opperating a distillation column far from flooding

I know that flooding will ruin the performance of a distillation column. There are many correlations (Eckert, kister, billet, etc.) that will tell you when a column will flood based on your fluid conditions. Most design guides suggest choosing a diameter that will lead 70-80% of the flooding condition. This makes sense as the size of the column (IE, the cost) is as small as possible while still giving you a 20-30% margin of error. 


However, what if due to other constraints you want the column to be large so that it is only operating at 10% of the flooding conditions (IE, a much larger diameter than normal). Would this column still operate? Is this type of operation just avoided because it is not economically practical and a smaller column would do the same thing operating closer to flooding? 




Using a much too large column means you loose a lot more heat through its walls, meaning it will take longer for the equilibrium temperature/concentration gradient in it to form, and the destillate comes not only later but also considerably slower.


*And* you'll have to put more power into heating the still, with following danger of decomposition, unwanted side-products, etc.


If you use an expensive column with silvered vacuum insulation, this effect might not be too large even at only 10% of the maximum capacity. I wouldn't want to judge without trying, though.


Education and experience taught me to always use the proper type and size of equipment. It's faster, cheaper, and gives higher yields. I you have a large column that costs thousands, you can sure afford an additional smaller one at a tenth of the price, can't you?


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