4 replies to this topic

[yaserbm]

hi all
we have stream of gas mixture ( CH4 + C2H2 + C2H6 + H2 ) and it has temperature and pressure of -50C and 12.8 barg respectively, we would like to install pressuer controller to drop the pressure from 12.8 barg to 5.88 barg in this situation how much the temperature going to be, any body can give me a method to calculate the resulted temperature?!! .
the stream has a mass flow rate of 32650 t/h of the above mentioned components, and it has molar flow of 1413.19 kmol/hr as well.
please help me in solving this issue

[Zauberberg]

Rule of thumb for Joule-Thomson effect is 1 degC temperature drop for each 2 bar pressure drop. This happens if the gas is below its maximum inversion temperature. Otherwise, the effect you will see by throttling is heating, rather than cooling. Each gas has its own maximum inversion temperature. Look in Perry's handbook for more information.

In your case, I'd expect gas temperature after throttling to be somewhere between -52 and -54 degC.

[yaserbm]

thank you Zauberberg for your effort,

any one can help me in solving this issue or can give an equation to solve this proplem.

[yaserbm]

what about if we used an equation that concern with adiabatic expansion.
can any body help

[PaoloPemi]

you can follow different ways:

1) use the estimated value given by Zauberberg

2) calculate Joule Thomson for that specific composition and operating conditions, then estimate the final temperature (Joule Thomson is the derivative vs. pressure)

3) solve a adiabatic flash, supposing there is no condensing you have to solve for H at different pressure, not difficult even with a EOS calculating enthalpy departure, if there is change of phase you need to solve the n additional VLE equations.

This is a problem easily solved with a simulator, if you prefer Excel there are libraries (see for example Prode Properties) which can do all that.