LNG – fundamental principles and plant examples

1 -

TPG 4140 Natural Gas - 2013

LNG –

fundamental principles and plant examples

Jostein Pettersen

2 -

Outline

• Why LNG?

• What is LNG ?

• Block diagram

• Gas pre-treatment

• Gas liquefaction

− Some basics

− Process alternatives

• LNG storage and loading

• LNG transport

• LNG plant examples

− Focus on Hammerfest LNG / Snøhvit

3 -

Why produce LNG?

LNG is mainly produced for transportation purposes • When the gas market is far from the source of the natural gas it

can be more economical to transport the gas as LNG instead of in a natural

gas pipeline.

• LNG also offers greater flexibility than pipeline gas

4 -

LNG Density

Natural gas

LNG

1 m3 LNG corresponds

to ca 600 Sm3 natural gas

S = Standard state, 15C, 1 atm

At temperatures above -110 ºC

LNG vapour is lighter than air

LNG is lighter than water

LNG Density: 450 kg/m3

Water density: 1000 kg/m3

5 -

Types of liquefaction plants

• Base-load plants

Large plants which are directly based on a specific gas field development and are the main plants for handling the gas. A base-load plant has typically a production capacity of above 3 Mtpa (million tons per annum) of LNG (i.e. . The main world-wide LNG production capacity come from this type of plants

• Peak-shaving plants

Smaller plants that are connected to a gas network. During the period of the year when gas demand is low, natural gas is liquefied and LNG is stored. LNG is vaporized during short periods when gas demand is high. These plants have a relatively small liquefaction capacity (as 200 tons/day – ca 70 ktpa) and large storage and vaporization capacity (as 6000 tons/day). Especially in the US many such plants exist

• Small-scale plants

Small-scale plants are plants that are connected to a gas network for continuous LNG production in a smaller scale. The LNG is distributed by LNG trucks or small LNG carriers to various customers with a small to moderate need of energy or fuel. This type of LNG plants typically has a production capacity below 500 ktpa. In Norway and China several plants

within this category is in operation.

© 2013, IHS Inc. No portion of this presentation may be reproduced, reused, or otherwise distributed in any form without prior written consent.

LNG global base load liquefaction plants (2013)

6

Source: IHS CERA.

00406-6_2808

7 -

Block diagram

Gas processing

8 -

Simplified LNG plant block diagram

End

flash

HHC

Extraction

CH4/N2

Fuel

gas

Power

&

heat

(C5+) (C4 and C3)

(CO2 and H2S)

9 - 2010-09-26

Gas conditioning (pre-treatment)

• Acid Gas (CO2 and H2S) removal

− Acid gas causes corrosion, reduces heating value, and may freeze and create solids in

cryogenic process

− Typical requirements for LNG: Max 50 ppmv CO2, Max 4 ppmv H2S (ppmv - parts per million by volume)

− Usual process: aMDEA (Amine)

• Dehydration (water removal)

− Water will freeze in cryogenic process

− Typical requirement: Max 1 ppmw (weight) H2O (In some cases max 0.1 ppmw)

− Usual process: Adsorption (Mol sieve)

• Mercury removal

− Mercury can cause corrosion problems, especially in aluminium heat exchangers

− Requirement: Max 0.01 g/Nm3

− Usual process: Adsorption

10 -

Liquefaction process

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Example of natural gas path through liquefaction

pressure-enthalpy diagram (C1:89.7% C2:5,5% C3:1.8% N2:2.8%)

1

10

100

-900 -800 -700 -600 -500 -400 -300 -200 -100 0 100 200

Enthalpy [kJ/kg]

Pre

ssu

re [

bara

]

