Distillation Theory

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Distillation Theory
Team 3: Robert Clifford, Patricia Firmin,
Gen Liang, Rooma Raza
The Basics of Distillation
Different Parts of Distillation
Condenser
Overhead Vapor
Overhead Product
Rectifying Section
Stripping Section
Reflux
Reboiler
Bottoms Product
Possible Feed Conditions
L-L
q=
F
V -V
q = 1+
F
McCabe-Thiele Graphical Method
Minimum Reflux Ratio
Optimal Feed Stage
Shortcut Method
• Fenske equation-minimum number of trays and split fraction
x lk (1 - x hk )
ln
x hk (1 - x lk )
Nm =
ln a lk /hk
N
a k x hk
xk =
N
1 + (a k -1)x hk
m
m
Tray Number and Reflux Ratio
blk = x lk
Ni =
{(a lk /hk
b hk = 1- x lk
12.3
-1)2/3 (1 - bi )1/6 }
N T = g N max i (N i ) + (1- g N ) min i (N i )
Ri =
{(a lk /hk
1.38
-1)0.9 (1 - bi )0.1 }
R = g R max i (Ri ) + (1 - g R ) min i (Ri )
Stage Efficiency
E0 = 13.3- 66.8log m
• Range from 41% to 88%
• For close-boiling mixtures, liquid viscosity is low, resulting in
high stage efficiency
Distillation Column Sizing
• Calculate column Diameter by Internal flowrates and design column
at 80% of linear flooding velocity.
A = p D 2 = V '/ (0.8Unf er g )
Unf = Csb (( rl - r g ) / r g ) (20 / s )
0.5
• If D> 3m = Parallel columns
0.2
Types of Distillation Columns
• Packed Bed Columns
 Used more often for absorption and
distillation of vapor-liquid mixtures.
 The liquid flows downward through the packing and
the vapor flows upward through the column.
• Advantages
 Cost efficient
 Lower pressure drop
 Good for thermally sensitive liquids
• Disadvantages
 Packing can break during installation
Types of Distillation Columns
• Tray Column
 The number of trays or stages is dependent
• Advantages
 Cost efficient
 Can handle high liquid flow rates
• Disadvantages
 Higher pressure drops than packed columns
 Foaming can occur due to agitation
Advanced Distillation
Extractive Distillation
Reactive Distillation
Vacuum Distillation
References
• Seader, J. D., Ernest J. Henley, and D. Keith. Roper. Separation Process
Principles: Chemical and Biochemical Operations. 3rd ed. Hoboken, NJ:
Wiley, 2011. Print.
• "ENCYCLOPEDIA OF CHEMICAL ENGINEERING EQUIPMENT." Distillation
Columns. N.p., n.d. Web. 11 Feb. 2015.
http://encyclopedia.che.engin.umich.edu/Pages/SeparationsChemical/Distill
ationColumns/DistillationColumns.html.
• Biegler, L., Grossmann, I., Westerberg , A., 1997, Systematic Methods of
Chemical Process Design, Prentice Hall.
• Bravo, Jose L. and James K. Fair. "Distillation Columns." Chemical
Engineering Progress January 1990: 19-29.

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