Aspen utilities user guide v7 2

Aspen Utilities
V7.2
User Guide

Version V7.2
July 2010
Copyright (c) 1981 – 2010 by Aspen Technology, Inc. All rights reserved.
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URL: http://www.aspentech.com

Contents
Introducing Aspen Utilities .....................................................................................1
What You Need To Use This Guide......................................................................1
Section Descriptions ...............................................................................2
About This Document .......................................................................................2
Related Documentation.....................................................................................2
Technical Support ............................................................................................3
1 Aspen Utilities Planner User Interface .................................................................5
Starting Aspen Utilities Planner ..........................................................................5
Aspen Utilities Planner Main Window...................................................................5
Flowsheet Window..................................................................................6
Explorer Window....................................................................................6
Message Window....................................................................................6
Optimization Menu .................................................................................6
Initializing Physical Properties ............................................................................6
Creating and Simulating an Aspen Utilities Model .................................................8
Aspen Utilities Model Library....................................................................8
Adding Data to the Blocks .......................................................................8
Running in Simulation Mode ....................................................................8
2 Data Editors .......................................................................................................11
Profiles Editor ................................................................................................ 12
Accessing the Profiles Data Editor........................................................... 14
Editing Demand Profile.......................................................................... 15
Editing Availability Profile ...................................................................... 17
Updating Profiles.................................................................................. 18
Filtering Profile Data ............................................................................. 21
Viewing Profiles.................................................................................... 22
Printing Profiles.................................................................................... 24
Saving and Transferring Profile Data....................................................... 25
Selecting a Case .................................................................................. 26
Editing a Case...................................................................................... 27
Copying a Case .................................................................................... 28
Exporting a Case.................................................................................. 29
Changing the Location of the Databases.................................................. 31
Tariff Editor ................................................................................................... 32
Accessing the Tariff Editor ..................................................................... 33
Adding Contract ................................................................................... 35
Editing a Contract ................................................................................ 36
Deleting a Contract .............................................................................. 37
Adding Tiers ........................................................................................ 38
Editing a Tier ....................................................................................... 39
Contents iii

Entering Tariff Cost Equations................................................................ 40
Deleting a Tier ..................................................................................... 46
Saving and Transferring Tariff Data ........................................................ 47
Printing Contracts and Tiers................................................................... 48
Demand Forecasting Editor.............................................................................. 48
Accessing the Demand Forecasting Editor................................................ 49
Calculating Utility Demands ................................................................... 50
Saving Utility Demands......................................................................... 51
Modifying Demand Equations................................................................. 51
Using the DFE Equation Editor ............................................................... 52
Tips for Creating Equations.................................................................... 62
Adding an Equation .............................................................................. 64
Deleting an Equation ............................................................................ 65
Displaying Equation Variables ................................................................ 66
Using the Variable Filter ........................................................................ 67
Modifying Independent Variables in Equations.......................................... 68
Calculating Utility Demands for Multiple Periods ....................................... 69
3 Optimization Configuration ................................................................................71
Enforcing Hot Standby Requirements................................................................ 71
Configuring Startup/Shutdown Constraints ........................................................ 73
Configuring Load Shedding.............................................................................. 75
Obtaining Marginal Utility Cost ......................................................................... 77
Identifying Optimization Errors ........................................................................ 80
Presolve Error Checking ........................................................................ 81
Error Tracking...................................................................................... 82
Setting up Options for Optimization.................................................................. 85
Multiple Period Run Mode ...................................................................... 85
Settings for Mixed Integer Linear Solver............................................................ 86
Cut Strategy........................................................................................ 86
Cut off Value (Max. Expected Cost) ........................................................ 87
Optimum Gap from Optimality (%)......................................................... 87
Presolve Strategy................................................................................. 87
4 Aspen Utilities On-line Implementation..............................................................89
Calculating Utility Demand Targets ................................................................... 89
Specifying Demands for On-line Optimization .................................................... 91
5 Microsoft Excel Interface....................................................................................93
Installing the Aspen Utilities Planner Add-In ...................................................... 93
Aspen Utilities Excel Menu Items ............................................................ 94
Open Aspen Utilities File........................................................................ 95
Running a Simulation from Excel ...................................................................... 95
Creating a Simulation Links worksheet.................................................... 96
Configuring Blocks and Variables for Input to Aspen Utilities Planner .......... 97
Configuring Blocks and Variables for Retrieval from Aspen Utilities Planner.. 98
Mapping Variable Values to the Excel Flowsheet ..................................... 100
Running Data Reconciliation from Excel........................................................... 101
Accessing Reconciliation Worksheet ...................................................... 102
Configuring Blocks and Variables for Reconciliation................................. 103
Running Optimization from Excel.................................................................... 104
iv Contents

Performing User Specific Tasks before Optimization................................ 105
Producing Optimization Results and Tariff Information from Aspen Utilities 106
Obtaining Results from Multi-Period Optimization ................................... 109
6 Aspen Utilities Planner Reference ....................................................................111
Model Library............................................................................................... 111
List of Models .................................................................................... 112
General Model Structure ..................................................................... 113
Standard Variable Names in Models...................................................... 114
Ports and Streams.............................................................................. 115
Specifying Capacity Limits ................................................................... 115
Feeds ............................................................................................... 116
Demands .......................................................................................... 120
Headers ............................................................................................ 124
Steam Models .................................................................................... 127
Pumps .............................................................................................. 132
Turbines............................................................................................ 137
Heat Exchangers ................................................................................ 142
Multipliers ......................................................................................... 151
Fuel Models ....................................................................................... 154
Emissions.......................................................................................... 169
Templates ......................................................................................... 177
Flowsheet Development ................................................................................ 179
Dealing with Snapshots....................................................................... 179
Variable Specification – Fixed and Free ................................................. 179
Appendix 1 – Configuring the Demand Forecasting Editor...................................181
Before you Start .......................................................................................... 183
Units of Measure .......................................................................................... 185
Configuring General Information .................................................................... 185
EquationTypes ................................................................................... 185
Operators.......................................................................................... 186
Config............................................................................................... 186
PeriodSet .......................................................................................... 186
Period............................................................................................... 186
GeneralInput ..................................................................................... 187
Configuring Production Parameters................................................................. 187
DemandForecasting Input ................................................................... 187
XinVal............................................................................................... 189
Configuring Modes........................................................................................ 190
TblModes .......................................................................................... 190
TblModeValues................................................................................... 191
PeriodModes ...................................................................................... 191
Configuring Calculations................................................................................ 192
tblEquationDefinition .......................................................................... 192
CalcVars ........................................................................................... 193
Configuring Demand Calculations ................................................................... 195
DemandCalcsEquations ....................................................................... 195
DemandCalcs..................................................................................... 195
Contents v

Index ..................................................................................................................197
vi Contents

Introducing Aspen Utilities
In this document Aspen Utilities is used as a generic term to refer to both
Aspen Utilities On-Line Optimizer (Utilities Optimizer), formerly known as
Aspen Utilities Operations, and Aspen Utilities Planner.
Aspen Utilities V7.2 is an equation-oriented tool for the simulation and
optimization of Utility Systems (Fuel, Steam and Power), specially designed to
address all the business processes related to the operation and management
of utility systems.
It can be used to address all the key issues in the purchase, supply and usage
of fuel, steam and power within environmental constraints, and provides a
single tool to optimize energy business processes and substantially improve
financial performance.
Aspen Utilities is based on Aspen Custom Modeler. The software is supplied
with a library of unit operations associated with utility systems. You can also
write your own unit operation models and add these to the library.
Aspen Utilities uses a Mixed Integer Linear Programming (MILP) solver for
optimization.
What You Need To Use This
Guide
To use this guide, you need Aspen Utilities Planner™ installed on PC or PC file
server running Windows 2000 or Windows XP. For information on how to do
this, read the Installation Guide supplied with the product, or contact your
system administrator.
Introducing Aspen Utilities 1

Section Descriptions
This guide contains the following sections:
Introduction  a brief overview of the guide and a list of related
documentation.
Section 1 Aspen Utilities Planner User Interface  an overview of the
application software and how to create an Aspen Utilities model.
Section 2 Data Editors – Detailed information on inputting data into Aspen
Utilities – utility demands, equipment availability, tariff information, and
utility demand forecasting.
Section 3 Optimization Configuration – how to achieve certain optimization
objectives such as hot standby requirements, startup/shutdown constraints,
load shedding, and others. Also how to diagnose optimization problems.
Section 4 Aspen Utilities On-line Implementation – an overview of using
Aspen Utilities Planner with Aspen Online to get data from the plant data
historian and run calculations.
Section 5 Microsoft Excel Interface  how to run Aspen Utilities and view
results from Microsoft Excel and the necessary prerequisites.
Section 6 Aspen Utilities Reference  detailed information covering the models
used in Aspen Utilities and some ideas on flowsheet development.
Appendix 1 Configuring the Demand Forecasting Editor  detailed information
about the demand forecasting application; a subset of tables within the
demand database. These need to be configured following a certain
convention.
Glossary  an explanation of terms used throughout this guide.
About This Document
This guide is suitable for Aspen Utilities Planner V7.2 users of all levels of
experience, from new user to power-user.
For details of basic workflow, refer to the associated Getting Started guide or
the Getting Started topics in the on-line help.
Related Documentation
In addition to this document and the on-line Help system supplied with Aspen
Utilities, the following documents are provided in PDF format to help users
install, learn and use Aspen Utilities.
Title Content
Aspen Engineering What’s New and Aspen Information about new features and
2 Introducing Aspen Utilities

