Matbal 001H Flowsheet CycloHexane

Matbal-001H Revised: Nov 7, 2012

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Cyclohexane Production with Aspen HYSYS® V8.0

Lesson Objectives 1.

Construct an Aspen HYSYS flowsheet simulation of the production of cyclohexane via benzene

hydrogenation

Become familiar with user interface and tools associated with Aspen HYSYS

Prerequisites 2.

Aspen HYSYS V8.0

Knowledge of chemical process operations

Background/Problem 3.

Construct an Aspen HYSYS simulation to model the production of cyclohexane via benzene hydrogenation. The

simplified flowsheet for this process is shown below. Fresh benzene and hydrogen feed streams are first fed

through a heater to bring the streams up to reactor feed temperature and pressure conditions. This feed

mixture is then sent to a fixed-bed catalytic reactor where 3 hydrogen molecules react with 1 benzene molecule

to form cyclohexane. This simulation will use a conversion reactor block to model this reaction. The reactor

effluent stream is then sent to a flash tank to separate the light and heavy components of the mixture. The

vapor stream coming off the flash tank is recycled back to the feed mixture after a small purge stream is

removed to prevent impurities from building up in the system. The majority of the liquid stream leaving the flash

tank goes to a distillation column to purify the cyclohexane product, while a small portion of the liquid stream is

recycled back to the feed mixture to minimize losses of benzene. Process operating specifications are listed on

the following page.


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Feed Streams Benzene Feed (BZFEED) Composition (mole fraction) Hydrogen - Nitrogen - Methane - Benzene 1 Total Flow (lbmol/hr) 100 Temperature (°F) 100 Pressure (psia) 15

Hydrogen Feed (H2FEED) Hydrogen 97.5 Nitrogen 0.5 Methane 2.0 Benzene - Total Flow (lbmol/hr) 310 Temperature (°F) 120 Pressure (psia) 335

Distillation Column Number of stages 15 Feed stage 8 Reflux Ratio 1.2 Cyclohexane recovery 99.99 mole % in bottoms Condenser Pressure 200 psia Reboiler Pressure 210 psia

Feed Preheater Outlet Temperature 300 °F Outlet Pressure 330 psia

Reactor Stoichiometry Benzene + 3H2 Cyclohexane Conversion 99.8% of benzene Outlet temperature 400°F Pressure drop 15psi

Flash Tank Temperature 120°F Pressure drop 5psi

Purge Stream

Purge rate is 8% of vapor recycle stream

Liquid Split 70% of liquid stream goes to distillation column

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

reflect an industrial application or real situation.


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Aspen HYSYS Solution 4.

4.01. Start Aspen HYSYS V8.0, select New on the Start Page to start a new simulation.

4.02. Create a component list. In the Component Lists folder, select the Add button to create a new HYSYS

component list.

4.03. Define components. Use the Find button to select the following components: Hydrogen, Nitrogen,

Methane, Benzene, and Cyclohexane.

4.04. Select a property package. In the Fluid Packages folder in the navigation pane click Add. Select SRK as

the property package.


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4.05. We must now specify the reaction involved in this process. Go to Reactions folder in the navigation

pane and click Add to add a reaction set.

4.06. In Reactions | Set-1 select Add Reaction. Select the Hysys radio button and select Conversion. Then

click Add Reaction. Once a new reaction (Rxn-1) can be seen on the reaction set page, close the

Reactions window shown below.

4.07. Double click on Rxn-1 to define the reaction. In the reaction property window, add components

Benzene, Hydrogen, and Cyclohexane to the Stoichiometry Info grid. Enter -1, -3, and 1, respectively,

for stoichiometry coefficients. In the Basis grid select Benzene as Base Component, Overall for Rxn

Phase, 99.8 for Co, and 0 for both C1 and C2. This indicates that the reaction will convert 99.8% of

benzene regardless of temperature. Close this window when complete.


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4.08. Attach this reaction set to a fluid package by clicking the Add to FP button. Select Basis-1 and click Add

Set to Fluid Package. The reaction set should now be ready.

4.09. We are now ready to enter the simulation environment. Click the Simulation button in the bottom left

of the screen.


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4.10. First we will place a Mixer and a Heater block onto the flowsheet.

4.11. Double click on the mixer (MIX-100) to open the mixer property window. Create 2 inlet streams:

H2FEED, BZFEED; and 1 outlet stream: ToPreHeat.


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4.12. Go to the Worksheet tab to define streams H2FEED and BZFEED. First we will define the Conditions of

each stream. For H2FEED, enter a Temperature of 120°F, a Pressure of 335 psia, and a Molar Flow of

310 lbmole/hr. For BZFEED, enter a Temperature of 100°F, a Pressure of 15 psia, and a Molar Flow of

100 lbmole/hr. Note that you can change the global unit set to Field if the units are different than those

displayed below.


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4.13. Next we will define the Composition of the two feed streams. In the Worksheet tab go to the

Composition form. Enter the compositions shown below. You will notice that after inputting the

composition, the mixer will successfully solve for all properties.

4.14. Double click on the heater block (E-100) to configure the heater. Select stream ToPreHeat as the inlet

and create an outlet stream called R-IN. Add an energy stream called PreHeatQ.


