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Process design of distillation column
Diagram
Feed
Distillate
Bottom
Cumene 0.996Phenol 0.004
Xd
Cumene 0.0016Phenol 0.9984
Xb
Cumene 0.17Phenol 0.83
Xf
Feed composition
Feed stream composition
Feed Mass(Kg/hr)
Phenol 277.452
Cumene 66.972
AMS 4.381
Cont…
Since the amount of AMS in feed stream is negligible and its properties resembling close to cumene. Hence it can be merged with cumene for easier calculations.
Feed Mass(Kg/hr) Mass(Kgmol/hr)
Xf
Phenol 277.452 2.948 0.83
Cumene 71.353 0.594 0.17
Calculation for bottom temperature
Bottom pressure = 1.28 atm = 972.8 mmHg
Using Antoine equation
Antoine equation constants for phenol
A = 16.4279B = 3490.89C = -98.59
Cont…
Putting the constants in above equation
The top temperature as given in process conditions is
Taking avg temperature
Now taking the average of these temperatures
Calculating vapour pressure of cumene Using antoine equation
Here = 171.86
The following are the antoine constants for cumene
A = 13.957B = 3363.3C = 207.78
Cont…
Putting the values in eq above
Calculating vapour pressure of phenol Using antoine equation
Here = 171.86
The following are the antoine constants for phenol
A = 14.4387B = 3507.80C = 175.4
Cont…
Putting the values in eq above
Calculating relative volatility
Putting the corresponding values of pressure in above eq
The following corresponding vapor-liquid relation is obtained
X .002 .02 .10 .20 .30 .40 .50 .60 .70 .80 .90 1.0
Y .004 .043 .19 .35 .49 .60 .69 .77 .84 .90 .95 1.0
VLE diagram Since the feed is entering at its boiling point hence q-line is vertical
0 0.2 0.4 0.6 0.8 1 1.20
0.2
0.4
0.6
0.8
1
1.2
VLE Diagram
Calculating minimum reflux ratio
So from graph Φm = 0.165
Calculating maximum reflux ratio
Taking
Calculating the number of theoretical and real plates required
Here obtained from the graph
Assuming efficiency = 75%
Calculating flooding velocityAt top plate
At bottom plate
Density at top
Cont…Density at bottom
Surface tension Top Cumene = 29.01 mN/m Bottom Phenol = 37.66 mN/m
Top = 0.05880 Bottom = 0.0849 Tray spacing = 0.30m
Figure
Cont…So from the previous figure Top Bottom Surface tension correction Top Bottom Flooding velocity Top Bottom
Cont… Design for 85% flooding velocity at max flow rate Top Bottom
Max vol.flowrate of vapour Top Bottom Net area required Top Bottom N
Calculating column area and diameter Downcomer area = 12% of column area
Top Bottom Column diameter Top Bottom