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kiwistillers VM Operation Tutorial.

PostPosted: Sun Jul 10, 2011 6:26 pm
by MacStill
Thank's to kiwistiller for sending me the following guide.

How to run a VM column.

Right, some long awaited VM operational instructions. Bear in mind that this is just how I run my VM. If you do it differently, give some feedback, and we'll edit your way into this post as well. This guide is assuming the goal is a neutral spirit. A VM 'can' be used for flavoured spirits, especially a light rum, but it's really an 'extra for experts', and by far the majority of flavoured spirits are easier to produce with a pot still IMHO. I'm going to assume you understand basic reflux design if you've built one of these, and have a basic understanding of cuts. You should be able to pick up that from the other posts in this section anyway.

Pre Run
Still Charge:
I would highly recommend running low wines in your VM - do a stripping run first with a pot still. Many of you have keg boilers, so a 40l charge at 40% will keep you busy for a long spirit run (start very early in the morning, or plan to do some both days of a weekend), but then you'll be left with roughly (I've never actually paid much attention to my VM yield after cuts aside from 'Lots' :oops:) 30l of fine neutral at 40%, enough to tide over any mortal for a good while. If that's not enough, seek help. :lol:

As always, never charge the boiler with higher than 40%ABV.

I'd also try to treat your low wines with sodium carbonate (preferable) or bicarbonate (baking soda, second choice), this will reduce the volume of heads you collect significantly. Low wines treatment is outside the scope of this guide, so do a search. Just roughly, 1 teaspoon carbonate per litre, and you can run straight away. 1 tablespoon of bicarb per litre, leave sit for at least 3-4 days before running.

Cooling Setup:
Run your coolant through the bottom of your product condenser, out the top, then into your coil. Don't run it too fast - the water should be exiting fairly warm (45-50 º C / 115-120 º ). Obviously, don't run the cooling too slow either, no one likes ethanol vapour billowing out the top of the still. The reason for not running the cooling flat out is that you may actually overcool the surroundings of the condenser, which will extend the effective condenser length down into your column. In extreme cases this will reduce your takeoff speed by condensing product in the takeoff chamber.

Insulate your column, at least up to the takeoff port. This is a must. No real need to insulate the condenser section, though you could do that takeoff arm if you like. One reason, efficiency aside, is you don't want that pretty copper catching a passing breeze and suddenly collapsing the equilibrium inside your still by conducting a lot of heat away and filling the column with reflux. There are others, but that's the simple one :)

Distillation run:

Heat up:
You can throw as much heat as you like at the boiler for the heatup stage. Just watch it, because you'll need to throttle it back once it heats up. Keep the takeoff valve completely shut for now.

Make sure your condenser and coolant system is working before you fire up the boiler.

Once the boiler charge hits boiling, it will fill the column with vapour very quickly, within seconds. You must have the coolant flowing before you get to that point, AND turn the heat to the boiler down before vapour floods the column.

Equalibriate at very low power for 1hr, minimum. This is running the still in 100% reflux (valve completely shut still) to allow the fractions to separate out in the column. The thermometer will probably be bouncing around a little at the start of this process, that's normal - just shows you that things aren't separated yet. I Believe snuffy was able to equalise his column with something tiny like 100-300W in a really well insulated system. I think it takes a little more than that for me, but I run gas, so hard to judge. You do need to keep the column refluxing though, so listen to your still - if you can still here the trickling, dripping noise of the reflux falling off your condenser, you're fine. That being said, Hookline informs me that he cannot hear the dripping through the insulation, so your mileage may vary with that trick. Your thermo will eventually stabilise a little below azeotrope temps (~76-78*C, or thereabouts, your thermometer will quite likely be out by .5* or so).

Foreshots / heads bleed:
Personally, I've stopped really distinguishing between these fractions in the normal fashion for a reflux run. The heads are so skanky that the vast majority of them aren't worth recycling to me, so I treat all but the very late heads as foreshots. Keeping the heat low initially, slightly crack your takeoff valve and bleed off your foreshots / heads at a very slow speed. I'd take the first maybe 500ml (of my 40l charge) at a couple of drops a second, before increasing the power a bit and shutting the valve again for 5 minutes to let the column re-equilibriate. I would then take the rest of heads off at the slightly higher power, aiming for maybe 500ml/hour. I plan on getting at minimum 10% of my total alcohol back as heads, but sometimes it can be more. This will of course depend on how fussy you are - some like a touch of heads in their neutral, Minime would be one off the top of my head.

Some folks bother trying to recycle feints (heads and tails) from neutral runs, Personally I don't bother. I throw the fores/heads from neutral runs into the methylated / denatured spirits bottle. Perfect use for them, they work great as a general purpose solvent.

