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> An acre full of pressurized hydrogen sounds like a Port of Beirut moment waiting to happen. You still need oxygen to react no? If it’s pure hydrogen …

dredmorbius 5y ago
Oxygen is available in bulk at eminently reasonable rates.
- simonh 5y ago
  As long as 20% concentration is sufficient, I've found no difficulty securing local supplies.
  - masklinn 5y ago
    I wonder what the flammability limits of hydrogen in low-ox environments is. It's 4 and 75 in air (so hydrogen will readily ignite between 4% an 75% hydrogen in air at 1atm), and it's 4 and 94 in pure oxygen. And the good news is that there is a limiting oxygen concentration, but the bad news is it's 5% (so over 5% oxygen by volume at STP it becomes possible for hydrogen to ignite), but I could not find flammability limits at sub20.
- worrycue 5y ago
  The original post had a reference to the Port of Beirut which had a ammonium nitrate explosion. That type of explosion don't require oxygen to my knowledge - denotation is caused by shockwave and in fact ammonium nitrate is itself a strong oxidizer, from what I read; "While ammonium nitrate is stable at ambient temperature and pressure under many conditions, it may detonate from a strong initiation charge. It should not be stored near high explosives or blasting agents." "Pure ammonium nitrate does not burn, but as a strong oxidizer, it supports and accelerates the combustion of organic (and some inorganic) material." - https://en.wikipedia.org/wiki/Ammonium_nitrate#Safety,_handling,_and_storage https://en.wikipedia.org/wiki/Ammonium_nitrate#Safety,_handl... Hydrogen would behave more like gasoline. It's only when there is a fuel-oxygen mixture do they start explosively burning - i.e. it should not go off all at once unless you pump the tank with oxygen and mix them/give the oxygen time to diffuse through the tank.
  - dredmorbius 5y ago
    Petrol doesn't tend to molecularly diffuse through solid containment, or embrittle metals. It's also remarkably difficult to ignite --- you can extinguish a match in it. A cigarette is demonstrated here: https://www.youtube.com/watch?v=DsZOE1nvlhI https://www.youtube.com/watch?v=DsZOE1nvlhI (Note that ignition will usually but not always fail. I don't advise making a habit of this.) Hydrogen is far more readily ignited: https://www.youtube.com/watch?v=RudCaJB_Xx4 https://www.youtube.com/watch?v=RudCaJB_Xx4 (It can also produce surprises after burning for a while.) Whilst it's true that a container or pipeline filled with gaseous or liquid hydrogen would be unlikely to explode iself directly, chances are reasonably high of leaks developing and from those, explosive mixes of hydrogen and air either within ground cavities or nearby structures. Embritlement might result in catastrophic failure of tanks or pipes (petrol is also rarely stored at high pressures or cryogenic temperatures). Resulting thermal and pressure shocks could further extend damage and increase rates of release and combustion. Resulting conflagrations might more closely resemble natural gas fires than ammonium nitrate / ANFO explosions, but those can be dangerous enough of themselves. Keep in mind that ANFO also tends not to flow as a liquid or gas, and whilst it reacts very rapidly, has only about ten percent of the energy by unit mass of hydrocarbon or pure hydrogen fuels. Once ignited, and if supplied with atmospheric oxygen, hydrogen will burn quite vigorously, and even explosively (flame front expanding faster than the speed of sound) given a proper stochiometric balance. All told, if anything goes wrong with a large hydrogen storage or distribution facility, it will quite probably be quite spectacular.
    - worrycue 5y ago
      Hydrogen storage seem like a pretty mature field, https://en.m.wikipedia.org/wiki/Hydrogen_tank https://en.m.wikipedia.org/wiki/Hydrogen_tank We have dealt with gasoline, which can leak and is just as dangerous, IMO just fine for decades - and gasoline vapor has a tendency to pool near the ground rather than float off and disperse high into the sky like hydrogen. Franky, it seems just about every energy storage system has pretty frightening failure modes - I take it you have seen the video of a Tesla fiercely burning up in a carpark in China.
      - 5y ago

dredmorbius 5y ago

Oxygen is available in bulk at eminently reasonable rates.

