Distillation Result Report

ChE 381 Process Laboratory Proect Result Report: Distillation

Short Summary of the experiment

This report is mainly about the study of the effect of reflux ratio changes on the distillation

column’s overhead and bottom compositions and the investigation of the influence of

different reflux ratio on condenser and reboiler heat duties.

From the experiment result, it is seen that reflux ratio plays a crucial role in distillation and

this is why it is deduced that any slight change in reflux ratio brings about a trend either in

terms of increasse or decrease of distillate and bottom compostion and flow rate, as well as

increase or decrease in condenser or reboiler heat duty.

This report covers 3 main areas which are the effects of reflux ratio on distillate and bottom

flowrate, the effects of reflux ratio of distillate and bottom composition and the effect of

reflux ratio on condenser and reboiler heat duty.


1.0 Objectives

To study the effect of different reflux ratio on the distillation column overhead and

bottom compositions.

To investigate the influence of different reflux ratio on the condenser and reboiler

Duties.

2.0 Apparatus Description

The main equipment used for this experiment is the distillation column, reboiler and

condenser inclusive of some other minor equipments which are listed in the table below.

Table 1: List of minor equipments used for distillation experiment

Stainless steel structure RTDs double Pt 100

Re-boiler Electronic temperature indicators

Quartz pre-heating resistance Timers

Distillation column 15A thyristor unit

Solenoid valve Electronic differential pressure transmitter

Reflux head Electronic level indicator

Overhead condenser Electronic differential pressure indicator

Double tube heat exchanger Electronic absolute pressure transmitter

Reflux solenoid valve Electronic flow meter

Feeding tank Pneumatic control valve

Level measure for distillate product tank Digital controllers

Bottom product tank Electrical switchboard

Graduated tank Supervision software mod.

Metering feeding pump Inert separator

Liquid ring vacum pump Pneumatic control valve for residual pressure

Pneumatic control valve for overhead

condenser cooling water,


2.1 Description of Controller Digitric 500

The plant used for this experiment is equipped with 2 controllers Digitric 500, multiloops PID

type with each of the controllers been complete of RS-485 cards for the connection with P.C.

through the use of a RS-485 / 232 converter. The main configuration of the controllers is

describe below.

2.2 Controller No. 1

1st loop: Control of pre-heating temperature control with acronym TIC1, range 0 - 150 0C,

output controlling J1 and indication of temperatures TI2 and TI3; TI4, TI5 and TI6, range 0 -

150 0C. This loop is performed through the controll of Quartz pre-heating resistance.

2nd loop: Control of flow rate of overhead cooling water using acronym FIC1 which falls

between the range 0-250L/h. This is achieved by controlling the pneumatice control valve.

3rd loop: Control of residual residual with acronym PLC1, range 0-100% proportional to 0-

1000 mbar; This loop is controlled through the use of controlling valve FV2.

4th loop: Control of valve in the metallic label on the pump. This is achieved by controlling

output controlling pump Gl, range 0-100% proportional to 12.64 L/h

2.3 Description of Controller No. 2

1st loop: The indication of temperatures TI7, TI8, TI9, TI10, TI11, TI12, range 0-150 0C

and of level LI1, range 0 - 100%

22nd loop: The output controlling resistance J2, range from 0-100 % proportional to 0 -

2500W and indications of differential pressure, with range 0-100% proportional to 0-1000

mmH2O.

2.4 Display Indications

1st line: This is the text line where the indications of menu and submenus appear

2nd line: This deals with the process variable

3rd line: This is the display of set-point (SP) value, error; out, %, bar. that can be selected with

the key are shown here

4th line: This helps indicate the current loop

2.5 Description of Frontal Panel

The Key Loop enables to select the desired loop


The Key Ind: This enables the variation of the parameter appearing in the third line of

the display, or to set the parameters as it will be explained in the next page.

The Key Esc/Menu: This enables to enter the menu or to exit from the menu and

submenus without storing the variations carried out.

The Key Enter: This helpsto enter the menu and submenus and to confirm the

variations carried out/

The Key M/A/C: This is to switch from the automatic mode to the manual mode

Keys ▼▲: This is to increase or to reduce the set-point value, the value of the

parameter selected in the programming or to run the menu and submenus.

