Separation- A key technology towards the hydrogen economy?towards the hydrogen economy?
C t K d dCosta Komodromos and Ashok K. Bhattacharya
University of OxfordDept. of Engineering SciencesParks RoadOxford OX1 3PJUKUK
University of Oxford
Structure of the presentationStructure of the presentation
• NATURALHY ProjectNATURALHY Project
• Separation technologies
• NATURALHY approach
• Status
• Future
University of Oxford
NATURALHY ProjectNATURALHY Project
Smooth, rapid introduction of
Main political drivers towards H2
, phydrogen to end-users by using existing widespread NG network system to distribute mixtures of
•Energy security
•Reduction of CO2 emissions (Kyoto ≥8% by
NG and H2
emissions (Kyoto ≥8% by 2010)
•Improvements in regional air quality
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Value of MixturesValue of Mixtures
• Reduction of CO2 emissions (greening of gas)(g g g )
• 1% of NG energy replaced by CO2-free H2 results in a reduction of 9Mt/y CO2 in the EU-25 countriesreduction of 9Mt/y CO2 in the EU 25 countries
• Potential of pure hydrogen delivery by H2 separation
• Offering hydrogen producers a connection to end-users
• Using existing system avoids investment in completely new infrastructure
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Hydrogen Local centresH2
High pressure system, 64-40
Medium pressure system 40 8 bar
Distribution system, <8 bar
End user infrastructure
End user appliance
system, 64 40 bar
system, 40-8 bar
MM M
H2 H2
H2 H2
Industrial d
Industrial
H2
end user end user
-Pressure reduction facility
M - H2 membranesIndustrial end user
Separation of HydrogenSeparation of Hydrogen
• Pressure swing adsorption (PSA)Pressure swing adsorption (PSA)• Membranes
Gas separation by adsorption processes widely used in
•Petrochemicals
•Biochemical
•environmental technology•environmental technology
•oil and gas industries.
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Pressure Swing Adsorption
Advantagesg• Well-established commercially, especially in natural gas systems and refineries•Fairly high purity H2y g p y
Disadvantages•Only 80-90% of H2 is recovered y•Higher purity H2 product requires more energy (more freq. switching) •Mechanically more complex – switching beds•Higher energy usage than filters / membranes•Higher capital cost
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Membrane principleMembrane principle
Sweep gas (co- or counter current)
H2H2Membrane
Permeate side
Heat 2
Retentate side
H2 rich H2 lean
eat
H2 rich 2
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Why Membrane Separator Development?Why Membrane Separator Development?
• Commercial systems problematic -expensive
• Capitalise on cost advantage for smaller scale operations
R l t t ifi ti d b t• Relevant to purification and membrane reactors
• Improvements in cost and reliability needed
• Need to link membrane development with packaging for process needs
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Programme objectives g j
Objectives
To develop high selectivity Pd based thin– To develop high selectivity Pd based thin membranes for Hydrogen separation from natural gas mixtures
– To examine performance envelope, packaging and system issues
– To develop low cost carbon based membranes
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Palladium Membranesa ad u e b a esAdvantages
• Simple, no moving partsSimple, no moving parts
• Pure H2 product
Modular for scale up• Modular for scale up
• Potential for lowering costs
• However, Still in development
– Relatively low flux – large membrane area required– Palladium (most common) is very expensivePalladium (most common) is very expensive– Contaminants (sulphur, other components)– Low outlet H2 pressure– High operating temperatures (>400C)
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Typical lab permeator (Univ Oxford)Typical lab permeator (Univ Oxford)
Early sampley p
• 8 µm Pd membrane supported on ceramic substrateon ceramic substrate
• Graphite seal• 13 mm o.d x 120mmlength• Sep factor>50:1 (~99%)• Sep. factor>50:1 (~99%)• Further development of ceramic
will allow thinner membranes (2-3 µm ) with separation ( µ ) pfactor>1000:1(>99.9%)
U i it f O f dUniversity of OxfordUniversity of Oxford
Scale up issues for Pd membranes
Flux Use Pd based alloys e.g. Pd/AgVery thin films of Pd on porous supports
Cost Price of Pd is ~$650/ounce (April, 2007)Thickness of Pd film will be <2μm for $500-1000/m2$500-1000/m2
Poisoning by process
Unsaturated hydrocarbons, H2S, COShould be regeneratable in steam or air
stream impuritiesg
Embrittlement Resistance to thermal cyclingα β (α’) phase transitionα β (α ) phase transition
Leak free sealing Supported membranes
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Pd membrane
High resolution SEM of substrate support for Pd alloys
10μm sol gel coating
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How do we address these problems?
