Calculation of theoretical stages: McCabe Thiele method

1
Calculation of theoretical stages McCabe
Thiele method
Vapour
Reflux
1
n
Feed
Feed stage
m
Vapour
N
Liquid
2
Assumptions

• Vapour and liquid phases leaving each stage are
  in equilibrium
• Sensible heat changes in a stage are small
• Equimolar overflow

For nth stage
Vn yn
Ln-1 xn-1
n
Vn1 yn1
Ln xn
3
Overall balance
Heat out
Distillate
Condenser
D xD
Reflux
Column
Feed
F xF
Heat in
Reboiler
Bottoms
W xW
4
Enriching section Scheme
1
D xD
2
Ln-1 xn-1
n
Vn1 yn1
Ln xn
F xF
5
Enriching section Balance
y
xD
x