Slide 1

INTERTANKO,ATHENS 13th April

PROPULSION ALTERNATIVES, LNG

By

Wilhelm Magelssen Associate Members Committee

Slide 2

Propulsion power for LNG carriers

20,000

30,000

40,000

125,000 150,000 175,000 200,000Size (m3)

Engine Power (kW)

21 knots

20 knots

19 knots

Source: MAN B&W

Slide 3

Thermal efficiencies

35

30

40

25

50

45

M edium speeddiesel engine

20

Capacity (M W )501 10

55Therm al efficiencies %

Gas turbine

Com bined cyclegas turbine

Steam turbine

Low speed diesel engine

5

LNG carrier

Source: MAN B&W

Slide 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)

Slide 5

Means for disposal of boil-off gas

Steam turbine propulsion:• Two boilers + main and auxiliary condenserGas engine propulsion:• One oxidizer with redundant auxiliariesDiesel engine propulsion:• One re-liquefaction unit + one oxidizerGas turbine propulsion:• One oxidizer with redundant auxiliaries

Slide 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

Slide 7

Steam Turbine Propulsion - Simplified

Furnace

Condensate pumps

Main Condenser

Red gearH.P

L.P ShaftFeed pumps

Deareator

Super-heater

Economiser Flue gas uptake

Downcomers

Boiler casing

Water wall

Slide 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 spaceSingle wall gas piping accepted. Applicable for low pressure gas engines only

Slide 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

Slide 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

Slide 11

ESD protected engine rooms

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

Slide 12

Dual Mode Gas/Diesel Engines

Slide 13

ESD protected engine rooms

Slide 14

Diesel engines + Re-liquefaction

BOG FEED

VENT

TO TANKS

2 3

1 E

COOLINGWATER

-200

-100

0

+100

-200

-100

0

+100

-200

-100

0

+100

-200

-100

0

+100

MAXMIN

-200

-100

0

+100

MAXMIN

-200

-100

0

+100

-200

-100

0

+100

-200

-100

0

+100

-200

-100

0

+100

RESE

RVOI

R

BY -PASS

SUCTION THROTTLE

NITR

OGE

N

RECYCLING

Slide 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

Slide 16

LNG carrier with oxidizer

Slide 17

Coastal LNG carrier: “Pioneer Knutsen”

delivered 2004, 1100 m3 cargo carrying capacity

2 x engines for gas fuel only + 2 diesel engines , - diesel electric propulsion

2 pods for main propulsion

redundant propulsion

Slide 18

Gas Turbines

• Rolls Royce MT30

– 36 MW flat rated @26C– 42% thermal efficiency– 201 g/kWhr on gas– Dual fuel capable

Slide 19

CargoTank

Steam Turbine Propulsion – Engine Room Arr’t

Slide 20

CargoTank

Gas Engines/Electric Propulsion – Engine Room Arr’t

+~

~

Reduced length

Slide 21

General Arrangement – Gas Turbines

Slide 22

Gas emissions from LNG carriers

Fuel NOx SOx CO2

Steam turbine HFO + LNG 200 2.400 180.000

Low speed diesel+ re-liquefaction

HFO 3.950 1.800 120.000

Dual fuel electric LNG only 240 0 100.000

Gas turbines and COGES LNG only 850 0 108.000

Source: ALSTOM Emissions: Tonnes / year / ship

Slide 23

Economics of LNG Re-liquefaction andSlow 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

Slide 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. 31-33% for Steam Propulsion

• Gas/Diesel Engines Have Higher Maintenance Costs

• Fuel Cost Savings for Gas/Diesel Plants Increase With Higher Fuel Oil Price

Slide 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

Slide 26

Offshore re-gasification and discharge

Slide 27

Experienced personnel, - a serious challenge !

.. insufficient supply of competent people may have a knock-on effect on other shipping sectors ?

Slide 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?

Slide 29

End of Presentation

Thank you!