In the reaction
CO + 2 H2 => CH3OH
this is interpreted as
Kp=[CH3OH]/[H2]^2/[CO]
where [] denotes mass concentration in kg/s as this is selected for the reaction basis.
The reactor results concentrations
[CO]5.867786081kg/m3
[H2]1.689679154kg/m3
[CH3OH]0.003660365kg/m3
giving Kp=0.003660365/1.689679154^2/5.867786081=0.000218495
which should equal at 573.51995 K:
Kp=10^((5139/573.51995)-12.621)=0.000218502
So it looks like the solution is ok for what is specified. But I reckon that the molar concentrations are to be used (Molality) which gives a different answer altogether.
Now a quick scan of the article reveals that the Kp values are only used in eq (4), so I am not at all sure whether they are intended to be used as equilibrium constants? (it might have been clarified in the text, I did not read the entire article).
The basis issue would have been apparent immediately from the report, which goes lost during persistence, resulting from transferring the unit operation back from the solution thread into the main thread (it was available by selecting Calculate Unit from the unit's context menu). Also from the units of measure of Kp in the reaction package it shows. The full list of reaction basis is documented here:
Now - let us see why the report was not available: ah - yes, this was a persistence problem introduced in COUSCOUS 2.5.0.1 and is now solved (fix available via CUP).
Finally, in your mail you state that selecting fugacity as the basis does not work. This makes the unit of measure of the equilibrium constant 1/Pa^2 (as the fugacities are in Pa), which would make the average order of fugacity about 70 Pa? I can imagine this will indeed not converge at 50e6 Pa. Check the units of measure there please.
Hope that helps - apologies for the report not being there to point out the used units of measure in the first place. Thank you for reporting the problem.Statistics: Posted by jasper — 08 January 2013, 13:21
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