Transcript ASPEN DYNAMICS

ASPEN DYNAMICS
EXAMPLES
PRESENTED BY
UBAID UR REHMAN
2008-CHEM-19
ANAM ASIF
2008-CHEM-107
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PRESENTATION LAYOUT
Introduction to Example
The Aspen Plus Simulation
Setting Up the Dynamic Simulation
Running the Batch Column Example
Initializing the Batch Column Example in Aspen
Dynamics
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INTRODUCTION
This is an example of a batch column simulation and illustrates
these features of Aspen Dynamics:
• Use of scripts to automate initialization of an Aspen Dynamic
flow sheet
• Use of tasks to start up and operate the batch reactor
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STATEMENT
A mixture of methanol, ethanol and water is to be separated
using a batch distillation column. The composition of the charge
is 30% ethanol, 30% methanol and 40% water by weight.
The required product purity is 68% ethanol w/w.
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THE ASPEN PLUS SIMULATION
• Aspen Plus has been used to set up the flow sheet for the
batch column, which will be exported to Aspen Dynamics and
initialized to be full of nitrogen at 20 C and 1 atmosphere
• The column has been modeled using a RadFrac block.
• Feed streams for the charge and nitrogen have been specified
together with vapor and liquid distillate streams and a bottoms
stream.
• The column has been specified with 10 stages, a partial
vaporliquid condenser and a kettle reboiler.
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THE ASPEN PLUS SIMULATION
• The column dimensions have been specified on the RadFrac
Dynamic form together with the sump and reflux drum size
and geometry.
• The LMTD heat transfer option has been selected for the
condenser and the cooling medium temperature specified as
200C
• The Constant temperature heat transfer option has been
selected for the reboiler and the medium temperature has been
specified as 120 C.
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USE OF SCRIPT
To set up the dynamic simulation
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SETTING UP THE DYNAMIC
SIMULATION
• A flowsheet level script called Setup and a RadFrac model
script called Empty.
• The Flowsheet level script does the following:
1. Adds a reflux ratio controller
2. Sets the feed flow rates to zero
3. Calls the RadFrac Empty script to initialize the column to be
full of nitrogen at 20 C and 1 atmosphere.
4. Performs an initialization run.
5. Saves a snapshot
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RUNNING THE BATCH
COLUMN EXAMPLE
To run the BatchColumn example:
1. In Aspen Plus, open BatchColumn.bkp. If you installed
Aspen Dynamics in the default location, BatchColumn.bkp is in:
C:\Program Files\AspenTech\Aspen Dynamics
12.1\Examples\BatchColumn.
2. Perform a run.
3. Export it as a flow-driven dynamic simulation file.
4. Exit Aspen Plus.
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INITIALIZING THE BATCH
COLUMN EXAMPLE IN ASPEN
DYNAMICS
1. In Aspen Dynamics, open BatchColumn.dynf
2. In the All Items pane of the Simulation Explorer, ensure
Flow sheet is selected. In the Contents pane, double-click Add
Script.
3. Enter a name for the script, for example, Setup.
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INITIALIZING THE BATCH COLUMN
EXAMPLE IN ASPEN DYNAMICS
4. In the text editor window, click the right mouse button and
point to Insert, then click File. Insert BatchColumnScript.txt.
5. Again click the right mouse button and click Invoke Script.
Close the text editor window.
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INITIALIZING THE BATCH COLUMN
EXAMPLE IN ASPEN DYNAMICS
6. Now create a task called BatchOperation.
To do this:
7. In the Contents pane of the Simulation Explorer, double-click
Add Task. Enter the name BatchOperation.
8. In the text editor window, select all of the existing text with
the mouse (or use Ctrl-A). Click the right mouse button and point to
Insert, then click File. Insert BatchOperationTask.txt.
9. Again click with the right mouse button and click Compile or press
F8. Close the text editor window.
10. In the Contents pane of the Simulation Explorer, double-click the
task to activate it.
11. Change the run mode to Dynamic and perform a dynamic run.
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USE 0F TASK
To start up and operate the batch reactor
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OPERATING SEQUENCE
The operating sequence defined by the tasks is: At time = 0.5
hours:
1. Ramp the mass flow rate of the Feed stream to 1000 kg/hr
over 0.1 hours.
2. Wait until the cumulative mass flow of stream Feed is >= 1000
kg.
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OPERATING SEQUENCE
3. Step the mass flow rate of the Feed stream to 0 kg/hr.
4. Wait for 3 minutes.
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OPERATING SEQUENCE
5. Increase the flow of the Nitrogen feed stream to 0.1 kmol/hr.
This is needed to maintain the pressure in the column.
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OPERATING SEQUENCE
6.Ramp the reboiler medium temperature to 80 C over 30
minutes.
7. Wait until the reflux drum level >= 0.3 m.
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OPERATING SEQUENCE
8. Start the reflux flow.
9. Wait for 3 minutes.
10. Start the product draw.
11. Ramp the reboiler medium temperature to 90 over 30
minutes.
12. Wait until the mass fraction of methanol in the distillate
receiver reaches 0.68.
13. Pause the simulation.
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OPERATING SEQUENCE
14. Use plots and tables to view the results of the simulation
during the dynamic run.
15. If you wish to repeat the simulation, rewind to saved
snapshot
Empty_Initial and then run again.
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