Heads / hearts cut:
If you are tasting (remember, dilute to 35% or so for accurate tasting) for cuts, you'll notice the sweet chemical taste of Ethyl Acetate starting to fade from your product. You're almost at the cut point then. To avoid dragging out this last bit of heads into your hearts, I like to return the column to equilibrium for a couple of minutes, and then open the valve slightly more than you have for the previous heads and draw off that last little bit. when it's tasting clean, you're in your hearts.

This last bit of heads is the only part of feints I'll recycle from a neutral run.

You can of course collect in small bottles and find the exact cut point later, after airing.

This is where a bit of operator discretion comes into play - you have to decide just how pure you like your hearts.

Switch to your hearts containers (I still collect in a set of 750ml bottles, reduces the damage of a mistake in cuts, and you don't want to repeat runs that take this much time).

Power up a bit (you can calculate this if you get into it, according to 'Designing and Building Automatic Stills' you want vapour speed between 12-20" per second) and open the valve up for hearts. For a tall 2" column, 2000W is a good upper limit - not all of this will be realised at the condenser unless you have perfect insulation, which you won't. Of course, if you have a wider column, scale up the power accordingly for the increase.

I run mine wide open or almost wide open which gets me a reflux ratio of ~1:1, which is close enough to azeotrope with my tall column to make me happy. My 2" column has 1.5m of copper mesh packed height, with reflux centering halfway down. Run on roughly 2000w, a ratio of 1:1 yields bout 95.2% according to theparent site's reflux sizing calculations. Your mileage may vary, of course - I'm probably faster that a bog-standard VM due to the reflux centering.

If I want a really top shelf neutral, I'll run it with a higher reflux ratio, maybe 1.5:1 or as high as 2:1. Some folks are fussier than I and would run 2:1 or higher, but I'd say that a ratio of 2:1 will please 95% of the people out there, and a good lot would settle for less. With a 2:1 ratio, the centre of hearts (after dilution) has absolutely no taste whatsoever to my senses. Again, YMMV.

I try to aim for at least 1.5l/hr, hopefully 2 (running that fast requires close attention though). If you want to run at a higher ratio, then of course you'll be collecting slower than this.

Hookline advises that he can taste the difference between 1 and 1.5 l/h from his 2" VM, and also only hits 94-94.5%.

Hearts / Tails Cut:
Watch the temp. You should have a digital thermometer with a 0.1*C resolution. It may rise and fall 0.1*C briefly over the course of the hearts, but when it rises 0.1 or 0.2 and stays there, it's time to pay attention. Shut the valve a bit to bring it back down. Keep the heat at the hearts level - you want to keep the vapour production and therefore reflux ratio up, so we control this with the valve, not the power. When temp rises again, shut a bit more. You're compressing tails now. It's really up to you how many times you reduce speed and keep going, but obviously you're getting less and less each time, and slower. I normally do it a couple of times and then let the last bit go to waste. I hate getting tails in my product condenser, gross and annoying to clean out, and after a long run I'm not normally concerned about that last litre.

Running a VM really is about a good thermo. Being able to read 0.1 ºC changes is what lets you make good neutral fairly easily.

Like I said, I don't normally bother collecting tails, they're so gross I won't recycle much of them anyway, and there is so little of them and they are so concentrated at the end of a VM neutral run.

If you did want to collect them, strapping on a pot still head to the boiler would probably be the best way. Otherwise, power up, open the valve fully, and quit collecting when you think you're starting to waste your time. The VM is unable to collect below about 40% - after that, the vapour is lighter than air and won't fall down the product branch. Neat, eh?

Post Run:
Neutral will benefit greatly from being left to air for a day or so. Remember though - it's ~95%, and will be losing volume fast to evaporation, so keep an eye on it.

When diluting, if you are using a alcometer and not a calculator, remember that as you dilute, it will warm up and throw off your readings, so keep an eye on the temperature and correct for it.

I think it's important to critique yourself on your cuts. I collect in bottles, and put a gap in the line of them where I've predicted my cuts. I'll check this cut point after airing - is that last bottle of heads really hearts? Is the first bottle of hearts just a little bit too burny? Give yourself some feedback so you can improve your cut points.

The water you dilute with will have a big impact on taste or lack thereof.

And finally, never, NEVER serve undiluted neutral to your mates or loved ones, and NEVER leave it where they might stumble across it. If you have to keep it strong, label it as poison (you won't be lying) and keep it locked away. Otherwise, dilute after airing back to standard commercial strength - 40% or so. This shit will be really, really neutral. Someone could seriously harm themselves without knowing what they're doing to themselves. It's all fun and games until someone goes to the hospital. Stay safe guys.