6. Economic Design of Small Scale LNG Tankers and Terminals. Economic Design of Small Scale... ·...

Economic Design of Small Scale LNG Tankers and Terminals

Björn MunkoTGE Gas Engineering

LNG Conference 2

Trends in LNG shipping

� Larger LNG carriers for “classical” LNG transportation market (up to 270,000 m³)

� Smaller LNG carriers for new LNG transportation market

�Clean fuel power plants for remote industrial areas or islands

�Regions without pipeline grid (e. g. Norwegian coast)

�Short sailing times in relation to LNG consumption

�Design requirement for partial filling

LNG Conference 3


� Smaller LNG carriers

�A Japanese yard is building a 19,000 m³ vessel with 3 spherical tanks (delivery: 2007).

�An Australian company is developing projects of up to 30,000 m³ transport capacity.

�Standard designs for LNG ships (spherical aluminium tanks or membrane tanks) are expensive � economics for such niche markets have to be improved.

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� Very Small LNG carriers (for coastal trade)

�First very small ship (1,000 m³) for Norwegian coast

delivered in 2004 (stainless steel tanks, electric propulsion)

�Two LNG ships of 2,500 m³ delivered in 2003/5 for Japanese coast (cylindrical aluminium tanks)

�Anthony Veder (NL) is building a 7,500 m³

LNG/Ethylene carrier for coastal transport in Norway

(vessel design and gas plant supplied by TGE)

LNG Conference 5

Design approach to small LNG terminals

� Market: Small consumption (islands, remote industrial area)

� Utilizing the know-how from design of large LNG terminals and of small ethylene terminals

� Tank concept depends on throughput and storage capacity

�above abt. 10,000 m³: flat bottom tank (like large terminals)

o containment type depends on local rules and safetyrequirements

�up to abt. 10,000 m³: pressure vessel type tanks

� BOG handling, tank pressure depends on send-out conditions

� LNG re-gasification concept depends on capacities and local

conditions

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Example: 30,000 m³ flat bottom tank:

built in Urumqi/China (single containment)

LNG Conference 7

single containment type: inner tank for containing the product, outer container for retaining and protecting the insulation only

Bund wall

elevated concrete base

base insulation

inner tank

insulated suspended deck

loose filled insulation

outer shell ( not able to contain liquid )

roof

concrete foundation with bottom heater

base insulation

inner tank wall

external insulation with weather barrier

inner roof

bund wall

inner tank bottom

Containment types acc. BS7777

LNG Conference 8

double containment type: inner tank for containing the product, outer container for retaining the insulation and in case of inner tank failure the product liquid ( but not the vapour )


base insulation

inner tank



outer shell ( not able to contain liquid )

roof


base insulation

inner tank wall

external insulation with weather barrier

inner roof

inner tank bottom

rain cover

prestressedconcrete outer tankwall

rain cover

outer tankshell( able tocontainthe liquid )


LNG Conference 9

full containment type: inner tank for containing the product, outer container for retaining the insulation and in case of inner tank failure both the product liquid and the vapour


base insulation

inner tank


insulation at inside outer tank

outer tank wall liner

roof


base insulation

inner tank wall

inner roof

inner tank bottom

outer tankshellor prestressedconcrete wallwith liner

prestressed concrete outer tank

outer roof


wall insulation at inner sideof outer tank ( or loose filledinsulation )


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Pressure vesesel type storage tanks:

Example: 5 x 1,200 m³ ethylene storage (China)

LNG Conference 11

Pressure vesesel type storage tanks:

� Ethylene storage built in China:� Inner Diameter: 4.6 m

�Length TL – TL: 75 m

�Volume: 5 x 1,200 cbm

�Material: 5% Nickel steel

� Insulation: foamglas

�Design pressure: 23 bar g

� LNG storage:�Material: stainless steel (AISI 304)

