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#REDIRECT [[Hydrogen purification]] |
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'''Hydrogen purity''' or hydrogen quality describes the presence of impurities in [[hydrogen]] when used as a [[fuel gas]]. Impurities in hydrogen can interfere with the proper functioning of equipment that stores, distributes, or uses [[hydrogen fuel]]. |
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== Hydrogen Purity Requirements == |
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The impact of impurities varies with the specific equipment used and on the physio-chemical nature of the impurity. For example, hydrogen boilers that combust hydrogen will generally tolerate higher concentrations of impurities than a vehicle using a [[Proton-exchange membrane fuel cell|polymer electrolyte membrane fuel cell (PEMFC)]]<ref name=":222">{{Cite web|title=WP2 Report Hydrogen Purity|url=https://www.hy4heat.info/reports|url-status=live|access-date=2021-10-18|website=Hy4Heat|language=en-US}}</ref> and inert impurities such as nitrogen are usually less harmful than reactive species such as hydrogen sulphide.<ref name=":0">{{Cite web|last=|title=ISO 14687:2019|url=https://www.iso.org/cms/render/live/en/sites/isoorg/contents/data/standard/06/95/69539.html|url-status=live|access-date=2021-10-18|website=|language=en}}</ref> |
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As the specific impurity matters it is not sufficient to rely on normal metrics of gas purity, often reported using [[Nines (notation)|nines]] (e.g. >99.9990% or 5.0N),<ref>{{Cite web|title=Purity, Grades and Concentration|url=https://www.boconline.co.uk/en/contact-and-support/technical-advice/speciality-products-advice/purity-grades-concentration/purity-grades.html|access-date=2021-10-27|website=BOConline UK|language=en}}</ref> as this does not provide adequate information about which impurities may be present at trace levels. Instead, standards have been developed that provide more detailed requirements on fuel purity for specific applications. The international standard ISO 14687-2-2019 <ref name=":0" /> specifies maximum permissible concentrations for many key impurities depending on use. This standard is being adopted into legislation in many jurisdictions. For example, in Europe the Directive 2014/94/EU<ref>{{Cite web|title=Directive 2014/94/EU on the deployment of alternative fuels structure|url=https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32014L0094&from=EN|access-date=15 August 2018}}</ref> on the deployment of alternative fuels infrastructure states that the hydrogen purity dispensed by hydrogen refuelling points shall comply with the technical specifications included in ISO 14687-2. |
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=== Fuel Cell Electric Vehicles === |
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Fuel cell electric vehicles commonly use polymer electrolyte membrane fuel cells (PEMFC) which are susceptible to a range of impurities. Impurities impact PEMFC using a range of mechanisms, these may include [[Catalyst poisoning|poisoning]] the anode hydrogen oxidation reaction catalysts, reducing the ionic conductivity of the ionomer and membrane, altering wetting behaviour of components or blocking porosity in diffusion media. The impact of some impurities like [[carbon monoxide]], [[formic acid]], or [[formaldehyde]] is reversible with PEMFC performance recovering once the supply of impurity is removed. Other impurities, for example sulphurous compounds, may cause irreversible degradation.<ref>{{Cite journal|last=X. Cheng, Z. Shi, N. Glass, L. Zhang, J. Zhang, D. Song, Z.-S. Liu, H. Wang and J. Shen|year=2007|title=A review of PEM hydrogen fuel cell contamination:Impacts, mechanisms, and mitigation|journal=Journal of Power Sources|volume=165|issue=2|pages=739–756|doi=10.1016/j.jpowsour.2006.12.012|bibcode=2007JPS...165..739C}}</ref> The permissible limits of hydrogen impurities are shown below. |
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{| class="wikitable" |
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|+Fuel Quality Specification For Gasseous Hydrogen Supplied to PEMFC Road Vehicles <ref name=":02">{{Cite web|last=|title=ISO 14687:2019|url=https://www.iso.org/cms/render/live/en/sites/isoorg/contents/data/standard/06/95/69539.html|url-status=live|access-date=2021-10-18|website=|language=en}}</ref> |
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! |
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!Maximum Permissible Concentration / |
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|Total non-hydrogen gasses |
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|300 |
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|Water |
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|5 |
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|Total Hydrocarbons Except Methane [Carbon atom basis] |
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|2 |
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|Methane |
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|100 |
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|Oxygen |
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|5 |
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|Helium |
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|300 |
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|Nitrogen |
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|300 |
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|Argon |
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|300 |
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|Carbon Dioxide |
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|2 |
