Traditional pot stills require high temperatures meaning that the distillate will include a certain percentage of water, making the alcohol content lower and the distillate safe for consumption. This is the commonly used process in Europe and other parts of the world to obtain Cognacs, Whiskeys, Armagnac and other spirits. This process commonly known as a simple distillation process is what gives the flavour associated with drinking alcohol.
With pot stills when a higher purity of alcohol is desired, a second or third distillation is needed. However at the end of the 19th century the reflux column still was introduced. The reflux still made it possible to process multiple distillations in one single go and obtain a purer product. At the time it revolutionised the production of many valuable petroleum and chemical products that we commonly use today.
As some of the less volatile components also vaporize, distillation is not capable of separating substances of very similar boiling points to obtain a higher level of purity. To obtain this purity one would need to do many single distillations, collect the vapour that comes off, condense it, clean out the still, and run it through again. This is why pot distillers run double & triple distillations to get into the 80+ % range. But a Reflux column employs a fractional distilling process and allows this to happen continuously. Reflux reintroduces some of the condensate into the column in order to further purify the distillate stream. Purity is improved during distillation by allowing the rising vapour to mingle with the wash at a slightly cooler temperature.
Our Al-Ambiq® reflux column still is made up of a soldered union construction copper pot and a tall column (the reflux column) which includes a condenser. A brass stopper is located on the top of the reflux column. By removing the stopper you may place a rubber bung and thermometer (included) to control the precise cutting points between the heads, hearts and tails. The water system in addition to being used for the condensing pipe also comes in contact with the reflux column.
The vapours from the pot (boiler) start to gather in the initial vapour chamber. They then start to travel up the reflux column. When these vapours come in contact with the cold surface created by the water inlet located at the bottom of the column, the heavy less volatile vapours condense and fall back into the pot. This is known as a pre-refining process. As the vapours continue to travel up the reflux column these continue to condense (due to the cooler temperatures of the column) and the liquid cascades back down into the boiler and mixes with the rising vapours. This reflux liquid helps clean the rising vapours and increase the % purity. The larger reflux column stills will have two pre-refining processes, one at the bottom of the reflux column with the water inlet and one at the top of the column where the water outlet is located, as here too the water comes in contact with the column and creates additional condensing of the rising vapours.
Professional continuous distillation columns have a number of plates introduced in the reflux column to further increase the purity. These are literally large metal plates or trays over which the liquid flows, and the alcoholic vapours bubble up through holes in them. Because some of the less volatile components will also vaporize, these series of plates, which have lower and lower temperatures as you reach the top of the column will condense the less volatile components back to liquid. The number of plates helps to determine the purity of the distillate. The more plates there are in a column, the greater the purity of the distillate. A greater number of plates require more energy. As these plates are quite difficult to design and build and not really suited for small column diameters (less than 30,48cm or1 ft diameter) it is easier to use a Packed Column; where the packing (not included) can be random (e.g. just dumped in there and given a shake), or carefully positioned and stacked.
The height of packing needed in order to do the same job as an ideal plate is called the HETP - HETP - Height Equivalent to aTheoretical Plate. Smaller HETPs are better than large ones, as it means that for a given column height (say 1m) you end up with more ideal plates, e.g. only 2 plates (87% purity) if the HETP= 0.5m, but 4 plates (92% purity) if HETP = 0.25 m. If you don't have an exact number of plates, that is still OK; you'll end up somewhere proportionally between the two.
To calculate the HETP for your still please go to:
http://www.homedistiller.org/refluxdesign.htm#help. This chart will help you calculate the estimated Vapour purity.
For a hobbyist it is far easier to use common pot scourers (non-rusting stainless steel or copper) instead of packing, as you will be cleaning them frequently (like after every 20L run). Alternatively you may use marbles, stainless steel screws, ceramic raschig rings or copper wool.
Simply remove the copper cap at the top of the reflux column (which is not soldered) fill this with the desired packing material, depending on the diameter of the column (smaller objects pack together better but be careful, you do not want to block the column off – you need to allow room for the vapour and liquid to flow around the packed items). The packed items will be hotter at the bottom then at the top. As the vapours come in contact with the cooler packed material, the less volatile compounds which have a lower boiling point will condense and fall back. When this liquid suspended in the packing re-evaporates then the resulting vapour is richer in the more volatile components. The packing is there simply to hold intermediate distillate in place so it can be bathed in hot, rising vapour and more volatiles are further extracted from the intermediate distillate. Finally when these vapours pass through the packing and come in contact with the top cooling tube (25L up), the vapours are once again stripped more thoroughly and a purer alcohol is obtained – up to 90%.
The taller the column the more reflux liquid, the purer the product will be as there is more place for the liquid and vapour to mingle. You will obtain a very clean distillate with little flavour to it – ideal for mixing flavours.
Useful information: The buyer has two options with this system. The reflux column still may be purchased with separate swan neck tubing and a condensing coil recipient transforming it also into an alembic pot still. You may distill a batch of any type of fruit or other organic material with the reflux column to obtain a with very high % purity alcohol with very little flavour. Consequently, should you wish to add flavouring to your already high % purity alcohol, simply process another distillation in the normal alembic pot and add whatever flavouring you wish – such as oak wood chips.
Basic information on different distilling processes is included in this site and a list of precautions that should be taken into consideration for any model.
The separate parts that make up a still have been designed and manufactured to fit together perfectly and seal off all vapours (thus the concave shape of the swan neck head). After years of usage some natural slack may occur between these parts and will need to be sealed off to prevent the escape of vapours.This is achieved with a very simple and rudimentary sealing technique.
These products are made with thicker copper sheetings and therefore we are only able to manufacture them with our Premium line.