Design of Distillation Col

Short Cut Method

Prof. S. BasuDept of Chem Eng.

IIT Delhi

web.iitd.ac.in/~sbasu/

f01_12

Column Selection

Step VI

Step VII

S

P

V

g

LIQUID FUGACITY COEFFICIENT - ESTIMATED FROM EQBM. STATE

L

LIQUID FUGACITY COEFFICIENT - ESTIMATED FROM EQBM. STATE

α

ψ

γ

Fenske

X

No of moles of saturated liq. produced per mole of feed on the feed tray

w.r.t.

x

C

D

Di/HK

Bi/HK

L feed T

ay

N = M + P

A liquid feed of 100 mol/h at the boiling point is fed to distillationcolumn at 405.3 kPa and is to be fractionated so that 95 % of the n-pentane (B) is recovered in the distillate and 95 % of the n-hexane (C) in the bottoms. The feed composition is as follows: n-butane (XA = 0.40), n-pentane (XB = 0.25), n-hexane (XC = 0.20), n-heptane (XD = 0.15). Calculate the following:1. Moles per hour and composition of distillate and bottoms2. Top and bottom temperature of tower3. Minimum no. of stages for total reflux and distribution of other components in the distillate and bottoms4. Minimum reflux ratio and number of theoretical stages at R = 1.3 Rm5. Location of feed tray

[K values is supplied]

Multi-Comp. Distillation Design Short-Cut MethodExample Problem

A

X

y

D

D

N

Com D

O

D

1

E

Rigorous Calculation

Design of Distillation Col

Prof. S. BasuIIT Delhi

web.iitd.ac.in/~sbasu/

MESH EQUATIONS

M – MATERIAL BALANCESE – EQUILIBRIUM EQUATIONS – SUMMATION EQUATIONH – ENTHALPY OR ENERGY BALANCES

i – components - Cj – no. of stages - N

Methods for solving MESH equations

• Boiling point method• Sum rate method

M- eqn

Generation of TDM

B

X

f10_04

H – eqn.

(Use M- eqn + E / S eqn summed over all stages and comp.)

h hV

H – eqn and Total Material Balance

V2

Convergence criteria

f10 07

f10 16