aspen flaresys analyzer v8 start

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Version Number: V8.0

December 2012

Copyright (c) 1981-2012 by Aspen Technology, Inc. All rights reserved.

Aspen Flare System Analyzer, Aspen Flarenet, and the aspen leaf logo are trademarks or registeredtrademarks of Aspen Technology, Inc., Burlington, MA. All other brand and product names aretrademarks or registered trademarks of their respective companies.

This document is intended as a guide to using AspenTech's software. This documentation

contains AspenTech proprietary and confidential information and may not be disclosed,used, or copied without the prior consent of AspenTech or as set forth in the applicable

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Phone: (781) 221-6400

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1 Introduction 1

Contents1 Introduction.........................................................................................................2

About this document.........................................................................................2Audience.........................................................................................................2Related Documentation.....................................................................................2

Technical Support ............................................................................................2

2 Building and Running a Model ..............................................................................4

Overview.........................................................................................................4Data Requirements...........................................................................................5

Pipe Segment Data.................................................................................5Relief Source Data..................................................................................6System Design Constraints......................................................................7

Starting Aspen Flare System Analyzer.................................................................7

Starting a New Model........................................................................................8Saving the Model ........................................................................................... 12Building the Pipe Network ............................................................................... 12

Starting the Pipe Network .....................................................................12

Completing the Pipe Network ................................................................. 16Defining the Scenarios .................................................................................... 26Defining the Sources ...................................................................................... 33

Rating the Network ........................................................................................44

Printing Data and Results ................................................................................ 47

3 Developing the Model .........................................................................................49

Overview....................................................................................................... 49Data Requirements.........................................................................................50

Pipe Segment Data............................................................................... 50Relief Source Data................................................................................ 51

System Design Constraints....................................................................53Opening the Old Model.................................................................................... 53

Updating the Model ........................................................................................54

Defining the Scenarios .................................................................................... 63Defining the Sources ...................................................................................... 66

Sizing the Network .........................................................................................73

Design Calculations ........................................................................................75



2 Building and Running aModel

This section provides information on the following topics:

Overview

Data Requirements

Starting Aspen Flare System Analyzer

Starting a New Model

Saving the Model

Building the Pipe Network

Defining the Scenario

Defining the Sources

OverviewThis Getting Started tutorial shows the fundamental principles involved in

using Aspen Flare System Analyzer to design and rate a new flare system.

This guided tour will expose you to most of the major features of Aspen FlareSystem Analyzer.

This tutorial assumes that you are familiar with the use of Microsoft Windows

and have some prior experience in the design of flare systems.

This example consists of the following main parts:

1 Building The Pipe Network - Pipes and nodes will be added using either

the Process Flowsheet or Pipe Manager.

2 Defining the Scenarios - Different scenarios will be set up to simulate

various process conditions.3 Defining The Sources - Relieving sources will be added to each scenario.

4 Sizing the Network - Finally, the pipe network will be simulated and

results will be viewed both in textual and graphical form.



2 Building and Running a Model 5

Data RequirementsBefore you can start to build a computer model of the flare header system,you must first define all the data that will determine your system.

When you are sizing a flare system, the initial pipe diameters may affect the

solution when there is a liquid phase and the liquid knockout drum ismodeled. You should initially size a network using vapor phase methods.

Pipe Segment DataData Description

Connectivity You would normally have prepared a system sketch thatdefines the nodes to which the pipe segments are connected.

Length and fittings

loss coefficients foreach pipe segment

These will be based upon either a preliminary or detailed

isometric drawing of the piping.

Diameter and pipe

schedule for eachpipe segment

If you are rating an existing network, these will normally be

taken from the flare system P&ID. If you are sizing a newflare system, the pipe diameters that you define are relativelyunimportant since they will be overwritten by the sizingalgorithms. It is recommended that reasonable diameters bedefined, so that the sizing algorithm initializes to a conditionthat will give faster convergence.

The following diagram shows the connectivity of the system that you will bedesigning in this example.

Fig 2.1

The piping in the network diagram is detailed in the following table:



Item Length(m)

InternalDiameter(mm)

WallThickness(mm)

FittingsLoss

ElevationChange(m)

Flare Tip 3.0 0

Stack 100 876.3 19.05 0 100

Header 3 50 876.3 19.05 0 0

Tail Pipe 1 25 428.65 14.275 0 0

Tail Pipe 2 25 428.65 14.275 0 0

The flare tip is not a pipe segment, but rather a node that represents a zerolength piece of pipe with defined fittings loss coefficients. Since the internal

diameter is not specified, it will assume the same diameter as the upstream

pipe segment. Fittings loss coefficients for the flare tip exclude pipeenlargement and junction losses for the connection to the upstream pipewhich will automatically be calculated.

Relief Source DataThe following data must be specified for the sources:

Data Description

Flow andComposition

These may vary for each scenario that you are evaluating. If arelief source is not used in a particular scenario, the flow maybe set to zero. Flow refers to the quantity of fluid that thesource valve must pass as a consequence of the plant upsetcondition. Rated Flow refers to the quantity of fluid that thesource valve will pass due to its physical construction . RatedFlow must always be greater than or equal to Flow.

Maximum AllowableBack Pressure(MABP)

This is the maximum pressure that can exist at the outlet of the device (source) without affecting its capacity.

Downstreamtemperature

This temperature is used as the pressure independenttemperature at which the source enters the network. Thistemperature is used when ideal gas enthalpies are used tocalculate the heat balance, or as an initial guess when anyother enthalpy method is used.

