Charge in the kettle - Highest Proof

[mikeg]

Hey everyone,

I'm curious what is the highest proof people have put into their stills. I know we have to be careful over 100 proof but have people done (or regularly do) in practice? I imagine that there is a big danger difference between direct fire and steam jacketed so I should say I'm really interested in steam jacketed.

The purpose here is to take leftover feints from previous runs and try to clean them up back to neutral, or as close to neutral as possible. My thoughts here are to load up the still with as high proof as possible, run the deflegmator, and run it super slow so it sticks as high as possible. My still is steam jacketed and has 4 plates. I can keep my feints around 170 proof so if I ran that I might get 185+ proof out, and it'll taste about as clean as it can get. So, the question is, is 170 proof too high to throw into the still?

Any thoughts?

Thanks for any and all insight!

[Roger]

Please tell everyone in your surrounding community to leave the area while you experiment.

[mikeg]

Please tell everyone in your surrounding community to leave the area while you experiment.

I realized after I posted most people would not answer this question due to the apparent risk. I guess I asked for this.

How about if I rephrase the question, taking it out of practice and application but more of a theoretical question:

Ethanol-water solutions above 50% are flammable and can cause an explosion if there is an ignition source and sufficient oxygen. Neither of these exist in a properly designed still. So, I'm at a loss as to how an explosion could occur.

Thinking about this a little more, if we are afraid to distill a charge with more than 50% ethanol then we are saying there is a lot of risk in the solution itself, after all the vapor above the charge, during a heads phase especially, can be at 180 proof. So, it seems that we're afraid of the solution exploding. But the only way that could happen is if there was oxygen in the solution & a sufficient heat source. I believe with a direct fire still one could heat up the copper to very high temps that could be considered an ignition source but with low pressure steam we cap out at 250 F. The auto-ignition temp of pure ethanol is at 350 C, which is 662 F. We're no where near that.

The solution has little dissolved oxygen, not nearly enough fuel to allow an explosion. A common experience, I'm sure we've all had is putting out the flame on a shot glass (statue of liberty anyone?). A flame in a glass of ethanol can't sustain itself without an open top.

So, I fully accept that I could be missing something. So, if anywhere here can highlight something I'm missing, that would be great!

Cheers

[Silk City Distillers]

I realized after I posted most people would not answer this question due to the apparent risk. I guess I asked for this.

How about if I rephrase the question, taking it out of practice and application but more of a theoretical question:

Ethanol-water solutions above 50% are flammable and can cause an explosion if there is an ignition source and sufficient oxygen. Neither of these exist in a properly designed still. So, I'm at a loss as to how an explosion could occur.

Actually, Ethanol/Water concentrations of 20% are flammable at these temperatures. The fire point of 20% ethanol/water is 136F. Lower yet they will still easily flash and sustained burn given the right temperatures (wine in a searing hot pan). However, your argument is a valid one. Regardless of the wash alcohol concentration, the gases in the head space and column of a still don't typically represent any kind of stoichiometric mixture. To use an engine analogy, it's too rich to burn, too much fuel.

The lower explosive limit (LEL) of ethanol is 3.3% and the upper explosive limit (UEL) is 19%. It's pretty much a given that ethanol vapor in a still would be above the lower explosive limit in nearly every case and very likely above the upper explosive limit, in nearly every case (catastrophic failure aside). This would even apply to a pot still filled with a wash, not even a spirit run.

Frankly, I'd look at it from an entirely different position. What would happen in this situation if the still boiler were to fail, and the still was to dump the entirety of it's contents? A weld, a ferrule, a seam, flange, clamp, rivet, valve, etc, etc. In a situation where you were loaded with a wash or beer, it would probably be ugly, but in the case where you were loaded with high proof, it would probably be a disaster. There are so many ways this can fail. Imagine looping a hose around a triclamp valve and accidentally tugging at it, perfectly real scenario. Are you going to charge a still drain spraying out hot alcohol to try to shut it off?

