Getting Started Guide

Aspen Utilites

Version V7.3March 2011

Copyright © 1981 – 2011 Aspen Technology, Inc. All rights reserved.

Aspen Utilities, Aspen Utilities PlannerTM, Aspen Utilities On-Line OptimizerTM (Utilities Optimizer), Aspen UtilitiesOperationsTM, SLM™, the Aspen leaf logo, and Plantelligence are trademarks or registered trademarks of AspenTechnology, Inc., Burlington, MA.

All other brand and product names are trademarks or registered trademarks of their respective companies.

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Contents i

Contents

Introducing Aspen Utilities .....................................................................................1

About This Document .......................................................................................1What You Need To Use This Guide......................................................................1Related Documentation.....................................................................................2Technical Support ............................................................................................2

Tutorial ...................................................................................................................3

Introducing Aspen Utilities Interface ...................................................................4The Aspen Utilities Planner Main Window...................................................4Initializing Physical Properties ..................................................................5

Developing a Flowsheet ....................................................................................5Adding Blocks to the Flowsheet ................................................................6Adding Data to the Blocks .......................................................................8Connecting Blocks with Streams...............................................................9Adjusting Variable Specifications ............................................................ 10Simulating an Aspen Utilities Flowsheet Model ......................................... 11

Optimizing the Flowsheet ................................................................................ 12Objectives ........................................................................................... 12Aspen Utilities Excel Interface................................................................ 13Utilities Nominations............................................................................. 14Utility Production Planning..................................................................... 17

Introducing Aspen Utilities 1

Introducing Aspen Utilities

In this document Aspen Utilities is used as a generic term to refer to bothAspen Utilities On-Line Optimizer (Utilities Optimizer), formerly known asAspen Utilities Operations, and Aspen Utilities Planner.

Aspen Utilities is an equation-oriented tool for the simulation and optimizationof Utility Systems (Fuel, Steam and Power), specially designed to address allthe business processes related to the operation and management of utilitysystems.

It can be used to address all the key issues in the purchase, supply and usageof fuel, steam and power within environmental constraints, and provides asingle tool to optimize energy business processes and substantially improvefinancial performance.

Aspen Utilities is based on Aspen Custom Modeler. The software is suppliedwith a library of unit operations associated with utility systems. You can alsowrite your own unit operation models and add these to the library.

Aspen Utilities uses a Mixed Integer Linear Programming (MILP) solver foroptimization.

About This DocumentThis guide contains tutorials designed for first-time users to Aspen UtilitiesV7.3.

In addition to providing an overview to the application, the tutorials take anew user through step-by-step flowsheet development and optimizationprocedures.

For more detailed information, please refer to the associated Aspen UtilitiesUser Guide and on-line help.

What You Need To Use ThisGuideTo use this guide, you need Aspen Utilities Planner™ installed on PC or PC fileserver running supported Windows operating systems. For information onhow to do this, read the Installation Guide supplied with the product, orcontact your system administrator.

2 Introducing Aspen Utilities

Related DocumentationIn addition to this document, the following documents are provided to helpyou learn and use the Aspen Utilities applications.

Title Content

Installation Manual and SLM Installation andReference Guide

(accessed from the AspenTech Installationsplash screen)

Full installation requirements andthe procedures required to install,verify, license, and run AspenUtilities.

Aspen Utilities User Guide Full user guidelines for all levels ofAspen Utilities user.

Technical SupportAspenTech customers with a valid license and software maintenanceagreement can register to access the Online Technical Support Center at:

http://support.aspentech.com

You use the Online Technical Support Center 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

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 proactively alert you to important technical supportinformation 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.

Tutorial 3

Tutorial

This tutorial uses the example Aspen Utilities model (example.auf) located inthe Examples folder of the installation directory. The model is used toinvestigate two off-line business processes.

The flowsheet for the model is shown below. For clarity and to displayadditional information, the display differs from that shown in theexample.auf; apart from these display differences, the flowsheets areidentical:

In terms of utilities, there is one supply of fuel, shown as block FuelFeed, andone supply of power shown as block Grid.

4 Tutorial

Introducing Aspen UtilitiesInterfaceTo start Aspen Utilities Planner:

1 Click Start, and then select Programs | AspenTech | ProcessModeling V7.3 | Aspen Utilities Planner | Aspen Utilities Planner tolaunch the application with a new flowsheet file already loaded.