Key SP-: This display the set-point value in the third line

3.0 Experimental Methods

3.1 Setting the Parameters

The parameters for this experiment are set in the submenu Parameter which is been entered

according to the following procedure:

1. In order to enter the main menu, press the key Esc/Menu which positions on the

submenu Parameter running the list of submenus with the keys ▼▲. Ths submenu is

then entered by pressing thekey Enter

2. The▼▲ botton is is to choose the parameter to be modified from the list, followed

pressing the Enter key

3. The parameter is modified by pressing the key Enter and then the keys ▼▲;

Which is followed by pressing the Ind key to shift to the digits of the number to be modified;

then pressing the key Ind for 3 s shifts the decimal point.

4. The Esc/Menu is pressed to exit without confirmation

5. The Enter key is pressed to confirm the variation

3.2 Setting the Continuous Distillation Plant Ready to Start In Manual Mode at Patm

1. Firstly, the following valves V2, V3, V5, V8, V9, V14, V15, Vl0, V1l, V13, V12,

V17,V18,V20, V21, V22, V23, V24, V25, V26, V28, V29 are all shut off.

2. In order to start the experiment, a feed mixture of 30 mol% of Ethanol in water is prepared.

3. Next, the following valves V1, V4, V6, V7, V16, V27 and V19 are turned on.

4. Tank Dl and boiler of column Cl are filled with water-ethanol binary mixture of 0.3 mol%

ethanol until the electrical resistor J2 is completely plunged.


5. All switches ware be set to 0.

6. The plant is connected to the electrical mains while the reducer unit set under the electrical

board is then connected to the 6-bar compressed air unit and the two reducers are adjusted

with respect to the pressure reported under the label (the reducer on the left is adjusted to 6

bar and the one on the right to 1.5 bar).

7. The water output (as shown in the annexed diagram) is connected to a waste pipe and the

switch will turned from AUTO-PC to AUT.

8. Next, AUTO-DIFF switch is connected and run switch is turned off.

9. The “Start” button is pushed and 2nd loop FICI (controller no.1) is be selected.

10. Control 2nd loop FIC1 (controller no.1) is set to manual mode with push button M/A/C

(red led on).

11. Control valve FVl is opened and flow rate is set at 200 L/h for example (select the

indication out with push button Ind and increase or decrease it with push button ▼▲).

12. The Set point is adjusted (push the button SP-w to increase or decrease its value with

pushbutton ▼▲ at 80% for example).

13. The 2nd loop FIC1 is set to automatic mode with push button M/A/C (green led on).

14. Values of flow rate is increased or decreased by adjusting the set-point (select the

indication SP1 with push button Ind and increase or decrease its value withpush button

▼▲).

3.3 Start up

1. Firstly, the switch of the resistor J2 is set to 1.

2. Electrical resistor is powered by using the output 4-20 mA of the 2nd loop of the controller

no. 2, proportional to 0-2500 W (select the 2nd loop with push button Loop and then the

indication Out with pushbutton Ind finally increase or decrease its value with pushbutton

▼▲).

3. Next, the mixture will is set to the boiling point.

4. The column reflux is then left to total reflux for about 5 minutes (until the temperature T16

is not stabilized).

5. The switch of the pump G1 is turned to position 1.

6. Feed, e.g. 2 L/h (20%), across the output of the 4th loop of the controller no.1 (4th (G1)

loop is selected with push button Loop and then the indication Out with push button Ind,

finally its valueis increased or decreased with push button▼▲).


7. Wait for a while until the container of the pre-heating resistor J1 is filled and select the 1st

loop (TIC1) of controller no.1.

8. The Set point is adjusted (push the button SP-w increase or decrease its value with push

button ▼▲) at 550C.

9. The control loop TIC1 is then set to automatic mode with push button M/A/C (green led

on).

10. In order to select the reflux ratio, the timer “START” is set at 2 seconds and the timer

“STOP” at 10 seconds for example.

