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water for dbl boiler on grains

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water for dbl boiler on grains

Postby casino_boy » Sat Sep 22, 2012 3:05 pm

Hello,
I distill my grain wash in a double boiler using water in a big pot and raise my milk can with canning rings so not to contact the boiler bottom. Its a simple pot still with a thumper right after my be a 18 inch rise on the still head then condenser.
It seems that i start out at output around 70% or so but when i get to around 60% it auto shuts down distilling to just a very slow drip then.
I find that when it starts it runs normal like it does when not using a double boiler (i seem to get more product and taste out doing it this way) and was wondering if this is the norm?
Temp on the still head is around 192 and about where i would stop any ways but was wondering if there was a way around this other than using a different liquid replacing my water?
Was thinking on trying sand but was afraid that would scorch my boiler using the grains as i have a bit of the grains in there.
Cheers
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Re: water for dbl boiler on grains

Postby Swede » Sat Sep 22, 2012 5:19 pm

That sounds kinda fishy....

First off, what are you heating your double boiler with?

If you don't have enough BTU's to effect a change of state once the (boiling point) BP of the wash gets past a certain point you wouldn't be able to get any product.

Put it this way, the BP of a mash with alcohol in it will be lower than the BP of a mash with very little alcohol...that's just the way it is.

You need less BTU to get the wash boiling when the alc content is higher at the beginning of the run, but later on in the run, the BTU losses of the double boiler and trying to keep the wash boiling might not be enough to get the wash to "boil" or evaporate anymore.

Maybe you could put up a few pics of your equipment so we can see what your dealing with.
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Re: water for dbl boiler on grains

Postby casino_boy » Sat Sep 22, 2012 6:16 pm

at work atm
but i use a turkey fryer burner mybe 54,000 btu.
I get 3 qrts of product out slowly turning up the heat as i go but near the end when it is boiling in the pot visibly near the end drips out.
Thought i might be able to get below 60% does this help?
8 gallon milk can
15 gal BOP
thanks
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Re: water for dbl boiler on grains

Postby casino_boy » Sat Sep 22, 2012 8:27 pm

the BTU losses of the double boiler and trying to keep the wash boiling might not be enough to get the wash to "boil" or evaporate anymore.

I guess i am at that point.

Any one use sand for heating on the grain?

Cheers
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Re: water for dbl boiler on grains

Postby Zymurgy Bob » Sat Sep 22, 2012 10:29 pm

Actually, it sounds just about right. Ask Myles about his efforts to distill with a water bath. The energy transfer function, the one that controls how fast energy moves from your bath to your wash, has a delta-T factor in it. Delta-T is the temperature difference between the bath and the wash. As the concentration of ethanol in the wash goes down, the wash boiling temperature approaches the bath boiling temperature and delta-T approaches zero. As delta-T approaches zero, so does heat transfer.

Myles solved it ny going to propylene glycol for the bath. It always boils at a temperature significantly greater than the wash, so delta-T is large, and so is heat transfer, and the still works.
Zymurgy Bob, a simple potstiller http://www.kelleybarts.com/zymurgy-bob- ... e-spirits/

You can make whisky in a reflux still, you can make vodka in a potstill,
and you can eat chicken noodle soup with a crescent wrench. But...
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Re: water for dbl boiler on grains

Postby myles » Sun Sep 23, 2012 9:33 am

Spot on description ZB. It is why most double boiler cookers that are commercially made, use either steam or a thermal transfer fluid. You need to increase the temperature gradient between the bath and the inner pot contents.

As a simple experiment try to boil water in a pan sitting inside another pan of water. It takes ages and lots of heat. If you are using a stainless inner pot it is even worse because stainless is not that good at transferring heat. Copper is a much better choice.

EDIT: ALSO unless you seal well, a lot of your energy input is lost in the form of steam escaping from the bath.
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Re: water for dbl boiler on grains

Postby casino_boy » Sun Sep 23, 2012 2:27 pm

Thanks guys ZB a myles i guess that answers my question i was guessing that it was some thing like this just wanted to be sure.
What about sand a 2 inch layer on the bottom and up the sides might this work or am I fighting a loosing battle?
i never did like scrubbing pots in the service or now.
Cheers
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Re: water for dbl boiler on grains

Postby myles » Sun Sep 23, 2012 3:47 pm

Sand will work although I have not used it so I honestly can't say how good it is. My experience is with veg oil and glycol. I like the glycol. It is food safe (if you get the correct one) and at the in use temperatures it is well below the smoke point.

Now I would only heat to 115 to 118 deg C to extend the life of the glycol. You can go much higher but glycol is not cheap and it starts to degrade if it gets over 121 degrees C.

If I had the cash I would use pressurised steam but I would NEVER self build. Glycol gives you the same temperature gradient but with no pressure change.
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