Crit

Phase

X=0.80/0.20

X=0.60/0.40

t=-200.0

t=-150.0

t=-100.0

t=-50.0

t=0.0

t=50.0

s=-4.000

s=-3.000

s=-2.000

s=-1.000

s=0.000

-200oC -150oC -100oC t = -50oC 0oC 50oC

Precooling Liquefaction Subcooling

Expansion

JT Throttling

End flash LNG

s = constant

12 -

Vapour pressure of pure fluids relevant for LNG

processes

1

10

100

-200 -150 -100 -50 0 50

Pre

ssu

ra(B

ara

)

Temp(C)

Refrigerant Vapour Pressure

N2

C1

C2

C3

NC4

Ethylene

LNG Range

N2 C1 Ethylene

C2

C3

n-C4

13 -

Liquefaction process licensors – Base load LNG plants (3+ Mtpa)

• Air Products and Chemicals Inc. (APCI)

− World leader since since the 1970s – ca 80 operating trains

− Propane Precooled Mixed Refrigerant (C3MR) process dominates

− AP-XTM (QatarGas II, III and IV, RasGas III: Six trains of 7.8 Mtpa each, Start up 2008)

• ConocoPhillips (Optimised) Cascade

− Alaska: Kenai (Operating since 1969!)

− Trinidad: Atlantic LNG - 4 trains

− Egypt: Idku – 2 trains

− Australia: Darwin LNG – 1 train

− Equatorial Guinea – 1 train

− Angola – 1 train

• Shell DMR – Double Mixed Refrigerant (Sakhalin, 2 x 4.8 Mtpa – start-up 2007) PMR (same as C3MR – but parallel MR circuits) – no references

• Linde MFC® Mixed Fluid Cascade Process (Snøhvit, 4.3 Mtpa – start up 2007)

Liquefaction process selection (Source: M. Nored, Apache Corp, 2013)

14 - 2010-09-26

C3MR

15 -

Simplified cascade process for natural gas

liquefaction

Methane

Ethylene

Propane

NG 12 °C -32 °C

1.4 bar 7 bar

-96 °C

1.4 bar 19 bar

LNG -155 °C

1.4 bar 45 bar

16 -

Temperature stages in cascade process

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Example of single-mix refrigerant cycle for natural

gas liquefaction (Prico cycle) (Max 1.2 Mtpa)

LNG

NG

5 bar

30 bar

12 °C

-155 °C

12 °C

-155 °C -155,5 °C

6,5 °C

99,8 °C

Composition:

NG Refrig

C1 0.897 0.360

C2 0.055 0.280

C3 0.018 0.110

nC4 0.001 0.150

N2 0.028 0.100

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Temperature – enthalpy diagram of Prico example

-200

-150

-100

-50

0

50

100

150

-1500 -1000 -500 0 500 1000 1500

Enthalpy, x 10^6 kJ/hr

Tem

pera

ture

, C

NG

Mixed refrigerant

NG 60 bar

LNG

NG

5 bar

30 bar

12 °C

-155 °C

12 °C

-155 °C -155,5 °C

6,5 °C

99,8 °C

Propane precooled mixed refrigerant (C3MR)

(Air Products and Chemicals Inc. - APCI) Illustration

from CB&I

19

Compressor driver selection (Source: M. Nored, Apache Corp, 2013)

20 - 2010-09-26

Industrial

gas turbines

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LNG storage and

loading

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LNG tank containment principles

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• Pre-stressed concrete outer walls

constructed by slipforming, sheathed

internally with a gas-tight layer of

nickel-alloyed steel.

• Inner tank in nickel-alloyed steel,

separated from the outer walls by a

layer of perlite - a variety of volcanic

obsidian highly suitable for insulation

• Extra layer of steel and insulation at

the transition between outer wall and

tank bottom to protect it against

strong local stresses should the

inner tank begin to leak.

• Heating cables under the tanks will

ensure that the ground remains

above 0°C in order to prevent frost

heaving.

Example of full-containment LNG tank design

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Typical storage and loading system

Loading arms connected

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26 -

LNG ships

27 -

LNG transportation – technical aspects

• LNG is transported at – 163 deg. C and at atmospheric pressure

• This low temperature require that the LNG is transported and handled with special

consideration, i.e.

