advanced simulation case using hysys

5/28/2018 Advanced Simulation Case Using Hysys

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Getting Started 1

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Getting Started

2000 AEA Technology plc - All Rights Reserved.Chem 1_3.pdf


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2 Getting Started

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WorkshopThe Getting Started module introduces you to some of the basic

concepts necessary for creating simulations in HYSYS. Some of the

things you will learn from this module are:

Methods for moving through different environments

Selecting property packages and components

Adding streams

Attaching utilities

You will use HYSYS to define three streams. You will learn how to

determine the properties of these streams by using the Property Table

utility.

Learning ObjectivesOnce you have completed this section, you will be able to:

Define a Fluid Package (Property Package and Components)

Add Streams Understand Flash Calculations

Attach Stream Utilities

Customize the Workbook


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Getting Started 3

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Building the Simulation

The Simulation Basis Manager

HYSYS uses the concept of the Fluid Package to contain all necessary

information for performing flash and physical property calculations.

This approach allows you to define all information (property package,

components, interaction parameters, reactions, tabular data,

hypothetical components, etc.) inside a single entity. There are three

key advantages to this approach:

All associated information is defined in a single location,allowing for easy creation and modification of the information

Fluid Packages can be stored as a completely separate entityfor use in any simulation

Multiple Fluid Packages can be used in the same simulation;however, they are all defined inside the common BasisManager.

The Simulation Basis Manager is a property view that allows you to

create and manipulate every Fluid Package in the simulation.

Whenever you begin a New Case, HYSYS places you at this location.

The opening tab of the Simulation Basis Manager, Fluid Pkgs, contains

the list of current Fluid Package definitions. You can use multiple Fluid

Packages within one simulation by assigning them to differentflowsheets and linking the flowsheets together.


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4 Getting Started

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Inside the Current Fluid Packagesgroup, there are a number ofbuttons:

View - this is only active when a Fluid Package exists in thecase. It allows you to view the property view for the selectedFluid Package.

Add allows you to create and install a Fluid Package into thesimulation.

Delete removes the selected Fluid Package from thesimulation.

Copy makes a copy of the selected Fluid Package.Everything is identical in the copied version, except the name.This is useful for modifying fluid packages.

Import allows you to import a predefined Fluid Package fromdisk. Fluid Packages have the file extension.fpk.

Export allows you to export the selected Fluid Package to adisk. The exported Fluid Package can be retrieved into anothercase, by using the Import function.

You can use the hot key to re-enter the Simulation Basis

Manager from any point in the simulation or choose the EnterBasis

Environmentbutton from the button bar.

Basis Environment button


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Getting Started 5

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Defining the Simulation Basis1. Start a new case by selecting theNew Casebutton.

2. Create a Fluid Packageby selecting theAddbutton from theSimulation Basis Manager.

3. Click theActivity Modelradio button and choose NRTL as theProperty Package.

4. Change the Namefrom the default Basis-1to Stripper. Do this byclicking in the "Name" cell, and typing the new name. Hit the

key when you are finished.5. Switch to the Componentstab. From this tab, you add

components to your case.

New Case button


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6 Getting Started

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You can select components for your simulation using several differentmethods:

Note: You can add a range of components by highlighting the entire

range and pressing theAdd Purebutton.

To Use Do This

Match Cell 1. Select one of the three nameformats, SimName, Full Name/Synonym, or Formulabyselecting the correspondingradio button.

2. Click on the Matchcell and

enter the name of the

component. As you start to

type, the list will change to

match what you have entered.

3. Once the desired component ishighlighted either:

Press the key

Press the Add Purebutton

Double click on the component toadd it to your simulation.

Component List 1. Using the scroll bar for themain component list, scrollthrough the list until you findthe desired component.

2. To add the component either:

Press the key


Double click on the component toadd it to your simulation

Family Filter 1. Ensure the Matchcell is empty,and press the FamilyFilterbutton.

2. Select the desired family from

the Family Filterto display only

that type of component.

3. Use either of the two previous

methods to then select the

desired component.

4. To add the component either:

Press the key


Double click on the component to

add it to your simulation


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Getting Started 7

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5. Select the library components Chloroform, Toluene, Ethanol,H2O, Oxygen andNitrogen.

6. Go to the Binary Coeffstab. Press the Unknowns Onlybutton toestimate missing coefficients. View the Aij, Bijand ijmatrices byselecting the corresponding radio button. The Aij matrix is shownbelow:

To view the Bijor ijcoefficients, click theappropriate radio button inthe Coefficient Matrix to Viewgroup.


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8 Getting Started

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Exporting Fluid PackagesHYSYS allows you to export Fluid Packages for use in other simulations.

This functionality allows you to create a single common Fluid Package

which you may use in multiple cases.

1. On the Fluid Pkgstab highlight the StripperFluid Package.

2. Press the Exportbutton.

3. Enter a unique name (Stripper) for the Fluid Package and pressthe OKbutton.

Now that the Fluid Package is now fully defined, you are ready to move

on and start building the simulation. Press the Enter Simulation

Environmentbutton or theInteractive Simulation Environment

button in the Button Bar.

HYSYS will automatically addthe file extension .fpk when itsaves your Fluid Package. Thefile is automatically saved tothe \HYSYS\pakssubdirectory.


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Getting Started 9

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Selecting a Unit SetIn HYSYS, it is possible to change the unit set used to display the

different variables.

1. From the Toolsmenu, choose Preferences.

2. Switch to theVariablestab, and go to the Unitspage.

3. If it is not already selected, select the desired unit set. Both Fieldand SI units will be given in this course; you are free to use

whichever is more comfortable for you.4. Close the window to return to the simulation.


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10 Getting Started

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Changing Units for a SpecificationTo change the units for a specification, simply type the numerical value

of the specification and press the space bar or click on the unit drop

down box. Choose the units for the value you are providing. HYSYS will

convert the units back to the default units.

You can scroll through theunit list by starting to type theunits, by using the arrow keysor by using the scroll bar.


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Getting Started 11

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Adding StreamsIn HYSYS, there are two types of streams, Material and Energy. Material

streams have a composition and parameters such as temperature,

pressure and flowrates. They are used to represent Process Streams.

Energy streams have only one parameter, a Heat Flow. They are used to

represent the Duty supplied to or by a Unit Operation.

There are a variety of ways to add streams in HYSYS.

In this exercise, you will add three streams to represent the feeds to anair stripper. Each stream will be added using a different method of

installation.

To Use This Do This

Menu Bar SelectAdd Streamfrom the

Flowsheet menu.

Or

Press the Hot Key.

The Stream property view will open.

Workbook Open the Workbook and go to the

Material Streamstab. Type a stream

name into the **New** cell.

Object Palette Select Object Palettefrom the

Flowsheetmenu or press to

open the Object Palette. Double

click on the stream icon.


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12 Getting Started

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Adding a Stream from the Menu BarThis procedure describes how to add a stream using the hot key.

1. Press the hot key. The Stream Property view is displayed:

You can change the stream name by simply typing in a new name in the

Stream Name box.

2. Change the stream name to Eth rich.


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Getting Started 13

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Entering Stream CompositionsThere are two different methods to enter stream compositions from the

Worksheettab.

3. Double click on the Mass Flowcell. The Input Composition forStreamview displays.

4. We want to define the composition of this stream by specifyingthe mass flows for each component. By default, HYSYS has

chosen the basis for defining the composition as mass fraction.Press the Basisbutton and select the Mass Flowsradio button inthe Composition Basisgroup. You are now able to enter the datain the desired format.

When Using the Do This

Conditions page Double click on the Molar Flow cell

to enter mole fractions.

Or

Double click on the Mass Flow cell to

enter mass fractions.

Or

Double click on the LiqVolFlow cellto enter volume fractions.

The Input Composition for Stream

dialog is shown.

Composition page Press the Editbutton.

The Input Composition for Stream

dialog is shown.


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14 Getting Started

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5. Enter the following compositions:

6. Press the OKbutton when all the mass flows have been entered.

7. Close the Stream Property view.

For This Component Enter This Mass Flow, kg/h (lb/hr)

Chloroform 2.5 (5.0)

Toluene 0

Ethanol 300 (600)

H2O 100 000 (200, 000)

Oxygen 0

Nitrogen 0

Note: If there are values, either enter 0 or presstheNormalizebutton.


