Aspen Flare System Analyzer Getting Started Guide

Transcription

Aspen Flare System Analyzer
Getting Started Guide
Version Number: V7.3
March 2011
Copyright (c) 1981-2011 by Aspen Technology, Inc. All rights reserved.
Aspen Flare System Analyzer, Aspen Flarenet, and the aspen leaf logo are trademarks or registered
trademarks of Aspen Technology, Inc., Burlington, MA. All other brand and product names are
trademarks 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
license agreement. Users are solely responsible for the proper use of the software and the
application of the results obtained.
Although AspenTech has tested the software and reviewed the documentation, the sole
warranty for the software may be found in the applicable license agreement between
AspenTech and the user. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER
EXPRESSED OR IMPLIED, WITH RESPECT TO THIS DOCUMENTATION, ITS QUALITY,
PERFORMANCE, MERCHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE.
Aspen Technology, Inc.
200 Wheeler Road
Burlington, MA 01803-5501
USA
Phone: (781) 221-6400
Toll free: (888) 996-7001
Website http://www.aspentech.com
Contents
1 Introduction .........................................................................................................1
About this document.........................................................................................1
Audience .........................................................................................................1
Related Documentation .....................................................................................1
Technical Support ............................................................................................1
2 Building and Running a Model ..............................................................................3
Overview.........................................................................................................3
Data Requirements...........................................................................................4
Pipe Segment Data.................................................................................4
Relief Source Data..................................................................................5
System Design Constraints......................................................................6
Starting Aspen Flare System Analyzer.................................................................6
Starting a New Model........................................................................................7
Saving the Model ........................................................................................... 11
Building the Pipe Network ............................................................................... 11
Starting the Pipe Network ..................................................................... 11
Completing the Pipe Network ................................................................. 15
Defining the Scenarios .................................................................................... 25
Defining the Sources ...................................................................................... 32
Rating the Network ........................................................................................ 44
Printing Data and Results ................................................................................ 47
3 Developing the Model .........................................................................................49
Overview....................................................................................................... 49
Data Requirements......................................................................................... 50
Pipe Segment Data............................................................................... 50
Relief Source Data................................................................................ 51
System Design Constraints.................................................................... 53
Opening the Old Model.................................................................................... 53
Updating the Model ........................................................................................ 54
Defining the Scenarios .................................................................................... 63
Defining the Sources ...................................................................................... 67
Sizing the Network ............................................................................... 75
Design Calculations ........................................................................................ 78
Contents
i
1 Introduction
This section provides information on the following topics:

About this Document

Audience

Related Documentation

Technical Support
About this document
The guide provides step by step instructions to the most commonly used
features within Aspen Flare System Analyzer (previously named Aspen
Flarenet).
Audience
This guide is intended for process and process systems engineers.
Related Documentation
Title
Content
Aspen Flare System Analyzer
Reference Manual
Reference Manual for Using Aspen
Flare System Analyzer
Technical Support
AspenTech customers with a valid license and software maintenance
agreement can register to access the online AspenTech Support Center at:
http://support.aspentech.com
This Web support site allows you to:

1 Introduction
Access current product documentation
1

Search for tech tips, solutions and frequently asked questions (FAQs)

Search for and download application examples

Search for and download service packs and product updates

Submit and track technical issues

Send suggestions

Report product defects

Review lists of known deficiencies and defects
Registered users can also subscribe to our Technical Support e-Bulletins.
These e-Bulletins are used to alert users to important technical support
information such as:

Technical advisories

Product updates and releases
Customer support is also available by phone, fax, and email. The most up-todate contact information is available at the AspenTech Support Center at
http://support.aspentech.com.
2
1 Introduction
2 Building and Running a
Model

