Hysys(lng) f1h6q

ChE 3G4 HYSYS TUTORIALS Tutorial 1: Introduction to HYSYS – Not Graded ........................................................ 1 A. Learning Objectives:............................................................................................... 2 B. Defining the Simulation Basis ................................................................................ 2 C. Selecting a Unit Set................................................................................................. 3 D. Adding a Stream ..................................................................................................... 3 E. Flash Calculations................................................................................................... 4 F. Adding Utilities....................................................................................................... 5 G. The Stream Property Value..................................................................................... 5 H. Customizing the Workbook .................................................................................... 5 I. Flash Calculations of a Ethanol-Water Mixture ..................................................... 6 J. Additional Exercises (For Extra Practice using the GasPlant Example) ................ 7 Tutorial 2: Propane Refrigeration Loop – 15 Marks .................................................... 8 A. Learning Objectives ................................................................................................ 8 B. Base Case (5 marks)................................................................................................ 8 C. Manipulating the PFD........................................................................................... 10 D. Manipulating Process Variables (10 marks) ......................................................... 10 E. Printing.................................................................................................................. 11 Tutorial 3: Refrigerated Gas Plant - 10 marks ............................................................ 12 A. Learning Objectives .............................................................................................. 12 B. Building the Simulation ........................................................................................ 12 C. Adding the Balance Operation.............................................................................. 14 D. Adding the Adjust Operation ................................................................................ 15 E. Using the Case Study ............................................................................................ 15 F. Bonus (5 Marks) ................................................................................................... 16 G. Saving the Simulation as a Template.................................................................... 16 Tutorial 4: Recycle Operations - 10 marks.................................................................. 17 A. Learning Objectives .............................................................................................. 17 B. Building the Simulation ........................................................................................ 17 C. Installing the Recycles .......................................................................................... 19 Tutorial 5: Separation Columns – 10 marks ................................................................ 21 A. Learning Objectives .............................................................................................. 21 B. Building the Simulation ........................................................................................ 21 C. Column Sub-Flowsheets (Read Only) .................................................................. 26 Tutorial 6: Optimization in HYSYS – 15 marks.......................................................... 27 A. Learning Objectives .............................................................................................. 27 B. Building the Simulation ........................................................................................ 27 C. The Optimizer ....................................................................................................... 29 D. Bonus ( 3 Marks) .................................................................................................. 33

ChE 3G04 Winter 2004 McMaster University

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Tutorial 1: Introduction to HYSYS – Not Graded A. Learning Objectives: • • •

Define a Fluid Package Add streams and a separator Perform simple flash calculations

B. Defining the Simulation Basis 1. To start HYSYS go to Course Folders, Chemical Engineering, ceng3g03 and click on HYSYS.Plant. Start a new case by Selecting File, New, Case. 2. Select the Components tab. This tab allows you to add components to your case. Select these components: N2, H2S, CO2, C1, C2, C3, i-C4, n-C4, i-C5, n-C5, C6 and H2O. You can also add components by typing their names (ie. methane rather then C1) with Match. The components should be listed under Component List-1. Minimize the window. 3. Select the Hypothetical button under Add Component to add a hypothetical component to the fluid package. These components can be used to model nonlibrary components, defined mixtures, undefined mixtures or solids. In this case it will be used to model the components in the gas mixture heavier then hexane. To create this component, select the Quick Create a Hypo Comp button. 4. On the ID tab type the name, C7+. Move to the Critical tab. Enter 110oC for its Normal Boiling Pt. Press Estimate Unknown Props to estimate all the other properties of the hypothetical component. You should get the following base property values: Molecular Wt: 111.00 Ideal Liq Density: 745.38 5. Add the hypothetical component to the current component list by highlighting/selecting it in the Hypo Components group and then pressing Add Hypo button. 6. HYSYS contains various Fluid Packages that contain necessary information for performing flash and physical property calculations. Select the Fluid Pkgs Tab. Create a fluid package by selecting the Add button and choose Peng-Robinson Equation of State Model (PR) 7. Change the Name from Basis-1 to GasPlant. 8. The fluid package is now defined and you can now start a simulation. Press Enter Simulation Environment or the Interactive Simulation Environment in the top toolbar.


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C. Selecting a Unit Set The HYSYS edition in the labs should have the default unit set to SI units. The unit set can be changed. 1. From the Tools menu, choose Preferences. Switch to the Variables tab and click on Units. 2. Highlight the units you wish to work with and close the window. We will use SI units for this tutorial and unless otherwise specified. D. Adding a Stream There are several ways to add a stream. We will focus on one and you may try the others if you have time. Adding a Stream from the Menu Bar 1. Press F11. The stream property view is displayed. Change the stream name to Feed 1. 2. Enter the compositions of the components by selecting the Composition. Select Edit. Click on mole fraction as a basis. Enter the following compositions and press OK. Close the window. Component N2 H2S CO2 C1 C2 C3

Mole Fraction 0.0025 0.0237 0.0048 0.6800 0.1920 0.0710

Component I-C4 N-C4 I-C5 N-C5 C6 C7+ H2O

Mole Fraction 0.0115 0.0085 0.0036 0.0021 0.0003 0 0

The following are other ways to add a stream. Move on to Part D. Work on these after you have completed the rest of the tutorial. Adding a Stream from a Workbook 1. To open or display the workbook, press the Workbook icon on the top toolbar. 2. Enter the stream name, Feed 2 in the **New**.


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3. Double click on the Molar Flow cell and enter the following compositions and click OK. Component N2 H2S CO2 C1 C2 C3

Mole Fraction 0.0002 0.0405 0.0151 0.7250 0.0815 0.0455


Mole Fraction 0.0150 0.0180 0.0120 0.0130 0.0090 0.0252 0

Adding a Stream from the Object Legend (F4 if it is not available) 1. Double click on the materials stream Enter the following compositions. Component N2 H2S CO2 C1 C2 C3

Mole Fraction 0.0050 0.0141 0.0205 0.5664 0.2545 0.0145

(blue) and change the name to Feed 3.


