A liquid stream containing 50.0mol% benzene and the balance toluene at 25°C at 5
ID: 921152 • Letter: A
Question
A liquid stream containing 50.0mol% benzene and the balance toluene at 25°C at 5.00 atm (abs.) is fed to a continuous single-stage evaporator at a rate of 1000mol/s. The temperature in the evaporator is maintained at 95°C and absolute pressure P (an unknown) by adding heat. The vapor and liquid phases, which are in equilibrium with each other, are separated and discharged as separate streams. The vapor stream contains 65.0mol% benzene.
Draw a fully labeled flow diagram, and do a degree-of-freedom analysis to confirm that all flows, compositions, and heat input can be solved.
Calculate
the evaporator pressure, P (atm),
the mole fraction of benzene in the liquid product, xB,
the volumetric flow rate of the vapor product, assuming that the vapor is ideal.
(c) An incomplete table of all input and output species, and their corresponding enthalpies, is shown below:
Inputs
Outputs
Species
Flow rate (mol/s)
(kJ/mol)
Flow rate (mol/s)
(kJ/mol)
Benzene (liquid)
500
0
9.802
Toluene (liquid)
500
0
1
Benzene (vapor)
2
Toluene (vapor)
34.278
What are the reference states for benzene and toluene?
Compute 1 and 2. (Values of properties of benzene and toluene needed for these calculations can be found in Table B.1)
Inputs
Outputs
Species
Flow rate (mol/s)
(kJ/mol)
Flow rate (mol/s)
(kJ/mol)
Benzene (liquid)
500
0
9.802
Toluene (liquid)
500
0
1
Benzene (vapor)
2
Toluene (vapor)
34.278
Explanation / Answer
Hello, the problem is incomplete, the analysis shows that one equation is missing, you need to specify another data.
Unknown Variable:
V; L; yB,L; yT,L; Q.
Equations:
1. F=V+L
2. Benzene Balance: FyB,F = VyB,V + LyB,L
3. yB,L + yT,L = 1
4. Q=V(yB,V)(HB,V) + L(yB,L)(HB,L) - F(yB,F)(HB,F)
5. unknown variables, 4 equations.
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