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
Overview
This 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 Flare
System 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
3
Data Requirements
Before you
u 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 th
the
e liquid knockout drum is
modeled. You should initially size a net
network
work using vapor phase methods.
Pipe Segment Data
Data
Description
Connectivity
You would normally have prepared a system sketch that
defines the nodes to which the pipe segments are connected.
conne
Length and fittings
loss coefficients for
each pipe segment
These will be based upon either a preliminary or detailed
isometric drawing of the piping.
Diameter and pipe
schedule for each
pipe segment
If you are rating an existing network, these will
w normally be
taken from the flare system P&ID. If you are sizing a new
flare system, the pipe diameters that you define are relatively
unimportant since they will be overwritten by the sizing
algorithms. It is recommended that reasonable diameters be
defined,
fined, so that the sizing algorithm initializes to a condition
that will give faster convergence.
The following diagram shows the connectivity of the system that you will be
designing in this example.
Fig 2.1
4
The piping in the network diagram is detailed in the following table:
Item
Length
(m)
Internal
Diameter
(mm)
Wall
Thickness
(mm)
Flare Tip
Fittings
Loss
Elevation
Change
(m)
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 zero
length 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 pipe
enlargement and junction losses for the connection to the upstream pipe
which will automatically be calculated.
Relief Source Data
The following data must be specified for the sources:
Data
Description
Flow and
Composition
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. Flow refers to the quantity of fluid that the
source valve must pass as a consequence of the plant upset
condition. Rated Flow refers to the quantity of fluid that the
source valve will pass due to its physical construction. Rated
Flow must always be greater than or equal to Flow.
Maximum Allowable
Back Pressure
(MABP)
This is the maximum pressure that can exist at the outlet of
the device (source) without affecting its capacity.
Downstream
temperature
This temperature is used as the pressure independent
temperature at which the source enters the network. This
temperature is used when ideal gas enthalpies are used to
calculate the heat balance, or as an initial guess when any
other enthalpy method is used.
Upstream pressure
and temperature
These are only used if Ideal Gas enthalpies are not used for
the heat balance. These may vary for each scenario that you
are evaluating. With relief valves, the flowing pressure should
be used.
Discharge flange
size
This will normally be determined from the relief valve sizing
calculations. If this value is unknown then the field should be
left empty to ignore the pressure change from the valve to
the downstream pipe due to the swage.
In this example, you will consider three scenarios that represent one fire case
and two single blocked discharge cases. The following tables define the source
data for each scenario.
Default Source Data
5
Source
Name
Flowrate
(kg/hr)
Flange
Size
(mm)
Mol.
Wt.
US
Temp
(C)
DS
Temp
(C)
US Pres.
(bar
abs)
MABP
(bar
abs)
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
Source
Name
Flowrate
(kg/hr)
Flange
Size
(mm)
Mol.
Wt.
US
Temp
(C)
DS
Temp
(C)
US Pres.
(bar
abs)
MABP
(bar
abs)
Source 1
100000
300
20
15
15
10
5.0
Source 2
0
300
25
15
15
10
5.0
Mol.
Wt.
US
Temp
(C)
DS
Temp
(C)
US Pres.
(bar
abs)
MABP
(bar
abs)
Source 2 Only Data
Source
Name
Flowrate
(kg/hr)
Flange
Size
(mm)
Source 1
0
300
20
15
15
10
5.0
Source 2
100000
300
25
15
15
10
5.0
System Design Constraints
In this case, the following data is used for both scenarios:

Maximum allowable mach number - 0.50 for both main headers and
tailpipes.

Maximum allowable noise – 100 dB for both main headers and tailpipes.
Starting Aspen Flare System
Analyzer
The installation process creates a short-cut to Aspen Flare System Analyzer in
the 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 Started
case, 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:
6
1
Click the aspenONE Button which is on the upper left corner of the
application window
window; then select Preferences from the Application Menu.
The Preferences Editor is displayed.
2
The current unit set is shown in the Units box.. The default unit set is
Metric,, which will be used for this exam
example.
3
Confirm that the Edit Objects on Add check box is selected.
selected This option
will open the object editor view each time a new object is added.
4
Click OK to close the Preferences Editor.
Starting
arting a New Model
To 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,
Code Project, and
Description fields, and then click OK.
The Component Manager is displayed.
7
Fig 2.2
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 are
typing, the Available components list
st will be filtered out to show only
the matching components.
3
Double-click Methane in the Available components list. Methane will
now 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.
8
Fig 2.3
4
Repeat the previous step with Ethane and Propane.. As an alternative
method, you may scroll through the Available components list until you
see the desired component. Highlight the component by clicking it,
it and
then click Add to place it in the Selected components list.
Note: Notice that now all the required components are shown in the
Selected components
omponents list, indicating that they
ey have been installed in the
case.
The Component Manager will now appear as follows:
9
Fig 2.4
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
mponents from the list. The Components data view will be
displayed:
Fig 2.5
10
2 Building
uilding and Running a Model
Note: You can use the horizontal scroll bar at the bottom of the sheet to view
all of the component properties.
Saving the Model
It 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 Network
Since all scenarios have a common pipe network, you should first build the
pipe network model via the Process Flowsheet.
Starting the Pipe Network
1
Click Process Flowsheet in Views group on the Home tab of the
Ribbon. The Process Flowsheet will be displayed, and the Process
Flowsheet 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.
11
Fig 2.6
At this point the flowsheet should be blank, since we have not added a single
object 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 Process
Flowsheet.
Fig 2.7
12

