On-Line H2 PPB Impurity Analysis Using FTIR

On-Line H2 PPB Impurity Analysis Using FTIR

Arik UltschMKS Instruments Deutschland

Background

Volatile fossil fuel prices have created interest in Hydrogen as a new energy source for the auto industryImpurities in H2 fuel directly affect the longevity of the combustion or fuel cell engineRegulatory agencies have initiated an H2 quality threshold at the ppb levelFTIR spectroscopy is the most viable method of providing ppb level H2 impurity detection on-site at the pump

H2 Impurity Analysis: Content

Fuel cell principleDetermining the effect of impurities on fuel cells– How much can be tolerated?– Is the effect reversible?– Effects of impurities

Sulfur (H2S, COS), ammonia, CO, CO2, H2O– Impurities from H2 Fuel as well as Air Feed

Cell Analysis by Air Liquide R&D Center USARobert Benesch, Tracey Jacksier, and Sumaeya Salman

FTIR Validation for H2 impurity detection– Method detection limits for:

Multiple componentsDifferent FTIR detector ranges tested

Fuel cells generate electricity from a simple electrochemical reaction in which oxygen and hydrogen combine to form waterAnode– Porous carbon coated with tiny particles of platinum (Pt) – Pt acts as a catalyst to form ions

(2H2 => 4H+ + 4e-)

Proton Exchange Membrane (PEM)– Allows positively charged

ions to travel through

Cathode– Forms oxygen atoms – Oxygen and hydrogen

combine to form water(O2 + 4H+ + 4e- => 2H2O)

Fuel Cell Principle

Impurity Effects on Cell Voltage

Decrease in performance– Affect different physical and chemical processes

Removal of impurity– Cell Performance: recoverable or non-recoverable

The Fuel – Hydrogen and Air

Hydrogen– Introduced to anode side of fuel cell

Reducing environment– Dependant upon production method

Typical methods- Biological – fermentation, anaerobic digestion- Electrochemical – electrolysis of H2O- Thermal – reforming, gasification

Steam Methane Reforming (SMR)- 95% of US H2 production- He, N2, CO, H2S, NH3, CH4 …

Air– Introduced to cathode side of fuel cell

Oxidizing environment

Sources of Impurities

Carbon Monoxide in H2– Reported Mechanism*

Physical adsorption onto fuel cell catalystCO absorbs onto Pt site blocking H2 adsorption

* J. Baschuyuk and X. Li, “Carbon Monoxide Poisoning of Proton Exchange Membrane Fuel Cells”; Int. J. Energy Res. 2001, 25; 695-713

adssg COPtPtCO ⋅⇔+−+ +++→+⋅ eHCOPtOHCOPt

gsads 2222

CO Effect on Fuel Cell

1.0 and 4.5 ppm CO in H2

9.2 ppm CO in H2

Sources of Impurities

Ammonia in H2– Reported Mechanism*

Concentration and exposure dependantShort-term exposure of trace concentrations (~<10ppm)

- Reversible- Mainly affects the Electrode

Long-term exposure of trace as well as high concentrations (~>40ppm)

- Non-Reversible- Mainly effects the Membrane structure

* F. Uribe, S. Gottesfeld, T. Zawodzinski, “Effect of Ammonia as Potential Fuel Impurity On Proton Exchange Membrane Fuel Cell Performance” J. Electrochemical Society, 2002, 149 (3) A293-296

NH3 Effects on Fuel Cell

0.5, 1.0 ppm NH3 in H2No Effect

9.0, 44.7 ppm NH3 in H29.0 Non - Reversible44.7 Non - Reversible

pure H2

Summary of Impurities Tested

Typical Air Sample: (maximum hourly concentration detected at EPA testing sites in Houston and Chicago area in 2005):

CO [3 ppm], NO [0.65 ppm], SO2 [0.137 ppm]

Impurity Electrode Lowest Test Conc (ppm)

Highest Test Conc (ppm)

% Decrease at Lowest

Conc

% Decrease at Highest

Conc CO anode 0.52 9.2 5 >58 H2S anode 0.10 2.0 not detected >58 NH3 anode 0.50 44.7 not detected 14.7 CO cathode 0.40 68.6 not detected not detected SO2 cathode 0.07 4.8 3 40 NO2 cathode 0.025 2.86 not detected 20

Current H2 Fuel Cell Specification SAE J2719

Property Value Unit Limit 1 Ammonia 0.1 ppm v/v Maximum 2 Carbon Dioxide 2 ppm v/v Maximum 3 Carbon Monoxide 0.2 ppm v/v Maximum 4 Formaldehyde 0.01 ppm v/v Maximum 5 Formic Acid 0.2 ppm v/v Maximum 6 Helium 300 ppm v/v Maximum 7 Hydrogen Fuel Index 99.97 % (a) Maximum 8 Nitrogen and Argon 100 ppm v/v Maximum 9 Oxygen 5 ppm v/v Maximum

10 Particulate Concentration 1 µg/L@NTP (b) Maximum 11 Particulates Size 10 µm Maximum 12 Total Gases 300 ppm v/v (c) Maximum 13 Total Halogenated Compounds 0.05 ppm v/v Maximum 14 Total Hydrocarbons 2 ppm v/v (d) Maximum 15 Total Sulfur Compounds 0.004 ppm v/v Maximum 16 Water 5 ppm v/v Maximum

FTIR For H2 Impurity Analysis

Real-time analysis at ppb levelsFTIR advantage – Multiple components analysis with one unit

Single analyzer for all the impurities except O2, H2, Ar, N2

– High resolution enables speciation between similar moleculesButane, Propane, Ethane, Methane, fuel sources, etc.