Upstream pressureand temperature

These are only used if Ideal Gas enthalpies are not used forthe heat balance. These may vary for each scenario that youare evaluating. With relief valves, the flowing pressure shouldbe used.

Discharge flangesize

This will normally be determined from the relief valve sizingcalculations. If this value is unknown then the field should beleft empty to ignore the pressure change from the valve tothe downstream pipe due to the swage.

In this example, you will consider three scenarios that represent one fire caseand two single blocked discharge cases. The following tables define the source

data for each scenario.

Default Source Data




SourceName

Flowrate(kg/hr)

FlangeSize(mm)

Mol.Wt.

USTemp(C)

DSTemp(C)

US Pres.(barabs)

MABP(barabs)

Source 1 100000 300 20 15 15 10 5.0

Source 2 100000 300 25 15 15 10 5.0

Source 1 is a control valve while Source 2 is a relief valve.

Source 1 Only Data

SourceName

Flowrate(kg/hr)

FlangeSize(mm)

Mol.Wt.

USTemp(C)

DSTemp(C)

US Pres.(barabs)

MABP(barabs)

Source 1 100000 300 20 15 15 10 5.0

Source 2 0 300 25 15 15 10 5.0

Source 2 Only Data

SourceName

Flowrate(kg/hr)

FlangeSize(mm)

Mol.Wt.

USTemp(C)

DSTemp(C)

US Pres.(barabs)

MABP(barabs)

Source 1 0 300 20 15 15 10 5.0

Source 2 100000 300 25 15 15 10 5.0

System Design ConstraintsIn this case, the following data is used for both scenarios:

Maximum allowable mach number - 0.50 for both main headers andtailpipes.

Maximum allowable noise – 100 dB for both main headers and tailpipes.

Starting Aspen Flare System

AnalyzerThe installation process creates a short-cut to Aspen Flare System Analyzer inthe Start menu.

To Start Aspen Flare System Analyzer:

1 Select the Start menu.2 Navigate to and click the Aspen Flare System Analyzer icon under

Programs | AspenTech | Process Modeling <version>

Now you are ready to begin working with Aspen Flare System Analyzer.

When you start Aspen Flare System Analyzer, the Aspen Flare System

Analyzer application window appears. Before setting up the Getting Startedcase, you should choose the Aspen Flare System Analyzer units set for

displaying information. You can check your current units set by accessing the

Preferences Editor:



1 Click the aspenONE Button which is on the upper left corner of the

application window; then select Preferences from the Application Menu.

The Preferences Editor is displayed.

Fig 2.2

2 The current unit set is shown in the Units box. The default unit set is

Metric, which will be used for this example.

3 Confirm that the Edit Objects on Add check box is selected. This optionwill open the object editor view each time a new object is added.

4 Click OK to close the Preferences Editor.

Starting a New ModelTo start a new case, do one of the following:

1 Click New on the Quick Access Toolbar beside the aspenONE Button; or,click the aspenONE Button, then click New from the Application Menu.

The Documentation Editor is displayed.

2 Enter the appropriate data into the User Name, Job Code, Project, andDescription fields, and then click OK.

The Component Manager is displayed.




Fig 2.3

Note: The Selected component list is empty, indicating that no components

have yet been installed in the case.

There are a number of ways to select components for your simulation. One

method is to filter the database for a certain component type. In this model,we will be using the following components: Methane, Ethane and Propane.

To add Methane using the filter option:

1 Ensure that the HC check box in the Component types group is selected.

2 Typing methane in the Selection filter field. Notice that as you aretyping, the Available components list will be filtered out to show only

the matching components.

3 Double-click Methane in the Available components list. Methane willnow be selected and shown in the Selected components list.

Note: Initially, all the check boxes in the Component types group are

selected. You can clear them by clicking Invert.




Fig 2.5

5 Click OK to close the Component Manager and accept the list of

components.

6 In the Navigation Pane, double-click Inputs on the Views pane, and then

select Components from the list. The Components data view will be

displayed:

Fig 2.6



Note: You can use the horizontal scroll bar at the bottom of the sheet to view

all of the component properties.

Saving the ModelIt is good practice to periodically save your case by doing one of the

following:

Click the Save icon on the Quick Access Toolbar.

Click the aspenONE Button on the upper left corner of the application

window, and then select Save from the Application Menu.

Press Ctrl+S.

As this is the first time you have saved your case, the All Files dialog box will

be displayed.

After selecting an appropriate disk drive and directory in the Save in list,enter the name of the file to which you want to save the case in the File

name field.

Note: You do not need to include the .fnwx extension; Aspen Flare System

Analyzer will add it automatically.

Click Save to close the dialog box and save the file.

Building the Pipe NetworkSince all scenarios have a common pipe network, you should first build thepipe network model via the Process Flowsheet.

Starting the Pipe Network1 Click Process Flowsheet in Views group on the Home tab of the

Ribbon. The Process Flowsheet will be displayed, and the ProcessFlowsheet tab will be shown on the Ribbon.

Note: Before proceeding any further, make sure that the Edit Objects on

Add check box on the General tab of the Preferences Editor is selected.




Fig 2.7

At this point the flowsheet should be blank, since we have not added a singleobject yet.

The desired objects can be added by using either of the following methods:

Clicking the Palette on the Process Flowsheet tab will open the

Palette, which displays all the objects available in Aspen Flare System

Analyzer. You can add an object by dragging it onto the ProcessFlowsheet.

Fig 2.8



Objects can also be added via the Pipe Manager and the NodeManager. These are accessible through Pipes and Nodes in the Build

group on the Home tab of the Ribbon, respectively.

