Bubble Point /w Antoine Equation

Computer Methods in Chemical Engineering


Problem Statement: The following Antoine equation describes the dependence of vapor pressure of a pure chemical species i on temperature.

    log10(P*i) = Ai- Bi/(T+Ci)
The coefficient A, B, and C for a few select species are tabulated below. P is expressed in mmHg, and T is expressed in Celsius degree.
                            Antoine Coefficients    liquid mole fraction
  formula  species    ID     A       B       C             (x)
  ----------------------------------------------------------------------
  C6H6     benzene     1  6.90565 1211.033 220.790         0.2
  C7H8     toluene     2  6.95464 1344.800 219.482         0.2
  CHCL3    chloroform  3  6.93710 1171.200 227.000         0.2
  C3H6O    acetone     4  7.23160 1277.030 237.230         0.2
  CH4O     methanol    5  8.07240 1574.990 238.870       balance
For a multicomponent system, component i in the liquid phase generates a vapor pressure proportional to its liquid phase mole fraction xi.
  Pi = xi*P*i
The total vapor pressure is the sum of the individual component vapor pressure.
  Ptotal = Si(Pi) = Si(xi*P*i)
  Ptotal = sumi(Pi) = sumi(xi*P*i)    (If you do not see the summation sign)
Given Ptotal=760mmHg, find the temperature T such that the last equation is satisfied. (This temperature is called the boiling point or the bubble point, because when the total vapor pressure equals that of the surrounding, the mixture bubbles and boils. In addition, find the vapor phase composition from the following equation:
  yi=Pi/Ptotal

Solution:


Modify the solution to the above problem so that that the worksheet can calculate the bubble point of a mixture that contains any of the 700 chemical species for which data are available in antoine.dat. Source of data: Yaws and Yang (Yaws, C. L. and Yang, H. C., "To estimate vapor pressure easily" Hydrocarbon Processing, October, 1989, p65.) Since Mathcad cannot read the header information well and has a default file extension of .PRN, I edited the file antoine.dat a bit for your convenience (download antoine.prn).

Solution:


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Computer Methods in Chemical Engineering -- Bubble Point /w Antoine Equation
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