2 To open an existing simulation, click File | Open.

3 Use the Look In list to locate the directory where the file you want toopen is stored, click the file you want to open, and click Open.

The Aspen Utilities Planner Main WindowWhen you start Aspen Utilities Planner the main window appears:

Optimization menu

All items paneFlowsheet window

Contents pane Message window

Flowsheet Window

The flowsheet window is where you build the flowsheet.

Tutorial 5

Explorer Window

The Explorer Window contains the All Items pane and the Contents pane.

Message Window

The message window displays all messages from Simulation andOptimization.

Optimization Menu

This menu items allows you to edit/set the input for optimization, allows youto launch the Profiles and Tariff Editor, change optimization settings, and startan optimization run.

Initializing Physical PropertiesWhen creating a new Aspen Utilities model you must initialize the physicalproperties:

1 Click on Component Lists in the Explorer pane.

2 Double click on Default in the Contents pane. A dialog box is generated.Click Yes.

3 A list box is generated allowing you to select the Aspen Plus PropertiesDefinition File to be used. Click Browse and use the Look In List box tolocate the directory where the file AspenUtilities.appdf is stored. Thisfile contains property information for steam/water and is stored in theExamples folder in the Aspen Utilities installation.

The default location is:

C:\Program Files\AspenTech\Aspen Utilities Planner V7.3

4 Click OK when you have located the file.

5 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 tomove the component to the right hand pane. Click OK.

Developing a FlowsheetThis section illustrates the procedure for developing an Aspen Utilitiesflowsheet model from a flowchart diagram. The flowchart for the process wewant to model/optimize is shown below. (The astute observer will notice thatthis diagram is actually the Boiler section of the flowsheet in example.auf.)

6 Tutorial

Adding Blocks to the FlowsheetAll unit operation models and streams are located in the Utilities library. Thiscan be accessed from the All Items pane in the Explorer window.

To select a model or stream:

1 Expand the utilities library folder and select the desired model or stream.

2 Drag the model or stream onto the flowsheet.

3 You can rename blocks and streams, and resize, rotate, and flip blocks,etc. Right-mouse-click on the block and select Rename Block in thecontext menu.

In this guide, we briefly discuss a few block types in the library required whendeveloping the example flowsheet.

Feed Blocks

Feed blocks are used to specify a supply of utility. This may be purchasedutility (such as natural gas) or a calculated supply of utility external to themodel (such as steam generated from the processes or fuel gas generated bythe processes).

There are separate feed blocks for feeds of air, steam, power, or fuel.Because each feed block has only one port, only one stream can be attachedto each feed block. To split the flow rate of a feed, place a header blockfollowing the feed block.

The following table lists typical specification variables for different Feed blocktypes:

Block Type Typical Specifications

FeedAir Temperature (Tout)

Mass flow (if necessary)

FeedFuel Molecular weight (MW_out)

LVH (CV_out)

Oxygen Demand (OD)

Tutorial 7

Carbon Index (CI) and Sulphur Index (SI) (If emissionscalculation is required)

Heat Flow (Flow) (if necessary)

FeedPower Power supply (if necessary)

FeedSteam Temperature (Tout)

Pressure (Pout).

Mass flow (if necessary)

Demand Blocks

Demand blocks are used to specify a demand for a utility, when demand isnot calculated within the model. The example here has a demand named HPSTEAM USE – the total high pressure steam required by all processesexternal to the Aspen Utilities flowsheet. Separate blocks are provided for air,steam, power or fuel demands. Because only one port is available on eachblock, only one stream can be attached to each demand block.

The following table lists typical specification variables for the differentDemand block types:

Block Type Typical Specifications

DemandSteam Flowrate (SteamIn(“SteamIn1”).F)

DemandPower Power demand (PowerIn(“PowerIn1”).Power)

DemandAir Flowrate (AirIn(“AirIn1”).F)

DemandFuel Heat flow (Default, FuelIn(“FuelIn1”).Flow)

Headers

The Header model is essentially a combination of mixer and splitter models.Four types of header models are available in the library: Air_Mix, FuelHeader,PowerHeader, and SteamHeader. All perform a mass and energy balance.

