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Distillation Column: Study and Design | 2015-16 DECLARATION BY THE SCHOLAR I hereby declare that this submission is my own and that, to the best of my knowledge and belief it contains no material previously published or written by another person nor material which has been accepted for award of any other Degree or Diploma of the University or other Institute of Higher Learning except where the acknowledgement has been made in the text. Akash Sood (R900213004) Avinash Kumar (R900213014) Prashun Pankaj (R900213031) Ravi Patel (R900213028) pg. 1

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Page 1: Final Report Minor_Final Draft

Distillation Column: Study and Design | 2015-16

DECLARATION BY THE SCHOLAR

I hereby declare that this submission is my own and that, to the best of my knowledge and belief it contains no material previously published or written by another person nor material which has been accepted for award of any other Degree or Diploma of the University or other Institute of Higher Learning except where the acknowledgement has been made in the text.

Akash Sood (R900213004)Avinash Kumar (R900213014)Prashun Pankaj (R900213031)Ravi Patel (R900213028)

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CERTIFICATE

This is to certify that the thesis titled Distillation Column: Study and Design submitted by Akash Sood (R900213004), Avinash Kumar (R900213014), Prashun Pankaj (R900213031) and Ravi Patel (R900213028), to the University of Petroleum & Energy Studies, for the award of degree of Bachelor of Technology in Chemical Engineering is a bonafide record of project work carried out by them under my supervision and guidance. The content of the report, in full or parts have not been submitted to any other Institute or University for the award of any other degree or diploma.

Mr. Giridhar VadicharlaAssistant Professor,Department of Chemical Engineering,University of Petroleum and Energy Studies, Dehradun

Date:

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ACKNOWLEDGEMENT

This project has been a great opportunity for learning and self-development. We consider ourselves to be very providential and truly honored to have so many wonderful individuals, who have helped us in various ways throughout the duration of the project.

We are grateful to University of Petroleum and Energy Studies, for giving us such a wonderful project to work on. We would like to extend our deepest thanks to our mentors Dr. Parichay Das and Mr. Giridhar Vadicharla without whose guidance this project would have not been possible. We would also like to thank Mrs. Rose Havillah Pulla for her support during the duration of the project.

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ABSTRACT

Most of the processes in chemical industry are involved in purifying components. As a consequence, a large part of the energy use in many industrial sectors can be attributed to separation processes. Distillation is the dominant separation technology in chemical industries despite its huge energy consumption. Distillation consumes about 3% of the total energy consumed globally. The knowledge about distillation column is very important to every chemical engineering student. This project involves a detailed study of distillation column pre-installed in mass transfer operations lab. All the parts of the distillation setup are studied in depth and observations are noted down. During the project the limitations in the working of current setup are to be identified and worked upon. At the end of the project it is to be ensured that the distillation column gives precise output with minimum error keeping in mind the manual and operational limitations. Also the operation time is to be optimized.

