Building a Continuous Still for Stripping a Sugar Wash

[rad14701]

That's a very interesting discovery, Lester... Perhaps the flash expansion helps the distillation separation process...

[emptyglass]

I get busy for a few weeks and miss a whole thread.

Disclaimer, I've only had a brief roll over of 5 pages, but I'll ask the question, in case it hasn't been asked.

How much are you fermenting Lester?

There seems to be much progress made on a continuous still, many issues worked through. But, will you be able to feed this little fella all the time?

I understand your desire to continuously strip wash, but have you got enough wash to strip without shutting it down to catch up on fermenting?
If you have enough wash, how are you going to cover the times where you sleep (unless you don't...)?

Sorry if I've overlooked some fundamentals that have already been addressed.

And sorry if its already been addressed, but if you can legaly distill, whats wrong with a larger batch still? Heat recovery can be acomplishied quite easy with a batch still

[Lester]

How much are you fermenting Lester?

665 liters fermented during the month of March alone, and growing.

And sorry if its already been addressed, but if you can legaly distill, whats wrong with a larger batch still? Heat recovery can be acomplishied quite easy with a batch still

Yes you are right about that. I just enjoy making stuff and giving myself a hard time.

There's one real benefit though: With a continuous stripper the spent wash is practically stripped of all its alcohol and it's almost just water going down the drain (temp = 99.5-deg C). With a batch still I stop running at 98-deg C and it seems there's still about half a liter of alcohol in the wash, for a 19-liter load. That half liter of EtOH adds up quickly as the ferment volumes go up. Why throw it away when you can actually get it out of the wash?

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I ran the stripper again today and got 47% ABV output. While the column was stable I measured the temp at the vapor take off and also at about 8" below the take off. BOTH TEMPERATURES WERE EXACTLY THE SAME. This result leads me to conclude that the packing above the wash injection point is doing nothing at improving output ABV so I am moving the wash injection point to the top of the column. Stripper rev 2 coming up.

[YHB]

Hi Lester,

I have not contributed much but that does not mean that I have not been following this thread with interest, It's just that the numbers are above my experience and my needs.

You are taking all the alcohol of the wash, but at what feed rate? if you slow down the feed do you get a higher %?

Are you looking to increase the rate, percentage or both, by moving the injection point?

Keep up the good work.

Brian

[Lester]

Hello Brian,

Manually running a continuous stripper is like walking a tightrope, I have to keep it "balanced" all the time. It takes some effort and right now a simple potstill with a big boiler is looking very attractive.

Using constant heat input, too little feed will lower the output ABV. There's simply not enough alcohol for vapor exchange and so water vapor from the boiler gets past the packing. At least this is what I think is happening.

If I increase the feed rate the ABV will go up but at some point it will result in more EtOH going down the drain. It takes less than 1 minute for the column to stabilize at this new setting.

Further increasing the feed rate will, at some point, stop the boiling.

I am using an aquarium pump to feed the wash and as the wash depletes in the reservoir (pump head height change) the feed rate goes down ever so slightly, and as a result the ABV goes down also. I am seeing less than 4" of change in wash level when I have to re-adjust the feed rate again.

I am moving the injection point so I can have more column height available for vapor exchange. With a 4" column, it is a lot more difficult to spread the wash evenly across the packing as compared to a 2" column. I am using 2 injectors in the hope of alleviating that somewhat. More column height means more opportunities to spread the wash across the packing, and hopefully less water vapor gets past, which I hope will result in higher ABV.

Preheating the Wash results in lower ABV. I don't know why this is so. I only got ~20% ABV output so I abandoned that idea. I am theorizing that heat exchange doesn't happen when both the vapor and the wash are at almost the same temperature.

[emptyglass]

Yes you are right about that. I just enjoy making stuff and giving myself a hard time. .

Well good on you for giving it a go

[badbird]

I ran the stripper again today and got 47% ABV output. While the column was stable I measured the temp at the vapor take off and also at about 8" below the take off. BOTH TEMPERATURES WERE EXACTLY THE SAME. This result leads me to conclude that the packing above the wash injection point is doing nothing at improving output ABV so I am moving the wash injection point to the top of the column. Stripper rev 2 coming up.

Interesting results Lester, not quite what I expected but that's not unusual If lowering the wash injection temperature increased the ABV, shortly there must be some kind of reflux happening??
Like I said back near the start of thread I originally tried injecting reasonably hot wash at the top of my column (didnt try cold) but couldn't get above ~25% ABV, when the injection was moved to around the middle of the column the product takeoff jumped to ~55 ABV so it will be interesting to see just how you go. Mind you I was using a 2" copper column with scoria packing but that shouldn't make that much difference, maybe before running the stripper again ill put a few more thermo ports in the column and see if results are similar.
I see the Russians with their tall plated stripping columns appear preheat their wash and inject at the top of the column so given they have been working on this for years so they probably have it reasonably right.

I am using an aquarium pump to feed the wash and as the wash depletes in the reservoir (pump head height change) the feed rate goes down ever so slightly,

Maybe this is where a good peristaltic pump hooked to a PID controller would be worth its weight in gold, its a pity used ones are so hard to find (within my depleted budget anyway ).

[Jacksonbrown]

I ran the stripper again today and got 47% ABV output. While the column was stable I measured the temp at the vapor take off and also at about 8" below the take off. BOTH TEMPERATURES WERE EXACTLY THE SAME. This result leads me to conclude that the packing above the wash injection point is doing nothing at improving output ABV so I am moving the wash injection point to the top of the column. Stripper rev 2 coming up.

Interesting results Lester, not quite what I expected but that's not unusual If lowering the wash injection temperature increased the ABV, shortly there must be some kind of reflux happening??
Like I said back near the start of thread I originally tried injecting reasonably hot wash at the top of my column (didnt try cold) but couldn't get above ~25% ABV, when the injection was moved to around the middle of the column the product takeoff jumped to ~55 ABV so it will be interesting to see just how you go. Mind you I was using a 2" copper column with scoria packing but that shouldn't make that much difference, maybe before running the stripper again ill put a few more thermo ports in the column and see if results are similar.
I see the Russians with their tall plated stripping columns appear preheat their wash and inject at the top of the column so given they have been working on this for years so they probably have it reasonably right.

I am using an aquarium pump to feed the wash and as the wash depletes in the reservoir (pump head height change) the feed rate goes down ever so slightly,

Maybe this is where a good peristaltic pump hooked to a PID controller would be worth its weight in gold, its a pity used ones are so hard to find (within my depleted budget anyway ).

I have found very similar results.

Having packing above the injection point without any reflux being induced (passive or otherwise) is just a half finish rectifying section and a waste of column height IMO.
Interesting that cooler feed seemed to bump up the ABV. Perhaps the difference between the feed temp and feed BP converts the top of the column to a rectifying section until the feed falls to the BP temp zone. This was my hunch and I’m trying to test for it but it’s very hard to get accurate results without having excellent control of all the other parameters. I got some good results and I will persist with what I learnt.

If any math gurus are keen to try the modelling and want to design some tests I’m happy to do the grunt work.


FYI, my fumblings can be found here - http://homedistiller.org/forum/viewtopi ... =1&t=48261