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Scaling SPP for a larger Column Diameter

These usually have the means for returning the spirits to the column and usually allow metering of the take off to help in the reflux.

Scaling SPP for a larger Column Diameter

Postby dad300 » Fri Mar 07, 2014 5:26 pm

So, my 3" x 36" Column is packed with 30" of SS SPP, larger than most current SPP.

I want a 4" column for all the obvious reasons.

So, I'm scaling up my SPP design approximately 25% for the new 4" dia. Idea being to keep the SPP dia within the approx 1/12th of the column dia. ref Previous design Rule of Thumb has been 1/10th - 1/12th.

In the previous version I attempted to use the 2" data that is out there and scale up for a 3" column. While my HETP was about 20% greater, my throughput was also about 20% higher (proportionately).

New SPP.jpg


The new mandrel also purposely causes a more open twist, there are small vents on the sides of the bits.

The column will start at 4" x 20" and all SPP. Its first run is at least a few weeks away. I have half the SPP and will be a week for the rest.

Comments welcomed...I'd like to hear comments on scaling up or down to column height.

manu, have you put any of yours in a larger column?
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Re: Scaling SPP for a larger Column Diameter

Postby 700G » Sat Mar 08, 2014 1:59 am

I can't offer any constructive comments, but will eagerly await your test results!
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Re: Scaling SPP for a larger Column Diameter

Postby manu de hanoi » Sun Mar 09, 2014 12:03 am

dad300 wrote:
manu, have you put any of yours in a larger column?

nope, max was 3" and I'm eagerly waiting for a comparative test of different diameters of SPP on a given column diameter.
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Re: Scaling SPP for a larger Column Diameter

Postby myles » Sun Mar 09, 2014 2:55 am

Are you going to try this with no induced reflux also? I am curious about the level of performance you can get without a reflux condenser.
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Re: Scaling SPP for a larger Column Diameter

Postby skow69 » Sun Mar 09, 2014 7:42 am

dad300 wrote:In the previous version I attempted to use the 2" data that is out there and scale up for a 3" column. While my HETP was about 20% greater, my throughput was also about 20% higher (proportionately).

Is that greater like better, shorter, or greater like taller?

I am also watching with great interest.

Is this Manu's product?
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Re: Scaling SPP for a larger Column Diameter

Postby dad300 » Mon Mar 10, 2014 1:06 pm

Skow, It is home made...and that makes the production slloooowww...I spin it on a lath which is very fast, but I cut it by hand and that hurts. I have a gallon ready... the 4" x 20" takes a little bit more than a gallon.

20% greater in all, dia & length. All though that makes the interior space (void) bigger and the weight per bit is not 20% greater! So the heat/energy mass will be less.

I'm feeling confident so I'm going ahead and making the second gallon. And I don't have a ferment ready...

Myles, I will be testing it with & without reflux. I'll be more excited to get three plates without than 12 with reflux.

I wanted to stay with the 20" packing of SPP, because that way I will have two sizes of SPP and enough to fill 20" of 4" column. The size I labeled as Previous I already have more five quarts of.

I will still have one difference that queers the direct size comparison. The Previous is etched with feric acid and I do not intend to etch the New until I see it's performance.

I've found some new literature about using random packings in larger columns. The tests were performed on a 4' (48") column and they used .75", 1.75" and 3" dia x 4" metal rings packing. So, 1.75" in 48" is 1/27th, and 3" in 48" is 1/16th... The results seemed to be that gases needed the larger sizes.

What I'm making is 8mm for 100mm column or ~1/12th. So, it may still be a little large for the 100mm column. But I'll have my old SPP 6mm to test against it and that will be ~1/16th column dia.

So, if the new stuff is too large for the 4" column, we'll just put it in a 6" dia column....ha....no, we won't...
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Re: Scaling SPP for a larger Column Diameter

Postby dad300 » Mon Apr 21, 2014 8:54 pm

Well, had a slightly dissatisfying trial...

14 gallons of 12% wash, in the 15 gallon keg (unmodified keg with 2" connection), 4" x 24" packed with 20" of new larger SPP, SS Scrubbie top and bottom....
4inch VM r.jpg


I knew the column was short, and probably short of azeo, but I wanted to get a better calculation of the number of plates. I wanted min reflux with reflux coil as high as I could get it. Let's say as close to 1:1 as possible.

I heated it slow and equalized for ten minutes after vapor reached the takeoff. It did achieve 100% reflux, so Reflux Coil is good to go. I raised the reflux coil and got drops for take off. I increased gas way beyond what I had expected to use and got a flow of approx a quart every ten minute. It started and ended at 92% abv with about 6 liters collected...

The dissatisfying part is the speed. Probably my fault. First, I was unwilling to throw a lot of power into it.

Second, the SPP never reach saturation/fluidized bed...I just don't think there was enough ethanol in the boiler. And...

Third, I think that the 2" connection may have caused a vapor speed problem. Too high a vapor speed at least in the bottom.

One other thing occurred that leads me to think vapor speed problem. The temp of my cooling water out of reflux coil surged up and down. Never had this before. City water in at ~66 deg F out at 100-140 deg F in cycles of about six to eight minutes.

Maybe a keg boiler just can't support the needs of this column??

Vapor speed caused the column to load/choke/dump back to boiler??? I've seen videos of plates doing something similar.

Next, I will try it over a 3" connection, longer equalization, more ethanol in boiler and throw the coals to it!

I have the stuff for this to be a 48" column with 40" of SPP. But that means the column will need more power and more ethanol.

Appreciate any and all ideas...

I had another experiment also.

