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Dr. H. de Vries, Ir. O. Florisson and Ir. G.C. Tiekstra N.V. Nederlandse Gasunie

Safe operation of Natural Gas Appliances Fueled with Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project). Dr. H. de Vries, Ir. O. Florisson and Ir. G.C. Tiekstra N.V. Nederlandse Gasunie 2nd ICHS, San Sebastian, 13-09-2007. Naturalhy project.

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Dr. H. de Vries, Ir. O. Florisson and Ir. G.C. Tiekstra N.V. Nederlandse Gasunie

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  1. Safe operation of Natural Gas Appliances Fueled with Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project) Dr. H. de Vries, Ir. O. Florisson and Ir. G.C. Tiekstra N.V. Nederlandse Gasunie 2nd ICHS, San Sebastian, 13-09-2007

  2. Naturalhy project  Preparing for the Hydrogen Economy by using the existing natural gas system as a catalyst • Physical and Chemical properties of Hydrogen differ from Natural Gas, with impact on: • Socio-economic and LCA aspects • Safety • Durability of pipeline material • Integrity of pipeline system • End-use and separation

  3. Integrity & Durability* Safety & Risk* End-use 0 100 Preliminary Conclusion * = Based upon current testresults, more tests are planned First indications: Max allowable Hydrogen for End-use might be the most limiting

  4. Thank you for your attention Gjalt Tiekstra Coordinator Naturalhy project www.naturalhy.net

  5. Safe operation: NG appliances: NG/H2 • Focus on domestic appliances • [H2]max limit by Wobbe index conditions in NG distribution • [H2]max limit by combustion safety aspects (light back) Gasunie, 2nd ICHS 13-09-’07

  6. Common safety practice in NG appln • Gas Appliances Directive (GAD): Council Directive 29-06-1990 • About 70 harmonised standards on appliances and fittings • EN437: Test gases – Test pressures – Appliance categories: • Gas classification: Wobbe index: W = Hs / , (T1,T2) (MJ/m3) • Type testing: short term tests of new appliances Gasunie, 2nd ICHS 13-09-’07

  7. EN 437 group test range incompl. combustion / sooting limit gas W (overheating limit gas) reference gas light back limit gas flame lift limit gas distribution range: “normal use” Distributed gases and Test gases Gasunie, 2nd ICHS 13-09-’07

  8. WmaxEN437 group W Wmaxdistr WNG WNG/H2 [H2]max Wmindistr WminEN437 group Distribution condition: WNG/H2 ≥ Wmindistr > WminEN437 group [H2]max limit by distribution condition Gasunie, 2nd ICHS 13-09-’07

  9. SL cold mixture: Fprim : fuel-rich or fuel-lean primary flame front Burner in appliance vu flow rate F + A CxHy ,N2 ,H2 , … AIR N2 ,O2 , … FUEL GAS flow rate F flow rate A constant Premixed appliance operation Gasunie, 2nd ICHS 13-09-’07

  10. F A Premixed appliance operation (2) • Fprim = (F/A) / (F/A)stoich • Behaviour upon changing fuel gas composition • Constant fuel gas pressure, constant air flow rate • Stable flame front: appliance safety (SL = vu) Gasunie, 2nd ICHS 13-09-’07

  11. Risk of light back with H2 • Light back: when everywhere in the flame front SL > vu holds, the flame will propagate upstream into the burner • Well-known: SL (H2) > SL (hydrocarbons) • CH4/H2 mixtures are sufficiently representative for NG/H2 mixtures for the present purposes Gasunie, 2nd ICHS 13-09-’07

  12. fuel-lean fuel-rich H2 F-shift: F(NG/H2) < F(NG) CH4/H2 = 20/80 CH4/H2 = 70/30 CH4 SL , F and H2 admixture Gasunie, 2nd ICHS 13-09-’07

  13. CH4/H2 = 70/30 CH4/H2 = 90/10 CH4 DSL for appliances (fuel-lean/fuel-rich) Gasunie, 2nd ICHS 13-09-’07

  14. [H2]max limit by light back (fuel-rich) • Practically useful [H2]maxvalues needed: experimentally comparing the light back behaviour of NG/H2 mixtures with that of a light back reference gas • “incipient light back” experiments on simple Bunsen tubes for most critical situations: Fprim ~ 1.2 – 1.3 • Gasunie (Prof. Dr. H.B. Levinsky et al) ; EET Program of the Dutch Ministry of Economic Affairs Gasunie, 2nd ICHS 13-09-’07

  15. Bunsen tube experiments Gasunie, 2nd ICHS 13-09-’07

  16. [H2]max from incipient light back expts. • These Bunsen tube experiments set – for the first time – light back limited [H2]max values for appliances that are light back critical upon H2 addition (cooking burners) in general , as acceptable from common safety practice • At the same time, one should realize that existing NG appliances were not designed for long-term use with H2 containing mixtures (corrosion, leakage)  large amount of testing effort needed * * * Gasunie, 2nd ICHS 13-09-’07

  17. Viewpoint: W-band • EN437 testgas Wobbe bands and Wobbe distribution bands apply on a national or regional scale • The appliances of different type all are connected to one and the same national or regional NG distribution grid • It is practical to consider detailed results from the viewpoint of a W-band • Safety aspect limited [H2]max per appliance type • WNG/H2 = Wmindistr. determined [H2]max limit • The lowest [H2]max value counts Gasunie, 2nd ICHS 13-09-’07

  18. WmaxH WminH [H2]max H-band situation Gasunie, 2nd ICHS 13-09-’07

  19. NG/H2 : where are we now ? • It is not yet justified to present statements on what level of hydrogen concentration could be safely allowed in which specific natural gas distribution region • More clarity obtained on some essential H2 admixing issues: • Combustion safety aspects of existing domestic appliances • The connection with the Wobbe distribution condition • More work needed on domestic appliances: • Fundamental calculations (straightforward) • Carefully designed experiments (straightforward) • Long-term corrosion tests Gasunie, 2nd ICHS 13-09-’07

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