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TABLE OF CONTENTS

1. Certificate 2

2. Acknowledgement 3

3. Abstract 4

4. List of Tables 6

5. List of Figures 7

6. Introduction 8

7. Literature Review 9

8. Materials and Methodology

i) Details of setup…………………………………………………………………..10

ii) The McCabe-Thiele method…………………………………………………......12

iii) Packed bed distillation column……………………………………………….….19

iv) The experiment…………………………………………………………………..27

9. Result and Discussion 30

10. Conclusion 31

11. References 32

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LIST OF TABLES

1. The equilibrium data of methanol and water at 1 std. atm. 15

2. Observation table for calibration chart 28

3. Observation table for the experiment 28

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LIST OF FIGURES

1. Simple distillation column setup to help get an idea of the process 12

2. Complete distillation setup 13

3. Example of application of McCabe-Thiele Method 13

4. Illustration of number of stages from McCabe-Thiele Method 14

5. Vapour Liquid Equilibrium Curve for methanol-water system at 1 std. atm. 15

6. Vapour Liquid Equilibrium Curve for methanol-water system at 1 std. atm. 17

7. Graph using McCabe-Thiele Method for given setup 18

8. Graph using McCabe-Thiele Method for the batch distillation column to be designed 21

9. Properties of different types of packings 22

10. Generalised flooding and pressure drop correlation for packings 24

11. Calibration chart for methanol – water 29

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CHAPTER - 1

INTRODUCTIONDistillation is a physical process for the separation of liquid mixtures that is based on differences in the boiling points of the constituent components. Distillation is the most widely used separation process used in many industries. A distillation column consists of two sections. The section above the feed tray is called the rectification section and the section below the feed tray is called stripping section. Rectifying section enriches with more volatile components and stripping section enriches with less volatile components. The separation process requires three things. First, a second phase must be formed so that both liquid and vapor phases are present and can contact each other on each stage within a separation column. Secondly, the components have different volatilities so that they will partition between the two phases to different extent. Lastly, the two phases can be separated by gravity or other mechanical means. Distillation differs from absorption and stripping in that the second phase is created by thermal means.

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CHAPTER - 2

LITERATURE REVIEWDistillation is the most important separation method in the chemical industry. Due to greater advantages like less time consumption, better efficiency and ability to treat high volumes, the continuous distillation process is widely used. However, interest in batch distillation still remains as it is economical for small scale industries and some sectors like pharmaceutical prefer batch distillation for their operations. This can also be seen from the fact that volume of literature for batch distillation has almost doubled since 1980. The liquid and vapour compositions on any tray in a batch distillation column vary with time and depend on a number of factors including the number of stages in the column, the reflux ratio and the thermodynamic properties of the components involved.

Batch distillation is an important unit operation frequently used in small scale, high value added chemicals and bio-chemicals industries. It is very useful in the separation of mixtures which become more viscous on concentration. Because of its flexibility in handling feeds of variable concentration and different mixtures, it is also used in multiproduct and multipurpose plants. In the separation of a multi component mixture, batch distillation is often preferred because complete separation can be achieved in a single column whereas with continuous distillation, several columns may be required. Another area where batch distillation finds great application is in the distillation of complex systems and of systems with greater difficulty of separation. This includes the distillation of close boiling and thermodynamically complex systems (azeotropic mixtures) and distillation accompanied by a chemical reaction. The latter is termed reactive batch distillation and considers the case where reaction occurs only in the reactor vessel, which acts as the still (Wilson and Martinez 1995), or a more complicated case where reaction occurs both in the reactor vessel and the distillation column (Albet et al 1991).

Mujtaba (2004) is a complete guide to design, model and dynamic optimize batch distillation, and will be used to optimize and design an experiment.

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CHAPTER - 3

MATERIALS AND METHODOLOGYDifferent parts of the set-up and their details are:

Distillation Column:

Size: 110mm diameter and 1500 mm height

MOC: SS304

Insulation: 25mm thick glass wool insulation and SS 304 cladding

Sight glass: Three sight glass

Tray:

Type: Sieve tray

MOC: SS304

Internals: With necessary downcomer and weir

Condenser:

Type: Horizontal shell and tube type, BEM, 1-1 pass type

Size: 75 mm diameter and 500 mm length

Tube: 12 mm diameter, 12 numbers of tubes

MOC: SS 304

Insulation: 25mm thick glass wool insulation and SS 304 cladding

Steam Generator:

Type: Kettle type

Size: 300mm diameter and 500 mm length

Heaters: 8kW Ni-Cr heater (2*4 kW)

Insulation: 25mm thick glass wool insulation and SS 304 cladding

PID Controller:

Purpose: For heaters

Input: Universal

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Output: 4-20 mA

Display: LED

Accuracy: 1% of full scale

Power Supply: 230 V AC, 5 amp

Reflux Drum:

MOC: SS304

Capacity: 2.5 liters

Glass: Toughened glass on one side for visualization

Feed Tank:

MOC: SS 304

Capacity: 30 liters

Accessories: Valve, glass tube liquid level indicator, drain valve, vent valve, feed valve

Distillate tank:

MOC: SS304

Capacity: 15 liters

Accessories: glass tube liquid level indicator, drain valve and feed nozzle

Water supply tank:

