Multi-Stage Cascade Refrigeration System

Multi-Stage

Cascade Refrigeration System

Contents

Refrigeration Cycle and

Input Condition of Natural Gas Cascade Refrigeration

Three-Stage Refrigeration of methane Two-Stage Refrigeration of ethylene Three-Stage Refrigeration of propane

Multi-Stage Cascade Refrigeration Cycle & Results

Refrigeration Cycle and

Input Condition of Natural Gas

What is the refrigerator?

Ø By letting-down the pressure of chilled and highly compressed refrigerant, we can obtain a cold

temperature of refrigerant. By adjusting the pressure letting-down level, we can obtain a wanted temperature level of refrigerant.

Ø By cooling after compressing a vapor stream, we

can obtain a liquefied refrigerant.

Ideal refrigeration Cycle

Process Flow Diagram Pressure Enthalpy Diagram

Compressor

Condenser

Expansion Valve Evaporator

D

A B

C

A

B C

D

△H^evap T_B=T_C

T_A T_D

P_A, P_D

P_B, P_C

P

H

By utilizing the Pressure-Enthalpy (P-H) diagram,

the refrigeration cycle can be broken down into four distinct steps : Expansion

Evaporation Compression Condensation

A B C D

Input Condition of Natural Gas

Component Mole%

Nitrogen 0.22

Methane 91.33

Ethane 5.36

Propane 2.14

I-Butane 0.46

N-Butane 0.47

I-Pentane 0.01

N-Pentane 0.01

Total 100

Contents Value

Pressure (bar) 53

Temperature (

C) 45

Flow Rate (kg/hr) 625,000

Cascade Refrigeration

Cascade Refrigeration

Stream01

Pressure : 53bar Temperature : 45 ^oC Flow Rate : 625,000 kg/hr

E01

Pressure drop(Hot Side) : 0.5bar Minimum of [Hot Out-Cold In]

and [Hot In-Cold Out] : 3 ^oC Refrigerant Component : C3 Refrigerant Temp. : 11.075 ^oC

E02

Pressure drop(Hot Side) : 0.5bar Minimum of [Hot Out-Cold In]

and [Hot In-Cold Out] : 3 ^oC Refrigerant Component : C3 Refrigerant Temp. : -17.148 ^oC

E03

Pressure drop(Hot Side) : 0.5bar Hot Product Temp. : -37 ^oC Refrigerant Component : C3

Refrigerant Temp. : -40 ^oC

E04

Pressure drop(Hot Side) : 0.5bar Minimum of [Hot Out-Cold In]

and [Hot In-Cold Out] : 3 ^oC Refrigerant Component : C2^- Refrigerant Temp. : -69.74 ^oC

E05

Pressure drop(Hot Side) : 0.5bar Hot Product Temp. : -92 ^oC Refrigerant Component : C2^-

Refrigerant Temp. : -95 ^oC

E06

Pressure drop(Hot Side) : 0.5bar Minimum of [Hot Out-Cold In]

and [Hot In-Cold Out] : 3 ^oC Refrigerant Component : C1 Refrigerant Temp. : -118.78 ^oC

E07

Pressure drop(Hot Side) : 0.5bar Minimum of [Hot Out-Cold In]

and [Hot In-Cold Out] : 3 ^oC Refrigerant Component : C1 Refrigerant Temp. : -139.29 ^oC

E08

Pressure drop(Hot Side) : 0.5bar Hot Product Temp. : -152 ^oC

Refrigerant Component : C1 Refrigerant Temp. : -155 ^oC

F01

Adiabatic : duty 0

E01 E02 E03 E04 E05 E06 E07 E08

CV01

F01

02

01

11

12

03 04 05 06 07 08 09 10

CV01

Pressure Drop : 0

CN01

CN1 Condition & Result

Rate of LNG Liquefaction

=Stream12 Total Rate/Stream01 Total Rate X 100

= 32158.4636/35065.3581 X 100 = 91.71%

Heat duty(10 ⁶ Kcal/hr)

0 20 40 60 80 100 120 140

T e m p e ra tu re ( ℃ )

-200 -150 -100 -50 0 50

Cascade Heating Curve

C3

C2

C1

[2]

[3]

[4]

[5]

[6]

[7]

[8]

Cascade Heating Curve

Temperature (℃)

Heat duty (*10

Kcal/hr)

Flowrate of refrigerator

(kg/hr)