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|Carbon Monoxide |
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|0.2 |
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|Total Sulphur Compounds [Sulphur atom basis] |
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|0.004 |
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|Formaldehyde |
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|0.2 |
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|Formic Acid |
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|0.2 |
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|Ammonia |
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|0.1 |
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|Halogenated Compounds [Halogen ion basis] |
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|0.05 |
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|Maximium Particulate Concentration |
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|1 mg kg<sup>−1</sup> |
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|} |
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Efforts to assess the compliance of hydrogen supplied by hydrogen refuelling stations against the ISO-14687 standard have been performed.<ref name=":1">{{Cite journal|last1=Aarhaug|first1=Thor Anders|last2=Kjos|first2=Ole|last3=Bacquart|first3=Thomas|last4=Valter|first4=Vladimir|last5=Optenhostert|first5=Thomas|date=2021-08-18|title=Assessment of hydrogen quality dispensed for hydrogen refuelling stations in Europe|url=https://www.sciencedirect.com/science/article/pii/S0360319920344098|journal=International Journal of Hydrogen Energy|series=HYDROGEN ENERGY SYSTEMS|language=en|volume=46|issue=57|pages=29501–29511|doi=10.1016/j.ijhydene.2020.11.163|s2cid=230535934|issn=0360-3199}}</ref><ref>{{Cite journal|last1=Aarhaug|first1=Thor A.|last2=Kjos|first2=Ole S.|last3=Ferber|first3=Alain|last4=Hsu|first4=Jong Pyong|last5=Bacquart|first5=Thomas|date=2020|title=Mapping of Hydrogen Fuel Quality in Europe|journal=Frontiers in Energy Research|volume=8|pages=307|doi=10.3389/fenrg.2020.585334|issn=2296-598X|doi-access=free}}</ref><ref>{{Cite web|title=HYDRAITE public report D3.1 {{!}} HYDRAITE|url=https://hydraite.eu/public-reports/|url-status=live|access-date=2021-10-18|language=en-US}}</ref> While the hydrogen was generally found to be 'good'<ref name=":1" /> violations of the standard have been reported, most frequently for nitrogen, water and oxygen. |
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=== Combustion Engines and Appliances === |
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Combustion applications are generally more tolerant of hydrogen impurities than PEFMC, as such the ISO-14687 standard for permissible impurities is less strict.<ref name=":03">{{Cite web|last=|title=ISO 14687:2019|url=https://www.iso.org/cms/render/live/en/sites/isoorg/contents/data/standard/06/95/69539.html|url-status=live|access-date=2021-10-18|website=|language=en}}</ref> This standard has its self been criticised with revisions proposed to make it more lenient and therefor suitable for hydrogen distributed through a repurposed gas network.<ref name=":222"/> |
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{| class="wikitable" |
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|+Fuel Quality Specification For Gasseous Hydrogen Supplied to Combustion Engines and Appliances <ref name=":04">{{Cite web|last=|title=ISO 14687:2019|url=https://www.iso.org/cms/render/live/en/sites/isoorg/contents/data/standard/06/95/69539.html|url-status=live|access-date=2021-10-18|website=|language=en}}</ref> |
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!Impurity |
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!Maximium Permissible Concentration / |
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|- |
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|Total non-hydrogen gasses |
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|20 000 |
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|Water |
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|Non-condensing |
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|Total Hydrocarbons [Carbon atom basis] |
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|100 |
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|Carbon Monoxide |
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|1 |
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|Sulphur [Sulphur atom basis] |
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|2 |
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|Combined water, oxygen, nitrogen, argon |
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|19 000 |
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|Permanent Particulates |
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|Shall not contain an amount sufficient to cause damage. |
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|} |
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== Sources of Hydrogen Impurities == |
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The presence of impurities in hydrogen depends on the feedstock and the production process. Hydrogen produced by [[Electrolysis of water|electrolysis]] of water may routinely include trace oxygen and water, which must be usually be removed prior to use. Hydrogen produced by [[Steam reforming|reforming]] of hydrocarbons is produced as a mixture with a stoichiometric mixture with carbon dioxide and carbon monoxide which must be separated, additionally trace impurities from the feedstock such as sulphur compounds may be present in the final hydrogen supply. Impurities may also be introduced during storage, distribution, dispensing or as a result of equipment malfunction. Examples of this include distribution of hydrogen through repurposed gas networks which may be contaminated with a range of impurities or malfunctioning of equipment at refuelling stations.<ref name=":222" /> Some impurities may be added deliberately, for example odorants to aid detection of gas leaks.<ref>{{Cite web|title=Hydrogen Odorant and Leak Detection Project Closure Report|url=https://sgn.co.uk/sites/default/files/media-entities/documents/2020-09/Hydrogen_Odorant_and_Leak_Detection_Project_Closure_Report_SGN.pdf|url-status=live}}</ref> |
