Aspentech’s Hysys: Fluid Package (Thermodynamics) Notes

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Aspentech’s Hysys is a process simulation tool. You always have to pick a “fluid package” when you use the program: a thermodynamic method it will use to calculate properties, especially vapour-liquid equilibria. I watched an old "webinar" (presentation given through the Internet) on their property packages and took some notes.

You can combine this post with the Hysys manual, the Hysys property package wizard, Aspentech Support’s advice, and books on simulation, and put it all together to choose the best package in each case. If you are in doubt Aspentech Support can always give you personalized advice. They are really quite good at quickly suggesting the best method to use.

One trick to remember is that you can use different fluid packages and different component lists in different parts of the simulation. You can have a Peng-Robinson Package running the calculations for your hydrocarbons, and the ASME Steam Package running the steam and water calculations.

Here are my notes from the webinar:

-Hydrocarbons: normally use an Equation of State method
-Vapour pressure models are OK at low pressures
-Activity coefficient like NRTL is poor model for hydrocarbons

Equations of State:
-Peng-Robinson is most enhanced in Hysys, highest T & P range, has special treatment for key components, largest binary interaction database: good standard for hydrocarbons
-PRSV: extends PR to moderately non-ideal systems and better represents poor components and mixtures. Adds a new parameter to the equation. Slower calculation speeds than Peng-Robinson
-SRK: modified Redlich Kwong model. Similar accuracy/use as Peng Rob, but in Hysys SRK has less enhancements than PR.
-PR-Twu, SR-Twu for hydrogen solutes? In liquid hydrocarbons
-TST: hydrocarbons with non-ideal components (used in glycol package)
-GCEOS: generalized cubic EOS for user to add their own parameters. Use this to build your own model when necessary
-MBWR: a modification of the old BWR models: 32 parameters, more empirical approach, so it works very well in the range where it has data
-Lee-Kesler-Pockler: modified BWR for non-polar substances, mixtures
-BWRS: modified BWR for multicomponents, requires experimental data
-Zudkevitch Joffee: modified RK method for VLE, systems with H2
-Kabadi-Danner: modified SRK with Liquid-Liquid-Equilibrium calcs for liquid H2O-Hydrocarbon systems, especially dilute, parameters must be tuned to experimental data
-Sour PR/SRK: sour water systems with H2S, CO2, NH3 at low to moderate P

Vapour Pressure Models:

These models OK for hydrocarbons. Historically they were used since computationally they are easier. Now with modern computers EOS models are easy to run, so vapour pressure models are used less often. However, Braun K10 is still good for vacuum units.
-Modified Antonie: OK for low pressure ideal systems
-Braun K10 Model: strictly applicable to only heavy Hydrocarbons @ low pressures
-Esso K: only heavy Hydrocarbons @ low Press

Semi-Empirical methods:
-Chao-Seader: hydrocarbons if T = 0-500C, P<10,000 kPa
-Grayson-Streed: Chao-Seader extention with emphasis on hydrogen, good if heavy hydrocarbon with lots of hydrogen like hydrotreaters. Is recommended for vacuum units.

-Glycol Package: TEG circulation rates, purities of lean TEG, dew points and water content of gas stream used in natural gas dehydration. Use PR for MEG, DEG, but be careful of results outside of standard range
-Clean Fuels: Thiols and Hydrocarbon
-OLI: electrolyte
-Amine: sour sweetening with amines
-Steam tables: ASME, NBS

Binary Interaction Permaters:
-Are many defaults, others estimated by BP & Density, most user can overwrite

-For hydrocarbons and hypocomponents use PR, SRK, or other EOS
-Vacuum unit – GS, PR, BK10
-High-hydrogen units like hydrotreaters – GS, PR, PR-Twu, or ZJ
-Sour gas sweetening – Amine
-Sour water – Sour PR/SRK
-Clean fuels for sulphur components & HC
-Utilities with water – use one of the steam tables. Steam tables are only for 100% water systems but are the best choice for these systems


2010-11-12 - Added note that multiple fluid packages can be run in the same simulation

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12 Responses to Aspentech’s Hysys: Fluid Package (Thermodynamics) Notes

  1. hari says:

    plz specify where the EOS limtations in terms of pressure and temperatures

    remaiing things are ok

    • admin says:


      If you look in the Aspentech documentation Simulation Basis Reference Guide, Appendix A, you will see some guidance. Also, if you go out of bounds the stream should turn yellow after converging and you should get a warning in the trace window.

  2. chan0458 says:

    “One trick to remember is that you can use different fluid packages and different component lists in different parts of the simulation. You can have a Peng-Robinson Package running the calculations for your hydrocarbons, and the ASME Steam Package running the steam and water calculations.”

    How do i accomplish this and how can i download the documentation?

    • admin says:


      When you set up your simulation, you always have to set up a component list and a fluid package (aka thermodynamic method) before you can start. In the windows where you set these up, you can add additional fluid packages and component lists. For example, the fluid package called Basis-1 could be Peng-Robinson and have Component List-1: Methane, Ethane attached to it. Meanwhile, Basis-2 could be ASME Steam and have Component List-2: Water attached to it.

      Then, in your simulation, double-click on any stream like you were going to define it’s properties. At the bottom of the main window there is the fluid package being applied by the stream. Click on it: you should find a drop-box that lets you change from Basis-1 to any of the other fluid packages you created. When you pick a different fluid package, it will automatically consider only the components attached to that package.

      Note that if you try to combine streams of different packages/component lists you’ll get into headaches.

      Usually this is on the Aspentech CDs. If you work at a large company, probably the I.T. group will install the documentation in your Windows start menu. It’ll be something like Start>Aspentech>Aspentech Documentation. You might also check the Aspentech Support website, once you create a profile you should be able to find the latest documentation pretty easily.

      Hope that helps!

  3. vahid says:

    what is differences between peng-rabinson hysys and peng rabinson standard?

    • admin says:

      I believe I remember the distinction: PR Hysys includes Aspentech’s various modifications and improvements to the Peng Robinson method, such as improved modelling of water behavior. In general you would always want to use PR Hysys, because it will give you more accurate and realistic results.

      PR standard strips away these improvements and uses the original PR, like you would see in a textbook. Why would you ever use standard? Maybe if you wanted to match results to some other tool using basic Peng Robinson.

      …but that is from my memory. I’d bet the Simulation Basis Reference Guide, Appendix A, will say for sure.

  4. Chryselz says:

    Hi, may i inquire the suitable fluid package for cryogenic air separation?

  5. jo says:

    you may try using seader and carlson’s reccommendation:)

    • DY says:

      Hi Jo,

      I am also trying to find the suitable fluid package for cryogenic air separation. With your kind advice, I followed Carlson’s recommendation and the flowchart led me to decide on NRTL or UNIQUAC fluid packages. (Polar -> Non-electrolyte -> P LL (Yes))

      May I know if you arrived at the same decision?

      However, from this source:, the recommended packages are Peng Robinson-BM, RKS-BM, Peng-Rob, RSK.

  6. arel says:

    can someone help me?i’m new in using aspen plus software.therefore,can someone explain in detail about HYSSRK fluid package in aspen plus 7.3?i really need the answer ASAP..thanx.pls reply to my email as per attach.

  7. dwyte says:

    Hi admin,

    What is the difference of NRTL fluid package in HYSYS to Cubic Plus Association (CPA) EOS?

    2. For a water-methanol separation system, is NRTL the most suited fluid package to use?

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