Objects can also be added via the Pipe Manager and the Node
Manager.. 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 in
the Name field. Click OK to close the Pipe Editor.
3
Next, add a Flare Tip
Tip. Drag the Flare Tip icon on the Palette to the
Process Flowsheet
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
lowsheet:
Fig 2.8
By default the Flare Tip has been named as FlareTip1,, which can be changed
to a more appropriate name as follows:
4
Click in the Name field on the Connections tab of the Flare Tip Editor.
Editor
5
Delete the default name an
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 be
simulated
imulated as a flare stack
stack, and it is attached to the Flare Tip.
Tip
6
Select Stack from the list in the Upstream node field.
7
In the At field
field, select Downstream as the pipe end connected to the
Flare Tip.
13
In order to complete the input on the Flare Tip Editor,, you need to
specify 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 coeff
coefficient
icient we are defining will calculate the pressure
loss in the Flare T
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 2.9
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
P
Flowsheet.. These may be drawn one on top of the other so you should
manually arrange them by clicking and dragging the object icons.
10 Open the Stack Object Editor by double-clicking
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.
14
Fig 2.10
13 On the Methods tab, confirm that Vertical Pipe and VLE Method are set
as Model Default
Default.
In this example, every pipe segment uses the default models which are
specified on the Methods tab of the Calculation Options Editor.
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
Manager.
Completing the Pipe Network
1
Click Pipes in the Build group on the Home tab of the Ribbon.
Ribbon The Pipe
Manager will be displayed.
15
Fig 2.11
2
Click Add.
A new pipe will be added to the list. Click Edit.
The Pipe Editor will be displayed.
16
Fig 2.12
3
Change the na
name to Header 3.
4
Move to the Dimensions tab and enter the following data in the
appropriate fields:
Field
Value
Length (m)
50
Nominal Diameter (inch)
36
Pipe Schedule
40
5
Click OK to clo
close the Pipe Editor.
6
Close the Pipe Manager by clicking Close.
You need to attach Header 3 with Stack using a node. Aspen Flare
System Analyzer allows you to choose between a variety of nodes, since
you need a simple connec
connection between the two pipes, a Connector node
will be used.
7
On the Palette
Palette, click the Connector icon and drag it to the Process
Flowsheet.
This will open the Connector Editor.
17
Fig 2.13
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.
18
2 Building
Fig 2.14
Notice that by default the Angle has a value of 90 deg and the Fitting
loss method
ethod 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.
Ribbon The
Node Manager will be displayed.
19
Fig 2.15
14 Click Add and Select Tee from the list. A new Tee will be added.
Click Edit.
The Tee Editor will be displayed.
20
Fig 2.16
15 Change the name to Tee 1 in the Name field.
16 Specify the Downstream node connection to be Header 3 and select
Upstream from the At field.
17 Move to the Calculations tab and verify that the Fitting loss methods
setting is Miller
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 section
of Tee 1 using the Pipe Manager.
20 Open the Pipe Manager by clicking Pipes in the Build group.
group
21
Fig 2.17
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 Branch
in the At field
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 pipe
which is a tail pipe tto
o a control valve source, the rated flow and actual flow
will be the same so the setting of this option will have no effect.
22
Fig 2.18
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
2 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,
valve
set the Tailpipe option to Yes.
30 Set Nominal Diameter as 18 inch from the list.
23
Fig 2.19
31 Click OK to close the Pipe Editor.
32 Close the Pipe Manager by clicking Close.
In the Navigation Pane area which is docked to the left side of the Process
Flowsheet, select
elect Inputs | Pipes on the Views pane.
The Pipes data sheet displays the data for all of the pipe segments:
Fig 2.20
24
You could
ld also check the P
Process Flowsheet to ensure that the proper
connections have been made. A portion of the P
Process Flowsheet
lowsheet is displayed
below:
Fig 2.21
Defining the Scenarios
You 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.
Ribbon
The Scenario Manager will be displayed.
25
Fig 2.22
2
26
Double-click Default Scenario in the Scenarios list.
2 Building
Fig 2.23
3
The Scenario Editor will be displayed.
isplayed. Alternatively, you could select
Default Scenario in the Scenarios list, and then click Edit.
Edit
Update the header Mach Number limit on the Constraints tab for the
Default Scenario as shown below, then click OK to close the Scenario
Editor and return to the Scenario Manager.
27
Fig 2.24
Now we should add the data for the Source 1 Only scenario.
4
28
Make sure that Default Scenario is highlighted in the Scenarios list on
the Scenario Manager
Manager. Click Clone. A new scenario will be added to the
list as shown below.
Fig 2.25
5
Click Edit to open the Scenario Editor for the new scenario.
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.
29
Fig 2.26
30
7
Click OK to close the Scenario Editor for Source 1 Only.. Repeat Step 4
to
o add a new scenario.
8
Change the name for the new scenario to Source 2 Only.
Fig 2.27
9
Verify the data for the new scenario on the Constraints tab is the same
as shown below
below.
31
Fig 2.28
10 Click OK to close the Scenario Editor and return to the Scenario
Scenari
Manager,, then click Close to close the Scenario Manager.
Manager
You 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 in
terms of molecular weight, the program preferences must be set to accept
the compositions on this basis.
1
32
Click the aspenONE Button at the upper left corner of the application
window. Select Preferences from the Application Menu that is displayed.
d
The Preferences Editor will be displayed.
Fig 2.29
Ensure that Mol
Molecular Weight is selected in the Composition Basis
field on the Defaults tab.
33
Fig 2.30
2
Click OK to close the Preferences Editor.
Before defining
ng a set of source data, you must select the scenario which
corresponds to this data. You will start by defining the data for the
Default Scenario
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 for
this scenario. This field is regarded as the Scenario Selector.
Selector
You can now add the data corresponding to this scenario for each source.
4
34
Click Nodes in the Build group. The Node Manager will be displayed:
2 Building
Fig 2.31
5
Click Add and select Control Valve from the list that is displayed.
displayed
35
Fig 2.32
Click Edit. The Control Valve Editor will be displayed:
36
Fig 2.33
6
Change the name to Source 1. Select Tail Pipe 1 in the Outlet field and
set connection to be at Upstream (of Tail Pipe 1).
37
Fig 2.34
7
38
Move to the Conditions tab and set the Mass Flow as 100000 kg/hr. In
this example, the inlet pressure and temperature are the same as the
default values
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 have
entered the M
Mol. Wt. and tabbed to the next field, you will notice the
composition will be calculated to give the required Mol. Wt.
39
Fig 2.36
Note: The Mole Fractions are automatically estimated from the Molecular
Weight. Because HC is selected from the list, only hydrocarbon
rocarbon components
will be used to match the Molecular Weight.
9
Click OK to close the Control Valve Editor for Source 1.. Click Add in
the 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
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 at
Upstream (of Tail Pipe 2).
40
Fig 2.37
13 On the Conditions tab, check that the relief valve set pressure or MAWP
is set to the default value of 10 bar which is correct
ect for this source. Select
the 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
k 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 tthe 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.
41
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 to
reflect 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 will
calculate 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:
42
2 Building
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 Process
Flowsheet, 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
ny open data views will now
display data for this scenario.
21 Make the following changes to the flowrates from the Sources data sheet
in the Source 1 Only scenario
cenario (all other information remains the same):

