packed column operation strategy

[MtRainier]

Is it better to try to boost the heat up until the reflux condenser almost can't handle it and you're on the edge of flooding the column and then start backing off cooling to let some vapor through to the product condenser?

Or is it better to just run the heat at a moderate level so that the water coming out of the reflux condenser is just a bit lower than the vapor temperature, say in the 70s, at a reasonably slow takeoff rate?

I know the first way takes more energy and water, but I'm wondering which way gives better tails compression. The first way will have more liquid in the column getting redistilled for sure, but I can't decide if it seems like it would make a difference or not. Seems like it might because there would be a higher reflux ratio happening.

I haven't run a packed column much to try to clean up feints, only a flute with perf plates, which is different. With plates, you're kind of more limited by the height of the overflow for how much liquid you can hold in the column getting distilled...

[Expat]

Optimal to my understanding is when you've increased the power input until the column floods on top of the packing and then backed off very slightly, then adjusting the reflux condenser cooling water until its barely knocking down everything. If your goal is tails compression, then allowing the column to reach equilibrium before taking off product is the way to go.

[MtRainier]

Got it, thanks. That's what made sense to me.

Gonna see if I can really clean up some feints and make some coffee liqueur and do the one where you hang a lemon over it in a jar.

[still_stirrin]

I agree with Expat.

But I have a combination LM/VM head. I start with both valves closed and bring the heat up and follow the heat as it rises up the column with my hand. I can feel when the vapor is at the top and the RC is knocking it all down. After a little stabilization, I’ll open the LM valve and collect the foreshots.

Then, I’ll crack open the VM valve (after closing the LM & restabilizing for a short bit). I manage the RC coolant flow so it knocks down the full load with both valves closed. This may require me to back down the heat input slightly after the reflux starts. But I try to keep the heat as high as possible so the purity stays high throughout the run. The VM output pretty much self regulates and does a fantastic job at compressing the tails.

In fact, it will produce until it stops. Then I’ll close the VM and crack open the LM again and draw the backend off. The proof usually falls very rapidly at this point and the run is nearly done. It scavenges the alcohol out of the wash very effectively.
ss

[MtRainier]

Thanks. I need a taller ceiling and another order of scrubbies too, heh.

[still_stirrin]

Thanks. I need a taller ceiling and another order of scrubbies too, heh.

Glass marbles work for me...and they’re VERY inexpensive.

Can’t help with the distilling shed infrastructure shortfall though.
ss

[shadylane]

A lot depends on what type of reflux management is being used.
My rig is a CM, it would be different if it was a LM or VM.
I run as much power as possible without puking or flooding.
The defleg is adjusted until the column is running at 99% reflux
I leave it that way while the forshot's slowly drip away.
Then the cooling water to the defleg is turned down, to let more alcohol pass for the rest of the run.
posting with SS

[MtRainier]

Thanks. I need a taller ceiling and another order of scrubbies too, heh.

Glass marbles work for me...and they’re VERY inexpensive.

Can’t help with the distilling shed infrastructure shortfall though.
ss

I'll look into marbles. They sure would be easier to clean and remove the stink from than scrubbies which all kind of latch on to each other and are a pain to deal with sometimes.

[MtRainier]

A lot depends on what type of reflux management is being used.
My rig is a CM, it would be different if it was a LM or VM.
I run as much power as possible without puking or flooding.
The defleg is adjusted until the column is running at 99% reflux
I leave it that way while the forshot's slowly drip away.
Then the cooling water to the defleg is turned down, to let more alcohol pass for the rest of the run.
posting with SS

Great, I'm on a CM too. It's just my flute with seven 6-inch sections with the dephleg at the top, all the plates taken out, and filled with scrubbies.

Sounds like the consensus is max power and max knockdown.

[shadylane]

Great, I'm on a CM too. It's just my flute with seven 6-inch sections with the dephleg at the top, all the plates taken out, and filled with scrubbies.

Sounds like the consensus is max power and max knockdown.

Just barely enough knockdown power during 100% reflux
We don't want the reflux being cooled more than needed

[OtisT]

Sounds like the consensus is max power and max knockdown.

Not max power. The way I read the recommendations, it was max power without flooding. So let the column heat up (equilibrium), bring it to a light flood, lower cooling so it’s just enough that vapor does not pass, then lower power just below a flood.

I think you said you may switch to marbles from scrubbies/mesh. Be aware that marbles take longer to reach equilibrium are much slower to react to power changes verses mesh, due to the much larger thermal mass of the marbles. So, make small changes and give the column time to react before adjusting further, or you can overcorrect.

Otis

[MtRainier]

Right, I mean max power for my rig's ability to knock down the vapors, not turn the dial all the way to 11.

The heating element on my boiler with 4" column is 5500W, and I can pretty much knock down 4kW with my 6 inch stainless dephleg, but the water going in is 18C and the water going out is 30C with a trickle of product still coming out, so it's clear that it isn't transferring much heat to the water which is really blowing through there. It seems pretty wasteful on the water front.

When I was running plates I'd flood it at 5500W, scrubbies let more back down I guess, so I don't think I can really flood them at 5500W in the 4 inch column. It's more a question of how much cooling water do I want to use, I think.

[still_stirrin]

...Be aware that marbles take longer to reach equilibrium are much slower to react to power changes verses mesh, due to the much larger thermal mass of the marbles. So, make small changes and give the column time to react before adjusting further, or you can overcorrect...

Marbles are more mass than stainless or copper scrubbies, granted. But, glass is a great insulator, so it doesn’t hold heat. It provides a surface that the vapors can condense on, especially as falling condensate pulls what heat is conducted onto the glass surface.