MOV: SS304

Capacity: 50 liters

Accessories: glass tube liquid level indicator and drain valve

Water supply pump:

Power: 0.5 HP

MOC: SS housing-suitable for warm water application

Flow meter:

Type: Rota meters

Feed: 3-30 LPH

Distillate: 1.5-15 LPH

Reflux: 1-10 LPH

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Bottom: 1-10 LPH

Cooling water: 1-10 LPM

Reboiler:

Type: Thermosyphon vertical reboiler

Shell side: Bottom product (majorly water)

Tube side: Compressed steam

The McCabe-Thiele Method

This method uses the equilibrium curve diagram to determine the number of theoretical stages (trays) required to achieve a desired degree of separation. It is a simplified method of analysis making use of several assumptions, but nonetheless a very useful tool for the understanding of distillation operation.

The VLE data must be available at the operating pressure of the column. Information required are the feed condition (temperature, composition), distillate and bottom compositions; and the reflux ratio, which, as we seen earlier, is defined as the ratio of reflux liquid over the distillate product. This is shown in the Figure below:

For example, a column is to be designed for the separation of a binary mixture. The feed has a concentration of xF (mole fraction) of the more volatile component, and a distillate having a concentration of xD of the more volatile component and bottoms having a concentration of xB are desired.

In its essence, the method involves the plotting on the equilibrium diagram 3 straight lines: the rectifying section operating line (ROL), the feed line (also known as the q-line) and the stripping section operating line (SOL).

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Each of these lines passes through the points representing the mole fractions of the more volatile component in the distillate, bottoms and feed (xD, xB andxF) respectively. These lines represent the relationship between the concentrations in the vapor phase (y) and the liquid phase (x).

The number of theoretical stages required for a given separation is then the number of triangles that can be drawn between these operating lines and the equilibrium curve. The last triangle on the diagram represents the reboiler.

To obtain the number of theoretical trays using the McCabe-Thiele Method, we use the "Parts-Whole Relationship": analysis is first carried out by partitioning the column into 3 sections: rectifying, feed and stripping sections as shown in left Figure below. These sections are then represented on the equilibrium curve for the binary mixture in question and re-combined to make a complete design, as shown in the right Figure

In the simplest case, the McCabe-Thiele Method to determine the number of theoretical stages follows the steps below:

1. Analysis of the Rectifying section, and determine the ROL using xD and R2. Analysis of the Feed section, and determine the feed condition (q)3. Determination of the feed line (q-line) using xF and q4. Locate the intersection point between ROL and q-line5. Analysis of the Stripping Section, and determine the SOL using (4) and xB

When R is unknown (but instead specified as a multiple of the minimum rate), we first determine the q-line. Usually the SOL is the last line to draw, after both ROL and q-line are drawn. Fixing

the ROL and the q-line automatically fixes the SOL. On the completed design (equilibrium diagram): The number of triangles drawn = Number of theoretical trays + 1 Reboiler (last

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triangle).As an example, see the Figure below. The number of theoretical trays = 6 + 1 Reboiler

The feed plate location can also be determined. In the example above, it is Tray 3.

The following parameters have been calculated in steps in the course of the study apt for the distillation column:

1. Operating pressure of the distillation column: 1 atm

Boiling point of water: 100°C (at 1 std atm)

Boiling point of methanol: 64.7°C (at 1 std atm)

As methanol has lower boiling point than water at operating pressure of the distillation column, therefore it is the more volatile component and will be the basis of the calculations of XF, XD and XB.

