Natural Gas Liquefaction - NTNUfolk.ntnu.no/cadorao/courses/TEP10/files/TEP10 Natural Gas... ·...

1

Classification: Internal Status: Draft

Natural Gas Liquefaction

TEP 10 – Gas Processing and LNG – Fall 2008

Jostein Pettersen

2

Simplified LNG plant block diagram

Endflash

HHCExtraction

CH4/N2

Fuelgas

Power&

heat

2

3

Hammerfest LNG plant - block flow diagram

Slugcatcher

Inlet facilities/Metering

CO2removal

De-hydration

Mercuryremoval

Natural gasliquefaction

LPG Storage

CondensateStorage

MEGRecovery

Condensatetreatment

CO2 dryingand

recompressionNitrogenremoval

Fractionation(RefrigerantMake-up)

Fuel gassystem

C1 / C2 / C3 Refrig. Make-up

CO2 reinjection(to pipeline)

Feed frompipeline

Lean MEG(to pipeline)

LNGStorage

LNGStorage

N2 to atm.

UtilitySystems

FlareFacilities

Controlroom

4

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)

• Dehydration (water removal)

– Water will freeze in cryogenic process

– Typical requirement: Max 1 ppmw (weight) H2O

• Mercury removal

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

– Requirement: Max 0.01 μg/Nm3

3

5

Gas quality constraints for gas liquefaction

Source: Advantica

6

Natural gas and LNG compositionDesign data for Hammerfest LNG plant

Component Slug catcher Liquefaction plant LNGNitrogen 2,51 2,67 1,10Methane 80,02 86,34 91,92Ethane 4,97 6,54 5,59Propane 2,50 2,68 1,11Butane 1,22 1,23 0,23Pentane 0,58 0,35 0,04C6+ 1,62 0,15 0Aromatics 0,23 0,02 0CO2 5,20 0,005 0,005H2S 0,0005 0 0Water 0,81 0 0MEG 0,35 0 0Total 100 100 100

Composition mol %

4

7

Example of ageing/weathering during LNG transport

40.25

40.3

40.35

40.4

40.45

40.5

40.55

0 2 4 6 8 10 12 14 16

Day

GC

V (M

J/Sm

³)

Calculated ageing effect during the voyage from Melkøya to USA, Cove Point

Calculated according to ISO 6976 – based on real gas

8

Nitrogen RemovalNitrogen need to be removed from LNG in order to meet

•Storage and transport specification (Roll Over)

•Fuel gas requirements

•LNG Heating Value requirements

Systems to handle N2 will vary in complexity, from simple end flash drums, to complex distillation columns systems for separating N2 from the LNG

5

9

Example of end flash with LNG turbineFlash gas (containing nitrogen) used as fuel gas

°

LNG EXPANDER

ENDFLASH

M

HP FUEL GAS

LNG RUNDOWN

Gen Set

Gen Set°

LNG EXPANDER

ENDFLASH

M

HP FUEL GAS

LNG RUNDOWN

Gen Set

Gen Set

High-pressure LNGfrom cryogenic HE

LNG at near-atmospheric pressurepumped to storage tank

10

Sulphurrecovcery

Utilities

Slugcatcher

Condensatestabilization

Utility powerand steam

Qatargas LNG plant layout

6

11

Qatargas

CO2absorber

Gas turbinesand

compressors

MCR Heat Exchanger CCR

12

Air cooledcondenser

s

Atlantic LNG – Trinidad(Air cooled)

Compressors

Jetty

Jetty

Cold boxes(Heat exchangers)

7


LAYOUT - HAMMERFEST LNG PLANT

Slug catcher

HP flare

LP flare Camp area

Condensate storagetank

LNG storagetanks

Product jettyLPG storage tank

Storage & loadingsubstationN2 cold box

NG Cold boxProcesssubstation

Electrical power generation

Compression area, barge

Process area, barge

Construction jetty

Subsea roadtunnel

Administration building / controlroom

Sea water outlet /sea water inletHolding basin / waste water

treatmentUtilitysubstationMDEA storage / fuel gas

Compressed air and inert gas facilitiesLandfall

Offshore utility substationMEG process

areaMEG substationMEG storage tank

areaHot oil and chemical storage

tanksPig receiver

Grid substation

Area 2 Area 3Area 1

14

Gas liquefaction process - idealExample: Natural gas at 60 bar, 10oC ambient temperature

