Overview

The challenge is to produce a working model within ten minutes!

In the Challenge you will:

  • Build a model of a simple ammonia plant;
  • Run the model of the plant;
  • Produce the process flow diagram (PFD) and print the PFD for distribution to your colleagues.

Creating the mass balance for the simple ammonia plant consists of the following 13 steps:

  1. Opening a new project,
  2. Adding StreamFlags,
  3. Dropping the equipment templates onto the page,
  4. Connecting the process equipment with process streams,
  5. Adding components (chemicals) to the system,
  6. Adding reactions,
  7. Adding separation factors,
  8. Running the mass balance,
  9. Updating the flowsheet table,
  10. Updating the equipment table,
  11. Capturing project information,
  12. Printing the Process Flow Diagram, and
  13. Creating Reports.

The view of the screen once you have completed the Challenge will look like the Figure 1 below:

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Figure 1. View screen showing the completed Challenge!

Process Description

Nitrogen and hydrogen are reacted to form ammonia. This reaction has a low conversion and the reaction product is a mixture of all three gases. Thus, the ammonia must then be separated from the reactor product stream. The remaining nitrogen and hydrogen are then recycled.


Step 1. Opening a New Project

Start Cycad Process by clicking on the icon on the Windows Desktop, or by selecting Cycad Process from the Start>Programs>Cycad Process menu.

Cycad starts with a new project already loaded. The view of the Cycad on start up is shown in Figure 2.

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Figure 2: The start-up view for Cycad Process.

It is good practice to save this project immediately and then save it at regular intervals.

Select Save or Save As from the File menu or from the File toolbar and save the file as "Ammonia Plant".


Step 2. Adding Stream Flags

Select the SteamFlagFeed from the Process Library.

While holding the left mouse button down, drag the template across to the page. Release the left mouse button at point where you would like to place the equipment.

This is illustrated in Figure 3 below.

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Figure 3. Dragging the StreamFlagFeed template onto the page.

Select the StreamFlagFeed element that you have just added to the Page by clicking on it.

Its properties are listed in the Properties Viewer. Edit the StreamFlagTag properties by typing "FEED" in the edit space provided. Editing the StreamFlagTag property is shown in Figure 4. Figure 4 is presented on the next page.

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Figure 4. Editing the properties of the StreamFlagTag.

Now click on an empty part of the Page and go to Properties Viewer.

Click on an empty part of the Page. Now go to Properties Viewer. The properties for the Page are displayed in the Viewer. Under the heading Behaviour, you will see a property called SnapTo. Select Guides and Grid from the list that opens when you click in the right hand box opposite this entry. This is illustrated in Figure 5.

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Figure 5. Selecting the SnapTo properties for the Page.

In a similar manner, add a StreamFlagProduct to the Page.


Step 3. Dropping the Equipment Templates onto the Page

In a similar fashion to the manner in which you added the Stream Flags, add a Reactor and a Separator from the Process Library.

This is illustrated in Figure 6.

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Figure 6. Adding a Reactor to the Page.

Also add a StreamJoin element, which represents the joining of two process streams in an operation.

Space them neatly on the Page.

Notice that when you move the drawings they snap to the grid. Use this property to align the elements.

At this stage the diagram should look similar to the page shown in Figure 7.

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Figure 7. Layout of the equipment for the ammonia plant.

The elements of the flowsheet can now be connected using the Process Stream Tool.

This is described below.


Step 4. Connecting the Process Equipment with Process Streams

Select the Process Stream Tool from the Process Toolbar as shown in Figure 8.

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Figure 8. Select the Process Stream Tool.

Connect the pieces of equipment with streams in the following manner:

  • Move the cursor to a connection point, shown as a light blue cross, on the equipment. If the connection is valid the connection point will change to a red square. If it is not, it will display a red cross.

  • Click the left mouse button and while holding the mouse button down, move the cursor to the input of the piece of equipment that represents the next operation in the process flowsheet. The connection point will change to a red square if the connection is allowed.

  • Release the mouse to draw the Process Stream.

This is illustrated in Figure 9.

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Figure 9. Drawing Process Streams using the Process Stream Tool.

Select the Selection Pointer Tool. The Process Stream that you have just added is highlighted.

Check that the squares of both the start point and the end point of the Process Stream are red, which indicates that they have successfully connected with the equipment at either end of the Process Stream.

The properties of the stream are shown in the Properties Viewer. Edit the ProcessStreamTag to give the stream an identity, as shown in Figure 10. The value of the ProcessStreamTag is displayed in a circle on the stream.

The ProcessStreamTag can be moved and positioned along the stream by selecting its control point, which is shown as a yellow diamond, and dragging the Tag to its desired position.

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Figure 10. Entering values for the ProcessStreamTag.

Edit the value of the ProcessStreamTag property to give the stream an identity. The Tag does not need to be a number.

Connect all the Process Units using the Process Stream Tool so that the flowsheet is similar to that illustrated in

Figure 11.

Remember to check that all Process Streams are properly connected.

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Figure 11. The process flowsheet for the Ammonia Plant.