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4.15. Go to the Worksheet tab and specify the outlet stream R-IN temperature and pressure. Enter 300°F for

Temperature and 330 psia for Pressure.


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4.16. The flowsheet should look like the following at this point.

4.17. We will now add a Conversion Reactor to the flowsheet. Press F12 on the keyboard to open the

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

4.18. In the Conversion Reactor property window, select the inlet stream to be R-IN, and create a Liquid

Outlet called LIQ and a Vapour Outlet called VAP. In the Parameters form, enter a Delta P of 15 psi.


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4.19. In the Reactions tab, select Set-1 for Reaction Set. Notice that when the reactor solves, the contents of

the reactor are entirely in the vapor phase, therefore there is no liquid flow leaving the bottom of the

reactor.


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4.20. Next we will add a Cooler to the main flowsheet to cool down the vapor stream leaving the reactor.

4.21. Double click on the cooler block (E-101) to open the cooler property window. Select VAP as the inlet

stream and create an outlet stream called COOL. Also add an energy stream called COOLQ. In the

Parameters form enter a Delta P of 5 psi.


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4.22. Go to the Worksheet tab to specify the outlet stream temperature. Enter 120°F for the Temperature of

stream COOL. The cooler will solve.


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4.23. We will now add a Separator block to separate the vapor and liquid phases of stream COOL. From the

model palette add a Separator to the flowsheet.

4.24. Double click on the separator block (V-100). Select COOL as the inlet stream and create liquid and vapor

outlet streams called LIQ1 and VAP1. The separator should solve.


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4.25. The flowsheet should now look like the following.

4.26. We will now add 2 Tee blocks, 1 for each of the separator outlet streams. One tee will be used to purge

a portion of the vapor stream to prevent impurities from building up in the system. The other tee will

be used to recycle a portion of the liquid back to the mixer and the rest of the liquid will be fed to a

distillation column.


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4.27. Double click on the first Tee block (TEE-100). Select stream VAP1 as the inlet, and create 2 outlet

streams VAPREC, and PURGE.


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4.28. Go to the Parameters page and enter 0.08 for the Flow Ratio for stream PURGE.

4.29. You can rotate the icon for a block by selecting the icon and clicking the Rotate button in the

Flowsheet/Modify tab in the ribbon.


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4.30. Double click the second Tee block (TEE-101). Select LIQ1 for the inlet stream and create 2 outlet

streams LIQREC, and ToColumn.

4.31. In the Parameters tab enter a Flow Ratio of 0.7 for stream ToColumn.


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(FAQ) Useful Option To Know: Saving Checkpoints

Save “checkpoints” as you go. Once you have a working section of the flowsheet, save as a new

file name, so you can revert to an earlier checkpoint if the current one becomes too complex to

troubleshoot or convergence errors become persistent.


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4.33. We are now ready to connect the recycle streams back to the mixer. On the main flowsheet, add 2

Recycle blocks.


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4.34. Double click on the first recycle block (RCY-1). Select stream VAPREC as the inlet stream and create an

outlet stream called VAPToMixer.

4.35. Double click the second recycle block (RCY-2). Select LIQREC as the inlet stream and create an outlet

stream called LIQToMixer.


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4.36. Connect the recycle streams back to the mixer. Double click the mixer block (MX-100). On the Design |

Connections sheet add LIQToMixer and VAPToMixer as inlet streams. The flowsheet should converge.



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4.38. We are now ready to add the distillation column to the flowsheet. From the Model Palette add a

Distillation Column Sub-Flowsheet.

4.39. Double click on the Distillation Column Sub-flowsheet. This will launch the Distillation Column Input

Expert. Enter 15 for # Stages and specify ToColumn as inlet stream on stage 8_Main TS. Select Full

Reflux for Condenser, create an Ovhd Vapour Outlet stream called Off Gas, create Bottoms Liquid

Outlet stream called Bot, and add a Condenser Energy Stream called Cond Q. When finished click Next.


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4.40. On page 2 of the Distillation Column Input Expert keep the default selections for Reboiler Configuration

and click Next.


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4.41. On page 3 of the Distillation Column Input Expert enter a condenser pressure of 200 psia and a reboiler

pressure of 210 psia. Click Next.

4.42. On page 4 of the Distillation Column Input Expert leave fields for temperature estimates blank and click

Next. On the final page of the column expert enter a molar Reflux Ratio of 1.2 and click Done to

configure the column.


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4.43. After completing the input for the column expert the Column property window will open. We want to

create a design specification in order to ensure that 99.99% of the cyclohexane is recovered in the

bottoms stream. Go to the Design | Specs sheet. Click Add and select Column Component Recovery.

In the Comp Recovery window specify Stream for Target Type, Bot@COL1 for Draw, 0.9999 for Spec

Value, and Cyclohexane for Components. Close this window when finished.


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4.44. Go to the Specs Summary sheet and make sure that the only active specs are Reflux Ratio and Comp

Recovery. The column should converge.

4.45. The flowsheet is now complete and should look like the following.


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This flowsheet is now complete.

Conclusion 5.This is a simplified process simulation, however you should now have learned the basic skills to create and

manipulate a steady state chemical process simulation in Aspen HYSYS V8.0.

Copyright 6.

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

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Matbal 001H Flowsheet CycloHexane

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