2. Feed composition selected: 50 wt % methanol and 50 wt % water

Feed composition, xF =

5032

5032

+5018

= 0.36

Degree of separation of distillate selected: 95 wt % methanol and 5 wt % water

Distillate composition, xD =

9532

9532

+ 518

= 0.914

Degree of separation of bottom selected: 30.78 wt % methanol and 69.22 wt % water

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Bottom composition, xB =

30.7832

30.7832

+ 69.2218

= 0.2

3. The equilibrium data of methanol-water separation at 1 std atm obtained is:

X 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Y 0 0.42 0.58 0.66 0.73 0.78 0.82 0.87 0.91 0.96 1T( C) 100 87.7 81.7 78 75.3 73.1 71.2 69.3 67.6 66 64.5

Fig: Methanol-Water Equilibrium Data (Source: Perry’s Handbook, 7th edition)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

140

150

160

170

180

190

200

210

220

VLE for MeOH/H2O system @ 1 atm

Liquid Vapor

MeOH Content (mole fraction)

Temp

eratu

re (o

F)

Source: Distillation Column Design (Methanol-Water) published by Prasanna Welahetti (Chemical & Process Engineering, University of Moratuwa)

4. We know that when composition is equal to feed composition i.e.xF, the temperature of the feed is equal to the bubble point temperature of the feed (tBP).

From the graph shown above, the temperature corresponding to xF = 0.36 is 77°C.

Therefore, Bubble point of feed, tBP = 77°C Feed temperature selected, tF = 30°C (as feed is entering at room temperature)

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Average temperature, tavg = 77+30

2 = 53.5°C

5. Calculation of q value:

q=λF+CPF (tBP−tF)

λF

Where,tBP – Bubble point of feedtavg – Average temperatureλF – Latent heat of methanol-water feed mixture at tBP

CPF – Heat capacity of methanol-water feed mixture at tavg

From Perry’s handbook,Latent heat of water at 77°C (tBP), λW = 4.19 x 104 J/molLatent heat of methanol at 77°C, λM = 3.46 x 104 J/molTherefore, λF = (xF*λM) + ((1-xF)*λW)

= ((0.36)*(3.46 x 104)) + ((0.64)*(4.19 x 104)) = 39334.72 J/mol

From physical properties data software by David Himmelblau (2000),Heat capacity of water at 53.5°C (tavg), CPW = 74.419 J/mol-KHeat capacity of methanol at 53.5°C, CPM = 84.499 J/mol-KTherefore, CPF = (xF*CPM) + ((1-xF)*CPW)

= ((0.36)*(84.499)) + ((0.64)*(74.419)) = 79.7902 J/mol-K

After putting values, we get, q = 1.087

6. Equation of q line:

y=( qq−1 )x−

x F

q−1

After putting values of xF and q, we gety = 12.49x – 4.14

7. The vapour liquid equilibrium curve:

From the VLE data mentioned in point 3, an equilibrium curve is drawn.

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

VLE for MeOH/H2O system @ 1 atm

Equilibrium Diagonal

x (mole frac MeOH)

y (mo

le frac

MeOH

)

8. Calculation of theoretical number of stages:a) Points xF, xD and xF were marked on the diagonal of the equilibrium curve shown

above.b) From xF, the q line was drawn till it cut the equilibrium curve (say point A).c) Points xD and A were joined and extended till the y-axis.

d) The intercept on y-axis = 0.59 = xD

Rm+1 , where Rm = minimum reflux ratio.

e) On putting value of xD, we get, Rm = 0.549f) For industrial apparatus of distillation column,

R = 1.2 Rm = 0.6588

g) Intercept of rectifying section operating line (ROL) on y-axis = x D

R+1 = 0.551

h) The above intercept was marked on the y-axis and joined with point XD which gave the ROL. The point where it cut the q line (say B) was marked.

i) The points B and XB were joined to get the stripping section operating line (SOL).Then the steps were constructed according to the McCabe Thiele method.

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9. We get the number of ideal stages = 8 which is shown below:

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Packed bed batch distillation column

After working on the existing set up, calculations were made for designing a new packed bed distillation column which we propose to set up. In the process we calculated HETP, column height and tower diameter. We also calculated other required data as follows:

Modelling calculation for packed bed distillation column

The current setup is based on the 1 Kg mass basis.

The initial feed consists of 50% methanol by mass and 50% water by mass.

The top product must contain 95% methanol by mass and the bottom product must contain 77% water by mass.

