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 02/33

Refrigeration Cycle and Input Condition of Natural Gas 03/33

What is the refrigerator? Ø y letting-down the pressure of chilled and highly compressed refrigerant, we can obtain a cold temperature of refrigerant. y adjusting the pressure letting-down level, we can obtain a wanted temperature level of refrigerant. Ø y cooling after compressing a vapor stream, we can obtain a liquefied refrigerant. 04/33

Ideal refrigeration Cycle Compressor Condenser P C D T T D D P, P D Evaporator T =T C P, P C C Expansion Valve H evap Process Flow Diagram Pressure Enthalpy Diagram H y utilizing the Pressure-Enthalpy (P-H) diagram, the refrigeration cycle can be broken down into four distinct steps : C D Expansion Evaporation Compression Condensation 05/33

Input Condition of Natural Gas Contents Value Pressure (bar) 53 Temperature ( o C) 45 Flow Rate (kg/hr) 625,000 Component Mole% Nitrogen 0.22 Methane 91.33 Ethane 5.36 Propane 2.14 I-utane 0.46 N-utane 0.47 I-Pentane 0.01 N-Pentane 0.01 Total 100 06/33

Cascade Refrigeration 07/33

Cascade Refrigeration E01 Pressure drop(hot Side) : 0.5bar Minimum of [Hot Out-Cold In] and [Hot In-Cold Out] : 3 o C Refrigerant Component : C3 Refrigerant Temp. : 11.075 o C E04 Pressure drop(hot Side) : 0.5bar Minimum of [Hot Out-Cold In] and [Hot In-Cold Out] : 3 o C Refrigerant Component : C2 - Refrigerant Temp. : -69.74 o C E06 Pressure drop(hot Side) : 0.5bar Minimum of [Hot Out-Cold In] and [Hot In-Cold Out] : 3 o C Refrigerant Component : C1 Refrigerant Temp. : -118.78 o C E02 Pressure drop(hot Side) : 0.5bar Minimum of [Hot Out-Cold In] and [Hot In-Cold Out] : 3 o C Refrigerant Component : C3 Refrigerant Temp. : -17.148 o C E05 Pressure drop(hot Side) : 0.5bar Hot Product Temp. : -92 o C Refrigerant Component : C2 - Refrigerant Temp. : -95 o C E07 Pressure drop(hot Side) : 0.5bar Minimum of [Hot Out-Cold In] and [Hot In-Cold Out] : 3 o C Refrigerant Component : C1 Refrigerant Temp. : -139.29 o C 11 02 03 04 05 06 07 08 09 10 01 E01 E02 E03 E04 E05 E06 E07 E08 CV01 F01 Stream01 Pressure : 53bar Temperature : 45 o C Flow Rate : 625,000 kg/hr E03 Pressure drop(hot Side) : 0.5bar Hot Product Temp. : -37 o C Refrigerant Component : C3 Refrigerant Temp. : -40 o C E08 Pressure drop(hot Side) : 0.5bar Hot Product Temp. : -152 o C Refrigerant Component : C1 Refrigerant Temp. : -155 o C CV01 Pressure Drop : 0 F01 diabatic : duty 0 12 CN01 08/33

CN1 Condition & Result Rate of LNG Liquefaction =Stream12 Total Rate/Stream01 Total Rate X 100 = 32158.4636/35065.3581 X 100 = 91.71% 09/33

Cascade Heating Curve 50 0 [1] ) [2] -50 [3] [4] -100 [5] Temperature( -150 [6] C2 - [7] C3 [8] C1-200 0 20 40 60 80 100 120 140 Heat duty(10 6 Kcal/hr) 10/33

Cascade Heating Curve Temperature ( ) Heat duty (*10 6 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 Propane K08 M08 K07 M07 K06 M06 72 70 69 74 73 71 61 E12 62 V 62 63 CV07 CV08 CV09 64L 62 F07 F08 F09 SP05 62L 62 64 64 V 65 SP06 64 64 66L 66 V 66 67 66 SP07 66 68 50 K05 Ethylene M05 K04 M04 48 47 01 02 E01 E02 E03 03 E10 51 49 42 V 44 V 41 E11 42 CV05 F05 43 42L SP03 42 42 44 CV06 F06 44L 45 46 44 SP04 44 Methane 04 05 E04 E05 K03 M03 31 K02 M02 29 K01 28 M01 33 32 30 E09 CV02 21 22 22 V 23 22 CV03 24 24 V 25 24L 24 CV04 26 26 V 27 F02 F03 F04 22L 22 SP01 SP02 24 26L 06 07 08 E06 E07 E08 11 09 10 CV01 F01 12 12/33

Three-Stage Refrigeration of methane 13/33

Three-Stage Refrigeration System Second Stage Discharge Pressure(K02) = Second Suction Pressure * Ratio per stage = 4.6250 * 2.7448 = 12.6947 bar First Stage Discharge Pressure(K01) = First Suction Pressure * Ratio per stage = 1.685 * 2.7448 = 4.6250 bar Ratio per stage K03 32 M03 K02 30 M02 K01 M01 31 29 28 33 E09 22 V 24 V 26 V 23 22 24 25 24 26 27 21 22 CV02 CV03 CV04 F02 F03 F04 22 L SP01 22 24 L SP02 24 26 L 06 07 08 09 E06 E07 E08 Temperature of Refrigerator(E06) = Dew point temperature of propane at 4.6250 bar = -118.78 o C Temperature of Refrigerator(E07) = Dew point temperature of propane at 12.6947 bar = -139.29 o C 14/33

Calculation of total flowrate of methane CV02 Outlet Pressure : 12.6947 bar CV03 Outlet Pressure : 4.6250 bar CV04 Outlet Pressure : 1.6850 bar 15/33

