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A Study on the Methane A Study on the Methane Isotope Separation Using Isotope Separation Using
Cryogenic DistillationCryogenic Distillation
Jonghwan KIM1, Sangjin PARK1, Sehoon YOON1, Jungho CHO2*, Young-Chul LEE3, Taek-Yong SONG3
and Euy Soo LEE1*
Dongguk University 1Dong Yang University 2
LNG Technology Research Center 3
Slide 2
LNG
Synthetic Gas(CO+H2)Reactor
Demethanizer Concentration of C13 Methane
Dehydrogenation &Dehydration
Concentration of C13 COPath I
Path II
Two Paths to Obtain Two Paths to Obtain 1313CHCH44 Based on a Based on a Cryogenic DistillationCryogenic Distillation
Slide 3
Vapor Pressure Correlation of Vapor Pressure Correlation of 1212CHCH44 MethaneMethane
! Antoine Vapor Pressure Equation is:
! Normal boiling temperature of 12CH4 methane is:
16.784.8972093.13ln
−−=
TPL (PL in kPa and T in K)
KT 6697738.111)325.101ln(2093.13
84.89716.7 =−
+=
Slide 4
Vapor Pressure Correlation of Vapor Pressure Correlation of 1313CHCH44 MethaneMethane
! Correlation of 13CH4 methane is:
! Vapor pressure expression of 13CH4 methane is:
! Normal boiling temperature of 13CH4 methane is:
TTPP
H
L 192.09.36log 2 −=
(PL in kPa and T in K)
TTTHP
192.09.3616.784.8972093.13log 210
+−
−−
=
KT 704475.111= (0.0347K difference with 12CH4 methane)
Slide 5
Relative Volatilities Relative Volatilities btnbtn 1212CHCH44 & & 1313CHCH44
! Definition of relative volatility of component ‘i’ and component ‘j’ is:
( )( ) j
i
j
i
j
iij P
PPPPP
KK ===α (component ‘’ is defined as more
volatile than component ‘j’)
1.003179.75580.00108.8731.003459.79660.00105.6621.003651.81252.00104.139
1.002999.714100.00111.5101.0025149.638150.00116.6711.0022199.568200.00120.6531.0018299.46300.00126.784
AlphaVP of 13CH4
(kPa)VP of 12CH4
(kPa)Temperature (K)
Slide 6
1313CHCH44 Property Calculation Using PRProperty Calculation Using PR! We used Peng-Robinson equation of state for the
modeling of methane isotope separation.
! Parameter ‘a’ and ‘b’ are functions of critical temperature and pressure.
! Alpha value is functions of reduced temperature and acentric factor.
! Acentric factor of 13CH4 methane was adjusted to accurately estimate vapor pressure at a given temperature.
( ) ( )bVbbVVa
bVRTP
−++⋅−
−= α
Slide 7
Comparison of Comparison of 1313CHCH44 Vapor Pressure Vapor Pressure btnbtnCorrelation & PR EquationCorrelation & PR Equation
Temperature ( K )70 80 90 100 110 120
Pres
sure
( K
Pa )
0
20
40
60
80
100 • Acentric factor, ω was modified as0.0108 to fit the correlated vaporpressure vs. temperature.
Slide 8
LNG Feed Composition: LNG Feed Composition: Supplied from KOGAS
-155.0Temperature (oC)
0.070089.35740.90267.81001.30000.24000.3200
Nitrogen12CH4 Methane13CH4 MethaneEthanePropanei-Butanen-Butane
Mole PercentComponents
Slide 9
1313CHCH44 Separation ProcedureSeparation Procedure! Separation of C2+ from LNG:! Step 1: Concentration of 13CH4 from 1% to 9.2376%! Step 2: Concentration of 13CH4 from 9.2376% to 35%! Step 3: Concentration of 13CH4 from 35% to 40%! Step 4: Concentration of 13CH4 from 40% to 60%! Step 5: Concentration of 13CH4 from 60% to 80%! Step 6: Concentration of 13CH4 from 80% to 90%
Slide 10
2
3
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1
20T01
1
2
3
DemethanizerDemethanizer Simulation Using PRO/IISimulation Using PRO/II
File Save As: DeC1_01.prz
Slide 11
Reflux Ratio0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Theo
retic
al N
umbe
r of T
ray
1000
2000
3000
4000
5000
Shortcut SimulationShortcut Simulation
Minimum number of tray = 1,644
Minimum reflux ratio = 887
Optimum theoretical number of tray = 2,400
Slide 12
Rigorous Simulation Example: Rigorous Simulation Example: PRO/II
File Save As: Rigorous_Small.prz
266
13019425832238645051457864270677083489896210261090115412181282134614101474153816021666173017941858192219862050211421782242230623702399
1
2400T01
1 2
3
Slide 13
1313CHCH44 Separation Step: Separation Step: 200 stages for each column
………Feed
Concentrated 13CH4
12CH4 Product
T01 T02 T03 T12
Slide 14
Case Study Results for a DeC1 & Cryogenic Case Study Results for a DeC1 & Cryogenic Distillation ColumnsDistillation Columns
2,400646.01,85280%!90%Step 7
2,400739.01,68860%!80%Step 6
2,400831.41,57840%!60%Step 5
2,400887.01,64435%!40%Step 4
2,600905.51,8729.2376%!35%Step 3
2,000253.01,4171%!9.2376%Step 2
20--DemethanizerStep 1
TheoreticalTrays
Minimum Reflux Ratio
Minimum Trays
Role
Slide 15
Relation of a distillation column operating Relation of a distillation column operating time and top time and top 1313CHCH44 impuritiesimpurities
6,209 hours-Step 1
5,158 hours15.0 mole%Step 2
926 hours5.0 mole%Step 3
24 hours5.0 mole%Step 4
59 hours2.0 mole%Step 5
31 hours1.0 mole%Step 6
11 hours0.5 mole%Step 7
Operating TimeTop 13CH4 Impurities
Slide 16
ConclusionsConclusions! 13CH4 isotope separation process using a cryogenic
distillation was simulated with PRO/II with PROVISION version 6.01. The modified Peng-Robinson modeling equation with a newly adjusted acentric factor was suitable to simulate the separation between methane isotope.
! It was concluded that 2,400 theoretical stages and six step procedures were required to obtain a 90 mole% of 13CH4methane product.
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