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[mobezo2]

Hi all,

I'm trying to use Aspen to solve a problem for class. Basically I have a mixed stream of cyclohexanol, phenol, and cyclohexanone that I would like to separate. I'm trying to use DSTWU to do this, but every time I do this I get some sort of error. I've received errors that say that the bubblepoint calculation timed out after 16 iterations, that the minimum reflux ratio calculated with the underwood equation is negative and is being set to 0.1, not converging within 25 iterations, etc. I've played around with the values a lot to try to get it to work. I'm aware that my feed stream components form azeotropes, but shouldn't I be able to get it to run even if they form azeotropes? Or do these impact the calculations that Aspen does with the DSTWU, making them impossible.

To condense all this down to a more reasonable series of questions:

1.) Does the presence of an azeotrope in a stream prevent me from using DSTWU?
2.) How do I specify DSTWU correctly. Are there any rules of thumb about picking reflux ratios, recovery rates, condenser/reboiler pressures, number of theoretical plates?

Thanks!