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Getting Started 15

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Adding a Stream from the WorkbookTo open or display the Workbook, press the Workbookbutton on the

Button Bar.

1. Enter the stream name, Tol richin the **New** cell.

2. Enter the following component mass flow rates. You will have tochange the basis again.

3. Close the Stream Property view.

Workbook button

For This Component Enter This Mass Flow, kg/h (lb/hr)

Chloroform 1.5 (3.0)

Toluene 140 (280)

Ethanol 0

H2O 100 000 (200, 000)

Oxygen 0

Nitrogen 0


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16 Getting Started

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Adding a Stream from the Object Palette1. If the Object Paletteis not open on the Desktop, press the

hot key to open it.

2. Double Click on the Material Streambutton. The StreamProperty view displays.

3. Change the name of the stream to Strip Air.

4. Double click on the Molar Flowcell and enter the followingstream compositions:

Saving your case

You can use one of several different methods to save a case in HYSYS:

From the File menu select Saveto save your case with thesame name.

Form the Filemenu select Save Asto save your case in adifferent location or with a different name.

Press the Savebutton on the button bar to save your case withthe same name.

Material Stream button (Blue)

For This Component Enter This Mole Fraction

Chloroform 0

Toluene 0

Ethanol 0

H2O 0

Oxygen 0.21

Nitrogen 0.79

Save your case often to avoidlosing information.

Save button

Save your case!


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Getting Started 17

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Flash CalculationsHYSYS can perform five types of flash calculations on streams: P-T,

Vf-P, Vf-T, P-Molar Enthalpy and T-Molar Enthalpy. Once the

composition of the stream and two of either temperature, pressure,

vapour fraction or molar enthalpy are known, HYSYS performs a flash

calculation on the stream, calculating the other two parameters.

With the flash capabilities of HYSYS, it is possible to perform dew andbubble point calculations. By specifying a vapour fraction of 1and

either the pressure or temperature of the stream, HYSYS will calculate

the dew temperature or pressure. To calculate the bubble temperature

or pressure, a vapour fraction of 0and either pressure or temperature

must be entered.

1. Perform a T-P flash calculation on the streamTol Rich. Set the pressure to 101.3 kPa (14.7 psia) andthe temperature to 90 C (200 F). What is the vapourfraction? __________

2. Perform a dew point calculation on the streamTol Rich. Set the pressure to 101.3 kPa (14.7 psia).

What is the dew point temperature? __________

3. Perform a bubble point calculation on the streamTol Rich. Set the pressure to 101.3 kPa (14.7 psia).What is the bubble point temperature? __________

Only 2 of these 4 streamparameters, Vapour Fraction,Temperature, PressureorMolar Enthalpycan besupplied.

If you try to supply temperature, pressure and vapourfraction, a consistency error can occur.


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18 Getting Started

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Attaching UtilitiesThe utilities available in HYSYS are a set of useful tools that interact

with your process, providing additional information or analysis of

streams or operations. Once installed, the utility becomes part of the

Flowsheet, automatically calculating when conditions change in the

stream or operation to which it is attached.

As with the majority of objects in HYSYS, there are a number of ways to

attach utilities to streams.

To Use the Do this

Menu Bar Select Utilitiesfrom the Toolsmenu.or

Press the hot key.

TheAvailable Utilitieswindow

displays.

Stream Property View Open the stream property view.

Switch to theAttachmentstab and

choose the Utilitiespage. Press the

Createbutton.

TheAvailable Utilitieswindow

displays.


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Getting Started 19

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Adding a Utility from the Stream PropertyView

The Property Tableutility allows you to examine property trends over a

range of conditions in both tabular and graphical formats. The utility

calculates dependent variables for up to two user specified

independent variable ranges or values.

A Property Table utility will be added to the stream Tol richfrom the

stream propertyview.

1. Use the hot key combination to open theAvailableUtilitieswindow.

2. Select Property Tablefrom the menu on the right and press theAdd Utilitybutton. The Property Tableview displays.

3. Press the Select Streambutton and select the stream Tol rich.

4. Press the OKbutton to return to the Ind. Proptab.

5. By default, Temperature is selected asVariable 1, and Pressure isselected asVariable 2.

6. Change the Lower Boundof the Temperature to 85 oC(185 oF)and change the Upper Boundto 100 oC(212 oF). Set the numberon increments to 5.

7. For the Pressure variable, use the drop down menu to change itsmode to State, and enter the following values: 90 kPa(13 psia),100 kPa (14.5 psia), 101.3 kPa (14.7 psia),110 kPa (16.0 psia), and120 kPa (17.4 psia).

8. Switch to the Dep. Proppage.


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20 Getting Started

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It is possible to choose multiple dependent properties for any of thesingle phases (liquid, aqueous or vapour) or for the bulk phase.

9. Select the Bulkradio button and highlight a cell in the Propertymatrix.

10. Choose Mass Densityfrom the drop down list.

11. Select the Liquidradio button, and select theViscosityproperty.

12. Select theAqueousradio button, and select theAq. Mass Fractionproperty.

13. Select the Vapourradio button, and select theVapour MassFractionproperty.

14. Press the Calculatecell to generate the Property Table.


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Getting Started 21

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You can examine the Property Table results in either graphical ortabular formats on the Performancetab.

Finishing the Simulation

The final step in this section is to add the stream information necessary

for the case to be used in future modules.

Add the following temperatures and pressures to the streams:

Add a flowrate of 18 000 kg/h(39, 700 lb/hr) to the stream Strip Air.

Examining the ResultsThe Stream Property View

Within HYSYS, it is possible to view the properties of the individual

phases for any stream.

1. Open the property view for the stream Tol Rich.

2. On theWorksheettab, Conditionspage, add a Temperaturevalue of 90C (195F) and supply a pressure of 101.3 kPa (14.7psia).

3. Move the mouse cursor to the left or right side of the view until

the cursor changes to resizing arrows.4. Press and hold the left mouse button and drag the edge of the

view until all the phases can be seen.

Pressure, kPa (psia) Temp., C (F)

Eth rich 101 kPa (14.7 psia) 15C (60F)

Tol rich 101 kPa (14.7 psia) 15C (60F)

Strip Air 101 kPa (14.7 psia) 25C (77F)


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The pages Propertiesand Compositionalso show data for the

individual phases.


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Getting Started 23

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Customizing the WorkbookHYSYS allows you to customize the Workbook at several different levels.

You can add additional pages, change the variables which are displayed

on the current pages, or change the format of the values which are

displayed.

In this exercise a new Workbook tab containing stream properties,Vap

Frac on a Mass Basis, Molecular Weight, Mass Density and Mass

Enthalpy, will be added.

1. Open the Workbook by pressing the Workbookbutton on the

button bar.

2. From theWorkbookmenu, select Setup. The Setupwindowdisplays.

3. Under theWorkbook Tabsgroup, press theAddbutton, and inthe view which appears, select +Streamand press OK.

4. A new Workbook tab, Streams 2, will be listed in theWorkbookTabsgroup. Ensure that this new tab is highlighted.

5. Highlight the Namecell in the Tab Contentsgroup, and changethe name to Other Prop.

6. In theVariablesgroup, press the Deletebutton until all thedefault variables are removed.

7. Click theAddbutton to view the list of variables grouped underthe Select Variable(s) For Mainpage.

8. From theVariableslist, selectVap Frac on a Mass Basisand clickOK.

Workbook button


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24 Getting Started

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9. Repeat 7 and 8 for Molecular Weight, Mass Density andMass Enthalpy.

10. Close this view to return to the Workbook.

The Workbook now contains the tab Other Propwhich shows the

vapour fraction on a mass basis, the molecular weight, the mass density

and the mass enthalpy for all the components for the three streams.


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Printing Stream and WorkbookDatasheets

In HYSYS you have the ability to print datasheets for Streams,

Operations and Workbooks.

Printing the Workbook Datasheet

1. Open the Workbook.

2. Right click (Object Inspect) the Workbook title bar. The PrintDatasheet orOpen Pagepop-up menu appears.

3. Select Print Datasheetand the Select Datablock(s) to Print forWorkbookwindow is displayed.

4. You can choose to print or preview any of the available datasheets(press the +collapse button to view all available datasheets).Clicking on the box will activate or deactivate the datasheet forprinting or previewing.

To print all streams:

Customize the Workbook to

contain all the stream info

you want.

Print the Workbook

Datasheet.


