p200514-301

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

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

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 =−

+=

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)

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)

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

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.

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

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%

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

1

20T01

1

2

3

DemethanizerDemethanizer Simulation Using PRO/IISimulation Using PRO/II

File Save As: DeC1_01.prz

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

Rigorous Simulation Example: Rigorous Simulation Example: PRO/II

File Save As: Rigorous_Small.prz

266

13019425832238645051457864270677083489896210261090115412181282134614101474153816021666173017941858192219862050211421782242230623702399

1

2400T01

1 2

3

1313CHCH44 Separation Step: Separation Step: 200 stages for each column

………Feed

Concentrated 13CH4

12CH4 Product

T01 T02 T03 T12

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

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





Operating TimeTop 13CH4 Impurities

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.

p200514-301

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