Documentation:CHBE Exam Wiki/Final Exam 2016W/Question 2
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|Final Exam 2016W|
|Midterm Exam 1 2016W|
|Midterm Exam 2 2016W|
|Module 1 - Process Basics|
|Module 2 - Reactors|
|Module 3 - Separations 1|
|Module 4 - Separations 2|
|Module 5 - Non-reactive Energy Balances|
|Module 6 - Reactive Energy Balances|
A liquid mixture of 70 mol% n-hexane (C6H14) and 30 mol% n-heptane (C7H16) at 40°C is fed at a rate of 100 mol/s into a separating tank, known as a flash drum. In the flash drum, the temperature of the liquid is brought to 80°C and leads to the creation of a vapour phase. The vapour and liquid product streams can be assumed to be in equilibrium and are removed continuously at 80°C. The entire process operates at a uniform 1 atm pressure. Data for this system are provided below:
The Antoine equation is:
Table 1: Antoine equation coefficients for n-hexane and n-heptane, respectively
Table 2: Thermodynamic properties
|Compound||Cp [J/(mol K)]||Ĥvap[kJ/mol)]|
Note that Ĥvap can be assumed to be independent of temperature and pressure
Question 2a [25 points]
Calculate the n-hexane and n-heptane molar compositions in the vapour and liquid product streams as well as the product vapor and liquid stream molar flow rates.
Determine the components in Raoult's law which can be determined using the given operationing condition (P,T), before solving, do you have the information you need to solve this problem?
Using the Antoine equation, determine the vapor pressure of n-hexane(a) and n-heptane(b)
Using Raoult's law,
Using mole balance,
Rearranging the equations,
Question 2b [15 points]
Is energy being transferred to or from the separation tank and what is the amount of energy transferred in kW?
What are the enthalpy values for each components in the liquid and vapor streams leaving the flash drum?
How does energy balance come into play in this situation?
Determine the enthalpy values for all the streams,
For the liquid streams:
For the vapor streams:
Using energy balance
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