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Multi-StageCascade 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
02/33
Refrigeration Cycle and Input Condition of Natural Gas
03/33
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.
04/33
Ideal refrigeration Cycle
Process Flow Diagram Pressure Enthalpy Diagram
Compressor
Condenser
ExpansionValve
Evaporator
D
AB
C
A
B C
D
△Hevap
TB=TC
TA TDPA, PD
PB, PC
P
H
By utilizing the Pressure-Enthalpy (P-H) diagram, the refrigeration cycle can be broken down into four distinct steps :
ExpansionEvaporationCompressionCondensation
A
B
C
D
05/33
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 ValuePressure (bar) 53
Temperature (oC) 45
Flow Rate (kg/hr) 625,000
06/33
Cascade Refrigeration
07/33
Cascade Refrigeration
Stream01Pressure : 53bar
Temperature : 45 oCFlow Rate : 625,000 kg/hr
E01Pressure drop(Hot Side) : 0.5barMinimum of [Hot Out-Cold In] and [Hot In-Cold Out] : 3 oCRefrigerant Component : C3Refrigerant Temp. : 11.075 oC
E02Pressure drop(Hot Side) : 0.5barMinimum of [Hot Out-Cold In] and [Hot In-Cold Out] : 3 oCRefrigerant Component : C3
Refrigerant Temp. : -17.148 oC
E03Pressure drop(Hot Side) : 0.5bar
Hot Product Temp. : -37 oCRefrigerant Component : C3Refrigerant Temp. : -40 oC
E04Pressure drop(Hot Side) : 0.5barMinimum of [Hot Out-Cold In] and [Hot In-Cold Out] : 3 oCRefrigerant Component : C2-
Refrigerant Temp. : -69.74 oC
E05Pressure drop(Hot Side) : 0.5bar
Hot Product Temp. : -92 oCRefrigerant Component : C2-
Refrigerant Temp. : -95 oC
E06Pressure drop(Hot Side) : 0.5barMinimum of [Hot Out-Cold In] and [Hot In-Cold Out] : 3 oCRefrigerant Component : C1
Refrigerant Temp. : -118.78 oC
E07Pressure drop(Hot Side) : 0.5barMinimum of [Hot Out-Cold In] and [Hot In-Cold Out] : 3 oCRefrigerant Component : C1
Refrigerant Temp. : -139.29 oC
E08Pressure drop(Hot Side) : 0.5bar
Hot Product Temp. : -152 oCRefrigerant Component : C1Refrigerant Temp. : -155 oC
F01Adiabatic : duty 0
E01 E02 E03 E04 E05 E06 E07 E08CV01
F01
02
01
11
12
03 04 05 06 07 08 09 10
CV01Pressure Drop : 0
CN01
08/33
CN1 Condition & Result
09/33
Rate of LNG Liquefaction=Stream12 Total Rate/Stream01 Total Rate X 100
= 32158.4636/35065.3581 X 100 = 91.71%
Heat duty(106 Kcal/hr)
0 20 40 60 80 100 120 140
Temperature(
℃)
-200
-150
-100
-50
0
50
Cascade Heating Curve
C3
C2-
C1
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
10/33
Cascade Heating Curve
Temperature(℃)
Heat duty(*106 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
11/33
Multi-Stage Cascade Refrigeration Cycle
E01 E02 E03
E04 E05
E06 E07 E08
K01K02K03
Propane
Ethylene
Methane
K04K05
K06K07K08
M01M02M03
M04M05
M06M07M08
CV01F01
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
030201
09
10
11
12
06 07 08
21 22
22V
22L 22B
22A
2423
24L
24V
24B
24A
2625
26V
26L
27
2829
30
31
3233
61
62
62V
62L 62B
62A
6463
64L
64V
64B
64A
6665
66V
66L
67
6970
71
72
7374
66B
66A
68
41
42
42L
42V
42B
42A
4344
44V
44L44B
44A
45 46
4748
49
50
51
12/33
Three-Stage Refrigeration of methane
13/33
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
CV02CV03 CV04
F02 F03 F04
SP01SP02
M01K01M02K02
E06 E07 E08
M03K03
21 22
22V
22L
23
22B
22A 24
24V
25
24L
24B
24A 26
26L
26V
27
2829
30
31
32
33
Ratio per stage
14/33
Calculation of total flowrate of methane
CV02Outlet Pressure :
12.6947 bar
CV03Outlet Pressure :
4.6250 bar
CV04Outlet Pressure :
1.6850 bar
15/33
CN1 Condition & Result