[1] 11.08 11.7401 337452.036

[2] -17.15 11.2082 117796.037

[3] -40.00 10.6854 106008.027

[4] -69.74 25.8445 253708.024

[5] -95.00 33.0099 296820.610

[6] -118.78 14.0877 149153.654

[7] -139.29 10.5958 95617.043

[8] -155.00 7.6387 64009.514

Total 124.8103

Multi-Stage Cascade Refrigeration Cycle

E01 E02 E03

E04 E05

E06 E07 E08

K01 K02

K03

Propane

Ethylene

Methane

K04 K05

K06 K07

K08

M01 M02

M03 M04

M05 M06

M07 M08

CV01 F01

F02 F03 F04

F05 F06

F07 F08 F09

E09 E10

E11 E12

CV02 CV03 CV04

CV05

CV06

CV07 CV08 CV09

SP01 SP02

SP03 SP04

SP05 SP06 SP07

04 05

03 02

01

09 10

11

12

06 07 08

21 22

22 V

22L 22

B 22

A 24

23

24L 24 V

24 B

24 A 25 26

26 V

26L 27 28

29

30 31

32 33 61

62 62 V

62L 62

B 62

A 64

63

64L 64 V

64 B

64 A 65 66

66 V

66L 67 69 70

71 72 74 73

66 B 66 A

68

41 42

42L 42 V

42 B

42

43 A 44

44 V

44L 44 B 44 A

45 46

47 48 49

50

51

Three-Stage Refrigeration

of methane

Three-Stage Refrigeration System

Temperature of Refrigerator(E06)

= Dew point temperature of propane at 4.6250 bar

= -118.78 ^oC

Temperature of Refrigerator(E07)

= Dew point temperature of propane at 12.6947 bar

= -139.29 ^oC First Stage Discharge Pressure(K01)

= First Suction Pressure * Ratio per stage

= 1.685 * 2.7448

= 4.6250 bar Second Stage Discharge Pressure(K02)

= Second Suction Pressure * Ratio per stage

= 4.6250 * 2.7448

= 12.6947 bar

06 07 08 09

E09

CV02 CV03 CV04

F02 F03 F04

SP01 SP02

K01 M01 K02 M02

E06 E07 E08

M03 K03

21 22

22 V

22 L

23

22 B

22

A 24

24 V

25

24

L 24

B

24

A 26

26 L 26

V

27 28

29 30

31 32

33

Ratio per stage

Calculation of total flowrate of methane

CV02 Outlet Pressure :

12.6947 bar

CV03 Outlet Pressure :

4.6250 bar

CV04 Outlet Pressure :

1.6850 bar

CN1 Condition & Result

Total Flowrate of methane

35431.4336 Kgmol/hr = 568419.403 kg/hr

Three-Stage Refrigeration Cycle

K01

Outlet Pressure : 4.6250bar Adiabatic Efficiency : 70%

E06/E07/E08

Pressure drop(Hot Side) : 0.5 bar Cold Product Liquid Fraction : 0

F02/F03/F04 Adiabatic : duty 0

Stream21 Temperature : -92 ℃

Bubble Point Component : Methane Total Fluid Flowrate : 568420 kg/hr

K02

Outlet Pressure : 12.6947bar Adiabatic Efficiency : 70%

K03

Outlet Pressure : 34.845bar Adiabatic Efficiency : 70%

E09

Pressure drop(Hot Side) : 0.5bar Hot Product Liquid Fraction : 1

CV02 Outlet Pressure :

12.6947 bar

CV03 Outlet Pressure :

4.6250 bar

CV04 Outlet Pressure :

1.6850 bar

Two-Stage Refrigeration

of ethylene

E04 E05

04 05 06

E09 E10

E11

CV05 CV06

F05 F06

SP03 SP04

M04

M05 K04

K05

41

42

42 V

44 L

42 B

42

A 44

43

44 V

42 L

44 B

44 A 45

46 47

48 49

50

51

Two-Stage Refrigeration System

Temperature of Refrigerator(E04)

= Dew point temperature of propane at 5.2239 bar

= -69.74 ^oC

First Stage Discharge Pressure(K04)

= Suction Pressure * Ratio per stage

= 1.665 * 3.1375

= 5.2239 bar

Ratio per stage

Condenser Heat Duty of C1 Refrigeration Cycle(E09)

= 56.2055*10⁶Kcal/hr

Calculation of total flowrate of ethylene

Stream Name 44A 46

Temperature (℃) -95.00 -95.00

Pressure (bar) 1.665 1.665

Flowrate

(kgmole/hr) 18015.211 18015.211

Flowrate

(kg/hr) 505395.121 505395.121

E09 Duty 56.2055*10

Kcal/hr

Calculation of total flowrate of ethylene

CV05 Outlet Pressure :

