This document provides calculations for the rate of distillation and size of a vapor column for distilling triethyl amine. It calculates the total heat transfer area and rate of vaporization as 1410.218 kg/hr. The diameter of the vapor column is calculated as approximately 4 inches and the height is approximately 10 feet. Various equations and data are presented to illustrate the step-by-step calculations and determine the necessary parameters for designing distillation equipment.

1. Process Calculation: Simple Distillation
Chandran Udumbasseri
Technical Consultant
chandran.udumbasseri@gmail.com.
Part !: Rate of distillation & Vapor Column size
When a product is developed at laboratory scale the next step is pilot
plant trial and finally bulk trial. A reaction can be conducted with its
limitations but the separation and purification are the difficult and
expensive step in any process. Bulk trials can be started once the plant
is erected. After pilot plant trial it is necessary to calculate all parameters
required for designing the vessel, column and condensers
As an example distillation is taken for calculating parameters. Tri ethyl
amine distillation is taken for parameter calculation. This can help to
understand step by step process calculation
To calculate rate of distillation, total heat exchange area has to be found
out.
A reactor has a cylindrical body with two tori spherical bottom and top
dished ends. Usually the occupancy volume of the material is cylindrical
body with bottom tori spherical dished end.
The total heat transfer takes place on the surface of cylindrical body and
tori spherical surface of the bottom dished end
Surface area
Surface area of the cylindrical part
=πDh, D is the diameter of the cylinder and ‘h’ is the height of the
cylinder.
Surface area of tori-spherical dish
Total surface area

2. The height to diameter ratio is 1.5
So D = h/1.5
πDh = πD2
/1.5
Example:
Reactor volume =10000 liter
Occupancy = 75%
Occupancy volume = 10000x0.75 = 7,500 litters
= π(D2
/4)x1.5D + (π/24)xD3
= [(1.5/4) +(1/24)]x π x D3
=0.4167x π x D3
=7500x1000cm3
=1.308 D3
D3
=5733944.95
D = 178.985cm= 1.79m
Total surface area
= 3,14x1.79x1.5x1.79 + (3.14/4)x(1.147x1.79)2
=15.091 + 3.309 = 18.4 sq m
Rate of distillation
To illustrate, the distillation of triethyl amine under atmospheric pressure
and using steam as heating transfer utility is studied.

3. The reactor has a capacity of 10,000 lts (10KL). The material of
construction (MOC) is SS316. The working capacity is taken as 7.5KL. it
has a Heat transfer area of 18.4sq m.
The heat energy transferred heating area; 18.4 sq m is calculated using
the formula
Q = UxAx (t2-t1)
U = overall heat transfer coefficient
A = 18.4 sq m
t2 – t1 = 89-25 = 64
The value for U may be assumed as = 250 Kcal/Sq m /hr/K (metal of
construction, SS316)
Utility (steam) Temparature (incoming,) o
C,T1 100
o
F 212
Utility (ateam) Temparature (outlet) o
C, T2 100
o
F 212
Initial material temperature, o
C, t1 25
Final material temperature, o
C ,t2 89
Q = 250 (Kcal/Sq m /hr/K)x18.4(sq m) x 64 (o
C) = 294400 Kcal/hr
The material is heated from 25o
C to 89o
C (to the BP) and this is sensible
heat. The hot liquid needs to be vaporised at constant temperature 89o
C.
This is latent heat
Total heat required to vaporise = mass x latent
Latent heat of TEA = 82.61 Kcal/Kg K
Total latent heat = mass of vaporKg x 82.61 Kcal/Kg K

4. Total sensible heat
= Mass of material x Heat capacity x (t2-t1)
Mass of material = occupancy volume x density
= 7500 x 0.7255
Heat capacity = 0.51086 Kcal/Kg K
t2- t1 = 89-25 = 64
Sensible heat = 7500 x 0.7255 Kg x 0.51086 Kcal/Kg K x 64
= 177901.886 Kcal
Total heat load of the material = sensible heat + latent heat
294400 Kcal/hr = 177901.886 Kcal + mass of vapour Kg x 82.61 Kcal/Kg
K
Mass of vapour, Kg
= (294400 Kcal/hr - 177901.886 Kcal)/ 82.61 Kcal/Kg K
1410.218Kg/hr
Rate of vaporization/distillation = 1410.218Kg/hr
Vapour column size
Column diameter
Clausius-Clapeyron equation is used to find vapor pressure of the
boiled up vapor from the still
p1 = vapor pressure at T1