The following table lists typical specification variables for the different Headerblock types:

Block Type Typical Specifications

SteamHeader Tout: The nominal temperature at which the header or mixeris operating.

Pout: The pressure at which the header or mixer is operating.

All other variables can stay at the default value.

Air_Mix None.

FuelHeader None.

PowerHeader None.

8 Tutorial

Boiler

The Boiler model is used to simulate steam generation at a specified pressurewith full rigorous heat and material balance. It requires three feeds: a fuelsupply, an air supply, and a water supply. There are three outlet streamsfrom the boiler: generated steam, flue gas, and blowdown.

The following table shows the required input for the boiler model:

Specifications Corresponding Variables

Blowdown rate bd_rate (Default is 10%)

Oxygen in the flue gas O2out (Default is 0.05 kg/kg)

Pressure drop in steamgenerator

Pdrop_Gen (Default is 0)

Pressure drop in steamsuperheater

Pdrop_SH (Default is 0)

Steam outlet temperature Tboiler (Default is 345°C)

Efficiency Constantefficiency

EffMethod = Constant

ConstEff (default is 100%)

Efficiency curve EffMethod = LookUpTable

Neff (default is 5)

Choose whether to extrapolate thecurve (Default is yes)

EffTable (The efficiency curve is inthe form of Steam Generation Rateversus efficiency)

With the above information you should be able to build a flowsheet in AspenUtilities that represents the flowchart at the beginning of this section.

Process Stream Name Model Type (Block Name) in Utilities Library

Natural Gas FeedFuel (NATGAS)

Boiler Boiler (BOILER)

HP Header Steamheader (HPHDR)

HP STEAM USE DemandSteam (HPUSE)

MAKE UP WATER FeedSteam (MKUP)

Air FeedAir (FeedAir)

Nat Gas Header Fuelheader (Fuelheader)

BFW FeedSteam (BFW)

Adding Data to the BlocksData input for various blocks is entered via forms. Double-clicking on a blockloads a Summary form which contains most of the variables you want toaccess. Other forms can be accessed by right-mouse-clicking on the block andselecting the desired input form from the Forms menu – as illustrated below:

Tutorial 9

As a minimum, a block has the following forms:

AllVariables – contains all of the variables defined in the block.

Summary – contains a selection of variables that are commonly specifiedor viewed.

Optimization_Limits – allows you to specify hard constraints for theitem of equipment. Examples of optimization constraints are minimumsteam generation capacity or maximum power generation.

There may be additional forms, depending on the block. For example, someblocks allow efficiency curves to describe the block performance.

Connecting Blocks with StreamsStreams can only be connected to blocks that have valid Ports. That is, fuelstreams can only be connected Fuel Ports, steam to Steam Ports, powerstreams to Power Ports, and air streams to Air Ports.

Some blocks may have ports for all utility types; others may have only oneport type. Single ports can be connected to only one stream, while multi-portscan be connected to any number of streams. When connecting streams toblocks, only the appropriate port(s) will be highlighted as available forconnection.

Some blocks may have more than one port of the same type but the port hasa specific function and, therefore, it is necessary to connect the stream to thecorrect port. When a block is selected that has more than one port of thesame type, a drop down list is shown from which the correct port can beselected, as shown in the diagram below. Here, a SteamStream is beingconnected to a Header block that has the three types SteamStreamconnections shown.

10 Tutorial

Adjusting Variable SpecificationsAspen Utilities is an Equation Oriented (EO) modeling environment (derivedfrom Aspen Custom Modeler). In the EO environment variables declared inthe process model can be either fixed or free. Fixed variables can be thoughtof as input variables while free variables are calculated from the fixedvariables and the model equations. Each block and stream has typicalvariables that need to be set or specified to configure the model correctly, aswell as typical result/calculated variables.

These typical variables can be accessed by double-clicking on the block in theflowsheet.

In some cases, it is necessary to change the fixed/free specifications, but thisshould always be done with care. Degrees of freedom rules and other keyrequirements must be respected. In example.auf, for example, when all thefeed blocks are connected to the boiler block, the degrees of freedom (DOF)of the entire flowsheet are over specified by 2. This is because initiallyVHPSteam generation rate, the Fuel flow rate, the BFW flow rate, and the Airflow rate all have fixed values. Specifying any two, for example theVHPSteam generation rate and Fuel flow rate, allows the BFW flow rate andAir flow rate to be calculated. Therefore two of those variables must bechanged from fixed to free. Changing these two variables from fixed to free

make the flowsheet square as indicated by the icon in the status area.