Mole Fraction 0.0041 0.0075 0.0038 0.0037 0.0060 0.0999 0

E. Flash Calculations In this section, simple vapour-liquid equilibrium flash calculations from ChE 3D3 will be performed. HYSYS can perform three types of flash calculations on streams: PressureTemperature, Vapour fraction-Pressure and Vapour fraction-Temperature. Once the composition of the stream and two of either T, P or vapour fraction are known, HYSYS performs a flash calculation on the stream. Try these on Stream Feed 1 1. P-T flash. Set P = 7500 kPa and T = 10oC. The calculated vapour fraction should be 0.9879. 2. Perform a dew pt calculation by setting P =7500 kPa and vapour fraction to 1.0. The dew pt should be 11.43oC. 3. Perform a bubble pt calculation by setting P = 7500 kPa and vapour fraction to 0.0. The bubble pt should be –34.32oC. ChE 3G04 Winter 2004 McMaster University

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F. Adding Utilities The utilities available in HYSYS is a useful tool that interact with your process and provide additional information or analysis of streams or operations. 1. Double click on stream Feed 1. 2. Select the Attachments tab and then select Utilities. Press Create to access the utilities window. 3. Select envelope and press Add Utility. The Envelope utility should be displayed 4. The critical temperature, -12.06oC, and pressure, 8980 kPa, for the stream should be displayed. 5. Select the Performance tab and the Plots tab to view the envelope. By pressing Table, you can view the envelope data in tabular form. 6. You can also add a utility using the Menu Bar – Menu, Utilities. G. The Stream Property Value It is possible to view the properties of the individual phases for any stream. 1. Double click on the stream, Feed 1 and enter the temperature –20oC and a pressure of 6000 kPa. Move the cursor to the left of the view until the cursor changes the resizing arrows. 2. Drag the edge of the view until all the phases can be seen (Feed 1, Vapour Phase, Liquid Phase). H. Customizing the Workbook HYSYS will allow you to customize the workbook. You can add additional pages, change the variables that are displayed on current pages, or change the format of the values which are displayed. In this exercise, a new workbook tab containing stream properties, /Cv, Heat of Vapourization and Molar Enthalpy will be added. 1. Open the workbook by pressing the Workbook icon button on the top toolbar. 2. Select Workbook and Setup from the main menu and the setup window will appear. Under Workbook Tabs, press Add and in the view which appears select Stream+ and OK. 3. A new workbook tab, Streams2 will be listed in the workbook pages group. Highlight this tab. Change the name to Other Properties. 4. In the Variables group, press the Delete button until all the default variables are removed. Click the Add button to add a new variable to the tab. 5. From the Variables list, select /Cv and click OK. Repeat by adding Heat of Vaporization and Molar Enthalpy. Press the Close button to return to the workbook.


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6. The workbook now contains the tab Other Properties which shows the value of /Cv, Heat of Vaporization and Molar Enthalpy. If there are no values for these numbers go back to the Stream tab and enter a temperature and pressure for stream Feed 1. 7. To print a workbook specsheet just right click and select Print Specsheet. 8. Save this file if you wish to try the other methods of adding streams. I. Flash Calculations of a Ethanol-Water Mixture In this exercise, we will take the flash calculations from Part D a step further by adding a separator. To install a flash separator, the following steps need to be performed: 1. Start a new case. Choose a fluid package. Choose UNIQUAC. 2. Select the components ethanol and water. You will learn later on in the course that the type of fluid package must be appropriate depending on your flash components. This means that it might happen that one or some of the desired components do not appear in the list for a certain fluid package. For ethanolwater mixture the UNIQUAC fluid package is appropriate. 3. Create a feed stream and name it. For flash calculations we need to fix the required degrees of freedom (4). A liquid-vapour mixture is necessary to allow separation. We therefore need to find the dew and bubble points, between which the 2 phases exist. Select P = 100 kPa, F = 100 kgmol/h and 50-50 mole fraction for each component. Then to calculate the dew point, set the vapour fraction to 1.0. A green OK should appear which indicates the degrees of freedom have been specified and a converged solution has been found. You should get Tdew = 84.03oC. Now change the vapour fraction to 0.0 to get a bubble point, which is Tbubb = 79.41 oC. Remove the specification of the vapour fraction and select a temperature between the dew and bubble point. The vapour fraction should be between 0.0 and 1.0. The following table shows dew and bubble points for the feed stream at different pressures. these with your case. Pressure (kPa) 100 150 200 250

Tbubb (oC) 79.41 90.09 98.13 104.7

Tdew (oC) 84.03 94.79 102.9 109.5

4. Press F12. We want a separator. Choose vessel and then separator. On the window that pops up enter the name of your feed stream into the Inlet, and name your vapour and liquid outlet and energy streams (ie. Vap, Liq, Q) 5. A yellow warning should appear indicating unknown duty. We will ignore duty in this case. Select Parameters and enter 0 for the duty. A green OK should now appear. ChE 3G04 Winter 2004 McMaster University

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6. Try these examples for pressure and temperature and these results with your case. To view the properties of the inlet and outlet streams double click on the separator and choose the Worksheet tab. To view the composition of the liquid and vapour streams select Composition. P = 150 kPa, T = 92oC, F = 100 kgmol/h Feed vap frac: Liquid Flow: Ethanol mol fraction (liquid) Water mol fraction (liquid) Vapour Flow Ethanol mol fraction (vapour) Water mol fraction (vapour)

0.7147 28.53 kgmol/h 0.3013 0.6987 71.47 kgmol/h 0.5793 0.4206

P = 250 kPa, T = 105oC, F = 100 kgmol/h Feed vap frac: Liquid Flow: Ethanol mol fraction (liquid) Water mol fraction (liquid) Vapour Flow Ethanol mol fraction (vapour) Water mol fraction (vapour)

0.2137 78.63 kgmol/h 0.4628 0.5372 21.37 kgmol/h 0.6368 0.3632

J. Additional Exercises (For Extra Practice using the GasPlant Example) Try these exercises, the answers are in bold. You will need to add the other streams in order to answer some of these questions. 1. The critical pt of Feed 2 -1.11oC, 14431 kPa 2. Cricondenbar (max pressure) for Feed 2 16292 kPa 3. Bubble Pt Temperature for Feed 3 at 6000 kPa -53.57 oC 4. Dew Pt Temperature for Feed 2 at 4000 kPa 98.12 oC 5. Vapour fraction for Feed 1 at 5oC and 8000 kPa 0.9487 o 6. Vapour fraction for Feed 2 at 32 F and 10 bar 0.9245 Note: when entering the pressure and temperature click on the unit drop down box for the correct units. HYSYS will convert these to the default units


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Tutorial 2: Propane Refrigeration Loop – 15 Marks Refrigeration systems are commonly found in the natural gas processing and petroleum refining industry. Refrigeration is used to cool gas to meet a hydrocarbon dewpoint specification and to produce a marketable liquid. In this tutorial you will construct, run, analyze and manipulate a propane refrigeration loop. A. Learning Objectives • • •

Adding and connecting unit operations to build a flowsheet Adding tables to the PFD Printing procedures

B. Base Case (5 marks) Answer the questions that appear as bold and boxed. 1. Start a new case and add the components and fluid package: propane and ethane and Peng Robinson (Equation of State). Enter the simulation environment. 2. Install a stream. Double click on the stream and enter the following information. Name Vapour Fraction Temperature Basis C3 Mole Fraction C2 Mole Fraction

1 0.0 45oC Mole Fraction 1.0 0.0

3. Add a second stream and enter the following properties: Name Vapour Fraction Temperature

3 1.0 -15 oC

What is the pressure of stream 1 in kPa? 4. There are a variety of ways to add unit operations in HYSYS. Last tutorial we used F12 and the Unit Operations window to install a separator. In this case you will add the following operations: valve, chiller, compressor, condenser. The following are alternate ways to install a unit operation. Use the one you feel most comfortable with. These instructions will use F12.


