Separation of Acetone Water with Aspen HYSYS® V8 · Separation of Acetone-Water with Aspen HYSYS...

Dist-009H Revised: Nov 19, 2012

1

Separation of Acetone-Water with Aspen HYSYS® V8.0

Liquid-Liquid Extraction with 3-Methylhexane as the Solvent

1. Lesson Objectives Learn how to build an extraction and solvent recovery flowsheet.

Learn how to configure a liquid-liquid extractor and a distillation column.

2. Prerequisites Aspen HYSYS V8.0

3. Background Water has a high latent heat (heat of vaporization) compared to many other components. For the separation of

a water-acetone mixture (50 wt-% each), it may be more energy efficient to use extraction instead of direct

distillation. In this example, we utilize 3-methylhexane as a solvent to remove water via liquid-liquid extraction,

followed by distillation to remove the solvent from acetone.

The examples presented are solely intended to illustrate specific concepts and principles. They may not

reflect an industrial application or real situation.

4. Problem Statement and Aspen HYSYS Solution

Problem Statement

Determine how much energy is required to separate a 50 wt-% acetone 50 wt-% water stream using 3-

methylhexane as a solvent.

Aspen HYSYS Solution

4.01. Start a new simulation in Aspen HYSYS V8.0.

4.02. Create a component list. In the Component Lists folder select Add. Add Acetone, Water, and 3-

methylhexane to the component list.


2

4.03. Select property package. In the Fluid Packages folder select Add. Select PRSV as the property package.

For information about the PRSV property package see Aspen HYSYS help.

4.04. Move to the simulation environment by clicking the Simulation button in the bottom left of the screen.

4.05. First we will add a Mixer to the flowsheet from the Model Palette. This mixer will serve to mix together

the recycled solvent stream and the solvent make up stream.


3

4.06. Double click the mixer (MIX-100). Create two Inlet streams called Make Up and Solvent-Recycle.

Create an Outlet stream called Solvent.


4

4.07. Double click on the Make Up stream. Specify a Temperature of 25°C, a Pressure of 1 bar, and a Molar

Flow of 0. We will later assign this stream a flowrate, but for now it will have zero flow. In the

Composition form enter a Mole Fraction of 1 for 3-methylhexane.

4.08. Double click on the Solvent-Recycle stream. Enter a Temperature of 30°C, a Pressure of 1 bar, and a

Mass Flow of 150 kg/h. In the Composition form enter a Mole Fraction of 1 for 3-methylhexane. These

specifications will serve as an initial guess as to what the actual recycle stream will be.


5

4.09. Add a Liquid-Liquid Extractor to the flowsheet from the Model Palette.

4.10. Double click on the extractor (T-100) to open the Liquid-Liquid Extractor Input Expert window. On the

first page enter a Top Stage Inlet called Feed and select Solvent for the Bottom Stage Inlet. Change the

number of stages to 8. Enter an Ovhd Light Liquid stream called Rich-Sol and a Bottoms Heavy Liquid

stream called Water. Click Next when complete.


6

4.11. On Page 2 of the Input Expert enter Top and Bottom Stage Pressures of 1 bar. Click Next when

complete.

4.12. On the final page of the Input Expert enter a Top Stage Temperature Estimate of 25°C. Click Done

when complete to configure the column.


7

4.13. We must now define the feed stream. Go to the Worksheet tab in the Column: T-100 window. For the

Feed stream enter a Temperature of 25°C, a Pressure of 1 bar, and a Mass Flow of 100 kg/h.

4.14. In the Compositions form under the Worksheet tab enter Mass Fractions of 0.5 for acetone and water

in the Feed stream.


8

4.15. Click the Run button at the bottom of the Column: T-100 window to begin column calculations. The

column should converge.

4.16. Check the composition of the Water stream exiting the bottom of the column. You will see that the

mole fraction for water is 1.


9

4.17. We will now insert a Distillation Column Sub-Flowsheet from the Model Palette.

4.18. Double click the column (T-101) to open the Distillation Column Input Expert. On Page 1 enter the

following information and click Next when complete.