The following guidelines for changing fixed and frees (Degrees of Freedom)should be followed:

When two blocks are connected with a stream, one of the blocks flowsneeds to be freed in order to maintain the degrees of freedom.

Only port flows should be set to fixed.

Only exchange fixed and free variables between identical variable types,unless you have a clear understanding of the implications of the change.

Tutorial 11

Stick to the default form when changing fixed and free variables (the onethat appears when you double-click on the block icon.

Keep the flowsheet square as you build the flowsheet and do not connectall the blocks before you try to satisfy the DOF. This can be achieved bytrying to simulate the flowsheet after adding each block.

If all fails, there is a specification analysis tool available by double-clicking

on the icon in the status area:

Refer to Tools-Specification Analysis and Aspen Customer Modeler Help topicsfor more information on how to use this feature.

Simulating an Aspen Utilities FlowsheetModelYou can continue building the flowsheet until it looks like the one in thefollowing diagram. Alternatively, you can open example.auf in the AspenUtilities Installation (the default location is Installation Drive\ProgramFiles\AspenTech\Aspen Utilities Planner V7.3\Examples\Example.auf).

12 Tutorial

The flowsheet can be run in Simulation mode after it is built and madesquare:

A simulation can be started by clicking on the Simulation Run button on thetoolbar or from the Run menu.

Once the simulation is complete, you can check results by displaying thesummary table of each block. Alternatively, you can view key variables inMicrosoft Excel; this is discussed in the Optimizing the Flowsheet in the AspenUtilities Excel Interface section.

Optimizing the Flowsheet

ObjectivesAt this point we have simulated the flowsheet; next we want to optimize it. Tooptimize the flowsheet, we need to set the optimization bounds and enter thecost for various utilities. The objective of the optimization is to achieve theminimum operating cost.

Given the flowsheet we have built (or example.auf), we will look at twobusiness processes – Utilities Nominations and Utilities Production Planning.The two cases will be run from Microsoft Excel to show how the Aspen UtilitiesExcel Add-In works.

Tutorial 13

Aspen Utilities Excel InterfaceYou can access all of the functionality of Aspen Utilities from within MicrosoftExcel. In addition, you can easily access Aspen Utilities flowsheet variablesand optimization results.

In this section we do not cover every detail in the Excel interface. Instead wefocus on how to access the basic Aspen Utilities optimization functionalityfrom Excel.

Further details of the Excel interface can be found in the “Microsoft ExcelInterface” chapter in the Aspen Utilities User Guide.

The basic steps in using the Excel Add-In are:

1 Start Excel. Load the Aspen Utilities Excel Add-In if the Aspen Utilitiesmenu is not present on the main Excel menu bar:

Select Tools | Add-Ins… and browse to Utilities240.xla in the AspenUtilities Planner V7.3 bin folder.

2 Open an Aspen Utilities flowsheet using the menu item: Aspen Utilities |Open Aspen Utilities.

3 Load the Simulation Links worksheet if it does not exist:

Select Aspen Utilities | Simulation | Load Simulation Links. You needto confirm that you want to add the Simulation Links worksheet.

This worksheet is used to send values to Aspen Utilities (from the left sideof the worksheet) and to receive values from Aspen Utilities (on the rightside of the worksheet). An example is shown here:

4 Draw a flowsheet using the Excel drawing tools in a blank worksheet. Youcan map variables on the Simulation Link worksheet to the cells on thisflowsheet.

14 Tutorial

5 Edit profile and tariff data by selecting Aspen Utilities | Optimization |Editors....

6 Run optimization by selecting Aspen Utilities | Optimize Flowsheet.

When the optimization converges, the values of the configured variables areautomatically updated in the excel flowsheet and Simulation Links worksheet.

The Excel spreadsheet used here is example.xls included in the Examplessubdirectory of the Aspen Utilities installation folder. All the variables arealready mapped in example.xls. Please refer to the Aspen Utilities UserGuide for more details of the Excel interface.

Utilities NominationsThe first business process we consider is Utilities Nominations.

