Opportunities for Gas Separation Technology in the Clean Energy Field

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Opportunitiesfor Gas Separation Technologyin
the Clean Energy Field

• Bowie Keefer
• Clean Energy Research Seminar
• 25 February 2009
• Clean Energy Research Centre, UBC
• G4 Insights Inc.

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Motivation

• Clean energy systems will achieve higher
  efficiency, extend fossil resources, avoid
  noxious emissions, and reduce the risks of major
  adverse climate impacts from global warming.
• Gas separation has key roles in advanced fuel
  processing and energy conversion systems.

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Engineering Ingredients

• Applied physical chemistry
• Materials science
• Thermofluid dynamics
• Contactors for heat and mass transfer
• Process intensification and integration
• Fluid machinery
• Unified and multidisciplinary approach

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Main Gas Separation Applications for clean energy
systems

• Oxygen generation
• Fuel processing
• Petroleum refining
• Coal or biomass gasification or hydrogasification
• Methane upgrading
• Hydrogen production and recovery
• CO2 capture
• Advanced fuel cell power plants

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Oxygen Generation

• Cryogenic distillation
• Pressure/vacuum swing adsorption
• Polymeric membranes
• High temperatureta ceramic membranes
• Chemical looping

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CO2 Capture

• Thermal Power Plants
• Post-combustion capture consider QuestAir VSA
  for CO2 capture, advanced CO2 adsorbents.
• Oxyfuel combustion consider QuestAir O2 for
  25-30 power saving relative to cryogenic air
  separation.
• Precombustion capture sorption-enhanced water
  gas shift reactor for high temp CO removal.
  Integrations with SOFC.

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Gas Separation Technology Development is an
active and competitive field with many
opportunities!

• Absorption
• Chemical solvents (e.g. amines) with thermal
  swing regeneration
• Physical solvents (e.g. Selexol) with pressure
  swing regeneration
• Chemical looping
• Mineral sorbents (e.g. CaO) with thermal swing
  regeneration
• Adsorption
• Adsorbents (e.g. active carbons or zeolites) with
  pressure swing (PSA) or thermal swing (TSA)
  regeneration
• Membranes
• Pressure or electric current driven, selective
  permeation of oxygen, hydrogen or CO2
• Cryogenic distillation

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PSA Process Overview
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Evolution of PSA TechnologyQuestAir Technologies
program
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Emergence of Compact PSA Technology
Conventional Hydrogen PSA
QuestAir Rotary Hydrogen PSA device

• Compact PSA technology
• Structured adsorbent
• Rotary valve technology

• Pressure Swing Adsorption (PSA)
• Established method of gas separation
• Used in large industrial applications

(Note the author is the original founder of
QuestAir Technologies Inc.)
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Working Principle of Compact PSA
Structured adsorbent cells in adsorber rotor
Product H2
Purge
Designed to minimize size and power
requirement. Several potential equipment options
depending on the application requirements
Rotary valve faces
Exhaust CO2
Feed H2 CO2
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Compact PSA for CO2 Concentration
Purge - PSA/VSA product - TSA cathode exhaust
air
Product - H2 purity as
desired
Heavy reflux is recirculation of the more
strongly adsorbed fraction (e.g. CO2) to rinse
less strongly components from the adsorbers,
increasing both CO2 product purity and H2 product
recovery.

Exhaust CO2 product
Feed - H2, CO, CH4 - CO2, H2O
Heavy reflux
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Methane-CO2 Separation
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QuestAir Industrial H2 PSA Plant
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Compact Oxygen PSA Unit

• Separates concentrates oxygen from air feed
  stream
• Higher purity of reactant increases fuel cell
  power density
• Volume 14 Liters
• Capacity 500 kg/day O2 delivered at 70 O2
  purity
• Sufficient oxygen flow for 50 kW SOFC

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Compact Pressure Swing Adsorbers for the CO2
Separation Module
50 kW
150 kW
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Hydrogen Recovery in RefineriesQuestAir twin
module rapid cycle rotary PSA
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Transportation Energy

• In a highly competitive field, successful
  innovation and entrepreneurial determination
  will help select between different pathways.
• Examples
• Hybrid ICE vehicles (highly successful launch)
• Hydrogen fuel cell vehicles (attempting launch)
• SOFC hybrid vehicles (potential dark horse)
• ICE Internal Combustion
  engine
• SOFC Solid Oxide Fuel Cell

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Low temperature H2 Fuel CellsversusHigh
temperature SOFC

• Hydrogen for fuel cell vehicles is most
  economically produced by steam reforming of
  hydrocarbon fuels such as natural gas, gasoline,
  methanol or DME.
• System efficiency of low temperature hydrogen
  fuel cells is compromised by energy requirements
  for fuel processing and compression to store the
  hydrogen.
• SOFC working temperature is high enough for fuel
  processing by high grade waste heat directly
  recovered from the fuel cell.
• Internal reforming SOFC power plants can run on
  many conventional hydrocarbon or alcohol fuels
  rather than H2.

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SOFC for Propulsion Power?

• Vehicular applications require robustness under
  severe climate, environmental, shock, vibration
  and cyclic duty conditions.
• SOFC stack materials science must still overcome
  major challenges to establish durability.
• SOFC developers have been working on vehicle
  auxiliary power units (APU) which would need to
  satisfy similar durability.
• Successful SOFC APU development could trigger
  initial use of SOFC vehicle propulsion engines as
  range extenders on plug-in hybrids.
• Subject to satisfactory stack life expectancy,
  future SOFC engines may be used in heavy duty
  applications in highway, rail and marine
  transport.
• Watch this game-changing technology for moving
  the efficiency goalposts!

