Membrane Reactor for
Hydrogen Production
AIChE 2008 Annual Meeting, Philadelphia, PA
Ashok Damle
Jim Acquaviva
Pall Corporation
November 17, 2008
Photo courtesy of
Pall Corporation
This presentation does not contain any proprietary or confidential information
Contributors & Acknowledgments
• Pall Corporation
–
–
–
–
–
–
–
–
Scott Hopkins
Daniel Henkel
Rick Kleiner
Rajinder P. Singh
Hongbin Zhao
Keith Rekczis
Chuck Love
Kevin Stark
• Colorado School of
Mines
– J. Douglas Way
– Oyvind Hatlevik
• RTI International
– Carrie Richardson
• DOE (EERE)
– Sara Dillich
2
Presentation Outline
• Drivers for Hydrogen Production and CO2 capture
• Process intensification / Membrane reactor concept
• Status of Pd-alloy composite membrane at Pall
• Inorganic substrate development
• Composite Pd-alloy membrane development
• Membrane reactor model simulations
• WGS Membrane reactor experimental studies
• Pall’s capabilities and future activities
3
Hydrogen Economy and Production
Two major drivers for hydrogen production
• Hydrogen as energy carrier – Transportation,
Power/heat generation, and Chemical production
• Pre-combustion CO2 capture and hydrogen production
has potential to reduce GHG emissions
Hydrogen Production
• Can be produced from multiple pathways – natural
gas, coal, biomass and renewables
• Near term hydrogen production from Natural Gas
• Longer term hydrogen production from Coal and
renewable energy sources (biomass, solar, wind)
4
Conventional Hydrogen Production
Exhaust
Natural
Gas
Air
Hydrogen
Product
400 oC
800 oC
Syngas
Generator
WGS
Current State:
PSA
Residual Gas
> 90 % of H2 is
produced from
NG by this
process
Very efficient
on large scale
Water
Future State:
Combining hydrogen generation and separation (process
intensification) can potentially reduce capital and
operating cost of hydrogen production at various scales
5
WGS Membrane Reactor Process
Exhaust
Hydrogen
Product
Natural
Gas
800 oC
400 oC
Air
WGS Membrane
Reactor
Syngas
Generator
Residual Gas
Water
• Increased conversion due to equilibrium shift
• Compact system, smaller footprint
• Simpler operation and lower operating/energy costs
• Need compressor for high pressure hydrogen product
6
Membrane Reformer Process
Exhaust
CO2
Hydrogen
Product
Steam
Natural
Gas
Air
600 oC
Membrane
Reformer
Residual
Gas
Efficiency
improvement
through
process
intensification
Water
Compact unit, smaller footprint
Milder conditions
Increased hydrogen yield
Less steam
Lower capital cost
Greater energy efficiency,
Lower cost of H2 production
Need high temperature inorganic membrane for H2 separation
7
Why Palladium Membrane ?
1.
10
-9
5
10
10
-7
-6
10
10
-5
0.0001
CSM PdAu
(7)
2.
4
10
3.
(7)
CSM Pd
4.
(1)
1000
(4)
5.
(2)
100
(3)
6.
10
Polymeric Membrane Materials
Inorganic Membrane Materials
2
2
H /N Ideal Separation Factor
10
-8
1 -9
10
10
-8
10
-7
7.
(6)
-6
10
10
-5
2
H Permeance (mol/m .s.Pa)
2
0.0001
Lee, D., Zhang, L., Oyama, S. T., Niu,
S., and R. F. Saraf, J. Membr. Sci., 231,
117(2004).
Kajiwara, M., Uemiya, S., Kojima, T., and
E. Kikuchi, Catal. Today, 56, 65(2000).
DeVos, R. M. and H. Verweij, Science,
279, 1710(1998).
Hassan, M. H., J. D. Way, P. M. Thoen,
and A. C. Dillon, J. Membr. Sci. , 104,
27(1995).
