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Antoine equation and temperature range of flammability

  1. Nov 11, 2013 #1
    1. The problem statement, all variables and given/known data
    A number of accidents have occurred on site as a result if the discharge of static electricity generated by the flow of fluids. You have been asked to review enhanced safety during an acetone drum filling operation. Your engineering manager has asked you to gather some background information and using the “Antoine Equation” to suggest what temperature range should the drum filling operation avoid so that a flammable mixture of air-acetone would be prevented.
    The lower flammability limit of acetone vapour in air is ~ 2.55% by volume.
    The upper flammability level of acetone in air is ~ 12.8% by volume

    Q: What assumptions can we make?
    Q: What are we looking to find out?


    2. Relevant equations
    ##\boxed{\log_{10} p = A - \frac{B}{C + T}}##
    Where p is the vapour pressure, T is the temperature and A, B and C are component specific constants.


    3. The attempt at a solution
    Now, I'm not too sure how to actually use this equation to judge which temperature range to avoid given the information that I have. I've done a bit of reading about it on Wikipedia but haven't really found too much. Could somebody give me an idea of how to use this equation to find which temperature ranges to avoid?
     
  2. jcsd
  3. Nov 11, 2013 #2
    When you start filling the drum, the drum is going to be filled with air. As the liquid level rises in the drum, acetone is going to be evaporating into the air above it, and will be at its equilibrium vapor pressure at the interface. Since the total pressure is 1 atm., the air partial pressure at the interface will be 1 atm. minus the equilibrium acetone partial pressure. This gives you enough information to calculate the mole fraction of acetone in the gas at the interface.
     
  4. Nov 11, 2013 #3
    Thanks for that. Can I find the vapour pressure of the acetone using the Antoine Equation by subbing in for the 3 constants and using room temperature for T? Then, the atmospheric pressure minus the partial pressure of the acetone will be equal to the partial pressure of the air in the air-acetone mixture as you said. Is the following a correct method of finding a mole fraction of acetone in the acetone-air mixture at the interface?

    partial pressure of acetone/(partial pressure of acetone + partial pressure of air) = mole fraction of acetone.

    Thanks for the quick response to the question.
     
  5. Nov 11, 2013 #4
    Yes and yes.
     
  6. Nov 12, 2013 #5
    Thank you!
     
  7. Nov 12, 2013 #6
    Actually, what're the Antoine coefficients for Acetone? Each site I've checked has had different values.
     
  8. Nov 12, 2013 #7
    4.42448 1312.253 -32.445 Ambrose, Sprake, et al., 1974 Coefficents calculated by NIST from author's data.

    It's probably not going to matter much which set you choose, but these are the parameters recommended by NIST, where P is in bars.
     
  9. Nov 12, 2013 #8
    Great. Thanks for that.
     
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