– Permanent calibration – Analysis performed at various sites

H2 production siteH2 storage site: gas or liquid cylindersAt - Line analysis at fueling station

Infrared (IR) Spectroscopy

Based on IR light absorption – Energy (IR radiation) heats molecule - vibrations and rotations– The pattern and intensity of the spectrum provides all the information

about gas (type and concentration)

Background and Sample

BACKGROUND (Io)N2 Purge 1cm-1

SAMPLE (I)1000 ppm NH3 1cm-1

Absorbance = - Log (I/Io)

Absorbance is Proportional to Concentration

FFT of Sample1000 ppm NH3 1.0 cm-1

Absorbance = - Log (I/Io)Absorbance = ε • C • path

What Can FTIR Do?

Analyze all components that:– Are IR active– Have Dipole Moments

Examples– Ammonia, CO, CO2, H2O,

Hydrocarbons, etc

Raw Reformed Hydrogen– Percent level analysis

Purified Hydrogen– PPB level analysis

0-100Low ppmSulfur Dioxide (SO2), ppm

Low ppmLow ppmNitric Dioxide (NO2), ppm

0-100Low ppmNitric Oxide (NO), ppm

0-100-10Non-methane Hydrocarbons, %

0-100-10Methane (CH4), %

0-250-25Water (H2O), %

0-250-25Carbon Dioxide (CO2), %

0-250-25Carbon Monoxide (CO), %

Low ppm0-300Hydrogen Sulfide (H2S), ppm

0-800-10Nitrogen (N2), %

0-50-1Oxygen (O2), %

0-1040-80Hydrogen (H2), %

ExhaustProductComponent

FTIR Components Used For TestGas Cell – Stainless steel – path length 5.11 meters– Metal sealed cell: <10-9 Torr / min He leak rate– BaF2 gas cell windows

Infrared cutoff near 850 cm-1

– Gold coated mirrors

Two Detectors Validated– 9.2u TE cooled detector

Infrared cutoff near 1100 cm-1

– 16u Stirling cooled detectorInfrared cutoff @ 850 cm-1 due to BaF2 windows

9u Cutoff

Water

Methane

Ethane

Formaldehyde

Formic Acid

CO2

COAmmonia

16u Cutoff

Method Validation

EPA Method 40 CFR 136 Appendix B– Build calibrations on FTIR– Estimate a minimum detection limit– Determine how low a concentration can be

detected with this method

FTIR Validation Method for H2

Gases validated on FTIR– CO, CO2, CH4, C2H6, NH3, H2O, Formaldehyde

and Formic Acid– All in Balance of H2

Gas standards creation– NIST traceable gas cylinders for gases

100 ppm of CO, CO2, CH4, C2H6 in H2

– NIST traceable permeation tubes for liquidsNH3, H2O, Formaldehyde and Formic Acid

– Blended with H2

Purified H2 (<1ppb H2O, CO CO2)

Contaminant SAE J2719 Detection

Limits (ppmv) 16u Stirling* 9.2u TE 16u LN2

Ammonia (NH3) 0.10 0.36 0.81 0.02 Carbon Monoxide (CO) 0.20 0.01 0.05 0.01 Carbon Dioxide (CO2) 2.00 0.01 0.01 0.01 Formaldehyde (HCHO) 0.01 0.02 0.02 0.02 Formic Acid (HCOOH) 0.20 0.03 0.02 0.02 Total Hydrocarbons (Reported as C1)

2.00 0.71

Methane 0.10 0.02 0.02 0.03 Ethane 0.10 0.02 0.05 0.05 Ethylene 0.10 0.03 Water (H2O) 5.00 0.40 0.74 0.12

Method Detection Limits

* Signal to noise ratio (SNR) was 1/3 that of 16u LN2 for this test* However improved SNR to same level as 16u LN2

Acknowledgments

Fuel cell work– Air Liquide Research and Technology Center

Robert Benesch, Tracey Jacksier, Sumaeya Salman

Method validation / calibration work– Elutions Design Bureau, Inc – Houston, TX

Scott Thompson– MKS Instruments – On Line Product Group

Barbara Marshik– Monetary support for this work

MKS InstrumentsShell Global Solutions Inc. - Westhollow Technology Center