10

4.19. On Page 2 of the Input Expert leave the default selections for a Once-through, Regular Hysys Reboiler.

Click Next.

4.20. On Page 3 of the Input Expert enter Condenser and Reboiler Pressures of 1 bar. Click Next when

complete.


11

4.21. On Page 4 and 5 leave all fields blank. Click Done on the final page to configure the column.

4.22. We must define the design specifications for this column. Go to the Specs Summary form under the

Design tab. Enter 1.2 for Reflux Ratio and make sure that the reflux ratio specification is the only active

design specification.

4.23. We will now add a specification for the mole fraction of acetone in the distillate stream. Go to the Specs

form under the Design tab. Click Add and select Column Component Fraction. Select Stream for Target

Type, Acetone for Draw, enter 0.99 for Spec Value, and select Acetone for Component.

4.24. The Degrees of Freedom for the column should now be 0. Click the Run button to begin column

calculations. The column should solve.


12

4.25. We now need to add a cooler to cool the bottoms stream in order to recycle it back to the mixer. Add a

Cooler to the flowsheet from the Model Palette.


13

4.26. Double click on the cooler (E-100). Select stream Sol-Rec as the Inlet, and create an Outlet called Lean-

Sol and an Energy stream called Q-Cool.

4.27. In the Worksheet tab enter an outlet Temperature of 30°C and a Pressure of 1 bar. The block should

solve.


14

4.28. Now we will add a Spreadsheet to control to flowrate of solvent in the Make Up stream.

4.29. Double click on the spreadsheet (SPRDSHT-1). Go to the Spreadsheet tab and enter the following text in

cells A1 and A2.


15

4.30. Right click on cell B1 and select Import Variable. Select Master Comp Molar Flow of 3-methylhexane in

the acetone product stream.

4.31. Click on cell B2 and enter “=B1”. Right click on cell B2 and select Export Formula Result. Select the

Molar Flow of stream Make Up. This will set the Make Up stream flowrate equal to the flowrate of

solvent being lost in the product stream.


16

4.32. We will now recycle the bottoms streams from the second column in order to prevent throwing away

acetone product. Add a Recycle block to the flowsheet from the Model Palette.


17

4.33. Double click on the recycle block (RCY-1). Select stream Sol-Rec as the Inlet and stream Solvent-Recycle

as the Outlet. The flowsheet should solve.

4.34. We can now try to minimize the amount of solvent that we are recycling. It is possible that there are

many solutions for the amount of solvent recycle, and we wish to find the optimum solution. We can

vary the mass flow of the recycle stream and find where the reboiler duty is at the lowest.

4.35. Go to Case Studies in the navigation pane and click Add. In Case Study 1 click Add and select the Mass

Flow of stream Solvent-Recycle and the Reboiler Duty of column T-101. Enter a Low Bound of 75 kg/h,

a High Bound of 200 kg/h, and a Step Size of 5 kg/h. Click Run.


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4.36. Check results. Go to the Plots tab and you will see that the reboiler duty is the lowest when the solvent

recycle flow is around 75 kg/h. You may try setting the flowrate of Solvent-Recycle even lower, but you

will find that the flowsheet will not converge.


19

4.37. Double click on stream Solvent-Recycle and enter a Mass Flow of 75 kg/h. The flowsheet should

converge after a few moments.

4.38. Check results. Double click on column T-101 and go to the Cond./Reboiler form under the Performance

tab. Make note of the Condenser and Reboiler Duty.

4.39. Double click on energy stream Q-Cool and make note of the cooling duty.


20

4.40. The total heating duty for this design is 16,270 kcal/h and the total cooling duty is 9,218 kcal/h.

4.41. Save this the HYSYS file as Dist-009H_Extraction.hsc.

5. Conclusions Based on the simulation results, it would require 16,270 kcal/h of heating and 9,218 kcal/h of cooling to

separate the water –acetone mixture via liquid-liquid extraction. This design is proven to be feasible, however it

may or may not be the optimal design. Another option would be direct distillation of water and acetone. Direct

distillation of water and acetone would require less equipment, but it may require more energy.