11. The “Reflux” is switch to 1.

12. To change the reflux ratio, different times on the timers is selected.

13. The temperatures, along the column, give the composition in different positions of the

column. The flowrate of the top and bottom products will be recorded.

3.4 Shutdown Procedure

1. The switch of the pre-heating resistor J1 is to 0.

2. The pump Gl is turned off.

3. Next, the column is exhausted.

4. The switch of the heating resistor J2 is to 0

5. Then, the “Reflux” switch is set to 0.

6. After about 3-5 minutes, water inlet to the top condenser is closed (take the output of the

control loop FIC1 to 0)

7. Container of the distillate D4, tank D2, tank of the high boiling D3 is exhausted.

8. Finally, the water to the top condenser is closed.


4.0 Experimental Results

After thoroughly performig the eperiment, the following results as presented in the tables as

well as the appendix as shown below

Table 1: Result Summary for Appendix A

Reflux Ratio, R 2 4 6

Molar Flow Rate (mol/s)

Feed, F

Distillate, D

Bottom, B

0.0673

0.0063

0.0610

0.0673

0.0036

0.0637

0.0673

0.0021

0.0652

Composition of Ethanol in

Feed, zethanol

Distillate, yethanol

Bottom, xethanol

0.300

0.739

0.225

0.300

0.660

0.280

0.300

0.634

0.289

MW (g/mol)

Feed, MWF

Distillate, MWD

Bottom, MWB

26.423

38.73

25.16

26.423

36.51

25.86

26.423

35.78

26.11

Weight Fraction of Ethanol in

Feed, wF,ethanol

Distillate, wD,ethanol

Bottom, wB,ethanol

0.523

0.879

0.467

0.523

0.832

0.498

0.523

0.816

0.510

Avg Density (kg/m3)

Feed, ρavg,F

Distillate, ρavg,D

Bottom, ρavg,B

889.647

814.531

901.463

889.647

824.448

894.922

889.647

827.824

892.390


Table 4.2: Result Summary for Appendix B


Latent Heat of Vaporization of Distillate,

λD (J/mol) 39172 39345 39402

Enthalpy (J/mol)

Feed, F

Distillate, D

Bottom, B

293.76

44870.1

317.33

293.76

45008.5

282.678

293.76

45068.02

294.88

Duty (kJ/s)

Condenser, QC

Reboiler, QR

0.74035

1.0226

0.70821

0.8685

0.57921

0.6733

5.0 Discussions

In this experiment, different reflux ratiois used and this is the ratio between the boil up rate

and the take-off rate or put in other form, it is the ratio between the amount of reflux that

goes back down the distillation column and the amount of reflux that is collected in the

receiver.

Reflux ratio which is one of the important design parameters has a crucial role to play in the

distillation process as such its effects on distillate and bottom flowrate and composition as

well as its effect on condenser and reboiler heat duty is actually important in order to describe

exactly how the various stages of the distillation process is carried out using different reflux

ratio.

During this experiment, three different reflux ratios were used and they are 2, 4 and 6

including at total reflux condition. Hence, it is neccesary to discuss the effect of this varying

reflux on the flowrate, composition and heat duties of condenser and reboiler. In doing so,

theoritical knowledge will be applied to explain each and every of the above as it is affected

by the changing reflux.


5.1 Effects of reflu on distillation and bottom flow rate

Figure 1: Graph of distillate and bottom molar flow rate versus reflux ratio

In general, reflux ratio is one of the important parameters that are to be taken into

consideration when operating a distillation column. This is because a slight change in this

value will directly affect the amount of the top and bottom product and hence its purity.