For example, to add a pipe:

2 Click the pipe icon in the Palette, drag and drop it to a proper place on

the Process Flowsheet. In the Pipe Editor that is displayed, type Stack inthe Name field. Click OK to close the Pipe Editor.

3 Next, add a Flare Tip. Drag the Flare Tip icon on the Palette to theProcess Flowsheet. Since the Edit Objects on Add check box is selected,The Flare Tip Editor will be displayed after the Flare Tip is installed to

the flowsheet:

Fig 2.9

By default the Flare Tip has been named as FlareTip1, which can be changedto a more appropriate name as follows:

4 Click in the Name field on the Connections tab of the Flare Tip Editor.

5 Delete the default name and type Flare Tip as the new name.

Since this example is of smaller size, the Location field will be left blank.

This field is only useful for larger cases with multiple sections (areas)

within a same plant. Now you need to specify the pipe, which will besimulated as a flare stack, and it is attached to the Flare Tip.

6 Select Stack from the list in the Upstream node field.

7 In the At field, select Downstream as the pipe end connected to the

Flare Tip.




In order to complete the input on the Flare Tip Editor, you need tospecify the Diameter and the Fitting Loss values on the Calculations

tab.

Note: The Fitting Loss Coefficient Basis should be set to Total Pressure

to indicate that the loss coefficient we are defining will calculate the pressure

loss in the Flare Tip including the velocity pressure loss.8 On the Calculations tab, enter 876.3 as the diameter and 3 as the fitting

loss in the appropriate fields.

Fig 2.10

Now you have provided all the necessary information about the Flare Tip.

9 Click OK to close the view.

Notice that now two new objects have been added to the Process

Flowsheet. These may be drawn one on top of the other so you shouldmanually arrange them by clicking and dragging the object icons.

10 Open the Stack Object Editor by double-clicking the pipe icon on the

flowsheet and move to the Dimensions tab.

11 Specify the Length as 100 m and the Elevation Change as 100 m.

This will result in a vertical pipe measuring 100 m tall.

12 Select the Nominal Diameter as 36 inch and the Pipe Schedule as 40.



Fig 2.11

13 On the Methods tab, confirm that Vertical Pipe and VLE Method are setas Model Default.

In this example, every pipe segment uses the default models which are

specified on the Methods tab of the Calculation Options Editor.

14 Click OK to close the Stack Object Editor.

Now you need to add another pipe segment which will be added using the

Pipe Manager.

Completing the Pipe Network1 Click Pipes in the Build group on the Home tab of the Ribbon. The Pipe

Manager will be displayed.




Fig 2.12

2 Click Add. A new pipe will be added to the list. Click Edit.

The Pipe Editor will be displayed.



Fig 2.13

3 Change the name to Header 3.

4 Move to the Dimensions tab and enter the following data in theappropriate fields:

Field Value

Length (m) 50

Nominal Diameter (inch) 36

Pipe Schedule 40

5 Click OK to close the Pipe Editor.

6 Close the Pipe Manager by clicking Close.

You need to attach Header 3 with Stack using a node. Aspen FlareSystem Analyzer allows you to choose between a variety of nodes, since

you need a simple connection between the two pipes, a Connector nodewill be used.

7 On the Palette, click the Connector icon and drag it to the Process

Flowsheet.

This will open the Connector Editor.




Fig 2.14

8 On the Connections tab, enter the new name as Con 1.

9 In the Downstream node field, select Stack and specify the connection

at Upstream (of Stack) in the At field.

10 In the Upstream node field, select Header 3 and specify the connection

at Downstream (of Header 3) in the At field.

11 Move to the Calculations tab.



Fig 2.15

Notice that by default the Angle has a value of 90 deg and the Fitting

loss method is set as Calculated. These and the other entries may be

left at their default values for this example.

12 Click OK to close the Connector Editor.

Now, a tee will be added, using the Node Manager, to combine the flow

from the two sources.13 Click Nodes in the Build group on the Home tab of the Ribbon. The

Node Manager will be displayed.




Fig 2.16

14 Click Add and Select Tee from the list. A new Tee will be added.

Click Edit. The Tee Editor will be displayed.



Fig 2.17

15 Change the name to Tee 1 in the Name field.

16 Specify the Downstream node connection to be Header 3 and selectUpstream from the At field.

17 Move to the Calculations tab and verify that the Fitting loss methods

setting is Miller. The remaining fields may be left at their default values.

18 Close the Tee Editor by clicking OK.

19 Click Close to close the Node Manager.

Now, you can add two pipe segments to the upstream and branch sectionof Tee 1 using the Pipe Manager.

20 Open the Pipe Manager by clicking Pipes in the Build group.




Fig 2.18

21 Click Add to add a new pipe segment. Click Edit to open the Pipe Editor.

22 Change the default pipe name to Tail Pipe 1.

23 Specify Tee 1 as the Downstream node connection and select Branchin the At field.

Note: Setting the tailpipe option to Yes will cause the pressure drop to be

calculated using the rated flows rather than the actual flow. For this pipewhich is a tail pipe to a control valve source, the rated flow and actual flow

will be the same so the setting of this option will have no effect.



Fig 2.19

24 Move to the Dimensions tab and specify the Length as 25 m.

25 Set Nominal Diameter as 18 inch from the list.

26 Click OK to close the Pipe Editor for Tail Pipe 1. Repeat Step 21 to add

another pipe segment.

27 Change the new pipe segment name to Tail Pipe 2.

28 Specify Tee 1 as the Downstream node connection and select

Upstream in the At field. Since this pipe is a tail pipe for a relief valve,

set the Tailpipe option to Yes.


