Appendix A Process Simulation HYSYS
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HYSYS Operating Instruction A Deethanizer will be used as the sample problem. Here is the PFD and Material Balance that must be designed.
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HYSYS 2.2 --- Operating Instructions Deethanizer Design Set Up the Simulation 1.
Open HYSYS
2.
Change Units to English (also can set other preferences, like color)
TOOLS-PREFERENCES-Variables-Field
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3.
Start a New Case to enter the BASIS Manager (where you define your components, chemistry, VLE Data, etc)
FILE-New-Case
Before proceeding, SAVE your file. Save often and keep multiple copies for various levels of detail. Always have a copy of something that worked. FILE-SAVE AS-locate where you want to put it.
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4. Bring up the Fluid Package (by pressing Fluid Package Tab and then ADD) That brings you directly to the Prop Package Tab. For a Deethanizer simulation, all components will be ideal, so we will pick PRSV equation of state. This choice must eventually be verified with actual data or experience.
5. Pick Components (View Components Button) Find your component by name or formula (a bit tricky sometimes) and move it from the library to your simulation using the <----Add Pure Button.
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The components can be sorted with the SORT LIST button (recommend you do this in order of expected volatility).
You can remove any components you accidentally added with the REMOVE COMPS button. You should at least review the other tabs, especially if you used one of the nonideal VLE packages (e.g. NRTL). You could now add your reactor information, but let’s do that later. Close the Fluid Package and reenter the Simulation Manager and then hit the ENTER SIMULATION ENVIRONMENT button. When you enter the Simulation Environment you can change all of your colors using Tools-Preferences-Resources.
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Define Simulation Blocks You will see a PFD Screen and an Equipment Screen. 1. Add a Feed
Click and Drag the Blue Arrow indicating a material stream to the PFD Screen (red arrow is an energy stream).
Define the Feed by double clicking and opening up you feed window.
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The first screen has the Conditions for the stream. Input 2 of 3, Temperature, Pressure, Vapor Fraction (VF). A VF=0 indicates a bubble point and a VF=1 °F and (let’s assume) indicates a dew point. We know that the stream is at 100 400 psia.
Enter the Feed Compositionby hitting COMPOSITION from the menu.
YOU CANNOT MAKE CHANGES HERE. You need to hit the EDIT button.
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Pick your COMPOSITION BASIS (mole or weight, Flows or Fractions). We’ll use weight Flows from our material balance. Enter your Data. Hit Normalize.
Hit OK and go back to your Conditions menu and you’ll see that the vapor fraction and Lb mol/hr have been calculated along with various other properties. You also see that there is now a green strip saying OK at the bottom. This indicates that the Feed is fully defined. The Light Blue arrow also turns Dark Blue. Close this screen and lets add a heat exchanger.
2. Add a Heat Exchanger
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Click and Drag a Heat Exchanger Icon to the PFD Screen. There are a bunch of them, lets take the Blue Shell and Tube indicating a cooler.
Define the Exchanger by double clicking and opening up the input windows.
First,inlet connect the isflowsheet byyour naming the inlet outlet and energy streams. The stream obviously defined feed and stream (Stream 1). You can App A - 11
name the outlet, lets call it DeC2 Feed, and the energy stream can be anything (call it Refrig-1).
Go to the PARAMETERS Menu. Put in a pressure drop of 5 psi, but DO NOT put in a duty. You can define the load on the exchanger with duty (here) or by defining the outlet stream temperature or Vapor Fraction. We will do it with the stream. If you try to do both, the little red light at the top will light and you will be required to unspecify the problem. Close up the Heat Exchanger (we will specify the load in the HEx outlet stream). Note that HEx is now connected, but it has not been calculated.
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Double click onto the HEx outlet stream (DeC2 Feed).
Let’s say we want to condense the stream to its bubble point (VF=0). (Note that Stream 1 has a vapor fraction of 1.0 at 100°F and 350 psia. Enter Vapor °F) and the OK given. Fraction = 0 and the temperature is calculated (25.3 App A - 13
Close this and the PFD now appears complete. Bringing your cursor to the Heat Exchanger opens up a box which shows that a duty of 10.44 MMBTU/hr has been calculated.
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3. Add a Distillation Tower
Click and drag a distillation tower icon to the PFD screen. There are a bunch of them --- pick the one with a condenser and a reboiler.
Define the tower parameters by double clicking and opening up an input sheet.