Source 1 - Mass F
Flow 100000 kg/hr, Mol. Wt. 20
43

Source 2 - Mass Flow 0 kg/hr, Mol. Wt. 25
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 following
changes to the Source 2 Only:


Finally reselect the Default Scenario from the Scenario Selector.
Rating the Network
We have now entered all the model data and can now make the sizing
calculations. We will need to set the calculation options before starting the
calculations.
1
44
Click Options in the Run group on the Home tab of the Ribbon. The
Calculation Options Editor will be displayed:
Fig 2.41
2
For this example
example, we are going to use the default methods and settings
defined when Aspen Flare System Analyzer creates a new model. This
includes the fol
following key options:

On the General tab, Calculation Mode should be set to Rating,
Rating Enable
Heat
eat 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.
Scenarios
45

On the Methods tab, the VLE Method should be set to Compressible
Gas, the Enthalpy Method to Ideal Gas and all pressure drop methods
to Isothermal Gas
Gas.
Click OK to close the Calculation Options Editor.
You can now start the calculations.
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.
Pane
The Messages data vi
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.
Pane
The Pressure/Flow Summary will be displayed:
46
Fig 2.44
With the Pressure/Flow Summary sheet open, select each scenario in turn
using the Scenario Selector in the Run group.
Note: In the scenario Source 1 Only,, the mach number problem on Tail
Pipe 1 is automatically highlighted.
7
At this point, save the model using either the Save icon on the Quick
Access Toolbar
Toolbar, or click the aspenONE Button
on at the upper left corner of
the application window then select Save from the Application Menu.
M
Printing Data and Results
To print data and results:
1
Click the aspenONE Button, and then s
select Print from the Application
Menu. 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 the
scenarios instead of jus
justt the current scenario. If you want to print to a file,
click Text,, then specify the file location and File name in the Save dialog
box.
3
Click Preview to preview the layout in the Print Preview window before
anything is pr
printed.
47
48
3 Developing the Model