30 Set Nominal Diameter as 18 inch from the list.




Fig 2.20



In the Navigation Pane area which is docked to the left side of the Process

Flowsheet, select Inputs | Pipes on the Views pane.

The Pipes data sheet displays the data for all of the pipe segments:

Fig 2.21

You could also check the Process Flowsheet to ensure that the proper

connections have been made. A portion of the Process Flowsheet is displayedbelow:



Fig 2.22

Defining the ScenariosYou now need to define the data for the entire scenario, the Default

Scenario, Source 1 Only and Source 2 Only scenarios. Since each case

must contain at least one scenario, a set of default scenario data is created

when you start a new case. We need to modify this data.1 Click Scenarios in the Build group on the Home tab of the Ribbon.

The Scenario Manager will be displayed.




Fig 2.23

2 Double-click Default Scenario in the Scenarios list.



Fig 2.24

3 The Scenario Editor will be displayed. Alternatively, you could select

Default Scenario in the Scenarios list, and then click Edit.

Update the header Mach Number limit on the Constraints tab for theDefault Scenario as shown below, then click OK to close the Scenario

Editor and return to the Scenario Manager.




Fig 2.25

Now we should add the data for the Source 1 Only scenario.

4 Make sure that Default Scenario is highlighted in the Scenarios list onthe Scenario Manager. Click Clone. A new scenario will be added to the

list as shown below.



Fig 2.26

5 Click Edit to open the Scenario Editor for the new scenario.

6 Change the default name to Source 1 Only and verify the data for the

Source 1 Only scenario is the same as shown below.




Fig 2.27

7 Click OK to close the Scenario Editor for Source 1 Only. Repeat Step 4

to add a new scenario.

8 Change the name for the new scenario to Source 2 Only.



Fig 2.28

9 Verify the data for the new scenario on the Constraints tab is the sameas shown below.




Fig 2.29

10 Click OK to close the Scenario Editor and return to the ScenarioManager, then click Close to close the Scenario Manager.

Defining the SourcesYou will now enter the source data for the sources in all scenarios. Since for

the first part of the example you will be defining the source compositions interms of molecular weight, the program preferences must be set to acceptthe compositions on this basis.

1 Click the aspenONE Button at the upper left corner of the application

window. Select Preferences from the Application Menu that is displayed.The Preferences Editor will be displayed.



Fig 2.30

Ensure that Molecular Weight is selected in the Composition Basisfield on the Defaults tab.




Fig 2.31

2 Click OK to close the Preferences Editor.

Before defining a set of source data, you must select the scenario which

corresponds to this data. You will start by defining the data for theDefault Scenario.

3 Make sure that the Default Scenario is selected in the Run group on the

Home tab of the Ribbon. Any open data views would now display data forthis scenario. This field is regarded as the Scenario Selector.

You can now add the data corresponding to this scenario for each source.

4 Click Nodes in the Build group. The Node Manager will be displayed:



Fig 2.32

5 Click Add and select Control Valve from the list that is displayed.




Fig 2.33

Click Edit. The Control Valve Editor will be displayed.

6 Change the name to Source 1. Select Tail Pipe 1 in the Outlet field andset connection to be at Upstream (of Tail Pipe 1).



Fig 2.34

7 Move to the Conditions tab and set the Mass Flow as 100000 kg/hr. Inthis example, the inlet pressure and temperature are the same as thedefault values, but this will not normally be the case.




Fig 2.35

8 On the Composition tab, specify the Mol. Wt. to be 20. Once you haveentered the Mol. Wt. and tabbed to the next field, you will notice the

composition will be calculated to give the required Mol. Wt.



Fig 2.36

Note: The Mole Fractions are automatically estimated from the MolecularWeight. Because HC is selected from the list, only hydrocarbon components

will be used to match the Molecular Weight.

9 Click OK to close the Control Valve Editor for Source 1. Click Add inthe Node Manager to add a new source. The node selection list will again

be displayed.

10 Select Relief Valve from the list, and then click Edit to open the Relief Valve Editor.

11 Name the new source as Source 2 on the Connections tab.

12 Select Tail Pipe 2 in the Outlet field and set connection to be atUpstream (of Tail Pipe 2).




Fig 2.37

13 On the Conditions tab, check that the relief valve set pressure or MAWPis set to the default value of 10 bar which is correct for this source. Selectthe Auto check box next to the Relieving Pressure field. This tells Aspen

Flare System Analyzer to calculate the relieving pressure from the MAWP

and the selected Contingency, which should be left as Operating in this

case. Check that the relieving pressure is calculated as 10.89 bar.14 Still on the Conditions tab, check that the Allowable Backpressure is

set to 5.0 bar. Enter the required Mass Flow rate for this source of 100000 kg/ hr. Select the Auto check box next to the Rated flow field.This tells Aspen Flare System Analyzer to calculate the rated flow for the

valve from the specified fluid conditions and properties, valve type and

orifice area.

15 Still on the Conditions tab, click the box next to the Orifice Area Per

Valve field to select orifice code api_T. Check that the orifice area is



updated to 16774 mm2 and notice the rated flow calculation is updated toreflect the increased orifice area.

16 On the Composition tab, specify the Mol. Wt. of the fluid to be 25.When you tab away from this field, Aspen Flare System Analyzer willcalculate the composition of the fluid from the mole weight. Click back on

the Conditions tab to confirm that the Rated flow calculation has been

updated to give a rated flow of 108,214 kg/hr.