Engineering Known Issues known issues and workarounds.
Aspen Engineering Installation Guide and
SLM Installation and Reference Guide
Full installation requirements and
procedures required to install, verify
license and run Aspen Utilities.
Aspen Utilities Getting Started Guide Tutorials designed to train first-time
users in the main functionality and
features of Aspen Utilities.
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:
 Access current product documentation
 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-to-date
contact information is available at the AspenTech Support Center at
http://support.aspentech.com.
Introducing Aspen Utilities 3

1 Aspen Utilities Planner
User Interface
Starting Aspen Utilities Planner
To start Aspen Utilities Planner:
1 Click Start, and then select All Programs.
2 Point to AspenTech | Process Modeling V7.2, | Aspen Utilities
Planner, and then click Aspen Utilities Planner to launch the
application with a new flowsheet file already loaded.
3 To open an existing simulation, click File | Open.
4 In the Open dialog box, use the Look in list box to locate the directory
where the file is stored, select the file you want to open, and click Open.
Aspen Utilities Planner Main
Window
When you start Aspen Utilities Planner, the main window appears:
1 Aspen Utilities Planner User Interface 5

Optimization Menu
All Items Pane
Contents Pane
Flowsheet Window
Message Window
Flowsheet Window
The flowsheet window is where you build the flowsheet.
Explorer Window
The Explorer Window contains the All Items pane and the Contents pane.
Message Window
The message window displays all messages from Simulation to Optimization.
Optimization Menu
These menu items are used to edit/set the input for optimization – to launch
the Profiles and Tariff Editors, to make optimization settings, and to start an
optimization run.
Initializing Physical Properties
When starting a new Aspen Utilities model you must initialize the physical
properties:
6 1 Aspen Utilities Planner User Interface

1 Click on Component Lists in the Explorer pane.
2 Double-click on Default in the Contents pane. Please Confirm This
Operation dialog box is generated. Click Yes.
3 Physical Properties Configuration dialog box appears, allowing you to
set the physical properties.
o Use Aspen property system – allows you to configure using
embedded Aspen properties.
Click Use Properties definition file. Click Browse and use the Look
In list box to locate the directory where the file AspenUtilities.appdf
is stored. This is stored in the Examples subdirectory of the Aspen
Utilities installation.
Note: The default location of AspenUtilities.appdf is: installation
driveProgram FilesAspenTechAspen Utilities Planner
V7.2Examples.
The other two options: Import Aspen Properties file and Edit using
Aspen Properties are used to change the water physical property
methods or to add components for some custom reason.
o Use custom properties – allows you to use custom physical
properties. You can build a component set.
o Don’t use properties – allows properties not to be used.
4 Click OK when you have located the file.
5 If you select AspenUtilites.appdf, a Build Component List form is
loaded. This has a single component, H2O in the left hand pane. Use the
arrows in the center of the form to move the component to the right hand
pane. Click OK.

Creating and Simulating an
Aspen Utilities Model
Aspen Utilities Model Library
All unit operation and stream models are located in the Utilities Library. This
can be accessed from the All Items pane in the Explorer window.
To select a model or stream:
1 In the tree view in the All Items pane, expand the Utilities subfolder
under the Libraries folder, you can select all utilities models and streams
from Stream Type subfolder and Utility_Models subfolder.
2 Drag the model or stream onto the flowsheet window.
3 All of the functionality of Aspen Custom Modeler is available within Aspen
Utilities Planner. You can rename blocks and streams, and resize, rotate,
and flip blocks. Click on the block and right click to allow access to all of
these functions.
Adding Data to the Blocks
Data input for the various blocks is done with forms. Double-clicking on a
block loads a Summary form which contains most of the variables you want
to access. Other forms can be accessed by choosing the block, right clicking,
then choosing Forms in the context menu.
All blocks have the following forms:
 AllVariables – contains all of the variables within the block.
 Summary – contains a selection of variables that you may want to
specify or view.
 Optimization_Limits – allows you to specify hard constraints for the
item of equipment, for example, minimum steam generation capacity or
maximum power generation, etc.
Blocks may have additional forms, for example to add efficiency curves to the
block.
Running in Simulation Mode
When the flowsheet is built, it can be run in Simulation Mode provided the
model is square (i.e., the number of equations defined in the model is equal
to the number of Free variables).

…….
A simulation can be started by clicking Simulation Run on the tool bar or
from the Run menu.

2 Data Editors
There are three basic types of information input into Aspen Utilities: utility
demands, equipment availabilities, and utility tariffs. Utility demands are the
amount of each utility (e.g., HP Steam, LP Steam, etc.) that must be supplied
by the utility system. Equipment availabilities define the availability of utility
system equipment – whether the equipment is available, its minimum and
maximum, etc. These demands and availabilities can be entered for one time
period or multiple time periods. In Aspen Utilities, demands and availabilities
are entered in the Profiles Editor; the utility tariffs are entered in the Tariff
Editor. Both editors are available within the same form. Apart from the above
two editors, Aspen Utilities also has a tool for calculating utility demands from
plant production rates and operating conditions, called Demand Forecasting.
Results from Demand Forecasting can be transferred to the demand profile in
the Profiles Form. The Demand Forecasting Editor, also known as DFE, is now
available within the same form as the Tariff and Profiles editors.
All data is stored in Microsoft Access databases by default, but other
databases – Oracle and SQL Server – are supported. Profile data is stored in
ProfileData.mdb, Tariff data is stored in TariffData.mdb, and Demand
forecasting data is stored in DemandData.mdb. Apart from these three
databases, there is a fourth database used by Aspen Utilities – Interface.mdb
– which is an internal database used by optimization to collect and hold data
from the other databases and store results from an optimization run. The
following diagram highlights the overall relationships between various data
editors and corresponding databases.
2 Data Editors 11

Profiles Editor
The Profiles Editor is used to enter data for utility demands and equipment
availability. Profile data is grouped in cases. Each case contains an equipment
availability profile, a utility demand profile, and a period set. A period set
contains any number of time periods, each with its own start and end time.
The Profiles Editor form is shown here for a case named Case1.
12 2 Data Editors

The Demand Profile for Case1 is displayed with all areas, all equipments, and
all periods:
The demand profile shown above relates to the example.auf flowsheet in the
Aspen Utilities Examples folder.
In general, the demand profile shows the demand for utilities external to the
utility system flowsheet, from the process units. The example above shows
steam demand from the process units as HP Steam Use. Demands are
usually linked to feed or demand blocks in the flowsheet. The availability
profile shows availability and constraints on equipment modeled in the Aspen
Utilities flowsheet. Data for demands and availabilities are entered in the form
of a range – Min and Max. If the value is fixed, enter the same value for the
minimum and maximum.
Before the Profiles Editor can be used it is necessary to configure the profiles
database with data from the Aspen Utilities model that has been developed.
Refer to the Updating Profiles section later in this chapter.
In general, the steps in using the editor are:
1 Open the Profiles Editor.
2 Make the changes required to the demand and availability profiles. Use
Update to add or delete profiles according to the flowsheet changes.
Note: The Update button is only available when the editor is launched
from within Aspen Utilities. It’s not available in the standalone Editor
launched from the Start menu.
3 Click Save to save the data. The running status bar shows the progress. It
displays “Profile data saved successfully” when the save is completed.
2 Data Editors 13

4 Click Commit to send the data to the optimizer. (Specifically, to the
Interface database.)
5 When prompted by a period dialog, select the periods that should have
data sent to the optimizer.
6 Click Apply.
7 Click to close the editor.
Accessing the Profiles Data Editor
You can access the Profiles Editor from the Optimization menu within Aspen
Utilities by clicking on Editors… then clicking Profile on the Aspen Utilities
Planner Data Editors menu bar.
14 2 Data Editors

The following editor appears:
Editing Demand Profile
Before editing demand profiles, you need to have the equipment names and
related port names set up in the profile database tables.
Please refer to the Updating Profiles section for details. In this section, we
assume all the database tables are set up and you are only interested in
editing the existing profiles.
2 Data Editors 15