As observed from figure 5.1 above, it can be clearly seen that an increase in the magnitude of

the reflux ratio will result in a decrease in the molar flow rate of the top product and an

increase in the molar flow rate of the bottom. In other words, this also indirectly indicates that

more condensed liquid will be directed back into the column whereby it will be once again

come into intimate contact with the up flowing vapor. Subsequently, mass transfer will occur

and a purer top product can be obtained. The relation between the purity of the top product

and the distillate flow rate is derived from the steady state overall mass balance and will be

shown below as:


Where

x = mole fraction of the light key in bottom product, D = distillate molar flow rate

y = mole fraction of the light key in the top product, F = feed molar flow rate

5.2 Effect of reflux ratio on distillate and bottom composition

Figure 5.2: Graph of reflu ratio on distillate and bottom composition

Total reflux which is a situation whereby there is no distillate collected from the distillation

process as all the condensed vapour goes back into column. The vapour and the condensed

vapour contact when the condensed vapour goes back into column. Thus, the higher the reflux

ratio, the higher the purity of the distillate. However, when most of the distillate goes back

into column, the production rate of distillate decreases although there is a corresponding

increase in the purity of distillate. However as this happens, the amount of bottom product

formed increases thus obeying the mass balance law of mass flow in equal to mass flow out.

Theoretically, higher reflux ratio gives a higher purity, but in this experiment, the results

oppose the theory. From our figure 5.2 above, it is observed that when increasing the reflux

ratio, the composition of more volatile component which is ethanol in distillate decreases.

Same goes to the bottom, such that as reflux ratio increases there is a decrease to the

composition of ethanol, but the result goes the other way.

This situation may be due to the occureflooding occurred during the experiment. The mixture

of water and ethanol went up to the top due to the pressure in the column and flows into the


condenser. Therefore, some controller can be installed to control the reboiler duty. When the

pressure reach a certain level the duty of the reboiler can be lower or turn off the reboiler until

the pressure reach the level where flooding will not occur.

5.3 Effects of reflux ratio on the condenser and reboiler heat duties

Figure 5.3: Graph of Reboiler and Condenser Duties versus Reflux Ratio

From the figure above, it can be seen that as the reflux ratio increases, the heat duties for the

condenser and reboiler decreases, meaning the issue of constraint control will be discussed in

the next section since theoritically increasing the reflux ratio should lead to an increase in

condenser and reboiler duties. This is because, as the reflux ratio increases, higher amount of

liquid is fed back to the distillation column, meaning a higher workload for the reboiler to

vaporize the increased liquid. As more vapor flows to the top, thus increasing condenser heat

duty.

For the selection of reflux ratios; there are several trade-offs, one of which are; the purity of

the product will increase since the flow rate of the bottom product increases, whilst the flow

rate of top product decreases when reflux ratio increases. Also, increasing reflux ratio will

increase energy cost due to increased heat transfer areas in the heat exchangers. At the same

time, energy cost decreases because of the reduced number of stages/trays to achieve the same

separation effect. (Gundersen 2007)


5.4 Constraint Control for the reboiler and condenser

There are several column constraints. For the reboiler duty some of the commonones

are: (Riggs 2008)

Fouled or plugged heat-exchanger tubes in the reboiler reduces the heat transfer-rate.

The control valve on the steam to the reboiler that isn’t the proper size affects the

steam flow to the reboiler.

If the column pressure increases, it will reduce the heat transfer rate.

As for the condenser duty:

Increase in ambient temperature, decreases the temperature difference for heat

transfer.

Fouled or plugged tubes in the condenser reduces its heat duty.

Coolant temperature increases.

An increase in column feed rate

6.0 Conclusion

From this experiment, it is agreed that changes in reflux ratio either in the positive or negative

direction have tremedous effect on the distillate, bottom product flowrate as well as their

composition and condenser and reboiler heat duties.

More so, it is observed that the composition of the distillate and bottom product did increase

as compared to ethanol composition which did increase in the bottom production as reflux

ratio increases. This is against the theoritical observation and believe on effects of changing

reflux ratio as such it is believed that this irregularity is as a result of either the process

temperature or any other factor as error in taking readings on apporiate expperimental

parameters which could possibly have influenced this experiment. Hence, it would be

important if same experimental process are performed more than once so that average values

could be taken.

More so, it is seen that the flow rate of the product agreed with theoritcially lead down rules

on effect of reflux ratio. This is proven in the the flow rate of the distillate did decrease while

the flow rate of the bottom production did increase as reflux ratio was increase.


Furthermore, it was found that as reflu ratio increases the heat duties for both the condenser

and reboiler did decrease.

Summarily, the learning outcome and objectives of this experiment has been achieved

although the were many sources of errors which posed challenges towards getting the exact

theoritical lead down rules for certain parameters determined in this experiment.