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Workbook

Object Legend

Select Tools, Workbook and select View. Open the workbook and go to UnitOps tab page then click on Add UnitOp button. The UnitOp window will be displayed You can select the unit from the icon of the operation. If this legend is close press F4 and it will appear. You can either double click on the appropriate operation or right click on it and drag it over to the simulation environment (PFD).

5. Press F12 and click on Piping Equipment. Select Valve and press the add button. The valve property window should be displayed. For the Feed stream select 1 and for the Product stream type 2. A J-T valve is being modeled so type J-T as the Name of the valve. Close the window. 6. The chiller operation in the loop is modeled in HYSYS using a heater operation. The outlet of the chiller will be at its dewpoint. Press F12 and select Heat Transfer Equipment. Select Heater and Add. In the property window name the operation Chiller. The inlet is stream 2 and the outlet is stream 3. Name the energy stream Chill-Q. 7. Select Parameters. Enter the values 1.50e+6 kJ/h and 5.0 kPa for the Duty and Pressure Drop of the chiller. A green OK should appear. Close the window. What is the flow rate of propane in kgmol/h? What is the valve pressure drop in kPa? What is the temperature of the valve outlet in oC? 8. The compressor is used to increase the pressure of the inlet gas stream. Press F12 and select Rotating Equipment. Select Compressor and add it. On the property view window enter the Name of the unit as Compressor the Inlet stream is 3, Outlet stream is 4, and Energy stream as Compressor-Q. 9. Select Parameters. Enter the Adiabatic efficiency as 75%. 10. To complete the loop we will add a condenser. It is placed between the compressor and valve and is modeled as a cooler operation. Press F12 and Heat Transfer Equipment. Select Cooler and Add. 11. In the property view window enter the Inlet stream as 4, the Outlet stream as 1, the Name of the unit as Condenser and the Energy stream as Condenser-Q. 12. Select Parameters and enter the Pressure Drop: 30 kPa. 13. If your PFD diagram appears to be small you can zoom in on the PFD by selecting the magnify glass icon and drawing a box around your PFD. What is the compressor duty in hp? Note: 1 J/s = 1.341 x 10-3 hp


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C. Manipulating the PFD HYSYS allows s to view properties and tables and print information for the PFD, unit operations and streams. Try these exercises to get accustomed to these options. 1. For the PFD, right click the mouse and select Add a Workbook Table. Streams should be highlighted and click on Select. Material and energy data for all streams should be displayed in the table on the PFD. You can remove the table by selecting the table, right click the mouse and select Hide. 2. Add a table for stream 4. Select stream 4 and right click on the mouse. Select Show Table from the menu. You can remove the table in the same manner as above. 3. Add a table for the valve. Select the valve using the mouse. Right click on the mouse and select Show table from the menu. Each workbook has a unit operations page by default that displays all the unit operation and their connections in the simulation. You can add additional pages for specific unit operations to the workbook. 1. Open the workbook. In the Menu bar, select Workbook and then Setup. 2. Highlight Unit Ops and press the Add button in the workbook pages group. From the New Object Type view, double click on Unit Operations and then select Compressor. Click Ok. A new page, Compressors, containing only compressor information is added to the workbook. D.

Manipulating Process Variables (10 marks) Save your base case using File, Save, Case. After manipulating variables of the base case for Question 1, you may want to re-open the base case and use it for Question 2. 1. In reality, a plant would not have a pure propane refrigeration cycle. There will always be a small fraction of impurities. Suppose the plant has a 96/4 (mole %) propane/ethane blend. What effect, if any, does this new composition have on the refrigeration loop? Use the base case for comparison. Base Case: 100% C3

New Case: 4 % C2, 96% C3

Flow (kgmol/h) Valve Pressure Drop (kPa) Valve Outlet Temp (oC) Condenser Q (kJ/h) Compressor Q (hp)


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2. In the plant there is no instrumentation that can measure or calculate the chiller duty. However, you know that the compressor is rated for 250 hp and that it is running at 90% of maximum and 70% adiabatic efficiency. Assume a pure propane refrigeration cycle. What is the chiller duty in kJ/h? What is the propane flow rate in kgmol/h. Explain how you solved this problem. E. Printing You can print results through the menu bar, from the PFD and using the report manager. You do not have to print any tables or PFD for this tutorial. Read these procedures only to become familiar with the printing procedures. 1. To print from the menu bar select File, Print. All worksheets will be printed. 2. To print your PFD, right click on the PFD and select Print PFD. 3. You can also print worksheets for specific streams or unit operations. Select the unit operation or stream you wish to have information printed. Right click the mouse and select Print Datasheet. You can view a Preview of the printout as well. 4. To print using the report manager, select Tools, Reports. Press Create to add a new report and open the Report Builder. Press Insert Datasheet to add specsheets to your report. You can add single or multiple unit operations specsheets to the report.


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Tutorial 3: Refrigerated Gas Plant - 10 marks In this simulation, a simplified version of a refrigerated gas plant is to be modified. The purpose is to find the LTS (low temperature separator) temperature at which the hydrocarbon dewpoint target is met. The Sales Gas hydrocarbon dewpoint should not exceed –15oC at 7000 kPa. The incoming gas is cooled in two stages – first by exchange with product Gas Sales in a gas-gas exchanger and then in a chiller. A Balance operation will be used to evaluate the hydrocarbon dewpoint of the product at 6000 kPa. A. Learning Objectives • • • •

Install and converge heat exchangers Understand Logical Operations (Balances and Adjusts) Use the Case Study tool to perform case studies on your simulation Saving the simulation as a template

B. Building the Simulation Answer any questions that appear in bold and boxed. 1. Start a new case. Enter the following components: N2, H2S, CO2, C1, C2, C3, iC4, n-C4, i-C5, n-C5, C6, H2O and a hypothetical component C7+. For the hypothetical component, choose 110oC for its normal boiling point and select Estimate Unknown Parameters to determine all other parameters. Use PengRobinson EOS as a fluid package. Enter the simulation environment. 2. Add a stream. Fill in the following values: Name: Temperature: Component N2 H2S CO2 C1 C2 C3 i-C4