Fig 2.38

17 Click OK to close the Relief Valve Editor.

The Node Manager will now appear as follows:




Fig 2.39

18 Close the Node Manager by clicking Close.

19 In the Navigation Pane area which is docked to the left of the ProcessFlowsheet, select Inputs | Sources on the Views pane.

The Sources data sheet for the Default Scenario will be displayed:

Fig 2.40

You must now add the source data for the other two scenarios.20 Select the Source 1 Only scenario from the Scenario Selector list in the

Run group on the Home tab of the Ribbon. Any open data views will nowdisplay data for this scenario.

21 Make the following changes to the flowrates from the Sources data sheetin the Source 1 Only scenario (all other information remains the same):

Source 1 - Mass Flow 100000 kg/hr, Mol. Wt. 20




Finally reselect the Default Scenario from the Scenario Selector.

22 Next, select the Source 2 Only scenario from the Scenario Selector list

in the Run group on the Home tab of the Ribbon. Make the followingchanges to the Source 2 Only:


Source 2 - Mass Flow 100000 kg/hr, Mol. Wt. 25Finally reselect the Default Scenario from the Scenario Selector.

Rating the NetworkWe have now entered all the model data and can now make the sizingcalculations. We will need to set the calculation options before starting the

calculations.

1 Click Options in the Run group on the Home tab of the Ribbon. TheCalculation Options Editor will be displayed:




Fig 2.41

2 For this example, we are going to use the default methods and settingsdefined when Aspen Flare System Analyzer creates a new model. This

includes the following key options:

On the General tab, Calculation Mode should be set to Rating, EnableHeat Transfer check box should be cleared, Include Kinetic Energy

check box should be cleared.

On the Scenarios tab, Calculate should be selected for All Scenarios.



On the Methods tab, the VLE Method should be set to CompressibleGas, the Enthalpy Method to Ideal Gas and all pressure drop methods

to Isothermal Gas.

Click OK to close the Calculation Options Editor. You can now start thecalculations.

3 Click Run in the Run group on the Home tab.

Fig 2.42

Once the calculations are complete you can review the results.

4 Select Results | Messages from the Views tab on the Navigation Pane.The Messages data view will be displayed.

Fig 2.43

The above view contains general information and warning messages

regarding the calculations.

5 Select Source 1 Only from the Scenario selector in the Run group on the

Home tab.

6 Select Results | Pressure/Flow Summary from the Navigation Pane.

The Pressure/Flow Summary will be displayed:




Fig 2.44

With the Pressure/Flow Summary sheet open, select each scenario in turnusing the Scenario Selector in the Run group.

Note: In the scenario Source 1 Only, the mach number problem on TailPipe 1 is automatically highlighted.

7 At this point, save the model using either the Save icon on the Quick

Access Toolbar, or click the aspenONE Button at the upper left corner of the application window then select Save from the Application Menu.

Printing Data and ResultsTo print data and results:

1 Click the aspenONE Button, and then select Print from the ApplicationMenu. The Print dialog box will be displayed.

2 Select the appropriate check boxes for the items that you want to print.

Also select the All Scenarios check box to print the results for all of thescenarios instead of just the current scenario.

If you want to print to a file, click Text, then specify the file location andFile name in the Save dialog box.

3 Click Preview to preview the layout in the Print Preview window before

anything is printed.



3 Developing the Model 49

3 Developing the Model

This section provides information on the following topics:

Overview

Data Requirements

Opening the Old Model

Updating the Model Defining the Scenarios


Sizing the Network

Design Calculations

OverviewIn this chapter of the Getting Started tutorial you will change the networkdesigned in Chapter 2 to model the tie-in of two new control valves into our

current system. The modified system will be simulated for two new scenarios,one each for the new sources.

This tutorial assumes that you are familiar with the use of Microsoft Windows

and have some prior experience in the design of flare systems.

Note: This tutorial is a continuation of the one in the previous chapter and

requires that you complete that chapter before continuing with this one.

This example consists of the following main parts:

1 Building The Pipe Network - Pipes and nodes will be added using either

the Process Flowsheet or the Manager views.

2 Defining the Scenarios - Different scenarios will be set up to simulate

various process conditions.3 Defining The Sources - Relieving sources will be added to each scenario.

4 Sizing the Network - Finally, the pipe network will be simulated andresults will be viewed both in textual and graphical form.



Data RequirementsBefore you can start to upgrade a computer model of the existing flare headersystem, you must first define all the data that will determine your system.

Pipe Segment DataData Description

Connectivity You would normally have prepared a system sketch thatdefines the nodes to which the new pipe segments areconnected.

Length and fittingsloss coefficients fornew pipe segment

These will be based upon either a preliminary or detailedisometric drawing of the piping.

Diameter and pipeschedule for eachpipe segment

If you are rating an existing network, these will normally betaken from the flare system P&ID. If you are sizing a newflare system, the pipe diameters that you define arerelatively unimportant since they will be overwritten by the

sizing algorithms. It is recommended that reasonablediameters be defined, so that the sizing algorithm initialisesto a condition that will give faster convergence.

Note: When you are sizing a flare system, the initial pipe diameters may

affect the solution when there is a liquid phase and the liquid knockout drumis modelled. You should initially size a network using vapour phase methods.

The following diagram shows the connectivity of the system which includes

the new sources you will be adding in this example.

Fig 3.1

The pipe segments in the network diagram are detailed in the following table.