The contract for the fuel feed stipulates that you must provide an estimate ofthe amount of gas to be purchased. The amount of fuel that is requireddepends upon the steam that is required in the process units, how muchpower is generated in the gas turbine and the two steam turbines, which inturn depends upon whether it is more cost effective to generate powerinternally or purchase power.

To run the model to determine the gas nomination:

1 Start Excel and open the interface file example.xls, which is found in theExamples subdirectory of the installation folder.

If Aspen Utilities menu does not appear in the Excel main menu bar,please see the previous section or refer to the “Microsoft Excel Interface”chapter in the Aspen Utilities User Guide for how to install it.

2 Use the Aspen Utilities menu item open the Aspen Utilities fileexample.auf found in the installation folder.

3 Use the Aspen Utilities menu item Optimization | Editors... to open theprofiles and tariff data editor. Amend the demand profile values in thedata editor to show the following demands:

o HP process steam generation 10 tonnes/hr.

o LP process steam generation 40 tonnes/hr.

o HP Steam use 90 tonnes/hr.

o LP Steam use 50 tonnes/hr.

o Site power demand 20 MW(e).

Amend the availability profile values in the data editor to show:

o All of the equipment is available.

o The power generation from the GTG can vary between 0 and 10 MW.

o The steam flow to STG1 can vary between 0 and 20 tonne/hr.

o The steam flow to STG2 can vary between 0 and 30 tonne/hr.

o The steam generation from the boiler can vary between 0 and 200tonne/hr.

o The fuel to the HRSG can vary between 0 and 2000 GJ/hr.

Tutorial 15

Here we assume that the profile and tariff databases have been configuredso all the profiles are listed in the data editors’ grid. The databasesshipped with Aspen Utilities (ProfileData.mdb and TariffData.mdb) containthis data.

If you start a new project with blank databases, you must add theappropriate profiles into the databases. The Profiles Editor has a featurethat makes it easy to select blocks and ports for configuring the profiles.

Please refer to “Updating Profiles” in the “Data Editors” chapter of theAspen Utilities User Guide.

Values for demand profiles (e.g. 10 MW for power generation, etc.) canalso be obtained from the Demand Forecasting application, which is usedto predict the various utilities demands using the process throughput andoperating conditions.

Please refer to “Demand Forecasting Editor” in the “Data Editors” chapterof the Aspen Utilities User Guide for more details.

4 Click Tariff to show the tariff data. Amend the contract to show thefollowing:

o Power import is £ 35/MWh and is unlimited.To show and unlimited usage put a very large number as either thehourly or total maximum.

o The gas costs £ 2.5/GJ and since we want to carry out a nominationrun this value should be unlimited.

5 Click Commit to save the data and send it to the model.

You will be asked to specify the start and end time for the optimization.Use the default values and click Apply. Close the editor window.

6 Start the optimization run by selecting Optimize Flowsheet from theAspen Utilities menu. An Optimization Message Window is opened whichshows the progress of the optimization. When the optimization is completeyou will hear a beep and the last line will state Optimization Complete.

16 Tutorial

7 The amount of fuel required can be seen on the flowsheet graphic:

The amount of fuel required is shown hereand this should become the nomination

8 Close Aspen Utilities and shut down Excel before starting the next section.

Tutorial 17

Utility Production PlanningThe second business process looks at the most optimum way of generatingutilities taking into account the constraints of purchased utility supply andequipment.

You provided the nomination generated in the last run to your gas supplier.The gas supplier has told you that you cannot have the required amount andthat your use is limited to 340 GJ/hr. The penalty structure of the contract issuch that you will incur a very large charge if you exceed this amount of gas.You need to determine what the most cost effective way is to use this gaswhile still satisfying the process demands.

1 Load example.xls and the Aspen Utilities file by following steps 1 and 2described previously.

2 The process utility demands and equipment availability are the same asfor the previous run and therefore do not need to be changed.

3 Use the Aspen Utilities menu item Optimization | Editors… to open theprofiles and tariff data editor. Click Tariff and fix the maximum hourlyflow of gas to 340 GJ/hr.

4 Click Commit to save the data and send it to the model.

You are asked to specify the start and end time for the optimization. Usethe default values and click Apply. Close the editor window.

5 Start the optimization run from the Aspen Utilities menu item by selectingOptimize Flowsheet.

6 Review the flowsheet to see what changes are made to the loads and setpoints on the pieces of equipment.