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== Methods for Hydrogen Purity Analysis == |
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As the permissible concentrations for many impurities are very low this sets stringent demands on the sensitivity of the analytical methods. Moreover, the high reactivity of some impurities requires use of a properly passivated sampling and analytical systems.<ref>{{Cite journal|last1=Bacquart|first1=Thomas|last2=Moore|first2=Niamh|last3=Hart|first3=Nick|last4=Morris|first4=Abigail|last5=Aarhaug|first5=Thor A.|last6=Kjos|first6=Ole|last7=Aupretre|first7=Fabien|last8=Colas|first8=Thibault|last9=Haloua|first9=Frederique|last10=Gozlan|first10=Bruno|last11=Murugan|first11=Arul|date=2020-02-14|title=Hydrogen quality sampling at the hydrogen refuelling station – lessons learnt on sampling at the production and at the nozzle|url=https://www.sciencedirect.com/science/article/pii/S0360319919340510|journal=International Journal of Hydrogen Energy|series=22nd World Hydrogen Energy Conference|language=en|volume=45|issue=8|pages=5565–5576|doi=10.1016/j.ijhydene.2019.10.178|s2cid=213820032|issn=0360-3199}}</ref> Sampling of hydrogen of is challenging and care must be taken to ensure that impurities are not introduced to the sample and that impurities do not absorb on or react within the sampling equipment, there are currently different methods for sampling but rely on filling a gas cylinder from the refuelling nozzle of a refuelling station.<ref>{{Cite journal|last1=Arrhenius|first1=Karine|last2=Aarhaug|first2=Thor|last3=Bacquart|first3=Thomas|last4=Morris|first4=Abigail|last5=Bartlett|first5=Sam|last6=Wagner|first6=Lisa|last7=Blondeel|first7=Claire|last8=Gozlan|first8=Bruno|last9=Lescornez|first9=Yann|last10=Chramosta|first10=Nathalie|last11=Spitta|first11=Christian|date=2021-10-11|title=Strategies for the sampling of hydrogen at refuelling stations for purity assessment|url=https://www.sciencedirect.com/science/article/pii/S0360319921031694|journal=International Journal of Hydrogen Energy|language=en|volume=46|issue=70|pages=34839–34853|doi=10.1016/j.ijhydene.2021.08.043|s2cid=239636011|issn=0360-3199}}</ref> Efforts are underway to standardise and compare sampling strategies.<ref>{{Citation|title=Practice for Sampling of High Pressure Hydrogen and Related Fuel Cell Feed Gases|url=http://dx.doi.org/10.1520/d7606-17|publisher=ASTM International|doi=10.1520/d7606-17|access-date=2021-11-01}}</ref><ref>{{Citation|title=DIN ISO/TS 22002-3:2017-09|url=https://www.iso.org/obp/ui/#iso:std:iso:19880:-1:ed-1:v1:en|publisher=|access-date=2021-11-01}}</ref> A combination of different instruments is needed to assess hydrogen samples for all of the components listed in ISO 14687-2.<ref>{{Cite journal|last1=Murugan|first1=Arul|last2=Brown|first2=Andrew S.|date=2015-03-22|title=Review of purity analysis methods for performing quality assurance of fuel cell hydrogen|url=https://www.sciencedirect.com/science/article/pii/S0360319915000804|journal=International Journal of Hydrogen Energy|language=en|volume=40|issue=11|pages=4219–4233|doi=10.1016/j.ijhydene.2015.01.041|issn=0360-3199}}</ref> Techniques suitable for individual impurities are indicated in the table below. |
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{| class="wikitable" |
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|+Example Analytical Methods for Asessing The Concentration of Impurities in Hydrogen<ref>{{Cite web|title=Hydrogen purity|url=https://www.npl.co.uk/products-services/gas/hydrogen-purity|access-date=2021-10-18|website=NPLWebsite|language=en}}</ref><ref>{{Cite journal|last1=Bacquart|first1=Thomas|last2=Arrhenius|first2=Karine|last3=Persijn|first3=Stefan|last4=Rojo|first4=Andrés|last5=Auprêtre|first5=Fabien|last6=Gozlan|first6=Bruno|last7=Moore|first7=Niamh|last8=Morris|first8=Abigail|last9=Fischer|first9=Andreas|last10=Murugan|first10=Arul|last11=Bartlett|first11=Sam|date=2019-12-31|title=Hydrogen fuel quality from two main production processes: Steam methane reforming and proton exchange membrane water electrolysis|url=https://www.sciencedirect.com/science/article/pii/S0378775319311632|journal=Journal of Power Sources|language=en|volume=444|pages=227170|doi=10.1016/j.jpowsour.2019.227170|bibcode=2019JPS...44427170B|s2cid=208754564|issn=0378-7753}}</ref> |
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!Impurity |
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!Possible Analytical Methods |
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!Detection Limits |
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|Total non-hydrogen gasses |
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| |
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| |
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|Water |
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|Quartz crystal microbalance |
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or CRDS |
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|1.3 or 0.030 |
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|Total Hydrocarbons Except Methane [Carbon atom basis] |
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|GC-Methaniser-FID |
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|0.1 |