Reference

Ackland, T. 2011. Basic Data for Ethanol-Water Binary Mix.

http://homedistiller.org/calc.htm (accessed 21st Sept 2011)

Agus, S. 2010 Distillation ChE 381 Process Lab Project Laboratory Manual

Basic Theory Distillation,

http://chemeng-processing.blogspot.com/2009/02/basic-theory-distillation.html (Accessed

5th September, 2011)

Dutta, B. K. 2007. Principles of Mass Transfer and Separation Processess. Distillation. New

Delhi: Prentice-Hall.

Dutta, B. K. 2009. Distillation. In Principles of Mass Transfer and Separation Processes,

India: Prentice Hall.

Geankoplis, C.J. 2003. Transport Process and Separation Process Principless (Includes Unit

Operation). 4th ed. New Jersey: Prentice Hall.

Liquids and Fluids- Specific Heats. 2011. The Engineering Toolbox.

http://www.engineeringtoolbox.com/specific-heat-fluids-d_151.html

McCabe, W. L., J. C. Smith and P. Harriott. Unit Operations of Chemical Engineering,

7th Ed. New York: McGraw-Hill, 2005.

Perry, R.H., and D. Green, Perry’s Chemical Engineering Handbook, 6th edition,

McGraw-Hill, 1984.

Reflux Ratio. 2011. B/R Corporation.

http://www.solvent--recycling.com/reflux%20ratio.html

The Engineering ToolBox. n.d. Water-Thermal properties

http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html

(accessed 21st Sept 2011)

http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html%0D%20%20%20%20%20%20%20%20%20%20%20%20(accessed

http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html%0D%20%20%20%20%20%20%20%20%20%20%20%20(accessed

http://www.solvent--recycling.com/reflux%20ratio.html

http://chemeng-processing.blogspot.com/2009/02/basic-theory-distillation.html(Accessed

http://chemeng-processing.blogspot.com/2009/02/basic-theory-distillation.html

http://homedistiller.org/calc.htm


8.0 Appendix

Appendix A

A.1: Data Collection

Table A.1.1 Experimental Value

Parameters Experimental Value

Reflux Ratio, R Total Reflux 2 4 6

Flow Rate of Feed, F (ml/s) 2 2 2 2

Composition of Ethanol in Feed, zethanol 0.30 0.30 0.30 0.30

Flow Rate of Distillate, D (ml/s) 0.00 0.30 0.16 0.09

Feed Temperature, TF /TI7 (oC) 28.4 28.4 28.4 28.4

Top Product Temperature, TD /TI6 (oC) 78.2 78.7 79.7 80.3

Bottom Product Temperature, TB / TI11 (oC) 28.8 28.9 28.8 28.8

The table A.1.1 above shows the data obtained from experiment:

Table A.1.2 Temperature distribution for different reflux ratios

Reflux Ratio, R Total 2 4 6


Temperature oC

TI1 28.6 28.4 34.3 36.1

TI2 93.0 92.8 92.8 92.5

TI3 89.1 89.3 89.1 89.1

TI4 79.1 79.1 79.1 79.1

TI5 76.9 77.3 77.5 77.3

TI6 78.2 78.7 79.7 80.3

TI7 28.4 28.4 28.4 28.4

TI11 28.8 28.9 28.8 28.8

The table A.1.2 above shows the reading of temperature at different location at different

reflux ratio:

Table A.1.3 Property data for ethanol and water (Ackland, 2011) (Engineering Toolbox n.d)

Properties Ethanol Water

Density, ρ (kg/m3) 789 1000

Molecular Weight, MW (g/mol) 46.0414 18.0152

Boiling Point, Tbp (°C) 78 100

Heat of Vapourisation, λv (kJ/mol) 38.60 40.79

Specific Heat of Vapor, Cv (J/mol.K) 65.6 37.4

Specific Heat of Liquid, Cl ((J/mol.K) 112.3 75.3

Table A.1.4 Ethanol-Water Vapour-Liquid Equilibrium data (Ackland, 2011)