Therefore,

F={[(0.5)/32]+[(0.5)/18 ]}=0.0434 Kmol

Mole fraction of methanol in feed is given by,

xF=(0.5/32) /0.0434=0.36

Mole fraction of methanol in distillate is given by

xD=(92.24/32)/((92.24 /32)+(7.76 /18))=0.87

Mole fraction of methanol in residue

xB=(19.52/32)/(( 19.5232 )+( 81.48

18 ))=0.2

Now,

D=F−B

¿ F (xF−xB)/(xD−xB)

¿0.0434∗(0.36−0.2)/ (0.87−0.2)

¿0.010 Kmol

Therefore,

B=0.0334 Kmol

Now to calculate Rm

Rm=( L

V )min

1−( LV )

min

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Where,

( LV )

min=( yD− yPI )/(x D−x PI)

From Graph,

xD=0.87

y D=0.94

xPI =xF=0.36

Corresponding equilibrium value of y

y PI= yF=0.71

( LV )

min=(0.94−0.71)

(0.87−0.36)=0.4509

Let the reflux ratio be R=3Rm at the start of the batch distillation,

R=3∗0.4509=2.46

Therefore the slope of the operating line = (R/ (R+1))=(L/V )

¿(2.46/(2.46+1))

¿0.71

Intercept of the operating line,

xD /(R+1)=0.25

Equilibrium Cure is plotted from the X-Y data available.

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And from the graph the number of stages obtained is 5.

Time required for batch distillation and with constant overhead composition is given by Bogart equation.

θ=F (xD−xF)

V ∫xB

xF d xB

(1− LV )( xD−x B )2

θ=0.0434 (0.87−0.36)

V ∫0.2

0.36 d xB

(1− LV )( xD−xB )2

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Graph is plotted for above equation and from there we get the area under the curve and correspondingly we get Vθ. Then by fixing time we get the vapor flow rate.

Θ=0.0434 (0.87−0.36 )

V∗(0.8514 )

Vθ = 0.01884

If the batch distillation time is fixed,

Θ=3h r4

V=0.01884∗43

=0.0251 Kmolh

Design of the distillation column

Type of tower: Packed Tower

Type of packing: Raschig rings

Size of packing = 6mm

Void spacing= 62%

Packing factor Fp=5250 m-1

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Tower diameter required at the bottom,

FLG=Lw

Gw( ρG

ρL)

12

Molar Flow rate of vapor, V=0.0251 kmol/h

V=L+D

AndL/ D=R

L=RD

L=2.46 D ,

V=L+D=2.46 D+D=3.46 D ,

D=V /4=0.0251/4=0.00725

L=0.017 Kmol /h

At the start of distillation,

M av=(0.36∗32)+{(1−0.36)∗18 }

=11.52+11.52=23.04 Kg / Kmol

Lw

Gw= L

V= 0.017

0.0251=0.67

Bubble temperature at x = 0.36, T = 76.38°C

Density of methanol at 76.38°C = 738.982 kg/m3

Density of water at 76.38°C= 964.711 kg/m3

ρG=P M av / RT=(101.325∗23.04)/(8.314∗349.38)=0.8037 Kg /m3

ρL=1/¿

FLG=0.75∗((0.8037 /836.855)0.5)=0.0232

From flooding correlations,

K f =0.24

Let the actual velocity of the vapor through packed tower = 70% of flooding velocity

( KK f

)0.5

∗100=70

K=(0.7)2∗K f =0.12

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Corresponding △P = 83.3mm WC/m of packing.

Gw=[ K ρG ρL gFP Ψ ( µL )0.2 ]

12

Viscosity of 50% methanol solution (by mass) at 76.78oC, µL = 0.35 mPa-s

Gw=[ 0.12∗0.8037∗836.855∗9.815250∗1.15278∗(0.35 )0.2 ]

12=0.082 Kg

m2 s

Mass flow rate of vapor,

mv=0.0251∗23.04=0.58428 Kgh

=1.623 X 10−4 Kgs

Arearequired at bottom, A=1.623 X 10−4

0.082m2=1.96 X 10−3 m2

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Now,

A=( π4 )Di

2

Therefore Di = 5 cm

Tower diameter required at top,

FLG=Lw

Gw( ρG

ρL)