High temp high concentration ethanol spilled will immediately create a vapor cloud, and chances are, it's going to be between the LEL/UEL. The higher the temperature, the lower the flash points, flame points, and the higher the speed of vaporization (given a fixed concentration). I cringe when I hear about guys doing spirit runs on a direct fire still. If the boiler were to fail, the operator and nearly everyone in the general vicinity would die.

All that said, I wouldn't bother, by loading the boiler at such high proof you are gaining, at best, the equivalent of one additional plate. Going from 4 to 5 plates to try to squeeze a neutral out of your feints isn't going to make any real difference. In fact, you could get exactly the same output running your still will a lower ABV boiler charge, slower take off rate, with a higher reflux ratio (higher dephlegmator flow rate or lower dephlegmator temperature overall). There is nothing that 5 plates can do that 4 plates run at a higher reflux ratio can't do (No, really, the operating conditions have a large overlap).

You should easily be able to hit 185 on a 4 plate with a 40% boiler charge. But it won't be anywhere near neutral or clean.

[Silk City Distillers]

One more comment, someone passed this nugget of info on to me, so I'll share it here.

Feints from a pot still are a different animal than feints from a plated or packed column still. Due to the nature of the tighter fractionation with plates or packing, the concentration of congeners is higher. So while recycling feints from a pot still might have merit, due to the inefficiency of a pot still, recycling feints from a plated or packed still may not. In most cases, if you were to try it, you'd find that it will probably require a specialized still, that can provide even higher levels of separation than your spirit still, and I'd wager a bet that you'll need to take off at azeo to get something usable.

[bluestar]

If you are trying to clean it up, rather than just increase proof, you want to go in at lower proof and make good cuts.

[mikeg]

One more comment, someone passed this nugget of info on to me, so I'll share it here.

Feints from a pot still are a different animal than feints from a plated or packed column still. Due to the nature of the tighter fractionation with plates or packing, the concentration of congeners is higher. So while recycling feints from a pot still might have merit, due to the inefficiency of a pot still, recycling feints from a plated or packed still may not. In most cases, if you were to try it, you'd find that it will probably require a specialized still, that can provide even higher levels of separation than your spirit still, and I'd wager a bet that you'll need to take off at azeo to get something usable

You have a great argument for doing a water add! You also made me happy that I have both a 4" valve and a 2" valve on the discharge pot on my still that both lock. Both would have to open for a catastrophic spill to occur.

[mikeg]

If you are trying to clean it up, rather than just increase proof, you want to go in at lower proof and make good cuts.

My reasoning for not doing a water add was that I wanted to get as high of proof out of the still as possible because I wanted to be (hopefully) above the transition temp for the volatiles I picked up in the heads of previous runs. If I ran the still with a heavy water add, I would make cuts through the same range of proofs that I normally do, which means I would pull through the volatiles that I did on the last runs.

But maybe you and jamesbedner are right that I should do a water add and run super slow with a ton of reflux and taste what I get.

[mikeg]

One more comment, someone passed this nugget of info on to me, so I'll share it here.

Feints from a pot still are a different animal than feints from a plated or packed column still. Due to the nature of the tighter fractionation with plates or packing, the concentration of congeners is higher. So while recycling feints from a pot still might have merit, due to the inefficiency of a pot still, recycling feints from a plated or packed still may not. In most cases, if you were to try it, you'd find that it will probably require a specialized still, that can provide even higher levels of separation than your spirit still, and I'd wager a bet that you'll need to take off at azeo to get something usable.

One side note:

While thinking about this I found a paper from NIST that stated the solubility of oxygen at different temperatures and in different ethanol-water solution concentrations. While the dissolved O2 is always too low to be considered sufficient fuel for an explosion, the interesting thing is that the solubility, for high ethanol concentrations, goes up with temperature and not down. I was totally surprised. My guess is that it has to do with the oxygen getting better access/bonding to the carbon chains.