-270

-230

-190

-150

-110

-70

-30

10

50

-6 -4 -2 0Entropy, kJ/(kgK)

Tem

pera

ture

, °C

-273

W

Q

p=1.3 bar

20 bar

60100• Heat is removed as the gas is

cooled at gliding temperature

• Ambient temperature 10oC

• Heat removed during liquefaction

(Q), and ideal work (W), are shown

as areas

• Gas pressure has a large influence

on work

• Ideal work of liquefaction: Natural gas

at 60 bar: 0.11 kWh/kg

(0.8 % of Lower Heating Value)

8

15

Energy (fuel gas) use for liquefaction

• Liquefaction process 2nd law(exergy) efficiency typicallyaround 50%

• Typical fuel use 5-10% of feed

• Ambient temperature and feedgas pressure has large effect

0

5

10

15

20

0 20 40 60 80 100

Exergy efficiency of liquefaction cycle, %

Ener

gy in

put a

s %

of L

HV

30 %50 %100 %

Efficiency of power generation:

Hammerfest

16

Natural gas cooling• Cooling of natural gas stream occurs

over large temperature span

• Heat must be removed from natural gas stream at varying temperature

• Temperature of evaporating refrigerantmust be as high as possible to reducepower need for heat pumping

• Close match between NG temperaturecurve and refrigerant temperature canbe achieved by

Heat transferred

T, oC

10oC

-160oC

NG

Ambient temperature (air / sea water)

Pumping of heat

- using many stages ofevaporation temperature(cascade process), or

- using a refrigerant thatevaporates at glidingtemperature (mixed refrigerantprocess)

9

17

0,01

0,1

1

10

-250 -150 -50 50 150

Temperature, deg C∆W

/∆Q

- C

hang

e in

wor

k (M

W) p

er M

W

heat

tran

sfer

red,

for 1

K d

elta

T

Temperature difference in heat exchangers is increasinglyimportant at lower temperatures

• Sub-ambient temperature

• ∆W = extra power input needed to compensate for heat transfer acrossa temperature difference of ∆T = 1 K

• ∆W grows more than exponentiallyas temperature level T is reduced

Ambient temp 10oC

Reduced workoutput

Increased workinput

To

T

S

∆T = 1 K

∆Q

∆SC

∆SH

∆W = T0 ∆S = To(∆SC - ∆SH)• Consequence: ∆T need to be

reduced as much as possible at low temperatures

18

Natural gas path through liquefactionpressure-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]

Pres

sure

[bar

a]

-200oC -150oC -100oC -50oC 0oC 50oC

PrecoolingLiquefactionSubcooling

Expansion

JT Throttling

End flash LNG

10

19

Simple vapour compression refrigeration system –Flow circuit

Fluid to be cooled

Heat sink(Air/water) Condenser

Evaporator

Evaporatingrefrigerant

Condensing refrigerant

High pressure

Low pressure

Compressor

Expansion valve

20

T [oC]: -60 -20 0 20 40 60 80 100-40

0,1

1,0

10,0

100,0

-700 -600 -500 -400 -300 -200 -100 0 100 200 300Enthalpy [kJ/kg]

Pres

sure

[bar

a]

Refrigeration cycle in ph-coordinates (propane)

1

2

3

4

4

2

1

3

Evaporation at -30oC Condensation at 30oC 40oC at Compressor

discharge

Evaporatingtemperature –30oC

Condensingtemperature 30oC

11

21

-80

-60

-40

-20

0

20

40

60

80

100

120

-700 -600 -500 -400 -300 -200 -100 0 100 200 300Enthalpy [kJ/kg]

Tem

pera

ture

[°C

]

Refrigeration cycle in Th-coordinates (propane)

p = 1 bar

2 bar

10

15 20

25

22

Vapour pressure of pure fluids relevant for LNG processes

Refrigerant Vapour Pressure

1

10

100

-200 -150 -100 -50 0 50

Temp(C)

