Full Boiling Chamber vs. Not

[aquavita]

Headspace - the kind in your still (dirty minds )

Completed filling my 13 gallon still with 11 or so gallons ready for a run.

Kind of reminded me of how fuel tanks in aircraft are less likely to "blow" when full vs. less than 1/2 full. Less volume of O2 and fuel vapor to ignite.

Any thoughts?

Aqua

[Bigbob]

I fill mine 3/4 or less. Had a puke once and don't want to repeat that.

[aquavita]

Understand the puke.

Put a sight glass 1/2 way up my column - can stop the puke before it's too late.

[shadylane]

I'm not sure, but there's probably isn't enough O2 in the pot for an explosion.
I'm thinking there's enough carbon dioxide left in the mash to displace the oxygen.

[3d0g]

CO2 doesn't displace oxygen, otherwise we'd all be dead down here on the ground in a blanket of our own waste. Alcohol vapor will push out all other gasses once things get going so the still charge size doesn't really matter. The biggest explosion risk is during cooldown when air is getting drawn back into the still, as seen in the Hudson distillery explosion. A CIP ball broke off and sparked in the column right as a stoichiometric mix was achieved. Horribly bad luck / timing.

[Usge]

I don't think they believe the Hudson Valley (Tuthilltown) distillery explosion was caused by an explosion inside the column. It was caused (they believe) by a ruptured holding tank that leaked distillate that was ignited by the heat source. At least...according to this article.

http://www.newpaltzx.com/2012/09/27/tut ... lery-fire/" onclick="window.open(this.href);return false;" rel="nofollow

[DAD300]

Commercial airliners now require Nitrogen purge system to displace the air in the tank.

[3d0g]

I was fortunate to have one of the actual investigators of the Hudson incident in my distilling training class last year. It was a CIP ball. I saw the pictures.

[cranky]

Not many people in the aerospace industry believe the reasons behind requiring the nitrogen generation in the fuel tanks is valid or necessary, but that's a discussion for another place. Now as far as potential still explosions as a result of the flammable vapor inside the still you need 3 things to get an explosion, combustible vapor, Air and ignition and all 3 have to be the right amount. The only thing the Mythbusters distilling episode got right was actually something they didn't intend to show and that was that when a still like we run "explodes" it is more of a woosh than an explosion because in the interest of safety, we keep our boiler charge below the flammable level so in the event of ignition whats in the boiler does not ignite, the vapor goes woosh and we douse anything on the outside with water. Now there was a guy a while back in Oklahoma who blew his garage doors off but that was the result of a leak that filled the garage to the point it ignited. My guess is he wasn't staying with his still when that happened or he would have smelled it. Our scale is really too small for a gallon or two of head space to make much of a difference should something happen.

[Danespirit]

Cranky..you hit the nail right on top.
Explosions in a still, will only happen if you're distilling with a too high ABV and would have a leak where vapours can reach a open flame.
Just the other day a member asked why to dillute below 40% ABV.
Alcohol can only be ignited when around 50% vol(ABV). For this to happen it also needs a source of ignition and a oxygen containing environment.
Take one factor away..and it will not burn.
I think the explosions we read of and what many people bring up as the first argument for forbidding homedistilation, is caused by careless people with not enough understanding. When someone boils a pot of let say 70% vol and have a leak in the still, it would be most likely he would smell those vapours. But leaving the still unattended and comming back with a cigarette hanging in the mouth, could be enough for that explosion to happen. A leak with a charge containing only 40% ABV, wouldn't be that dramatic.
Remember alcohol vapours are heavy, like gasoline vapours they will sink to the bottom and only when whirled up and mixed with air they can create a burnable mixture.
Unfortunatly there will always be idiots that creates fires or explosions, who put a bad light on home distilling..giveing people a negative impression of this wonderfull hobby.

[dstaines]

Danespirit I'm pretty sure that's not correct. I agree that stepping away from the still at any point is asking for trouble, as is smoking around your equipment obviously. But a liquid mixture of alcohol and water won't be able to sustain a flame below about a 50:50 ratio *at room temperature*. It's possible to flame a pan on the stove when deglazing with just wine. That's because it's never the liquid mixture that's burning, it's the mixture of vaporized alcohol and oxygen in the air, and heating the liquid mixture increases the amount of vaporized alcohol in contact with oxygen. And since we are always running our stills at above room temperature, ANY leak poses a risk of catastrophic fire, no matter how much you dilute the still charge.

[pfshine]

People keep saying smoking while neglecting the obvious ignition source. We put a container full of flammables on a propane burner and literaly shoot fire at it. Or jam a metal rod attached to 240v into it. I don't think smoking is at the top of the risk list.

[Brutal]

This prompted me to read the wikipedia page on ethanol again. Lots of good reading if you have a few minutes, check it out.

Here's a quote from there on ethanol flammability.
"Flammability

An ethanol-water solution that contains 40% ABV (alcohol by volume) will catch fire if heated to about 26 °C (79 °F) and if an ignition source is applied to it. This is called its flash point.[82] The flash point of pure ethanol is 16.60 °C (61.88 °F), less than average room temperature.

The flash points of ethanol concentrations from 10% ABV to 96% ABV are shown below:[83]

10% — 49 °C (120 °F)
20% — 36 °C (97 °F)
30% — 29 °C (84 °F)
40% — 26 °C (79 °F)
50% — 24 °C (75 °F)
60% — 22 °C (72 °F)
70% — 21 °C (70 °F)
80% — 20 °C (68 °F)
90% — 17 °C (63 °F)
96% — 17 °C (63 °F)

Alcoholic beverages that have a low concentration of ethanol will burn if sufficiently heated and an ignition source (such as an electric spark or a match) is applied to them. For example, the flash point of ordinary wine containing 12.5% ethanol is about 52 °C (126 °F).[84]"

Reading it you can see where the old estimate of product being 100 proof to burn came from. And how "approximate" it is/was.