12

Lw

Gw= L

V=0.67

M av=(0.914∗32)+((1−0.914)∗18)=30.796

T dew=65.72 ᴼc

ρG=¿

P M av

RT = (101.325 )(30.796)(8.314)(273+65.72)

=1.10805 kgm3 ¿

ρL=denstiy of methanol=747.903 kgm3

FLG=0.67 (1.10805747.903 )

12=0.025

From the graph

K F=0.19

Let actual velocity of vapour is equal to 70% of the flooding velocity,

K=(0.7)2 KF=0.0931

From the graph,

ΔP = 83.3 mm WC/m of packing

Gw=[ K ρG ρL gFP Ψ µL

0.2 ]12

Ψ =density of waterdensity of liquid

=972.167747.903

=1.299

µL=0.30941 mPa−s

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Gw=[ 0.0931∗1.10805∗747.903∗9.815250∗1.299∗0.30940.2 ]

12=0.061 Kg

m2 s

Mass flow rate of vapour,

mv=0.0251∗30.796=0.773 Kgh

=2.15 X 10−4 Kgs

Area required at top=

Arearequired at top=(2.15 ×10−4)

0.061=3.52× 10−3 m2

Di = 0.06 m = 6 cm

Therefore, diameter of the tower = 6 cm (for entire tower)

Height of packing

H= HETP × N

N= Number of theoretical stages

HETP= Height of equivalent of a theoretical plate

H= Height of packing

Value of HETP can be determined by modified by Granville equation

HETP =

HETP =

HETP

HETP13

=28∗6∗0.001∗ma∗(0.67)( 52.4

)13

HETP23=28∗6∗0.001∗ma∗0.67∗1.6091

HETP23=0.18112ma

Calculation of average top

1. tan 26° = 0.4872. tan 27° = 0.5093. tan 32° = 0.6244. tan 38° = 0.781

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5. tan 52° = 1.279

∑m = 3.68

n = 5

Therefore, mav = 0.736

Therefore, HETP = 0.04867 m

H= HETP * n = 0.04867 * 5 = 0.24335 m = 24.33 cm

Height of packing (approx.) = 25 cm

Height of the column = 30 cm

The Experiment

Aim:

To verify Fenske Equation under total reflux.

Apparatus:

Batch distillation apparatus, test tubes, watch, refractometer, calibration chart

Chemicals Required:

Methanol, distilled water

Theory:

Fenske equation is given by

( Nm+1 ) logα av= logx D

1−xD

1−xw

xW

where the symbols have their usual meanings.

Fenske equation is used to calculate minimum number of theoretical stages when the relative volatility is relatively constant (MTO - Treybal, pg. 384)

Procedure:

1. Calibration chart of methanol water is prepared by filling the observation table.2. Ensure that all the valves are closed.3. Charge a fixed amount of feed (F) of desired composition XF into the boiler.4. Fill the condenser with tap water.5. Now set the heater such that the temperature of the feed reaches 80-85°C.

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6. After some time, when the reflux drum has filled sufficiently, open the reflux valve completely and ensure that distillate valve is closed so that the equipment operates in total reflux condition.

7. Keep checking the composition of the distillate and the bottom with the use of a refractometer and the calibration chart.

8. After almost 30-40 minutes, note down the final values of xD and xW.

9. Shut of all the valves and switch off power supply after finishing the experiment.

Observations:

Observation table for calibration chart

S.No

Volume of Methanol (ml)

Volume of water (ml)

Mass of Methanol (0.79*V) (g)

Mass of Water (1*V) (g)

Moles of Methanol (mol)

Moles of water (mol)

Mole fraction of Methanol (XMeOH)