To Refrig 15oC

Pressure: Flow Rate:

Mole Fraction 0.0066 0.0003 0.0003 0.7575 0.1709 0.0413 0.0068

6500 kPa 1500 kgmole/hr Component n-C4 i-C5 n-C5 C6 H2O C7+

Mole Fraction 0.0101 0.0028 0.0027 0.0006 0.0 0.0001

3. Add a separator. Select F12, Vessels and Separator. Enter the following information: Name: Feed:

Inlet Gas Sep To Refrig


Vapour Outlet: Inlet Sep Vap Liquid Outlet: Inlet Sep Liq

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The heat exchanger performs two-sided energy and material balance calculations. The heat exchanger is capable of solving for temperatures, pressures, heat flows, material stream flows and UA. 4. Add a heat exchanger. Select F12, Heat Transfer Equipment and Heat Exchanger. Enter the following information. Name: Gas-Gas Tube Side Inlet: Inlet Sep Vap Tube Side Outlet: Gas to Chiller

Shell Side Inlet: Shell Side Outlet:

LTS Vap Sales Gas

The heat exchanger models are defined as follows: Weighted – The heating curves are broken into intervals, which then exchange energy individually. A log mean temperature difference (LMTD) and UA are calculated to each interval in the heat curve and summed to calculate the overall exchanger UA. The weighted method is available only for counter current exchangers. Endpoint – A single LMTD and UA are calculated from the inlet and outlet conditions. Can be used for simple problems where there is no phase change and is relatively constant. 5. Switch to the Parameters tab. Under Heat Exchanger Model, select Exchanger Design Weighted. Under Individual Heat Curve Details, change the number of intervals to 10 for both streams. Under Exchanger Parameters enter a Tubeside Delta P of 30 kPa and Shellside Delta P of 5 kPa. In order to solve the heat exchanger, unknown parameters are manipulated by the solver. Each parameter specification will reduce the number of degrees of freedom by one. Two specifications are needed for this exchanger: Heat Balance = 0 : this is a duty error specification and is needed to ensure that the heat equation balances. HYSYS will supply this specification by default. Min Approach = 5oC – this is the minimum temperature difference between the hot and cold stream. 6. On the Design tab, select Specs. Deactivate the UA specification. Click on the Active check box for the specification (the X means the specification is active) 7. To add a specification, press the Add button. In the display window enter the following. Close the window once entering the information. Name: :

Temp Approach Overall

Type: Spec Value:

Min Approach 5 oC

What is the flowrate of stream “Gas to Chiller”in kgmol/h? ChE 3G04 Winter 2004 McMaster University

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8. Add a cooler to the simulation. F12, Heat Transfer Equipment, Cooler. Enter the following information: Name: Feed Stream:

Chiller Gas to Chiller

Energy Stream: Product Stream:

Chiller Q Gas to LTS

Under the Parameters tab, add a pressure drop of 40 kPa. 9. Add a separator and provide the following information. Name: Vapour Outlet:

LTS LTS Vap

Feed Stream: Liquid Outlet:

Gas to LTS LTS Liq

10. Specify the temperature of the stream Gas to LTS to be –25oC. • • •

What is the pressure of stream “Sales Gas” in kPa? What is the temperature of stream “Sales Gas” in oC? What is the current available UA for the Gas-Gas exchanger in kJ/oCh?

C. Adding the Balance Operation The balance operation provides a general-purpose heat and material balance facility. There are different balances available in HYSYS: Mole: an overall balance is performed where only the molar flow of each component is conserved. Outlet streams will have the same molar flow rate and composition as the inlet stream, but will contain no vapour fraction, temperature or pressure values. Mass: Same as above but only the mass flow is conserved. Heat: Same as above but only the heat flow is conserved. Mole and Heat: the mole and heat flow are conserved. Look at the parameters for Sales Gas. The stream parameters are calculated so there is no way to force the stream to calculate a dewpoint temperature at 7000 kPa. Adding a mole balance allows you to create a second steam with the same molar flowrate and composition but no vapour fraction, temperature or pressure. 11. Select F12, Logicals and Balance. Add the following information: Inlet stream: Sales Gas

Outlet Stream: HC Dewpoint

Select the Parameters tab. For the Balance Type, click on Mole. 12. Specify a pressure of 7000 kPa for the stream HC Dewpoint. Set the vapour fraction to calculate the dew point temperature. ChE 3G04 Winter 2004 McMaster University

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What is the dewpoint temperature in oC? Assuming the pressure is fixed, what other parameter affects the dewpoint? How can we change the dewpoint in the simulation (Hint: Keep reading on)? D. Adding the Adjust Operation The adjust operation is a logical operation. It will vary the value of one stream variable (independent variable) to meet a required value or specification (dependent variable) in another stream. The current HC dewpoint does not meet the requirement of –15oC. 13. Select F12, Logicals and Adjust. On the display window, press Select Var. in the Adjusted Variable group. From the Object list select Gas to LTS. From the Variable list, select Temperature. Press Ok to accept the variable and return to the Adjust property view. 14. Press the Select Var.. button in the Target Variable group. Select HC Dewpoint Temperature as the target variable. Enter the value of –15oC in the Specified Target Value box. 15. Switch to the Parameters tab. When considering step sizes, use larger rather then smaller sizes. The Secant method works best once the solution has been bracketed by using a larger step size and a converged solution will be found faster. For this case leave parameters at the default values. 16. Go back to the Connections tab and press Start to begin calculations. To view the progress of the Adjust, go to the Monitor tab. What is the chiller outlet temperature to achieve the dewpoint specification in o C? E. Using the Case Study The case study tool allows you to monitor the steady state response of key process variables to changes in your process. You select independent variables to change and dependent variables to monitor. HYSYS varies the independent variables one at a time and the dependent variables are calculated. Instead of using the Adjust to find the LTS feed temperature required to achieve the hydrocarbon dewpoint, you can use the Case Study to examine a range of LTS temperatures and dewpoints. 17. Open the Adjust view. Check the ignore box in the bottom right hand corner. This turns off the Adjust function which is required for the Case Study function to be used. 18. From the Tools menu select Databook. On the Variables tab, press the Insert button. Select the Gas to LTS Temperature as the first variable. Press the Add button to add the variable.


