Huffing below boiling temp

This hobby is fun & enjoyable, but it is not tiddlywinks. Be safe!

Moderator: Site Moderator

Post Reply
Micmac
Novice
Posts: 21
Joined: Wed Feb 14, 2018 8:56 am

Huffing below boiling temp

Post by Micmac »

Hi all,

Total novice here, learning much on the site! Did my first run the other day which I will call a hybrid stripping run. I’ve run my reflux still (mile-hi 3” torpedo) in both reflux and pot still mode with water and all ran well. First alcohol wash I wanted to see if I could lower the length of the column by taking out some sections and reduce packing to make it more pot still worthy. Everything went great with slow rise temp. Toward the end of the run I wanted to see if I raised the heat like I guess I would if I would a pure stripping so cranked the power to the element a bit. Over 205F in the boiler I started to see the discharge product warming with some huffing. I turned the heat down a bit and all was good. Water flow to the condenser was constant and water discharge seemed cool. Question I have is did I just overpower the condenser? Did my shortening the column effect the performance? Was the vapor velocity just too fast? If I put more copper packing in the column would that be of benifit? Of note it was very cold when I was distilling around 38F. Would that have any impact. Trying to make sure things don’t go boom!
ShineRunner
Swill Maker
Posts: 464
Joined: Tue Dec 08, 2015 11:12 am

Re: Huffing below boiling temp

Post by ShineRunner »

This has been discussed many times on here. Check the HD google search out. There’s a link in my signature.

Short answer is twofold. First, is that your still will act differently when condensing alcohol. Secondly, you’re overcooling the vapor. Your condenser discharge water should be hot as it exits.

Try the HD google search for more details.

SR
User avatar
Saltbush Bill
Site Mod
Posts: 9675
Joined: Thu Mar 17, 2011 2:13 am
Location: Northern NSW Australia

Re: Huffing below boiling temp

Post by Saltbush Bill »

Micmac wrote: Over 205F in the boiler I started to see the discharge product warming with some huffing. I turned the heat down a bit and all was good.
205F is 96.1111 c.....is almost boiling temp of water ...ya lucky to get that far with a potty without it huffing.
You are over thinking everything ....running your condenser so its warm at the top and cool at the bottom will help your issues.
I'm guessing that soon you will get a whole heap of answers that will revolve around temps and out put speeds, they will be over thinking it as well .....when you run it as a pot still ..run it like a pot ..........use your nose , taste buds , ears n eyes.
PS you will also get those who say read read read ...or use the search button....dont be afraid to ask questions...ever.
Micmac
Novice
Posts: 21
Joined: Wed Feb 14, 2018 8:56 am

Re: Huffing below boiling temp

Post by Micmac »

Thanks for the reply and info Saltbush. Shine runner, Not a novice to forums in general and the search function but will dig deeper next time
User avatar
still_stirrin
Master of Distillation
Posts: 10337
Joined: Tue Mar 18, 2014 7:01 am
Location: where the buffalo roam, and the deer & antelope play

Re: Huffing below boiling temp

Post by still_stirrin »

Micmac,

To add what the others have suggested, and possibly help with your question....I do believe that you are outrunning your product condenser. If the condensate is coming out warm and the coolant isn’t, then you have a mismatch in operational efficiency. Slowing the water will help pull more of the heat out. But, you may also have too small of product condenser...that is, it may be undersized for your heat input.

Also, you want a good temperature gradient in the product condenser...so the vapor doesn’t collapse and cause the sucking in of air at the spout (that’s called, “huffing”). When it’s pushing out warm vapors out of the end, like you’ve described, (that’s called, “puffing”). Puffing results from an underpowered condenser. And huffing results from an improper temperature gradient in the product condenser.

The 3” tower will take a lot of heat, especially when running in a high reflux ratio. And that is when you have it loaded with packing. So, the vapor moving to the product condenser has less mass flow (lb./hour) than when used for stripping.

In a stripping function, you’re relying on the product condenser to remove all the heat you’re putting into the boiler. While a 3” potstill will pass a lot of vapor (a large heat input), the product condenser must be capable of that as well.

You didn’t say what type of product condenser you’re using, but I assume it’s a Liebig. How long is the water jacketed section?

You can add more capacity (for stripping runs) if you add a secondary Liebig section to the end of your current one, thereby extending the cooling/condensing line path. Use a copper union to join the two and it’ll work. Run the cold water in at the bottom and couple the water outlet from the lower condenser to the input of the primary condenser...connecting them in a “series” arrangement. You can even remove the extension when doing a full reflux run as well.

Bottomline, you’re overpowering the pc. Without mods, you’ll have to reduce the heat input, which will reduce the vapor production rate. And don’t trip up thinking about temperatures. It’s the amount of heat...not the temperature of the vapor that is important.
ss
My LM/VM & Potstill: My build thread
My Cadco hotplate modification thread: Hotplate Build
My stock pot gin still: stock pot potstill
My 5-grain Bourbon recipe: Special K
Micmac
Novice
Posts: 21
Joined: Wed Feb 14, 2018 8:56 am

Re: Huffing below boiling temp

Post by Micmac »

Thanks SS for the thorough explanation. That makes a lot of sense, my guess after reading the response is it was a combination of a few factors. The 3 inch column lowered probably was allowing a high volume of vapor. I’ll play around with the water flow in the future to see if that helps. The flow rate of the distillate was more than adequate prior to cranking up the heat so I will also just keep
It in the sweet spot on future runs
Post Reply