Работа №.7. Моделирование динамических режимов технологических схем совместно с контурами регулирования

АспенДинамикс является мощным средством анализа динамики сложных технологических схем и образует унегрированную систему с Аспен Плюс, который обеспечивает синтез и анализ стационарных технологических схем. При использовании этого инструмента вначале проводится синтез и анализ технологической схемы в стационарном режиме, затем проводится переход к стационарному режиму. При этом система требует ввода дополнительных данных о характеристиках используемого оборудования, связанные с емкостями и задерживающими способностями отдельных элементов технологических схем, которые необходимы для моделировании переходных процессах в отдельных аппаратах технологических схем. После ввода всех технологических данных, проводится моделирование в динамическом режиме и системы сама расставляет необходимые регуляторы в тех точках технологической схемы, где заданы условия работы. Например, уровень в емкости, температура и давление в аппарате, и др. После этого можно экспортировать полученные результаты динамического моделирования в специально созданную рабочую папку. Из этой рабочей папки можно открыть задачу моделирования в программном комплексе АспенДинамикс, исследовать динамическое поведение схемы при наличии различных возмущений и усовершенствовать, при необходимости контуры регулирования и изменить их настройки для получения заданного качества регулирования.

В Работе №7 будет проведено создание схемы динамического моделирования процесса, а в Работе №8 будет проведено исследование динамических свойст и модификация контуров управления и выбор оптимальных настроек регуляиров.

Выполнение работ производится в точном соотвтетствии с рабочими инструкциями программного комплекса АспенДинамкс

1 Tutorial 1 - Entering Dynamic

Data and Exporting a File

In this tutorial you will:

Use Aspen Plus to modify an existing steady-state example

Add the equipment data and heat transfer information

necessary to simulate the process dynamically in Aspen

Dynamics

Generate and export the dynamic simulation files from Aspen

Plus for using in Aspen Dynamics

Allow about 20 minutes for this tutorial.

Experienced Aspen Plus users You will be opening the file

MCHSPEC in the directory Program Files\AspenTech\Aspen Plus

11.1\GUI\xmp. If you already know how to do this, go to page 1-5.

1-2  Tutorial 1 - Entering Dynamic Data and Exporting a File Getting Started Guide

Starting Aspen Plus

To start Aspen Plus:

1. Click the Start button, point to Programs, then AspenTech,

then Aspen Engineering Suite, then Aspen Plus 11.1, then

click the Aspen Plus User Interface.

The Aspen Plus Startup dialog box appears:

2. Select Blank Simulation, then click OK.

The Aspen Plus main window appears (see the picture on the

next page):

Getting Started Guide Tutorial 1 - Entering Dynamics Data and Exporting a File  1-3

1-4  Tutorial 1 - Entering Dynamic Data and Exporting a File Getting Started Guide

Opening an Existing Simulation

To open an existing simulation:

1. From the File menu, click Open.

2. In the Open dialog box, navigate to the folder where the

Aspen Plus User Interface was installed (for example,

C:\Program Files\AspenTech\Aspen Plus 11.1\GUI) then open

the xmp folder.

3. Click the file MCHSPEC to select it, then click Open.

A dialog box appears, asking if you want to close the current

run before opening a new run.

Getting Started Guide Tutorial 1 - Entering Dynamics Data and Exporting a File  1-5

4. Click Yes to close the current run and open the MCHSPEC

example backup file.

The MCHSPEC example file opens and the process flowsheet

appears (see the picture on the next page).

If you cannot see the Dynamic toolbar as shown

above, follow these steps to add the toolbar:

5. Ensure the flowsheet window is active, by clicking in it.

6. From the View menu, click Toolbar.

1-6  Tutorial 1 - Entering Dynamic Data and Exporting a File Getting Started Guide

7. In the Toolbars dialog box, ensure the Dynamic check box is

selected, like this:

8. Click OK.

The Dynamic toolbar is added to your toolbars.

About the MCH Steady-State

Simulation

The MCH example describes a simulation in which 98% pure

methylcyclohexane (MCH) is recovered from a mixture of MCH

and toluene. Because these components form a close-boiling

system that is difficult to separate by simple binary distillation,

phenol is used as an extractant to enhance the relative volatility of

MCH over toluene.

Aspen Plususes a design specification to determine the phenol

flow rate required to achieve the 98% purity in the distillate. You

can view the results of stream 2 to see that the required phenol

flow rate is approximately 1515 lbmol/hr.

Aspen Plus design specifications are often used for design

purposes and generally do not correspond directly to plant control

strategies. For this reason, Aspen Dynamics does not automatically

convert steady-state design specifications to dynamic controllers.

In tutorial 3, you will create a controller to maintain the product

purity.

Getting Started Guide Tutorial 1 - Entering Dynamics Data and Exporting a File  1-7

Entering Dynamic Data in Aspen Plus

Before entering any dynamic data in Aspen Plus, you would

usually run a steady-state simulation to ensure it completes

normally. For this tutorial you need not do this, because the

example file has already completed normally and has been saved

with results.

Before you can enter dynamic data, you have to click the Dynamic

button on the Dynamic toolbar. This enables you to access the

dynamic input data sheets for each block.

1. To access the dynamic data for the MCH column, click the

Dynamic button so that it is pressed in.

Dynamic button, pressed in

The RadFrac block (B1) contains forms that require dynamic

data, so the status indicator on the status bar changes to

Required Input Incomplete.