� Insulation: foamglas or vacuum

�Design pressure: depending on send-out situation

LNG Conference 12

LNG re-gasification equipment

� Preferred equipment depends on required capacitiesand local ambient condition (air, sea water):

� Open rack vaporizer (ORV)

� using sea water as heat source

� Submerged combustion vaporizer (SCV)

� using gas energy

� Ambient air vaporizer (AAV)

� using ambient air as heat source

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Open Rack Vaporizer

� low operating cost: water

pumping energy

� higher investment costs� need of sea water intake

� min. temperature for seawater required

LNG Conference 14

Submerged combustion vaporizer

� lower investment costs

� need of dedicated fuel gas installation

� high operating cost by gas consumption( ~ 1.5% of gas send-out)

LNG Conference 15

Ambient air vaporizer

� moderate investment costs

� need large installation areas

� dry ambient air preferred

� application currently under investigation (qualification program) for larger capacities

LNG Conference 16

TGE’s design approach to small LNG carriers

� Objective: minimize the CAPEX

� Utilize the know-how from design of Ethylene carriers

�Ethylene ships: TGE‘s market share for delivery of gas handling systems and cargo tanks is more than 80%

�Actual order book: 32 ethylene carriers

� Maximize operation flexibility for a combined

LNG/Ethylene/LPG-carrier

� Main questions:

�Cargo tank design

�Boil-off gas handling / propulsion system

LNG Conference 17

Types of cargo tanks for gas carriers

� (Internal insulation tanks)

� (Integral tanks)

� (Semi-membrane tanks: very few applications)

� Membrane tanks

� Independent tanks

�(Type A)

�Type B

�Type C

LNG Conference 18

TGE’s design approach: independent Type C tanks

�self-supporting pressure vessel

�cylindrical or bilobe with outside insulation

�no secondary barrier required

�no restriction concerning partial filling

LNG Conference 19

Cargo tanks for 22,000 m³ Ethylene-carrier

� 5,700 m³ (4 tanks)

� 4.7 bar g

� 480 t

� 5% Nickel steel

LNG Conference 20

Type C tanks for LNG

� Ship capacity below 15,000 m³

�Cylindrical tank design

o 2 tank design up to abt. 10,000 m³

o 3 tank design up to abt. 15,000 m³

� Ship capacity above 15,000 m³

�Bilobe tank design

o 3 tank design up to 25,000 m³

o 4 tank design up to 35,000 m³ (or even 40,000 m³)

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� Tank design temperature: -163°C

� Tank material:

� (Aluminium)

� (9% Ni-steel)

� SS AISI 304L

LNG Conference 22


� Ship design example: 30,000 m³ capacity:

�4 Bilobe tanks each abt. 7,500 m³ capacity

�Min. design pressure @ density 500 kg/m³:

o AISI 304L: 2.74 bar g

�Tank weights:

o AISI 304L: abt. 530 tons

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30,000 m³ LNG-Carrier

lbp = 175.2 m

b = 27.6 m

d = 8.8 m

speed = 17.5 kn

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� Design constraints for LNG compared to Ethylene:

�Higher material shrinkage due to:

o Larger delta T during cooling down

o Higher material shrinkage factor for AISI 304L

�Problem especially for bi-lobe tanks:for 15 m diameter tanks the shrinkage is 35 mm (304L)

�Detailed design review and complete re-design of supports necessary (displacement and stress analysis, temperature profiles)!

