1. INTERTANKO,ATHENS 13th April
PROPULSION ALTERNATIVES, LNG By
Wilhelm Magelssen
Associate Members Committee

2. Propulsion power for LNG carriers
Engine Power (kW)
21 knots
40,000
20 knots
19 knots
30,000
20,000
Size (m3)
125,000
150,000
175,000
200,000
Source: MAN B&W

3. Thermal efficiencies
Source: MAN B&W

4. Handling of boil-off gas
Use as fuel in boilers
Accumulation during voyage
Use as fuel in gas engines
Use as fuel in gas turbines
Re-liquefaction
Burn in oxidizer (incinerator)

5. Means for disposal of boil-off gas
Steam turbine propulsion:
Two boilers + main and auxiliary condenser
Gas engine propulsion:
One oxidizer with redundant auxiliaries
Diesel engine propulsion:
One re-liquefaction unit + one oxidizer
Gas turbine propulsion:

6. Propulsion alternatives for LNG carriers
Steam turbine/dual fuel steam boilers
Dual fuel high pressure gas/diesel engine
Dual mode low pressure gas/diesel engines
Low pressure gas engines and diesel engines
Gas turbine & combined gas turbines/diesel engines
Diesel engine/boil-off re-liquefaction

7. Steam Turbine Propulsion - Simplified
Economiser
Flue gas uptake
Super-heater
Downcomers
Deareator
Furnace
Boiler casing
Water wall
Red gear
H.P
Shaft
Feed pumps
L.P
Main Condenser
Condensate pumps

8. DNV Rules for gas fuelled engine installations
The Rules define two concepts for safety against gas hazards in machinery spaces:
Inherently gas safe machinery space
The two-barrier concept as known from the IGC Code with an additional requirement for fitting excess flow shut-off in the gas supply
ESD protected machinery space
Single wall gas piping accepted. Applicable for low pressure gas engines only

9. Gas engines - piping
Low pressure gas engines have gas supply piping which is difficult to arrange with complete jacketing
There are no low pressure gas engines on the market at present having fully jacketed gas piping. However,Wärtsilä, is claiming that they are in the position in the near future

10. ESD Rule conditions (Emergency Shut Down)
Conditions for acceptance of ESD protected machinery space:
Gas supply pressure to be < 10 bar
Automatic de-energising of all sources of ignition on detecting of low concentration of gas and shut-off of gas supply to the engine room
Automatic shut-off of gas supply on loss of engine room ventilation, detection of fire or excess gas flow

11. ESD protected engine rooms
Because of the shut-down requirement for an ESD Protected engine room, the power generation for propulsion and manoeuvring must be divided between two or more engine rooms independent of each other

12. Dual Mode Gas/Diesel Engines

13. ESD protected engine rooms

14. Diesel engines + Re-liquefaction

15. Re-liquefaction plant for LNG boil-off
At present there is experiences only from one shipboard LNG re-liquefaction plant (NYK)
Power consumption is high (3,5-5,0 MW)
For LNG cargo tanks with permitted filling ratio of 99.5% (spherical) overfill protection arrangements should be considered

16. LNG carrier with oxidizer

17. Coastal LNG carrier: “Pioneer Knutsen”
delivered 2004, m3 cargo carrying capacity
2 x engines for gas fuel only + 2 diesel engines , - diesel electric propulsion
2 pods for main propulsion
redundant propulsion

18. Gas Turbines Rolls Royce MT30 36 MW flat rated @26C
42% thermal efficiency
201 g/kWhr on gas
Dual fuel capable

19. Steam Turbine Propulsion – Engine Room Arr’t
Cargo
Tank

20. Gas Engines/Electric Propulsion – Engine Room Arr’t+
Cargo
Tank ~ ~
Reduced length

21. General Arrangement – Gas Turbines

22. Gas emissions from LNG carriers
Fuel
NOx
SOx
CO2
Steam turbine
HFO + LNG
200
2.400
Low speed diesel
+ re-liquefaction
HFO
3.950
1.800
Dual fuel electric
LNG only
240
Gas turbines and COGES
850
Source: ALSTOM
Emissions: Tonnes / year / ship

23. Economics of LNG Re-liquefaction and Slow Speed Diesel Propulsion
Low Fuel Consumption for Propulsion, but power required by the re-liquefaction plant adds another 10 – 20 tons of heavy fuel oil
Unknown Initial Cost for the Re-liquefaction Plant, but Assumed to be Significant
High Power Requirements for Re-liquefaction, in the order of 3-5 MW at max. load

24. Economics of Dual Fuel Gas/Diesel Engines/Gas Turbines and Electric propulsion
Electric Propulsion Plants Require Higher Initial Costs
Gas/Diesel Engine Plants Have Lower Fuel Consumption - Thermal Efficiency 42-44% v.s % for Steam Propulsion
Gas/Diesel Engines Have Higher Maintenance Costs
Fuel Cost Savings for Gas/Diesel Plants Increase With Higher Fuel Oil Price

25. LNG carrier propulsion - Conclusion
The traditional steam turbine propulsion has served LNG carriers well for over 30 years
Future operating modes will require flexibility and efficient propulsion plants able to accommodate different ship speeds
Operating economy and environmental issues have to be considered carefully when selecting propulsion power plant
Safety and redundancy are important features required from the propulsion power plant

26. Offshore re-gasification and discharge

27. Experienced personnel, - a serious challenge !
.. insufficient supply of competent people may have a knock-on effect on other shipping sectors ?

28. LNG Trade in cold Climate
Cold climate: Is this the future environment for LNG carriers? What kind of impact will this have on the Propulsion system?

29. End of Presentation
Thank you!