James BronfenbrennerDr. Yu-Nan Liu

Dr.Tamara Daugherty

James BronfenbrennerDr. Yu-Nan Liu

Dr.Tamara Daugherty

LNG Liquefaction CycleEfficiency Analysis

Air Products and Chemicals, Inc.

LNG Liquefaction CycleEfficiency Analysis

Air Products and Chemicals, Inc.

©1998 Air Products and Chemicals, Inc.

Carnot Work

Carnot Cycle Work

Wmin = To ΔS - ΔH

Carnot efficiency W = (To) - (Tr) Q o (To)

COPQr = (Tr) W (To) - (Tr)

Carnot Cycle

Wmin

Entropy

Temp

Temperature-Entropy Diagram

-

-

To

Tr

0

To

Tr δWr

δWr-1

δWr-2

δWr-3

δW1T1

Tr-3

Tr-2

Tr-1

Entropy

T-S DiagramIn

Out0

. . . . . . . . Tem

pera

ture

Minimum work: δW = To δS - δH

Carnot Work Over a Temperature Range

Minimum Work

A

BC

D

E-40

0

40

80

Tem

pera

ture

(C)

Temperature-Entropy Diagram Pure Component System

1

2

Entropy

A

B

CB2

E

C2

D

Temperature-Entropy Diagram Mixed Refrigerant Cycle

-160

-80

0

80

160

Tem

pera

ture

(C)

Entropy

Single MR Cascade Dual MR

Lost Work Components

0%

20%

40%

60%

Lost

Wor

k, %

Tot

al W

ork

Lost

Wor

k, %

Tot

al W

ork

(Incr

easi

ng P

ower

)

(Incr

easi

ng P

ower

)

dP, Mix, Sep

P Letdown

C3 EvapMCHE,C1/C2 Evap.Inter/AfterCoolers

Compress

C3/MR

Compressor Performance Curve

% Volumetric Flow

% H

ead

80

100

120

80 100 120

Surge

100%

105%

95%

Speed

83

Efficiency %8282

80

80

Interstage Cooling/Condensing Issues

Interstage Cooling - More Isothermal Compression

Cp/Cv Ratio N2-1.4; C1-1.3; MR-1.2; C3-1.1

Interstage Condensing - Converts Compression to Pump Power

Heat Exchange Area

Pow

erPower - Area Tradeoff

ΔTmean 0

DISTILLATION

MR TO COMPRESSOR

DRY FEED

MR FROMCOMPRESSOR

Heat Exchange Area

Pow

erMaldistribution

ΔTmean 0

20% Maldistribution

Perfect Mixing

Cycle Efficiency Comparison

Ideal Carnot

C3-MR Dual MR Cascade Single MR0

20

40

60

Effic

ienc

y, %

63

48 48 45 43

•Thermodynamic fundamentals•Sound engineering practices•Defined evaluation criteria

Will produce a meaningfulLNG Liquefaction Cycle

Efficiency Analysis

Air Products and Chemicals, Inc.

•Thermodynamic fundamentals•Sound engineering practices•Defined evaluation criteria

Will produce a meaningfulLNG Liquefaction Cycle

Efficiency Analysis

Air Products and Chemicals, Inc.©1998 Air Products and Chemicals, Inc.