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Printing an Individual Stream DatasheetTo print the datasheet for an individual Stream, Object Inspect the

stream property view title bar and follow the same procedure as with

the Workbook.

Save your case!


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Getting Started 27

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Exercise 1

A. Use the Workbook to find the following values:

1. The dew point temperature of stream Eth Rich at 101 kPa(14.7 psia). __________

2. The bubble point pressure of stream Tol rich at 15C (60 F).__________

3. The dew point pressure of stream Strip Air at 25C (77 F).__________

4. The bubble point temperature of stream Strip Air at 101 kPa(14.7 psia). __________

B. Perform the following flash calculations:

1. The vapour fraction of stream Eth rich at 15C (60 F) and 101 kPa(14.7 psia). __________

2. The temperature of stream Tol rich at 101 kPa (14.7 psia) and 0.5vapour fraction. __________

3. What is the molar fraction of toluene in vapour phase for streamTol rich under the same condition? __________

4. The mass density of stream Strip Air at 25 C (77 F) and 101 kPa(14.7 psia). __________

5. The mass fraction of toluene in the aqueous phase of the stream"Tol rich" at 15 C (60 F) and 101.3 kPa (14.7 psia). __________

Exercise 2

The stream Eth Rich is stored in a 200 m3(7000 ft3) vessel. Assuming the

storage vessel has a 45 minute hold-up and the vessel is at atmospheric

conditions (1 atm, 25C, 77 F):

What is the composition of the vapor space? _________

How full is the storage vessel? __________


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Thermodynamics and HYSYS 1

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Thermodynamics and HYSYS

2000 AEA Technology plc - All Rights Reserved.

Chem 2_5.pdf


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2 Thermodynamics and HYSYS

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WorkshopOne of the main assets of HYSYS is its strong thermodynamic

foundation. Not only can you use a wide variety of internal property

packages, you can use tabular capabilities to override specific property

calculations for more accuracy over a narrow range. Or, you can use the

functionality provided through OLE to interact with externally

constructed property packages.

The built-in property packages in HYSYS provide accurate

thermodynamic, physical and transport property predictions for

hydrocarbon, non-hydrocarbon, petrochemical and chemical fluids.

The database consists of an excess of 1500 components and over 16000

fitted binary coefficients. If a library component cannot be found

within the database, a comprehensive selection of estimation methods

is available for creating fully defined hypothetical components.

HYSYS also contains a regression package within the tabular feature.

Experimental pure component data, which HYSYS provides for over

1000 components, can be used as input to the regression package.

Alternatively, you can supplement the existing data or supply a set of

your own data. The regression package will fit the input data to one of

the numerous mathematical expressions available in HYSYS. This will

allow you to obtain simulation results for specific thermophysical

properties that closely match your experimental data.

However, there are cases when the parameters calculated by HYSYS are

not accurate enough, or cases when the models used by HYSYS do not

predict the correct behaviour of some liquid-liquid mixtures

(azeotropic mixtures). For those cases it is recommended to use

another of Hyprotechs products, DISTIL. This powerful simulation

program provides an environment for exploration of thermodynamic

model behaviour, proper determination and tuning of interaction

parameters and physical properties, as well as alternative designs for

distillation systems.


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Proper use of thermodynamic property package parameters is key tosuccessfully simulating any chemical process. Effects of pressure and

temperature can drastically alter the accuracy of a simulation given

missing parameters or parameters fitted for different conditions.

HYSYS is user friendly by allowing quick viewing and changing of the

particular parameters associated with any of the property packages. In

addition, you are able to quickly check the results of one set of

parameters and compare those results with another set.

In this module, you will explore the thermodynamic packages of HYSYS

and the proper use of their thermodynamic parameters.

Learning ObjectivesOnce you have completed this module, you will be able to:

Select an appropriate Property Package

Understand the validity of each Activity Model

Enter new interaction parameters for a property package

Check multiphase behaviour of a stream

Understand the importance of properly regressed binarycoefficients


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Selecting Property PackagesThe property packages available in HYSYS allow you to predict

properties of mixtures ranging from well defined light hydrocarbon

systems to complex oil mixtures and highly non-ideal (non-electrolytic)

chemical systems. HYSYS provides enhanced equations of state (PR

and PRSV)for rigorous treatment of hydrocarbon systems; semi-

empirical and vapour pressure models for the heavier hydrocarbon

systems; steam correlations for accurate steam property predictions;

and activity coefficient models for chemical systems. All of these

equations have their own inherent limitations and you are encouraged

to become more familiar with the application of each equation.

The following table lists some typical systems and recommendedcorrelations:

Type of System Recommended Property Package

TEG Dehydration PR

Sour Water PR, Sour PR

Cryogenic Gas Processing PR, PRSV

Air Separation PR, PRSV

Atm Crude Towers PR, PR Options, GS

Vacuum Towers PR, PR Options, GS


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Equations of StateFor oil, gas and petrochemical applications, the Peng-Robinson EOS

(PR) is generally the recommended property package. HYSYS currently

offers the enhanced Peng-Robinson (PR) and Soave-Redlich-Kwong

(SRK) equations of state. In addition, HYSYS offers several methods

which are modifications of these property packages, including PRSV,

Zudkevitch Joffee (ZJ)and Kabadi Danner (KD). Lee Kesler Plocker

(LKP) is an adaptation of the Lee Kesler equations for mixtures, which

itself was modified from the BWRequation. Of these, the Peng-

Robinson equation of state supports the widest range of operating

conditions and the greatest variety of systems. The Peng-Robinson and

Soave-Redlich-Kwong equations of state (EOS) generate all required

equilibrium and thermodynamic properties directly. Although theforms of these EOS methods are common with other commercial

simulators, they have been significantly enhanced by Hyprotech to

extend their range of applicability.

The Peng-Robinson property package options are PR, SourPR, and PRSV.

Soave-Redlich-Kwong equation of state options are the SRK,Sour SRK, KDand ZJ.

For the Chemical industry due to the common occurrence of highly

non-ideal systems, the PRSV EOS may be considered. It is a two-fold

modification of the PR equation of state that extends the application of

the original PR method for highly non-ideal systems.

It has shown to match vapour pressure curves of purecomponents and mixtures, especially at low vapour pressures.

It has been successfully extended to handle non-ideal systemsgiving results as good as those obtained by activity models.

A limited amount of non-hydrocarbon interaction parametersare available.

Activity Models

Although equation of state models have proven to be very reliable in

predicting properties of most hydrocarbon based fluids over a large

range of operating conditions, their application has been limited toprimarily non-polar or slightly polar components. Polar or non-ideal

chemical systems have traditionally been handled using dual model

approaches.

Activity Models are much more empirical in nature when compared to


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the property predictions in the hydrocarbon industry. For example,they cannot be used as reliably as the equations of state for generalized

application or extrapolating into untested operating conditions. Their

tuning parameters should be fitted against a representative sample of

experimental data and their application should be limited to moderate

pressures.

For every component i in the mixture, the condition of

thermodynamics equilibrium is given by the equality between the

fugacities of the liquid phase and vapour phase. This feature gives the

flexibility to use separate thermodynamic models for the liquid and gas

phases, so the fugacities for each phase have different forms. In this

approach:

an equation of state is used for predicting the vapour fugacitycoefficients (normally ideal gas assumption or the RedlichKwong, Peng-Robinson or SRK equations of state, although aVirial equation of state is available for specific applications)

an activity coefficient model is used for the liquid phase.

Although there is considerable research being conducted to extend

equation of state applications into the chemical industry (e.g., PRSV

equation), the state of the art of property predictions for chemical

systems is still governed mainly by Activity Models.

Activity coefficients are fudge factors applied to the ideal solution

hypothesis (Raoults Law in its simplest form) to allow the development

of models which actually represent real data. Although they are fudgefactors, activity coefficients have an exact thermodynamic meaning as

the ratio of the fugacity coefficient of a component in a mixture at P and

T, and the fugacity coefficient of the pure component at the same P and

T. Consequently, more caution should be exercised when selecting these

models for your simulation.

Activity Models produce thebest results when they areapplied in the operatingregion for which theinteraction parameters wereregressed.


