minimum reflux ratio

[thubelihle]

i read a paper that indicated that if l hold the distillate and bottoms purity constant and start increasing number of stages, reflux ratio will decrease till it hits a constant value, where an increase in number of stages has no effect on the reflux ratio. In this case l increased the number of stages till 160 and the reflux ratio did decrease, but after 160 stages the column did not converge. My question is that the column should not it converge for any number of stages as long as they are more than the minimum number of stages. I also tried to put infinity number of stages, 300 maximum for COCO, as at infinity number of stages we get the minimum reflux ratio, but the simulation did not converge. How so, thanks? Attached is the file.

[jasper]

The case you attached converges. I see you set up a parametric study (which works if you remove the output parameter for Feed1 stage). What is the outcome of that?

Please note that the 300 stage limit is ChemSep's, not COCO's. Should be sufficient for most real-life problems.

[thubelihle]

Thank you sir for your knowledge!

[thubelihle]

The above case did converge as the number of stages is 160, but above 160 it does fail to converge as shown in the attached file. Also l am trying to calculate the critical pressure of a stream using the calculator, but there are options of critical temperature and pressure of the mixture in a stream. Thanks

[jasper]

The critical pressure or temperature of a mixture (there can be multiple critical points in fact, so the answer is not unique) is not something that is straight forward to calculate, and CAPE-OPEN does not provide a way to communicate this information from the thermodynamic package to the simulator.

[jasper]

The convergence issues are not there when using internal ChemSep thermodynamics. The issue is being looked into.

[hkooijman]

Can you please try again with the new version of ChemSep LITE 7v41 to see if this has resolved the issue?
Harry