Dewpoints and bubblepoints in Hysys

[JackWhite]

Hello forum,

I performed a few experiments in hysys with a mixture of methane, ethane, water and SO3. I tested the envelope of this stream, and compared it with databook-case study calculation keeping the pressure and vapour phase as independent variables (P=1 bar, vap phase=0 or 1 (bubble point or dewpoint))and temperature as a dependent var.

The results? The envelope gives only dewpoints and they are completly different from var-calculation. The envelope seems to ignore the presence of water in the system.

I tested this for several property packages (more than i had to): PR, PR-sour, PR-twu, SRK, KD, and others. The differences are subtle comparing most to eack other. PR and PR-sour gives identical results.

Therefore, i would advise anyone using hysys for dewpoint or bp calculations to consider the property package they use, and the nature of the system (water and SOx, H2S, etc. need special attention). The curves also behaved unnaturally for high temperatures and pressures (over 10-20 bar).

Good luck, hope this was helpfull.

 

[chemebabak]

Engineers,

Just as important as the property package selection described by JackWhite is the user's responsibility and understanding of basic Thermodynamics and Chemical Engineering principles.

I have met far too many engineers, both juniors and highly experienced senior engineers, who just punched some numbers into the program (Hysys, excel or even a pocket calculator) and reported the results as the final answer. It is as if they are playing video games. If the program beeps, then they know that they made a mistake.

Just as JackWhite recommends, please review the data and exercise good engineering judgement to ensure that your results are correct.