fuel ethanol production using cyclohexane as an entrainer 1

[tughanite]

I run a 60Kl per day fuel ethanol plant. Since 1982, benzene has been used as an entrainer. In June 2003, I switched to cyclohexane for health reasons. So far I have only managed to produce no more than 30Kl a day and with some struggles.
I know the decanting is not ok. Am failing to have the interface lower than the decanter overflow pipe. This means I am sending water to the dehydration column.
Some one out there who has worked with cyclohexane and had good results? Or maybe with cyclohexane the volumes are lower? I have lost two months of production.
Desparate!
Susan

 

[25362]

tughanite, I haven't had any experience with drying of fuel ethanol, but have dealt with other azeotropic distillations.
From tables it appears that the ternary azeotrope with CHX at 62.6 deg C contains less water, not more, than the one with bz. at 64.9 deg C.
If I got them right the published % wt figures for water/ethanol/carrier are :
7.4/18.5/74.1 and 4.8/19.7/75.5, for bz and CHX, respectively.
In order for the heavier layer to have a larger volume than expected one should look at the partition of ethanol, between water and CHX at the prevailing temperature. It could be checked in the lab, by mixing the components in the expected proportions while looking for the time taken for phase separation and the formation of a cleancut interphase.

It is possible that the mutual liquid-liquid diffusion of water, ethanol and carrier is slower with CHX than with bz. at the prevailing temperatures.

Other things equal, such a simple lab bench trial would help you to understand what's actually happening in the plant's decanter.

Good luck.

 

[PierreSTRAUCH]

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