member

    I'm retired but work part time for the transportation department of a large school system.

    We run a fleet of 72 passenger school busses, most diesel, but we do have about a dozen that run on propane. We got some sort of incentive from the government to take these propane busses.

    The good: They run clean.

    The bad: Not very efficient. I can get 7 or 8 miles per gallon out of diesel, more at constant speeds on the highway. With the propane units, it's more like 4 miles per gallon. Drivers complain that they are fueling them all the time.

    I would think in a boat that they'd burn a lot of fuel.

    MIA
     
  3. DuoPropper
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    DuoPropper New Member

    Check out Blue Gas Marine, they have been researching and implementing Natural Gas Marine Vessels for a while www.bluegasmarine.com
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    My understanding is the gas is less polluting in terms of CO2 emissions and the fine particulates associated with diesel.
     
  5. fredrosse
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    fredrosse USACE Steam

    Diesel vs. Propane vs. Natural Gas

    " I can get 7 or 8 miles per gallon out of diesel, more at constant speeds on the highway. With the propane units, it's more like 4 miles per gallon. Drivers complain that they are fueling them all the time."

    Makes prefect sense.

    Diesel Fuel = 140,000 BTU per gallon, Propane = 93,000 BTU per gallon. That implies, with equal engine efficiency, propane will consume 150% of the fuel gallons needed for Diesel Fuel. However the Diesel engine is significantly more efficient than the spark ignition (SI) engine, so things are actually even worse for the Propane.

    Comparing Carbon Emissions, Diesel Fuel is about 88% Carbon, while Propane is 82% Carbon, which makes the Propane look better than the Diesel for CO2 emissions, but considering the fuel consumption above, the Diesel Fuel comes out with far less CO2 emissions than the propane.

    Natural Gas is somewhat better, 75% Carbon in the fuel, but again, due to poor SI engine efficiency, CO2 emissions with natural gas fuel are no better than Diesel.
     
  6. gonzo
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    gonzo Senior Member

    Starters, alternators, switches, etc. are spark proof or shielded for gasoline engine applications. When adapting a diesel to LP or NG some care needs to be taken. Also, a bilge blower will be required.
     
  7. TANSL
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    TANSL Senior Member

    You mean, I guess, LPG and LNG or may be CNG.
    Yes, instead of bilge pumps you need bilge blowers. Where do they blow? (Perhaps it is more correct to speak of aspirations for gases).
    Before adapting a diesel engine to consume petroleum gas, I would try to put an engine designed directly for it. Am I saying nonsense?
     
  8. gonzo
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    gonzo Senior Member

    Yes. A bilge blower is necessary to exhaust the gasses that are denser than air. In the US and Canada there are large tax breaks for converting diesels. I think some other countries do too.
     
  9. TANSL
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    TANSL Senior Member

    I would talk to suck instead of blow.
    When you talk about the density of the gas, at what temperature and pressure is it measured?
    I don´t know energy policy in US or Canada. Is the gas, in these countries, cheaper than gasoline?
     
  10. gonzo
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    gonzo Senior Member

    Innuendo aside, they are called bilge blowers. Density is measured at standards conditions. Then each gas has a correction factor to compensate from the ideal gas equation. This can be used to calculated density from condensation to ignition or plasma forming. At all temperatures that a vessel can be operated, propane is denser than air.
     
  11. TANSL
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    TANSL Senior Member

    Except that propane is heavier than air, I do not understand anything else. By the way is propane what a combustion engine gas burns?.
    I would like you to examine the attached table. (I will not say anything, but you should study more before speaking)
     

    Attached Files:

  12. AndySGray
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    AndySGray Senior Member

    Caterpillar do a wide range of Gas (not gasolene) versions of the bigger diesel engines -

    e.g. the 12 and 16 cylinder D398 and D399 were also available as the G398 and G399 similarly the 3412 has a G3412

    These are not spark ignition but compression ignition as per their diesel analogues.
     
  13. whitepointer23

    whitepointer23 Previous Member

    Cng is the way to go . You get a lot more fuel in the same size space. I have seen a huge cat in a power house 20 years ago but that did have spark plugs to fire the gas. It was connected to the northwest gas pipeline in western australia.
     
  14. AndySGray
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    AndySGray Senior Member

    Please take care - the density quoted of 493.00 Kg per m3 is for liquid propane, I don't understand why you are comparing that to air?

    Propane Gas density (1.013 bar and 15 °C (59 °F)) : 1.8988 kg/m3 (still heavier than air)

    :?:
     

  15. TANSL
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    TANSL Senior Member

    You are right. It seems that I was wrong and I had the mistake that was attributing to Gonzo.
    How can propane liquid be lighter than gaseous ?. Am I understanding something wrong or I miss something ?. Thank you sincerely
     
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