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19. Add a second variable. Select the HC Dewpoint Temperature and press the Add button. Press the close button to return to the Databook. 20. In the Databook, switch to the Case Studies tab. Press the Add button to add a new case study. Select the Gas to LTS Temperature as the independent variable (Ind) and HC Dewpoint Temperature as the dependent variable (Dep.) 21. Press the View button to setup the case study. Enter the values for Low Bound, High Bound and Step Size of –25oC, 5oC and 5oC respectively. Press the Start button to begin the calculations. What Gas to LTS temperature range will satisfy the HC Dewpoint specification (-15oC)? Reactivate the Adjust operation by unchecking the ignore box. SAVE THIS CASE ON A DISK F. Bonus (5 Marks) What is the log mean temperature difference (LMTD) for the exchanger with an minimum approach temperature of 5oC? Double Click on the heat exchanger to find this information. Suppose now the available UA for the Gas-Gas exchanger is only 1.5 x 105 kJ/oC h. Make the necessary modifications to your exchanger design to achieve this UA. What is the affect on your LMTD and minimum approach temperature? Describe the steps you took to solve this problem in HYSYS. G. Saving the Simulation as a Template HYSYS allows the to save a simulation as a template. A 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 be read from disk and installed as a complete sub-flowsheet operation any number of times into any number of different simulations. The main advantage of a template is it can link two or more cases together. 22. Choose Main Properties from the Simulation menu. 23. Press Convert to Template button. Press Yes to convert the simulation case to a template. Answer No to the question “Do you want to save the simulation case.” Name your template file.


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Tutorial 4: Recycle Operations - 10 marks In this tutorial, a typical application of the recycle operation will be used. Feed gas enters the compressor station at 40oC and 1725 kPa. The gas is to be delivered at 7500 kPa and it is to be compressed in two stages. Each stage consists of a knockout drum, a compressor and a cooler. Liquids from each separator are recycled back to the previous stage, after the pressure has been reduced.

A. Learning Objectives • Using the Recycle operation in HYSYS B. Building the Simulation 1. Start a new case and select the Peng Robinson EOS with the following components: N2, CO2, C1, C2, C3, i-C4, n-C4, i-C5, n-C5, C6. 2. Add a material stream with the following information:

Name Pressure Component N2 CO2 C1 C2 C3

To Compression 1725 kPa Mole Fraction 0.0075 0.0147 0.5069 0.1451 0.0725

Temperature Molar Flow Component i-C4 n-C4 i-C5 n-C5 C6

40 oC 7500 kgmol/h Mole Fraction 0.0652 0.0578 0.0515 0.0431 0.0357

3. Install a mixer (F12, Piping Equipment, Mixer) with the following information: Name: Outlet:

Mixer To LP Sep

Inlet:

To Compression

On the Design tab select Parameters and select the pressure assignment as Equalize All. 4. Add a separator with the following information: Name: Feed:

LP Sep To LP Sep

Vapour Outlet: Liquid Outlet:

LP Sep Vap LP Sep Liq

5. Add a compressor (F12, Rotating Equipment, Compressor) with the following information: Name: Inlet:

Stage 1 LP Sep Vap

Outlet: Stage 1 Out Energy: Stage 1 HP

Select the Dynamics tab and enter an adiabatic efficiency of 75%. In the worksheet enter a pressure of 3450 kPa for stream Stage 1 Out.


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6. Install a cooler with the following information: Name: Stage 1 Cooler Inlet: Stage 1 Out

Outlet: Energy:

Cooler 1 Out Stage 1 Q

In the Design tab select Parameters and enter a pressure drop of 0 kPa. In the worksheet enter a temperature of 50oC for stream Cooler 1 Out . 7. Add a mixer operation with the following information: Name: Inlet:

Mixer 2 Cooler 1 Out

Outlet:

To IS Sep

For the pressure assignment choose Equalize all. 8. Install a separator with the following information: Name: Feed:

IS Sep To IS Sep


IS Sep Vap IS Sep Liq

9. Add a Valve (F12, Piping Equipment, Valve) with the following information: Name: Inlet:

LetDown 1 IS Sep Liq

Outlet:

LD1 Out

In the worksheet enter a pressure of 1725 kPa for stream LD1 Out. 10. Install a compressor with the following information: Name: Inlet:

Stage 2 IS Sep Vap

Outlet: Energy:

Stage 2 Out Stage 2 HP

Enter an adiabatic efficiency of 75%. In the worksheet enter a pressure of 7500 kPa for the stream Stage 2 Out. 11. Install a cooler with the following information: Name: Inlet:

Stage 2 Cooler Stage 2 Out

Outlet: Energy:

Cooler 2 Out Stage 2 Q

Enter a pressure drop of 0 kPa. In the worksheet enter a Cooler 2 Out temperature of 50oC. 12. Add a separator with the following information: Name: Feed:

HP Sep Cooler 2 Out



HP Gas HP Sep Liq

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13. Install a valve with the following information: Name: Inlet:

LetDown 2 HP Sep Liq

Outlet: LD2 Out

In the worksheet enter a pressure of 3450 kPa for stream LD2 Out.

1. What is the duty of the two coolers in kJ/h?

C. Installing the Recycles A recycle operation is a mathematical unit operation. It has an inlet (calculated) stream and an outlet (assumed) stream. The recycle installs a theoretical block in the process stream. The feed into the block is termed the calculated recycle stream and the product is the assumed recycle stream. The following steps take place during the convergence process: • • • •

HYSYS uses the conditions of the assumed stream and solves the flowsheet up to the calculated stream. HYSYS then compares the values of the calculated stream to the assumed stream. Based on the difference between these values, HYSYS modifies the values in the calculated stream and es the modified values to the assumed stream. The calculation process iterates until the values of the calculated stream match those of in the assumed stream within specified tolerances (Sequential Modular).

2. Examine the streams LD1 Out and LD2 Out. Fill in the table of Values: o

LD1 Out

LD2 Out

Temperature ( C) Flow (kgmole/h) Vapour Fraction Is Composition known (y/n)? 3. Can these be used as a guess for the recycle outlet?Why?


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14. Add the first recycle. Select F12, Logicals and Recycle. Enter the following information: Name: Feed:

RCY-1 LD1 Out

Product:

RCY-1 Out

15. Click on the Parameters tab. HYSYS allows you to set the convergence criteria or tolerance for each of the recycle variables. Smaller tolerances result in a tighter convergence requirement. Leave everything at their default. 16. In the Parameters tab select Numerical. This page contains the options for the two types of recycles, Nested and Simultaneous. In this case, use Nested Recycles. This page also displays the convergence information as the calculations are performed (maximum iterations, acceleration method, number of iterations). Use the Wegstein acceleration method for this case. Nested: this type of recycle gets called whenever it is encountered during calculations. Use this type if you have a single recycle or if you have multiple recycles which are not connected. Simultaneous: all recycles set at simultaneous will be called at the same time. Use this option if your flowsheet has multiple inter-connected recycles.