Polymer line from :
Robeson, L. M., J. Membr. Sci., 62,
165(1991).
Wu, J. C. S. et al., J. Membr. Sci., 77,
85(1993).
Hatlevik, Ø., Gade, S. K., Keeling, M. K.,
Thoen, P. M. and J. D.Way, "Palladium
and Palladium Alloy Membranes for
Hydrogen Separation and Production:
History, Fabrication Strategies, and
Current Performance," submitted to
Separation and Purification Technology,
Sept. 2008.
Graph courtesy of Prof. Doug Way and CSM group
8
Pd-alloy membrane development
Self supporting membrane structures
• Need membrane of sufficient thickness for
structural integrity and strength e.g. tubes or flat
sheets > 25 µm
• Expensive, Niche applications – small H2 purifiers
Composite membrane structures
• Thin films on substrates
• Substrate provides structural integrity and strength
• Deposition of thin Pd-alloy films by various
techniques ~ 1 – 5 µm
• Better seals for High T – High P applications
• Lower cost – thin Pd layer, less membrane area
9
Pd-alloy membrane development at Pall
Components of a Composite Membrane
1) Porous stainless steel
– Provides mechanical support that
can withstand the operating
conditions of the process
– Critical features: permeability,
weld configuration, mechanical,
thermal and chemical
compatibility
2) Diffusion barrier
– Enables formation of functional
layer
– Critical features: surface
properties, material, gas
permeability, number of defects
3) Pd alloy membrane
– Functional layer provides for
gas separation
– Critical features: thickness,
alloy composition, durability
and number of defects
3
2
1
Excellent adhesion to zirconia layer, uniform thickness,
and surface contour following of Pd-alloy metal film
10
Pd-alloy membrane development at Pall
Ceramic / PSS composite substrate for Pd alloy membranes
It’s all about the substrate
Porous stainless steel tube with
ZrO2 ceramic coating: Extensive
development work done to
optimize the composite structure
and surface properties to enable
formation of a high quality Pd alloy
or other functional layer.
PSS
Medium
Ceramic
Coating
• All welded design
No polymer seals, Higher temp. capabilities
• Thermal expansion
Uniform thermal expansion with the housing
and module components
• Cost
All metal design with welded fittings, allows
for direct welding to a tube sheet. This
eliminates the need for intricate sealing
mechanism and reduces overall module cost
11
Pd-alloy membrane development at Pall
Durability : Pall Gas/Gas separation supports have been
exposed to multiple thermal cycles with no detrimental
effects to the composite structure
– Ceramic layer stable and maintains adhesion to metallic
substrate through thermal cycles
– Composite tube with 310SC can be used up to 550 oC in
pure H2 and up to 400oC in air or inert gases
Characterization Data of Composite Support
First bubble in IPA is > 30 psi
Air permeability @ 1000 cc/min ~ 7 psi
Zirconia coating pore structure is 70 nm
Base metallic tube pore structure is 2 microns in
average
12
Pd-alloy membrane development at Pall
75 cm2 active surface area
!