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� Design appraisal by a classification society

�FEM analysis of tank shell, supports and shipside steel structure for different loading cases

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Tank insulation for LNG

� Tank insulation for Ethylene:

�Typical Polystyrene panels glued to tank surface with

abt. 230 mm thickness

� Tank insulation for LNG application

�Same insulation type may be applied (spherical LNG

tanks use same technology)

�Insulation thickness of 300 mm (boil-off rate abt. 0.35 –

0.45 %/day)

�Design details modified (shrinkage, stress)

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Type C tanks for LNG – new design

� Concept approval certificate already issued by Class

� Patent pending

� 30 … 35,000 m³ designs have been discussed for a specific project with three shipyards on the basis of confidentiality agreements concerning design details

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Boil-off gas handling / propulsion system

Alternatives for boil-off gas handling considering typically short voyages and small BOG quantities:

a) Burn the BOG in a thermal oxidiser (combustor)

b) Accept a pressure increase during voyage, provided that receiving terminal can accept it

c) Utilize BOG for propulsion (electric power production)

d) Reliquefaction

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Boil-off gas handling

b) Pressure increase

0

0,5

1

1,5

2

2,5

3

3,5

4

0 10 20 30 40 50 60

Sailing Time [days]

Pre

ssure

[bar g]

Basic LNG

Composition

N2:2%

CO2:0%

C1:89%

C2:5,5%

C3:2,5%

C4:1%Tank Volume: 30.000 m³

Insulation: 300 mm

Polystyrene

Initial pressure: 140 mbar g

9% Ni

SS 304L

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c) Utilize BOG for propulsion

� Owner: Anthony Veder, NL (design and gas plant supplied by TGE)

� Project: Coastal transport in Norway

�LNG to be used as fuel

�HFO to be used as fuel for transportation of other cargoes

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c) Utilize BOG for propulsion

� 7,500 m³ LNG/LEG/LPG carrier for Anthony Veder

Electric propulsion (Gas, HFO):

�HFO generator sets: 2 x 3,685 kW

�Gas generator sets: 2 x 2,280 kW

�thrusters for optimum manoeuvrability

GAS

GAS

HFO

HFO

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d) Reliquefaction

� Electric propulsion (utilize LNG and HFO as fuel) �high CAPEX

� Conventional slow speed diesel-mechanic (HFO) �BOG reliquefaction needed (CAPEX !), if pressure increase is not an option

� Alternative concepts based on mature technology:

�pure LNG carriers: nitrogen system (Brayton cycle)

�combined LNG/LEG carrier: utilize cascade technology from Ethylene ships (under development)

LNG Conference 33

Combined LNG/Ethylene/LPG Carrier

� Changing grade from LNG to Ethylene or LPG

requires tank warming up

� Changing grade is time consuming (especially from

LNG to LPG)

� Cargo contamination may be an issue (for some

cargoes visual inspection may be required)

� � Frequent grade changes are not economic

LNG Conference 34

Combined LNG/Ethylene/LPG Carrier

� Small LNG ships with type C cargo tanks can easily be “upgraded” to combined gas carriers (installation of

BOG reliquefaction for Ethylene)

� LNG transportation in smaller quantities is not a mature

market

� Combined LNG/Ethylene/LPG carriers – like 7,500 m³

vessel – meet the demands of a developing market

� increase operating flexibility

�seasonal LNG transportation demands

�up to 35,000 m³

LNG Conference 35

Economics of small LNG carriers

� CAPEX:

�Little changes for ship‘s hull construction (steel grade of tank supports)

�Tanks and cargo handling system more expensive than for Ethylene carriers

�TGE estimation shows an overall CAPEX abt. 10 – 15 % above the corresponding Ethylene-carrier price, depending BOG handling concept

LNG Conference 36

Conclusion

� Target market: small gas consumers without access to a pipeline grid

� TGE’s design approach with type C tanks is based in vast experience with Ethylene carriers

� The combined 7,500 m³ LNG/Ethylene/LPG carrier demonstrates that TGE’s approach meets the requirements of this developing market

� Small LNG carriers can be economical with type C cargo tanks up to 35,000 m³ capacity

� TGE has received a „Concept Approval“ of a modified tank design with a classification society

� A patent is pending for the new tank design

Thank you for your attention!

For any questions please contact TGE:

email: [email protected]: +49-228-60448-217

6. Economic Design of Small Scale LNG Tankers and Terminals. Economic Design of Small Scale... ·...

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