When the editor starts, it displays the Demand profiles. You can change
between Demand and Availability profiles by selecting the appropriate radio
button as shown below:
You can type in the minimum and maximum values for the selected demand
profiles as well as its unit of measure. The fields for the demand profile are:
 Legend – this is a description of the data.
 Start Time – this is the starting time and date for the period to which the
data relates.
 End Time – this is the ending time and date for the period to which the
data relates.
You cannot alter Legend, Start Time, and End Time with the editor. The time
is setup in the demand database. However, you could change them directly in
the profile database if necessary.
 Min – the minimum value in the range.
 Max – the maximum value in the range.
 Unit – the unit of measure for data entry and display. The default unit of
measure is defined within the profiles database but for any editing session
this can be changed by double clicking on the unit and selecting a new
unit.
 Area – the field used to group the processes in the plant. Area is
particularly useful for a multiplant case, where process units are often
located in different geographical locations (north, south, etc.). Refer to the
Updating Profiles section for how to set areas.
16 2 Data Editors

Editing Availability Profile
You display and edit the equipment availability profile by selecting the View
Availability Profile radio icon. The availability profile shown below relates to
the example.auf flowsheet in the Aspen Utilities Examples directory.
The Availability profile allows you to define equipment availability (on or off)
and set equipment constraints. Usually equipment design constraints are set
within the definition of the block in Aspen Utilities. However, these constraints
can be further refined within the availability profile. For example, a boiler may
be designed to generate a maximum 200 t/h of steam and have a 25%
turndown. Therefore, within the definition of the block in Aspen Utilities the
optimization limits can be set as follows:
 MinStmFlow = 50 ton/hr.
 MaxStmFlow = 200 ton/hr.
However, if for some reason the maximum generation of steam from the
boiler is limited to 150 ton/hr, this can be set as the maximum value. When
optimization is invoked, the more constraining of the limits set in the
availability profile or the optimization limits are taken.
Note: The availability profile has more than one type of data for the same
piece of equipment - availability and range (Minimum and Maximum).
The availability profile has the following data:
 Legend – a description of the data. You cannot change this value within
the editor.
 Start Time – the starting time and date for the period to which the data
relates. You cannot change this value within the editor.
 End Time – the ending time and date for the period to which the data
relates. You cannot change this value within the editor.
 Min Value – the minimum value of the range. If the data item is related
to equipment availability then this box is disabled.
 Max Value – the maximum value of the range. If the data item is related
to equipment availability then the box has a drop down list allowing you to
select the following options:
o Not Available – the item of equipment is not available for use; for
example, it is down for maintenance. In this case the optimizer cannot
switch on the unit even if it is economic to do so.
2 Data Editors 17

o Available – the item of equipment is available for use. The optimizer
can switch it on or off depending upon the economics.
o Must be on – the item of equipment must be used even if it is not
economic to do so. If equipment must be on and it is not economic to
do so, the item of equipment is usually operated at the minimum
setting.
 Unit – the unit of measure for data entry and display. The default unit of
measure is defined within the profiles database but for any editing session
this can be changed by double clicking on the unit and selecting a new
unit.
 Area – The field used to group the processes in the plant. Area is
particularly useful for a multiplant case, where process units are often
located in different geographical locations (north, south, etc.). Refer to the
Updating Profiles section for how to set areas.
If equipment availability is set as Available, the minimum value for all settings
for that piece of equipment should be set to 0 within the availability profile.
This allows the equipment usage to go to zero (not used) during the
optimization.
Updating Profiles
Before using the Editor to edit the demand and availability profiles, the
underlying Profiles database must be set up properly. The database must
contain the equipment and port name associated with the profile, its display
unit of measure, etc. As the flowsheet is developed, new process blocks might
be added to the flowsheet while others might be deleted. It is necessary to
keep the profile database updated with the changing flowsheet. The Update
feature in the Profiles Editor facilitates this and is available when the editor is
launched from within Aspen Utilities.
Note: The Update button is not available in the standalone Editor launched
from the Start Menu.
18 2 Data Editors

When you click Update on the Editor Menu bar, you are first asked to select
the profile that you wish to update:
Select the appropriate choice and click OK. Here we select Demand profile as
an example.
2 Data Editors 19

Select Ports for Demand Profile window appears:
To add a profile, select the equipment and port in the left-most two panes
and then click Add. The newly added profile will be displayed in the Selected
Ports list in the form Equipment*Port.
To remove an existing profile, select it in the Selected Ports list and click
Remove. When you close the form the selected profile is removed from the
grid.
Note: You need to click Save on the Editor Command bar to save your
changes in the Profiles database.
The following list contains brief descriptions of fields shown in the Update
window:
 Blocks – contains all blocks in the current flowsheet.
 Ports – contains all possible profile variables associated with the selected
block.
 Selected Ports – current selected profile variables and those in the
profile database.
 Add/Remove – Add/Remove port to/from the Selected Port column.
 Configure – the Configure new ports window appears when you click
Configure after new ports are added. In this window, you can select the
display unit of measurement and categorize the selected ports into
predefined areas. After clicking OK, the newly added/removed profile on
the grid appears/disappears.
20 2 Data Editors

This window will only appear for newly added profiles and will close upon
completion of last new profile configuration.
Filtering Profile Data
For a large flowsheet, there could be many demand and availability profiles,
in multiple periods. In such cases it may be difficult to locate specific profiles.
The profile filtering feature addresses this issue.
You can filter the profile data by area, equipment, or period.
By Area
Click on the area filter displays a drop-down list with all defined areas listed.
Select an item to view data relating to a specific area or to all areas.
By Equipment
Click on the equipment filter displays a drop-down list with all items of
equipment listed. Select an item to view data relating to a single piece of
equipment or to all equipments.
By Period
Click on the period filter displays a drop-down list with all periods listed.
Select an item to view data relating to a single period or to all periods.
Note: The equipment filter and the period filter can be used together.
2 Data Editors 21

Viewing Profiles
In addition to the equipment view of profile data, you can click on View in the
main command bar in the editor and switch to period view.
Equipment View
22 2 Data Editors

Period View
2 Data Editors 23

Printing Profiles
Demand and equipment availability profiles can be viewed and printed in
HTML format. The Print preview window appears when you click Print on
the Editor Menu bar. This is the HTML view format of the selected profile.
Click Print on the Print preview window, the report will be sent to the
printer. Meanwhile, a Save As dialog box appears which allows you to save
the report.
24 2 Data Editors

Saving and Transferring Profile Data
After changing demand and equipment profiles, save the changes to the
Profiles database by clicking Save on the Command bar.
In order for optimization to use the modified profile data, you also need to
transfer the profile data to the Interface database. This is done by clicking
Commit on the Command bar. Commit also saves the profile data to the
Profiles database:
2 Data Editors 25

Selecting a Case
Each Profiles database can contain many cases, which may represent different
operating scenarios for the utility plant. When the Profiles editor is first
launched, the profile data in the default case is displayed, as shown below:
You can display, edit, and transfer profile data in other cases by selecting a
different case in the drop-down list.
26 2 Data Editors

Editing a Case
Each case contains a set of demand profiles and a set of availability profiles.
The Demand and Availability profiles that comprise a case can be changed
with the Edit Case dialog box shown below. This case editing capability,
along with other case management features, allows you to easily carry out
What-if analyses when multiple operating scenarios exist in the utility plant.
The following dialog box is displayed when you click Edit on the Editor Menu
bar:
 Demand profile – all demand profiles are listed in the drop-down list and
the current demand profile is highlighted.
 Availability profile – all availability profiles are listed in the drop-down
list and the current availability profile is highlighted.
 Select Period Set – all period sets are listed in the drop-down list and
the current period set is highlighted.
2 Data Editors 27

Copying a Case
Copy case is used to copy an entire case to a new case. This is also an easy
way to generate a new case. Clicking Copy in the Editor Menu bar displays
the following dialog box:
Case Frame
 Name – the name for the new case.
 Description – the new case description.
Profile Frame
 Copy Profile (check box) - Indicates that the current demand and
availability profiles, listed here, should be copied to the new case.
 ID - The demand and availability profile ids for the new case.
 Name - The demand and availability profile names for the new case.
 Description - The demand and availability profile descriptions in the new
case.
Period Set Frame
 Copy Period Set (check box) - Indicates that the current period set,
listed here, should be copied to the new case.
 ID - Period set ID for the new case.
 Description - Period set description for the new case.
28 2 Data Editors
Case Frame
Profile frame
Period set
frame

Exporting a Case
Export case is used to Import/Export the case from/to an external source
(database or data source file). The Select database to import/export case
window appears when you click Export on the Editor Menu bar:
Select the correct location in Look in drop down list to find the external data
source file you want to import/export.
2 Data Editors 29

After a source has been selected, the Import/Export Case window displays:
All cases in the current profile database are listed in the left column. All the
cases in the external database are listed in the right column. From here, you
can decide which case or which profile in the case to export or import.
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Changing the Location of the Databases
You can change the location of the Aspen Utilities databases by clicking
Configure on the Editor Menu bar:
Browse to each of the Profile, Tariff, Demand and Interface databases and
click OK.
The Set for all users checkbox is used to set the same database location for
all users. When this is unchecked, only Registry values in
HKEY_CURRENT_USER are set. When this is checked, Registry values in both
HKEY_CURRENT_USER and HKEY_LOCAL_MACHINE are set.
2 Data Editors 31