− Completely separated from the ship’s hull

− LNG temperature must be maintained during the voyage – requiring efficient insulation

of the cargo tanks and handling of boil off gas (BOG)

− All cargo handling equipment must be able to operate at the low temperature of -163

deg. C

• Two basically different cargo containment systems are used:

− Self supported independent tanks (Moss Rosenberg spherical tanks, IHI SPB,

cylindrical tanks)

− Membrane tanks (Gaz Transport and Technigaz (GTT))

• Market share between the two concepts has been about. 50/50 - but the membrane concept

has been increasingly selected for recent newbuilding orders.

Cargo containment systems

Spherical tanks

(Moss Rosenberg) Membrane containment

28 -

29 - 2010-09-26

Plant examples:

- Trinidad – Atlantic LNG

- Darwin LNG (Australia)

- Yemen LNG

- Hammerfest LNG / Snøhvit

Atlantic LNG - Trinidad

30

Air cooled

condensers

Compressors

Jetty

Jetty

Cold boxes

(Heat exchangers) Source: www.comenco.it

Darwin LNG (Australia)

31

Source: www.lngfacts.org

Yemen LNG Water cooled

32

Sources:

www.yemenlng.com

www.yemenfox.net

www.nationalyemen.com

70°39′48″N

23°40′55″E

Facts:

Discovered: 1981 – 84

Water depth: 250 – 340 m

Distance to shore: 140 km

Gas in place (GIP): 317 GSm3

Recoverable reserves : 193 GSm3

Condensate: 34 MSm3

Statoil ASA (Operator) 36.79%

Petoro AS 30.00%

Total E&P Norge AS 18.40%

GDF Suez Norge AS 12.00%

RWE Dea Norge AS 2.81%

0 100 200 km

G:\T&P\ANT\MBM\NKG\Mapdata\NO\Norge_Oversikt\Lisenskart\Mxd\Statoil_Hydro_let_lic_tot_20070401vle.mxd

Snøhvit, Albatross

and Askeladd

Owners:

Original 2002

figures

2010-09-26

Hammerfest – Melkøya (May 2006)

2010-09-26

SNØHVIT Simplified overview

CO2 Injection

well

Production well

Seabed

Reservoir

Albatross

Production wells

CDU

Plem

Production wells

Production wells

Snøhvit

CO2 Injection well

Slug catcher Inlet facilities

Pretreatment

Fractionation

Carbon dioxide

MEG

recovery

Condensate production

LPG production

LNG production

Liquefaction cycle Subcooling cycle

Storage and loading:

LNG, LPG, condensate

Precooling cycle

Prepared by Petrolink as

Natural gas Cold Box

Nitrogen Removal Cold Box

Process substation

Electric power generation

Compressor area

Process area

2 3

1

HAMMERFEST LNG – Process area

Mixed Fluid Cascade (MFC®) Liquefaction process and

power/heat generation at Hammerfest

65 MW

65 MW

32 MW

NGL

2010-09-26

Why this very large extent of

prefabrication?

• Harsh weather conditions

• Remoteness – lack of necessary infrastructure

• Reduce the necessity of steel work at site

• Higher productivity at construction yard

• Reduce work at site in general -

of the total estimate of 15 million man-hours to

build the plant, 50 % is done at site.

Prefabrication and use of

large modules

Cold box

Process

plant

Prefabrication – LNG plant on a barge

Process systems on the barge Weight: 21.000 tonnes Height over deck: 60 m

Barge Weight: 10.000 tonnes Size: 154 x 54 x 9m

Blue Marlin and process barge in Cadiz….

Hammerfest – here we are!

In-docking of process-barge….

21 August 2007: Production start

13.09.07 First LNG to tank

26.09.07 First condensate cargo

20.10.07 First LNG cargo

47 - 2010-09-26

Arctic Shipping