Structured Packing Quest

[Yummyrum]

I'm thinking a shotgun dephleg would distribute the reflux good enough.

Thats my thinking too Shady . You gonna need an RC , so why not get it to kill two birds .I also agree that there is no real need in a 2” to distribute reflux but would be in a 4” .


BigSwede , you’re making great corrugated mesh but whats got me buggered is how you are going to cut it to fit the circular biscuit without deforming it .

[BALDR]

I have been looking at larger diameter packed columns for neutral production not for volume of liquor but for manageable run times that fit in with life. Maybe it's a fool's errand, but time will tell.

One of the big things that comes up all the time when looking at column diameters above 4" is the distribution of reflux at the top of the packed column. As many have noted, the problem with poor reflux distribution can significantly degrade the efficiency of the packing. I have heard that doubling HETP could be a real possibility. In a height challenged domestic shed that is a killer, and that isn't even accounting for the cost of the actual packing.

One of the liquid distribution designs I came across and looks like something that could be DIYed is a "Gravity Liquid Distributor". One can be seen here https://www.machengineering.com/tower-i ... tributors/

gravity_liquid_distributor.png

They would sit below a dephlegmator, and work by the vapour rushing up through the chimneys and the refluxing liquid falling down and captured in the bath. The liquid forms a shallow pool and there is a positive pressure generated by the vapour rushing up towards the condenser. With the right number of right size holes the return liquid is squirted down in a controlled pattern onto the lower packing.

It is hard to imagine something like this working (or being needed) for a 2" column, but I could see it being needed for a 6" column.

It would be easy to make, start with a blank bubble plate disc that fits into the triclamp joint, drill larger holes for the chimneys and the pattern of smaller liquid distribution holes. then solder in the chimneys from short copper lengths.

Increasing the chimney length allows for higher turn down ratio, I have read up to 1:2 ratio (running at half the design power).

What got me interested in this is it improves packed column extraction performance without increasing the packed height. Obviously the distributor increases it, but nowhere as much as doubling the packed height.

Something like this with 3/4" pipe and larger holes. They have a76mm but a 67mm that would work better. Found on ebay

s-l1200 (1).webp

[shadylane]

I'm thinking a shotgun dephleg would distribute the reflux good enough.

Thats my thinking too Shady . You gonna need an RC , so why not get it to kill two birds .I also agree that there is no real need in a 2” to distribute reflux but would be in a 4” .

If using a coiled RC, another option for spreading the reflux would be to add several small whiskers to the coils so the condensed liquid would fall off the coils instead of spiraling down and dripping off the center. Something as simple as a short piece of 18gage wire wrapped around the coil and twisted so the tail ends hang down. I figure 4 - 6 of the whiskers would be all that's needed.

[shadylane]

I'm thinking structured packing is going to want the reflux spread evenly to work properly.
Maybe add several inches of mesh or SPP on top the packing to spread out the reflux.
This would be the simplest option plus gain another theoretical plate.

[BigSwede]

I love this discussion on reflux distribution. I agree I'm overthinking it on a 2" or 3" column. One very simple test would be a single biscuit in a sight glass below the reflux condenser/dephleg such that you can see both above and below the biscuit... see the entry reflux and the exit reflux. If it's coming out the bottom evenly, it's a winner. If not, there might be some work to do.

Roo, that plate thing is interesting. I can't see much vapor moving through the tiny holes. The tubes can handle some, but I think the bulk of vapor must come through the annular space... I think it's intentional with those tabs keeping the plate centered, and most of the vapor simply bypasses the plate on the periphery, while reflux gets contained and dropped into the middle 90% of the circular packing area. And it's simple, easily done by a hobbyist in any size.

Struct33.jpg

I like what I'm seeing with roll set 2. It's basically a set of gear teeth with wider than normal spacing for a diameter of that size, leaving room for mesh between teeth. It's tedious, each 7" roll being equivalent to 20 or so 1" dia. steel spur gears, but coming right along. Halfway there.

BigSwede , you’re making great corrugated mesh but whats got me buggered is how you are going to cut it to fit the circular biscuit without deforming it .

It gets slightly squished at the cut line, but really nothing too terrible, and the cuts will be in contact with the biscuit bands. My plan is this, let me know what you guys think. I'm going to make a drawing of a given diameter, and divide it into any number of chords, with the widest chord being the actual diameter. Every other chord gets progressively smaller. If the mesh is 0.15" thick, there'd be 20 for a 3", 13 for a 2", give or take.

Make 20 piles of cuts of the correct length, weld up a band (or have a tube template), stack the chords in there, band it up.

[Roo]

Roo, that plate thing is interesting. I can't see much vapor moving through the tiny holes. The tubes can handle some, but I think the bulk of vapor must come through the annular space... I think it's intentional with those tabs keeping the plate centered, and most of the vapor simply bypasses the plate on the periphery, while reflux gets contained and dropped into the middle 90% of the circular packing area. And it's simple, easily done by a hobbyist in any size.