Tariff Editor
Optimization in Aspen Utilities is all about cost saving on utilities, i.e.,
minimizing the total utility cost during the plant operation. The input cost data
to Aspen Utilities is the price of each purchased or sold utility. The Tariff
editor is used to enter this information. This Tariff data is stored in an Access
database (TariffData.mdb). As in Profiles data, you must transfer the data to
the optimizer before an optimization run takes place.
The tariff structure defined in Aspen Utilities contains two components, the
Contract and the Tier. In the tariff editor, you define a Contract in Contract
Definition Table for each utility purchased or sold. For each contract, you
create one or more tiers to define the actual utility price. In many cases,
utility tariffs vary non-continually with usage or usage rate. To handle these
types of contracts, multiple tiers are used to define various price structures in
a utility contract.
In general, follow below steps to use the Tariff Editor:
1 Open the Tariff editor from the Optimization menu.
2 Make the necessary changes to the contracts and tiers.
3 Click Save to save the data in the Tariffs Database.
4 Click Commit to save the data in the Tariff database and to send the data
to the optimizer.
5 Click Exit to close the editor.
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Accessing the Tariff Editor
The Tariff Editor is accessed from the Optimization menu in Aspen Utilities
Planner by clicking Editors…, then clicking Tariff on the Aspen Utilities
Planner Data Editors Menu bar.
2 Data Editors 33

The following window appears after clicking Tariff:
All contracts are listed in the upper-half of the table, and the tiers of the
selected contract are listed in the lower half of the table. You can add and
delete contracts and tiers by using Add and Delete on the Command bar.
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Adding Contract
When new purchased or sold utilities are introduced into the flowsheet, you
will need to add a new contract. To add a new contract, right click the mouse
somewhere in the top table and select Add contract. Alternatively, you can
click the arrow on Add and select Contract in the drop-down menu:
To edit an existing contract, double-click on a selected field to enter edit
mode.
To delete an existing contract, click on the relevant contract in the contract
definition table, then either right click the mouse and select Delete Contract,
or click the arrow on Delete and select Contract in the drop-down menu.
For each new contract, you need to provide a unique Contract ID. You must
also specify the Block and Port that the utility represents in the flowsheet.
Click on the drop-down list in the Block and Port fields to select blocks and
ports.
The following data is required for defining a contract:
 Contract ID – you must supply a unique name for the contract.
 Block – the name of the block (usually a feed or demand block) in Aspen
Utilities flowsheet which uses or provides the utility in the contract. The
2 Data Editors 35

previous example shows a Block name of FuelFeed, which is a unit
operation in the example file, example.auf.
 Port – a drop-down list from which you select the port in the block that
provides or uses the utility in the contract. The previous example shows a
Port name of FuelOut1, which is a port name in unit operation FuelFeed in
the example file, example.auf.
 Buy/Sell – this allows you to specify whether the utility is bought or sold.
In the previous example the utility is bought.
 Utility Type – a drop-down list from which you select one of three utility
types: Fuel, Electricity, or Steam. In the previous example the utility type
is Fuel.
 Use Forecast – allows you to specify if a forecast is to be used. This is
very important if there are (for example) annual limits associated with the
contract. If ‘Yes’ is selected, additional data is required.
 Used to Date - this input is only enabled if a Forecast is used. You must
enter the amount of utility used from the start of the contract period to
the current date.
 Forecast - this input is only enabled if a Forecast is used. You must enter
a forecast of the amount of utility used between the end of the run period
and the end of the contract period.
 Do Peak – a peak contract is defined as a contract in which the cost is
linked to the peak usage. Select Yes to define a peak contract, No
otherwise.
 Peak Price – enter here the peak cost in the contract, in units of
monetary unit/usage. Valid when Do Peak is Yes.
 Peak Value – specify the peak usage value. For Usage type contracts
(Rate/Usage field), this is the maximum amount of the utility used so far.
 Disabled – a contract can be temporarily disabled so that it will not be
used in the optimization.
 Rate/Usage – you can select how the contract is controlled, on an hourly
basis or on a total usage basis. If the contract is controlled on a total
usage basis, then it is advisable to use a forecast.
 Unit – you can select the unit of measure for data entry and display.
Editing a Contract
Edit mode is entered when you double-click in any grid cell.
36 2 Data Editors

Deleting a Contract
To delete a contract, select a contract in the contract definition table and click
Delete | Contract on the Command bar:
Alternatively, select a contract in the Contract Definition table, right click the
mouse in any cell, and select Delete Contract.
2 Data Editors 37

Adding Tiers
You can add, edit, or delete tiers associated with a particular contract the
same way as for contracts. To see the tiers associated with a particular
contract, click on a Contract ID in the top Contract Definition table.
To add a tier for a contract, click Add on the Editor Menu bar, and then select
Tier from the drop-down menu (or right-click the mouse and click Add tier) a
new row is generated in the Tier Definition table. Alternatively, select a
contract, right click the mouse in any cell of the tier in the Tier Definition
table, and select Add Tier.
The following data is required to complete a tier definition:
 Tier ID – a unique identifier supplied by you.
 Variable Cost – the cost of utility per unit of use. The base unit is the
same unit of measure defined for the related contract. In this case we
would need to add the cost per GJ of fuel.
 Fixed Cost – the fixed cost portion of the contract, if any. Enter 0 if there
is no fixed cost (you cannot leave this field blank).
 Min Rate – the minimum amount of the utility that can be used in an
hour. This field is used only if the contract is controlled by Rate. If the
contract is controlled by usage, enter 0 (you cannot leave this field blank).
If the field is disabled, any entry here is not being used in optimization.
 Max Rate – the maximum amount of the utility that can be used in an
hour. This field is used only if the contract is controlled by Rate. If the
38 2 Data Editors

contract is controlled by usage, enter 0 (you cannot leave this field blank).
If the field is disabled, any entry here is not being used in optimization.
 Min Usage – the minimum amount that can be used within this tier. This
field is active if the contract is controlled by Usage. If the contract is
controlled by rate, enter 0 (you cannot leave this field blank). If the field
is disabled, any entry here is not being used in optimization.
 Max Usage – the maximum amount that can be used within this tier. This
field is used only if the contract is controlled by Usage. If the contract is
controlled by rate, enter 0 (you cannot leave this field blank). If the field
is disabled, any entry here is not being used in optimization.
 Priority – the priority order of the tiers considered in optimization. We
recommended you use integer numbers starting from 1. The lower the
number the higher the priority. For example, the optimizer is set to
maximize the use of a tier with priority 1 before using a tier with priority
2. When two tiers have same priorities the optimizer is allowed to use any
of the two or both.
 Time dependent – if the variable cost of a tier varies with time, select
Yes, if not select No. When Yes is selected, Variable Cost by Period table
appears below the Tier Definition table. Enter the variable cost for each
period.
Editing a Tier
Edit mode is entered when you double-click in any grid cell.
2 Data Editors 39

Entering Tariff Cost Equations
In many cases, the cost for a particular utility can be broken down to several
contributing cost components. For example, electricity cost typically consists
of a fixed standing charge, taxes, a unit price, delivery cost, etc. The fixed
and variable cost for each tier can be calculated by combining these individual
cost components.
In order to do this, you need to input the individual cost components and the
equations that use the cost components, for each tier.
Adding Utility Cost Components
1 Click Costing on the main command bar in the combined editor and the
cost component form is displayed:
2 Enter the name, description, and value for each cost component in the
grid.
Note: The names of the cost components cannot be duplicated. In
addition, the names cannot contain square brackets ([ and ]).
Editing Utility Cost Components
Edit or change data by typing in the cell.
40 2 Data Editors

Deleting Utility Cost Component
Delete a component by selecting the record and pressing the Delete key. A
confirmation dialog is displayed to verify the change.
Note: Deleting a cost component that is referenced in an equation will cause
errors during the equation evaluation. Therefore be careful when deleting cost
components and be sure to remove any references in the Cost Equations.
Saving Utility Cost Components
Click OK to save changes and close the form. Click Cancel to discard changes
and close the form.
2 Data Editors 41

Accessing the Tier Cost Equation Form
Cost equations can be entered for each tier when the individual cost
components have been added. Cost equations can be entered for the fixed
cost, the variable cost, or both.
The cost equation input form can be displayed in two ways:
 Click Equation on the main command bar.
 Right click the mouse in the fixed or variable cost cell in the tier table and
select Cost Equations… from the context menu.
42 2 Data Editors