The recycle worksheet page displays the inlet and outlet stream information. In this case the inlet and outlet streams should have the same values. This is because before we installed the recycle, the inlet stream was already calculated by HYSYS. 17. Install the second recycle with the following information: Name: Feed:

RCY-2 LD2 Out

Product:

RCY-2 Out

18. The final step to solve the flowsheet is to connect the recycle outlets as inlets to Mixer 1 and Mixer 2. Double click on Mixer 1 and add RCY-1 Out as a feed. Repeat with Mixer 2 with RCY-2 Out as a feed. Look at the Worksheet tab for each recycle. The flowrates should be identical for the inlets and outlets. There may be small differences (see bonus question).

4. Fill in the following table. RCY 1

RCY 2

Inlet Vapour fraction Outlet Vapour fraction BONUS (2 marks): The vapour fractions will be slightly different in the recycle inlet and outlet for one or both streams, but should be identical. What can be done to achieve identical vapour fractions?


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Tutorial 5: Separation Columns – 10 marks Recovery of natural gas liquids (NGL) from natural gas is a common procedure in the gas processing industry. Recovery is done to produce transportable gas free from heavier hydrocarbons, meet sales gas specification and to maximize liquid recovery (when liquid products are more valuable than gas). HYSYS can model diffrent column configurations. In this NGL plant the following three columns will be modeled: De-Methanizer, DeEthanizer and De-Propanizer. A. Learning Objectives • Add columns (Absorber and distillation) • Add extra specifications to columns B. Building the Simulation 1. 2.

Start a new case using Peng Robinson EOS as a fluid package and adding components: N2, CO2, C1, C2…..C8 and enter the simulation. Add a material stream with the following data: Name Pressure Component N2 CO2 C1 C2 C3 i-C4

3.

Feed 1 2275 kPa Mole Fraction 0.0025 0.0048 0.7041 0.1921 0.0706 0.0112

Temperature Flowrate Component n-C4 i-C5 n-C5 C6 C7 C8

-95oC 1590 kgmol/h Mole Fraction 0.0085 0.0036 0.0020 0.0003 0.0002 0.0001

Add a second material stream with the following data: Name Pressure Component N2 CO2 C1 C2 C3 i-C4

Feed 2 2290 kPa Mole Fraction 0.0057 0.0029 0.7227 0.1176 0.0750 0.0204


Temperature Flowrate Component n-C4 i-C5 n-C5 C6 C7 C8

-85oC 215 kgmol/h Mole Fraction 0.0197 0.0147 0.0102 0.0037 0.0047 0.0027

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4.

Add a energy stream (select the red arrow from the legend template) and enter the following information: Name: Ex Duty

Energy Flow: 2.1 x 106 kJ/h

The De-Methanizer is modeled a reboiled absorber operation with two feed streams and an energy feed stream which represents a side heater on the column. 5.

Add the reboiled absorber (F12, Prebuilt Columns, Reboiled Absorber). Enter the following column information: Column Name Optional Feed Stream / Feed Stage Ovhd Vapour Product Bottoms Liquid Product

DC1 Feed 2 / 2 DC1 Ovhd DC1 Btm

Top Stage Feed Optional Feed Stream / Feed Stage Reboiler Energy Stream C. Tray Numbering

Feed 1 Ex Duty / 4 DC1 Reb Q Top Down

For the optional feed streams make sure the two streams are being fed to the correct column stage. Select Next. 6.

7.

Enter a Top Stage Pressure estimate of 2275 kPa and Reboiler Pressure of 2310 kPa and select Next. Enter a temperature estimate for the Top Stage as -88oC and Reboiler temperature estimate of 27 oC. Select Next. No information is supplied for the Boilup Ratio so select Done. HYSYS will open up the column property view. Select the Design tab and Monitor. Activate the Ovhd Prod Rate and specify a value of 1338 kgmol/h. Deactivate the Btms Prod Rate and Boilup Ratio if they are active. This should give zero degrees of freedom. Select Run to converge the column. If there is no convergence, ask the TA.

1. What is the mole fraction of methane in DC1 Ovhd.?

It is not always practical to have flow rate specifications. These specifications can result in columns which cannot be converged or produce streams with undesirable properties. An alternative approach is to specify either component fractions or component recoveries in the column product streams.


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8. 9.

In the Design tab select Specs. Press the Add button and select Component Fractions from the list that appears. Press the Add Specs button. In the display window that appears enter the following information and close the window: Name: Stage: Flow Basis:

Comp Fraction 1 Mole Fraction

Phase: Vapour Spec Value: 0.96 Components: Methane

10. Select Monitor from the Design tab. The column shows zero degrees of freedom even though you just added another specification. This is due to the fact that the specification was added as an estimate, not as an active specification. Deactivate the Ovhd Prod Rate and activate the Component Fraction of methane. Once the column has converged you can view the results in the Performance or Worksheet tab. 2. What is the flowrate of the overhead product, DC1 Ovhd in kgmol/h

11. Install a pump (F12, Rotating Equipment, Pump). The pump is used to move the De-Methanizer bottom product to the De-Ethanizer. Enter the following information: Inlet: Outlet:

DC1 Btm DC2 Feed

Energy: P-100-hp

In the worksheet, enter a pressure of 2792 kPa for stream DC2 Feed. The De-Ethanizer column is modeled as a distillation column with 14 stages. It operates at a pressure of 2760 kPa. The purpose of this column is to produce a bottoms product that has a ratio of ethane to propane of 0.01. 12. Install a distallation column (F12, Prebuilt Columns, Distillation) and enter the following information. Name Feed Stage/ Stage Ovhd Vapour Product Bottom Product Condenser Duty

DC2 DC2 Feed / 6 DC2 Ovhd DC2 Btm DC2 Cond Q


No. of Stages Condenser Type Ovhd Liquid Product (Distillate) Reboiler Duty

14 Partial DC2 Dist DC2 Reb Q

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Enter the following pressures, temperature estimates and column specifications and press Run: Condenser P Condenser Delta P Reboiler P Condenser T

2725 kPa 35 kPa 2792 kPa -4oC

Reboiler T Ovhd Vapour Rate Distillate Rate Reflux Ratio

95oC 320 kgmol/h 0 kgmol/h 2.5 (molar)

3. What is the flowrate of C2 and C3 in DC2 Btms in kgmol/h? 4. What is the ratio of C2/C3?

13. In the Design tab, select Specs. Press the Add button and select Component Ratio from the list of specifications. Enter the following information on the display window which appears. Name: Stage: Flow Basis:

C2/C3 Reboiler Molar

Phase: Liquid Spec Value: 0.01 Components: ethane, propane

14. Select Monitor and deactivate the Ovhd Vap Rate and activate C2/C3 specification. 5. What is the flowrate of DC2 Ovhd in kgmol/h?