SegmentName

Length(m)

NominalDiameter (inch)

Schedule FittingsLoss

ElevationChange (m)

Stack 100 36 40 0 100

Header 1 50 28 30 0 0

Header 2 50 28 30 0 0




SegmentName

Length(m)

NominalDiameter (inch)

Schedule FittingsLoss

ElevationChange (m)

Header 3 50 36 40 0 0

Tail Pipe 1 25 18 40 0 0

Tail Pipe 2 25 18 40 0 0

Tail Pipe 3 25 12 40 0 0Tail Pipe 4 25 18 40 0 0

The new pipe segments Header 1, Header 2, Tail Pipe 3 and Tail Pipe 4 will be

added.

Relief Source DataThe following data must be specified for the sources:

Data Description

Flow andComposition

These may vary for each scenario that you are evaluating.If a relief source is not used in a particular scenario, the

flow may be set to zero. The Flow refers to the quantity of fluid that the source valve must pass as a consequence of the plant upset condition. The Rated Flow refers to thequantity of fluid that the source valve will pass due to itsphysical construction. Rated flow must always be greaterthan or equal to flow.

Maximum AllowableBack Pressure(MABP)

This is the maximum pressure that can exist at the outlet of the device (source) without affecting its capacity.

DownstreamTemperature

This temperature is used as the pressure independenttemperature at which the source enters the network. Thistemperature is used when ideal gas enthalpies are used tocalculate the heat balance, or as an initial guess when anyother enthalpy method is used.

Upstream Pressureand Temperature

These are only used if the Ideal Gas enthalpies are notused for the heat balance. These may vary for eachscenario that you are evaluating. With relief valves, theflowing pressure should be used.

Discharge FlangeSize

This will normally be determined from the relief valve sizingcalculations.

In this example, you will consider five scenarios that represent one fire caseand four single blocked discharge cases. The following tables define the

source data for each scenario.

The discharge flange size values are left undefined. In this case, they areassumed to have the same diameter as the attached pipes.

Default Source Data

Source

Name

Flowrate

(kg/hr)

Mol.

Wt.

US

Temp(C)

DS

Temp(C)

US Pres.

(barabs)

MABP

(barabs)

Source 1 100000 20 15 15 10 5.0

Source 2 100000 25 15 15 10 5.0



SourceName

Flowrate(kg/hr)

Mol.Wt.

USTemp(C)

DSTemp(C)

US Pres.(barabs)

MABP(barabs)

Source 3 100000 30 15 15 10 5.0

Source 4 100000 35 15 15 10 5.0

Source 1 Only Data

SourceName

Flowrate(kg/hr)

Mol.Wt.

USTemp(C)

DSTemp(C)

US Pres.(barabs)

MABP(barabs)

Source 1 100000 20 15 15 10 5.0

Source 2 0 25 15 15 10 5.0

Source 3 0 30 15 15 10 5.0

Source 4 0 35 15 15 10 5.0

Source 2 Only Data

SourceName

Flowrate(kg/hr)

Mol.Wt.

USTemp(C)

DSTemp(C)

US Pres.(barabs)

MABP(barabs)

Source 1 0 20 15 15 10 5.0

Source 2 100000 25 15 15 10 5.0

Source 3 0 30 15 15 10 5.0

Source 4 0 35 15 15 10 5.0

Source 3 Only Data

SourceName

Flowrate(kg/hr)

Mol.Wt.

USTemp(C)

DSTemp(C)

US Pres.(barabs)

MABP(barabs)

Source 1 0 20 15 15 10 5.0

Source 2 0 25 15 15 10 5.0

Source 3 100000 30 15 15 10 5.0

Source 4 0 35 15 15 10 5.0

Source 4 Only Data

Source

Name

Flowrate

(kg/hr)

Mol.

Wt.

US

Temp(C)

DS

Temp(C)

US Pres.

(barabs)

MABP

(barabs)

Source 1 0 20 15 15 10 5.0

Source 2 0 25 15 15 10 5.0

Source 3 0 30 15 15 10 5.0

Source 4 100000 35 15 15 10 5.0




System Design ConstraintsIn this case, the following data is used for all scenarios:

Maximum allowable mach number - 0.50 for both main headers and

tailpipes.

Maximum Noise – 100 dB for both main headers and tailpipes.

Opening the Old Model1 Start Aspen Flare System Analyzer and open the previously stored case

that you have just saved in Chapter 2.

2 Click Open from the Quick Access Toolbar that is docked beside theaspenONE Button on the upper left corner of the application window.

-or-

Click the aspenONE Button, then click Open from the Application Menu

that is displayed.

-or-

Press Alt then 2.

3 The Open File dialog box will be displayed.

Fig 3.2

4 Click the Look in field to select the appropriate disk drive and directory.

5 Next, select the file that you created in Chapter 2 from the list, and thenclick Open.



Updating the ModelYou need to add new pipe segments to the existing model, but first you mustdelete the connection between Tee 1 and Header 3. Open the ProcessFlowsheet and delete the connection as follows:

1 Click Toggle Connect/Arrange Mode on the Process Flowsheet tabon the Ribbon to switch to Connect mode and select the connectionbetween Tee 1 and Header 3.

Fig 3.3

2 Press DELETE. Click Toggle Connect/Arrange Mode again to switch

back to Arrange mode.

To add a Tee section after Header 3:

3 Open the Node Manager by clicking Nodes in the Build group on the

Home tab on the Ribbon.




Fig 3.4

4 Click Add and select Tee from the list that is displayed. Click Edit.

The Tee Editor will be displayed:



Fig 3.5

5 Specify the name to be Tee 3, the Downstream node connection to be

Header 3 and select Upstream from the At field.

Note: Since this example is of smaller size, therefore the Location field willbe left blank. This field is only useful for larger case with multiple sections

(areas) within a same plant.