We will design the Deethanizer. Input the following info on this first sheet. App A - 15
o o o o o o o o o o When
Stream Names (be descriptive) DeC2 Feed (from the Feed HEx Outlet) Crude C2s (overhead stream) Crude C3s (bottom stream) Refrig-0F (condensing medium - 0°F refrigerant) LPS (reboiling medium – low pressure steam) Column Name (DeC2) Condenser Type (Total) Number of Stages (lets say 30) Feed Stage (lets say in the middle – 15) done, the NEXT button will activate.
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Next screen is for the pressure levels. The DeC2 runs at 300 psia condenser with a 5 psi pressure drop for the condenser and a 0.15 psi∆P per theoretical stage (0.15 x 30 = 4.5 psi∆P for all of the trays). o Reboiler Pressure = 300 + 5 (Condenser) + 4.5 (trays) = 309.5 psia.
Hit the NEXT button to get the Temperature Estimate page. Put in 0°F at the top and 100°F at the bottom. Good estimates can be critical in complex problems.
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Hit NEXT and get the final input screen where Reflux Ratio (RR) and a material balance spec is inputted. I would start with a RR = 1.0 and you can take your distillate rate directly from your material balance (40,198 lb/hr). Make sure you change your flow basis to mass.
Press DONE and enter the tower run/performance sheets. The first screen is the echo of your input. You come here to change, number of trays, feed location…..
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The menu on the left side of the DESIGN form shows where to go to modify your tower specs, put in new specs and change condenser requirements. Hit the MONITOR button and show your run sheet. You’ll find it convenient to execute your run from this sheet so you can observe (monitor!!!) what’s happening.
Your 1.0 RR and 40,198 lb/hr Distillate Rateare already shown. These are your two tower specs. If you try and add another one (say Bottoms rate), theprogram will tell you are over specified. Press the RUN button.
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The red bar at the bottom turns yellow to say it is solving and then green when it is converged. You now have a valid run. But is it the solution that you want. Remember, that we wanted only 20 lb/hr of C2’s in the bottom (900 wt ppm) to meet the Propylene Product spec. To check it, press the PERFORMANCE tab.
You can change units and column widths to get a better view. The 1st menu shows the composition of both the feed and products. This shows you have about 2 lb/hr C2’s in the C3’s while your specs allow 20. In general, it is not a good idea to make “too good” a product, so that we should back off, either by reducing reflux or stages.
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Similarly, you can get the tower Temperature and Pressure and Flow profiles by hitting the Column Profile Button.
The tower heat loads are found by hitting the Feeds/Products Button. (Condenser = 11.4 MMBTU/hr and Reboiler = 11.7 MMBTU/hr duties) Finally,
you
can
plot
any
of
the
profiles
using
the
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plots
button.
Now, back to the problem. Since our C3 Bottoms are TOO GOOD quality, let’s reduce RR from 1.0 to 0.8. Close the table and go back to the MONITOR screen (at the DESIGN tab). Change the RR to 0.8. It will recalculate your tower for the new RR automatically. Go back to PERFORMANCE/SUMMARY.
The C2’s are now at 5.0+ lb/hr. We can reduce RR further. By trial and error you can get to a RR = 0.69 to get 20 lb/hr. OR, you can set up another tower spec to get it for you directly. Go to the DESIGN Tab, and hit the SPECS button on the left to open up the SPECS window.
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Add a new spec that says we want exactly 20 lb/hr C2s in the Crude C3s stream. First, hit the ADD button on the Spec sheet. Then in the popup menu find the Column Component Flow. Double Click on it and fill in the info for the new menu.
Close the screen and go back to monitor where you will see the new spec at the bottom. Now you need to deactivate one spec (RR) and activate the new one you just created. It will recalculate and modify the RR to give you your 20 lb/hr spec of C2’s in the Crude C3 stream.
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Double checking the PERFORMANCE/SUMMARY again shows the C2s at exactly 20 lb/hr in the bottoms.
Go to PERFORMANCE/Column Profiles, to see the temperature/pressure/flow profiles in tower as well as the duties. Go to the Plots screen and you can plot any of the P, T, Flow, K, Property values or get them in tabular form.
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WORKSHEET gives you Conditions, Properties and Compositions of the terminal streams.
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Your PFD is now all dark blue indicating everything has been converged.
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4. Add a Reactor
First we have to go back to the Basis Environment .
And enter into the Simulation Basis Manager. Hit the REACTIONS Tab.
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Next, add the components involved in the reactions (if they’re not already there). We will simulate C2H2 being hydrogenated to both C2H4 and C2H6. Hit the ADD COMPS button and then the ADD THIS GROUP OF COMPONENTS button.