Pres

sura

(Bar

a)

LNG Range

N2

C1 Ethylene

CO2

C2

C3

n-C4

12

23

Data for some relevant fluids

NBP dhNBP

[°C] [kg/kJ] [°C] [bara] [°C] [bara]Nitrogen N2 -195,75 202,678 -210,0 0,125 -146,95 33,944Methane CH4 -161,45 522,080 -182,5 0,117 -82,55 46,002Ethylene C2H4 -103,71 487,132 -169,2 0,0012 9,20 50,359

Carbon dioxide CO2 -78,45 392,780 -56,6 5,170 31,05 73,765Ethane C2H6 -88,65 496,999 -182,8 0,000013 32,25 48,839Propane C3H8 -42,07 431,517 -187,6 1,960E-09 96,67 42,496n-Butane C4H10 -0,45 389,746 -138,3 6,740E-06 152,05 37,997

Critical pointTriple point

Normal boiling point, at 1.013 bara

Enthalpy of evaporation at NBP

Normal sublimation temperature (NBP lower than triple point temp)

[kJ/kg]

24

Phase envelope(for a given composition)

Critical

Cricondenbar

Cricondentherm

Bubblepoint Curve

Dew Point Curve

QualityLines

Temperature

Pres

sure 75%

50%

25%

Bubble Point Curve Boundary between liquid phase and 2-phase region

Dew Point Curve Boundary between gas phase and 2-phase region.

Critical Point Location where bubble point and dew-point curves meet.

Cricondentherm Highest T in phase envelope.

Cricondenbar Highest P in phase envelope.

Quality Lines Lines of constant volumetric or molar percentage of a phase.

13

25

Tx-diagram example:Cooling C2/C3 at a constant pressure of 5 bara

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

5

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100Weight-% Ethane

Tem

pera

ture

[°C

]

Bubble Dew

Temp/concentrationof first liquidcondensed

Temp/concentrationof last vapour to condense

Equilibrium betweenliquid and vapour

ΔT

Two-phase

Superheatedvapour

Subcooledliquid

(Saturated)

26

Mixed-fluid process in Th-coordinates(50/50 w-% C2/C3)

-80

-60

-40

-20

0

20

40

60

80

100

120

-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300Enthalpy [kJ/kg]

Tem

pera

ture

[°C

]

p = 1 bar

2 bar

10

15 20

25

14

27

Process licensors – Base load LNG plants• Air Products and Chemicals Inc (APCI)

– World leader since since the 1970s– More than 130 Mtpa installed, 50 Mtpa under construction, more than 60 operating trains

– C3MR process ( < 60 trains)

– AP-XTM Hybrid (Qatar Gas II, 2 x 7.8 Mtpa, Start up 2008 and 2009)

• ConocoPhillips (Optimised) Cascade– Trinidad: Atlantic LNG - 4 trains

– Egypt: Idku

– Alaska: Kenai (Operating since 1969!)

– Australia: Darwin LNG

– Equatorial Guinea

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

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

• Axens Liquefin™ (No references)

Mtpa = Million tonnes per year

28

Cascade process for natural gas liquefaction

MethaneEthylenePropane

NG12 °C-32 °C

1.4 bar 7 bar

-96 °C

1.4 bar 19 bar

LNG -155 °C

1.4 bar 45 bar

15

29

Mixed-fluid process in Th-coordinates(50/50 w-% C2/C3)

-80

-60

-40

-20

0

20

40

60

80

100

120

-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300Enthalpy [kJ/kg]

Tem

pera

ture

[°C

]

p = 1 bar

2 bar

10

15 20

25

30

Principles of mixed refrigerant cycle(Prico single-mix cycle)

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

16

31

Temperature - Enthalpy

-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

Mixed refrigerant dew point line

Mixed refrigerant bubble point line

NG bubble point line

NG dew point line

Mixed refrigerant 30 bar

Mixed refrigerant 5 bar

NG 60 bar

32

Mixed Fluid Cascade (MFC®) process (Linde-Statoil)

• Three mixed refrigerant circuits

– Precooling (Mainly: C2, C3)