Step 5. Adding Components (Chemicals) to the Mass Balance

Press the "Add Components" Button, which is illustrated in Figure 12, to launch the Components Selection Form.

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Figure 12. The Add Components Button on the Process Toolbar.

The Components Selection Form is shown in Figure 13. To select a component double click on it in the list. To remove accidently selected components simply double click on it in the selected components list. For this course use “NBS 1982” as far as possible.

Select Ar (g), H2 (g), N2 (g) and NH3 (g) and press the OK”” button.

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Figure 13. The Components Selection Form.

The selected components are now added to each Process Stream of the flow sheet and this can be verified by selecting the Stream Manager tab on the tab list above the Page Viewer.

If no Process Streams are Selected when you press this tab, the All Streams sheet is displayed. However, if a Process Stream is selected prior to pressing the Stream Manager tab, the Selected Stream sheet is displayed.

The All Stream sheet at this point in the Challenge is shown in Figure 14.

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Figure 14. The All Streams sheet in Stream Manager.

This Figure illustrates the Process Balance sheet of the Stream Manager, showing the four selected components that have been successfully added to the system.

At this point, the flowsheet has been drawn, and the components have been entered. It now time to provide values for the feed material.

In the Page Viewer, select the feed stream, then press Stream Manager to get the view shown in Figure 15.

Enter values for the nitrogen and hydrogen in the Stream Manager.

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Figure 15. Enter the values for the mass in the feed stream.

Now some functionality needs to be added to the Reactor and the Separator. This is done in the next two sections.


Step 6. Adding Reactions

In the Page view, select the Reactor by clicking on it.

Move to the "Reactions" property in the Property Viewer as shown in Figure 16.

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Figure 16. The reactions property of the Reactor.

Press on the ellipsis button (that is, the button with the three dots) that is displayed when you click in the right hand box of the "Reactions" property.

This will launch the Reactions Form.

The Reactions Form is shown in Figure 17:

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Figure 17. The Reactions Form, where the reactions are entered.

Press the "Add” button first, and then type in the reaction and the reaction conversion as shown in Figure 17:

N2 (g) + 3 H2 (g) --> 2 NH3 (g)

ext = 0.1

The reaction should be typed so that there is a space between the stoichiometric number and the component, and between the chemical formula and the state of the component. You may only have reactions amongst components that have already been added to the balance.

Press the "Apply" button. You now have a Reactor that has a single reaction in it.

(It is possible to add more reactions. You would simply press the "Add” button again, and then type in the new reaction, and its associated conversion after the expression "ext = ".)


Step 7. Adding Separation Factors

In the Page Viewer, select the Separator. In the Properties Viewer, launch the Separations form by pressing the ellipsis button opposite the Parameters property.

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Figure 18. The Separation Property of the Separator.

Enter the separation factors for each component in the form in the same manner as they are shown in Figure 19.

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Figure 19. The Separations Form.

Formula
State
Factor
H2
(g)
0.1
N2
(g)
0.3
NH3
(g)
0.95
Ar
(g)
0.0

Now that the Reactor and the Separator have some functionality, you can solve the mass balance.


Step 8. Running the Mass Balance

You are now in a position to run the mass and energy balance. Press the "Run Project" shown in Figure 20.

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Figure 20. The "Run Application"

Pressing the "Run Project" button launches the Convergence Form, shown in Figure 21, that provides the user with feedback on the progress of the calculation.

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Figure 21. Convergence Form

The above Convergence Form showing that there is one recycle stream that has converged to an error less than 1e-9.

While the program is running, Messages are displayed in the Messages Viewer.

These provide feedback on the course of the calculation. For example, as shown in Figure 22, is the convergence error (that is the sum-of-squared differences of the component masses for the tear streams between iterations), indicating the progress towards the convergence tolerance.

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Figure 22. The Messages Viewer.

This provides basic feedback on the progress of the calculations.

In this case, the mass balance converged in 2 iterations that took 0.094 seconds to complete (note, this may be different in your simulation).

Once the calculation has run, the cursor will change to allow input.

Select either the "Accept Values" or "Reject Values" on the Convergence Form.

If you select the "Reject Values" button, then the values of

the streams are not updated with the results of the calculation.

In this case, press the "Accept Values" button.

The results can be found in the Stream Manager, which can be compared against those in Error: Reference source not found.

This shows the Process Balance sheet of the Stream Manager.

Table 1: Calculated results after running the ammonia plant balance.

Stream Description
Plant Feed
Reactor Feed
Reactor Product
Final Product
Recycle
Stream Number
001
002
003
004
005
H2
(g)
hydrogen
t/h
1.000
8.950
8.833
0.883
7.950
N2
(g)
nitrogen
t/h
2.000
5.405
4.865
1.459
3.405
NH3
(g)
ammonia
t/h
0.000
0.035
0.692
0.657
0.035
Ar
(g)
argon
t/h
0.000
0.000
0.000
0.000
0.000

If you select the "Stream" tab within the Stream Manager, you will be shown an individual stream if one has been selected in the Page Viewer.

For example, with Stream 002 selected, the "Stream" sheet displays the details shown in Figure 23 for that stream.

