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Help? trying to solve an energy problem?

  1. Jun 10, 2015 #1
    I am trying to figure out what kind of force would be given off if a 4000 gallon tank of ethanol were to ignite. My husband is a distiller, and to help raise awareness of safety issues, he's trying to explain to his coworkers the kind of explosive force that could occur if it were to ignite by faulty wiring, lightning strike, or some dummy smoking around it. All I can understand is that 1kg of ethanol contains 27,000 joules, which can lift a pound 9 inches. Beyond that, I have no idea what I'm doing here. If I had 4000 gallons of ethanol ignite in a tank, about how many square feet would it destroy? This would be a safety concern for even neighboring buildings, not just employees, correct?
  2. jcsd
  3. Jun 10, 2015 #2
    I mean ethyl alcohol. I think he's looking for the velocity in feet per second of the explosion?
  4. Jun 10, 2015 #3
    And like, how fast would that go off? Like so many square inches in how many seconds?
  5. Jun 10, 2015 #4


    Staff: Mentor

    It can't burn without oxygen. A tank full of ethanol is pretty safe unless the ethanol is exposed to the air.
  6. Jun 10, 2015 #5


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    Gold Member

    What you're looking for may be pretty impractical to provide. The factors very hugely and the results will too.

    Here's a 4000+ gallon tanker going up in flames:
  7. Jun 10, 2015 #6


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    Staff: Mentor

    That's not right - a kilogram of ethanol is more like 27,000,000 Joules - you have misplaced a few digits.

    One gallon of ethanol weighs a bit less than seven pounds, about three kilograms. So your 4000 gallon tank is about 12000 kilograms (twelve tons) and about 300,000,000,000 Joules. That's the same amount of energy that would be released by the explosion of 50 tons of TNT, which would easily level several city blocks. Yes, pound for pound, liquid fuels like ethanol carry more energy than military explosives - that's because military explosives include oxidizers as well as fuel, whereas your ethanol tank is pure fuel.

    To get the full effect of a 300,000,000,000 Joule explosion, you'd have to take the entire tank of ethanol, carefully vaporize it and mix it with the exact right amount of air, and then ignite it. Small spills or vapor leaks won't burn the entire tank so would produce a smaller explosion - but that's still plenty of energy to wreck a building and kill a bunch of people. You don't need to be afraid of a 4000 gallon tank of ethanol, it's safe if it's treated with respect, but you should be afraid to be around people who won't treat it with respect.
    Last edited: Jun 10, 2015
  8. Jun 10, 2015 #7


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    Staff Emeritus
    Science Advisor

    Note that even though it may not be able to level a city block, a tank of alcohol would certainly pose a threat any nearby buildings just from the simple fact that its a liquid that can spread while burning.
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