Now hit the ADD RXN button where a little window will pop up asking what kind of reactor to use. Since we do not have actual kinetic models, use CONVERSION. Double click the Conversion and you’ll get a screen to enter your stoichiometric data.
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Note that negative Stoic Coefficient indicates reactants and positive is products. Click on the BASIS tab and fill in the conversion of C2H2 to C2H4, say its 20% to C2H4 and 80% to C2H6. Put in 20% for the Co term and zero for the others.
Close the window and hit ADD RXN again to input the ethane at 80% conversion.
Remember to finish the BASIS (conversion). App A - 29
Close the window and go back to the SIMULATION BASIS MANAGER. Hit the ADD to FP button and then the ADD SET TO FLUID PACKAGE button.
You can now return to the Simulation Environment. Add the reactor by first clicking on the General Reactor icon. This will bring up a mini reactor type icon menu.
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Pick the “C” reactor for conversion reactor and click it onto the PFD.
Double Click on the reactor to get the reactor inputsheet. Fill in the name of the Reactor and the stream names. The feed to this reactor is the Crude C2s.
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Go to the Reactors tab and pick the Global Reaction Set.
Hit the RESULTS Button and go to Reaction Balance.
Nothing Reacted…………WHY????????????
Why doesn’t the reactor convert??????
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Because DUMMY, you forgot to add some H2!!!!!!!!!!!!!!! (just to let you know, it took me an hour before I realized I forgot the H2) Add some now with the BLUE ARROW. We have 120 lbmol/hr C2H2, say add 250 lbmol/hr H2, then connect it to your converter. As soon as you do, the reaction will go.
You can see that 24 mols/hr ethylene was made and 96 mols ethane --- the 20% and 80% conversions, respectively. Acetylene is completely reacted.
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Looking at the WORKSHEET tab under conditions, you see that the temperature went to 442°F and its all vapor.
Since you did not input a utility for the reactor itself, the reactor acts as an adiabatic reactor. However, the temperature rise that you see here of 342ºF (442-110) is not the true adiabatic temperature rise. Some of the heat also goes to vaporizing the feed, as can be seen in the above table. To get the true adiabatic rise, you need to first vaporize the feed at 110ºF and 300 psia.
The outlet temperature is now 745ºF, resulting in an adiabatic rise of 635ºF.
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5. ADJUST Block The ADJUST Block acts as a “controller”. You can control a specific parameter by varying another variable or unit operation. For this example, rather than specifying the bubble point for our DeC2 Feed Exchanger, we will set a temperature by varying the heat flow to the exchanger.
Go into stream bubpt and delete the vapor fraction. Then click on stream ref50 and put in 1 BTU/hr for heat flow. Now, click and drag the “A-diamond” icon. Double click it on and open up the connection screen.
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Hit Select Variable in the Adjusted Variable area and select the variable you want to manipulate, in this case ref50 Heat Flow.
Hit Ok and go to the target variable to set the stream bubpt Temperature.
Hit OK .
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Now put in the target Temperature you want, say 50ºF.
Now go to the PARAMETERS tab to enter the minimum, maximum and increment range for the heat flow to achieve your target, as well as the tolerance for your target. We will say we want to increment the heat flow by0.5 MMBTU/hr from a minimum of 0 to a maximum of 10 MMBTU/hr to achieve a target temperature of 50ºF +/- 0.1ºF.
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We may need more iterations. Close this and click on steam bubpt.
The temperature is 50.032ºF, well within your 0.1ºF tolerance. Open up the E-100 Heat Exchanger and go to the parameters tab and you can see the duty required to cool down the feed to 50ºF.
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6. Recycle Block The Recycle Block helps to connect the recycles more efficiently. To illustrate the use of the RECYCLE Block, I reduced the conversion of acetylene to 50% in the reactor and added a Component Splitter which preferentially removes acetylene for recycle while sending the C2’s forward. I also changed the specs on the column to be RR and C2’s in the Bottom.
Opening up the Component Splitter, connect the streams, put in the pressure and vapor fractions on the parameters page and define the splits (in this case all acetylene to the overhead, everything else to the bottoms).
Now double click the R-diamond and bring it onto the PFD. App A - 40
Open up the Recycle icon and FIRST THING --- CHECK THE IGNORE BUTTON!!!!!!!. This will ensure that your simulation doesn’t take off on you before you’re ready. While here, connect the stream Acetylene to the inlet and make up a stream C2H2 Recycle for the outlet.
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Now connect the C2H2 Recycle stream to your tower.
