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Distillation for sugarcane molasses &


david_october

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Hello All,

Has anyone heard of using sugarcane molasses for distillation directly?

and using ready made 96% alcohol from sugarcane molasses to make alcohol of up to 98%?

It's for a question of my customer.

The equipment he will use is a Copper Still with 2x16 plate Vodka column.

Thank you.

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Assuming we are at the standard temp of 20 C, it is impossible to achieve 98% ABV by traditional fractional distillation.

Then how about a Still of upto 32 trays of bubble plate? It's said even a Still of 20 trays will be able to achieve 98% ABV.

post-9943-0-09563900-1454044604_thumb.jp

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The attached graph shows the equilibrium data for ethanol/water mixtures. Unfortunately the scales are in mole fractions, but when expressed as ABV or mass % the conclusions remain the same.

The X axis is the concentration of ethanol in the liquid and the Y axis is the concentration of ethanol in the vapor when boiling at atmospheric pressure (760 mmHg). For example, if you boil a 10 ABV% liquid, which is about 0.033 mole fraction the vapor that will be generated will be at a mol fraction of around 0.2, which translates to an ABV of 46%. This is what you would achieve in a simple pot still with no trays and no reflux.

As you move across to the right on the X axis the vapor concentration continues to be above the liquid concentration until you get to a mole fraction of 0.8943 (=97.2 ABV%). At this point the vapor generated is at exactly the same concentration as in the liquid. This point where the liquid and vapor have the same concentration is called the azeotrope. Because there is no enriching occuring at this point you can never go beyond this point by normal distillation. The only way to to get beyond this point is to add another chemical as an entrainer. Cyclohexane is often used for this purpose.

To get to the azeotropic concentration of 97.2 ABV% would require an infinite number of trays or infinite reflux. The practical limit, with an economic reflux ratio, is about 96% ABV.

post-1693-0-09019000-1454059430_thumb.gi

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