Gas Separation

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??????????
???????? 253789

• Gas Separation

??????? ???????????? ?????????????????????????? ??
??????????????????
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????????????

• ????????????????????????????????????????
• ????????????????????
• ???????????????
• ????????????????????

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Gas Separation

• ???????????????????????? 100 ??
  ????????????????????????????? 20 ??
• ????? ?????????????????????????
• ???????????????????? ???? Cryogenic / Adsorption
  / Absorption
• History
• 1850 Thomas Graham ?????????????????????????????
  Grahams Law
• 1943-45 ???? Manhatton Project
  ????????????????? Knoxville, Tennessee
• 1940-50 Barrer ?????? ?? Solution-Diffusion Model
  
• 1980 Monsato ?????????????????????????????????????
  ??
• ?????????????? CO2 ?????? Methane
  ?????????????????????????
• ???????? ???????????? N2 ??????????????? 10,000
  ??? (gt 50 ???????)

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History
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??????????????

• ??????????? 2 ??? ??? Gas Diffusion ??? Gas
  Permeation

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??????????????

• Gas Diffusion ????????????????????????
  ?????????? 3 ????????
• - Poiseuille Flow/Viscous Flow ?????? gt 50 nm
• - Knudsen Flow 2nm lt ?????? lt 50 nm
• - Molecular Sieving lt 2nm
• Mean Free Path ????????????????????????????????
  ????????????????
• ???????????? 500 2000 A

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??????????????

• ???????????????? 50 nm ???????????????????????????
  ???????????????
• ????????? gt 50 nm ?????????????? ?????????????
• ???????????? Molecular Sieving ????????
  ??????????????????????
• ?????????? Diffusion ????????????????????
  ??????????????????????????

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??????????????

• 2) Gas Permeation ????????????????????
  ?????????? Solution-Diffusion

Ficks Law
Ji flux (m3(STP)/m2.s) Ci
concentration (m3(STP)/m3) Di diffusion
coefficient (m2/s) ?m membrane thickness
(m) Si sorption coefficient (m3(STP)/
m3.Pa) Pi partial pressure (Pa)
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????????????????????

• ??????

?????????????????????? (membrane
permeability) ????? Barrer 0.76 x 10-17 m3
(STP).m/m2.s.Pa 10-10 cm3(STP).cm/cm2.s.cm.Hg
(1)
??? ???????? Permeance (m3/m2.s.Pa)
??????????????? (Separation Factor / Selectivity)
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????? 1

• ?????????????????? Butyl Rubber
  ??????????????????????????? ??????????????????????
  ? 2400 cm3 (STP) ?????????? 2 Bar
  ???????????????????????????? ????????????
  ????????? (?P) ????? ?????? 1 mm ????????? 2400
  cm2 ??????????????????????????????? 0.9 Barrer

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??? D Diffusion Coefficient

• ????????????????????????? ????????????????????????
  ??????
• ??????????????????? ??????????
• ???????????????????????????????????????????
  (Rubbery State) ???????????????????? (Glassy
  State) ??????????????
• ???? Hydrogen ??? Pentane

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??? S Sorption Coefficient

• ??? S ??? ??????????????????????????
  ??????????????????????????????????????????????????
  ???? ?????????????????????????????????????????
  ?????????????????????????
• ?????????????????????????????????

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??? ??????????????????????

• ???????????? D ??? S
• ?????????????????????? ?????????????????????????
  ? ????????????????????????????????????????????????
  ??????????????????? ?????????????????
• ??? ?????? ? ???
• ?????????????????? ??????????????
  ??????????????????????????????????
• ??? ??? ??? ? ???

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??? Permeability ???????
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Membranes

• Metal Membranes ?????????????????
• ??? Hydrogen ??? Palladium / Silver Alloy ???
  370 ?C ??????? 450 psi
• ???????????????????????? 99.9
  ???????????????????????????????????
• Polymeric Membranes ??????? ?????????????????
  ???? Polyaramide Polyimide Polyamide etc.
  ???????????????????????????
• ????????????????????????????????????????
  ???????????? defects

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Membranes

• Ceramic and Zeolite Membranes ???????????????????
  ?? Sol-Gel ???? Zeolite ?????????????????????
  ?????????? Selectivity ?????? ????????????????
  ????????????????????????????? Mixed-Matrix
  Membrane ??????

