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Txy Examples with Aspen Plus® V8.0

1. Lesson Objectives Use different property methods in different parts of Aspen Plus

Observe various types of Txy diagrams involving vapor-liquid equilibrium

2. Prerequisites Aspen Plus V8.0

3. Background Different types of Txy diagrams and azeotropes can be observed for different binary systems. For the

ammonia/water system, the vapor curve and liquid curve are far apart from each other. For the n-butane/cis-2-

butene system, the vapor and liquid curves are close together. For the cis-2-butene/trans-2-butene system, the

vapor and liquid curves are very close together. A minimum boiling azeotrope can be observed for the

benzene/ethanol system whereas a maximum boiling azeotrope can be observed for the acetone/chloroform

system.

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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4. Aspen Plus Solution If you are unfamiliar with how to start Aspen Plus, select components, or def ine methods, consult Get Started

Guide for New Users of Aspen Plus.pdf for instructions.

4.01. Create a new simulation in Aspen Plus using the Blank Simulation template. The Components |

Specification | Selection sheet is displayed. Enter AMMONIA, WATER, BENZENE, ETHANOL, ACETONE,

CHCL3, N-BUTANE, CIS-C4H8, and TRANS-C4 for Component ID. Also, enter CIS-2-BUTENE and TRANS-

2-BUTENE for Component name for CIS-C4H8 and TRANS-C4 respectively.

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4.02. Go to the Methods | Specifications | Global sheet. Select PENG-ROB for Base method. Then, select

ALL for Method filter and select UNIQ-RK for Base method. Now, both the PENG-ROB method and the

UNIQ-RK method are available.

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4.03. Click the Next Input button (or press F4) twice so that binary interaction parameters are populated.

4.04. Perform a binary analysis for the ammonia/water system. Click the Analysis | Binary button on the

Home tab of the ribbon. The Analysis | BINRY-1 | Input | Binary Analysis sheet is displayed. Ensure

that AMMONIA is selected for Component 1 and WATER is selected for Component 2. In the Property

options frame, ensure that the UNIQ-RK method is selected for Property method.

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4.05. Click the Run analysis button. A Txy diagram for the ammonia/water binary system is generated. Note

that the T-x curve and T-y curve are far away from each other, which means that it should be easy to

separate these two components using a distillation column.

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4.06. Repeat step 4.05 to perform a binary analysis for the n-butane/cis-2-butene system using the PENG-ROB

method.

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4.07. Click the Run analysis button. A Txy diagram for the n-butane/cis-2-butene system is generated. Note

that the T-x curve and T-y curve are close, which means that it is difficult to separate these two

component using a distillation column (i.e., need a tall and big column if only one distillation column is

used).

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4.08. Repeat step 4.05 to perform a binary analysis for the cis-2-butene/trans-2-butene system using the

PENG-ROB method.

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4.09. Click the Run analysis button. A Txy diagram for the cis-2-butene/trans-2-butene system is generated.

Note that the T-x curve and T-y are very, very close together. Of course, these two components behave

similarly for actual usage and thus, there is no need to separate them most of time .

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4.10. Repeat step 4.05 to perform a binary analysis for the benzene/ethanol system using the UNIQ-RK

method.

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4.11. Click the Run analysis button. A Txy diagram for the benzene/ethanol system is generated. Note that

benzene and ethanol form a minimum boiling azeotrope. To separate these two components, we

typically need more than just a single distillation column.

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4.12. Repeat step 4.05 to perform a binary analysis for the acetone/chloroform system using the UNIQ-RK

method.

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4.13. Click the Run analysis button. A Txy diagram for the acetone/chloroform system is generated. Note

that acetone and chloroform form a maximum boiling azeotrope. To separate these two components,

we typically need more than just a single distillation column.

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5. Conclusions More than one property methods can be made available in one simulation BKP file. Both the PENG-ROB method

and the UNIQ-RK method have been used to generate Txy diagrams for various binary systems involving vapor-

liquid equilibrium. Users can also try to find similar types of Txy diagrams using other binary systems. It is also

important to note that physical property models have their own targeted systems. Therefore, it is important to

select the appropriate physical property model depending on the components in the system.

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

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

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

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