Limiting step - pressure.

Watershed · Post by **Watershed** » Sun Jan 22, 2006 3:34 am

Well I 've found the limit for my pot still by gradualy increasing the heat on strippings runs. If I try to run a gallon ( 14% ) off in less than 1 hour the top lifts off with the pressure build up.

It set me wondering though - if I clamped the top to allow higher pressure ( not that I'd gain much from doing so with this set up ), what effect does increased pressure have on efficiency?

junkyard dawg · Post by **junkyard dawg** » Sun Jan 22, 2006 9:11 am

I think that lower pressure also lowers the boiling point of ethanol. Thats why there are vacuum stills. Vapor pressure? Is that the right term?

So, maybe the still would be operating less efficiently under higher pressure? but then the temperature would also go up...now I'm confused... going reading...

Post by **Tater** » Sun Jan 22, 2006 9:18 am

Gonna get more water in vaper .Whole point in distilling is to try to get most ethanol outta wash by keeping temp of wash to boiling point of ethanol.

Hillbilly Rebel · Post by **Hillbilly Rebel** » Sun Jan 22, 2006 9:19 am

I would be real carefull about clamping your pot still for the purpose of building up pressure. You may get more than you are asking for, it could explode. Old timers tell me that Naplam has nothing on exploding mash for a really bad burn. They also knew exactly how big a rock to put on top of their cap to give them the pressure they wanted but to still act as a pressure valve if they got to much pressure. Make sure you have a pressure guage and take it very slowly, IMHO.

Watershed · Post by **Watershed** » Sun Jan 22, 2006 10:08 am

I'd never deliberately build up pressure - I just wondered what effect it had on the vapour proportions.

possum · Post by **possum** » Sun Jan 22, 2006 10:23 am

I have foot locker clamps tacked into and soldered into my cap and body, but I have a T conection, with a cork on the T between my lyne arm and cap. This is my "fuse" or blow off cork. When you run your rig hot, you may not get the smal amount of reflux that occurs with some potstill designs.Basically, you may end up with more water in your stripping runs.
Just keep safty in mind.

Watershed · Post by **Watershed** » Sun Jan 22, 2006 2:16 pm

I always take the high proof runs real slow - don't want to think of the consequences of the lid lifting of with a naked flame underneath. At least I bought an extinguiser.

decoy · Post by **decoy** » Sun Jan 22, 2006 6:39 pm

one thing i have learnt in the past few months id that a still is a balanced pice of equipment..

you have to take into consideration the following:

wash %
then the size of your pot
how much heat you need to supply to pot
ammount of steam generated
Pot presure
Pot lid height "water vapour condenses on walls and runs back down lowering internal presure"
the height and diam of the reflux column
and then the condensor to strip of the energy.

the presure will raise the boiling point of water and alcohol etc..
the reflux column will start to output more water then ethanol as a final product and your condensor will need more watter to condense the ethanol.
and if the velocity of the vapor flowing through the condensor gets to high for the length of your condensor then you will find you will have stem coming out of your condensor and you will be venting ethanol vapor into the air, then if you are in an enclosed room with a flame it is posible to achive an explosion in your room.

I belive exploading stills "expecialy under conditions we are running" are a myth, could be one to send in to Myth Busters

alcohol vapor will only expload in the presence of oxygen, and if you want to be fully safty concious you would start a continuos still with water and steam then introduce your wash and purge pot stills with CO2 or argon before you started heating your wash.

you will find a mixture of alcohol and water vapor will not explode unless the encloased room was full of alcohol vapour and air then there is a posibilty of explosion.

worst case senario is burns from a alcohol fire or hot liquid or steam burns.

these are my views only.

there was a recent show by myth busters were they filld a toilet with Methane Gas and set fire to it and there was no explosion just the toilet paper and dummy caught on fire..

rectifier · Post by **rectifier** » Sun Jan 22, 2006 6:54 pm

Hey good idea decoy, I'd love to see the mythbusters try to blow up a still!

I'm pretty sure a still would blow up during the show - the question would be, because of an ethanol explosion, or because they filled it with gas because it wouldn't explode

I think any explosion would be an initial physical explosion due to a pressurised vessel failing, followed by a large but mostly harmless fuel/air fireball as the ethanol vapor sprayed throughout the area contacted the flame.

decoy · Post by **decoy** » Sun Jan 22, 2006 7:55 pm

i am visualising it now...

shit it wont blow, quickly finshing the batch and we will drink it while filling the still full of dynamite, or droping it from a 100 ft crane..

i might try emailing it in to Mythbusters...

anybody here from the US care to donate a still so they can blow it up ...

Watershed · Post by **Watershed** » Mon Jan 23, 2006 1:03 am

I've had pin hole leeks that burn quite stably, worst case would be the top lifting off and a high proof igniting - I know it won't explode but 50cc of rum in a flambe makes flames that touch the ceiling. 1gal of 90% might not just touch a wooden ceiling. ...

Thorin · Post by **Thorin** » Mon Jan 23, 2006 5:45 am

Hillbilly Rebel wrote:I would be real carefull about clamping your pot still for the purpose of building up pressure. You may get more than you are asking for, it could explode. Old timers tell me that Naplam has nothing on exploding mash for a really bad burn. They also knew exactly how big a rock to put on top of their cap to give them the pressure they wanted but to still act as a pressure valve if they got to much pressure. Make sure you have a pressure guage and take it very slowly, IMHO.

hmm... was a still in Bergen that blew up noit long ago. they said it was a rather huge explotion...

i'll build in a few valves to guard my pressure,
incase the coolers block up or something...

I dont think having more pressure will be good...

Thorin

Watershed · Post by **Watershed** » Mon Jan 23, 2006 9:45 am

That's why I like the dough seal - it's go no strength. There's not much to my still to block up - the pot goes straight to coil with a very short lyne arm. One single 90degree compression fitting and I listen to the outlet every fifteen mins ( yes you can hear it boiling without get alcohol in your ear ).

You'll only get an explosion where you've got a fuel/air mix. There shouldn't be any air in the once liquid's coming out of the condenser. Open it or let the still cool part way and you'll let air in.

I still can't find anything along the lines of a how the water/ethanol vapour pressure changes with varying pressure. Not that I've got any good reason for needing to know.

stoker · Post by **stoker** » Mon Jan 23, 2006 10:32 am

You'll only get an explosion where you've got a fuel/air mix.

a physical explosion if also possible. coused by the pressure building up, without fire

Watershed · Post by **Watershed** » Mon Jan 23, 2006 11:50 am

good point

Hillbilly Rebel · Post by **Hillbilly Rebel** » Mon Jan 23, 2006 6:47 pm

Exactly, that is what I was talking about. An explosion caused by excessive pressure resulting in a structure failure.

agl · Post by **agl** » Tue Feb 07, 2006 9:01 am

When I was 14, I was an idiot, and I built a pot still with a glass boiler (not pyrex) and it cracked from the thermal stress from the propane flame I was using to heat it. It kind of split in half, and as the wash spilled out, it drew air in, and promptly blew up with a spectacular bang and fireball. it spread chunks of glass everywhere. If I didn't wear glasses I would quite likely have been blinded. As it was I was incredebly lucky I had only a few cuts and a couple of hours of sweeping up glass, and mopping up sticky mash.