Overview

Data Requirements

Opening the Old Model

Updating the Model



Sizing the Network

Design Calculations
Overview
In this chapter of the Getting Started tutorial you will change the network
designed 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 and
results will be viewed both in textual and graphical form.
49
Data Requirements
Before you can start to upgrade a computer model of the existing flare header
system, you must first define al
alll the data that will determine your system.
Pipe Segment Data
Data
Description
Connectivity
You would normally have prepared a system sketch that
defines the nodes to which the new pipe segments are
connected.
Length and fittings
loss coefficients for
new
w pipe segment
These will be based upon either a preliminary or detailed
isometric drawing of the piping.
Diameter and pipe
schedule for each
pipe segment
If you are rating an existing network, these will normally be
taken from the flare system P&ID. If you are sizing a new
flare system, the pipe diameters that you define are
relatively unimportant since they will be overwritten by the
sizing algorithms. It is recommended that reasonable
diameters be defined, so that the sizing algorithm initialises
to 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 drum
is modelled. You should initially size a network using vapo
vapour
ur 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.
Segment
Name
50
Length
(m)
Nominal
Diameter (inch)
Schedule
Fittings
Loss
Elevation
Change (m)
Stack
100
36
40
0
100
Header 1
50
28
30
0
0
3 Developing
Developin the Model
Segment
Name
Length
(m)
Nominal
Diameter (inch)
Schedule
Fittings
Loss
Elevation
Change (m)
Header 2
50
28
30
0
0
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
0
Tail 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 Data
The following data must be specified for the sources:
Data
Description
Flow and
Composition
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 the
quantity of fluid that the source valve will pass due to its
physical construction. Rated flow must always be greater
than or equal to flow.
Maximum Allowable
Back Pressure
(MABP)
This is the maximum pressure that can exist at the outlet of
the device (source) without affecting its capacity.
Downstream
Temperature
This temperature is used as the pressure independent
temperature at which the source enters the network. This
temperature is used when ideal gas enthalpies are used to
calculate the heat balance, or as an initial guess when any
other enthalpy method is used.
Upstream Pressure
and Temperature
These are only used if the Ideal Gas enthalpies are not
used for the heat balance. These may vary for each
scenario that you are evaluating. With relief valves, the
flowing pressure should be used.
Discharge Flange
Size
This will normally be determined from the relief valve sizing
calculations.
In this example, you will consider five scenarios that represent one fire case
and 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 are
assumed 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.
(bar
abs)
MABP
(bar
abs)
Source 1
100000
20
15
15
10
5.0
51
Source
Name
Flowrate
(kg/hr)
Mol.
Wt.
US
Temp
(C)
DS
Temp
(C)
US Pres.
(bar
abs)
MABP
(bar
abs)
Source 2
100000
25
15
15
10
5.0
Source 3
100000
30
15
15
10
5.0
Source 4
100000
35
15
15
10
5.0
Source 1 Only Data
Source
Name
Flowrate
(kg/hr)
Mol.
Wt.
US
Temp
(C)
DS
Temp
(C)
US Pres.
(bar
abs)
MABP
(bar
abs)
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
US
Temp
(C)
DS
Temp
(C)
US Pres.
(bar
abs)
MABP
(bar
abs)
Source 2 Only Data
Source
Name
Flowrate
(kg/hr)
Mol.
Wt.
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
Source
Name
Flowrate
(kg/hr)
Mol.
Wt.
US
Temp
(C)
DS
Temp
(C)
US Pres.
(bar
abs)
MABP
(bar
abs)
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
52
Source
Name
Flowrate
(kg/hr)
Mol.
Wt.
US
Temp
(C)
DS
Temp
(C)
US Pres.
(bar
abs)
MABP
(bar
abs)
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 Constraints
In 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 Model
1
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 the
aspenONE Button on the upper left corner of the application window.
window
-orClick the aspenONE B
Button, then click Open from the Application Menu
that is displayed
displayed.
-orPress 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.
53
5
Next, select the file that you created in Chapter 2 from the list,
list and then
click Open.
Updating the Model
You need to add new pipe segments to the existing model, but first you must
delete the connection between Tee 1 and Header 3.. Open the Process
P
Flowsheet and delete the co
connection as follows:
1
Click Toggle Connect/Arrange Mode on the Process Flowsheet tab
on the Ribbon to switch to Connect mode and select the connection
between 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
ee section after Header 3:
3
54
Open the Node Manager by clicking Nodes in the Build group on the
Home tab on the Rib
Ribbon.
Fig 3.4
4
Click Add and select Tee from the list that is displayed. Click Edit.
