Safe operation of Natural Gas Appliances Fueled with Hydrogen/Natural Gas Mixtures (Progress Obtaine...
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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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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 Hydrogen/Natural Gas Mixtures (Progress Obtained in the 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


Preliminary conclusion

Integrity & Durability* Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)

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


Thank you for your attention

Thank you for your attention Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)

Gjalt Tiekstra

Coordinator Naturalhy project

www.naturalhy.net


Safe operation ng appliances ng h 2
Safe operation: NG appliances: NG/H Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)2

  • 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


Common safety practice in ng appl n
Common safety practice in NG appl Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)n

  • 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


Distributed gases and test gases

EN 437 group Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)

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


H 2 max limit by distribution condition

W Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)maxEN437 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


Premixed appliance operation

S Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)L

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


Premixed appliance operation 2

F Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)

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


Risk of light back with h 2
Risk of light back with H Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)2

  • 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


S l f and h 2 admixture

fuel-lean Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)

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


D s l for appliances fuel lean fuel rich

CH4/H2 = 70/30 Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)

CH4/H2 = 90/10

CH4

DSL for appliances (fuel-lean/fuel-rich)

Gasunie, 2nd ICHS 13-09-’07


H 2 max limit by light back fuel rich
[H Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)2]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


Bunsen tube experiments
Bunsen tube experiments Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)

Gasunie, 2nd ICHS 13-09-’07


H 2 max from incipient light back expts
[H Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)2]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


Viewpoint w band
Viewpoint: W-band Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)

  • 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


H band situation

W Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)maxH

WminH

[H2]max

H-band situation

Gasunie, 2nd ICHS 13-09-’07


Ng h 2 where are we now
NG/H Hydrogen/Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)2 : 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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