A word of caution is necessary before you make the first trial run. Distillation may involve the use of high heat, electrical connections, open flames, boiling liquids, and perhaps explosive gas mixtures. All of these can cause serious personal injury, fires or even explosions if you do not take precautions and give a lot of thought to these things.
If, even after these warnings, you decide proceed with the distillation of highly flammable substances such as alcohol, remember that it is akin to boiling a pot of gasoline on top of your gas stove at home.
The test of the apparatus should be a trial run in which a gallon or two of water is distilled. The test will verify that the joints don't leak that there is sufficient heat input to do the job, and enough cooling control to control the distillation. It will also allow you to check the distillation rates and the warm up time.
To start the run, mount the boiler on top of the heat source, and fill it with a gallon of tap water. Then connect the cooling hoses on the column to the water supply and drain, and attach the column to the boiler. Do not allow the cooling water to circulate through the apparatus at this time.
Turn on the heat to its' highest setting and insert the thermometer in the top of the column. The bulb should be seated to the level of the upper column tee connection (where the vapors flow to the condenser).
In a short time (about 15 minutes) the water should be boiling to the point where vapor and liquid can be seen exiting the condenser, and the thermometer indicates that the boiling point temperature (100° C..) has been reached in the column. Note how long it took to boil so you can estimate the time for larger amounts.
Turn the heat down to a rolling boil, and slowly open the cooling water circulation valve just enough to stop any vapor from exiting the condenser. The distillate that runs from the condenser should be warm to the touch. This represents the maximum effective rate that the still can deliver under these circumstances.
At that point measure the time needed to collect exactly 250 ml of distillate. This should take about 7 or 8 minutes.
When that's done, slowly open the circulation valve until the distillate stops running altogether. Let the system continue in that state (no output) for about 15 minutes to verify its ability to operate under total reflux conditions.
When you've verified this point, it's time to shut the system down. You should always follow a sequence in these operations in order to avoid imploding the boiler and column. The shutdown sequence is:
© First remove the thermometer cap from the top of the column (use gloves, it may be hot, and avoid burning yourself with the vapors coming out).
© Finally shut off the cooling water circulation.
This is important, because if you are using plastic tubing to collect the distillate from the condenser, it could get kinked or obstructed in some way. That would seal off the apparatus from the air. If this happened while it was cooling down, a vacuum would be formed within the still as the vapors inside condense, and the air pressure outside could crush the unit.
When the unit has reached room temperature, disconnect the cooling hoses, back-flush the column with water then remove the top end from the boiler for cleaning.
Now that we know how to run the still, it might be a good idea to give some more thought of how to optimize the distillation.
Whenever you try to maximize the purity of the distillate in the least amount of time, you have to deal with the amount of refluxing needed.
In operation, we allow only a small part of the distillate output to be withdrawn in a unit of time. The remainder is re-cycled back into the column. This controls the amount of refluxing. The proportion of distillate returned to the column versus that which is withdrawn is called the Reflux Ratio.
In theory, the more reflux cycles that are allowed to take place the purer the output will be. In other words, high reflux ratios produce more refined products.
In practice though, you will find that as you increase the reflux ratio more and more, it produces less and less improvement in the purity of the output. You soon reach the point where the whole operation becomes counter productive in terms of the time and heating costs to produce the distillate.
It's also important to recognize that no matter how many reflux cycles are applied to the process, you will never be able to get a completely pure distillate.
Under the circumstances then, your goal in operating the still should be to produce a purer product than what you can buy commercially, and at the same time produce the product at the least cost.
All this then comes down to the big question:
"What is the best reflux ratio to use in my still, and how do I regulate it? ".
The system we are building controls the reflux ratio by regulating the cooling flow inside the column. We calculate the reflux ratio by measuring the maximum distillation rate at a given heat level without cooling, and then regulate the cooling to provide an appropriate fraction of that rate.
Suppose, for instance, you can distill 1 liter/hour at a given heat setting without any cooling, and you want a reflux ratio of 3 to 1. Then you simply adjust the cooling flow (without changing the heat) to the point where only 250 ml of output is distilled in one hour. That means for each 1000 ml of distillate passed in a unit of time, 250ml is withdrawn, and 750 ml is refluxed. That gives a reflux ratio of 3:1.
Coming back to the key question "What's the best reflux ratio to use?" It depends on the column design, what's being distilled, an assessment of the output purity, and an evaluation of the costs involved in producing that purity.
It will take some experimentation on your part to get exactly what you want.
If you want to distill ethyl alcohol for instance, your best bet would be to start with a reflux ratio of 3:1 with this still. Commercial operations, I've been told, use ratios ranging from 1.8:1 to 5:1 for distilling this product.
Under normal conditions then, and using this ratio, you should be able to produce a crystal clear, totally odorless, 190 proof spirit from a 20% beer in a about 6 hours of distillation.
In any event, you have complete control over the refluxing with this still, and the only limitation you will face is the desired degree of refinement.
That is much more than can be said for most small scale stills.
Well it's done. We've started at scratch, learned a The Last Words little along the way, maybe got involved enough to actually build the still, and maybe even went further.
For me, it's been a lot of fun, a great experience, and a continuing adventure. For those of you who have traveled the entire course, I hope you are pleased with the results. More than that, I hope you get involved enough to improve on this basic apparatus and let others know about it so that they too, may profit from your experiences.
Who knows, with enough interest from those of you reading this, perhaps some of the more insensible laws of the land can be changed. And if they can be changed simply because you get involved, then you will have made a great contribution by giving everyone a bit more freedom to pursue those interests that do no harm to their neighbors.
In any case, with the apparatus you have just constructed, you will be able to isolate, and perhaps enjoy, many of the refined compounds derived from your distillation apparatus. That, for many, is reward enough.
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