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Basic Approach
Purpose Apply advanced gas purification
technology to improve efficiency, performance and
cost competitiveness of SOFC systems Specific
Objectives

• Recover and recycle hydrogen at anode
• Improve steam and heat management
• Maximize electric power output
• Wide range load-following and turndown
• Simplification and cost reduction

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Conventional SOFC power plant
Anode recycle
Pre-reformer
Anode
SOFC
Fuel
Cathode
Burner
Air Blower
Heat Recovery
Fairly high efficiency from hydrocarbon fuels,
but excess heat production which cannot easily be
recovered in small power plants
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Hybrid SOFC-GT power plant
Anode recycle
Pre-reformer
Anode
SOFC
Fuel
Cathode
Burner
Generator
Gas Turbine
Can achieve high efficiency in large power plants
with simple fuels
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Enriched H2 Recycle SOFC power plant
Anode recycle
Pre-reformer
CO2 Separation Module
Anode
SOFC
Cathode
Thermal Recuperation
Blower
CO2 and Excess H2O
Hydrocarbon Fuel
Feed Air
Exhaust Air
Less heat generation, more electrical output and
highest efficiency even for quite small power
plants
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Gas Separation Benefits for SOFC

• Hydrogen recycle raises hydrogen concentration
  throughout anode
• Lower steam to carbon ratio without coking
• Possible elimination of steam at inlet
• Less steam and greater H2 concentration increases
  cell voltage, current and fuel utilization
• More power and less heat produced
• Internal reforming reaction is delayed and anode
  gas composition is more uniform
• Less thermal gradient less thermal stress

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H2/O2 Fuel Cell Ideal Potential
TDS
H2 ½ O2 ? H2O(g)
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Basic Thermodynamics
for hydrogen as fuel, n 2
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Calculated Effect on Polarization Curve
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Calculated Effect on Open Circuit Voltage H2
Recycle
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Modeling of Alternative SOFC Systems

• Alternatives considered
• Case 1 conventional unpressurized SOFC system,
  fuel utilization 85.
• Case 2 enriched hydrogen recycle with SCA (Sweep
  gas purged Cyclic Adsorption) for CO2 transfer
  from anode exhaust to cathode exhaust air, fuel
  utilization 96.
• Case 3 enriched hydrogen recycle with VSA
  (Vacuum Swing Adsorption) for CO2 separation and
  concentration, fuel utilization 95.5.

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Case 2 Atmospheric SOFC Rotary Adsorber with
cathode exhaust purge
Anode Exhaust
Fuel
Steam
Condenser
Pre-reformer
Water gas shift reactor
Anode
SOFC
Blower
Cathode
Water
QuestAir C-7100Rotary Adsorber Module
Blower
Exhaust CO2 in air
Air
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Case 3 Low pressure SOFC and QuestAir VSA with
heavy reflux
Recycle or H2 Export
Fuel
Steam
Condenser
Pre-reformer
Water gas shift reactor
Anode
SOFC
Blower
Cathode
Burner
Water
Tail Gas
QuestAir VSA
Air
Heat Recovery
Heavy Reflux
Optional Reflux Compressor
Pure CO2
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SOFC Power Density versus Voltage

• Legend
• Case 1 conventional SOFC without enriched
  hydrogen anode recycle
• Case 2 SOFC with anode recycle by QuestAir
  compact SCA transferring diluted CO2 to cathode
  exhaust
• Case 3 SOFC with anode recycle by QuestAir
  compact VSA delivering purified H2 and enriched
  CO2 product streams. Vacuum pump efficiency
  50, including electric motor drive.
• Case 3A As Case 3, but vacuum pump efficiency
  60.

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Cell Voltage versus SOFC Power Density
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Power Plant Efficiency versus Power Density
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Excess Heat versus Power Density
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Potential Applications in SOFC Systems

• Distributed CHP and remote power
• Improved efficiency and heat distribution
• H2 cogeneration for residential refuelling
• Mobile and transportation power plants
• Highest efficiency from hydrocarbon fuels
• Load-following and turndown
• Minimal high grade thermal emission in cruise
  mode
• Larger power plants
• High efficiency ( 75 LHV)
• CO2 sequestration
• H2 or syngas cogeneration

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Future Central Power Generation

• Enriched hydrogen recycle boosts SOFC efficiency
  and enables pre-reforming or hydrogasification of
  the fuel feedstock.
• For solid fuels, high pressure hydrogasification
  minimizes oxygen requirement and generates
  methane.
• Methane in feed to SOFC is desirable for stack
  cooling and heat recovery by endothermic internal
  reforming.
• Hydrogen may be a cogeneration product with
  electricity and CO2.
• Auxiliary turbine expanders may drive compressors
  and other auxiliary loads including compression
  of captured CO2.

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Enriched H2 Recycle SOFC power plant with
Hydrogasification of Coal or Biomass
Anode recycle
Hydrogasifiier
CO2 Separation Module
Anode
Solid Fuel (coal or biomass)
SOFC
Cathode
Char
Char Gasifier
ASU
Gas Turbine
CO2 and Excess H2O
Exhaust Air
Ash
Feed Air
Optional O2 enrichment to cathode air feed
Less heat generation, more electrical output and
greater efficiency
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The Key Role of Hydrogen within advanced energy
conversion systems(but less promising as a
merchant fuel commodity!)

• Some examples
• Solid oxide fuel cell (SOFC) with hydrogen
  enriched anode recycle loop
• Hydrogasification of biomass or coal
• Decarbonization of natural gas or integrated
  gasification syngas in combined cycle power
  plants.

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Future Outlook

Let a hundred flowers bloom, let a hundred
schools of thought contend.
Mao Tse-Tung
G4 Insights Inc.