Open the C2H2 Stream and put in a “likely” composition/T/P. In this case, we are taking pure acetylene from our component splitter and it will be say, 400psia and 110F (this stream will be recalculated eventually). What you are doing here is getting the system started with a reasonable first estimate. When the feed to your recycle block is about the same as your effluent from the recycle block you will UNCHECK the ignore block. Since we know we will have 50% conversion in the reactor and we started with 3125 lb/hr C2H2 in the Fresh Feed, we know this recycle stream has to contain about 3125 lb/hr C2H2 as well. However to demonstrate a point, we will only put in 1000 lb/hr.
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Go to the Tower module and hit run and it will give a new solution with the additional 1000 lb/hr C2H2. The ACETYLENE stream now contains 2062 lb/hr C2H2 and the C2H2 Stream contains the same 1000 lb/hr C2H2 (because the Recycle Block is still being ignored). Go change the 1000 lb/hr that you inputted in the previous iteration with the new 2062 that was just calculated. For this second iteration, the ACETYLENE Stream is now 2593 lb/hr. You can repeat this procedure until you get closer and the turn the Recycle Block back on, or you can just do it now. Let’s see what happens. What happened, is that the recycle iterated until 3124.8 lb/hr C2H2 was recycled, rather close to our expected 3125 lb/hr. We could tighten up the tolerance even more by going to the Parameter tab of the Recycle Module. WHY DID WE DO THIS MANUAL ITERATION FIRST. To be sure that the rest of the program with its complicated specs would function properly. For example, we started out by changing the tower specs to RR and C2 Loss in the Bottoms. Previously we had Total Flow of Overhead and C2 Spec in Btm. If we kept that spec, the tower could never converge because it could not let the additional acetylene flow out the overhead because it was speced by material balance and it would not have exited the bottoms because of the spec. This way,entire if you forgot to change in the beginning, youis may not haveC2messed up your simulation. The itmorale to the story DON’T CONNECT THE RECYCLE UNTIL YOU ARE SURE THAT EVERYTHING ELSE IS BEHAVING.
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HYSYS Helpful Hints Azeotropes The tower module does not recognize you have an azeotrope unless you tell it, even though the properties package dutifully tells youthere is one. You need to do the following: Tower Module – Parameters – Solver – on the right side, check Azeotrope 2-Liquid Phases Whenever you suspect two liquid phases on a tray, for example when you have mesityl oxide and water and stuff, use a different solver routine. Tower Module – Parameters – Solver – Solving Method Menu Sparse Continuation Solver Keeping Windows Open When you want to keep a window open that has results while you restart the tower. For Example, you want to check the Performance-Results-Composition Table While you are changing specs on your Monitor screen. Tools --- Preferences --- Simulation --- UN-check “Use Modal Properties View Reports You can get much better summaries for material balances and unit operations by using the Workbook feature. Construct a Material Balance in lb/hr with NO decimal places. Tools --- Workbook --- Highlight Case --- VIEW This will open up a screen with some information regarding streams or unit operations. From here you will create your own summary reports. Place the cursor on one of the tabs and RIGHT click and hit SETUP WORKBOOK TABS --- ADD --- hit STREAM --- OK You can now modify what you wish to summarize, in this case MASS Balance. TAB CONTENT --- rename to STREAMS MATBAL Highlight the word VARIABLE --- DELETE --- then hit ADD This will open up a list of things you can get from the simulation. COMPONENT MASS FLOW --- ALL Components --- OK Highlight Format --- Hit the FORMAT button --- change decimal to 0 Close Window and you’ll have theMatBal. You can go back in and add T, P, other properties, etc. You can also hide streams (utility streams), andreorder the streams. You can also make the same summaries with theUnit Operations.
To print, go to the Blue Bar at top, right click PRINT DATASHEET, UN-click All Pages, click the little plus sign, CHECK your page and PREVIEW and PRINT.
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Physical Property Tables/Graphs You can get any physical properties for a pure component ora stream. First create the stream. Tools --- Utilities --- Property Table --- Connections
Variable 2 will be your X-Axis Variable while Variable 1 will be the additional lines on your graph The Y-Axis will 100F be theatProperty. Letspressure. get the Liquid phase heat capacity of variable. acetone between 0 and atmospheric Select stream that you created --- Acetone Properties Make Variable 1 Pressure, Variable 2 Temperature Pressure : Upper 14.7 / Lower 14.7 / Increments 1 Temperature : Upper 100F / Lower 0F / Increments 10 Now set the dependent variable (Cp) Dep. Properties --- click LIQUID --- pull down table Property Mass Heat Capacity Hit CALCULATE button The results are in the performance tab and you can get a table or a plot (right click PRINT PLOT).
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