Yeah, agree now I think about it. As you mention it the outer annular area is probably intended to be additional vapour path, with vapour rushing up through there it probably encourages falling liquid above towards the inner weir.

The smaller holes are for the liquid to be squirted out in a well designed liquid distribution pattern, I think some even use narrow tubes to provide further guidance. When properly balanced, a fluid bed builds up and the vapour squirts the liquid through. Hopefully it doesn't come to something like this, I suspect tuning it might be "fun" if needed.

I like what I'm seeing with roll set 2. It's basically a set of gear teeth with wider than normal spacing for a diameter of that size, leaving room for mesh between teeth. It's tedious, each 7" roll being equivalent to 20 or so 1" dia. steel spur gears, but coming right along. Halfway there.

That second set looks interesting, do you expect that once formed the mesh strips will have more surface area? It looks like it might.

It gets slightly squished at the cut line, but really nothing too terrible, and the cuts will be in contact with the biscuit bands. My plan is this, let me know what you guys think. I'm going to make a drawing of a given diameter, and divide it into any number of chords, with the widest chord being the actual diameter. Every other chord gets progressively smaller. If the mesh is 0.15" thick, there'd be 20 for a 3", 13 for a 2", give or take.

Make 20 piles of cuts of the correct length, weld up a band (or have a tube template), stack the chords in there, band it up.

I think it sounds like it'd work I reckon, I am assuming the biscuit will be able to compress a bit so it can be slightly oversized and compressed and inserted into the column and be self supporting. If that is the case the edges might get away with being a bit imprecise. This is what made me think about the liquid distributor on the top, get the liquid at the top ideally centred and it can work towards the walls in the way down.

How high do you think a full column targeting azeo might be? I think the higher, the more liquid centring might be needed.

[Windy City]

For this type of packing I don't think you want your reflux centered but more evenly distributed across the biscuit.
The tabs that stick out around the perimeter are called "zero wall flow".
A dephlegamator would probably suffice for distribution.
I may have to move my pumped reflux return on column #1 to above the dephleg for better dispersion.

[BigSwede]

Done fiddling with the machine. It makes excellent, well-formed mesh. The deeper gear teeth did the trick.

Struct34.jpg

On the top-left is what it made with just the triangular teeth. To the right is the improved mesh.

Struct35.jpg

It stacks nicely. Appearance-wise, it looks like the "Sulzer" lab packing from the first post. I think 45 degree will work best. But I need to finalize on a SS mesh, either 30 or 40. 20 mesh looks/feels a bit coarse.

Struct37.jpg

I'm going to start on a 2" biscuit just to get the build process down pat. My plan is to spot weld 2 bands, set those aside, then use a 1" long ring of 2" copper to stack the pieces. The copper ring will size it and the mesh structure will protrude top and bottom. Slip on a welded band, remove copper ring, add a second band, which are precut for bending out the "wall reflux diversion" tabs.

[Copperhead road]

That is a top-notch looking machine you have fabricated BigSwede.

[Roo]

That is a top-notch looking machine you have fabricated BigSwede.

I know right, were do I buy one?

Every update the hardware gets sexier.

[BigSwede]

Thanks fellas. I'm having fun with this one!

Here is the first crude attempt at forming a biscuit...

Struct38.jpg

No banding yet, just a 2" ring of copper to check the packing.

First step was to simply measure and draw on paper the circular chord lengths that should fill the 2" diameter. After making longer 8" strips at 45 degrees, I simply held them to the paper drawing and cut a bunch of chord lengths, made a pile of mesh segments, and started stacking.

Something I realized quickly is that no matter how carefully I cut with tin snips, it was hard to get a consistent dimension, both height and width. What I really need is a guillotine bench shear with stops for repeatable (and square) cuts. It's something I've always wanted, so I've got one inbound. Hopefully I can set a stop on it so if I need a 2.7" segment for example, it'll cut as many of those as needed, true and square.

I'll do a couple of 2" biscuits for practice, but I've got a 3" column to actually use, so I'm going to head towards filling that. It's a short column, which should give an indication of StP performance.

[Roo]

Thanks fellas. I'm having fun with this one!

Here is the first crude attempt at forming a biscuit...

Struct38.jpg

No banding yet, just a 2" ring of copper to check the packing.

Do you know how tall to make the biscuit? Most of the commerical images I have seen they have a squat aspect ratio... but then they are also up to meters in diameter.

I have no idea, but from an assembly point of view I imagine the taller version is more efficient (in terms of effort) to assemble, but it reduces the opportunity for change in direction (fewer stacked biscuits) in a column.

I'll do a couple of 2" biscuits for practice, but I've got a 3" column to actually use, so I'm going to head towards filling that. It's a short column, which should give an indication of StP performance.

Makes sense, especially if that is a setup you have used before and have a sense of how it performed with previous packing.

[shadylane]

Thanks fellas. I'm having fun with this one!