Adding a Tier Cost Equation
There is a slight difference depending on how the Cost Equation form is
launched. When Equation is clicked the entire table is displayed with no
specific record highlighted. When the Cost Equations… menu item is
selected from a tier cell, the record for this tier is highlighted in the table. If
no cost equation exists, one is automatically added, as shown below.
In this screenshot, the Cost Equation form is launched from Contract Natural
Gas, tier Tier1 and the Variable Cost cell. A new record is added automatically
and you only need to enter the Equation and the optional Notes.
When the equation form is launched by clicking Equation, you need to
manually enter the Contract, Tier, and Type by selecting from the drop-down
lists.
Entering a Tier Cost Equation
When a record is selected in the Cost Equation table, the equation string is
displayed in the Cost Equation = textbox beneath the table. Edit the
equation in the textbox. To display a list of cost components, type an open
square bracket ([) and a dropdown list is displayed containing all cost
component names defined in Tariff cost components form. Scroll to the
desired cost component and select it by pressing the Space bar or by double-clicking
on it in the list.
2 Data Editors 43

Note: The equation cannot be more than 65535 characters. If this becomes a
limitation, Aspen Utilities recommend using shorter cost component names to
reduce the length of the equation string. You can provide a meaningful
description for the cost component in the Notes field; this description is
shown when the cost component is selected.
You can use any functions or mathematical operators that are recognized by
Microsoft Excel since Excel is used to evaluate the equation. When you click
on the Value cell the equation is evaluated and the result will be displayed.
The following screenshots illustrate how to select cost components, their
descriptions, and building an equation:
Typing a left square bracket [ displays a list of all defined cost components.
The text entered in the Notes field is displayed in the tool-tip window.
44 2 Data Editors

Pressing the Space bar or double-clicking on the name in the list substitutes
the name into the equation and closes the bracket.
Editing a Tier Cost Equation
Edit or change equation by typing in the text box.
2 Data Editors 45

Deleting a Tier Cost Equation
Delete a cost equation by selecting the record and pressing the Delete key. A
confirmation dialog is displayed to verify the change.
Saving a Tier Cost Equation
After editing the cost equation in the text box, you can close the Tariff Cost
Equations dialog box directly and the new edited cost equation will be saved
automatically. This also means there is no cancel that discards changes.
Deleting a Tier
To delete an existing tier, select the desired contract in the top table, then
select the desired tier in the Tier Definition table, and click Delete | Tier
from the Command bar. Alternatively, select the tier, right click the mouse in
any cell, and select Delete Tier from the context menu.
46 2 Data Editors

Saving and Transferring Tariff Data
After you add, edit, or delete contracts and tiers, you can save the changes in
the Tariff database by clicking Save on the Command bar.
In order for optimization to use the modified tariff data, you need to transfer
the tariff data to the Interface database. This is done by clicking Commit on
the Command bar. Commit also saves the tariff data to the Tariff database:
2 Data Editors 47

Printing Contracts and Tiers
Like the Profiles editor, the Tariff editor also allows you to view and print the
contracts and tiers in HTML format. The following window is displayed by
clicking Print on the Menu bar:
When you select and click OK, the corresponding report print preview is
displayed. Click Print on the Print preview window, the report will be sent
to the printer and at the same time a Save As dialog box will be loaded which
allows you to save the report.
Demand Forecasting Editor
The Demand Forecasting Editor is used in conjunction with two Access
databases to calculate utility demands from plant production rates. The
equations relating utility demand to production rate are stored in an Access
database, DemandData.mdb. The calculated utility demands are stored in a
second access database, ProfileData.mdb.
The DemandData.mdb file for a specific application must be pre-configured
before the Demand Forecasting Editor can access it. Refer to Appendix 1 –
Configuring the Demand Forecasting Editor for information how to do this.
The discussion here assumes the Demand database has been configured.
In general, follow below steps when using the Demand Forecasting Editor.
1 Click Optimization | Editors… from the Aspen Utilities menu to open the
Demand Forecasting Editor or launch the standalone editor from the Start
menu. Click on DFE in the command bar.
2 Make the changes required to the demand and availability profiles.
3 Click Calc in the Command bar to calculate the utility demands. The
running status bar shows the progress.
4 Click Save to save the data. This saves the utility demands to the Profiles
database (ProfileData.mdb) and updates the production parameter
information in the Demand database (DemandData.mdb).
5 Click to close the editor.
6 At any time you can click on (in the lower right-hand corner) to view a
log file detailing the status of the Demand Forecasting Data and
Calculations.
48 2 Data Editors

Accessing the Demand Forecasting Editor
The Demand Forecasting Editor can be accessed by clicking DFE in the Aspen
Utilities Editor, launched from Start | All Programs | AspenTech | Process
Modeling V7.2 | Aspen Utilities Planner | Editors.
The following editor appears:
2 Data Editors 49

Calculating Utility Demands
1 Enter the following data to calculating utility demands:
o Number of Periods – the number of periods to calculate.
o Start time – the starting time for the first period.
o Start date – the starting date for the first period.
o Period Length – the length of each period in hours.
o Modes – select the mode of operation for the period for each process
unit that has multiple modes of operation, using the drop-down list.
o Inputs – the value of each production parameter for each period
(e.g., production flow rate).
2 Click Calc to calculate the utility demands. The calculated utility demands
can be seen in the lower pane of the window:
50 2 Data Editors

Saving Utility Demands
Click Save to save the calculated utility demands to the Profiles database
(ProfileData.mdb) and to update the production parameter information to the
Demand database (DemandData.mdb).
Modifying Demand Equations
Go to the bottom pane and use the scroll bars to search for the utility demand
you want to change. Click Edit next to the Unit column to see the equation
editor. The equation editor for the utility HP Steam Use is shown here:
2 Data Editors 51

Demand Forecasting Equation Editor Layout
The Equation Editor contains two fields:
 Equation Editor
 Equations Viewer
Equation Editor
The Equation Editor field is for you to edit demand forecasting equations. The
table at the top contains all of the equations that have been defined. When
you click on an equation in the grid, the equation definition is displayed in the
below text box.
The equations with the Demand check box selected at the top table means
they are the equations for utility demand.
In the example above the HP Steam Use equation contains two variables:
[cvY1] and [cvY2]. Variables are contained with square brackets [ ].
Variables can be defined as values (e.g., 5, Mode1, True), or other
equations. Variables that represent equations are displayed in the table at the
top and all other variables are displayed by clicking Variables….
Equations Viewer
You can view the equations defined in this field and evaluate them. Select the
variable you want to see from drop-down list and the equation it represents is
displayed in the text box at the bottom. In this field, you can only check the
equations but cannot edit. In the example above, [cvY1] is selected in the
drop-down list and the equation it represents seen at the bottom. You can
evaluate the equation by clicking Evaluate next to the equation.
Using the DFE Equation Editor
An example will show how to use the DFE Equation Editor. The example will
create the HP Steam Use equation, starting with nothing.
The HP Steam use is given by:
 If the season is winter:
HP Steam Use = 6 + 0.2*X1 + 2*X1^2
Where X1 is the propylene production rate. And if X1 is less than or equal
to zero, it returns 0.
If season is not winter, HP Steam Use = 90 tonnes/hr
 If the Acetic acid mode is Lean:
HP Steam Use = 0
1 Click on Edit next to the unit of measure for HP Steam Use.
The Equation Editor window appears:
52 2 Data Editors

Notice that there is no equation defined for HP Steam Use. The first step is
to create the equation.
2 Click Add Equation… and fill information requested in Add Equation
dialog box:
If you need to set this equation as a utility demand, then select the Set
this equation to be a utility demand check box.
3 Click OK and you return to the Equation editor ready to create the
equation for cvY1:
2 Data Editors 53

The basic equation is given by: 6 + 0.2*X1 + 2*X1^2 where X1 is the
propylene production rate. Because we want this to be evaluated only
when the season is winter we can put an IF statement around the
equation:
IF("[SEASON]"="(SEASON.Winter)",6+0.2*[X1]+2*[X1]^2,0)
Note: In this example, SEASON is case sensitive, The value in the
equation should use the same case as what is displayed in the Variables
table (click Variables… to open). If you use SEASON.WINTER in the
equation, the equation will not work properly.
Also, we want to return 0 if X1 is less than or equal to zero. We can create
a nested IF statement to do this:
IF("[SEASON]"="(SEASON.Winter)",IF([X1]>0,6+0.2*[X1]+2*[X1]^2,
0))
And if season is not winter, the value of HP Steam Use is 90 tonnes/hr. So
the final equation should be:
IF(“[SEASON]”=”(SEASON.Winter)”,IF([X1]>0,6=0.2*[X1]+2*[X1]^2,
0),90)
Begin by typing to the first left square bracket [. When you type the left
bracket, a list is displayed with all of the variables known to DFE:
54 2 Data Editors

4 Scroll down to SEASON and double-click.
The Equation description is shown as a small tool-tip window when a
variable is clicked:
2 Data Editors 55

Notes:
1. Notice that the right bracket is automatically inserted for you.
2. Notice that the [SEASON] is enclosed in double-quotes “” because it
contains text.
5 Continue editing:
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Note: The parentheses ( ) around the value of the text variable:
(SEASON.Winter)
When values are substituted for variables, DFE places parentheses around
the variable contents. For text values the brackets signifying variable
names are inside the double quotes, resulting in the parentheses being
inside the double quotes after substitution. Therefore, you must add
parentheses around all text values being compared.
6 Click Variables… to see the variables defined for DFE. Refer to the
section Displaying Equation Variables for more information.
Finally, complete the equation:
2 Data Editors 57