Much like scoria (lava rock), the heat is tranferred from hot, rising vapors to the cooled, falling condensate. The surface area for this heat transfer is greater for scoria than glass marbles, but marbles are cheap and easy to manage, both in filling/removal as well as cleaning.

What you want for packing is something with a large surface per unit volume, with a good path for vapors to flow, yet contact. Also, good insulation properties (for the packing) so that heat is transferred between the vapors to the condensate and NOT get absorbed into the packing (heat sink).

As a result of the insulating properties of glass, the responsiveness of the marble packing is surprisingly good. Mine will adjust very quickly when heat input is made, as I get vapor changes quickly at the VM valve. In fact, it is the coolant flow rate that is the most reactive (delayed from adjustment changes to effective changes).

One thing to consider with the choice of glass marbles for packing is the diameter relationship of the marbles to the diameter of the column. Large marbles have more surface area per marble, but with a lower pack density, they have less surface area per unit column volume. And if the marbles are too small, the pack density is greater and the resistance to rising vapors is correspondingly increased.

So, there is an optimal marble diameter to column diameter which best matches the heat input and vapor production (and reflux) rate. For a 2” to 3” diameter column, I believe 1/2” or 12-14mm diameter marbles will work efficiently. For a larger diameter, 4” or so, I believe 3/4” or 16-18mm diameter of marbles would be optimum.

Marbles are cheap...I got mine from the Hobby Lobby...so, give them a try.
ss

[hpby98]

Thanks. I need a taller ceiling and another order of scrubbies too, heh.

Try 1/4 to 1/2” lava stones

Took me from 92 to 95% compared to packed with copper packing

[MtRainier]

Thanks. I need a taller ceiling and another order of scrubbies too, heh.

Try 1/4 to 1/2” lava stones

Took me from 92 to 95% compared to packed with copper packing

I'd read a few posts about lava stones. I'll look into that too. That's a nice increase.

Thanks for the advice, folks. I am running the same neutral through again tonight trying to get it cleaner and also because I don't have any other ferments to run.

I ran the feints through last night before getting the above advice, and it ran at around 95% the whole time at 2kW. This time I was going for as high a heat as I could knock down so I ran at 3kW with lots of flow through the dephleg (temp in is 18, temp out is 28) and just getting drips of fores or yucky heads out for a while. Then instead of turning down cooling I just started raising heat slowly until I got a nice slow stream. That should get me to pretty much the maximum reflux my dephleg can handle. I'm at 4kW and collecting about 1.5 liters per hour at 96% now according to my hydrometer as measured on the bottom of the meniscus.

[shadylane]

When I was running plates I'd flood it at 5500W, scrubbies let more back down I guess, so I don't think I can really flood them at 5500W in the 4 inch column.

I don't know what it takes to flood a 4" packed with scrubbies
But I know It can handle 2 X 4500w
On my 4" rig the limit isn't the column or defleg
It's transferring the max power to the wash/mash without the pot foaming up, boiling over, puking

It's more a question of how much cooling water do I want to use, I think.

I think your right
In my neck of the woods, water is cheap
And there's always a use for waste water from the still.

[MtRainier]

I don't know what it takes to flood a 4" packed with scrubbies
But I know It can handle 2 X 4500w
On my 4" rig the limit isn't the column or defleg
It's transferring the max power to the wash/mash without the pot foaming up, boiling over, puking

I hear ya. I've only puked badly once, and it happened so fast. I turned around and next thing I knew the column was full of brown liquid.

This won't foam up cause it's all feints, but I'd be worried if it was a batch of sugar shine. That stuff I'll make in big batches, strip fast, then run through the column when I have a bunch. After this I don't need to do that for a while, though, because I'll have gallons of neutral to play with. Gotta get good at making Odin's Easy Gin for my father in law.

[bluefish_dist]

I found that I had best performance at right around 20 fps vapor speed. If I ran it just below flooding I was usually running too hard and abv suffered. On my 4” I ran at 5500w and the 6” at my max power of 8000w, 2” was best around 1600w.

I for reflux I would start out slow and reduce it while watching the abv, once it dropped below 190.5, I would start increasing reflux to keep the abv high enough to be vodka.

Now I have a 4” column packed with marbles that I am going to use for flavored product, so I will run it at a much lower abv, say 130 proof for my barrel aged products. I will run it same, adjust reflux to hit 130 then slowly increase it as the abv drops during the run.

[shadylane]

I've only puked badly once, and it happened so fast. I turned around and next thing I knew the column was full of brown liquid.

I've got a sight glass between the boiler and column
It's handy when running 6kw on a 4" column

[Expat]

I've only puked badly once, and it happened so fast. I turned around and next thing I knew the column was full of brown liquid.

I've got a sight glass between the boiler and column
It's handy when running 6kw on a 4" column

+1 to what Shady said. Having a sight glass above the boiler is super useful!

[shadylane]

A friend uses his column for stripping
He will let the column equalize and draw off the forshots
Then turn off the defleg cooling water to finish stripping

[MtRainier]

A friend uses his column for stripping
He will let the column equalize and draw off the forshots
Then turn off the defleg cooling water to finish stripping

Hey, neat idea. I betit does help have a nicer spirit run to be able to pull off that first bit of nasty separately.

[MtRainier]

so both lava stones and glass marbles are not good conductors of heat.

Does it work better to separate fractions to have the column full of insulators that don't want to give up their heat to the condensed liquid and have the rising vapor evaporate what's trickling down?

Or does it work better to have the column full of conductors (scrubbies or SPP) that would be, I assume, hot enough and conductive enough to evaporate the descending liquid directly because they're kept heated by the rising vapors.