Petroleum Characterization

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  • I am not sure what I am doing wrong. When I try to add an oil characterization
    via the Distillation Curves Petroleum Characterization Utility I use "True
    Boiling Point", with a specific gravity (60/60) of 0.88. I enter my TBP curve
    on the next step (Step 2 - Experimental Data) but when I hit "next" for "Step
    3 - Data Plot" nothing shows up in the window so I hit "next" for "Step 4 -
    Configure Pseudocomponents" I'm not sure what to do here so I hit "next" and
    get the following error:

    DWSIM generated an unhandled exception.

    In most cases you can continue to exe3cute DWSIM normally. If you choose to
    close the application you still can save the opened simulations.

    If the error is unrecoverable click the 'Close' button. It will not be
    possible to save the opened simulations. In this case, check the 'Restart
    DWSIM' box to restart the program

    Please help me figure out what I am doing wrong?

    My email:



  • Hi Joseph,

    I`ve found a bug on this utility (the update graph event was not firing). It
    will be fixed on the next release (in a few weeks). Thanks for your help and
    sorry about that. ;-)


  • Thanks I'll give it a try

  • Something is wrong with the link.

  • Seems to be working now! Thanks! This is a great concept for open source. I am
    in the process of evaluating it for our small company. If all goes well, I'll
    talk with my bosses about donating some to the cause. Thanks again.

  • Now it seems to be stuck in a loop on Step 6. It keeps flashing a small window
    with a blue 'time wheel' that seems to be counting down and says "Calculating
    Adjustment Factor Please wait..."

    As a note of interest I moved the Small DWSIM window out of the way and
    clicked on next again on the "Step 6 - Methods Correlations" page and a second
    small window comes up doing the same thing.

  • It may not be stuck, that's because this is a really heavy calculation
    (finding optimum values for acentric factors and rackett parameters). If it is
    taking too long you can uncheck the two checkboxes on Step 6's panel and then
    you should go straight to the results window.

  • I let these two windows cycle for about 5 - 10 minutes and they finally went
    away but the same error I described in my first post popped up. I hit continue
    and it looked like the characterization worked all right. It was apparently
    the 2nd pressing of the next button that brought up the error message. So, I
    hit the 'Previous' button and it went to the small 'cycle' window asking me to
    please wait. This time I was a bit more patient and let it finish without
    touching anything else. It seems to be working properly now.

  • It should not take that long, maybe you used the 50-component default setting,
    didn't you? Sometimes the calculation fails, but in most cases it works
    fine... that's why I left it enabled by default.

    If you need more help, just ask. :-)


  • Other steady state simulators offer the option of inputting "Light Ends"
    (usually C1 through C5). I have not seen that on your "Petroleum
    Characterization Tool". I would think that would reside somewhere in 'Step 1.

    I also notice that you do not have an option for °API Gravity for density. In
    the Oil industry this is the most common form of density. The formula is very
    simple, and I would recommend putting it in as an option for future builds:

    °API = (141.5 / SG) - 131.5

  • Yes I did use 50-component default setting.

  • I"m also not sure how to "Define cut temperatures" Can you elaborate on that
    for me?

  • Some time ago I tried to implement the light ends feature but it was just too
    time-consuming and hard to do, so it was not worth it (for me). As a
    workaround, you can add another stream with your light compounds and mix it
    with your C7+ stream and the same effect should be achieved.

    With "Define cut temperatures" you can input a list of temperatures (one per
    line) and the pseudos will be generated in such a way that each one will have
    a boiling point calculated as the average of two temperatures that you
    informed on the list.

  • OK, I loaded the beta version, but the Logical Operations "Adjust, &
    Specification" are empty. Nothing in the Properties tab. Is there something I
    am doing wrong? I want to control the flow of the light ends to vary with the
    flow input of my Crude stream.

  • Hi Joseph, they aren't showing anything in the property grid, indeed. Will
    check it this evening and update the beta ASAP.


  • Thanks Daniel,

    Just some things I've noticed:

    I don't believe I am doing anything wrong. I was able to mix the pseudo stream
    with the light ends as you suggested above, but when I tried to mix water with
    that stream in the next step, it would not converge. I am trying to simulate
    the front end of an oil refinery and then will add a distillation column. I'm
    using a study manual I got from attending a HYSYS training course a few years
    ago. I'm trying to see how the answers in DWSIM compare to the big boys.

    As a separate item I noticed that when I try to define a stream if I don't
    specify a volumetric flow rate first, I get "Infinity" as the calculated (I
    was first specifying a lbm/h) volumetric flow rate. If I then specify a
    volumetric flow rate the mass flow rates convert as expected and then I can
    enter a mass flow rate and get the volumetric flow rate to convert as well.

    Also, when I tried to flash my water stream I set the specifications to
    Temperature & Vapor Fraction. But when I entered 1 as the vapor fraction at
    60°F I got Infinity as the pressure and when I set it to 0.99999 I get 0.21076
    psi. When I vary the fraction anywhere from 0.55 up to 0.99999 I get 0.21076
    psi as the calculated pressure. If I lower the vapor fraction below that I get
    NaN as the pressure, Specific Enthalpy, and Specific Entropy, and the flow
    rate goes to Infinity.

  • Hi Joseph, About the water mixing, when you do that you should use the three-
    phase flash algorithm - go to Simulation Settings > Thermo > Advanced Settings
    and select the three-phase flash with water as the key compound for the second
    phase. Then see if it calculates ok.

    The infinite volumetric flow rate is tricky... I also noticed this some time
    ago. It seems that it calculates only from the second time and on. I'll take a
    look at it. Finally, when you tried the TVF flash, was water present in the
    mixture? If you send me the simulation I can investigate further. My email is
    danielwag at

    DWSIM always had some problems with flash calculations and petroleum
    fractions. It is difficult for my algorithm to converge when there are some of
    them in the mixture... that's mainly because of the proximity of the boiling
    points. In this case, the less pseudos you have, the better.

  • Just fixed the infinite volume bug. Waiting for you to send me your simulation
    to see if there is anything else to fix.


  • OK, I tried that and it seemed to converge OK, but when I look at the values I
    get infinity for the volumetric flow rate out of the first mixer (I also sent
    you the file). I believe this is propagating through the rest of the
    simulation because the energy required to heat this stream from 78°F to 145°F
    is 13,427,192,033 Btu/hr which seems kind of high.

  • Is there a way to change what displays when you float over objects and

  • I'll upload a new beta version in a moment that fixes the mixer. It was my
    fault - I was playing with the solver code and ended messing up everything..

    About the high energy value, maybe it is because you have 1300000 lbm/h on
    your oil stream, that's a lot... and finally about the floating table - no,
    its data is fixed, but you can click with the right mouse button over the
    object and go to "Table" > "Configure" to select items to show in a table on
    the flowsheet when you go to "Table" > "Show" (after defining what to show).

    I would like to thank you again, Joseph. Since I don't have time to do
    validation as I wanted to, I rely on user feedback to fix bugs, and you are
    being very helpful on that task. ;-)


  • Cool, I'll give it a try. Do I need to uninstall and then install? Or can I
    just install over the old one?

    I'm glad I'm not being to pesky. I was worried about that.

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