Refractive Index

1 10 0 7.9 0 0.247 0 1 1.33482 9 1 7.11 1 0.222 0.056 0.799 1.33783 8 2 6.32 2 0.198 0.111 0.641 1.33984 7 3 5.53 3 0.173 0.167 0.509 1.34145 6 4 4.74 4 0.148 0.222 0.400 1.34176 5 5 3.95 5 0.123 0.278 0.307 1.34137 4 6 3.16 6 0.099 0.333 0.229 1.33988 3 7 2.37 7 0.074 0.389 0.160 1.33829 2 8 1.58 8 0.049 0.444 0.099 1.335710 1 9 0.79 9 0.025 0.500 0.048 1.333511 0 10 0 10 0 0.556 0 1.3318

xF=0.36 (500ml water + 632 ml methanol i.e. 50% by mass feed)

ρ of methanol = 0.79 g/ml

αav = 4.26 (From Seader & Henley)

S. No. Refractive Index (top)

Refractive Index (Bottom)

XD XW

1 1.338 1.339 0.79 0.22 1.341 1.339 0.65 0.233 1.339 1.338 0.71 0.17

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Distillation Column: Study and Design | 2015-16

Calculations:

Theoretical –

For the calculations to design the distillation column, we took XF = 0.36, XD = 0.87, XW = 0.2

Putting in the Fenske equation, we get minimum number of trays = 1.76 i.e 2.

Practical –

XD (average) = 0.716, XW (average) = 0.2

Form Fenske equation, minimum no. of trays = 1.59 i.e 2.

Graphs:

0 0.2 0.4 0.6 0.8 1 1.21.326

1.328

1.33

1.332

1.334

1.336

1.338

1.34

1.342

1.344

Calibration Chart

Mole fraction (Methanol)

Refr

activ

e In

dex

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Distillation Column: Study and Design | 2015-16

CHAPTER - 4

RESULTS AND DISCUSSIONSThe compositions of feed, distillate and bottom were selected on the basis of practical degree of separation. Application of the McCabe-Thiele method on the selected compositions of feed, distillate and bottom, and existing parameters has led to requirement of 8 ideal stages whereas the apparatus in the mass transfer lab has 7 stages. The operating time taken by the setup is approximately 6 hours which is not ideal for performing experiments. The existing setup has been observed and studied carefully for better understanding of the topic.

The time required for processing the request is quite long so in the meantime we are designing a packed bed batch distillation column which will replace the existing column in mass transfer lab. The calculations are shown above. The results obtained for 1 kg feed are as follows:

HETP = 0.050 m

Number of theoretical trays from McCabe Thiele method (n) = 5

Height of packing = 25 cm

Approximate height of the column = 30 cm

Diameter of the tower = 5 cm

The minimum number of stages obtained from Fenske equation for practical and experimental calculations are 2 under total reflux. This implies that our equipment is working fine.

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Distillation Column: Study and Design | 2015-16

CHAPTER - 5

CONCLUSIONSAs per the observations the current setup can be made as an 8 tray column by replacing the vertical thermosiphon reboiler by a kettle type reboiler, which would further act as an ideal tray. This in turn would increase the degree of separation and reduce the operating time. Further calculations taking into account the diameter, height and other parameters of the distillation column which will give us more insight to the column internals and hence the problem are being done.

The minimum number of stages obtained from Fenske equation for practical and experimental calculations are 2 under total reflux. This implies that our equipment is working fine.

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Distillation Column: Study and Design | 2015-16

REFERENCES1. Bhatt, B.I., & Thakore, S.B. (2009). Introduction to Process Engineering and Design

(Second reprint., pp. 475-492). McGraw-Hill, Inc.2. Henley, E., & Seader, J. (2001). Distillation of Binary Mixtures. In Separation Process

Principles (Second ed., pp. 252-285). New Delhi: Wiley India Pvt.3. Kayode Coker, A. (2010). Distillation. In Ludwig's Applied Process Design for Chemical

and Petrochemical Plants (Fourth ed., Vol. 2, pp. 1-263). Elseveir.4. Perry, R. (Ed.). (1969). Perry's Chemical Engineers' Handbook (Seventh ed). McGraw-

Hill, Inc.5. Treybal, R. (1981). Mass Transfer Operations (Third ed., pp. 342-460). McGraw-Hill,

Inc.6. Mujtaba, I (2004). Batch Distillation – Design and Operation (Vol. 3). Imperial College

Press, London.

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