[Danespirit]

Danespirit I'm pretty sure that's not correct. I agree that stepping away from the still at any point is asking for trouble, as is smoking around your equipment obviously. But a liquid mixture of alcohol and water won't be able to sustain a flame below about a 50:50 ratio *at room temperature*. It's possible to flame a pan on the stove when deglazing with just wine. That's because it's never the liquid mixture that's burning, it's the mixture of vaporized alcohol and oxygen in the air, and heating the liquid mixture increases the amount of vaporized alcohol in contact with oxygen. And since we are always running our stills at above room temperature, ANY leak poses a risk of catastrophic fire, no matter how much you dilute the still charge.

That was exactly what i was saying and part of my explainaition....so no argue on that..

Alcohol can only be ignited when around 50% vol(ABV). For this to happen it also needs a source of ignition and a oxygen containing environment.

But a liquid mixture of alcohol and water won't be able to sustain a flame below about a 50:50 ratio *at room temperature*

Temperature plays a role no doubt about that. And two terms : Flash point and ignition temperature.
Flashpoint is: " The lowest temperature where a violatile material would vapourize and can create a ignatable mixture".
Ignition temperature is: " The temperature any given substance should have at a minimum, before getting on fire without exposure to any igniton source"

Pfshine...i would also see smoking as a minor factor in this, a open flame would be worse of course.

[cranky]

Like I said, the volatile mixture is the vaporized alcohol mixed with air and it goes WOOSH and goes out, The guy that I mentioned who blew his house up did so with a flash fire that quickly extinguished itself. The distillery explosion a while back in Oklahoma city was also a flash fire, not an explosion, it went WOOSH. When I was young and my dad got burnt by a flash fire from a gas leak it was also a flash fire and not an explosion. Now as a boiler heats up the vapor being released from the wash quickly displaces the oxygen in spite of it being open to the atmosphere and as 3dog mentioned the risk is if you have to shut down in the middle of a run when the O2 gets sucked back into the boiler there are a few seconds when the mixture is right for ignition and on our scale there isn't enough back pressure to actually explode. Our final product is much more volatile than whats going on inside the still, however I would like to say that I don't like open flames, but that's just me and that's why I chose to go electric. I would also like to mention that I have a hot plate that if you touch something on top of it while it is on it will shock the piss out of you. This is something I would never use on a still because of potential arching, this is also why my boilers are grounded as close to the elements as possible. Regardless of how low or high the chances are I don't like taking chances.

[Hound Dog]

Pfshine pointed out the obvious ignition source of the propane burner. Cranky, you claim to have gone to electric because it is safer. It can go both ways. I went to electric now for the convenience factor, not for safety. Since ethanol vapor is heavier than air it will fall and collect along the floor. If you are running propane it will light up right away and flash off. With electric it can keep collecting until you have quite the mass amount of air fuel mixture to ignite. Like the example of the garage doors blowing out. On the other hand, I had the head come off a pot still during a stripping run over propane once. In that case, electric would have been safer because it was sudden and I could have easily shut things down. It was a little harry over propane with the fireball and all but I was prepared with a water hose and remote gas bottle (my 100# tank sits outside the garage door with a long hose for safety and so you can get to it to shut it down in a fire) and it was a non issue. So really it just depends on the situation.

Back on topic, yea, I don't think the little bit of head space inside the boiler matters one way or another.

[cranky]

Pfshine pointed out the obvious ignition source of the propane burner. Cranky, you claim to have gone to electric because it is safer. It can go both ways. I went to electric now for the convenience factor, not for safety. Since ethanol vapor is heavier than air it will fall and collect along the floor. If you are running propane it will light up right away and flash off. With electric it can keep collecting until you have quite the mass amount of air fuel mixture to ignite. Like the example of the garage doors blowing out. On the other hand, I had the head come off a pot still during a stripping run over propane once. In that case, electric would have been safer because it was sudden and I could have easily shut things down. It was a little harry over propane with the fireball and all but I was prepared with a water hose and remote gas bottle (my 100# tank sits outside the garage door with a long hose for safety and so you can get to it to shut it down in a fire) and it was a non issue. So really it just depends on the situation.

Back on topic, yea, I don't think the little bit of head space inside the boiler matters one way or another.

Not to really argue with you Hound Dog but if vapor accumulation at floor level builds up to the point of flashing it's because you aren't in the room and shouldn't be stilling. If you are there you will smell it long before it gets to that point, so yes electric is safer. That instance you mention where the head blew off is very similar to what happened in OKC and there is a picture of the distiller covered in hot distillate next to a geyser of steam taken a fraction of a second before it flashed. The resulting severe burns could have happened to you or anybody else running gas when the lid blew. Could a stray spark from electric set it off? Maybe but in the case of open propane flame it is an absolute certainty.

[Danespirit]

Yes Cranky a spark is all it takes.
Given the facts that the vapor/air mix is at a favorable level, a tiny spark can ignite the mixture.
If the vapor also is heated up, it further promotes the explosion.
As a little sidenote: When i was younger, me and my buddy build a potatocannon that used alcohol as a propellant.
All it took was a small fan to stirr up the mixture and a piezoelectric element from a old lighter...BOOM.
So yes...alcohol can cause a explosive combustion to happen, so can gasoline.
The point is that it is a combustion NOT a real explosion. The combustion just happens rappid.
Same is happening in a gasoline engine, it's not a "explosion engine" it's a combustion engine.