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|- |
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|Methane |
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|GC-Methaniser-FID |
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|0.1 |
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|Oxygen |
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|GC-PDHID |
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|0.3 |
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|Helium |
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|GC-TCD |
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|10 |
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|Nitrogen |
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|GC-PDHID |
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|1 |
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|Argon |
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|GC-PDHID |
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|0.3 |
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|Carbon Dioxide |
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|GC-Methaniser-FID |
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|0.02 |
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|Carbon Monoxide |
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|GC-Methaniser-FID |
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|0.02 |
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|Total Sulphur Compounds [Sulphur atom basis] |
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|GC-SCD |
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|0.001 |
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|Formaldehyde |
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|GC-Methaniser-FID |
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|0.1 |
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|Formic Acid |
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|FTIR |
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|0.2 |
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|Ammonia |
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|GC-MS or UV-visible spectroscopy or FTIR |
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|1 or 0.03 or 0.1 |
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|Halogenated Compounds (Halogen Ion Equivalent) |
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|TD-GC-MS |
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|0.016 |
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|} |
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In addition to rigorous laboratory analysis analytical methods that can be operated in the field continuously assessing hydrogen for impurities are being developed. These include techniques such as electrochemical sensors <ref>{{Cite journal|last=Mukundan|first=Rangachary|title=Development of an Electrochemical Hydrogen Contaminant Detector|url=https://iopscience.iop.org/article/10.1149/1945-7111/abc43a/meta|journal=Journal of the Electrochemical Society|year=2020|language=en|volume=167|issue=14|pages=147507|doi=10.1149/1945-7111/abc43a|bibcode=2020JElS..167n7507M|s2cid=226341724}}</ref><ref>{{Cite journal|last1=Noda|first1=Z.|last2=Hirata|first2=K.|last3=Hayashi|first3=A.|last4=Takahashi|first4=T.|last5=Nakazato|first5=N.|last6=Saigusa|first6=K.|last7=Seo|first7=A.|last8=Suzuki|first8=K.|last9=Ariura|first9=S.|last10=Shinkai|first10=H.|last11=Sasaki|first11=K.|date=2017-02-02|title=Hydrogen pump-type impurity sensors for hydrogen fuels|url=https://www.sciencedirect.com/science/article/pii/S0360319916336138|journal=International Journal of Hydrogen Energy|language=en|volume=42|issue=5|pages=3281–3293|doi=10.1016/j.ijhydene.2016.12.066|issn=0360-3199}}</ref> and mass spectrometry.<ref>{{Cite web|title=HydrogenSense|url=https://www.vandf.com/en/products/analyzers/hydrogensense/,%20https://www.vandf.com/en/products/analyzers/hydrogensense/|url-status=live|access-date=2021-10-27|website=www.vandf.com|language=en}}</ref> |
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== Methods for Purifying Hydrogen == |
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[[Hydrogen purifier|See also: Hydrogen purifier]] |
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Purification of hydrogen is an important aspect of hydrogen distribution and there are a range of technologies available depending on the impurities present and process conditions.<ref name=":222"/> |
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==See also== |
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* [[Hydrogen station]] |
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* [[Hydrogen fuel]] |
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* [[Hydrogen purifier]] |
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* [[Proton-exchange membrane fuel cell]] |
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* [https://www.sintef.no/projectweb/metrohyve-2/ MetroHyVe2 Project] |
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* [https://hydraite.eu/ Hydraite Project] |
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* [https://www.npl.co.uk/products-services/gas/hydrogen-purity National Physical Laboratory Hydrogen Purity] |
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==References== |
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{{reflist|refs=}} |
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{{DEFAULTSORT:Hydrogen Purity}} |
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[[Category:Hydrogen]] |
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[[Category:Hydrogen technologies]] |
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Latest revision as of 22:36, 11 April 2024
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