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Thread: Hydrogen Flammability and explosive reaction

  1. #1 Hydrogen Flammability and explosive reaction 
    Forum Freshman
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    HI,
    I have a quick question that has me a little confused.
    I was reading that hydrogen does not react explosively above 1400F (760C), please see link:
    https://vacaero.com/information-reso...ce-unsafe.html

    I wasn't aware that there was such a thing as a maximum explosive temperature, surely if the concentrations are correct it will explode regardless of temperature as long as there is an ignition source???

    I am aware that the link above is in a vacuum furnace so there would be very little air to mix with the hydrogen, however I am just curious about the temperature aspect of this.

    Many thanks
    James


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  3. #2  
    exchemist
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    Quote Originally Posted by james2409 View Post
    HI,
    I have a quick question that has me a little confused.
    I was reading that hydrogen does not react explosively above 1400F (760C), please see link:
    https://vacaero.com/information-reso...ce-unsafe.html

    I wasn't aware that there was such a thing as a maximum explosive temperature, surely if the concentrations are correct it will explode regardless of temperature as long as there is an ignition source???

    I am aware that the link above is in a vacuum furnace so there would be very little air to mix with the hydrogen, however I am just curious about the temperature aspect of this.

    Many thanks
    James
    I share your confusion. Generally the upper and lower explosive limits get farther apart as temperature rises, meaning that a wider range of compositions can explode, increasing the risk.

    Also, slightly tangentially, I found this paper, which is actually very interesting on the mechanism of the chain reaction of hydrogen combustion.: http://dtic.mil/dtic/tr/fulltext/u2/a264896.pdf

    This has a diagram on p8 that seems to show that for stochiometric mixtures there is a complex dependence on pressure and temperature, but in general as temperature rises the explosive areas get larger and above 580C any pressure will be explosive. There is some discussion of the chain steps that are implicated in determining the shape of the curve, which I found interesting. But it is not directly relevant as we are not dealing with stoichiometric mixtures.

    I don't think I can help further. Perhaps someone else can explain it.


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