I capped the top and pot stilled another charge of same ferment, through the SPP. I got a little more free with the power.
4 inch capped r.jpg


This was more satisfying. 7.5 liters at 76%. It hit 82 for first two. So, without induced reflux it made just short of three plates.

But, a liter ever 5 minutes. It took longer to heat it up (50 min)than to collect it (40 min)!

I took all this and dropped it into the 3" next day and really made for some beautiful neutral.
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Re: Scaling SPP for a larger Column Diameter

Postby jarheadshiner » Tue Apr 22, 2014 2:52 am

As you know I built a 2" VM column of your/Manu's design Dad, but run it over a 15.5 gallon keg thumper. I only charge the thumper with enough water to cover the bottom of the tube (1 to 2 gallons) so I have a large amount of head space for vapor to accumulate slowly before it ever enters the column.

I realize that the column diameter is the largest factor in relation to takeoff speed, but I believe that this large void has to be (at least part) of the reason that I can takeoff off at faster than normal rates for a column of this diameter. I am not a science guy, but if the vapor has this large void to begin with, then it has to be entering the column at a slower speed initially and a lot of it.

I know it may defeat the purpose of what you are trying to achieve with respect to the efficiency of the SPP on a low abv wash but it might be worth trying a higher abv charge with a lot of head space at least once. If this is all nonsense, then by all means tell me.
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Re: Scaling SPP for a larger Column Diameter

Postby brantoken » Wed Apr 23, 2014 6:35 am

I wonder about the surging, when i look at the squared off edges at the bottom of the column.
I am thinking that the reflux would pool there. That might be part of the surging issue.

What if you added something like a 2 to 4 inch long tapered reducer( if one exist) , I am thinking that might help. That way if wouldn't have a physical space/area to pool. I am thinking that you might even have a small temperature change on the external column surface there to indicate the pooled liquid existed there. Might be worth checking, as I am sure a 2 x4 long reducer would cost quite a bit.

Just a thought.... may not help.
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Re: Scaling SPP for a larger Column Diameter

Postby myles » Wed Apr 23, 2014 9:03 am

dad300 wrote:Maybe a keg boiler just can't support the needs of this column??


Trying to find some information on this precise point. For any boiler there must come a point when the column is just too big relative to the amount of volatiles in the boiler.

This probably leads to instability in the column and poor performance.

Has anyone got any experience of experiments that support this?
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Re: Scaling SPP for a larger Column Diameter

Postby RandyMarshCT » Wed Apr 23, 2014 9:47 am

myles wrote:
dad300 wrote:Maybe a keg boiler just can't support the needs of this column??


Trying to find some information on this precise point. For any boiler there must come a point when the column is just too big relative to the amount of volatiles in the boiler.

This probably leads to instability in the column and poor performance.

Has anyone got any experience of experiments that support this?


IT's not the same setup, but I've run my 4" 4-plate CM column on a 8-gallon, 15.5-gallon (keg), and 26-gallon boilers. I can say, with absolute certainty, that the 8 and 15.5 gallon boilers don't run as well with a wash. By this I mean that I have a harder time keeping the plates loaded for a full run without adjusting the power. With the 26-gallon boiler, it cruises along like a dream and I don't have to raise the power until I'm just about into tails. With the smaller boilers I'm constantly messing with the cooling flow and power input. With 30% to 40% low wines, the smaller boilers seem to work much better.

Dad, do you know what fluid volume (appx) that 4" column holds with the SPP when it's in equilibrium? I bet this thing would crank (even faster that it already is) with a 30% low wine charge. If I was anywhere near you, I'd offer to let you take my big boiler to try out. I think it would make a significant difference.
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Re: Scaling SPP for a larger Column Diameter

Postby myles » Wed Apr 23, 2014 9:59 am

Thanks Randy, useful info. :8)
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Re: Scaling SPP for a larger Column Diameter

Postby dad300 » Wed Apr 23, 2014 11:58 am

One of the problems Odin reported from SPP in a larger dia column, was the weight crushed the SPP. I've had this SPP out of the column and it is not been crushed.

brantoken...I have a scrubbie at the bottom to spread the vapor and retained liquid. But, if the vapor speed changes or enough liquid pools there, I assume, the liquid will still drop to the boiler just like a collapsing plate.

I think the rising and falling temp at the top, was the column almost loaded (temp up) and then collapsing back to the boiler (temp down). Thoughts??

I may be able to prevent that from happening...by putting a sieve plate at the bottom with no downcomer. I have the plate already. I'll just replace the wide wire screen with the sieve plate. Thoughts??

This vapor speed/liquid volume balance is where I think the problem lies.

Remember, that SPP reaches it's peak performance when retaining a max amount of liquid.

So, if the void in a 4" SPP filled column (even of only 24") is ~84%, the column would need almost 1 gallon of liquid to be "Full" and reach max potential HETP. And that's 2/3rd's the ethanol charge in 14 gallons of 12% ferment.

I'm not ready for a larger boiler...so, the higher ABV boiler charge is the next test. That means I'll have to strip a few large ferments to get a decent 14 gallon boiler charge.

I still am relating this to the design of larger column's. Even an 8"-10", off the boiler plated column, feeds that column with a relatively small 2" connection, boiler to column.

I may also have a distillery within reach that would "test" the column on a larger boiler.
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Re: Scaling SPP for a larger Column Diameter

Postby ant » Mon Sep 08, 2014 1:39 pm

Well this thread is the latest addition to my personal "builds of note" list.

What do you mean by vents in the side of the mandrel?

Have you got any further with it?
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Re: Scaling SPP for a larger Column Diameter

Postby dad300 » Mon Sep 08, 2014 4:41 pm

Nothing new...I needed some drink and fell back to the 3" just to get some out.
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