OAPEC-IFP Joint Seminar 17 – 19 June 2008 1

SELECTING AN LNG PROCESS

Not an easy task

Pierre Boutelant

OAPEC-IFP Joint Seminar 17 – 19 June 2008 2

Looking for Efficiency

• A better efficiency (kW per ton of LNG)

Less Capex for a given production

Savings on natural gas resources

Less CO2 to atmosphere

OAPEC-IFP Joint Seminar 17 – 19 June 2008 3

SEVERAL PROCESSES ARE AVAILABLE

• Today a fierce competition between the « Old » and the « New » processes.

• Before comparing efficiencies, the bases must be clearly defined so as to compare « apples with apples ».

OAPEC-IFP Joint Seminar 17 – 19 June 2008 4

C3/MR

LNG

Feed Gas

CW

CW

Propane cycle MR cycle

CW

OAPEC-IFP Joint Seminar 17 – 19 June 2008 5

APX

LNG

Feed Gas

CW

CW

CW

N2 CyclePropane cycle MR cycle

CW

OAPEC-IFP Joint Seminar 17 – 19 June 2008 6

Cascade

C3

C2=

C1

Natural Gas

PFHE PFHE PFHE

LNG

OAPEC-IFP Joint Seminar 17 – 19 June 2008 7

DMR

Naturalgas

LNG

First mixedrefrigerantcycle

OAPEC-IFP Joint Seminar 17 – 19 June 2008 8

MFCP

Naturalgas

LNG

Pre-coolingMR cycle

LiquefactionMR cycle

Plate-finExchangers

Sub-coolingMR cycle

Spiral-woundheat-exchanger

Spiral-woundheat-exchanger

OAPEC-IFP Joint Seminar 17 – 19 June 2008 9

Liquefin

Plate finsHeat Exchanger

C2+

-30 °C

-60 °C

LNG

Natural Gas

-150 °C

-160 °C

OAPEC-IFP Joint Seminar 17 – 19 June 2008 10

Enthalpy curvesfor Liquefin process

Pre-cooling

-80

-60

-40

-20

0

20

40

60

0 50 100 150 200 250

MW

Cryogenic Section

-160-140-120-100

-80-60-40-20

0

0 50 100 150

Temperature, °C

MW

Temperature, °C

OAPEC-IFP Joint Seminar 17 – 19 June 2008 11

Enthalpy Curves – Pre Cooling

-80

-60

-40

-20

0

20

40

60

0 50 100 150 200 250

Enthalpy (MW)

Te

mp

éra

ture

(°C

)

OAPEC-IFP Joint Seminar 17 – 19 June 2008 12

The « Key » Parameters

• Their selected value have a direct effect on the theoretical plant production

• Condensing temperature of pre-cooling medium

• Amount of Flash Gas • LPG’s recovery rate• Compressors’ efficiency

OAPEC-IFP Joint Seminar 17 – 19 June 2008 13

Condensing temperatureof pre-cooling refrigerant

C2+

-30 °C

-60 °C

LNG-150 °C

OAPEC-IFP Joint Seminar 17 – 19 June 2008 14

LNG Production vs MR1 condensing temperature

100

101

102

103

39 40 41 42 43 44 45

Condenser outlet temperature, °C

% LNGproduction

OAPEC-IFP Joint Seminar 17 – 19 June 2008 15

Less surface required for refrigerant fluids condensers

Condensers’ LMTD

20

25

30

35

40

45

50

55

60

0 50 100 150 200 250 300 350

Duty

Temperature,°C

Same final condensation temperature

Propane

MR Condensation

Air or Water

Same condensation duty

LMTD higher (+35%) ⇒ Condenser 35% smaller

OAPEC-IFP Joint Seminar 17 – 19 June 2008 16

Flash Gas quantity

C2+

-30 °C

-60 °C

LNG-150 °C

Flash gas

-160 °C

OAPEC-IFP Joint Seminar 17 – 19 June 2008 17

LNG Production vs Flash Gas quantity

100

101

102

103

104

105

106

100 110 120 130 140

Relative quantity of Flash Gas %

LNG relative production %

OAPEC-IFP Joint Seminar 17 – 19 June 2008 18

LPG recovery rate

C2+

-30 °C

-60 °C

LNG-150 °C

OAPEC-IFP Joint Seminar 17 – 19 June 2008 19

LNG Production vs LPG recovery rate

91

92

93

94

95

96

97

98

99

100

30 40 50 60 70 80 90

91

92

93

94

95

96

97

98

99

100

30 40 50 60 70 80 90

C3 recovery rate (% of total C3 in the Feed Gas)

LNG Production %

OAPEC-IFP Joint Seminar 17 – 19 June 2008 20

Compressors efficiency

C2+

-30 °C

-60 °C

LNG-150 °C

OAPEC-IFP Joint Seminar 17 – 19 June 2008 21

LNG Production vs compressorsefficiency

LNG Production vs Compressors Polytropic efficiency

79 80 81 82 83 84 85

96

98

100

102

104

LNGRelative

Production %

Compressors Polytropic Efficiency %

OAPEC-IFP Joint Seminar 17 – 19 June 2008 22

CONCLUSION (1)

• In addition to “classical” conditions such as• Feed gas pressure & composition• Ambient temperature, etc.

• The selected data for the following “external” parameters must be known :• T approach on MR condensers • Compressors’ polytropic efficiency• Amount of Flash Gas • LPG recovery rate

• Altogether they can artificially affect the process efficiency up to 20 %

OAPEC-IFP Joint Seminar 17 – 19 June 2008 23

Conclusion (2)

• The various LNG processes available today have different efficiencies

• The “absolute” efficiency is meaningless

• Before comparing the « vendors’ » efficiency, make sure that processes have been optimized for YOUR project, hence on identical bases.

OAPEC-IFP Joint Seminar 17 – 19 June 2008 24

Thank you for your attention