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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.

Re: Scaling SPP for a larger Column Diameter

Postby marcus » Tue Dec 22, 2015 10:31 pm

My experiences to date with spp and 4 inch column. Picture attached is my latest 4 inch / 4Kw VM build before the insulation went on. The column uses 6 x 300mm spool pipes - each has a removable perforated plate at the bottom, and a centering collar at the top. Lucky my cave has a 3 metre stud height.
I have tried different packings over the years. My first VM still used structured copper mesh but I found that over time it got black and very hard to clean – especially in the quantity required to fill a 4 inch column - now its just falling apart and I don’t even think it would make suitable scrap. I wanted a random packing in stainless, and spp seemed the logical first choice. So I filled each of the lower 5 sections with spp to a level just below the centering collar (3Kg in each), and in the top section, I put 1.5Kg spp plus some copper scrubbers. I put a 15% wash in the boiler and fired it up (stripping with VM tap fully open). The run started well but as it continued, it started to make gurgling noises and rocking and spitting out into the collection. Some spp even ended up under the VM tap seat. I reduced the power to 3Kw and stripped perfectly. Problem solved – or so I thought. Then on to the rectifying run. Half an hour in under full reflux and liquid boiled out the top of the reflux condenser. Reducing power yet again to 1.5Kw and 45 minutes in under full reflux – same result. The spp I used is the smaller size – its about 2.2-2.3mm diameter. It sits directly on a perforated plate with 2mm diameter holes @ 3mm centres (40% open area according to the manufacturers specs). The maker of the SPP has been very helpful in suggesting possible solutions to this. I have tried some, but I still have two yet to try. One is that the spp might be packed in to tight – solution – repack it but make sure you don’t tap or bump the column. The other is that when the spp sits on the plate, because of its small size, it partially fills the holes and cuts down even further on the open area of the plate creating a restriction – solution – drill out the plate with larger holes and sit the spp on scrubbers…. Does anyone know of a suitable support for small spp other than scrubbers? I did read somewhere about cones but the problem there is that with a 4 inch column, and in my case, six cones would cut down useable column space. I did have a thought of cutting the top off a cone, inverting it and rewelding it back. Then I had the thought of getting some perf plate, bending it in a series of zig zag bends and cutting 4 inch diameter pieces on a plasma cutter. I have seen the type of support plate available that would be perfect, but so far, Ive only seen them for large industrial columns.
Meanwhile, I am using 5x5mm dixon rings made of ss mesh sitting directly on the perf plate and its humming along sweet at full power. 1Kg of 5x5 size dixon rings occupies the same volume as 3kg of the small size spp. The manufacturers specs for the Dixon rings recommend ring size for column diameter as follows:
2x2mm for columns 20-35mm diameter
3x3mm for columns 20-50mm diameter
4x4mm for columns 20-70mm diameter
5x5mm for columns 20-100mm diameter
That’s why I chose the 5x5 size. I probably could of got away with a smaller size and still avoided choking problems, but then again, I didn’t want to risk going to small and then having to get the next size up. It’s a bit of a juggling act since you really want small packing to increase surface area and liquid retention, but at the same time, you don’t want to restrict your free column volume to much. I know I should get motivated and try the spp makers suggestions, but with the new build humming along well on the Dixon rings, its easy now to sit back and be lazy – oh – and sample the product merry xmas
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Re: Scaling SPP for a larger Column Diameter

Postby dad300 » Wed Dec 23, 2015 4:55 pm

Nice rig...you're having some of the same issues I had with small SPP.

There are filter plates at stilldragon.com for 4" column that work great for my larger SPP. I would use one for each section to relieve weight.

Centering rings, I gave up on because they increased vapor speed and promoted flooding at the top, rather than whole column.

Now I got to ask...

Have you tried a shorter height? I can't imagine you need that height.

What kind of take off are you achieving? ABV? Volume?

3kw on how big a boiler volume?
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Re: Scaling SPP for a larger Column Diameter

Postby punkin » Wed Dec 23, 2015 5:25 pm

we have had some issues in some installations of the SD filter plates causing flooding at higher R/R. Others have had success like Dad
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Re: Scaling SPP for a larger Column Diameter

Postby marcus » Wed Dec 23, 2015 8:44 pm

That filter looks very similar to what I have made. Are they 2mm diameter holes @ 3mm centres? The filter I have made has openings right out to the edge so it may even have more open space than that filter. Im not having any problems with the Dixon rings sitting on it, which are possibly similar size to your larger spp. The centering rings are about 75-80mm hole diameter and they are not within the packing. I would say the vapour speed within the small spp and possibly even within the Dixon rings (by the time they are retaining liquid) would be similar or even more than the vapour speed through the centering ring – anyways its not causing any problems. Yes you are right – Im sure I could easily remove a section or two or three – that’s the whole idea of it but I have spent so much time on it over the last 6-9 months that those tests will have to wait. I have only done two rectifying runs with it and I set the R/R at 90% (collecting about 27ml/min @ 4Kw) and it produces azo right up to boiler temp 97.5*C. When I get motivated again, I will experiment with R/R and see how hard I can push it. The boiler is officially 100 liter, but you could put more in no problem. 115 litres will fill it to about 100mm below the upper side of the 6 inch port
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Re: Scaling SPP for a larger Column Diameter

Postby marcus » Wed Dec 23, 2015 11:33 pm

this is more the type of support I had in mind - anyone know of these for 4 inch? I did see one somewhere for 4 inch, but the holes would of been to big for the small spp
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Re: Scaling SPP for a larger Column Diameter

Postby plipek1 » Wed Jan 04, 2017 11:22 am

Hello

I use a large SPP in columns with a diameter of 10cm / 4 inch.
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