Here, X1 is the propylene production rate. The variable values substituted
into the equation are those seen by clicking Variables…. Refer to
Displaying Equation Variables for more information.
7 Click Evaluate to evaluate the equation:
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If there is an error, a red exclamation point is displayed. Holding the
mouse pointer over the exclamation point shows the error in a tool-tip
window.
2 Data Editors 59

Note: Not all errors are caught this way. Some equation errors are not
caught until Microsoft Excel is evaluating the equation. In these cases you
will see a large negative number being displayed.
8 You can edit other equations for HP Steam Use in a similar fashion.
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9 Finally, the HP Steam Use is created in the middle text box.
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Note: Newly created equation variables like cvY1 will be displayed
automatically in the drop-down variable list after entering left square
bracket [.
10 Finally, click Evaluate for HP Steam Use to check the equation entered.
11 Click OK to save your data and close the Equation Editor
Tips for Creating Equations
Here are some tips for creating equations:
 Variable substitution and equation evaluation is faster if you enter the
coefficient values directly in the equation, rather than using variables. For
example:
3.1 + 10.22*[X2]
will evaluate faster than
Var_A + Var_B*[X2]
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This will be more noticeable as the number of equations and variables get
larger.
 The maximum length of an equation string is 65535 characters, including
all spaces, brackets, and variable names. If you have a longer equation,
create multiple equation variables, an equation can be made up entirely of
equation variables and that equation can be referenced by a single
variable in another equation. That way, extremely long equation strings
can be created; there is no limit.
2 Data Editors 63

Adding an Equation
To add an equation, first create the equation variable by clicking Add
Equation… and the Add Equation dialog box appears:
Enter the Equation ID and Equation description. The Equation ID becomes the
equation variable name seen in the equation drop-down list in the Equations
Viewer field and drop-down variable list.
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Click OK to return to the equation editor. The new equation is selected and
can be entered in the text box in Equation Editor field:
Note: When adding an arbitrary equation, you must to uncheck the Set this
equation to be a utility demand checkbox. When checked, the system
assumes you are creating an equation that is linked to a utility.
Deleting an Equation
Delete an equation by selecting an equation and clicking Delete Equation….
You will be asked to confirm the deletion.
2 Data Editors 65

Displaying Equation Variables
You can view the variables that have been defined by clicking Variables…:
This table contains variables that come from the Demand and Profiles
databases as well as user-defined variables. User-defined variables include
production rate variable, mode variable and user variable.
To create a user defined variable, click Add…. The Add Variable dialog box
appears:
Notes:
66 2 Data Editors

 Variable names may not contain square brackets [ and ] since these are
used by DFE to enclose variable names.
 Variable values can be changed for any variable but only values for user
variables are saved when you click OK. This allows you to temporarily
change production rates, modes, etc., while evaluating an equation.
 Once created, a variable name and description cannot be edited. You must
delete the variable and recreate it.
Demand Forecasting Variable Location
The DFE variables are located in the following tables in the Demand database,
DemandData.mdb:
Variable Type Demand Database Table
Production rates DemandForecastingInput
Mode variables tblModes
Equation variables tblEquationDefinition
User variables tblUserVariables
Using the Variable Filter
You can shorten the list of variables displayed in the drop-down variable list
by clicking Variable Filter…:
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Check the variables that you want to display in the drop-down variable list
when a left bracket [ is typed in the equation editor.
Modifying Independent Variables in
Equations
With the exception of user variables, the values of independent variables can
only be changed within the Microsoft Access database editor. The default
Demand database, DemandData.mdb, is located in Installation
Drive:Documents and SettingsAll UsersApplication
DataAspenTechAspen Utilities Planner V7.2Example Databases.
Refer to the Changing the location of the databases section earlier in this
chapter for how to change the location.
Click Variables… to display all variables. Find the variable description of
interest and get the Variable name.
Open the appropriate table in the Demand database (refer to Demand
Forecasting Variable Location section), find the variable name, and change its
value.
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Calculating Utility Demands for Multiple
Periods
If you set the number of periods to be higher than 1, the Demand Forecasting
editor shows an additional column of data for each additional period. The
example below shows a 5-period forecast:
The editor displays the additional columns using default values as inputs for
period length, mode values, and production rates. You can edit these inputs
either manually or by copying and pasting data from Microsoft Excel.
2 Data Editors 69

3 Optimization Configuration
This chapter describes how to set your input data to achieve specific types of
optimizations. Topics covered are: enforcing hot standby requirements,
configuring startup/shutdown constraints, configuring load shedding, and
obtaining marginal utility costs.
This chapter also describes how to identify optimization errors and gives tips
on how to fix them. Advanced optimizer settings are also discussed here.
Enforcing Hot Standby
Requirements
To enforce hot standby requirements, it is necessary to indicate which of the
steam generators are to be included within the calculation of hot standby
capacity. This setting is accessed from the Optimization_Settings form for the
block. Right click on the boiler block, for example, and select Forms |
Optimization_Settings from the context menu:
3 Optimization Configuration 71

If the block is to be included in the calculation of hot standby capacity, set
DoSteamReserve to True. The default setting is False.
To enable the hot standby calculations within the optimization:
1 Select Edit Optimization Settings from the Optimization menu in
Aspen Utilities Planner.
2 Check the Enable hot standby calculations check box.
3 The hot standby requirement is also set in this dialog box. This value must
be specified in tonnes/hr.
72 3 Optimization Configuration

4 Run the optimization as usual either from the Microsoft Excel Interface or
from Aspen Utilities Planner.
5 If the hot standby constraint cannot be met, the optimization will still
complete but with a lower hot standby capacity.
Configuring Startup/Shutdown
Constraints
It is possible to set start-up and shut-down times and costs within Aspen
Utilities. When carrying out a multi-period optimization, these values are
taken into account to determine the economic profile for utility generation
and/or purchase over the entire optimization timeframe.
Start-up and shut-down times and costs can be provided for most blocks by
accessing the Optimization_Settings form.
To enable startup and shutdown calculations, set the DoStartStop variable to
True. The default for all blocks is False.
You must then specify:
 StartUpTime – the time taken to start the unit from cold to actually
producing utility.
 StartUpCost – the hourly cost of starting up the unit.
 ShutDownTime – the time taken to shut the unit down. It is assumed
that utility is not generated from the start of the shutdown period to the
end of it.
 ShutdownCost – the hourly cost of shutting down the unit.

To enable the startup/shutdown calculations within the optimization:
1 Select Edit Optimization Settings from the Optimization menu in Aspen
Utilities Planner.
2 Check the Enable start/stop calculations check box.
3 Run the optimization as usual. If an item of equipment is set as available
within the optimization input, the cost for changing the state of that item
of equipment (starting it up if it is currently off or shutting it down if is
currently on) is calculated.

Configuring Load Shedding
Aspen Utilities Planner can be used to determine the optimum load shedding
scheme. In order to configure Aspen Utilities Planner for load shedding
optimization, you need to specify which blocks are to be included in the
optimization and their load shedding cost. Follow the steps below to configure
the Aspen Utilities model for load shedding:
1 Specify which blocks should be included in the loadshedding calculation.
This is done by setting the AllowLoadShedding parameter to True in
the AllVariables table. Right click on the block and select Forms |
AllVariables.
Repeat this step until all blocks have been specified.
2 To account for lost production and other related costs, you can enter the
cost of load shedding in LoadShedCost, further down in the AllVariables
table.
3 You must also provide the availability and demand profiles to be used in
the load shedding calculation. Do this by filling in the OptInputMods table
in the Interface database (Interface.mdb).
An example is shown below. The example also shows multiple profiles –
two time periods to be considered in the optimization.

4 As a last step of configuration, you create a loadshedding problem by
creating and invoking a script in Aspen Utilities Planner.
Do the following to create a new script:
a Click Add Script at the Flowsheet Level in the Aspen Utilities Planner
Explorer and Enter a name, e.g. SteamLoadShedding.
b Click OK and a text editor is displayed. Enter the text shown in the
screen below. Here, n should be replaced with the number of periods that
are being considered in the load shedding calculation.

c You can run the script by double-clicking on it in the Contents Pane.
You can also run the script programmatically. For example, you can create
a Visual Basic script function in Excel with the following contents:
Public Sub cmdCreateShed_Click()
On Error GoTo ErrHandle
Set AUapp = Application.Run("GetAMApp")
…
…
AUapp.Simulation.Flowsheet.Invoke "SteamLoadShedding"
Exit Sub
ErrHandle:
MsgBox Err.Description
End Sub
5 Run optimization. When the optimization is complete you can check the
solution as usual in Aspen Utilities Planner or create a Visual Basic
function to extract the results from Aspen Utilities Planner to Excel in a
user-preferred format.
Obtaining Marginal Utility Cost
To obtain the marginal cost of utility headers (e.g. steam header, fuel header,
etc.) at the optimal solution you should follow below steps:
1 Display the Optimization Setting dialog by selecting Optimization | Edit
Optimization Settings… from the Aspen Utilities Planner menu.
2 Select the check box Calculate marginal utility costs.