– Liquefaction (Mainly: C1, C2, C3)

– Subcooling (Mainly: N2, C1, C2)

• Cascade connection of the circuits

• Precooling in two (sometimes three) stages

• No fractionation of the mixed refrigerant flows

• Expander on subcooling cycle

X1

NG

LNG

CW1

C2

CW2

E1A

E1B

E2

E3

PrePre--coolingcoolingSectionSection

LiquefactionLiquefactionSectionSection

SubSub--coolingcoolingSectionSection

CW3A/B

C1

C3G

17

33

Heavy hydrocarbon extractionScrubber column (Snøhvit)

• Natural gas liquids (NGL/LPG) are formed during precooling, and can/must be separated from the gas stream

• Propane and butane are valuable products

• Extraction process is needed to reach lean gas specifications, LNG specs demand that C3 and C4 is removed

• A relatively simple solution is to use a scrubber columnthat separates out liquid components which are formedduring cooling of the natural gas

• Some LPG is fractionated to give pure C1, C2 and C3 for refrigerant make-up

LPG FractionationRefrigerant make-up

Precooling

-25oC -50oC

Scrubber column

Natural gasfrom pre-processing

34Feedgas from

pre-processing

N2/CH4 tonitrogenremoval

CH4 fromnitrogenremoval

LNG

LPG FractionationRefrigerant make-up

Precooling Subcooling

Nat

ural

Gas

Liq

uefa

ctio

nC

ircui

ting

Lique-faction

18

35

Natural gas circuiting

36

Composite temperature curves - HammerfestOverall Heat / Temperature Diagram for Cold Equipment in System 25

Snøhvit A Plant Feed Stock

110 130 150 170 190 210 230 250 270 2900

40

80

120

160

200

240

280

320

360

Temperature [K]

Hea

t [M

W]

Hot (sum) Cold (sum)