" #
$
#
$
% $
&
15 cm2 active surface area
#
'(
$ )
13
Membrane Durability in Thermal Cycling
Thermal Cycle: Air
Temperature (C): 25
Pressure (psig): 0
Air
400
20
Argon
400
20
Hydrogen
400
20
Air
25
0
14
Components of a Gas/Gas Separation Module
Pressure vessel
with fittings
Non-porous
end fitting
Weld
Porous
substrate
Internal
hardware
Membrane tube
sub-assembly*
Welds
* Pd alloy membrane not shown, typically on the OD of the tube
15
Membrane Reactor Model Simulations
Fuel Gas
with Steam
Membrane
Fuel Reforming/WGS Catalyst
Residual Gas
H2
H2
Permeate Hydrogen
Model Assumptions
• Temperature and total pressure constant on both sides
• Reaction kinetics faster than hydrogen permeation
• Feed side is in dynamic equilibrium
• Hydrogen flux determined by local driving force
16
16
WGS Membrane Reactor Experimental Results
100
Methane
Reformate
Feed Gas (Dry)
H2 - 75.2%
CO - 15.6%
CO2 - 7.1%
CH4 - 2.1%
90
CO Conversion, %
80
70
Steam:CO = 1.2:1
Temperature - 375 oC
Feed Pressure - 100, 150 psig
High Temp. Fe-Cr WGS Catalyst
(Sud-Chemie - Shiftmax 120)
Model Prediction
(Fast Kinetics)
60
50
40
Equilibrium CO Conversion
at Feed Gas Conditions
30
Experimental Data
100 psig
150 psig
20
0
10
20
30
40
50
60
70
80
90
100
Net Hydrogen Recovery, %
Demonstrated > 80% Net Recovery of Hydrogen with >80% CO conversion
Experiments conducted by Damle at RTI International – Fuel Cell Seminar 2007
17
Predicted Methane Conversion increase
@ T – 600 C, Steam:C::2:1, P-100, 250 psig
Effect of Pressure – Greater H2 recovery and yield
in spite of unfavorable equilibrium
18
Membrane Reactor Performance
@ T – 600 C, Steam:C::2:1, P-100 psig
Recovery of sensible and combustion heat of Residual Gas
Net heat requirement analysis
19
Membrane Reactor Performance
@ T – 600 C, Steam:C::2:1, P-250 psig
Effect of Pressure – Greater H2 partial pressure
Less Membrane Area requirement
20
Membrane Reactor Performance
@ T – 600 C, Steam:C::3:1, P-100 psig
Higher Steam:C ratio – Greater H2 partial pressure
Less Membrane Area requirement
Relatively small energy penalty
21
Membrane Reactor Performance
@ T – 550 C, Steam:C::2:1, P-100 psig
Lower Temperature – Lower H2 partial pressure – less conversion
(strong effect)
Low hydrogen recovery
22
Components of Economic Analysis
NG reformer
Process
Model
Process
Data
Membrane
Reactor Model
Membrane
Pilot Plant
Performance
Measurements
Su
rfa
ce
Ar
ea
Hydrogen Permeate Flow
Economic Model
Membrane
OPEX & CAPEX
PSA
OPEX & CAPEX
Energy Model
n
sio
s
re
mp ost
o
C
C
Compressor
OPEX & CAPEX
H2 Cost
($/gge)
23
Potential Benefits of Membrane Reactor
Basis: 100 Kg/day (1650 SCFH)
• Membrane module area ~ 10 ft2
• Membrane Module cost with DOE Target ~ $7,500
Cost of metal ~ $ 235 (October 2008 prices)
• Capital cost reduction by replacing PSA/WGS ~ $ 40,000
• DOE H2A Forecourt Model – Capital cost portion ~ $3.06/kg H2
• Potential reduction in capital cost contribution ~ $0.36/kg H2
• Penalty for 50% additional compressor cost ~ $ 0.08/kg H2
• Additional benefits not yet quantified
– Increased hydrogen yield
– Reduced operational cost
– Reduced energy costs
24
Future R&D Needs – Reduce Cost
Capital Cost
•
•
•
•
•
High flux membrane to reduce required membrane area and pressure
vessel size
High efficiency modules to maximize use of membrane area
Commercial scale manufacturing process for Pd alloy membranes
Process integration to reduce balance of plant cost
Process intensification (ex: membrane reactors) to minimize catalyst
and hardware cost
Operating Cost
•
•
High separation factor membranes that maximize H2 recovery
Process integration to minimize the energy penalty for CO2 capture
Maintenance Cost
•
Durable palladium alloys that can tolerate severe process conditions,
abrupt startups & shutdowns, and contaminants in feed streams
25
Scale-up of Metal Tube Technology
Research
Development
Commercialization
26
Questions ?
27