You can now use the Next button to guide you through the

required input data forms.

2. On the Data Browser toolbar, click the Next button and

the Flowsheet Complete dialog box appears.

1-8  Tutorial 1 - Entering Dynamic Data and Exporting a File Getting Started Guide

3. In the Flowsheet Complete dialog box, click OK to display

the first required input form.

The Data Browser opens with the Block B1 (RADFRAC)

Dynamic form displayed.

Note At this stage, no data is required on this form.

Getting Started Guide Tutorial 1 - Entering Dynamics Data and Exporting a File  1-9

Entering Condenser and Reboiler

Geometry and Heat Transfer Data

In this section, you will enter geometry and heat transfer data for

the condenser and reboiler. Geometry data is used to calculate the

vessel holdups. The required data are the vessel orientation, head

type, length and diameter.

For heat transfer purposes, you will use log-mean temperature

difference (LMTD) assumptions for the condenser. Heat duty is

dependent on the log mean temperature differential between the

process fluid and the heating/cooling medium. The reboiler heat

duty is assumed constant:

1. Click the Condenser sheet.

2. In the Heat transfer option box, click the down arrow to see

more options and from the list displayed, click LMTD.

Do not change the other default values. The Condenser sheet is

now complete.

3. Click Next to go to the Reflux Drum sheet.

4. In the Vessel Type box, select Horizontal from the list box.

1-10  Tutorial 1 - Entering Dynamic Data and Exporting a File Getting Started Guide

5. In the Length box, type 6 ft and in the Diameter box, type 3 ft,

like this:

Do not change the other values. The Reflux Drum sheet is now

complete.

6. Click Next to continue and the Sump sheet appears.

7. In the Height box, type 5 ft and in the Diameter box, type 3 ft.

Do not change the other values.

8. Press Enter to accept the input.

The Sump sheet is now complete and you have finished entering

data for the condenser and reboiler.

Entering Tray Geometry

The tray geometry data is used to calculate the holdups on the

trays. Column B1 has 22 theoretical stages.Stage1 being the

condenser and Stage22 the reboiler. Stages 2 through 21 are the

theoretical trays.

In the previous section, you specified the necessary information for

the condenser (stage 1) and the reboiler (stage 22). In this section,

you will enter the tray diameter geometry for stages 2 through 21.

The default values of the other parameters will be used.

1. Click Next to go to the Hydraulics sheet.

2. In the Stage1 column, type 2 and in the Stage2 column, type

21.

3. In the Diameter column, delete 6.56168 and type 5.

Getting Started Guide Tutorial 1 - Entering Dynamics Data and Exporting a File  1-11

4. Press Enter to accept the input and leave the remaining values

at their defaults.

The Tray geometry specifications are now complete and the

sheet looks like this:

5. Click Next to continue.

The Required Input Complete dialog box appears.

You have entered the additional data needed for the RadFrac

column and you are now ready to run the steady-state simulation.

You do this to ensure that all the results required to export the

dynamic simulation are calculated.

1-12  Tutorial 1 - Entering Dynamic Data and Exporting a File Getting Started Guide

Running the Steady-State Simulation

Having entered the dynamic specifications, you run the steady-state

simulation. To do this:

1. On the Required Input Complete dialog box, click OK.

Aspen Plus displays the Control Panel where you can view

the simulation messages during the run.

2. Wait for the message Simulation Calculations Completed to

appear and Results Available to appear in the status bar. This

indicates that the run is complete.

3. Click the Close button , to close the Control Panel window.

Getting Started Guide Tutorial 1 - Entering Dynamics Data and Exporting a File  1-13

Exporting the Dynamic Simulation

You are now ready to export the files necessary to run this

simulation dynamically. To do this:

1. From the File menu, click Export.

2. Go to the drive and folder where you want to save your file,

for example C:\My Simulations. Choose a folder other than

the xmp folder from which you selected the MCHSPEC

example because this folder is for system files only.

3. In the Save as type box, select Flow Driven Dyn Simulation

(*.dynf & *dyn.appdf).

4. In the File name box, type Mchdyn, then click Save.

These files are created:

Mchdyn.dynf, the Aspen Dynamics input file

Mchdyndyn.appdf, which contains physical property data for

use by Properties Plus during the dynamic simulation

Saving the Backup File

To save your changes to the Aspen Plus backup file:

1. From the File menu, click Save As.

2. Go to the folder where you saved your exported dynamic

simulation files.

3. In the Save As box, select Aspen Plus Backup files (*.bkp).

1-14  Tutorial 1 - Entering Dynamic Data and Exporting a File Getting Started Guide

4. In the File name box, type Mchdyn then click Save.

A dialog box appears requesting if you want to save the file in

Aspen Plus Document (quick restart) format.

5. There is no need to save it as an Aspen Plus Document file, so

click No.

Your simulation is saved as a backup file called Mchdyn.bkp.

Quitting Aspen Plus

Now that you have generated the files necessary for a dynamic run,

you are ready to run Aspen Dynamics. To quit Aspen Plus:

➤ From the File menu, click Exit.

Tutorial Review

In this basic tutorial, you have learnt how to use Aspen Plus to:

Modify an existing steady-state example

Add the equipment data and heat transfer information

necessary to simulate the process dynamically in Aspen

Dynamics

Generate and export the dynamic simulation files for use in

Aspen Dynamics

Getting Started Guide Tutorial 2 - Modifying the Control Scheme  2-1