Question 1. An aqueous solution of furfural contains 4 mol%furfural. It is to be continuously fractionated at 1 stdatm pressure to provide solutions containing 0.1 and 99.5 mot% furfural respectively. Feed is liquid at bubble point. Equilibrium data is given as:
| t,°C |
x |
y•
|
t,°C
|
X
|
y•
|
| 100. |
0 |
0 |
100.6
|
0.80
|
0.11
|
| 98.56 |
0.01
|
0.055
|
109.5
|
0.90
|
039 |
| 98.07 |
0.02
|
0.080
|
122.5
|
0.92
|
0.32 |
| 97.90 |
0.04
|
0.092
|
146.0
|
0.94 |
0.64 |
| 97.90 |
0.092
|
0.092
|
154.8
|
0.96 |
0.81 |
| 97.90 |
0.50
|
0.092
|
158.8
|
0.98 |
0.90 |
| 98.7 |
0.70
|
0.095
|
161.7
|
1.00 |
1.00 |
x,y refers to furfural. (i) Arrange a scheme for the separation using kettle-type reboiters, and determine the number of theoretical trays required for a vapor boilup rate of 1.25 times the minimum for an infinite number of trays. The overall efficiency of the stage is 0.7.
(ii) Repeat part (i) but use open steam at essentially atmospheric pressure for the tower delivering the water-rich product, with 1.25 times the minimum steam and vapor boilup rates.
(iii) Which schemes incurs the greater furfural loss to the water rich product?
Question 2. A distillation column is used to separate an equimolar binary mixture of A and B to the distillate rate of 1 mol/s. The purity of distillate is 98mol%. The mole fractions 'x' and 'y' of A in any nth tray in column are 0.7 and 0.83. On n+1 tray it is 0.6 and 0.75. Assuming the latent heat of vaporization are same for all mixtures and the feed is saturated liquid, determine
(i) number of theoretical stages and feed tray location when Murphree tray efficiency is 0.7
(ii) Internal liquid and vapor flow rates
(iii) Minimum number of theoretical stages
(iv) Number of theoretical stages in enriching and stripping sections when feed is saturated vapor.
(v) If the vapor velocity is 6m/s determine the diameter of the column.