Precooling Refrigerant

Lique-faction Refri-gerant

Subcooling Refrigerant

Reboi ler

19

37

Precooling cicruit

38

25-HA-101

25-HG-101 A-D

25-V

D-1

07

25-PA-102 A/B

25-HA-105

25-PA-103 A/B

25-V

E-10

1

25-HG-105

25-HG-102 A-F

25-HA-112

G

G

LCM

PCM

SC

I

SC

IIM

25-HA-111

25-V

D-1

02

25-V

D-1

01

25-HX-101

25-HX-102

25-KA-101

25-KA-102

25-HA-114

25-HA-104

25-V

D-1

06

25-V

D-1

05

25-V

E-10

2

25-KA-103

25-HX-103

25-PA-101A/B

25-EG-102

25-EG-101

25-CT-102

25-CT-101

25-HA-113

21

26

42

27

42

27

25-V

D-1

07A

25-V

D-1

09

26C

42

26

25-V

D-1

10

25-V

D-1

1125

-VD

-112

SW SW

SW

SW

SW

HO

SW

26D

26C

27A

27A

46A

46A

27A

26B

26A

27A

26B

OVERVIEW

25-144

25-1

54

25-155

25-1

56

21-102 25-138

25-139

25-153

25-1

52

25-2

12

25-15125-150

26-205

25-215 25-149

25-149.1

25-1

4825-2

25

25-141

25-1

42

25-219

25-144.1

25-157

25-156.1 25-156.2

25-162

25-161

25-158

25-163

25-1

65

27-130

25-1

66

25-167

27-131

25-1

59

25-160

25-196.4

25-2

05

25-1

02

25-1

96

25-1

96.2

25-168

25-1

96.1

25-1

96.3

25-2

0025

-201

25-263.1

25-263

25-1

95

25-2

02

25-103

25-263.2

25-198

25-193

25-122.1

25-1

21.2

25-1

21.1

25-209

25-1

20

25-1

21

25-2

07 25-2

10

25-122.2

25-123

25-124

25-181

25-2

81.1

25-253

25-2

5425

-255

25-2

5625

-257

25-125

25-1

26

25-2

06

25-133

25-133.125-133.2

25-134

25-1

3525

-136

25-177

25-140

25-140.1 25-140.2

25-137

25-258

25-2

5925

-260

25-2

61

25-1

27

25-2

62

25-1

28

25-179

25-211

25-1

29

25-1

30

25-1

31

25-1

32

25-1

32.1

25-132.2

25-1

71

25-172

25-1

73

25-104

25-251

25-247

25-24825-252

25-2

49

25-264

25-26525-269

25-2

70

25-272

25-2

71

25-2

73

25-274

25-277

25-278 25-279

25-266

26-1

84

26-1

12

25-112

25-1

08

25-109

25-801

25-805

25-8

04

25-802

25-8

03

25-110

26D

26-1

7526

-180

25-2

80

25-115

26A26-139

26-174

25-183

25-116

25-810

25-808

25-806

25-809

25-117

25-2

23

25-105

25-106

25-815

25-114

25-81225-813

25-2

68

25-111

25-1

13

25-820

25-816

25-819

25-114

25-818

25-118

25-117

26-1

02

25-189

26-1

40

42-104 25-169

25-143

MIN. FLOW LINE

ANTISURGE

START UP RECYCLE

25-807

25-817

25-8

11

25-1

90

MIN

. FLO

W

25-203 25-202ANTISURGE

MIN

. FLO

W

25-133

25-122

MIN

. FLO

W

ANTI

SU

RG

E

ANTISURGE

START-UP LINE

25-V

D-1

16

25-V

D-1

15

25-VD-104

25-VD-114

25-VD-103

25-HG-104

25-HG-103 A/B

25-FV-1725A

25-FV-1203

25-F

V-14

51

25-FV-1531

25-PV-1316

25-H

V-13

02

25-F

V-16

5425

-FV-

1657

27-FV-1025

25-T

V-1

268

25-164

25-PV-1255B

25-141

25-UV-1548

25-FV-1550

25-F

V-15

49

25-LV-1007

25-U

V-1

011

25-U

V-1

012

25-PV-146425-PV-1626

25-LV-1463

25-LV-1321A25-LV-1321B

25-F

V-1

219A

25-F

V-1

219B

25-LV-1327A25-LV-1327B

25-F

V-12

21A

25-F

V-12

21B

25-LV-1448

25-LV-1430A25-LV-1430B

25-F

V-1

224A

25-F

V-1

224B

25-LV-1435A25-LV-1435B

25-FV-1227A25-FV-1227B

25-U

V-10

10

25-F

V-1

546

25-U

V-1

877

25-PV-1559

25-P

V-1

560B

25-P

V-1

560C

25-F

V-1

236A

25-F

V-1

236B

25-U

V-18

78

25-U

V-1

308

25-FV-1543

25-UV-1879

25-U

V-10

09

25-PV-1560A

25-PV-1561A

25-PV-1282B

25-PV-1282A25-HV-1138

25-P

V-15

61B

25-P

V-15

61C

25-F

V-15

62A

25-F

V-15

62B

20


39PROSESS STRØM

25-HA-101

25-HG-103

25-HX-101

25-HX-102

25-HX-103

25-PA-101

25-PA-102

25-PA-103

25-VD-107

25-VE-102

26-VE-101

27-VE-102

27-VE-101

27-KA-101

25-CT-10225-HA-105 25-VE-101

25-HG-101


40PROSESS STRØMVÆSKEDANNINGSKRETS

25-CT-102

25-HA-101

25-HA-105

25-HX-101

25-HX-102

25-HX-103

25-PA-101

