A Posse ad Esse. From Possibility to realization.
Join Date: Apr 2009
Location: River City, USA
Progress has been made. I picked up a dozen of the stainless pot scrubbers at Hongs Restaurant Supply for $5.99, and after I first pulled them apart, I rammed them firmly into the column, using a hard wood dowel.
They are held between the two combination Viton gasket/10 mesh screens at each end of the column, which I scored from brewerygaskets.com. I chose Viton because of its compatibility with hot ethanol.
I recommend this Cole Palmer site, for choosing alternate materials from what I have used here, should it be more readily available:
http://www.coleparmer.co.uk/Chemical-Resistance?referred_id=1033&mk wid=smji51NEu&pcrid=1519596864 5&gclid=CNfn8YSciLECFWYbQgodGU VoPw
The science behind the 1 meter column packed with stainless ribbon, is that the large surface area of the ribbon continually cools the rising vapors until the point that they cool to a liquid and rain back down the column.
Eventually the vapors will heat up the insulated column, and they will rise higher and higher in the column, until the column and its contents reach thermal equilibrium.
Because of this continuous refluxing action, when it reaches equilibrium, the lowest boiling point vapors will be at the top of the column, and the heavier vapors below them in the column.
Because I would like to do this in a 1 meter column, I have elected to install an Alhin refluxing condenser above the column. This refluxing condenser condenses everything that rises above the packing, so that a shorter column can be used.
There is a digital thermometer in the cross below the refluxing condenser, with the probe far enough back, so as to not be affected by the temperature of raining condensate. It tells which constituent is at the top of the column, by the temperature of the vapors.
Bleeding off the fractions:
There are a couple of standard ways to bleed off the fractions, with one called liquid control, and one called vapor control.
With liquid control, you capture some of the liquid raining down from the reflux condenser at the top of the column and bleed it off.
Instead of liquid control, I will be using two different vapor control techniques with this fractionating still. I will detail them below, but the principle with both liquid and vapor control, is that if you provide a means to extract the liquid or vapor at the top of the column at a slow enough rate, the column will continually reestablish equilibrium, and you can bleed off that constituent.
The rising temperature tells you that the next constituent, or an azeotrope of that constituent has reached the still head.
Providing a bleed path using vapor control:
You will notice that besides the Alhin reflux condenser at the top of the column, there are two Liebig product condensers that come into play, depending on where the vapor stream is coming from.
Path A is created by cracking the valve on one leg of the cross, which allows some of the vapors at the top of the reflux column to exit through the Liebig condenser, where it is cooled to a liquid.
This technique relies on the fact that water steam is lighter than air, at 0.6 its density, while ethanol vapors are 1.6 times as dense. That means that given an opportunity, that the steam will rise and the ethanol vapors will sink, until their concentration falls below about 41% by volume in the top of the column.
This is a handy feature if you are making ethanol from scratch, as you can strip the wash with the valve wide open, and the product will drop off as the critical temperature for tails is reached, making the separation easy.
Usually the first constituent to reach the head of the still will be the Ethyl Acetate, and Methanol, which are bled off and discarded, followed by their azeotropes with ethanol, called the heads.
After the heads, comes the purified ethanol, until it reaches about 41%, at which time the tails arrive, with fusil oils and other cogens.
The advantage of this type of vapor control, is that the temperature and flow of the incoming water to the condensers isn't as critical, and it is self regulating on shut off. The temperature will not only rise, but product through the Liebig condenser will dwindle.
Path B, provides even finer separation of the constituents, but does rely on regulating both the flow and temperature of the water to the Alhin refluxing condenser, because we will be using it as the control point.
The way we operate it, is to run it in full reflux mode until it reaches equilibrium, and then start cutting back the flow to the Alhin condenser. That will let the very lowest boiling point constituents to flow up and out the top of the Alhin, where it is directed through a Liebig product condenser and cooled into a liquid.
The advantage is very fine control, but it has to be monitored more closely and cooling water pressure, temperature, and flow are more critical.
You can also achieve the same effect by leaving the flow through the Alhin reflux condenser constant, and cranking up the boiler heat. Less system losses, the amount of heat added by the boiler, has to be removed by the reflux condenser to stay in balance. Increasing the heat will drive the vapors out the top of a finely balanced heat exchanger, just like reducing the cooling capacity.
For those applications where a simple pot still is just the ticket, with the Enabler's modular design, the head cross can easily be attached directly to the boiler itself, eliminating the column altogether. Hee, hee, hee, what could be sweeter?
An age is called Dark not because the light fails to shine, but because people refuse to see it.
Believing is seeing and ignorance is bliss until it bites you in the ass!
Alas, my ignorance abounds; the more I've learned, the less I know that I know..........
Thou shalt seek and respect the opinions of operators, even unto the third helper, for theirs is a wisdom unknown to technicrats.
Wise men learn more from fools, than fools from wise men.