6 Move to the Calculations tab and verify that the Fitting Loss Methodsetting is Miller.


8 Click Close to close the Node Manager.

Now, you can add two pipe segments to the upstream and branch section

of Tee 3 using the Pipe Manager.

9 Open the Pipe Manager by clicking Pipes in the Build group.




Fig 3.6

10 Click Add to add a new pipe segment. Click Edit to open the Pipe Editor.

11 Change the default pipe name to Tail Pipe 4.

12 Specify Tee 3 as the Downstream node connection and select Branchin the At field.



Fig 3.7


14 Select Nominal Diameter as 18 inch from the list provided.

15 Click OK to close the Pipe Editor. Repeat Step 10 to add another pipesegment.

16 Change the default name of the new pipe segment to Header 2.

17 Specify Tee 3 as the Downstream node connection and selectUpstream in the At field.


19 Set Nominal Diameter as 28 inch and Schedule as 30 from the listprovided.




Fig 3.8



Notice that three new objects have been added to the Process Flowsheet.You can manually arrange them by clicking and dragging the object icons.

Now you will add a tee section using the Palette.

22 Open the Palette (if it is not displayed) by clicking the Palette icon onthe Process Flowsheet tab on the Ribbon.

23 Click the Tee icon in the Palette window, drag and drop it to the ProcessFlowsheet.

Since the Edit Objects on Add check box is selected, The Tee Editor will

be displayed.



Fig 3.9

24 Change the default name to Tee 2.

25 Specify Header 2 as the Downstream node connection and selectUpstream in the At field. On the Calculations tab, verify the Fitting

loss method is Miller.


Now, you can add two pipe segments to the upstream and branch section

of Tee 2 using the Palette.

27 Click the Pipe icon, drag and drop it onto the Process Flowsheet to add a

new pipe segment.

28 On the Pipe Editor, change the default pipe name to Tail Pipe 3.

29 Specify Tee 2 as the Downstream node connection and select Branch

in the At field.




Fig 3.10


31 Verify that the Nominal Diameter is 12 inch.

32 Close the Pipe Editor by clicking OK.

33 Repeat Step 27 to add another pipe segment.

34 Change the default name of the new pipe segment to Header 1.

35 Specify Tee 2 as the Downstream node connection and select

Upstream in the At field.

36 Specify Tee 1 as the Upstream connection and select Downstream inthe At field.


38 Set Nominal Diameter as 28 inch and Schedule as 30.



Fig 3.11


Select Inputs | Pipes from the Views menu on the Navigation Pane. The

Pipes data sheet displays the data for all of the pipe segments:

Fig 3.12

At this point you might want to rearrange the new items on the Process

Flowsheet. The Process Flowsheet should be similar as displayed below:




Fig 3.13

Defining the ScenariosYou now need to define the data for the new scenarios, the Source 3 Onlyand Source 4 Only scenarios. The existing model already contains three

scenarios which you will still be using in this example. To add the newscenarios:

1 Click Scenarios in the Build group on the Home tab o the Ribbon.

The Scenario Manager will be displayed.



Fig 3.14

2 Click Default Scenario in the Scenarios list to highlight it. Click Clone.A new scenario is added to the list.

Fig 3.15

3 Click Edit to open the Scenario Editor.4 Change the default name to Source 3 Only. On the Constraints tab,

verify that the values of the Mach Number in both Headers andTailpipes groups are 0.5 as shown below:




Fig 3.16

5 Repeat Step 2 to add a new scenario. Click Edit.

6 Change the default name for the new scenario to Source 4 Only.



Fig 3.17

7 Verify that the values of the Mach Number on the Constraints tab in

both Headers and Tailpipes groups are 0.5.

8 Click OK to close the Scenario Editor and return to the ScenarioManager. Now select Default Scenario and click Current to make this

the working scenario. Click Close to close the Scenario Manager.


You will now enter the source data for the sources in all scenarios. Since forthe first part of the example you will be defining the source compositions in

terms of molecular weight, the program preferences must be set to acceptthe compositions on this basis as described in Chapter 2.

1 Click Nodes in the Build menu on the Home tab.

The Node Manager will be displayed.




Fig 3.18

2 Click Add and select Control Valve from the list displayed.



Fig 3.19

Click Edit. The Control Valve Editor will be displayed:

Fig 3.20

3 Change the default name to Source 3. Select Tail Pipe 3 in the Outletfield and set connection to be at Upstream (of Tail Pipe 3).

4 Move to the Conditions tab and set the Mass Flow as 100000 kg/hr.




Fig 3.21

5 On the Composition tab, specify the Mol. Wt. to be 30.

Note: The composition will be calculated as soon as you tab away from theMol. Wt. field.



Fig 3.22

Note: The Mole Fractions are automatically estimated from the MolecularWeight. Because HC is selected, only hydrocarbon components will be used tomatch the Molecular Weight.

6 Click OK to close the Control Valve Editor for Source 3.

7 Repeat Step 2 to add a new source. Again select Control Valve and theControl Valve Editor will be displayed.

8 Name the new source as Source 4.

9 Select Tail Pipe 4 in the Outlet field and set connection to be atUpstream (of Tail Pipe 4).




Fig 3.23

10 Repeat 4-6 to add all the information required by the scenario. SpecifyMole Wt. to be 35 on the Composition tab.

11 Click OK to close the Control Valve Editor.

The Node Manager will now appear as follows:



Fig 3.24

12 Close the Node Manager by clicking Close.

13 Select Inputs | Sources from the Views menu on the Navigation Pane.

The Sources data sheet for the Default Scenario will be displayed:

Fig 3.25

14 You must now add the source data for the four scenarios.

15 Select the scenarios from the Scenario Selector in the Run group on theHome tab. Any open data views will display data for the selected

scenario.