6. Copyright Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be

reproduced or distributed in any form or by any means without the prior written consent of

AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH

RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be

liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential

damages arising out of the use of the information contained in, or the digital files supplied with or for use with,

this work. This work and its contents are provided for educational purposes only.

AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and

product names mentioned in this documentation are trademarks or service marks of their respective companies.

RX-008H Revised: Nov 6, 2012

1

Simple Combustion Reactor with Aspen HYSYS® V8.0

1. Lesson Objectives Use conversion reactor block

Determine air flow rate needed for a clean burn

Determine heat available from a fuel stream


Understanding of enthalpy of combustion

3. Background Natural gas, which is primarily methane, is distributed in underground pipes. The pressure in these pipes varies

depending on where in the pipe it is: the closer to the pumping station, the higher the pressure. An industrial

customer can expect to get natural gas at around 60 psig, and is typically charged per cubic foot of natural gas

used. Methane burns in the following reaction:

CH4 + 2 O2 CO2 + 2 H2O




Problem Determine how much energy is available from a 5 ft3/h (0.472 kg/h) fuel stream that consists of only methane at

60 psig. The air feed should be approximated with 80 mol-% nitrogen and 20 mol-% oxygen. There should be

10% excess oxygen in the air stream so the fuel-air mixture is not too rich. Assume the exhaust is 182 °C. Report

the air flow rate in mol/h and ft3/h (at 1 atm) in addition to the available heat in kW.

Mole Balance Two moles of oxygen are required to combust each mole of methane. Oxygen is one fifth of the moles in air.

Therefore there will need to be ten moles of air for each mole of methane for a stoichiome tric mixture. A 10%

excess requires a 10% increase in the relative amount of air, or 11 moles of air for each mole of methane.


2

Aspen HYSYS Solution 4.01. Start Aspen HYSYS V8.0. Select New to create a new simulation.

4.02. Create a component list. In the navigation pane find Component Lists and select Add to create a new

HYSYS component list. Add Oxygen, Nitrogen, Methane, Carbon Dioxide, and Water to the component

list.

4.03. Add a fluid package. Go to Fluid Packages and select Add. Select Peng-Robinson as the property

package.

4.04. Define reaction. Go to Reactions and click New to create a new reaction set. In the form for the newly

created reaction set, click Add Reaction and select Hysys, Conversion.


3

4.05. Double click Rxn-1 to open the Conversion Reaction: Rnx-1 window. Enter the following information.

Notice that the Reaction Heat is automatically calculated to be -8.0e+05 kJ/kgmole.

4.06. Attach reaction to fluid package. In the Reaction Set 1 form, click the Add to FP button. Select Basis-1.


4

4.07. At this point, you are ready to move to the simulation environment. To do so, click the Simulation

button at the bottom left of the screen.

4.08. On the main flowsheet create a material stream using the Model Palette. Select the icon for material

stream and place it onto the flowsheet.


5

4.09. Double click the stream to open the stream property window. Change the stream name to Methane,

and enter a Temperature of 25°C, a Pressure of 515 kPa, and a Mass Flow of 0.472 kg/h.

4.10. Go to the Composition form and enter a Mole Fraction of 1 for Methane. You will notice that after

entering the stream composition, the status bar will turn green and say OK. This indicates that stream is

fully defined and solved for all parameters.


6

4.11. Create a second material stream to be the air stream that is required for combustion. Double click on

the new material stream and enter the following information. Bold blue font indicates a user-entered

value. From the solved Methane stream, we know there are 0.02942 kgmole/hr of Methane. We

would like there to be 11 moles of air for each mole of methane, therefore we will enter a molar

flowrate of 0.324 kgmole/hr for the air stream. Enter a Mole Fraction of 0.2 for Oxygen and mole

fraction of 0.8 for Nitrogen. The stream should then solve.


7

4.12. The flowsheet should now look like the following.


8

4.13. We will now place a valve in order to reduce the pressure of the methane stream to ambient pressure.

Select a Control Valve from the Model Palette and place it onto the flowsheet.

