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Hey Guyz !!

I am have to design a distillation system for ethanol production. The mixture is ethanol and water and I need to use McCabe Thiele method.

It a paper design so I need to assume all the parameters. I want to design for 10% ethanol concentration in the feed which would give may be 90-95% ethanol after two steps of distillation.Can anyone suggest the values of the various parameters used in the McCabe Thiele..??

Please reply as soon as possible !!!

Thanks !!


Neha

[katmar]

The first thing you need if you are doing a paper based McCabe Thiele design is good binary VLE data. An excellent source for this is at http://www.cheric.org/kdb/ Open the "Hydrocarbons" page and then search for the components ethanol and water. I believe doing paper based McCabe Thiele calculations is an excellent way to develop an appreciation for what is actually happening in the column.

When you specify the concentrations of the ethanol you must include the basis. Distillation calculations are usually based on molar concentrations, but in the plant the concentrations could be given in mass or volume terms. 10% would be a fairly typical concentration from a fermentation process if it is in volume terms. For ethanol/water there is a large variation between the different bases.

The number of stages you will need will be much more than 2. Typically an ethanol rectifier would have about 8 theoretical stages in the stripping section, and about 35 in the rectification section. Actual trays would be about 50% more than this. These numbers are based on a reflux ratio of about 5, and a top product of 95% volume. The number of trays will be significantly less if you only need 90% volume as the product. You will see how the pinch point develops when you plot your McCabe Thiele diagram.