Make the following changes to the flowrates in all scenarios:

Scenarios Source 1(kg/hr)

Source 2(kg/hr)

Source 3(kg/hr)

Source 4(kg/hr)

Source 1 Only 100000 0 0 0

Source 2 Only 0 100000 0 0




Scenarios Source 1(kg/hr)

Source 2(kg/hr)

Source 3(kg/hr)

Source 4(kg/hr)

Source 3 Only 0 0 100000 0

Source 4 Only 0 0 0 100000

For each scenario, ensure that the sources which have a flowrate of 0 are

ignored (i.e. select the Ignore check box for the source).

Note: You can also add the single source scenarios by selecting the Add

Single Source Scenarios tool from Source Tools in Tools group on the

Home tab.

Sizing the NetworkYou have now entered all the model data and can now make the sizing

calculations. You will need to set the calculation options before starting the

calculations.

1 Select Options in the Run group on the Home tab. The Calculation

Options Editor will be displayed:



Fig 3.26

2 For the first calculation of this example ensure that the following optionsare set:

On the General tab, Calculation Mode should be set to Rating, EnableHeat Transfer check box should be cleared, Include Kinetic Energycheck box should be cleared, Ignore Source to Pipe Pressure Loss in

Design Mode should be selected.




On the Scenarios tab, the Calculate box should be set to CurrentScenario.

On the Methods tab, the VLE Method should be set to CompressibleGas, the Enthalpy Method to Ideal Gas and all the Pressure Dropmethods to Isothermal Gas.

3 Click OK to close the Calculation Options Editor. Ensure that the

Default Scenario is selected using the Scenario Selector on the Hometab.

You can now start the calculations.

4 Click Run in the Run group.

Fig 3.27

Once the calculations are complete you can review the results.

5 Select Results | Messages from the Views pane on the Navigation

Pane. The Messages sheet will be displayed.

Fig 3.28

The above view contains general information and warning messagesregarding the calculations. In this case the mach number exceeds thedesign value of 0.5 for Tail Pipe 3, which was defined for each scenario.

It also shows both upstream and downstream pipe segment mach number

for each violation. It is due to smaller pipe segments causing very highfluid velocities across the pipe segment.

At this point, it is a good idea to save your case before doing detail

design.

6 Click the aspenONE Button on the upper left corner of the applicationwindow, and then select Save As from the Application Menu that is

displayed. Save the file as Getting Started 2 Rating.fnwx.

Design Calculations1 We will now use Aspen Flare System Analyzer's design capabilities to

redesign the network to resolve the mach number problem we have

identified in the rating calculation we have just completed.



Use the Calculation Mode selector in the Run group on the Home tab of the Ribbon to change the calculation mode to Debottleneck. This

calculation mode will redesign the flare system to meet our definedsystem limits without reducing the current sizes of any pipes.

2 Click the Run icon on the Ribbon.

After the calculation has been completed, you can review the new results.

Fig 3.29

3 Select Results | Messages from the Views pane, and then select the

Sizing tab to see a list of changes that Aspen Flare System Analyzer has

made to the network.4 Select Results | Pressure/Flow Summary.

The Pressure/Flow Summary data sheet will be displayed.

Fig 3.30

Notice that the upstream and downstream mach numbers are now withinthe design specification for the given scenario. You can use the bottomscroll bar to move across the columns.

We now have a flare system that is designed correctly for the Default

Scenario where all sources are relieving but we have not yet checkedthat it is adequate for all of the scenarios. To do this we will do a Ratingcalculation for all of the scenarios.




5 Open the Calculation Options Editor by clicking Options in the Rungroup on the Home tab. Set the Calculation Mode to Rating on the

General tab. On the Scenarios tab, set the Calculate option to AllScenarios. After closing the Calculation Options Editor, click the Runicon to run the rating check.

6 When the calculations have finished, select Results | Messages from the

Views pane. Click the Problems tab where any violations of our systemdesign limits will be displayed. You will see that Aspen Flare System

Analyzer has detected a violation of the mach number limits for the tailpipes in the single source scenarios.

Fig 3.31

The reason for this is that the lower back pressure in the system whenonly a single source is relieving means that the gas density is reduced

resulting in higher velocities.

7 To fix this problem with our design we will re-run the Debottleneckcalculations for all the scenarios. Use the Calculation Mode selector on

the Ribbon to change the calculation mode to Debottleneck and then

click the Run icon.

8 When completed, review the Problems tab of the Messages view to

confirm that the flare system now meets all our design limits in allscenarios. The Sizing tab will show which pipe sizes have been increased.



Fig 3.32

Note: We could have run the Debottleneck calculations for all scenarios

immediately after our first rating calculation and obtained the same results.While this might have been faster, we have obtained a better understanding

of which scenarios have caused changes to pipe sizes by doing ourcalculations in stages.

9 Select Results | Pressure/Flow Summary from the Views pane on the

Navigation Pane.

The Pressure/Flow Summary will be displayed.

Fig 3.33

Notice that the upstream and downstream mach numbers are now withinthe design specification for the given scenario. You can use the bottomscroll bar to move across the columns.



10 Click the aspenONE Button on the upper left corner of the application

window, and then select Save As from the Application Menu to save the

case as a new file.

11 Enter the new file name as Getting Started 2 Design.fnwx in the All

Files dialog box and click Save.

aspen flaresys analyzer v8 start

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