ChE 477 Workshop 1.Hysys Tutorial B. Joseph
This session is meant to introduce you to the use of Hysys for Steady state simulation. The objective is to get familiar with the menu bars and general principles of operation. We will study the flash separation of a mixture of acetone and water into a vapor and a liquid stream. We will study the effect of physical property models used on the results achieved.
Using Windows Explorer create a new folder in your directory called che477. You will use this directory to store your Hysys runs. Start Hysys.
Open a new case using the menu File/New/Case. Hysys will set up a new design case. Give it a name using the menu File/save. You will be prompted for a name and location.
When you start the simulation Hysys opens up a window called the Simulation Basis Manager. This is where you define the Physical property models to be used in the simulation and the components associated with this physical property model.
( called fluid package)
From the Tools pull down menu select Preferences. Then choose Field units by clicking on it once. It should be highlighted. This specifies your preferences for units used in the data entry and reports. Note that there are other tabs available. Currently you should in the variables tab. The bar at the left shows the other choices available under this tab. (Units and Formats). You might want to inspect the other choices available. When you are done inpecting close the window by clicking on the top right corner.
Next click the add button on the Simulation Basis Manager Menu as shown below.
This will take you to the menu of choices for property models.
From this menu choose Antoine as the Base property package by clicking on it. Next click on the Components Tab. This will take you to the menu of components available for the Antoine package.
On the Match cell, enter the name water. As you type Hysys will bring up components that match your letters. After you have located water, highlight it and then click Add Pure to make this one of the components used in your simulation.
Close the window and then click on Enter Simulation Environment Button. This will put you in the PFD ( Process Flow Diagaram) mode. You can create a flowsheet on this screen. You will also see a menubar of available unit operations on the right. ( Called the Object Pallette). See above diagram.
Click on the Separator icon from this tool bar (first one on top) and then bring your curson to the PFD area and click once to place this unit on the flowdiagram.
Now double click on this new block ( V-100) to open this object. This object has the following tabs: Design/Reactions/Rating/Worksheet/Dynamics. Under Design, we have the menu choices: Connections ( currently active as shown above)/Parameters/User Variables/Notes.
Type feed1 in the Inlets list.
Type vap1 in the vapor Outlet box
Type liq1 in the liquid outlet box.
Type q101 in the energy stream box.
Next click the Parameters on the left menu bar shown above.
Enter the pressure drop as 10 and the Heat Duty as 0. This creates an Adiabatic Flash.
Next click on the Worksheet tab and enter the feed stream conditons as shown below.
Double click on the molar flow of feed1 ( 100.000) to enter its composition. Specify the feed composition as 50 mole% water and 50% acetone.
That is it! The bottom bar should turn green indicating that Hysys has enough data to calcuate the flash unit.
Note that the vapor stream is 17.4 lbmoles per hour.
What is its composition? You can click on the composition menu item on the left to bring up stream compositions.
Note the temperature has dropped to 182 F in the flash.
Isothermal flash: Another type of flash that is often carried out is an isothermal flash. This fixes the flash temperature and computes the heat duty instead. To do this go to the Design Tab and then select parameters again. Remove the entry for the heat duty by clicking on it and then entering blanks instead of zeros.
The bottom bar changes back to yellow indicating that Hysys now does not have enough information.
Now if you go to the Worksheet Tab you will see entries in blue any one of which can be speciied. Let us specify the temperature of vapor stream as 170.
What is the heat duty?
Now remove the temperature specification and change the vapor flow to 40.What is the temperature and heat duty?
How much feed should be fed to the flash drum to produce 30 lbmoles/hr of vapor adiabatically?
These exercises show the power and flexibility of Hysys. You can change items in blue, but only within the degrees of freedom available. When all degrees of freedom as used up, Hysys computes the remaining variables using mass and energy balances combined with the equilibrium relations.
Save your work.
Concept of Degrees of Freedom.
Hysys waits until it has enough data to do the calculations, ie. there are no degrees of freedom left. If you remove any specification, say the feed temperature, then it will not be able to do the flash calculation.
Importance of Using the Correct Fluid Package.
We used Ideal gas model with Antoine vapor pressure equation. While this is efficient, it can lead to totally erroneous conclusions. Let us compare the compositions of the vapor stream using the Antoine equation with a fluid package that uses UNIQUAC model.
The results from Antoine equation are shown below. For
Feed = 100 lbmoles/hr, 200 F, 30psia, Adiabatic Flash.
Close the windows and return to PFD mode. Choose Simulation/ Basis Environment.
Now we can define a new fluid package. First press copy to make a copy of Basis-1.
You now have Basis-2. Click on Basis-2. Then click View. Select UNIQUAC model. Change Vapor model from Ideal to SRK.( Soave-Redlich-Kwong) by clicking on the cell. You can choose SRK from the pull down menu obtained by the down arrow on the left as shown.
Now close the window and change the association between Flowsheet-Fluid pkg to Basis-2 for the Case ( Main) as shown below.
This defines the property package used for the Main flowsheet. We do not have any subflowsheets in this simulation. But we can create subflowsheets and associate different fluid packages with each subflowsheet using this procedure.
Now Return to Simulation Environment. You will be asked if you want to Hold the calculations or to proceed with the calculations. Answer No, so you can see the results.
Compare the liquid compositions. Note that when nonideality is taken into account, our model predicts almost 6% acetone in the liquid as opposed to almost zero %.
Choosing Fluid Package options.
There is no simple way to decide which Fluid package is appropriate for a given application.
For a general discussion on the subject see an excellent article by Carlson.
Report Requirements:
Answer first three questions using Antoine package.
1. What is the heat duty for an isothermal flash at 200 F and 20psia?
2. What is the temperature of an adiabatic flash at 20psia?
3. What temperature is needed to vaporize 50% of feed?
4. How do the above answers change when UNIQUAC fluid package is used with SRK for vapor phase model?
5. What is the answer to question 2 above if UNIQUAC model is used with ideal gas vapor phase model?
Print the complete Workbook for the last problem. This can be done by clicking the Workbook icon on the menubar ( second line from top) and then using File/print option. Submit this with your report.
Babu Joseph Page 4 08/19/99 99wsp1.doc