5.2239 bar

CV06 Outlet Pressure :

1.6650 bar

CN3 Condition & Result

Total Flowrate of ethylene

53164.75 Kgmol/hr = 1491473.264 kg/hr

Two-Stage Refrigeration Cycle

K04

Outlet Pressure : 5.2239bar Adiabatic Efficiency : 70%

K05

Outlet Pressure : 16.390bar Adiabatic Efficiency : 70%

E09

Pressure drop(Hot Side) : 0.5bar Hot Product Liquid Fraction : 1

CV05 Outlet Pressure :

5.2239 bar

CV06 Outlet Pressure :

1.6650 bar

E04/E05

Pressure drop(Hot Side) : 0.5 bar Cold Product Liquid Fraction : 0 E10

Pressure drop(Hot Side) : 0 bar Hot Product Temperature : 45℃

E11

Pressure drop(Hot Side) : 0.5 bar Hot Product Liquid Fraction : 1

F05/F06 Adiabatic : duty 0

Stream41 Temperature : -37 ℃

Bubble Point Component : Ethylene Total Fluid Flowrate : 1491500 kg/hr

Three-Stage Refrigeration

of propane

Three-Stage Refrigeration System

Temperature of Refrigerator(E01)

= Dew point temperature of propane at 2.7013 bar

= -17.148 ^oC

Ratio per stage

Temperature of Refrigerator(E02)

= Dew point temperature of propane at 6.5505 bar

= 11.075 ^oC

First Stage Discharge Pressure(K06)

= First Suction Pressure * Ratio per stage

= 1.114 * 2.4249

= 2.7013 bar Second Stage Discharge Pressure(K07)

= Second Suction Pressure * Ratio per stage

= 2.7013 * 2.4249

= 6.5505 bar

E01 E02 E03

E11

01 02 03 04

61

62

62 V

62

L 62

B

62

A 64

63

64 V

64 L

64 B

64

A 66

65

66 L 66

V 67

66 B

66 A

68 71

72 70 69

73

74

K08 M08 K07 M07 K06 M06

CV07 CV08 CV09

F07 SP05 F08 SP06 F09 SP07

E12

Condenser Heat Duty of C2^- Refrigeration Cycle(E11)

= 174.1497*10⁶Kcal/hr

Calculation of total flowrate of propane

Stream Name 66A 68

Temperature (℃) -40.00 -39.99

Pressure (bar) 1.114 1.114

Flowrate

(kgmole/hr) 39180.305 39180.305

Flowrate

(kg/hr) 1727714.258 1727714.258

E09 Duty 174.1497*10

Kcal/hr

Calculation of total flowrate of propane

CV07 Outlet Pressure :

6.5505 bar

CV08 Outlet Pressure :

2.7013 bar

CV09 Outlet Pressure :

1.114 bar

CN5 Condition & Result

Total Flowrate of propane

87113.3668 Kgmol/hr = 3841394.579 kg/hr

Three-Stage Refrigeration Cycle

K06

Outlet Pressure : 2.7013bar Adiabatic Efficiency : 70%

E01/E02/E03

Pressure drop(Hot Side) : 0.5 bar Cold Product Liquid Fraction : 0

F07/F08/F09 Adiabatic : duty 0

Stream61 Temperature : 45 ℃

Bubble Point Component : Propane Total Fluid Flowrate : 3841400 kg/hr

K07

Outlet Pressure : 6.5505bar Adiabatic Efficiency : 70%

K08

Outlet Pressure : 15.885bar Adiabatic Efficiency : 70%

E12

Pressure drop(Hot Side) : 0.5bar Hot Product Liquid Fraction : 1

CV07 Outlet Pressure :

6.5505 bar

CV08 Outlet Pressure :

2.7013 bar

CV09 Outlet Pressure :

1.114 bar

E09

Pressure drop(Hot Side) : 0.5bar Hot Product Liquid Fraction : 1

Multi-Stage Cascade Refrigeration Cycle

& Results

Multi-Stage Cascade Refrigeration Cycle

Results of Calculator

Refrigerator Contents Actual Work (kW)

Propane

K08 6.97935E+04

K07 4.65535E+04

K06 3.26463E+04

Ethylene K05 4.93771E+04

K04 2.40789E+04

Methane

K03 1.94100E+04

K02 6.41777E+03

K01 1.91124E+03

Total 2.50188E+05

LNG Flowrate (kg/hr) 577679.6567

Specific Power for produced LNG [kWh/kg]

= 0.433 kWh/kg LNG

Thank you

for your attention