(1) For a separations process it is necessary to determine the VLE compositions of a mixture of ethyl bromide and n-heptane at 30°C. At this temperature the vapor pressure of pure ethyl bromide is 0.7569 bar, and the vapor pressure of pure n-heptane is 0.0773 bar. Calculate the bubble pressure and the composition of the vapor in equilibrium with a liquid containing 47.23 mol% ethyl bromide assuming ideal solution behavior. Compare the calculated pressure to the experimental value of 0.4537 bar.
(2) Consider a mixture of 50 mol% n-pentane and 50 mol% n-butane at 14 bar.
What is the dew-point temperature? What is the composition of the first drop of liquid?
At what temperature is the vapor completely condensed if the pressure is maintained at 14 bar? What is the composition of the last drop of vapor?
(3) A 50 mol% mixture of propane(1) and n-butane(2) enters an isothermal flash drum at 37°C. If the flash drum is maintained at 0.6 MPa, what fraction of the feed exits as liquid? What are the compositions of the phases exiting the flash drum? Work the problem in the following two ways.
Use Raoult's law (use the Peng-Robinson equation to calculate pure component vapor pressures).
Assume ideal mixtures of vapor and liquid. (Use the Peng-Robinson equation to obtain fsat for each component.)
(4) Use Raoult's law to estimate the flash point temperature for the following equimolar liquid mixtures in an air atmosphere at 750 mmHg total pressure:
Pentane (LFL = 1.5%) and hexane (LFL = 1.2%)
Methanol (LFL = 7.3%) and ethanol (LFL = 4.3%)
Benzene (LFL = 1.3%) and toluene (LFL = 1.27%)