■ Cost– thin films of Pd on hydrogen-porous supports– minimize Pd film thickness
■ Poisoning– remove most H2S up frontremove most H2S up front– PdCu40 is sulphur resistant
■ Embrittlement– Pd alloys reduce distortion upon
hydriding/dehydridingy g y g
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Technical ApproachTechnical Approach• Thin Pd films on supports:
• Challenge is to produce perfect defect free film very• Challenge is to produce perfect defect free film –very difficult
• Role of support is crucial• Defect free supports problematicpp p• Electroless plating OK for Pd but not for Pd/Ag and
Pd/cu alloys
F Pd ll S tt i th d b iFor Pd alloys Sputtering methods being investigated
• Deposit thin coherent film of Pd/Ag on defect free supportsupport
• Silicon wafers and ultra-fine filter materials used • Deposit on substrate, seal and manifold
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CMS FormationCMS Formation
+ MeSalt/MeO
200-800˚C100
120
Sample: HC + 4% CuN 750CSize: 17.2210 mg TGA
File: C:...\Experimental\TGA\HC+4%CuN750C.001Operator: DRGRun Date: 2006-03-03 16:13Instrument: TGA Q500 V6.4 Build 193
6
8
Sample: HC + 4% CuN 750CSize: 17.2210 mg MS
File: C:...\Experimental\TGA\hc4cu750b.taiOperator: DRGRun Date: 3/3/2006 17:13Instrument: Mass Spectrometer
60
80W
eigh
t (%
)
0
2
4
Ion
Cur
rent
(nA
)
0 20 40 60 80 100
Time (min) Universal V4.1D TA Instruments
20
40
W
L l B0
0 200 400 600 800
Temperature (°C) Universal V4.1D TA Instruments
Levoglucosan Benzopyrene
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CMS Mixed Gas Results (30% H2 in CH4)
Material Test TempoC
Test feed pressure bar
H2 permeability Barrer
Selectivity
H2 permeanceM3(STP)/m2.h e bar h (12 microns)
HC+Cu 550oC 90 4 1502 679 0.34
HC+Cu 650 oC 30 2 700 181 0.16
HC+cu 650 oC 30 6 648 541 0.15
HC+Cu 650 oC 80 2 1230 218 0.28
HC+Cu 650 oC 80 6 1155 532 0.26
• Insensitive to pressure in the application range (2-6 bar)• Significant increase in permeability with temperature• Significant increase in permeability with temperature• 80% H2 recovery, >90% purity possible at 30 C
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SEM of hollow carbon membraneChallenge is to achieve close control of the pore tailoring and carbonization procedures. Work is focussed on making defect free larger membranes or hollow fibres (NTNU)
Temperature programmed furnace SEM f h ll b fibp p gfor carbonization of precursor films SEM of hollow carbon fibre
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Summary Palladium Alloy MembranesPalladium Alloy Membranes
• Most cost effective for small scale production• Most cost effective for small scale production• Cost depends on flux obtained/unit area• Flux is function of (thickness, partial pressure drop,
temperature poison concentration)temperature, poison concentration)• Need very thin membranes • Typical results for 5 microns from 65% H2 in CH4 at
5 b d 450oC i 17 3/h / 25 bar and 450oC is 17 m3/hr/m2
• Target is reliability in thin films pin holes, thermal/mechanical stress, poisons
S t t i l iti l • Support material critical • Need to consider issues of packaging
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SummarySummary• Thin Pd based membranes offer potential but
h i ll h ll itechnically challenging
» work at relatively high temperatureid h d» provide pure hydrogen
• Carbon based membranes: low cost with good flux, work at relatively low temperaturework at relatively low temperature
• Separation system may involve both types
• Packaged systems