25-PA-102

25-PA-103

25-VD-107

25-VE-101

25-VE-102

26-VE-101

27-VE-102

27-VE-101

27-KA-101

25-HA-114

25-KA-102

25-VD-105

25-HG-101

25-HG-102

25-HG-103

21


41PROSESS STRØMVÆSKEDANNINGSKRETSFORKJØLINGSKRETS

25-CT-102

25-HA-101

25-HA-105

25-HG-101

25-HX-101

25-HX-102

25-HX-103

25-PA-101

25-PA-102

25-PA-103

25-VD-107

25-VE-101

25-VE-102

26-VE-101

27-VE-102

27-VE-101

27-KA-101

25-HA-114

25-HG-102

25-KA-102

25-VD-105

25-VD-10225-VD-103

25-HA-112

25-HA-111

25-HG-105

25-HG-104

25-VD-101

25-VD-115

25-VD-109

25-VD-112

25-VD-110

25-VD-116 25-KA-101

25-HG-103


42PROSESS STRØMVÆSKEDANNINGSKRETSFORKJØLINGSKRETSUNDERKJØLINGSKRETS

25-CT-102

25-HA-101

25-HA-105

25-HG-101

25-HX-101

25-HX-102

25-HX-103

25-PA-101

25-PA-102

25-PA-103

25-VD-107

25-VE-101

25-VE-102

26-VE-101

27-VE-102

27-VE-101

27-KA-101

25-HA-114

25-HG-102

25-KA-102

25-VD-105

25-VD-10225-VD-103

25-HA-112

25-HA-111

25-HG-105

25-HG-104

25-VD-101

25-VD-115

25-VD-109

25-VD-112

25-VD-110

25-VD-116 25-KA-101

25-CT-101

25-HA-104

27-HA-113

25-KA-103

25-VD-106

25-HG-103

22


43VÆSKEDANNINGSKRETS

25-HX-101

25-HX-102

25-HA-114

25-KA-102

25-VD-105

25-HG-10225-VD-104


44FORKJØLINGSKRETS

25-HG-101

25-HG-102

25-VD-10225-VD-103

25-HA-112

25-HA-111

25-HG-105

25-HG-104

25-VD-101

25-VD-115

25-VD-109

25-VD-112

25-VD-110

25-VD-116 25-KA-101

27-HG-101

23


45UNDERKJØLINGSKRETS

25-HX-101

25-HX-102

25-HG-102

25-CT-101

25-HA-104

27-HA-113

25-KA-103

25-VD-106

25-VD-114

46

Liquefaction technology – present and prediction(Source: Shell)

24

47

Compressor driver alternatives• Steam turbine

– Refrigerant compressor(s) driven by steam turbine

– Common in older LNG plants

– Steam plant needed, including boiler, feedwater treatment etc.

• Gas turbine

– Direct mechanical compressor drive using gas turbine

– Small plot area, low CAPEX

– Most common solution today

– Capacity of plant determined by available gas turbine sizes

• Electric

– Only Snøhvit so far, but considered in several current developments

– Increased availability, potential use of high-efficiency combined-cycle technology

48

Compressor driver trends

25

49

Mixed Fluid Cascade (MFC) process and energy system at Hammerfest

GG

Pre-coolingCycle

Lique-factionCycle

Sub-coolingCycle

SCCExp./Gener.

LNG Expander/Generator

Plate FinHeatExchangers

Spiral WoundHeatExchangersGenerator

NG

LNG

M

M

M

SCC Compressor

PCC Compressor

LCC Compressor

ElectricPowerGener.

5 x GE LM 6000 GTwith waste heat recovery

G

G

G

G

G

Process heatconsumers

Fuel gasAir

Hotoilcycle

Electric Powerfrom the Grid

Seawater cooling

Cold box

Unit 25

Cycle compression and seawater cooling

Unit 25

Electric power generationwaste heat recovery,hot oil cycleUnit 81 and 50

50

Parallel drivers/compressors (increasing availability) ”Two in one” concept

26

51

Process availability (on-stream time)

GT0.98 *

= 0.96

On-line Availability

= 0.97

= 0.94

GT0.98 *

GT0.98 *

GT0.98 *

GT0.98

GT0.98

GT

GT0.99

Fraction of time

2 circuits

2 circuits1 paralleldriver/compr

3 circuits

52

Heat rejectionAir cooling Water cooling

Tube-in-shellheat exchanger

27

53

Heat rejectionAir cooling

• Large plot area needed

• Lower process efficiency (less LNG for given power input)

• Lower CAPEX than water cooling

• Larger seasonal variation in capacity and efficiency

Water cooling

• More compact plant

• Costly corrosion-resistant materials needed(e.g. titanium)

• High process efficiency

• May need chlorination to prevent fouling

54

Air cooled condensers

28

55

Cooling of LNG plants

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