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

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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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Experiments with H S and THT in CHExperiments with H2S and THT in CH4CETH

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Carbon based membranesCarbon based membranes

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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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Packaged Pd membraneg

CETH examining packaged concepts

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Process DesignProcess Design

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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