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The following table briefly summarizes recommended activitycoefficient models for different applications (refer to the bulleted

reference guide below):

A= Applicable

N/A= Not Applicable

?= Questionable

G= Good

LA= Limited Application

Application Margules van Laar Wilson NRTL UNIQUAC

Binary Systems A A A A A

Multicomponent

Systems

LA LA A A A

Azeotropic Systems A A A A A

Liquid-Liquid

Equilibria

A A N/A A A

Dilute Systems ? ? A A A

Self-Associating

Systems

? ? A A A

Polymers N/A N/A N/A N/A A

Extrapolation ? ? G G G


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Overview of Models

Margules

One of the earliest activity coefficient expressions was proposed by

Margules at the end of the 19th century.

The Margules equation was the first Gibbs excess energyrepresentation developed.

The equation does not have any theoretical basis, but is usefulfor quick estimates and data interpolation.

In its simplest form, it has just one adjustable parameter andcan represent mixtures which feature symmetric activity

coefficient curves.

HYSYS has an extended multicomponent Margules equation with up to

four adjustable parameters per binary. The four adjustable parameters

for the Margules equation in HYSYS are the aijand aji(temperature

independent) and the bij and bjiterms (temperature dependent).

The equation will use parameter values stored in HYSYS orany user supplied value for further fitting the equation to agiven set of data.

In HYSYS, the equation is empirically extended and thereforecaution should be exercised when handling multicomponentmixtures.

van Laar

The van Laar equation was the first Gibbs excess energy representation

with physical significance. This equation fits many systems quite well,

particularly for LLE component distributions. It can be used for

systems that exhibit positive or negative deviations from Raoults Law.

Some of the advantages and disadvantage for this model are:

Generally requires less CPU time than other activity models.

It can represent limited miscibility as well as three phaseequilibrium.

It cannot predict maxima or minima in the activity coefficientand therefore, generally performs poorly for systems with

halogenated hydrocarbons and alcohols. It also has a tendency to predict two liquid phases when they

do not exist.

The Margules equation shouldnot be used for extrapolationbeyond the range over whichthe energy parameters havebeen fitted.

The van Laar equationperforms poorly for dilutesystems and CANNOTrepresent many commonsystems, such as alcohol-hydrocarbon mixtures, withacceptable accuracy.


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The van Laar equation implemented in HYSYS has two parameters withlinear temperature dependency, thus making it a four parameter

model. In HYSYS, the equation is empirically extended and therefore its

use should be avoided when handling multicomponent mixtures.

Wilson

The Wilson equation, proposed by Grant M. Wilson in 1964, was the

first activity coefficient equation that used the local composition model

to derive the Gibbs Excess energy expression. It offers a

thermodynamically consistent approach to predicting multi-

component behaviour from regressed binary equilibrium data.

Although the Wilson equation is more complex and requiresmore CPU time than either the van Laar or Margulesequations, it can represent almost all non-ideal liquid solutionssatisfactorily except electrolytes and solutions exhibiting limitedmiscibility (LLE or VLLE).

It performs an excellent job of predicting ternary equilibriumusing parameters regressed from binary data only.

It will give similar results to the Margules and van Laarequations for weak non-ideal systems, but consistentlyoutperforms them for increasingly non-ideal systems.

It cannot predict liquid-liquid phase splitting and thereforeshould only be used on problems where demixing is not anissue.

Our experience shows that the Wilson equation can be extrapolatedwith reasonable confidence to other operating regions with the same

set of regressed energy parameters.

NRTL

The NRTL (Non-Random-Two-Liquid) equation, proposed by Renon

and Prausnitz in 1968, is an extension of the original Wilson equation. It

uses statistical mechanics and the liquid cell theory to represent the

liquid structure. These concepts, combined with Wilsons local

composition model, produce an equation capable of representing VLE,

LLE, and VLLE phase behaviour. Like the Wilson equation, the NRTL

model is thermodynamically consistent and can be applied to ternary

and higher order systems using parameters regressed from binary

equilibrium data. The NRTL model has an accuracy comparable to the

Wilson equation for VLE systems.

The NRTL combines the advantages of the Wilson and vanLaar equations.

The Wilson equation CANNOTbe used for problems involvingliquid-liquid equilibrium.

The additional parameter inthe NRTL equation, called thealpha term, or non-randomness parameter,represents the inverse of the

coordination number ofmolecule i surrounded bymolecules j. Since liquidsusually have a coordinationnumber between 3 and 6, youmight expect the alphaparameter between 0.17 and0.33.


38


10

It is not extremely CPU intensive. It can represent LLE quite well.

However, because of the mathematical structure of the NRTLequation, it can produce erroneous multiple miscibility gaps.

The NRTL equation in HYSYS contains five adjustable parameters

(temperature dependent and independent) for fitting per binary pair.

UNIQUAC

The UNIQUAC (UNIversal QUAsi Chemical) equation proposed by

Abrams and Prausnitz in 1975 uses statistical mechanics and the quasi-

chemical theory of Guggenheim to represent the liquid structure. The

equation is capable of representing LLE, VLE and VLLE with accuracycomparable to the NRTL equation, but without the need for a non-

randomness factor, it is a two parameter model.

The UNIQUAC equation is significantly more detailed and

sophisticated than any of the other activity models.

Its main advantage is that a good representation of both VLEand LLE can be obtained for a large range of non-electrolytemixtures using only two adjustable parameters per binary.

The fitted parameters usually exhibit a smaller temperaturedependence which makes them more valid for extrapolationpurposes.

The UNIQUAC equation utilizes the concept of localcomposition as proposed by Wilson. Since the primaryconcentration variable is a surface fraction as opposed to amole fraction, it is applicable to systems containing moleculesof very different sizes and shape, such as polymer solutions.

The UNIQUAC equation can be applied to a wide range ofmixtures containing H2O, alcohols, nitriles, amines, esters,ketones, aldehydes, halogenated hydrocarbons andhydrocarbons.

In its simplest form it is a two parameter model, with the same remarks

as Wilson and NRTL. UNIQUAC needs van der Waals area and volume

parameters, and those can sometimes be difficult to find, especially for

non-condensable gases (although DIPPR has a fair number available).

Extended and General NRTL

The Extended and General NRTL models are variations of the NRTL

model, simple NRTL with a complex temperature dependency for the

aijand ajiterms. Apply either model to systems:


39


11

with a wide boiling point range between components where you require simultaneous solution of VLE and LLE, andthere exists a wide boiling range or concentration rangebetween components

Extreme caution must be exercised when extrapolating beyond the

temperature and pressure ranges used in regression of parameters. Due

to the larger number of parameters used in fitting, inaccurate results

can be obtained outside the original bounds.

Chien-Null

Chien-Null is an empirical model designed to allow you to mix and

match models which were created using different methods andcombined into a multicomponent expression. The Chien-Null model

provides a consistent framework for applying existing activity models

on a binary by binary basis. In this manner, Chien-Null allows you to

select the best activity model for each pair in the case. For example,

Chien-Null can allow the user to have a binary defined using NRTL,

another using Margules and another using van Laar, and combine them

to perform a three component calculation, mixing three different

thermodynamic models.

The Chien Null model allows 3 sets of coefficients for each component

pair, accessible via theA, Band Ccoefficient matrices.

Henrys Law

Henrys Law cannot be selected explicitly as a property method in

HYSYS. However, HYSYS will use Henrys Law when an activity model is

selected and "non-condensable" components are included within the

component list.

HYSYS considers the following components non-condensable:

Methane, Ethane, Ethylene, Acetylene, Hydrogen, Helium, Argon,

Nitrogen, Oxygen, NO, H2S, CO2, and CO.

The general NRTL model isparticularly susceptible toinaccuracies if the model isused outside of the intendedrange.

Care must be taken to ensurethat you are operating withinthe bounds of the model.

The Thermodynamics appendix in the HYSYS User Manualprovides more information on Property Packages,Equations of State, and Activity Models, and the equationsfor each.

No interaction between "non-condensable" componentpairs is taken into account inthe VLE calculations.


40


12

The extended Henrys Law equation in HYSYS is used to model dilutesolute/solvent interactions. "Non-condensable" components are

defined as those components that have critical temperatures below the

system temperature.

Activity Model Vapour Phase Options

There are several methods available for calculating the Vapour Phase in

conjunction with the selected liquid activity model. The choice will

depend on specific considerations of your system.

Ideal

The ideal gas law can be used to model the vapour phase. This model is

appropriate for low pressures and for a vapour phase with little

intermolecular interaction. The model is the default vapour phase

fugacity calculation method for activity coefficient models.