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Membrane Modules

• ?????????? ??????? ?????? Hollow Fibre
• ??????????????? ?????????

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?????????????

• ?????????????? i ??? ???? j ?????????
• ????????? (Recovery)

(2)
S Qp / Qf
???????????????? ????????
(3)
(4)
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?????????????

• Assume ?????????????? feed ??? permeate ?????????
  ???????????????? i ???????????

(5)
(6)
(7)
?????? PR Pf/Pp ???????????????????????????
(8)
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????? 2

• ??????????????????????????????????????????????????
  ?????????? ????????????????????????????? 1 ?m
  ??????????????? 2.5 ???? ???????????? 0.5 ????
  ???????????????? 36 m3(STP)/h ????????????????????
  ???????????? CO2 ??? N2 ???? 81 ??? 5.3 Barrer
  ???????? ????????????????????????????
  ????????????? (Recovery) ????????? ??? CO2
  ???????????????? CO2 ?????????????? 0.2

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????? 3

• ????????????????????????????? 10 m3/hr
  ?????????????????????????????????????? 30
  ?????????????????????????????? ???????????????????
  ? PDMS ???????????? 1 ?m ?????????????????????????
  ?? 600 Barrer ????????? ? (O2/N2) 2.2 ?????
  Pf 1 Bar ?? Pp 0.2 Bar ???????????????????????
  ?????????????????????

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????????????????????

• ???????????????? 93 ???? 98
• ??? Methane Recovery yiRQR/yifQf
• 90.2

Feed Retentate Permeate
Components ( Mol) - CH4 - CO2 Flow Rate (MMSCFD) ??????? Psig 93.0 7.0 20.0 850 98.0 2.0 17.11 835 63.4 36.6 2.89 10
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????????????????????
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???????????????????????? (???????????????? Feed
970 psi)
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??????????????????????????
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????????????????????????????????????
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?????????????

• ??? Single-Stage ????? VOC ????? 0.1

??? Two-Stage ?????????????????? 0.01
?????????????????????????????
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?????????????
??? Two-Stage ????????????? VOC ??????????
?????????????????????
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?????????????
??? Recycle ????????????? VOC ??????????
???????????????? 50
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?????????????
??? Membrane-Condenser - ?????????????????????????
?????????
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Process Design

• 3 Factors ??????????????
• Selectivity ????????????
• Pressure Ratio ???????????????? PR Pf/Pp
• Recovery ???? Stage cut
• ?????????????????? (A)

S Qp / Qf

He H2 CO2 C2H4 O2 N2 CO CH4 C2H4
2.6 2.89 3.3 3.9 3.46 3.64 3.76 3.9 4.3
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Applications

• Hydrogen Separation
• ????????? 1980 ????????? Monsanto ????????
• ?????? H2 ??? CO/ CH4 / Natural Gas
• ????????????????????? (Glassy State) ?????
  Selectivity ??????

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??????????????????????????????????
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??????????????????????????????????
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Applications

• 2. Oxygen/Nitrogen Separation ???? Application
  ?????????????? ??????? N2
• ????????? Selectivity ??? ??????????? trade-off
  ?????? permeability ????

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Robesons Boundary
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??????????????? 99
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Applications

• 3. Natural Gas Purification ??? CO2 ??? H2S
  ??????????????????
• ???????????????????? ?????????????????????????????
  ???????????

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??? CO2 ??????????
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?????????????????????????????
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Publications

• 1. On the limits of gas separation in CO2/CH4,
  N2/CH4 and CO2/N2 binary mixtures using
• polyimide membranes
• 2. Mixed-matrix membranes containing MOF-5 for
  gas separations
• 3. The fabrication of hollow fiber membranes with
  double-layer mixed-matrix materials for
• gas separation
• 4. Polymeric CO2/N2 gas separation membranes for
  the capture of carbon dioxide from power plant
  flue gases
• 5. A parametric study of CO2/N2 gas separation
  membrane processes for post-combustion capture
• 6. Biogas, membranes and carbon dioxide capture
• 7. The effects of water vapor on the separation
  of methane and carbon dioxide by gas
• permeation through polymeric membranes