4.14. Double click the valve to open the valve property window. In the Connections page select Methane as

the Inlet stream and create an Outlet called Methane-LP.


9

4.15. Specify valve outlet pressure. Go to the Worksheet tab and enter a Pressure of 101.3 kPa for the

Methane-LP stream. The valve should solve.


10

4.16. Insert reactor. Press F12 to open the UnitOps window. Select the Reactors radio button and add a

Conversion Reactor to the flowsheet.

4.17. In the Conversion Reactor property window select streams Air and Methane-LP as Inlet streams.

Create a Vapour Outlet stream called VAP-Out and a Liquid Outlet called LIQ-Out.


11

4.18. Go to the Reactions tab. Select Set-1 for Reaction Set. The reactor should solve and the status should

turn green and say OK.


12


4.20. To check results go to Worksheet tab of the Conversion Reactor. You can see that the stream VAP-Out

is leaving the reactor at an extremely high temperature. This is due to the high heat of reaction. To

calculate exactly how much energy is released from this reaction simply take the heat of reaction found

in the Reactions tab and multiply it by the methane molar flowrate. In this case, burning 5 ft3/h of

methane releases 6.5 kW.


13

5. Conclusions 5 ft3/h of methane produces 6.5 kW of heat. To run a quality, lean mixture there must be 280 ft3/h of air (that is

20 mol-% oxygen) which is 0.324 kgmole/h. The conversion reactor block is useful for quick simulations with

well understood reactions. Reactions with slow kinetics, or complex systems with series or parallel reactions are

outside the scope of this reactor model.

This simulation could also be created using a Gibbs reactor block. The Gibbs reactor is unique in that it can

function without a defined reaction set. This reactor block will minimize the Gibbs free energy of the reacting

system to calculate the product composition. This reactor block is useful when the exact reactions or kinetics

are unknown, and the reaction reaches equilibrium very quickly. It may be a useful exercise to repeat this

module using a Gibbs reactor and compare results.










Design-001H Revised: Nov 7, 2012

1

Ammonia Synthesis with Aspen HYSYS® V8.0

Part 1 Open Loop Simulation of Ammonia Synthesis

1. Lesson Objectives Become comfortable and familiar with the Aspen HYSYS graphical user interface

Explore Aspen HYSYS flowsheet handling techniques

Understand the basic input required to run an Aspen HYSYS simulation

Determination of Physical Properties method for Ammonia Synthesis

Apply acquired skill to build an open loop Ammonia Synthesis process simulation

Enter the minimum input required for an simplified Ammonia Synthesis model

Examine the open loop simulation results


3. Background Ammonia is one of the most highly produced chemicals in the world and is mostly used in fertilizers. In 1913

Fritz Haber and Carl Bosch developed a process for the manufacture of ammonia on an industrial scale (Haber-

Bosch process). This process is known for extremely high pressures which are required to maintain a reasonable

equilibrium constant. Today, this process produces 500 million tons of nitrogen fertilizer per year and is

responsible for sustaining one-third of the Earth’s population.

Ammonia is produced by reacting nitrogen from air with hydrogen. Hydrogen is usually obtained from steam

reformation of methane, and nitrogen is obtained from deoxygenated air. The chemical reaction is shown

below:

Our goal is to produce a simulation for the production of ammonia using Aspen HYSYS. We will create a very

simplified version of this process in order to learn the basics of how to create a flowsheet in the Aspen HYSYS

V8.0 user interface. A diagram for this process is shown below.


2

Knowledge Base: Physical Properties for Ammonia Process

Equation-of-state models provide an accurate description of the thermodynamic properties of the high-

temperature, high-pressure conditions encountered in ammonia plants. The Peng-Robinson equation of state

was chosen for this application.




3

4. Aspen HYSYS Solution

Build a Process Simulation for Ammonia Synthesis

4.01. Start Aspen HYSYS V8.0. Select New on the Start Page to create a new simulation.

4.02. Create a component list. In the Component Lists folder, select Add. Add the following components to

the component list.

4.03. Create a fluid package. In the Fluid Packages folder, select Add. Select the Peng-Robinson property

package.