Peng Robinson, SRK or RK

To model non-idealities in the vapour phase, the PR, SRK, or RK

options can be used in conjunction with an activity model.

PR and SRK vapour phase models handle the same types ofsituations as the PR and SRK equations of state.

When selecting one of these three models, ensure that thebinary interaction parameters used for the activity modelremain applicable with the chosen vapour model.

For applications with compressors and turbines, PR or SRKwillbe superior to the RK or Ideal vapour model.

Virial

TheVirial option enables you to better model vapour phase fugacities

of systems displaying strong vapour phase interactions. Typically this

occurs in systems containing carboxylic acids, or compounds that have

the tendency to form stable H2 bonds in the vapour phase.

HYSYS contains temperature dependent coefficients for carboxylicacids. You can overwrite these by changing the Association (ij) or

Solvation (ii) coefficients from the default values.

This option is restricted to systems where the density is moderate,

typically less than one-half the critical density.

Care should be exercised inchoosing PR, SRK, RV or Virialto ensure binary coefficientshave been regressed with thecorresponding vapour phasemodel.


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13

Binary CoefficientsFor the Property Packages which do include binary coefficients, the

Binary Coefficientstab contains a matrix which lists the interaction

parameters for each component pair. Depending on the property

method chosen, different estimation methods may be available and a

different view may be shown. You have the option of overwriting any

library value.

Equation of State Interaction Parameters

The Equation of State Interaction Parameters group appears as follows

on the Binary Coeffstab when an EOSis the selected property package:

For all EOS parameters (except PRSV),

Kij= Kji

so when you change the value of one of these, both cells of the pair

automatically update with the same value. In many cases, the library

interaction parameters for PRSV do have Kij= Kji, but HYSYS does not

force this if you modify one parameter in a binary pair.

The numbers appearing in thematrix are initially calculatedby HYSYS, but you have theoption of overwriting anylibrary value.


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14

If you are using PRor SRK(or one of the Sour options), two radiobuttons are displayed at the bottom of the page in the Treatment of

Interaction Coefficients Unavailable from the Library group:

Estimate HC-HC/Set Non HC-HC to 0.0 this radio button isthe default selection. HYSYS provides the estimates for theinteraction parameters in the matrix, setting all non-hydrocarbon pairs to 0.

Set All to 0.0 when this is selected, HYSYS sets allinteraction parameter values in the matrix to 0.0.

Activity Model Interaction Parameters

Activity Models are much more empirical in nature when compared to

the property predictions in the hydrocarbon industry. Their tuning

parameters should be fitted against a representative sample of

experimental data and their application should be limited to moderate

pressures.

TheActivity Model Interaction Parametersgroup appears as follows

on the Binary Coeffstab when anActivity Modelis the selected

property package:

The interaction parameters for each binary pair will be displayed. You

can overwrite any value or use one of the estimation methods.

Note that the Kij= Kjirule does not apply to Activity Model interaction

parameters.


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15

Estimation MethodsWhen using Activity Models, HYSYS provides three interaction

parameter estimation methods. Select the estimation method by

choosing one of the radio buttons in the Coeff Estimationwindow. The

options are:

UNIFAC VLE

UNIFAC LLE

Immiscible

You can then invoke the estimation by selecting one of the available

cells.

For UNIFAC methods the options are:

Individual Pair calculates the parameters for the selectedcomponent pair, Aijand Aji. The existing values in the matrixare overwritten.

Unknowns Only calculates the activity parameters for all theunknown pairs. If you delete the contents of cells or if HYSYSdoes not provide default values, you can use this option.

All Binaries recalculates all the binaries of the matrix. If youhad changed some of the original HYSYS values, you coulduse this to have HYSYS re-estimate the entire matrix.

.

For the Immiscible method the options are:

Row in Clm pair estimates the parameters such that the rowcomponent (j) is immiscible in the column component (i).

Clm in Row pair estimates parameters such that the column

component (j) is immiscible in the row component (i). All in Row estimates parameters such that both componentsare mutually immiscible.

In Module 1, you chose the NRTLActivity Model, then select the

UNIFAC VLEestimation method (default) before pressing the

Unknowns Onlycell.

When theAll Binariesbutton is used, HYSYS does notreturn the original library values. Estimation values will bereturned using the selected UNIFAC method. To return tothe original library values, you must select a new propertymethod and then re-select the original property method

The UNIFAC (UNIquac group-Functional ActivityCoefficient) method is a groupcontribution technique usingthe UNIQUAC model as thestarting point to estimatebinary coefficients. This,however, should be a lastsolution as it is preferable totry and find values estimatedfrom experimental data.


44


16

Which Activity Coefficient ModelShould I Use?

This is a tough question to answer, but some guidelines are provided. If

you require additional assistance, it is best to contact Hyprotechs

Technical Support department.

Basic Data

Activity coefficient models are empirical by nature and the quality of

their prediction depends on the quality and range of data used to

determine the parameters. Some important things you should be aware

of in HYSYS.

The parameters built in HYSYS were fitted at 1 atm whereverpossible, or were fitted using isothermal data which wouldproduce pressures closest to 1 atm. They are good for a firstdesign, but always look for experimental data closer to theregion you are working in to confirm your results.

The values in the HYSYS component database are defined forVLE only, hence the LLE prediction may not be very good andadditional fitting is necessary.

Data used in the determination of built in interactionparameters very rarely goes below 0.01 mole fraction, andextrapolating into the ppm or ppb region can be risky.

Again, because the interaction parameters were calculated atmodest pressures, usually 1 atm, they may be inadequate forprocesses at high pressures.

Check the accuracy of the model for azeotropic systems.Additional fitting may be required to match the azeotrope withacceptable accuracy. Check not only for the temperature, butfor the composition as well.

If three phase behaviour is suspected, additional fitting of theparameters may be required to reliably reproduce the VLLEequilibrium conditions.

UNIFAC or no UNIFAC?

UNIFAC is a handy tool to give initial estimates for activity coefficient

models. Nevertheless keep in mind the following:

Group contribution methods are always approximate and theyare not substitutions for experimental data.

UNIFAC was designed using relatively low molecular weightcondensable components (thus high boilers may not be wellrepresented), using temperatures between 0-150 oC and dataat modest pressures.


45


17

Generally, UNIFAC does not provide good predictions for thedilute region.

Choosing an Activity Model

Again, some general guidelines to consider.

Margulesor vanLaar- generally chosen if computation speedis a consideration. With the computers we have today, this isusually not an issue. May also be chosen if some preliminarywork has been done using one of these models.

Wilson- generally chosen if the system does not exhibit phasesplitting.

NRTLor UNIQUAC- generally chosen if the system exhibitsphase splitting.

GeneralNRTL- should only be used if an abundant amount ofdata over a wide temperature range was used to define itsparameters. Otherwise it will provide the same modellingpower as NRTL.

Exploring with the SimulationProper use of thermodynamic property package parameters is key to

successfully simulating any chemical process. Effects of pressure andtemperature can drastically alter the accuracy of a simulation given

missing parameters or parameters fitted for different conditions.

HYSYS is user friendly in allowing quick viewing and changing of the

particular parameters associated with any of the property packages.

Additionally, the user is able to quickly check the results of one set of

parameters and compare against another.


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18

Exercise 1

Di-iso-Propyl-Ether/H2O Binary

This example effectively demonstrates the need for having interaction

parameters. Do the following:

1. Open case DIIPE.hsc.

2. Enter the following conditions for stream DIIPE/H2O:

3. Close the stream view and press the Enter Basis Environmentbutton.

4. Select the Binary Coeffstab of the Fluid Package. Notice that theinteraction parameters for the binary are both set to 0.0.

5. Press the Reset Paramsbutton to recall the default NRTL activitycoefficient model interaction parameters.

6. Close the Fluid Package view.

7. Return to the simulation environment by pressing the Return toSimulation Environmentbutton.

8. Open the stream view by double clicking on the stream DIIPE/H2O.

Conditions

Vapour Fraction 0.0

Pressure 1 atm

Molar Flow 1 kgmole/h (1 lbmole/hr)

Composition

di-i-P-Ether 50 mole %

H2O 50 mole %

What phases are present? __________

What phases are now present? __________

What is the composition of each? __________


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19

Clearly, it can be seen how important it is to have interactionparameters for the thermodynamic model. The xy phase diagrams on

the next page (figures 1 and 2) illustrate the homogeneous behaviour

when no parameters are available and the heterogeneous azeotropic

behaviour when properly fitted parameters are used. The majority of

the default interaction parameters for activity coefficient models in

HYSYS have been regressed based on VLE data from DECHEMA,

Chemistry Data Services.