You must indicate which headers are to be included in the marginal cost
calculation.
3 Display the summary table for the desired header by double-clicking on it.
Select True for the IncludeMarginalCost parameter. Repeat this step
until all desired headers are specified:

4 Run the optimization. When the optimization completes the marginal cost
of header is reported in the variable MarginalCost in the summary table of
the header model.

Identifying Optimization Errors
The Aspen Utilities optimization model is linear and uses a mature integer
linear programming technique do the optimization. In the majority of the
cases the model will run without problems. However, data input errors can
cause optimization failure – namely infeasibilities.
Aspen Utilities Planner contains two error diagnostic mechanisms to help
detect optimization errors: presolve checking and error tracking. You can
access optimization error diagnostics from the Optimization menu in Aspen
Utilities Planner:
Click Optimization Error Diagnostics… to display the following window:
 Run Presolve Error Check – executes presolve error checking.
 Execute Error Tracking Run – performs error tracking.

 View LP Model – brings up a list file, (a Dash compilation file for the
model).
 View Log file – the optimization iteration log, which could contain
infeasibility information if the optimization failure is caused by infeasibility.
This file is displayed at the end of running Presolve Error Check.
Presolve Error Checking
Presolve error checking uses the built-in solver presolve checking function to
identify possible infeasibility errors (for example, a minimum bound is greater
than a maximum bound on a variable).
Below is an example of a typical user input error and presolve checking
report:
This error report indicates that the particular LP problem is infeasible due to
the equation FPort(1, Boiler, BFW), which points to port BFW in block Boiler in
the flowsheet. The infeasibility is that in this case, the lower bound of the
BFW port in the boiler is 75.8 tonnes/hr but the upper bound of connected
stream flow is 30 tonners/hr only. So the Lower Bound is greater than the
Upper Bound.
Therefore, you can correct the incorrect data and then begin your calculation.

Error Tracking
Apart from the above obvious type of infeasibility, there could be other
infeasibility due to the failure of closing the mass balance on a process block.
This is more difficult to detect and usually cannot be picked up by the solver
built-in presolve mechanism.
In Aspen Utilities Planner, error tracking is carried out by introducing a
balance variable on each mass balance equation which is minimized in the
objective function. When the optimization completes, the problematic
balance equations and corresponding blocks containing the balance equations
will be listed in the simulation message window. This should give an indication
of where to search for faulty limit specifications.
In general, this type of error is much more difficult to detect than the first
type. It requires careful engineering analysis and familiarity with the
flowsheet even after identifying the error by using Error tracking.
The following forms show an example of input error and using the error-tracking
mechanism to detect it:

Note: LP Process Steam Generation is 1000 tonnes/hr (much higher than the
maximum boiler steam generation (200 tonnes/hr)).
Although the input is correct in mathematical terms (minimum<=maximum)
and the presolve mechanism does not detect any error, it causes an infeasible
solution when the optimization runs.
An Error Tracking run with the input data has the following output:

Note: The solution contains objective function values that are very big
numbers. This usually indicates the balance variables are non-zero in some
process balance equations.
In the simulation message window, the error messages indicate that the
balance equation in block HPHDR is not balanced (this becomes balanced only
with non-zero relaxation variables). By inspecting the profiles data, we find
that the LP Steam Generation (LPGEN) is too large and hence causes the
infeasible solution.

Setting up Options for
Optimization
Multiple Period Run Mode
When running a multi-period optimization in Aspen Utilities Planner, you can
use one of two modes: Simultaneous or MultiRun. The
MultiPeriodRunMode parameter in the Globals Table is set to the desired
mode:
Simultaneous mode means that the entire optimization model covering all
periods is solved simultaneously. This approach can be slow and poses
numerical difficulties when dealing with a large optimization model. However,
under some circumstances (e.g., equipment Startup/Shutdown, when time-dependent
utility contracts need to be taken into account, etc.), this mode
must be used to satisfy optimization constraints.
MultiRun, as indicated by its name, makes optimization runs as many times
as there are periods defined in the model. Convergence is relatively fast and
robust with this mode. You should use this mode when there is no
requirement to connect one period optimization to another period
optimization.

Settings for Mixed Integer
Linear Solver
Please refer to the following Optimization Settings dialog box for settings
discussed in this section:
Cut Strategy
Cut strategy is a setting that controls the number of cuts generated in each
branch and bound solution. The following table summarizes the available cut
strategy. You should refer to general Branch and Bound methods for mixer
integer linear programming to understand more about Cuts:

Values for Cut Strategy Description
-1 Automatic selection of the cut strategy.
0 No cuts.
1 Conservative cut strategy.
2 Moderate cut strategy.
3 Aggressive cut strategy.
Cut off Value (Max. Expected Cost)
If you know you are interested only in values of the objective function which
are better than some value, you can specify this value in Cut off value
(Max. expected cost). This allows the Optimizer to ignore solving any nodes
which may yield worse objective values, saving solution time. It is set
automatically after an LP Optimizer command, unless it was previously input
here.
Note: Since cost minimization is the objective in an Aspen Utilities
optimization, the cut off value can also described as the maximum expected
utility cost.
Optimum Gap from Optimality (%)
This determines whether or not the global search will terminate. Essentially,
the global search will stop if:
| MIPOBJVAL - BESTBOUND | <= GAP (%) * BESTBOUND
where MIPOBJVAL is the value of the best solution's objective function and
BESTBOUND is the current best solution bound.
For example, if you enter a 5 (%) here, the global search will stop when a
MIP solution has been found and the Optimizer can guarantee it is within 5%
of the optimal solution.
Presolve Strategy
The Optimizer provides a number of algorithms for simplifying a problem prior
to the optimization process. This elaborate collection of procedures, known as
presolve, can often greatly improve the Optimizer's performance by
modifying the problem matrix, making it easier to solve. The presolve
algorithms identify and remove redundant rows and columns, reducing the
size of the matrix. In most cases this is a helpful tool in reducing solution
times. However, presolve is included as an option and can be disabled by
entering 0 for Presolve Strategy. Here, we have other three options: 1, 2 and
3. 1 means conservative, 2 moderate and 3 aggressive. The default value is 2
(moderate).

4 Aspen Utilities On-line
Implementation
Linking with InfoPlus.21 via Aspen Online, Aspen Utilities can be configured as
an on-line implementation. In online mode, Aspen Utilities takes data
automatically from the real-time data historian at certain time intervals and
updates the demand profiles automatically.
One of the main differences between offline implementation and online
implementation is that Aspen Utilities must run unattended. Therefore Aspen
Utilities must be configured to run without user intervention.
Calculating Utility Demand
Targets
The Demand Forecasting Editor (DFE) is normally used interactively to
calculate the utility demands. Since this is not possible in online mode you
must configure it to run in an automatic manner as described in the steps
below:
1 Setup the demand forecasting database, DemandData.mdb.
Refer to Appendix 1 – Configuring the Demand Forecasting Editor for the
detailed information on how to configure the demand forecasting
database.
2 Open the On_Line form. This form is available for all demand blocks and
for the GeneralModel block.
Right click the mouse on one of these block types and select Forms |
On_Line.
4 Aspen Utilities On-line Implementation 89

In this form you need to give the number of inputs (nInputs), its
corresponding ID and input values (array OptInputVar), the number of
process operating modes (nModes), its corresponding ID (array ModeID)
and mode value (array ModeValue). The On_line form is illustrated in the
following example.
In this example, two blocks, FCC and CRU, contribute to the total LP
consumption (LPUSE). The LP consumption correlation for FCC has one
independent variable (FCC_Throughtput) and the correlation for CRU has
two independent variables (CRU_Throughput and CRU_ARO); therefore,
the total number of inputs (nInputs) is 3. Each process has a different
operating mode and thus nModes is 2. The values for ModeID are given as
FCC_Mode and CRU_Mode, respectively (arbitrary, but descriptive). There
are two operating modes for each process and thus nModeValue is 2
respectively. You also need to specify the number of target variables, in
this case the number of LP consumption for nTargets and name of the
contribution from each process (FCC_LPUSE and CRU_LPUSE) for
TargetVariableID.
The calculation result will be displayed and stored in array TargetValue for
each processes.
90 4 Aspen Utilities On-line Implementation

Note: All these names (IDs) must be the same as those defined in the
database.
Specifying Demands for On-line
Optimization
Utility import and export can be varied in an Aspen Utilities on-line
optimization. For instance, natural gas import from the supplier could be
minimized while power export could be maximized.
This might not be the case for other utility supplies and demands. For
example, steam export from production processes cannot be changed due to
fixed production throughput or operating conditions, and steam demand from
production is also fixed due to fixed process throughput.
To handle these situations properly, you must specify which utility
feeds/demand blocks have fixed utility flow at its current value in the
optimization. Specify fixed utility flow by setting the OptInputFlag
4 Aspen Utilities On-line Implementation 91

parameter to True in the On_Line form for the various types of Feed and
Demand blocks and the GeneralModel block.
92 4 Aspen Utilities On-line Implementation

