Regarding finding the minimum number of theoretical plates
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The minimum reflux ratio was determined to be 2.7, and an upper limit of 200 was set for the reflux ratio. An attempt was made to determine the minimum number of theoretical plates through sensitivity analysis, but the results were incorrect, as shown in the figure below. This distillation column is used to separate systems containing azeotropes; is it possible that this is related to the inability to determine the minimum theoretical half?
Can sensitivity analysis be performed on the strict models? I haven’t done this yet. Is the purity at the top and bottom of the control tower unchanged now?
It has to do with the design specifications you set. If you specify requirements for distillation, then you need to conduct a sensitivity analysis on the number of plates in the distillation section, rather than the total number of plates. Of course, it’s fine to analyze the total number of plates as well, as long as the number of feed plates changes accordingly. If your simulation matches what was described, then the graph can provide some insights; the minimum theoretical number of plates is around 18–25. Adjust the range of the sensitivity analysis to 18–25, and first run the process with one of these values (preferably 25, as 18 might not lead to a convergent result). Once that works, then carry out the sensitivity analysis
I added a calculator module, setting FSTAGE=0.8*NSTAGE; therefore, the number of feed plates should vary depending on the number of tray stages. Following the method you suggested, I tried it with 28 panels – the program ran properly – but when I changed the number to 27 panels, an error occurred. If the 28th rapid stage represents the minimum theoretical number of stages, then the corresponding reflux ratio is around 42. However, the upper limit for the reflux ratio that I have set is 200 – is this correct? See attached figure
The control is to keep the content of the reformed components at the top of the tower at no more than 0.001
Try adjusting it in manual mode; set it to 27. The position of the inlet plate should not be at 0.8×27 – try using the optimal position. Will the reflux ratio become very high? If it does, then that’s roughly the minimum theoretical value
Additionally, since you have already determined the minimum reflux ratio, you can also try finding out how many trays there are when using 1.2 times that minimum reflux ratio; this number is approximately twice the minimum theoretical number of trays, which can be used as an indirect way to verify the result
Oh oh. . Okay, thank you{:1_90:}
Look at this: with three substances, shouldn’t there be three sets of binary interaction parameters? Now that NRTL is being used, there are only two sets of parameters; the Aspen database does not include the other set. In this case, do I need to find experimental data from others (from published literature) in order to determine the property parameters? Or are just two groups okay too? Is the third group necessary?