48


20

Fig. 1 - Interaction Parameters set to 0.

Fig. 2 - Using the Default HYSYS Interaction Parameters.


49


21

Exercise 2

Phenol/H2O Binary

This binary shows the importance of ensuring that properly fitted

interaction parameters for the conditions of your simulation are used.

The default parameters for the Phenol/H2O system have been

regressed from the DECHEMA Chemistry data series and provide very

accurate vapour-liquid equilibrium since the original data source (1)

was in this format. However, the Phenol/Water system is also shown to

exhibit liquid-liquid behaviour (2). A set of interaction parameters can

be obtained from sources such as DECHEMA and entered into HYSYS.

The following example illustrates the poor LLE prediction than can be

produced by comparing the results using default interaction

parameters and specially regressed LLE parameters.

1. Open the case Phenolh2o.hsc.

2. Enter the following conditions for stream Phenol/H2O:

Conditions

Temperature 40C

Pressure 1 atm

Molar Flow 1 kgmole/h (1 lbmole/hr)

Composition

Phenol 25 mole %

H2O 75 mole %

What phase(s) are present? __________


50


22

To provide a better prediction for LLE at 40

o

C (105

o

F) the following Aijinteraction parameters are to be entered. To enter the parameters do

the following:

1. Close the stream view and press the Enter Basis Environmentbutton.

2. Ensure the Fluid Package view is open and select the BinaryCoeffstab.

3. Enter the A ijinteraction parameters as shown here:

4. Select theAlphaij/Cijradio button.

5. Enter an Alphaij= 0.2.


7. Return to the simulation environment by pressing the Return toSimulation Environmentbutton.

8. Open the stream view for Phenol/H2O.

The figures on the following page (figures 3 and 4) show the difference

between the two sets of interaction parameters. Therefore, care must be

exercised when simulating LLE as almost all the default interactionparameters for the activity coefficient models in HYSYS are for VLE.

What phase(s) are present now? __________

What are the compositions? __________


51


23

Fig. 3 - Using the Default (VLE) Interaction Parameters.

Fig. 4 - Using the Fitted (LLE Optimizied) Interaction Parameters.


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24

Exercise 3

Benzene/Cyclohexane/H2O Ternary

This example again illustrates the importance of having interaction

parameters and also discusses how the user can obtain parameters

from regression. To illustrate the principles do the following:

1. Open the case Ternary.hsc.

2. Enter the following stream conditions for Benzene/CC6/H2O:

To provide a more precise simulation the missing CC6/H2O interaction

parameter has to be obtained. Fortunately, some data is available at

25C giving the liquid-liquid equilibrium between CC6 and H2O. Using

this data, and the regression capabilities within DISTIL, an AEA

Technology Engineering Software conceptual design and

thermodynamic regression product, you can obtain new interaction

parameters. The temperature dependent Bij parameters are to be left at

0 and the alphaijterm is to be set to 0.2for the CC6/H2O. To implement

these parameters, proceed with the steps on the following page.

Conditions

Temperature 25C

Pressure 1 atm

Composition

Benzene 20 mole %

H2O 20 mole %

CC6 60 mole %

How many phases are present? __________


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25

1. Return to the Basis Environment by pressing the Enter BasisEnvironment button.

2. Open the Fluid Package view and move to the Binary Coeffstab.

3. Enter the data in the Aij matrix as shown here:

4. Select theAlphaij/Cijradio button.

5. Enter a CC6/H2O alphaij value of 0.2.


7. Return to the Simulation Environment.

8. Open the stream Benzene/CC6/H2O.

The figures on the following page (figures 5 and 6) clearly show the

behaviour of the ternary system. Without the regressed CC6/H2O

binary, the thermodynamic property package incorrectly predicts the

system to be miscible at higher CC6 concentrations. This prediction is

correct given properly regressed CC6/H2O parameters.

References

1. Schreinemakers F.A.H., Z. Phys. Chem.35, 459 (1900).

2. Hill A.E. and Malisoff W.M., J.Am. Chem. Soc.

48 (1926) 918.

How many phases are now present? __________

What are the compositions? __________


54


26

Fig. 5 - Without Regressed CC6/H2O Interaction Parameters.

Fig. 6 - With Regressed CC6/H2O Interaction Parameters.


55

Flowsheeting 1

1

Flowsheeting



56

2 Flowsheeting

2

WorkshopIn evaporation, a solution consisting of a non-volatile solute and a

volatile solvent is concentrated by the addition of heat. In multiple

effect evaporation, the volatile solvent recovered from the first

evaporator is condensed and used as a heat source for the next

evaporator. This means that the second evaporator must operate at a

lower temperature and pressure than the first evaporator.

In this module you will simulate a series of three evaporators to

concentrate a solution of sucrose/water. Each evaporator is modelled

using a flash tank. You will convert the completed simulation to a

template, making it available to connect to other simulations.

On the next page, a Process Overview is shown. This represents the

actual process. On the third page a Simulation PFD is shown. This

represents the simulation as you will build it in this module. Building

the simulation in this way allows more flexibility in the design.

Learning Objectives

Once you have completed this section, you will be able to:

Add and connect operations to build a Flowsheet

Add and use logical operations, Sets and Adjusts

Use the graphical interface to manipulate flowsheets in HYSYS

Understand information propagation in HYSYS

Convert HYSYS flowsheet to templates

PrerequisitesBefore beginning this section you need to know how to:

Define a Fluid Package

Define Streams

Navigate the Workbook interface


57

Process Overview


58

Simulation PFD


59

Flowsheeting 5

5

Building the SimulationThe first step to building any simulation is defining a Fluid Package. A

brief recap on how to define a Fluid Package and install streams is

described below. For a complete description see: Defining the

Simulation Basis, Module 1.

Defining the Simulation Basis

1. Start a New Case and add a Fluid Package.

2. UseWilson/Idealas the Property Package with the components

Sucroseand H2O.

3. Move to the Binary Coefficients page. Notice that the interactionparameters for Aijand Bijare empty.

The program warns you that the binary coefficients have not been

determined and the model will assume values of zero. Answer OKto

this message. Enter the Simulation Environment.

The Wilson equation cannotbe used for problems involving

liquid-liquid equilibrium.


60

6 Flowsheeting

6

4. Add a stream with the following values.

5. Add a second stream with the following properties:

In this cell Enter

Name Feed

Vapour Fraction 0

Pressure 101.3 kPa (14.7 psia)

Flowrate 50 kg/h (110 lb/hr)

Mass Fraction Surcose 0.3

Mass Fraction H2O 0.7

Note that the compositionvalues for this stream are inMassfractions. Double-clickon the Mass Flow cell to enterthese values.

In this cell Enter

Name Steam

Vapour Fraction 1.0

Pressure 275 kPa (40 psia)

Mass fraction H2O 1.0

What is the temperature of stream Feed? __________

What is the temperature of stream Steam? __________


61

Flowsheeting 7

7

Adding Unit Operations to a FlowsheetAs with streams, there are a variety of ways to add Unit Operations in

HYSYS:

The Triple Effect Evaporator consists of six operations:

A series of three evaporators modelled as flash tanks (2 Phaseseparators)

Three coolers

In this exercise, you will add each operation using a different method of

installation.

To use the Do this

Menu Bar SelectAdd Operationfrom the

Flowsheetmenu.

Or

Press the hot key.

The UnitOpswindow displays.

Workbook Open the Workbook and go to the

UnitOpspage, then click theAdd

UnitOpbutton.

The UnitOpswindow displays.

Object Palette Select Object Palettefrom the

Flowsheetmenu or press to

open the Object Palette and double

click the icon of the Unit Operation

you want to add.

PFD/Object Palette Using the right mouse button,

dragndrop the icon from the Object

Palette to the PFD.


62

8 Flowsheeting

8

Adding a Separator

The Evaporator is modelled using a Separator in HYSYS.

The Separator will be added using the hot key.