15. Add a valve (F12, Piping Equipment, Valve). A valve is required to reduce the pressure of the stream DC2 Btm before it enters the De-Propanizer. Enter the following information: Inlet: DC2 Btm

Outlet: DC3 Feed

Enter a DC3 Feed pressure of 1690 kPa. The final column to be added is the De-Propanizer. It is modeled as a distillation column with 24 stages. The purpose of this column is to produce an overhead product that contains no more then 1.5 mole percent i-C4 and n-C4 as well as a concentration of propane in the bottoms product that should be less then 2 mole percent.


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16. Add a distillation column with the following information: Name Feed Stream/ Stage Ovhd Liquid Product Reboiler Duty

DC3 DC3 Feed/ 11 DC3 Dist

No. of Stages Condenser Type Bottom Product

24 Total DC3 Btm

DC3 Reb Q

Condenser Duty

DC3 Cond Q

Enter the following pressures, temperature estimates and specifications and run the column: Condenser P Condenser Delta P Reboiler P Condenser T

1585 kPa 35 kPa 1655 kPa 38oC

Reboiler T Distillate Rate Reflux Ratio

120oC 110 kgmol/h 1.0 (molar)

6. What is the mole fraction of C3 in the overhead and bottoms product?

17. Create two new Component Fraction specifications for the column: Specification 1: Name: Stage: Flow Basis:

iC4 and nC4 Condenser Molar

Phase: Liquid Spec Value: 0.015 Components: i-butane, n-butane

Specification 2: Name: Stage: Flow Basis:

C3 Reboiler Molar

Phase: Spec Value: Component:

Liquid 0.02 propane

18. Deactivate the Distillate Rate and Reflux Ratio specification and activate the iC4 and nC4 and C3 specification. 7. What is the flowrate in kgmol/h of the distillate and bottoms products?


25

C. Column Sub-Flowsheets (Read Only) The column is a special type of sub-flowsheet in HYSYS. Sub-flowsheets contain equipment and streams, and exchange information with the parent flowsheet through the connected streams. From the main environment, the column appears as a single, multifeed, multi-product operation. The column sub-flowsheet provides a number of advantages: Optional use of different Fluid Packages- HYSYS allows you to specify a unique fluid package for the column sub-flowsheet. This may be useful in instances when a different fluid package is better suited for the column or column does not use all the components in the main flowsheet and by decreasing the number of components you may speed up convergence. Isolation of Column Solver- The column sub-flowsheet allows you to make changes and focus on the column without recalculation of entire flowsheet. Ability to solve multiple towers simultaneously- The column sub-flowsheet uses a simultaneous solver whereby all operations within the subflowsheet are solved simultaneously. The simultaneous solver permits the to install multiple interconnected columns within the subflowsheet without the need for recycle blocks. The column sub-flowsheet can be accessed by pressing the Column Environment button on the Column Property View. You can return to the main environment by pressing the Parent Environment button.


26

Tutorial 6: Optimization in HYSYS – 15 marks In this example, a stabilization scheme is used to separate an oil and gas mixture into a stabilized oil and saleable gas. This approach is used in many gas plants where liquid production is small and does not warrant a full distillation column. A simple three-stage separation with heating between each stage is used. The object of the exercise is to select the let-down pressure and temperatures such that the products revenue less the utilities cost is maximized. A special tool in HYSYS, the optimizer, will be used to find the optimal operating conditions. A. Learning Objectives • •

Use the optimizer tool in HYSYS to optimize flowsheets Use the spreadsheet to perform calculations

B. Building the Simulation 1. Start a new case using Peng Robinson EOS as a fluid package and add components C1,C2….C9. 2. Modify the unit set. For this case the units for molar flow are in m3/d_gas, instead of kgmol/h and units for liquid volume flow are m3/d rather then m3/h. From the Tools menu select Preferences and go to the Variables tab. Select the SI unit set as the default. Click on the Clone button. Rename the cloned set to Optimizer. Move the cursor to the Flow cell. Select m3/d_gas from the drop down menu. Move the cursor to the Liquid Volume Flow cell and select m3/d. 3. Add a material stream with the following information: Name Pressure Component C1 C2 C3 i-C4 n-C4

Feed 4125 kPa Mole Fraction 0.316 0.158 0.105 0.105 0.105

Temperature Molar Flow Component i-C5 n-C5 C6 C7 C8 C9

10oC 28200 m3/d_gas Mole Fraction 0.053 0.053 0.027 0.026 0.026 0.026

4. Add 3 heaters to the simulation with the following information Heater 1 Name: Outlet:

Heater 1 HotFeed 1

Inlet: Energy:

Feed Steam 1

Enter a pressure drop of 0 kPa and a Duty of 4.25 x 105 kJ/h.


27

Heater 2 Name: Outlet:

Heater 2 HotFeed 2

Inlet: Energy:

Stage1 Liq Steam 2

Enter a pressure drop of 0 kPa and a Duty of 3.15 x 105 kJ/h. Heater 3 Name: Outlet:

Heater 3 HotFeed 3

Inlet: Energy:

Stage 2 Liq Steam 3

Enter a pressure drop of 0 kPa and a Duty of 1.13 x 105 kJ/h. 5. Add 3 separators with the following information: Separator 1 Name: Feed:

Stage 1 HotFeed 1

Liquid Outlet: Vapour Outlet:

Stage 1 Liq Stage 1 Vap

Enter a pressure drop of 0 kPa (should be at this value). Separator 2 Name: Feed:

Stage 2 HotFeed 2


Stage 2 Liq Stage 2 Vap

Delete the pressure drop value (0 kPa is the default). Separator 3 Name: Feed:

Stage 3 HotFeed 3


Liquid Product Stage 3 Vap

Delete the pressure drop value (0 kPa is the default). 6. Add 2 compressors with the following information: Compressor 1 Name: Inlet:

Comp 1 Stage 2 Vap

Outlet: Energy:

Comp 1 Out Comp 1-hp

Enter an adiabatic efficiency of 75%.


