Recovery of Ethanol from NaCl/NO3/Water mix 2

[burndirt]

I have a waste stream composed of:
Ethanol ~50% +/- 20% (denatured)
Water ~50% +/- 20%
NaCl ~1-3%
NO3 (nitrate) ~0-3%
organic compounds 1-3%

I would like to recover the (denatured) ethanol for reuse, and minimize the volume of other stuff to dispose of. (I can tolerate up to 30% water in the recovered ethanol, but I need to get rid of the nitrate, organics and NaCl)

Distillation is the most obvious route, but it is difficult to obtain a permit and it requires an explosion proof area which I don't have.

I have looked at membranes, but so far the ethanol and NaCl molecules are too close in size to separate efficiently.

volume is maybe 20-100L / Batch.

I don't mind to have an outside contractor deal take the material offsite to do the recovery, then return the ethanol.

Anyone have any ideas?

(present facility location Ontario, Canada... shipping any significant distance likely won't be economical)

Thanks

 

[dcasto]

freeze it. The ethanol will stay a liquid.

 

[burndirt]

Good idea, thanks, I will try that.

 

[bimr]

Why don't you just have a waste hauler take the material away and makeup with new ethanol?

That way you will not be susceptible to any contamination issues with recycled material.

Your waste volume seems to be so small that it would preclude trying to recycle. It would not be economical.

 

[burndirt]

Waste hauling is what we do now,
Presently I am at pilot plant scale and I need to find a good solution that is scaleable to full production.
When i get to full production then the quantities produces will be very large.
The cost to purchase new ethanol, plus the cost to dispose of the waste works out to a lot of money.

Distillation economics work out a little better at large scale, but i'm still hoping to find a more elegant solution. Even if I can just reduce the ultimate size of the still or the waste volume it will help.

Freezing is looking a little less practical than at first glance unfortunately.

 

[moltenmetal]

Distillation doesn't require an "explosion-proof" area: enclosed distillation equipment will be Class 1 Div 2- not normally hazardous, but hazardous in the case of emergency. The rules are not nearly as stringent nor are the costs of implementing such an area so high as if you just jump to the conclusion that the whole thing will be Div 1. Areas associated with filling drums etc. will be Div 1, normally/frequently hazardous ("explosion proof" per your parlance).

What about pervaporating off the ethanol?

 

[HariAugustine]

Have you considered electrolysis?

 

[alcoengineer]

Freezing the solution will be difficult as there's no differentiating layer between the water fraction and the ethanol, it will behave as a single phase and will have a freezing point determined by the ethanol solution.

I think you'll find distillation may be the best option (and probably the reason it's commonly used still to remove alcohol from solution)

I know that in Australia Dangerous Goods and hazardous Zones legislation keeps getting more and more stringent, so the cost of a recovery plant would have to be weighed up against the cost of dumping and replacing. You'd also probably need to register the still with the ATF (or whoever looks after alcohol excise regulations in the US)

If you're only after 20-100L then you'll find a small pot still (similar to those you can get for making "essentail oils") could be used. Seeing as this is only a pilot scale unit, the DG regulations wouldn't be anywhere near those required if you were making a distillation plant capable of 1000L/h.

I think you'll find you just need a small clearence area for the pot still. Better in a well ventilated area. Rather than requiring a completely explosion proof zone.

 

[dalcazar]

a little late answering here, but have you considered using a flash vacuum expansion process?

here is a link to a brazilian experiment (the undisputed kings of ethanol) where they used precisely that.

It might not get the kind of purification that you're looking for, but it's probably more energy efficient than distilling and can be done continously for the full scale operation.

 

[burndirt]

Thanks Dalcazar, I don't see a link though.

 

[dalcazar]

oops my bad, here it is

http://www.scielo.br/scielo.php?pid=S1516-89132005000400002&script=sci_arttext

 

[nouanda]

Flash is good idea, but it will be better if ran continuously. otherwise it will just be a single-plate-vacuum-batch-distillation...

I used to work in a company specialized in ethanol distillation, I kept some of the home-made spreadsheets. I can make a quick simulation (mass and heat balance) if I have time. What is your expected full capacity?

However, excuse my little experience, but I am doubtful about the capability of a flash to remove dissolved compounds, especially organics (it will depend on their boiling temperature and solubility in ethanol; if they are not too close to the ethanol's, you can work on the condensation temperature but maybe you’ll need an absorber). Same goes for salt and nitrates (I don't know their solubility in ethanol).

 

[nouanda]

dam! I didn't see the date of the post... I think I'm too late...