5. p2 = vapor pressure at T2
P can be in mm of Hg, Atm, etc
T is in Kelvin
ΔH = enthalpy of vaporisation, KJ/mol
R = 8.314 JKmol
Input data
P1 = 1atm
P2 = ?
T1 = 273 +25 = 298K
T2 = 273 + 89 = 362K
ΔH = 35 KJ/mol
P2 = 1.0025atm = 1.0025x750 = 763mm of Hg
Now calculating vapour volume usingideal gas law
PV = nRt
V = nRT/P
Boil-up = 1410Kg/hr
Mol weight = 101.19
T = 362K
P = 1.0025atm
V = 41832Lt/hr

6. = 41.832m3
/hr
= 42.832/3600 = 0.01162m3
/sec
Souders-Brown equation is used to calculate vapour velocity and cross
area
v = vapour velocity, m/s
tl = liquid density, kg/m3
rv = vapour density, kg/m3
Vapour velocity = 1.53m/s
The cross area is given by the following formula
D = 0.0982m
=0.0982x3.281 = 0.3222 x12 = 3.866 inch
Diameter of the column is = ~ 4” (Inches)
Height of the column
The vapour pressure is calculated above using Clausius-Clapeyron
equation, as
P = 763mm

7. But
P = hxdxg
h = height
d = vapour density, Kg/m3
= 3.5Kg/m3
g = 9.81m/s2
1mm = 133.322Pa
h = P/dg
=2.96m = 2.95x3.281 ft= 9.71ft
The height of the vapour column is ~ 10 ft
Data Used
The above calculations are based on the following books. The below
data are collected from books like
 PROCESS HEAT TRANSFER: Donald Kern
 Chemical Process Equipment: James Couper, Rony Penney,
etc
 Chemical Engineering design: Richardson & Coulson
Overall heat transfer coefficient for metal pipes
Type Application Overall heat transfer
coefficient, U
W/m2
/K Btu/ft2
/F
Tubular
heating/cooling
Gas at atmospheric pressure
inside and outside
5-15 1-0
Gas at high pressure inside and
outside
150-500 25-90
Liquid inside and gas outside
vice versa
15-70 3-15
Gas at high pressure inside and
liquid outside
200-400 15-70

8. Liquid inside and outside 150-1200 25-200
Steam outside and liquid inside 300-1200 50-200
Condensation Organic vapour outside/cooling
water (CW) inside
300-1200 50-200
Tubular
evaporation
Steam outside/high viscous
liquid inside
300-900 50-150
Steam outside/low viscous liquid
inside
600-1700 100-300
Steam outside/liquid inside
forced circulation
700-3000 150-300
Air cooled
exchanger
CW 600-700 100-130
Cooling lighr hydrocarbon 400-500 70-95
Cooling of tar 30-60 5-10
Cooling ofair/flue gas 60-100 10-20
Cooling of hydrocarbon gas 200-400 35-50
Condensation of low pressure
steam
700-800 125-150
Condensation of organic vapour 250-500 65-90
Plate heat
exchanger
Liquid to liquid 1000-
4000
150-700
Data of Triethyl amine
Tri ethyl amine
Molecular weight,g/mol
101.18
Density g/ml 0.7255
Kg/Cu m 725.5
Lb/cu ft 45.2915
Vapour Density, Kg/m3
3.5
Heat capacity, J/mol/K 216.43
BTU/lbmol 93.0478
Kcal/Kg K
0.51086
Latent Heat of Vaporization, KJ/mol 35
Kcal/Kg K 82.613
Btu/lb 148.604

9. Viscosity , cP/Kpas 0.363
KPas 0.363
lb/ft-sec 0.24395
Steam
Utility Temparature (incoming,)C 100
o
F 212
Utility Temparature (outlet)C 100
o
F 212
Specific heat,( at 100C), KJ/Kg 4.18
Kcal/Kg.K 1
Latent Heat of steam at 1atm, KJ/kg 2257
Kcal/Kg 539.952
Part II: Condenser/Shell and Tube Heat Exchanger (Next Issue)