The Tee Editor will be displayed:
55
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 will
be 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 Method
setting is Miller
Miller.
7
Close the Tee Editor by clicking OK.
8
Click Close to close the Node Manager.
Now, you can
n add two pipe segments to the upstream and branch section
of Tee 3 using the Pipe Manager.
9
56
Open the Pipe Manager by clicking Pipes in the Build group.
group
Fig 3.6
10 Click Add to add a new pi
pipe segment. Click Edit to open the Pipe Editor.
11 Change the default pipe name to Tail Pipe 4.
in the At field
field.
57
Fig 3.7
14 Select Nominal Diameter as 18 inch from the list provided.
provided
15 Click OK to close the Pipe Editor. Repeat Step 10 to add another pipe
segment.
16 Change the default name of the new pipe segment to Header 2.
2
Upstream in the At field.
19 Set Nominal Diameter as 28 inch and Schedule as 30 from the list
provided.
58
Fig 3.8
21 Close the Pipe Manager by clicking Close.
Notice that three new objects have been added to the P
Process
rocess 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
alette icon on
the Process Flowsheet tab on the Ribbon.
23 Click the Tee icon in the Palette window,, drag and drop it to the Process
Flowsheet.
Since the Edit Objects on Add check box is selected, The Tee Editor will
be displayed.
59
Fig 3.9
24 Change the default name to Tee 2.
25 Specify Header 2 as the Downstream node connection and select
Upstream in the At field. On the Calculations tab, verify the Fitting
loss method is Miller.
26 Close the Tee Editor by clicking OK.
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 Edi
Editor, change the default pipe name to Tail Pipe 3.
3
in the At field
field.
60
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.
1
Upstream in the At field.
36 Specify Tee 1 as the Upstream connection and select Downstream in
the At field.
38 Set Nominal Diameter as 28 inch and Schedule as 30.
61
Fig 3.11
Select Inputs | Pipes from the Views menu on the Navigation Pane.
Pane The
Pipes data sheet displays the data for all of the pipe segments:
Fig 3.12
At this point you might want to rea
rearrange
rrange the new items on the Process
P
Flowsheet.. The P
Process Flowsheet should be similar as displayed below:
62
Fig 3.13
You now need to define the data for the new scenarios, the Source 3 Only
and Source 4 Only scenarios. The existing model already contains three
scenarios which you will still be using in this example. To add the new
scenarios:
1
Click Scenario
Scenarios in the Build group on the Home tab on the Ribbon.
Ribbon
The Scenario Manager will be displayed.
63
Fig 3.14
2
64
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 and
Tailpipes groups are 0.5 as shown below:
65
Fig 3.16
66
5
Repeat Step 2 tto add a new scenario. Click Edit.
6
Change the default name for the new scenario to Source 4 Only.
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 Scenario
Manager. Now select Default Scenario and click Current to make this
the working scenario. Click Close to close the Scenario Manager.
Manager
You 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 in
terms of molecular weight, the program preferences must be set to accept
the 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.
67
Fig 3.18
2
68
Click Add and select Control Valve from the list displayed.
displayed
Fig 3.19
Click Edit. The Control Valve Editor will be displayed:
69
Fig 3.20
70
3
Change the default name to Source 3. Select Tail Pipe 3 in the Outlet
field and set connection to be at Upstream (of Tail
il Pipe 3).
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 the
Mol. Wt. field.
71
Fig 3.22
Note: The Mole Fractions are automatically estimated from the Molecular
Weight. Because HC is selected, only hydrocarbon components will be used to
match the Molecular Weight.
72
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 the
Control Valve Editor will be displayed.
8
Name the new
ew source as Source 4.
9
Select Tail Pipe 4 in the Outlet field and set connection to be at
Upstream (of Tail Pipe 4).
Fig 3.23
10 Repeat 4-6 to add all the information required by the scen
scenario.
ario. Specify
Mole 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:
73
Fig 3.24
12 Close the Node Manager by clicking Close.
13 Select Inputs | Sources from the Views menu on the Navigation Pane.
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 the
Home tab.. Any open data views will display data for the selected
scenario.
Make the following changes to the flowrates iin all scenarios:
74
Scenarios
Source 1
(kg/hr)
Source 2
(kg/hr)
Source 3
(kg/hr)
Source 4
(kg/hr)
Source 1 Only
100000
0
0
0
Scenarios
Source 1
(kg/hr)
Source 2
(kg/hr)
Source 3
(kg/hr)
Source 4
(kg/hr)
Source 2 Only
0
100000
0
0
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 Network
You 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:
75
Fig 3.26
76
2
For the first calculation of this example ensure that the following options
are set:

