Originally By Tony Ackland
Designing Your Own StillSo how do you put all this together to make your own still ? Say you're looking at wanting to make 90%+ purity, off a 20L wash.
PotTo hold 20L you want at least another 1/4 spare for foam, etc. So go for something in the 25-30L range. I'd suggest something where you can easily lock the lid down, but also be able to get into it fully to clean it out. Suggestions include paint tins as seen in walt or AV25L or a preserving pan with a clipped lid like Teds at http://mwci.s5.com/.
These all have pretty thin lids, so to support the column, you may need a small flange to help hold it all up, or a stiffening plate/oversized washer to help strengthen the lid.
Heating ElementProbably in the 1000-1500 W size. Whats cost-effective for you ? A 1500W element will heat up the contents to begin in around 65 minutes, but a 1000W will take 98 minutes. If time is crucial, you could add a second element to act as a boost during the initial heat up.
Column SizingThe diameter is based on the amount of heat you're using, whereas its length determines what purity you'll get. Its a hobby still, so I've assumed that the packing will be stainless steel or copper scourers - they only take about 1/2 the height that marbles do to get the same purity. You will also need to insulate the whole length of column too - plumbing suppliers sell slip-on piping insulation for around NZ$8/m
Diameter : 1 inch is too narrow for a 1380W element, but 1.5 inch is OK with a 1800W element. Roughly, lets say to use 1.5 inch for 1000W - 1500W and 1.75 - 2 inch for 1500W - 2000W. If in doubt, go up in size by say 0.25 inch. Too narrow will lead to all manner of problems & difficult operation, but too wide will only give a minimal reduction in purity. 2" is a well used, very reliable diameter that works under most circumstances.
Height : This is the purity. Use the wee interactive applet at the start of this page to see how the number of stages or HETP's improves the purity. Its easy to get the first gains up to 90%, but then more difficult to squeeze out the last improvements towards 95%+ Lets assume (we'll come back to this) that each HETP for scrubbing pads is around 15cm... then for a 15% wash, No packing, purity = 62% , 15cm packing = 82%, 30cm = 88%, 45cm = 90%, 60cm = 92%, 75cm = 92.8%, 90cm = 93.4%, 105cm = 93.9%. These won't be exact, and depend on a number of different factors, but it shouldn't be too far off. So, if height is a problem, and you're happy with low 90's, then 60cm should do ya. If you want to make a perfect vodka, go for 120 to 150cm. Normally I'd recommend at least 100cm, but the choice is yours, as it depends on the type of product you want to make.
These numbers assume that we've reached equilbrium nicely for each 15cm of packing. To do so, we need to provide heaps of surface area for the liquid and vapour to mingle over (done - using scrubbers), and that we're refluxing a large proportion of the vapour back down as liquid, rather than keeping it. But this means that our take-off will be rather slow. Eg we may be able to start out with a reflux ratio of say 3-4 (ie return 30-40mL for every 10 mL we keep) when the pot is very rich in alcohol, but later on, when its getting down in alcohol, we may need to increase this up to 5-10 to keep the high purity.
A reflux ratio of 4, with a 1500W element means that we're collecting at around 20 mL/min. Thus a 20L 15% wash will take a minimum of 2.5 hours to collect (20 mL/min), up to 5 hours at a reflux ratio of 8 (10 mL/min). The actual time will be somewhere between these, depending on what ratio you end up needing in order to deliver the purity you're after.
If the distilling time is taking too long, we can make the column taller, and then run at a slightly smaller reflux ratio, to get the same purity.
The collection rate is directly proportional to the element size, so if a 1500W element with reflux ratio of 4 takes 3 hours to distill, then 1000W will take 4.5 hours, or a 2000W 2.25 hours.
Making the RefluxTheres a couple of different options for how to provide the refluxing liquid. The choices come down to how much control you want over it.
The first, simplest and cheapest, is just to have a cooling coil in the head of the column, which is fed cooling water direct from the condensor. Provided you have sufficient coil surface area available (eg > 1-2 m), you should be able to increase and control the reflux ratio to give you the high purity. If you only have a couple of coils inside the column (like I've drawn), then you wan't be able to make enough reflux, and you're in for mediocre results.
Second - plumb the cooling coil with its own water supply - say a T joint off the main line, with a couple of valves to be able to regulate the water to the coil seperately from the main condensor. This would allow you to say turn off the coil if you want to do a stripping run, without affecting the performance of the main condensor.
For excellent instruction on fitting a coil, see Homers diagram or a couple of Phils photos.
If the main column is too narrow to have a coiling coil inside it, you can always use a cold collar around the outside of it. Another, but less effective method is to coil around the outside of the column.
There are excellent instructions for making the external condensor in the "StillMaker" or at Http://www.Moonshine-Still.com Basically just use a couple of T fittings, or if you're a dab hand at welding, just build it up yourself. Another (easier) option is the "Euro" still condensor, where the cooling water is simply fed in a tube up through the outlet pipe. See a photo of it.
Third (my preferred option) is to do the Nixon style of condensor, as seen in the photos, where all the vapour is condensed (with an oversized coil - thus minimal water required), and then you proportion off the amount of liquid you keep vs return. This gives you maximum control over the reflux ratio, being able to dial it up from "total reflux", essential for getting a column into equilbrium before taking off the heads, through to "no reflux" if you want to do a stripping run, or only a low reflux run say for a flavourful rum or the like. The disadvantage of this design is that it adds to the height - say another 30 cm. But I reckon well worth it.
An excellent variation on that is Alex's (Bokakob) mini-still:
ControlsI prefer to only control the reflux ratio. If the column is wide enough, then you don't need to worry about metering the heat input via the element. Either up the water flowrate, or close down the take-off valve, in response to the vapour temperature measured at the top of the column. Use this graph below to compare temperature to purity. Cheap (NZ$28 at www.dse.co.nz ) digital thermometers are excellent for reading this temperature.
SummarySo, in summary, to make a very cheap, short still, how about a 1500W element, with a 1.5 inch by 60-70cm column, scrubber packing, and simple external condensor (Euro style) & internal cooling coil of say 4-5 turns, directly plumbed between the two.
To make a more high performance still with more options on how to run it & what products you can make from it, first make it taller, and then consider using the Nixon condensor.