Temperature Mole Fraction


oC Liquid, x Vapour, y

95.5 0.019 0.170

89.0 0.072 0.389

86.7 0.097 0.438

85.3 0.124 0.470

84.1 0.166 0.509

82.7 0.234 0.545

82.3 0.261 0.558

81.5 0.327 0.583

80.7 0.397 0.612

79.8 0.508 0.656

79.7 0.520 0.660

79.3 0.573 0.684

78.74 0.676 0.739

78.24 0.747 0.782

78.15 0.894 0.894

The table A.1.4above shows the vapor-liquid equilibrium data for ethanol-water that obtained from source:

A.2 Compositions for Top and Bottom Products.


Compositions of Top Product (Distillate):

The composition ethanol and water in top product for different reflux ratio are obtained from Table

A.1.4 by using their respective temperature.

Reflux Ratio, R Top Product Temperature, TD (°C) Sat. Vapour

2 78.7 0.739 0.261

4 79.7 0.660 0.340

6 80.3 0.634 0.366

Table A.2.1: Top product (distillate) Composition.

MW of Feed and Distillate:

When Reflux ratio=2;

The above calculations for feed and distillate molecular weight are repeated by using R=4 and

6.

Table A.2.2 MW of distillate at different values of reflux ratio


Reflux Ratio, R Molecular Weight of Distillate, MWD (g/mol)

2 38.73

4 36.51

6 35.78

Weight Fraction of Ethanol and Water in Feed and Distillate:


When reflux ratio=2,

The above calculations for weight fraction are repeated for reflux ratio of 4 and 6 and the

results are in Table A.2.3 below:

Table A.2.3: Ethanol and water weight fraction in distillate at different reflux ratio

Reflux Ratio,

R


Distillate,

Weight Fraction of Water in

Distillate,

2 0.879 0.121

4 0.832 0.168

6 0.816 0.184

Average Density of Feed and Distillate, :

When reflux ratio, R=2,


The average density calculations will be repeated with reflux ratio of 4 and 6. The results are

tabulated in Table A.2.4.

Table A.2.4: Distillate average density for different reflux ratio

Reflux Ratio, RAvg Density of Distillate, (

2 814.531

4 824.448

6 827.824

Molar Flow rate for Feed and Distillate:


The above calculation for molar flow rate is repeated by using reflux ratio of 4 and 6. The

results are as in Table A.2.5.

Table A.2.5: Molar flow rate of distillate for different reflux ratio.

Reflux Ratio, R Molar

2 0.0063

4 0.0036


6 0.0021

Molar Flow Rate, Compositions and Other Properties for Bottom Product:

The bottom product properties will be obtained by using the answers from previous

calculations.

When reflux ratio= 2,

The above calculation for molar flow rate is repeated for reflux ration of 4 and 6. The results

are tabulated in Table A.2.6 below.

Table A.2.6 Molar flow rate of bottom for different reflux ratio

Reflux Ratio, R

2 0.0610

4 0.0637

6 0.0652

Ethanol composition in bottom product,


The above steps for composition of ethanol in bottom product are repeated by using reflux

ratio of 4 and 6. The results from the calculations are tabulated in Table A.2.7 below:

Table A.2.7 Compositions of ethanol and water in bottom for different reflux ratio

Reflux Ratio, R Composition of Ethanol in Bottom, Composition of Water in Bottom,

2 0.255 0.745

4 0.280 0.720

6 0.289 0.711

MW for bottom product:


The above calculation for molecular weight for bottom product is repeated by using reflux

ratio of 4 and 6. The results obtained are tabulated in Table A.2.8 below:

Table A.2.8 MW for bottom product for different reflux ratio

Reflux Ratio, R Molecular Weight of Bottom, MWBottom (g/mol)

2 25.16

4 25.86

6 26.11


Reflux ratio=2,

The above steps for weight fraction calculation are repeated by using reflux ratio of 4 and 6.