1. Press the hot key. The UnitOpswindow displays:

2. Select Separatorfrom theAvailable Unit Operationslist.

3. Press theAddbutton. The Separator property view displays.

4. On the Connectionspage enter the data as shown here:

Note: Drop down boxes, such as for Feedand Productstreams, containlists of available streams which can be connected to the operation.


63

Flowsheeting 9

9

Adding a CoolerAdd the first Cooler using the same method.

1. Press the hot key

2. The UnitOps window displays. Click the Category Heat TransferEquipmentand select Cooler.

3. Press theAddbutton. The Cooler property view displays.

4. On the Connectionspage enter the information as shown below:

5. Go to the Parameterspage.


64

10 Flowsheeting

10

6. Enter a value of 0 kPa(0 psi) for the Pressure Drop.

7. Go to theWorksheettab.

8. Specify aVapour Fractionof 0for the stream Condensate.

To completely define the separation we need to provide an energy flow.

9. On the Worksheet tab, enter a value of 2.42e4 kJ/h(2.29e4 Btu/hr)for the Energy stream q1.

What is the flowrate of Water in the stream L1? __________

What is the temperature of the stream V1? __________

What is the mass flow of steam through the Cooler?__________


65

Flowsheeting 11

11

Add the Second CoolerThis procedure describes how to add Unit Operations using the

UnitOpspage of the Workbook.

1. Open the Workbook and click the UnitOps tab.

2. Click theAdd UnitOpbutton. The UnitOpswindow displays:

3. Select Heat Transfer Equipmentfrom the Categoriesgroup.

4. Select Coolerfrom theAvailable Unit Operations list.

5. Press theAddbutton. The Coolerproperty view displays.

6. On the Connectionspage enter the information as shown below:

7. On the Parameterspage specify a Pressure Dropof 0 kPa (0 psi).8. Go to theWorksheettab and specify theVapour Fractionof the

stream C2as 0. Close this view.

What is the Heat Flow for stream q2? __________


66

12 Flowsheeting

12

Add Another SeparatorThis procedure describes how to add a Separator using the Object

Palette. The Object Palette contains icons for all the Streams and Unit

Operations in HYSYS.

1. Press the hot key. The Object Palette displays:

2. Double click the Separatorbutton on the Object Palette. TheSeparator property view displays.

Separator button


67

Flowsheeting 13

13

3. On the Connectionspage enter the stream information as shownhere:

4. On the Parameterspage, delete the pressure drop specification.The Separator should become unsolved; Unknown Delta P.


68

14 Flowsheeting

14

Add a Set OperationThe Set Operation is a steady-state logical operation used to set the

value of a specific Process Variable (PV) in relation to another PV. The

relationship is between the same PV in two like objects -- for instance,

the temperature of two streams, or the UA of two exchangers.

In order for the energy to flow from Cooler 2 to Effect 2, the Separator

outlet temperature must be cooler then the condensate from the

Cooler. A Set operation will be used to maintain this relationship.

1. Add a Setoperation by double-clicking on the Set icon in theobject palette.

2. Complete the Connectionspage as shown here:

3. Go to the Parameterstab. Complete the view as shown below, ifusing field units the value for the offset will be -5 oF:

What is the Delta P of Effect 2? __________

Set operation button


69

Flowsheeting 15

15

Add the Third CoolerWorking with a graphical representation, you can build your flowsheet

in the PFD using the mouse to install and connect objects. This

procedure describes how to install and connect the Cooler using the

Object Palette Dragndrop technique.

To DragnDrop in the PFD:

1. Press the Coolerbutton on the Object Palette.

2. Move the cursor to the PFD. The cursor will change to a specialcursor, with a box and a plus (+) symbol attached to it. The boxindicates the size and location of the cooler icon.

3. Click the left mouse button to drop the Cooler onto the PFD.

There are two ways to connect the operation to a stream on the PFD:

To connect using the Do this

Attach Modetoggle button

Insert Icon

Press theAttach Modetoggle button.

Place the cursor over the operation.

The Feed stream connection point is

highlighted in dark blue.

Move the cursor over the stream you

want to connect.

Press and hold the left mouse

button.

Move the cursor to the operation

icon and release the mouse button.

key Press and hold the key and

pass the cursor over the operation.

Place the cursor over the stream you

want to connect.

Press and hold the left mouse

button.

Move the cursor to the operation

icon and release the mouse button

and the key.


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16 Flowsheeting

16

4. Double click on the Cooler icon on the PFD. The Cooler propertyview displays. Enter the data shown below:

5. On the Parameterspage specify a Pressure Dropof 0 kPa (0 psi).

6. Go to theWorksheettab and specify theVapour Fractionof thestream C3as 0. Close this view.

Add the Third Separator

1. Drag n drop the Separatoronto the PFD. Connect the stream L2as the Feed to the Separator.

2. Double click on the Separator. Make the following connections:

3. On the Parameters page delete the pressure drop specification.


71

Flowsheeting 17

17

Set Operation1. Add a Setoperation and complete the Connectionspage as

shown here:

2. On the Parameterstab enter a value of 3 C (-5F)as the Offset,and 1.0for the Multiplier.


72

18 Flowsheeting

18

Add an AdjustThe Adjust operation is a Logical Operation - a mathematical operation

rather than a physical operation. It will vary the value of one stream

variable (the independent variable) to meet a required value or

specification (the dependant variable) in another stream or operation.

It is desired to reach 15 weight% water in stream L3. The only

parameter we have to manipulate this variable is the energy supplied to

the first Effect. To meet a target concentration in L3 we can use an

Adjust operation.

1. Add theAdjustoperation. The Adjust property view displays.

2. Press the Select Varbutton in theAdjusted Variablegroup toopen theVariable Navigator.

3. From the Objectlist select q1. From theVariablelist which is nowvisible, select Heat Flow.

4. Press the OKcell to accept the variable and return to theAdjustproperty view.

5. Press the Select Varbutton in the Target Variablegroup.

What is the weight percent of Water in stream L3?__________

Adjust button

The adjusted variable mustalways be a user specifiedvalue.

Always work left to right in theVariable Navigator. Dontforget you can use the ObjectFilter when the Object list islarge.


73

Flowsheeting 19

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6. Select L3 and Comp Mass Frac (H2O)as the target variable.7. On the Connectionspage, enter a value of 0.15in the Specified

Target Valuebox.

The completed Connectionspage is shown below.

8. Switch to the Parameterstab, and enter 2000 kJ/h (1900 Btu/hr)as the Step Size.

9. Press the Startbutton to begin calculations.Note: once the case issolved (OK status), this button will disappear from the propertyview.

10. To view the progress of the Adjust, go to the Monitortab.

When adjusting certainvariables, it is often a goodidea to provide a minimum ormaximum which correspondsto a physical boundary, such

as zero for pressure or flow.

Note the Toleranceand StepSize values. When consideringstep sizes, use larger ratherthan smaller sizes. The Secantmethod works best once thesolution has been bracketedand by using a larger step size,you are more likely to bracketthe solution quickly.


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If you enter a step size too large for the energy HYSYS will not calculate

because all the liquid has been flashed. You need to decrease the step

size, enter a new value for q1 and restart the simulation.

Note that HYSYS does not predict the formation of solids; this will have

to be verified separately.

Manipulating the PFDThe PFD is designed around using the mouse and/or keyboard. There

are a number of instances in which either the mouse or the keyboard

can be used to perform the same function. One very important PFD

function for which the keyboard cannot be used is Object Inspection.

You can perform many of the tasks and manipulations on the icons in

the PFD by using Object Inspection. Place the mouse pointer over the

icon you wish to inspect and press the secondary mouse button. Anappropriate menu is produced depending upon the icon selected

(Stream, Operation, Column, or Text Annotation).

A list of the objects which you can Object Inspect are shown below with

What is the energy required to achieve a concentration of85 wt% of sucrose in the product stream? __________


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the corresponding menus.

Object... Object Inspection Menu...

PFD

Unit Operations

Streams


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Customize the PFD by performing the following:

1. Add a Title, Triple Effect Evaporator.

2. Add aWorkbook Tablefor the Material Streams in the simulation.

3. Add a Tablefor stream L3.

Adding Unit Operation Information tothe Workbook

Each WorkBook has a UnitOpspage by default that displays all the Unit

Operations and their connections in the simulation. You can add

additional pages for specific Unit Operations to the WorkBook. For

example, you can add a page to the WorkBook to contain only Coolers

in the simulation.