5 Microsoft Excel Interface
You can run Aspen Utilities Planner and view the results from within Microsoft
Excel. This allows you to develop a graphical representation of your flowsheet
and to retrieve and report Aspen Utilities Planner results within Excel. This
chapter describes how to use the Aspen Utilities Planner – Microsoft Excel
interface.
Installing the Aspen Utilities
Planner Add-In
The first step is to install the Aspen Utilities Planner Excel Add-In. Execute the
following steps to install the Add-In:
1 Start Microsoft Excel.
2 Select Tools | Add-ins.
3 Use Browse to find the Aspen Utilities Planner Add-In, named
utilities240.xla. This file is located in the bin subdirectory of the Aspen
Utilities installation (default location is installation drive:Program
FilesAspenTechAspen Utilities Planner V7.2bin).
4 Select utilities240.xla and click OK.
If you previously had installed this Add-In you are asked if you want to
replace the existing reference, click Yes.
5 When the Add-In installed a new menu item - named Aspen Utilities – is
added to the Excel menu bar.
5 Microsoft Excel Interface 93

Aspen Utilities Excel Menu Items
When the Aspen Utilities Planner Add-In is installed, the Aspen Utilities menu
item will be present on the main excel menu bar.
 Open Aspen Utilities File – used to browse to and select an Aspen
Utilities Planner file (an .auf file).
 Show Aspen Utilities – make Aspen Utilities Planner visible. By default,
Aspen Utilities Planner is not visible when an Aspen Utilities Planner file is
opened.
 Hide Aspen Utilities – allows you to hide Aspen Utilities Planner.
 Close Aspen Utilities – close the Aspen Utilities file and shutdown Aspen
Utilities Planner.
 Simulate Flowsheet – run a flowsheet simulation. This option is the
same as the run simulation in Aspen Utilities Planner with two important
additions: 1. before the simulation runs, values are sent from the
spreadsheet to Aspen Utilities Planner, and 2. when the run has finished
the latest values are retrieved from Aspen Utilities Planner.
 Run Reconciliation – runs data Reconciliation.
 Optimize Flowsheet – runs an optimization. As with Simulate Flowsheet,
values are sent from the spreadsheet to Aspen Utilities Planner before the
optimization and values are retrieved from Aspen Utilities Planner when
the optimization is complete.
 Simulation Menu
o Load Simulation Links – loads the Simulation Links command bar
and generates the Simulation Links worksheet if it not present.
94 5 Microsoft Excel Interface

o Send Values – this option retrieves the values of variables on the
Simulation Links worksheet and sends them to Aspen Utilities Planner
o Get Latest Values – this option retrieves the latest values from
Aspen Utilities Planner for the variables selected on the Simulation
Links worksheet.
 Reconciliation Menu
o Load Reconciliation – loads the reconciliation bar and generates the
Reconciliation worksheet if it not present.
o Get Latest Values – this option retrieves the latest values from
Aspen Utilities Planner for the variables selected on the Simulation
Links worksheet.
 Optimization Menu
o Get Optimization Results – when an optimization run is completed,
the results shown in the Simulation Links sheet are for the first period
only. To view the results from other periods, select this menu item and
input the period number of interest. The flowsheet re-simulates and
the results are displayed for that period.
o Editors… – displays the Profiles and Tariff Data editors.
 Refresh Data – updates the data shown in the spreadsheet.
At the bottom of the Aspen Utilities menu item is a list of the most recently
opened Aspen Utilities files. This recent file list is discarded when the Add-In
is uninstalled.
Open Aspen Utilities File
An Aspen Utilities file must be opened before any Aspen Utilities menu items
become available and before the Simulation Links worksheet can be
configured.
1 Select Open Aspen Utilities File from the Aspen Utilities menu item.
2 Use Browse to search for the file you want to open.
3 Click OK.
The status bar in Excel shows the full path name of the file being opened.
When the file is open the status area message changes to Ready.
If required, you can make Aspen Utilities Planner visible by selecting Show
Aspen Utilities from the Aspen Utilities menu.
Running a Simulation from
Excel
This section describes how to setup Excel to send and retrieve values from
Aspen Utilities Planner.

Creating a Simulation Links worksheet
Simulation Links is used, as the name implies, to create links between Excel
and your Aspen Utilities Planner flowsheet (the .auf file).
You can add a simulation links worksheet by selecting the menu item Aspen
Utilities | Simulation | Load Simulation Links.
Note: If a Simulation Links worksheet already exists a new one will not be
added.
A blank Simulation Links worksheet is shown below:
There are two sections in the Simulation Links sheet: the left-hand side is
used for sending values to Aspen Utilities Planner and the right-hand side is
used to retrieve values from Aspen Utilities Planner.
Note: A Simulation Links command bar is added to the Excel menu area.
All information is saved with the spreadsheet. If you change the Aspen
Utilities Planner file in certain ways (e.g., renaming a block, removing a block,
changing the model by removing a variables, etc.), some links may become
invalid and these cells are highlighted yellow the next time the spreadsheet is
open. A yellow highlight indicates the block or variable in the simulation link
does not exist in the currently opened Aspen Utilities flowsheet.

Configuring Blocks and Variables for Input
to Aspen Utilities Planner
To configure blocks and variables to send to Aspen Utilities Planner follow
below steps:
1 Click on the left-hand side dropdown list to display all block names in the
flowsheet as shown below:
2 Select the block of interest and the name will be added to the first empty
row on the Send Values side.
3 Click Load Variables (see above figure).
4 Click on the Variable Name drop-down list to display all the variables
associated with the selected block. Select a variable and its name is
inserted next to the block name in the worksheet. An example of the
variable name list is shown below.

5 Enter the desired value in the Value cell.
6 Continue the above steps until all your input variables are selected. When
the data on the spreadsheet reaches the last couple of rows near the
bottom of the worksheet a line is automatically added.
7 By default, the value you enter must be in the current unit of measure
defined in Aspen Utilities Planner. You can enter a different unit of
measure in the Unit column (e.g., GJ/hr for energy flow, ton/hr for mass
flow, etc.). The value will be converted to the new unit when it is sent to
Aspen Utilities Planner. If you select the menu item Aspen Utilities |
Simulation | Send Values, the values are converted and sent without
executing simulation. This is done automatically when you simulate or
optimize the flowsheet. Take care when entering a different unit of
measure, that the string you enter is known to Aspen Utilities Planner.
Configuring Blocks and Variables for
Retrieval from Aspen Utilities Planner
Configuring blocks and variables to retrieve from Aspen Utilities Planner is
very similar to the procedure outlined in the previous section. Blocks and
variables to be retrieved from Aspen Utilities Planner are configured on the
right-hand side of the spreadsheet. Follow below steps:
1 Click on the third drop-down list from left to display all block names in the
flowsheet:
2 Select the block of interest and the name will be added to the first empty
row on the Retrieve Values side.
3 Click Load Variables (see above figure).

4 Click on the Variable Name drop-down list to display all the variables
associated with the selected block. Select a variable and its name is
inserted next to the block name in the worksheet. An example of the
variable name list is shown below:
5 By default, the displayed value is in the current unit of measure defined in
Aspen Utilities Planner. You can enter a different unit of measure in the
Unit column (e.g., GJ/hr for energy flow, ton/hr for mass flow, etc.). The
value will be converted to the new unit when it is retrieved from Aspen
Utilities Planner. If you select the menu item Aspen Utilities |
Simulation | Get Latest Values, the values are retrieved and converted
immediately. This is done automatically when you simulate or optimize the
flowsheet. Take care when entering a different unit of measure, that the
string you enter is known to Aspen Utilities Planner.

Mapping Variable Values to the Excel
Flowsheet
There are many advantages when using Microsoft Excel to run Aspen Utilities
Planner. One advantage is that it allows you to decompose complex
flowsheets into sub-flowsheets and draw them on separate worksheets. You
can then map variables from the Simulation Links worksheet to the cells in
the sub-flowsheet drawing in an intuitive way. A simple boiler model is used
here to illustrate this:
1 Starting with a new blank worksheet, draw a boiler and associated
streams using the drawing tools provided with Excel. It might look like:
2 Place the mouse cursor in the cell that you want to map to a Simulation
link and type = in the cell (cell E17 in the example above).
3 Switch to Simulation Links worksheet and click on the Value column for
the variable to map. Press the Enter key and Excel links the cells in the
two worksheets.
Note: The value column you should choose for the variable to map is the
value column in Retrieve latest values from Aspen Utilities form on the
right side.
4 Repeat these steps until all Simulation links have been mapped to your
flowsheet drawing.

Aspen utilities user guide v7 2

Aspen utilities user guide v7 2

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