simonh 5y ago
As long as 20% concentration is sufficient, I've found no difficulty securing local supplies.
- masklinn 5y ago
  I wonder what the flammability limits of hydrogen in low-ox environments is. It's 4 and 75 in air (so hydrogen will readily ignite between 4% an 75% hydrogen in air at 1atm), and it's 4 and 94 in pure oxygen. And the good news is that there is a limiting oxygen concentration, but the bad news is it's 5% (so over 5% oxygen by volume at STP it becomes possible for hydrogen to ignite), but I could not find flammability limits at sub20.
worrycue 5y ago
The original post had a reference to the Port of Beirut which had a ammonium nitrate explosion. That type of explosion don't require oxygen to my knowledge - denotation is caused by shockwave and in fact ammonium nitrate is itself a strong oxidizer, from what I read; "While ammonium nitrate is stable at ambient temperature and pressure under many conditions, it may detonate from a strong initiation charge. It should not be stored near high explosives or blasting agents." "Pure ammonium nitrate does not burn, but as a strong oxidizer, it supports and accelerates the combustion of organic (and some inorganic) material." - https://en.wikipedia.org/wiki/Ammonium_nitrate#Safety,_handling,_and_storage https://en.wikipedia.org/wiki/Ammonium_nitrate#Safety,_handl... Hydrogen would behave more like gasoline. It's only when there is a fuel-oxygen mixture do they start explosively burning - i.e. it should not go off all at once unless you pump the tank with oxygen and mix them/give the oxygen time to diffuse through the tank.
- dredmorbius 5y ago
  Petrol doesn't tend to molecularly diffuse through solid containment, or embrittle metals. It's also remarkably difficult to ignite --- you can extinguish a match in it. A cigarette is demonstrated here: https://www.youtube.com/watch?v=DsZOE1nvlhI https://www.youtube.com/watch?v=DsZOE1nvlhI (Note that ignition will usually but not always fail. I don't advise making a habit of this.) Hydrogen is far more readily ignited: https://www.youtube.com/watch?v=RudCaJB_Xx4 https://www.youtube.com/watch?v=RudCaJB_Xx4 (It can also produce surprises after burning for a while.) Whilst it's true that a container or pipeline filled with gaseous or liquid hydrogen would be unlikely to explode iself directly, chances are reasonably high of leaks developing and from those, explosive mixes of hydrogen and air either within ground cavities or nearby structures. Embritlement might result in catastrophic failure of tanks or pipes (petrol is also rarely stored at high pressures or cryogenic temperatures). Resulting thermal and pressure shocks could further extend damage and increase rates of release and combustion. Resulting conflagrations might more closely resemble natural gas fires than ammonium nitrate / ANFO explosions, but those can be dangerous enough of themselves. Keep in mind that ANFO also tends not to flow as a liquid or gas, and whilst it reacts very rapidly, has only about ten percent of the energy by unit mass of hydrocarbon or pure hydrogen fuels. Once ignited, and if supplied with atmospheric oxygen, hydrogen will burn quite vigorously, and even explosively (flame front expanding faster than the speed of sound) given a proper stochiometric balance. All told, if anything goes wrong with a large hydrogen storage or distribution facility, it will quite probably be quite spectacular.
  - worrycue 5y ago
    Hydrogen storage seem like a pretty mature field, https://en.m.wikipedia.org/wiki/Hydrogen_tank https://en.m.wikipedia.org/wiki/Hydrogen_tank We have dealt with gasoline, which can leak and is just as dangerous, IMO just fine for decades - and gasoline vapor has a tendency to pool near the ground rather than float off and disperse high into the sky like hydrogen. Franky, it seems just about every energy storage system has pretty frightening failure modes - I take it you have seen the video of a Tesla fiercely burning up in a carpark in China.
    - 5y ago