To add a Unit Operation tab to theWorkBook:

1. Open theWorkbook.

2. In the Menu Bar, selectWorkbook, and then Setup.

3. In the Setupview, press theAddbutton in the UnitOpsgroup.

4. From the New Object Typeview, select Heat TransferEquipment, thenCooler.

5. Click OK. A new page, Cooler, containing only Cooler informationis added to the WorkBook.

Double clicking on a title witha "+" sign will open anexpanded menu.


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Adding Unit Operation Information tothe PFD

For each Unit Operation, you can display a Property Table on the PFD.

The Property Table contains certain default information about the Unit

Operation.

Add Unit Operation information to the PFD:

1. Open the PFD.

2. Select the Separator Effect 1.

3. Object Inspect the Unit Operation.

4. Select Show Tablefrom the menu.

5. TheVessel Temperature, Pressure, Liquid Molar Flow, and Dutyare shown as defaults in the table. Object Inspect the table andinsert theVapour Mass Flow.

6. Create two tables for the streams Feedand L3showing theComponent Mass Fractionof Sucrose and the Mass Flow.

Remember you can ObjectInspect an object by selecting itand then clicking on it withthe right mouse button.

Save your case!


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Exploring with the SimulationExercise 1

Try running the case for different final sucrose concentrations. Can you

find any cases in which the program does not solve?

Watch for cases when the Adjust block takes too large of a step in energy,

causing all of the liquid to be flashed.


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Saving the Simulation as a TemplateA template is a complete Flowsheet that has been stored to disk with

some additional information included that pertains to attaching the

Flowsheet as a Sub-Flowsheet operation. Typically, a template is

representative of a plant process module or portion of a process

module. The stored template can subsequently be read from disk and

efficiently installed as a complete Sub-Flowsheet operation any

number of times into any number of different simulations.

Some of the advantages of using templates are:

Provide the mechanism by which two or more cases can belinked together

Can employ a different property package than the main case towhich it is attached

Provide a convenient method for breaking large simulationsinto smaller, easily managed components

Can be created once and then installed in multiple cases

Before you convert a case to a template, it needs to be made generic so

it can be used with gas plants of various flowrates.

1. Delete the Flow andComposition of streamFeed.

2. Choose Main Propertiesfrom the Simulationmenu.

3. Press the Convert to Templatebutton.

4. Press Yesto convert the simulation case to a template.

5. Answer Noto the question Do you want to save the simulationcase.

6. Save the template as 3-Effect-Evap.tpl.

Note that once a case has beensaved as a template, it can notbe re-converted back into a

normal simulation case.


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Reactions 1

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Reactions



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2 Reactions

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WorkshopThis module demonstrates the HYSYS philosophy for building

reactions within a simulation. HYSYS defines reactions within the

context of the Fluid Package. This is important for a number of reasons:

By associating reactions with the fluid system rather than aspecific reactor unit operation, the user is free to modelreactions anywhere they might take place: in flash tanks, traysections, reboilers etc., as well as in reactors. Reactions aredefined and simply attachedto the equipment piece.

By defining the reactions up front in the fluid system, the

reactions need only be defined once, rather than each time areactor unit is built. Additionally, any changes to the basicreaction data are updated throughout the model automatically.

By separating the reaction definitions from the unit operationsor model topology, component and reaction data may be savedout as an independent file for use in another case. The usercan then create a reaction library or database for future use,thereby eliminating a repetitive task, reducing engineering timeand working more efficiently.

This module presents Steam-Methane Reforming.

Learning ObjectivesOnce you have completed this section, you will be able to:

Define reactions in HYSYS

Model Conversion and Equilibrium reactors in HYSYS.

PrerequisitesBefore beginning this section you need to know how to:

Create a Fluid Package

Add streams

Add Unit Operations


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Reactions and ReactorsThere are five different types of reactors that can be simulated with

HYSYS. By using combinations of these five reactors, virtually any

reactor can be modelled within HYSYS. The five reactor types are:

Conversion- given the stoichiometry of all the reactionsoccurring and the conversion of the base component,calculates the composition of the outlet stream.

Equilibrium - determines the composition of the outlet streamgiven the stoichiometry of all reactions occurring and the valueof equilibrium constant (or the temperature dependantparameters that govern the equilibrium constant) for eachreaction.

Gibbs- evaluates the equilibrium composition of the outletstream by minimizing the total Gibbs free energy of the reactionsystem.

CSTR- computes the conversion of each component enteringthe reactor. The conversion in the reactor depends on the rateexpression of the reactions associated with the reaction type.

PFR- assumes that the reaction streams pass through thereactor in plug flow in computing the outlet stream composition,given the stoichiometry of all the reactions occurring and akinetic rate constant for each reaction.

Note: The required input is different depending on the type of reactor

that is chosen. CSTR and PFR reactors must have kinetic rate constants

(or the formula to determine the kinetic rate constant) as inputs, as well

as the stoichiometry of the reactions. All of the reactor types, except forthe Gibbs type, must have the reaction stoichiometry as inputs.

Reactions can also occur in the Tank, Separator, and Three Phase

Separator Unit Operations if a reaction set is attached.

Note that Kinetic, Kinetic

RevEqb, and Langmuir-Hinshelwood reactions canonly be modelled in the CSTR,PFR and Separator.


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Process Overview


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Steam-Methane ReformerSteam reformation of methane is often undertaken in conjunction with

processes which require large amounts of hydrogen for instance

hydrotreating, ammonia production, or any process which may utilise

such a synthesis gas. Successive reaction stages take advantage of

thermodynamics and catalysts to enhance the production of hydrogen

at the expense of the by-product gases carbon monoxide and dioxide.

Finally, remaining carbon oxides are converted back into methane as

completely as possible to minimise CO and CO2carryover into the

downstream process.

In the course of this problem, we will use two of the reactor types in

HYSYS to simulate the reactors in the steam reformation train: the

Conversionand Equilibriumreactors.


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Building the Simulation

Defining the Simulation Basis

For this simulation we will use the Peng Robinson EOS with the

following components: methane, carbonmonoxide, carbondioxide,

hydrogenandwater. The Fluid Package that you defined can be

renamed to Steam-C1 reformer.

Adding the Reactions

The reactions which take place in this simulation are:

Reactions in HYSYS are added in a manner very similar to the methodused to add components to the simulation:

1. Open the Fluid Package and select the Rxnstab. Press theSimulation Basis Mgrbutton to open the Simulation BasisManager view.

2. Press theAdd Compsbutton to open the component selectionview. Here, we will select the components that we will have use inour reactions.

ReactionName

Reaction

Reform1 CH4 +H2O ---> CO + 3H2

Reform2 CO + H2O ---> CO2+ H2

Shift1 CO + H2O CO2 + H2

Meth1 CO + 3H2---> H2O + CH4


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3. Ensure that the FPkg Poolradio button is selected. Press theAddThis Group of Componentsbutton. This moves the entirecomponent list over to the Selected Reaction Components group.

4. Return to the Simulation Basis Managerview and press theAddRxnbutton. Choose Equilibriumas the type from the displayedlist.

5. Press theAdd Reactionbutton and enter the necessaryinformation as shown:

This has defined the stoichiometry of the first reaction:

CH4 +H2O ---> CO + 3H2

Note that reactants are defined with negative coefficients and products

have positive coefficients; this is the HYSYS standard. All reactions

must be defined this way.

6. Move to the Basistab and click the K vs T Tableradio button.


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7. On the Keq790tab, enter the following values:

8. Add the second Equilibriumreaction by selecting the reactiontype as Equilibrium.

CO + H2O ---> CO2+ H2

9. For reaction 2, proceed as above and enter the following valuesfor the Equilibrium Constant:

The name of this reaction can be changed to Reform 2.

In the absence of a catalyst and at 430 C(800F), the rate of reaction

number 1 in the Shift Reactor is negligible, and reaction number 2

becomes the only reaction.

HYSYS contains a library of some of the most commonly encountered

chemical reactions with their Equilibrium Constants. For the Shift

Reactor, you will use the library values for the Equilibrium Constant.

Temperature, C (F) Keq

595C (1100F) 0.5

650C (1200F) 3

705C (1300F) 14

760C (1400F) 63

815C (1500F) 243

870C (1600F) 817

Temperature, C (F) Keq

675C (1250F) 1.7

advanced simulation case using hysys

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