4.04. Define reactions. Go to the Reactions folder, and click Add. This will create a new reaction set called

Set-1. In Set-1, select Add Reaction and select Hysys, Conversion. This will create a new reaction called

Rxn-1.


4

4.05. Double click on Rxn-1 to open the Rxn-1 window. Enter the following information. Close this window

when complete.

4.06. In Set-1, we must now attach the reaction set to a fluid package. Click the Add to FP button and select

Basis-1. The reaction set should now be ready.


5

4.07. Go to the simulation environment. Click on the Simulation button in the bottom left of the screen. Then

find the Flowsheet Main tab. The Flowsheet Main is the main simulation flowsheet where you will

create a simulation.

4.08. From the Model Palette, add a Compressor to the main flowsheet.


6

4.09. Double click the compressor (K-100) to open the property window. Create an Inlet stream called

SynGas, an Outlet stream called S2, and an Energy stream called Q-Comp1.


7

4.10. We must define our SynGas feed stream. In K-100, go to the Worksheet tab. For the stream SynGas,

enter a Temperature of 280°C, a Pressure of 25.5 bar_g, and a Molar Flow of 7000 kgmole/h. In the

Composition form enter the following mole fractions. Stream SynGas should now solve.

4.11. Specify the compressor outlet pressure. In the Worksheet tab of K-100, enter a Pressure of 274 bar_g

for stream S2. The compressor should now solve.


8

4.12. The flowsheet should look like the following.

4.13. Next, we will add a mixer. Add a Mixer to the flowsheet from the Model Palette.


9

4.14. Double click on the mixer (MIX-100) to open the mixer window. Select stream S2 as the Inlet and create

an Outlet stream called S3. The mixer should solve. We will eventually use this mixer to connect a

recycle stream to the process.


10

4.15. Next, add a heater to the flowsheet.

4.16. Double click on the heater (E-100) to open the heater window. Select S3 as the Inlet stream, create an

Outlet stream called S4, and create an Energy stream called Q-Heater. In the Parameters form in the

Design tab, enter a Delta P of 0. In the Worksheet tab, specify an outlet Temperature of 775 K

(481.9°C). Note that this heater is currently acting as a cooler, but once we connect the recycle stream

this block will in fact add heat and raise the temperature of the stream.


11

4.17. Next, we will add a reactor to the flowsheet. This process uses plug flow reactors to accomplish

synthesis reaction, but for this simplified simulation we will use a conversion reactor. To use a plug flow

reactor, we would need to have detailed kinetics describing the reaction. Press F12 to open the UnitOps

window. Select the Reactors radio button and select Conversion Reactor. Click Add.


12

4.18. After clicking Add, the conversion reactor window will open. Select an Inlet stream of S4 and create a

Vapour Outlet stream of S5V, a Liquid Outlet stream of S5L, and an Energy stream called Q-Reac.

4.19. In the conversion reactor window (CRV-100), go to the Reactions tab. Select Set-1 for Reaction Set. In

the Worksheet tab enter an outlet Temperature of 481.9°C for stream S5L. This value will copy over to

S5V. The reactor should then solve. Notice that the contents of the reactor are entirely vapor;

therefore the liquid outlet stream has a flowrate of zero.


13


4.21. We will now add a cooler to cool the vapor stream leaving the reactor.


14

4.22. Double click the cooler (E-101) to open the cooler window. Select stream S5V as the Inlet stream,

create an Outlet stream called S6, and create an Energy stream called Q-Cooler.


15

4.23. In the Parameters form under the Design tab, enter a Delta P of 100 bar. We want to lower the

pressure in order to allow an easier separation of ammonia. In the Worksheet tab, specify an outlet

stream Temperature of 300 K (26.85°C). The cooler should solve.


16

4.24. Add a separator block to the flowsheet.

4.25. Double click on the separator (V-100). Select an Inlet stream of S6, create a Vapour Outlet called S7,

and create a Liquid Outlet called NH3. The separator should solve.