CN1 Condition & Result Total Flowrate of methane 35431.4336 Kgmol/hr = 568419.403 kg/hr 16/33

Three-Stage Refrigeration Cycle K03 Outlet Pressure : 34.845bar diabatic Efficiency : 70% K02 Outlet Pressure : 12.6947bar diabatic Efficiency : 70% K01 Outlet Pressure : 4.6250bar diabatic 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 F02/F03/F04 diabatic : duty 0 Stream21 Temperature : -92 ubble Point Component : Methane Total Fluid Flowrate : 568420 kg/hr E06/E07/E08 Pressure drop(hot Side) : 0.5 bar Cold Product Liquid Fraction : 0 17/33

Two-Stage Refrigeration of ethylene 18/33

Two-Stage Refrigeration System First Stage Discharge Pressure(K04) = Suction Pressure * Ratio per stage = 1.665 * 3.1375 = 5.2239 bar Ratio per stage 50 K05 49 M05 K04 M04 48 47 E10 51 E11 42 V 43 42 44 44 V 45 Condenser Heat Duty of C1 Refrigeration Cycle(E09) = 56.2055*10 6 Kcal/hr 41 CV05 42 F05 CV06 F06 44 46 Temperature of Refrigerator(E04) = Dew point temperature of propane at 5.2239 bar = -69.74 o C 42 L SP03 42 44 L SP04 44 E09 04 05 06 E04 E05 19/33

Calculation of total flowrate of ethylene Stream Name 44 46 Temperature ( ) -95.00-95.00 Pressure (bar) 1.665 1.665 Flowrate (kgmole/hr) Flowrate (kg/hr) 18015.211 18015.211 505395.121 505395.121 E09 Duty 56.2055*10 6 Kcal/hr 20/33

Calculation of total flowrate of ethylene CV05 Outlet Pressure : 5.2239 bar CV06 Outlet Pressure : 1.6650 bar 21/33

CN3 Condition & Result Total Flowrate of ethylene 53164.75 Kgmol/hr = 1491473.264 kg/hr 22/33

Two-Stage Refrigeration Cycle K05 Outlet Pressure : 16.390bar diabatic Efficiency : 70% K04 Outlet Pressure : 5.2239bar diabatic Efficiency : 70% E10 Pressure drop(hot Side) : 0 bar Hot Product Temperature : 45 E11 Pressure drop(hot Side) : 0.5 bar Hot Product Liquid Fraction : 1 CV05 Outlet Pressure : 5.2239 bar F05/F06 diabatic : duty 0 E09 Pressure drop(hot Side) : 0.5bar Hot Product Liquid Fraction : 1 CV06 Outlet Pressure : 1.6650 bar Stream41 Temperature : -37 ubble Point Component : Ethylene Total Fluid Flowrate : 1491500 kg/hr E04/E05 Pressure drop(hot Side) : 0.5 bar Cold Product Liquid Fraction : 0 23/33

Three-Stage Refrigeration of propane 24/33

Three-Stage Refrigeration System Second Stage Discharge Pressure(K07) = Second Suction Pressure * Ratio per stage = 2.7013 * 2.4249 = 6.5505 bar First Stage Discharge Pressure(K06) = First Suction Pressure * Ratio per stage = 1.114 * 2.4249 = 2.7013 bar Ratio per stage K08 73 M08 K07 71 M07 K06 M06 72 70 69 74 61 E12 62 V 63 62 64 64 V 65 64 66 Condenser Heat Duty of C2 - Refrigeration Cycle(E11) = 174.1497*10 6 Kcal/hr 66 V 67 68 CV07 62 F07 SP05 CV08 F08 SP06 CV09 F09 SP07 66 E11 62 L 62 64 L 64 66 L 66 01 02 03 04 E01 E02 E03 Temperature of Refrigerator(E01) = Dew point temperature of propane at 2.7013 bar = -17.148 o C Temperature of Refrigerator(E02) = Dew point temperature of propane at 6.5505 bar = 11.075 o C 25/33

Calculation of total flowrate of propane Stream Name 66 68 Temperature ( ) -40.00-39.99 Pressure (bar) 1.114 1.114 Flowrate (kgmole/hr) Flowrate (kg/hr) 39180.305 39180.305 1727714.258 1727714.258 E09 Duty 174.1497*10 6 Kcal/hr 26/33

Calculation of total flowrate of propane CV07 Outlet Pressure : 6.5505 bar CV08 Outlet Pressure : 2.7013 bar CV09 Outlet Pressure : 1.114 bar 27/33

CN5 Condition & Result Total Flowrate of propane 87113.3668 Kgmol/hr = 3841394.579 kg/hr 28/33

Three-Stage Refrigeration Cycle K08 Outlet Pressure : 15.885bar diabatic Efficiency : 70% K07 Outlet Pressure : 6.5505bar diabatic Efficiency : 70% K06 Outlet Pressure : 2.7013bar diabatic 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 F07/F08/F09 diabatic : duty 0 Stream61 Temperature : 45 ubble Point Component : Propane Total Fluid Flowrate : 3841400 kg/hr E01/E02/E03 Pressure drop(hot Side) : 0.5 bar Cold Product Liquid Fraction : 0 29/33

Multi-Stage Cascade Refrigeration Cycle & Results 30/33

Multi-Stage Cascade Refrigeration Cycle 31/33

Results of Calculator Refrigerator Contents ctual Work (kw) K08 6.97935E+04 Propane K07 4.65535E+04 K06 3.26463E+04 Ethylene K05 4.93771E+04 K04 2.40789E+04 K03 1.94100E+04 Methane 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

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