The results obtained are tabulated in Table A.2.9 below:

Table A.2.9 Weight fraction of ethanol and water in bottom product for different reflux ratio

Reflux Ratio,

R


Bottom,

Weight Fraction of Water in

Bottom,

2 0.467 0.533

4 0.498 0.502


6 0.510 0.490

Average density in bottom product, :


The above calculation for average density in bottom product is repeated by using reflux ratio

of 4 and 6. The results are tabulated in Table A.2.10 below:

Table A.2.10 Average density of bottom product for different reflux ratio

Reflux Ratio, RAverage Density of Bottom, (

2 901.463

4 894.922

6 892.390

The Table A.2.11 below shows the summary results obtained in Part A2 calculations.


Molar Flow Rate (mol/s)

Feed, F 0.0673 0.0673 0.0673


Distillate, D

Bottom, B

0.0063

0.0610

0.0036

0.0637

0.0021

0.0652

Composition of Ethanol in

Feed, zethanol

Distillate, yethanol

Bottom, xethanol

0.300

0.739

0.225

0.300

0.660

0.280

0.300

0.634

0.289

MW (g/mol)

Feed, MWF

Distillate, MWD

Bottom, MWB

26.423

38.73

25.16

26.423

36.51

25.86

26.423

35.78

26.11


Feed, wF,ethanol

Distillate, wD,ethanol

Bottom, wB,ethanol

0.523

0.879

0.467

0.523

0.832

0.498

0.523

0.816

0.510

Avg Density (kg/m3)

Feed, ρavg,F

Distillate, ρavg,D

Bottom, ρavg,B

889.647

814.531

901.463

889.647

824.448

894.922

889.647

827.824

892.390

Table A.2.11 Result Summary Part A.2


A.3 Condenser and Reboiler Duty

Latent Heat of Vaporisation of Distillate

To find the latent heat of vaporisation of the distillate, the following equation will be used:

For reflux ratio of 2,

The above calculation is repeated by using reflux ratio of 4 and 6. The results obtained will be

tabulated in Table A.3.1 below:

Table A.3.1 Latent heat of vaporisation for different reflux ratio

Reflux Ratio, R Latent Heat of Vaporisation, (J/mol)

2 39172

4 39345

6 39402

Too find the duty of Condenser, the below equation will be used:


The above calculation for condenser duty will be repeated for reflux ratio of 4 and 6. The

results are tabulated in Table A.3.2 below:


Table A.3.2 Condenser duty for different reflux ratio

Reflux Ratio, R Condenser Duty, QC (kJ/s)

2 0.74035

4 0.70821

6 0.579.21

The Molar Enthalpy of Feed, Distillate and Bottom:

Before calculating for molar enthalpy, a reference temperature, Tref will be chose. So, the Tref

that going to used is 25°C. Then, the molar enthalpy of feed, distillate and bottom will be

calculated my using the below equation:



The above calculation for enthalpy will be repeated by using reflux ratio of 4 and 6. The result

obtained is tabulated in Table A.3.3.

Table A.3.3 Molar enthalpy of distillate and bottom for different reflux ratio

Reflux Ratio,

R

Molar Enthalpy of Distillate, HD

(J/mol)

Molar Enthalpy of Bottom, HB

(J/mol)

2 44870.1 317.33

4 45008.5 282.678

6 45068.02 294.88

Reboiler Heat Duty:

The reboiler heat duty is calculated by using the below formula:


The above calculation for reboiler heat duty is repeated by using reflux ratio of 4 and 6. The

result obtained is tabulated in Table A.3.4 below:


Table A.3.4 Reboiler duty for different reflux ratio

Reflux Ratio, R Reboiler Duty, QR (kJ/s)

2 1.0226

4 0.8685

6 0.6733

Result Summary for Part A.3:

The table below shows the results obtained from calculation in A.3 to determine the condenser and reboiler heat duty.

Table A.3.5: Result Summary for A.3


Latent Heat of Vaporization of Distillate, λD

(J/mol)39172 39345 39402

Enthalpy (J/mol)

Feed, F

Distillate, D

Bottom, B

293.76

44870.1

317.33

293.76

45008.5

282.678

293.76

45068.02

294.88

Duty (kJ/s)

Condenser, QC

Reboiler, QR

0.74035

1.0226

0.70821

0.8685

0.57921

0.6733

Documents

Distillation Result Report