17


4.27. Review simulation results. Double click stream NH3. In the Conditions form under the Worksheet tab

you can view the stream flowrate and conditions. In the Composition form you can view the stream

composition. Here you can see that the mole fraction of ammonia is equal to 0.9754.


18

4.28. After completing this simulation, you should save the file as a .hsc file. It is also good practice to save

periodically as you create a simulation so you do not risk losing any work. The open loop simulation is

now ready to add a recycle stream, which we will then call a closed loop simulation. See module Design-

002H for the closed loop design.

5. Copyright

Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be










1

Extractive Distillation for Heptane-Toluene Separation using Aspen HYSYS® V8.0

1. Lesson Objectives Essentials of extractive distillation

How to compare design alternatives


Introduction to distillation

3. Background When the two components in a binary mixture have very close normal boiling points, their relative volatility is

likely to be small if they do not form an azeotrope. For such cases, it may be more efficient to use extractive

distillation with a solvent than normal distillation. In extractive distillation, a less volatile solvent is used to

increase the relative volatilities of the original mixtures, allowing for easier separation. In this example, phenol

is used as the solvent for the separation of n-heptane and toluene.




Problem Statement

Determine whether conventional distillation or extractive distillation with phenol as a solvent is a more efficient

method to separate n-heptane and toluene.

Aspen HYSYS Solution

4.01. We will build models to simulate the separation of n-heptane and toluene. One model has a single

distillation column and the other uses the extractive distillation approach with two columns. First we

will build a simulation for a single distillation column. Start a new simulation using in Aspen HYSYS V8.0.

4.02. Create a component list. In the Component Lists folder select Add. Add n-Heptane and Toluene to the

component list.


2

4.03. Select property package. In the Fluid Packages folder select Add. Select NRTL as the property package

and select RK as the Vapour Model.

4.04. Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.


3

4.05. Place a Distillation Column Sub-Flowsheet on the main flowsheet from the Model Palette.

4.06. Double click on the column (T-100) to open the Distillation Column Input Expert. On Page 1 enter the

following information and click Next when complete.


4

4.07. On Page 2 of the Input Expert leave the default selections for a Once-through, Regular Hysys reboiler.

Click Next.


complete.


5

4.09. On Page 4 and 5 of the Input Expert leave all fields empty. Click Done on the final page to configure the

column.

4.10. In the Column: T-100 window go to the Worksheet tab to specify the feed stream. For the Feed stream

enter a Vapour Fraction of 0.5, a Pressure of 1 bar, and a Molar Flow of 100 kgmole/h.

4.11. In the Composition form under the Worksheet tab enter Mole Fractions of 0.5 for both components.

This stream should solve.

4.12. Now we must define the column design specifications. Go to the Specs Summary form under the

Design tab. Uncheck the Active boxes so that there are no active specifications.


6

4.13. Go to the Specs form under the Design tab. We want to add a specification for the mole purity of both

product streams. Click Add and select Column Component Fraction. Select Stream for Target Type,

Heptane for Draw, enter 0.99 for Spec Value, and select n-Heptane for Component.

4.14. Add a similar specification for the mole fraction of toluene in the bottoms product stream.


7

4.15. After entering both design specifications the Degrees of Freedom should now be 0. Click Run to begin

calculations. The column should converge.

4.16. Go to the Cond./Reboiler form under the Performance tab. Make a note of both the Condenser and

Reboiler duties. The Condenser Duty is 5.390e+006 kcal/h and the Reboiler Duty is 5.388e+006 kcal/h.


8

4.17. Save this file as Dist-012H-Single_Column.hsc.

4.18. We will now create a second simulation, this time using extractive distillation. Create a new file in

Aspen HYSYS V8.0.

4.19. Create a component list. In the Component Lists folder select Add. Add n-Heptane, Toluene, and

Phenol to the component list.

4.20. Select property package. In the Fluid Packages folder select Add. Select NRTL as the property package

and select RK as the Vapour Model.


9

4.21. Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.

4.22. Add a Distillation Column Sub-Flowsheet to the main flowsheet from the Model Palette.


10

4.23. Double click on the column (T-100) to open the Distillation Column Input Expert. Enter the following

information on Page 1 and click Next when complete.