Since this is an uncomplicated flowsheet, involving only one input and one output, select the output stream and check, the total mass-in is the same as the total mass-out.

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Figure 23. The "Stream" sheet of the Stream Manager when the reactor feed stream is pre-selected in the Page Viewer.


Step 9. Updating the Flowsheet Table

The Flowsheet Table provides details of the mass flows, temperatures and other properties for streams at the bottom of the Process Flow Diagram.

To display this information, you need to choose the information you would like to display, and then update the table. Navigate there by selecting the Stream Manager tab above the Page Viewer and then selecting the “All Streams” tab in the Stream Manager.

The information that you would like to display is selected by checking the boxes in the left column of the Process Balance sheet in the Stream Manager.

This is shown in Figure 24.

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Figure 24. Selecting components, elements, and properties to be represented on the Flowsheet Table.

Select the values shown in Figure 24. Once the required values are selected, return to the Page Viewer.

With the mouse hovering over the Flowsheet Table, right click to activate the context menu. From the context menu,

select "Update Grid".

This will automatically fill the grid with the values of the selected variables for the Process Streams on the current page. The result of this is shown in Figure 25.

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Figure 25. The updated Flowsheet Table.

Now it is time to update the equipment list.


Step 10. Updating the Equipment Table

Before you update the Equipment List you should make sure that the equipment has an Equipment Tag, an Equipment Description and the NumberOf property filled in correctly.

Select the Reactor and navigate to the EquipmentTag property in the Property Viewer. Enter "A1" for the Tag (you can have any descriptor) and "AMMONIA REACTOR" for the Description.

The NumberOf property tracks the number of repeated pieces of the same equipment that are to be installed in the plant.

For example, often pumps are installed in duplicates so in that case the NumberOf property should be 2. This is shown in Figure 26.

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Figure 26. Changing the Equipment List properties.

Repeat this for the Separator.

Now navigate to the Equipment List Table at the top right hand side of the page.

Right click the mouse when the mouse pointer is hovering above the Equipment Table.

This launches the context menu. From the context menu select "Update Grid" to fill the table with the data you have just entered.

This is shown in Figure 27 below.

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Figure 27. Updating the Equipment List Table.


Step 11. Capturing the Project Information

Information for the project can be entered in the various forms that are launched by clicking on the “File” tab in the ribbon, shown in Figure 28.

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Figure 28. Inserting the project information and company logos

All the project, user, and cclient information can be inputted here.

The project name and the project number are automatically added to the tables in the bottom right hand side of the page.

In addition to these details, you can load your logo and the client’s logo, which will be automatically displayed on the page. Experiment for yourself by adding values to these forms and the other forms found in the Settings menu item.

A watermark can also be added to the page by selecting Settings > Watermark. The Watermark is a text item and is used to convey important information to the engineering team about the status of your drawing.

For example, you might enter "DRAFT ISSUE – FOR REVIEW PURPOSES ONLY" so that team members know that this is a draft and that the values displayed will not be used for design purposes.

Save your file!


Step 12. Printing the Drawing

The drawing is printed in the standard manner by first selecting the File>Print Flowsheet. This is shown in Figure 29.

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Figure 29. The Print Setup selection.

Configure the printing options to suit the situation. Typically, drawings are printed on either A4 or A3 paper depending on what printer is available. However, the software does allow for any size printing to be undertaken.

It is recommended that you print to a PDF printer by default.

Once happy with the settings select “Print”.


Step 13. Mass Balance, Equipment List and Design Criteria

Congratulations! You just have completed your first mass balance. The screen should look like that shown at the beginning of the Challenge, that is, Figure 1.

You have produced a Process Flow Diagram as your main output. You may want to view some of the other outputs that you can provide.

Press the Mass Balance tab above the Page Viewer to launch the mass balance output sheet. This is shown in Figure 30. The variables that you chose earlier in the “All Streams” sheet of the Stream Manager tab have been transferred to this sheet.

In addition to the variables that you selected in the Process Balance sheet, the Design Factor and the Design Flow have been shown.

The Design Factor is entered in the Properties Viewer when a Process Stream is highlighted. It is multiplied by the volumetric flow to give a Design Flow and is always provided.

The Design factor allows you to indicate that pipe sizing must not be performed on the calculated flow obtained by the mass balance, but increased or decreased as the case may be by a certain factor.

This sheet can be exported to MS Excel. The context menu is launched by right clicking the mouse when the mouse pointer is hovering over the sheet. Choose "Export To Excel" from the context menu.

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Figure 30. The Mass Balance output from of the Challenge.

The Equipment List is constructed when you press the Equipment List tab above the Page Viewer. The Equipment List for the Challenge is shown in Figure 31.

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Figure 31. The Equipment List output from the Challenge.

The Design Criteria are all the data that you have entered and some of the results of the calculation required for design purposes.

The view of the Design Criteria for the Challenge is shown in Figure 32.

These Design Criteria provide you will a summary of all the information that you have added in order to solve the mass and energy balance.

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Figure 32. The Design Criteria – Section Tab - for the Challenge.