28

Compressor 2 Name: Inlet:

Comp 2 Stage 3 Vap

Outlet: Energy:

Comp 2 Out Comp 2-hp

Enter an adiabatic efficiency of 75%. 7. Add a mixer with the following information: Name: Inlets:

Gas Mixer Stage 1 Vap Comp 1 Out Comp 2 Out

Outlet:

Gas Product

Set the pressure assignment to Set Outlet to Lowest Inlet. 8. Make the necessary stream specifications Stage 2 Vap, Pressure Stage 3 Vap, Pressure Comp 1 Out, Pressure Comp 2 Out, Pressure

2050 kPa 350 kPa 4125 kPa 4125 kPa

The vapour pressure is the pressure of a confined vapour in equilibrium with its liquid at a specified temperature. It is a measure of a liquid’s volatility. Vapour pressure of gasoline and other volatile petroleum products is commonly measured as a Reid Vapour Pressure (RVP). RVP is useful in predicting seasonal gasoline performance (high volatility is needed in winter, lower volatility in summer), as well as the tendencies of gasolines and other volatile petroleum products toward evaporative loss and fire hazard. 9. The Reid Vapour Pressure (RVP) of the stream Liquid Product should be approximately 96.5 kPa to satisfy the pipeline criterion. Create a utility by selecting Tools and Utility. The RVP for a stream is located in the Cold Properties utility. 1. What is the current RVP for stream Liquid Product? C. The Optimizer C. The Optimizer HYSYS contains a multi-variable steady state optimizer. Once your flowsheet has been built and a converged solution has been obtained, you can use the optimizer to find the operating conditions which minimize or maximize an objective function. The optimizer contains a spreadsheet for defining the objective function as well as any constraints. The following are some important terminology when dealing with an optimization problem.


29

Primary Variables: these are flowsheet variables whose values are manipulated in order to minimize/maximize the objective function. You set the upper and lower bound for the primary variables, which are used to set the search range. Objective Function: this is the function which is to be minimized or maximized. The function has to be defined within the spreadsheet. Constraint Functions: these are inequality or equality functions that are defined in the spreadsheet. In solving the objective function, the optimizer must meet these constraint specifications. In this case we want to maximize profit while achieving a RVP of Liquid Product less then 96.5 kPa. The revenues from the plant are the Gas Product and Liquid Product. The associated operating costs are the steam costs for each heater plus the compression costs for each compressor. Profit = Revenue – Cost Profit = Gas Product + Liquid Product – Steam Costs – Compression Costs 2. Which variable can we change to affect steam cost?

3. How is the compression cost measured?

4. Which variables can we change to affect the compression cost ( the compressor outlet pressure is fixed)?

5. What should be the process (adjusted) variables be to maximize profit (there are five)?


30

10. To load the optimizer, select F5. Select the Variables tab. You can define the process (adjusted) variables. Press the Add button to add the first variable, Steam 1, Heat Flow. Set the low bound to 0 and the high bound to 1 x 106 kJ/h. Complete the list of process variables below. Object Steam 2 Steam 3 Stage 2 Vap Stage 3 Vap

Variable Heat Flow Heat Flow Pressure Pressure

Low Bound 0 kJ/h 0 kJ/h 650 kPa 70 kPa

High Bound 1.0e+6 kJ/h 1.0e+6 kJ/h 3500 kPa 1000 kPa

The optimizer has its own spreadsheet for defining the objective and constraint functions. Primary variables may be imported and function defined within the optimizer spreadsheet. 11. Select the Spreadsheet button on the optimizer view to open the spreadsheet. On the Parameters tab, increase the number of row form 10 to 15. Make sure your units set is Optimizer not SI. Move to the Spreadsheet tab. 12. HYSYS allows you to import variables from the simulation into the spreadsheet. The following variables need to be imported into the spreadsheet. Select the appropriate cell, right-click on the mouse and choose Import Variable. Select the appropriate variable. In the spreadsheet you may want to write the variable name in the next cell beside the value. Cell

Object B1 B4 B8 B9 B12 B13 B14 D4

Utility-1 Select Utility from the Navigator Scope Liquid Product Select Flowsheet from the Navigator Scope Comp 1-hp Comp 2-hp Steam 1 Steam 2 Steam 3 Gas Product


Variable Reid VP Std Liquid Volume Flow Heat Flow Heat Flow Heat Flow Heat Flow Heat Flow Molar Flow

31

The following constants should be added to the spreadsheet. Do not include their units. Cell B2 B6 B10 B15 D6

Comment RVP Specification Oil Price Compression Cost Steam Cost Gas Price

Value 96.5 kPa 94.35 $/m3 0.1 $/kw-h 0.682 $/kw-h 0.106 $/m3_gas

Conversion factor which you will need: 1 kw-h = 3600 kJ 13. In cells D7, D8 and D9, calculate the Gas Revenue, Oil Revenue and Total Revenue. Watch your units. To write a formula in a cell you do not have to type the = sign first. Here are the functions you need to know for this case with an example of what to type in a cell. Addition (+): +A1+A2 Subtraction (-): +A1-A2 Multiplication (*): +A1*A2 14. Other functions are available by selecting the Functions Help button. The wrong units will be displayed when each value is calculated. To make these values unitless go to Variable Type and scroll down to SG. 15. In cells D12, D13, calculate the Compression and steam costs. In cell D14 calculate your Net Revenue (Profit). 16. The Function tab contains two groups, the objective function and the constraint functions. Close the spreadsheet window and return to the optimizer window. Select the Functions tab. Select the objective function cell (D14) and select maximize. For the constraint function select the Add button. For the LHS cell select cell B1 (current RVP). Select < for the condition. Select cell B2 (RVP Specification) for the RHS cell. Leave the penalty function as is. 17. Select the Parameters tab. This is used to select the optimization scheme. Select SQP (Sequential Quadratic Programming). Use the defaults for tolerance and number of iterations. 18. Move to the Monitor tab and press Start to begin the optimization.


32

6. Fill in the results. optimized case.

Give a brief summary comparing the base case to the

Gas Product Flow m3/d_gas Liquid Product Flow, m3/d Total Profit $ Steam 1 Heat Flow, kJ/h Steam 2 Heat Flow, kJ/h Steam 3 Heat Flow, kJ/h Stage 2 Vap Pressure, kPa Stage 3 Vap Pressure, kPa RVP of Liquid Product kPa

Base Case 25343

B. Optimized Case

17.25 361.6 425000 315000 113000 2050 350 Answer to Question 1

D. Bonus ( 3 Marks) The pressure of the Stage 3 Vap has been decreased to 70 kPa which is less than atmospheric. This is not a desired condition for the inlet of a compressor. The inlet of the second compressor, Comp 2, cannot be less then 125 kPa. What is the maximum profit that can be obtained with this additional constraint. Explain how you solved this problem in HYSYS.


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