11

4.24. On Page 2 of the Input Expert leave the default selections for a Once-through, Regular Hysys reboiler.

Click Next when complete.


complete.

4.26. On Page 4 and 5 leave all fields empty. Click Done on the final page to configure the column.

4.27. First we must define the feed streams. In the Column: T-100 window go to the Worksheet tab. For the

Feed stream enter a Vapour Fraction of 0.5, a Pressure of 1 bar, and a Molar Flow of 100 kgmole/h.

For the Solvent stream enter a Temperature of 181°C, a Pressure of 1 bar, and a Molar Flow of 60

kgmole/h.


12

4.28. In the Composition form under the Worksheet tab enter Mole Fractions of 0.5 for n-Heptane and

Toluene in the Feed stream, and a Mole Fraction of 1 for Phenol in the Solvent stream. Both streams

should solve.

4.29. We must now define our design specifications for the column. Go to the Specs Summary sheet under

the Design tab. We want to specify a distillate product rate of 50 kgmole/h with a mole fraction of 0.99

n-Heptane. Enter 50 kgmole/h in the field for Vent Rate and uncheck the active box for Reflux Ratio.


13

4.30. Go to the Specs form under the Design tab. Here we will add a specification for the mole fraction of

heptane in the distillate stream. Click Add and select Column Component Fraction. Select Stream for

Target Type, Heptane for Draw, enter 0.99 for Spec Value, and select n-Heptane for Component.

4.31. The Degrees of Freedom for the column should now be 0. Click Run to begin calculations. The column

should solve.

4.32. We must now add a second column to separate the solvent from the toluene in the Rich-Solvent

stream. Insert a second Distillation Column Sub-Flowsheet from the Model Palette.


14

4.33. Double click on the second column (T-101) to open the Distillation Column Input Expert. On Page 1

enter the following information and click Next when complete.

4.34. On Page 2 of the Input Expert leave the default selections for Once-through, Regular Hysys reboiler.

Click Next.


complete.


15

4.36. On Page 4 and 5 of the Input Expert leave all fields blank and click Done on the final page to configure

the column.

4.37. We must define the design specifications for this second column. Go to the Spec Summary form under

the Design tab. Uncheck the active boxes so that there are no active specifications.

4.38. Go to the Specs form under the Design tab. Here we will create two specifications for the mole

fractions of toluene and phenol in the product streams. Click Add and select Column Component

Fraction. Select Stream for Target Type, Toluene for Draw, enter 0.99 for Spec Value, and select

Toluene for Component.


16

4.39. Add a similar specification for the mole fraction of phenol in the bottoms product stream. Enter .99999

for Spec Value.

4.40. The Degrees of Freedom for the column should now be 0. Click Run to begin calculations. The column

should converge.


17

4.41. We will now recycle the Lean-Solvent stream back to the first column. Add a Recycle block to the

flowsheet from the Model Palette.


18

4.42. Double click on the recycle block (RCY-1). Select stream Lean-Solvent as the Inlet and stream Solvent as

the Outlet. The recycle block should solve.

4.43. Check results. Double click on the first column (T-100) and go to the Cond./Reboiler form under the

Performance tab. Make note of the Condenser and Reboiler Duties.


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4.44. Double click the second column (T-101) and go to the Cond./Reboiler form under the Performance tab.

Make a note of the Condenser and Reboiler Duties.

4.45. The following table will summarize the energy requirements from the case with 1 column versus the

case using extractive distillation.

Single Column Distillation Extractive Distillation

Total Heating Duty (kcal/h) 5,388,000 1,803,000 Total Cooling Duty (kcal/h) 5,390,000 1,410,000

5. Conclusions For the separation of n-heptane and toluene, extractive distillation has a significant advantage in total energy

requirements. Adding phenol as a solvent increased the relative volatilities of n-heptane and toluene in the

mixture and allowed for a much easier separation. However, extractive distillation required more equipment in

this case. Therefore a further analysis on capital versus operational costs would have to be performed in order

to make a decision as to which design is the better option.


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