Aspen batch 间歇精馏模拟

Aspen间歇精馏模拟教程

Use this Getting Started section to become familiar with the steps to set up a batch simulation using Aspen Batch Modeler.

You will be modeling a system to recover methanol from a mixture of methanol and water.

The objective is to separate methanol from the mixture with a purity of 99%. This mixture is not ideal given the polarity of the molecules; therefore, for a working pressure of 1atm, you will choose NRTL to model its physical properties.

There are four steps in this process. Click a step to go the instructions for the step.

Step 1 – Set up the Properties for Aspen Batch Modeler

Step 2 – Enter structural data and specifications for the Aspen Batch Modeler block

Step 3 – Enter Operating Steps

Step 4 – Run the simulation and view the results

Step 1 - Set up the Properties for Aspen Batch Modeler

We want to define a Properties file that has the following defined.

Components Property Method

Water NRTL

Methanol

To define this Properties file, follow the steps below.

To set up the Problem Definition file from within Aspen Batch Modeler:

1. Start Aspen Batch Modeler.

2. On the Species form, click Edit Using Aspen Properties.

This will start Aspen Properties.

3. Enter the Components:

Component ID Component name Formula WATER WATER H2O METHANOL METHANOL CH4O

Tip: You can use the Next button

4. Click the Next button Properties Specifications form.

5. On the Properties Specifications form, in the Property method field, select NRTL. Tip: Clicking the pull-down arrow on the field and typing N (the first letter of the property method name) takes you to the right choice much faster than just scrolling down the long list.

6. Click Next

You are taken to the binary parameters forms, where you can view the binary parameters that will be used for Properties Calculations.

7. Click Next

You are prompted to click one of the options shown below.

8. There is no need for further input, so click OK to run the property setup.

9. Close Aspen Properties by clicking File | Exit.

You are prompted with the following:

10. Click Yes to save the file.

The Property setup is now complete.

Step 2 - Enter structural data and specifications for the Aspen Batch Modeler block

The column has been designed as follows:

Configuration

10 Stages (this includes eight trays, condenser and pot)

Vapor-liquid separation

Pot Geometry

Elliptical head

1m diameter

volume of 1m3

Overhead

Total Condenser

Distillate mole flow rate = 4.5kmol/hr

Reflux drum is present

(no need to enter dimension because we are defining fixed pressure profile/holdups; therefore reflux holdup will be entered)

Pressure/Holdups

Pressure profile is fixed

Condenser pressure 1.01325 bar

Column Pressure Drop 0.1 bar

Holdups

Reflux Drum liquid holdup: 0.02 m3

Stage holdup: 0.005 m3

Heat Transfer

Duty: 150 kW

Receivers

One receiver for liquid distillate

Initial condition: total reflux

Initial Conditions

Initial Charge

18kmol of material

Component mole fraction

Methanol: 0.4

Water: 0.6

To Enter the Data

1. Set the configuration to Batch Distillation Column, specify the number of stages and ensure valid phases are Vapor-Liquid on the Configuration Main form

10 Stages (this includes eight trays, condenser, and pot)

Vapor-liquid separation

2. On the Setup | Pot Geometry tab , type the pot dimensions:

Elliptical; 1m diameter; volume of 1m3

3. Click the Overhead form. On the Condenser tab, click Total for Total condenser.

4. On the Reflux tab, type the distillate mole flow rate:

Distillate mole flow rate = 4.5kmol/hr

Reflux drum is present

Note: You need not enter dimension because we are defining fixed pressure profile/holdups. Therefore, reflux holdup will be entered.

5. Click the Jacket Heating form under Setup. On the Jacket Heating tab, enter the pot conditions:

Duty: 150 kW

6. Click Pressure/Holdups | Pressure.

7. On the Pressure tab, type the pressure profile:

Pressure profile is fixed.

Condenser pressure 1.01325 bar

Column Pressure Drop 0.1 bar

8. On the Holdups tab, type the reflux and stage holdup information: Reflux Drum liquid holdup: 0.02 m3

Stage holdup: 0.005 m3

9. Click Receivers | Distillate.

10. On the Distillate tab, define one liquid distillate receiver.

11. Click Initial Conditions | Main.

12. On the Main tab, in the Initial condition field, click Total reflux.

13. On the Initial Charge tab, define the following:

Total initial charge: 18 kmol of material

Component mole fraction:

Methanol: 0.4

Water: 0.6

Note: Do not forget to save your work regularly.

To save your file for the first time:

1. On the File menu, click Save As.

2. In the File name field, type a name, or select a file name to overwrite an existing file:

3. Click Save.

Step 3 - Enter Operating Steps

There are two Operating Steps:

1. Start product draw maintaining a distillate flow rate of 4.5 kmol/hr.

2. Stop when the mole fraction of water in the distillate receiver approaches 0.01 from below. The batch is complete.

To create the required operating steps to run the problem:

1. Click Operating Steps and enter distil in the Name column of the Operating Steps table.

This will create the first operating step distil.

2. On the Changed Parameters tab, create an operating step to distill the methanol by maintaining a distillate flow rate of 4.5 kmol/hr.

3. On the End Condition tab, specify as the end condition the mole fraction of water in the distillate receiver approaching the value of 0.01 from below.

Step 4 - Run the simulation and view the results

The simulation is now ready to run.

Before running the simulation, it is a good idea to create plots for key variables such as: the composition and holdup in the Receiver

the composition and temperature in the pot

and so on

To create plots for key variables:

1. On the Plots form, click the Temperature and Composition to create time plots for pot temperature and mole fractions.

2. Use the Custom plots feature to create plots of the receiver holdups and compositions. Click New on the Custom plots table and specify H2O_distil as the name of the plot.

3. Go to the Holdups Summary Results\Distillate tab. Select the field that displays the WATER mole fraction and drag it on to the plot (H2O_distil) created in the previous step.

4. Use the same approach to create plots of holdups in the receiver and/or the plot.

5. You can change the time units displayed in the plots by clicking the Run Options toolbar button Select the time units in which the user interface should display time field.

14. Click the Run button and view the Simulation Messages window for any relevant messages.

Once the problem has run successfully you can view results in the forms.

Batch time: 1.49 hours/ 89.4 minutes

Pot temperature: 101.05 ℃

Methanol recovery: 6.636 kmol

Note: It is always good practice to restart your simulation in order to restore it to time zero before saving your work.