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  1. OldDoc

    Calculate the condensation temperature of any gas mixture at a known pressure

    Wilson correlation ln(Kval) = ln(Pci/p)+5.373*(1+Aci)*(1-Tci/t) can produce decent results with (light) hydrocarbons, however your mixture may include water or other non-hydrocarbon fluids and a EOS (there are many available in process simulators and thermodynamic libraries) can produce much...
  2. OldDoc

    Hydrate formation temperature with Prode Properties

    no experience with polymers etc. injected into water phase (LDHI), we use mainly (traditional) methanol or glycol based inhibitors ...
  3. OldDoc

    Hydrate formation temperature with Prode Properties

    thanks all, apetri, if possible I would stay with base version which probably includes more than I need (except for inhibitors) PaoloPemi, thanks for advice, I'll test the method. georgeverghese, I wish to evaluate a few polar compounds (alcohols and glycols which work as inhibitors by...
  4. OldDoc

    Hydrate formation temperature with Prode Properties

    In some cases I need to calculate hydrate formation temperature ( or hydrate formation pressure ) for natural gas mixtures + inhibitors as methanol , glycol etc. I have the base version of Prode Properties 1.2C4 which includes two models (PRX-NRTL-HV + PRX-CPA-NRTL-HV) for hydrates, Prode...
  5. OldDoc

    Calculating tank cooling upon venting

    HazGas, if you imagine a single molecule (no interactions with other molecules) expanding from initial to final conditions the path is isentropic, a problem, simulating a real behaviour, is that each molecule interact with each other and the final result is difficult to estimate, simulators...
  6. OldDoc

    Discharge gas Temperature for Poly-tropic Process and Adiabatic Process

    are you comparing isentropic vs. polytropic ? "http://en.wikipedia.org/wiki/Gas_compressor" consider the equations for ideal gases, for real gases things are a bit more complex.
  7. OldDoc

    Gas-liquid equilibrium rates, Ki = yi/xi

    tables with Kvalues were common in old days, my copy of API TDB includes a large collection, you may find some data on GPSA chapter 25 "Equilibrium Ration (K) data" Another possibility is to calculate kvalues yourself with a EOS, details are shown on textbooks as The Properties of Gases adn...
  8. OldDoc

    Steam Properties algebraic approximation

    in Matlab and Mathcad for Steam properties such as dH/dP , dH/dT , dS/dP , dS/dT , dV/dP , dV/dT .... I utilize IAPWS95 model and a process library (Prode Properties), IAPWS95 is the most accurate but it is complex to code, you may find more easy IAPWS97 or use an external code as I do.
  9. OldDoc

    ethane compression from 21 to 120 bar

    dcasto, out of curiosity, how have you calculated those values ? for pure ethane, single polytropic stage with polytropic eff. 75% tin 15 C pin 20 Bar.a pout 120 bar.a I get a tout of about 149 C (about 50 C less)
  10. OldDoc

    Dynamic depressurization in Hysys

    indeed it seems a strange result, perhaps in these cases it would be preferable a step by step solution as suggested by apetri, at least you will be able to evidence the problem (if any), unfortunately a (black box) unit allows only a limited access and control.
  11. OldDoc

    PSV discharging temperature (valve outlet)

    thank you all, very interesting thread !
  12. OldDoc

    Aspen Plus

    I would recommend to evaluate the list in this page http://en.wikipedia.org/wiki/List_of_chemical_process_simulators there are many good tools available with both a graphical interface and not, I would presume you are a chemeng, the best you can do is to download free/trial copies and make...
  13. OldDoc

    C6+ characterization for natural gas

    if the dew point is far from minimum operating temperature (say 3-4 times the max error) perhaps you may persuade the client to accept a correction with results from regular laboratory analysis, the same if there are really very small amounts of heavy components, differently better to budget a...
  14. OldDoc

    C6+ characterization for natural gas

    everything mentioned in sales contract is significant, if not perhaps GPSA manual (or equivalents) may provide some hints. The point is that specifications parameters may include compositions, contaminants, water content etc. in addition to dew point, as example we have a maximum content for...
  15. OldDoc

    C6+ characterization for natural gas

    if your gas contains a significant amount of octane, nonane, or decane you must consider all these heavy components when calculating dew points, differently you get uncorrect values, the characterization works only when all these components (with a significant amount) are included...
  16. OldDoc

    chilled mirror or software : this is...

    the cost of the software is not a problem providing it can replace the mirror which has a quite large cost due to maintenance... We have tested two software packages, once properly tuned (settimg the same parameters) they give exactly (< 0.5 K) the same values (for dew points, cricondentherm...
  17. OldDoc

    chilled mirror or software : this is...

    thanks. I must agree with your comment, there are no ways to get the real dew point as the mirror needs some content of condensate (70 mg.m-3 is a std. value) to react, also mirrors can show errors of 5-7 C (MCMI v ACMI see the NPL REPORT AS 3), GC-EOS packages in general could be very accurate...
  18. OldDoc

    chilled mirror or software : this is...

    thank you for the comments, we have a in-line mirror which is expensive and difficult to maintain, also I am not sure about reliability (laboratory gives quite different results, 3-5 degrees difference), we are considering alternatives, our in-line GC is limited to C6 but we get regularly C6+...
  19. OldDoc

    chilled mirror or software : this is...

    we have a chilled mirror system for monitoring natural gas (mainly C1) dew point, it should provide two/three degrees (Celsius) of precision, we have also a in-line gas chromatograph for composition (C1-C6+) , I got a suggestion to put the composition on a computer, calculate the dew point and...

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