Total Flowrate of methane35431.4336 Kgmol/hr = 568419.403 kg/hr
16/33
Three-Stage Refrigeration Cycle
K01Outlet Pressure : 4.6250barAdiabatic Efficiency : 70%
E06/E07/E08Pressure drop(Hot Side) : 0.5 barCold Product Liquid Fraction : 0
F02/F03/F04Adiabatic : duty 0
Stream21Temperature : -92 ℃
Bubble PointComponent : Methane
Total Fluid Flowrate : 568420 kg/hr
K02Outlet Pressure : 12.6947barAdiabatic Efficiency : 70%
K03Outlet Pressure : 34.845barAdiabatic Efficiency : 70%
E09Pressure drop(Hot Side) : 0.5barHot Product Liquid Fraction : 1
CV02Outlet Pressure :
12.6947 bar
CV03Outlet Pressure :
4.6250 bar
CV04Outlet Pressure :
1.6850 bar
17/33
Two-Stage Refrigeration of ethylene
18/33
E04 E05
04 05 06
E09
E10
E11
CV05CV06
F05 F06
SP03SP04
M04M05 K04K05
41
42
42V
44L
42B
42A 44
43
44V
42L
44B
44A
45
46
4748
4950
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*106 Kcal/hr
19/33
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*106 Kcal/hr
20/33
Calculation of total flowrate of ethylene
CV05Outlet Pressure :
5.2239 bar
CV06Outlet Pressure :
1.6650 bar
21/33
CN3 Condition & Result
Total Flowrate of ethylene53164.75 Kgmol/hr = 1491473.264 kg/hr
22/33
Two-Stage Refrigeration CycleK04
Outlet Pressure : 5.2239barAdiabatic Efficiency : 70%
K05Outlet Pressure : 16.390barAdiabatic Efficiency : 70%
E09Pressure drop(Hot Side) : 0.5barHot Product Liquid Fraction : 1
CV05Outlet Pressure :
5.2239 bar
CV06Outlet Pressure :
1.6650 bar
E04/E05Pressure drop(Hot Side) : 0.5 barCold Product Liquid Fraction : 0
E10Pressure drop(Hot Side) : 0 barHot Product Temperature : 45℃
E11Pressure drop(Hot Side) : 0.5 barHot Product Liquid Fraction : 1
F05/F06Adiabatic : duty 0
Stream41Temperature : -37 ℃
Bubble PointComponent : Ethylene
Total Fluid Flowrate : 1491500 kg/hr
23/33
Three-Stage Refrigerationof propane
24/33
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
62V
62L
62B
62A 64
63
64V
64L
64B
64A 66
65
66L
66V
67
66B
66A
68
71
72 70 69
73
74
K08 K06K07 M06M07M08
CV07CV08 CV09
F07 F08 F09SP05 SP06 SP07
E12
Condenser Heat Duty of C2- Refrigeration Cycle(E11)
= 174.1497*106 Kcal/hr
25/33
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*106 Kcal/hr
26/33
Calculation of total flowrate of propane
CV07Outlet Pressure :
6.5505 bar
CV08Outlet Pressure :
2.7013 bar
CV09Outlet Pressure :
1.114 bar
27/33
CN5 Condition & Result
Total Flowrate of propane87113.3668 Kgmol/hr = 3841394.579 kg/hr
28/33
Three-Stage Refrigeration Cycle
K06Outlet Pressure : 2.7013barAdiabatic Efficiency : 70%
E01/E02/E03Pressure drop(Hot Side) : 0.5 barCold Product Liquid Fraction : 0
F07/F08/F09Adiabatic : duty 0
Stream61Temperature : 45 ℃
Bubble PointComponent : Propane
Total Fluid Flowrate : 3841400 kg/hr
K07Outlet Pressure : 6.5505barAdiabatic Efficiency : 70%
K08Outlet Pressure : 15.885barAdiabatic Efficiency : 70%
E12Pressure drop(Hot Side) : 0.5barHot Product Liquid Fraction : 1
CV07Outlet Pressure :
6.5505 bar
CV08Outlet Pressure :
2.7013 bar
CV09Outlet Pressure :
1.114 bar
E09Pressure drop(Hot Side) : 0.5barHot Product Liquid Fraction : 1
29/33
Multi-Stage Cascade Refrigeration Cycle
& Results
30/33
Multi-Stage Cascade Refrigeration Cycle
31/33
Results of Calculator
Refrigerator Contents Actual Work (kW)
Propane
K08 6.97935E+04
K07 4.65535E+04
K06 3.26463E+04
EthyleneK05 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
32/33
Thank youfor your attention
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