On the General tab, Calculation Mode should be set to Rating,
Rating Enable
Heat Transfer check box should be cleared, Include Kinetic Energy
check 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 Current
Scenario.

On the Methods tab, the VLE Method should be set to Compressible
Gas, the Enthalpy Method to Ideal Gas and all the Pressure Drop
methods to Isothermal Gas
Gas.
3
Click OK to close the Calculation Options Editor. Ensure that the
Default Scenario is selected using the Scenario Selector on the Home
tab.
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.
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 messages
regarding the calculations. In this case the mach number exceeds the
design value
ue 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 high
fluid 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 application
window, and then select Save As from the Application Menu
enu that is
displayed. Save
ave the file as Getting Started 2 Rating.fnwx.
Rating.fnw
77
Design Calculations
1
We will now use Aspen Flare System Analyzer's
's design capabilities to
redesign the network to resolve the mach number problem we have
identified in the rat
rating
ing 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.
Debottleneck This
calculation mode will redesign the flare system to meet our defined
system 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
network.
4
Select Results | Pressure/Flow Summary
Summary.
The Pressure/Flow Summary data sheet will be displayed.
displayed
Fig 3.30
78
Notice that the upstream and downstream mach numbers are now within
the design specification for the given scenario. You can use the bottom
scroll bar to move across the columns.
We now have a flare system that is designed correct
correctly
ly for the Default
Scenario where all sources are relieving but we have not yet checked
that it is adequate for all of the scenarios. To do this we will do a Rating
calculation for all of the scenarios.
5
Open the Calculatio
Calculation Options Editor by clicking Options in the Run
group on the Home tab. Set the Calculation Mode to Rating on the
General tab. On the Scenarios tab, set the Calculate option to All
Scenarios.. After closing the Calculation Options Editor,, click the Run
icon 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 system
design limits will be displayed. You will see that Aspen
n Flare System
Analyzer has detected a violation of the mach number limits for the tail
pipes in the single source scenarios.
Fig 3.31
The reason for this is that the lower back pressure in the system when
only 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
re-run the Debottleneck
calculations 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 complete
completed, review the Problems tab of the Messages view to
confirm that the flare system now meets all our design limits in all
scenarios. The Sizing tab will
ill show which pipe sizes have been increased.
79
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 obtai
obtained
ned a better understanding
of which scenarios have caused changes to pipe sizes by doing our
calculations in stages.
9
Select Results | Pressure/Flow Summary from the Views
View pane on the
Navigation Pane
Pane.
The Pressure/Flow Summ
Summary will be displayed.
Fig 3.33
80
Notice that the upstream and downstream mach numbers are now within
the design specification for the given scenario. You can use the bottom
scroll 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.
81

Aspen Flare System Analyzer Getting Started Guide

Transcription

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