Here is the first crude attempt at forming a biscuit...

What's between the crimped mesh or is that another crimped strip that alternates every 90'

[googe]

Awesome stuff BigSwede, always wanted to try a similar idea from past ideas, using as much contact area as possible. I remeber someone saying use something like the inside of cardboard, the wavey cardboard innards, just like you have done. Great idea, minimal rc requirement.

[BigSwede]

Do you know how tall to make the biscuit? Most of the commerical images I have seen they have a squat aspect ratio... but then they are also up to meters in diameter.

I have no idea, but from an assembly point of view I imagine the taller version is more efficient (in terms of effort) to assemble, but it reduces the opportunity for change in direction (fewer stacked biscuits) in a column.

Roo I have no idea about best height/diameter ratio. That stack pictured is 2.5" tall, so just a bit more than the column ID. I'm just guessing at this point. I wouldn't want to go any less than a 1/1 ratio, just for ease of assembly. Placing the individual segments by hand (and banding) into a really wide but short biscuit would be difficult.

I'm hoping "practice makes perfect" kicks in. It's not hard to stack them, just fiddly.

What's between the crimped mesh or is that another crimped strip that alternates every 90'

Weird isn't it? What you are seeing is an angle looking down the 45 degree channels of every other segment. The alternating sections look different but are the same material. If I rotate the biscuit 90 degrees from that first view you can see the entire form. It's optically alive!

Struct39.jpg

The hardest part at this early stage is banding them. I can spot weld a band, but slipping it over the stack is tricky. I can squeeze with that hose clamp but I don't want to deform the structure. I'll figure something out.

[Windy City]

Do you know how tall to make the biscuit? Most of the commerical images I have seen they have a squat aspect ratio... but then they are also up to meters in diameter.

When I reached out to the manufacturer the told me the 4" diameter biscuit is 4" tall so I am guessing 1 to 1

The hardest part at this early stage is banding them. I can spot weld a band, but slipping it over the stack is tricky. I can squeeze with that hose clamp but I don't want to deform the structure. I'll figure something out.

I think if you make the band out of thin stainless and then cut the zero wall flow tabs and bend them out a little it might make it a lot eaisier to slip it over and onto the mesh

[BigSwede]

I think if you make the band out of thin stainless and then cut the zero wall flow tabs and bend them out a little it might make it a lot eaisier to slip it over and onto the mesh

A height/diameter of 1/1 seems like a good starting point.

Windy, thank you for this simple idea. A band made of mesh has holes, and every prickly wire bit poking out of the stack enters the band holes and keeps it from sliding on. Need to source some very thin stainless sheet.

I tried spot welding copper sheet, it doesn't work. So stainless is the ticket.

[BigSwede]

Permit me to geek out a bit, I'm so excited!

The whole spot welding band thing had me going until Windy City suggested SS shim stock, which I have incoming, and a shear. That'll solve those problems.

But a bigger problem is stacking, securing, holding a circular pile of mesh segments so as to bind up into a proper biscuit. They move, are fiddly as hell, and don't want to behave.

I remembered I had a tiny device called a "sput welder", used to weld small wires to large aluminum pieces for anodizing. It's a capacitator discharge machine. Looks like this, just 8" or so across.

Struct40.jpg

What you do is let the machine charge up, then forcefully contact the work, usually with a wire in an alligator clamp. Instant very neat tiny welded wire. I played with it in different ways with all the test mesh pieces I'd accumulated.

By placing two mesh pieces on a ground plate, and aligning a rod along a channel, the machine is charged, and the positive rod is tapped onto the rod in contact with the mesh.

Struct41.jpg

There's a decent little POP, and it creates a hundred micro-welds where the mesh segments contact. Zero weld of the round rod. The welds are so small you can't even see them, but it feels like I dumped super glue in there.

Struct42.jpg

I found I could do 4 at a time using less than half the machine's power. So the plan is now: Cut a ring of copper, 2" to 4". Cut that into 2 semicircles, screw those to a base plate ground. Add a mesh segment or 3, sput weld, build it up in height until I have a half biscuit. Repeat, combine the two halves.

Thanks for letting me share. I demo'd for the wife... "Uh, that's nice, have fun."

[MooseMan]

Oh that's a very clever solution BigSwede, and a cool little gadget to have at your disposal!

I would have soooo much fun in your workshop man, you'd never get rid of me!

[BigSwede]

Oh that's a very clever solution BigSwede, and a cool little gadget to have at your disposal!

I would have soooo much fun in your workshop man, you'd never get rid of me!

Thanks Moose, I'll throttle back a bit on the day to day of this project... I was just so excited to have this work, as I think it was the last real hurdle to production.

This hobby is hard to share. It's not like Fred next door understands, appreciates, and won't call the cops because he thinks your shack is going to explode.

[Salt Must Flow]

I think this is going to be another landmark thread here on Home Distiller

I look forward to seeing how this packing functions.