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I've searched around a bit but never really found much info about running perforated plates and bubble cap plates together in the one still so I decided to do an experiment and the answer, for my set up anyway is yes they work fine together.
I am currently running a 4" solid body 5 perf plate still with 4 bubble cap sections bolted to the top for a total of 9 plates and it is running fine. I would run one more bubble cap section but am limited by ceiling height. Boiler charge is 35l of 30% low wines and I am running 2 x 2400 watt heating elements with one on a controller. All plates are loaded and bubbling away like they should and it seems to be very responsive to water flow and power input changes, more-so than running all perf plates or all bubble caps but that might just be the number of plates I am using.
Hearts are just starting to come through now and the transition between heads and hearts seems fairly well defined. I'm just going to play around with the water/power settings to see what speed I can get for the hearts run. Only problem is the crappy alcometer I got from the Ukraine that has sunk and won't actually float up to tell me what the ABV is but at a guess due to the low wines, the number of plates and the alcometer only going to 96% it would be around 95% after temp correction.
Over all I'm pretty happy with the results so far.
Excellent experiment @unsub keep us posted.
No problems. I'm now using my old parrot and alcometer and it's pulling 95.6% at 2.5l p/h which is what I was aiming for to make vodka. Even at that abv it still has some wheat taste to it.
Well the runs over and it behaved really well, no surprises, no special adjustments had to be made and the added benefit of the perf plate early tails detection.
The only odd thing I found was that the top tee was an SD one with the thermowell in it and the temp never got above 74.1 on the digital thermometer. I would have thought that it should have gone up to at least the temperature that the ethanol vapour was? Could just be the thermo though. Saying that, the temp was stable at 73.9 for the entire run until very early tails when it only went up to 74.1 and the alcometer sat steady at 95.6 until tails and then dropped to 95 which is when I pulled the plug. I could probably have wrung some more out of it but was going for a clean vodka so no to very little tails were collected.
So there you go, perf plates and bubble plates worked fine together in the same still. I used the same amount of power and same amount of water as I would using them individually.
Thanks for the update. I just got two perf plates, and am planning on running a single malt whiskey using them with a single bubble plate underneath, so I will post up here regarding how they do with a flavored product as well.
Great stuff unsub. The thermo is only there really to give you an indication of changes. These are cheapies with no way to set them, so i wouldn't worry about the actual reading, more the changes.
In saying that it sounds like your temps are much more stable than mine, although i measure above the reflux condensor.
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This isn't really conventional. The normal configuration from other industry is to use the perforated plates at the bottom, with the bubble caps at the top - although it probably will not matter on this scale.
Both types of plate will work over a range of vapour speeds, so it is just a case of matching the size of the plate perforations so they work with the bubble cap.
Interested in any more comments or experimentation on this. Anyone rigged a short packed section as well?
Yes I did.
4 x 4" perf plates Crystal Dragon style under a 510mm (20") x 4" pipe that was packed tightly with SS wool.
Worked great but it was at least a year ago and those notes are long lost now.
I only remember that the product was very clean and that it was a good configuration.
Sorry my notes are lost now but organization and recall of all my test runs has never been my strong suite. Its all kind of 'right here and right now' for me because so many things fly by so quickly.
Dang, you got me wanting to do it again @rossco but scaled up to 5".
I tried a similar setup as Lloyd with 4 perf plate sections and a 510mm packed section and had a big flooding problem on the top plate and in the packed section, they were not SD perf plates though and I think the filter disk was acting like a bubble plate but with no downcomer so all the alcohol stayed in the packed section then dumped onto the top plate.
It freaked me out more than a little bit. I have since drilled out some big holes in the filter plate and had some better success.
Thanks Lloyd, I'll have a go myself. Will be by Punkins in a few weeks so I'll grab the bits I need and report how it goes. Got plenty of heads and tails. Will put down a WPOSW this afternoon. That 5" does look great.
Myles, any idea why the bubble plates would go on top rather than below? It was my understanding that one of the benefits to bubble caps was the reduced threat of clogging, which it why I figured on running mine closest to the wash. I'm not totally clear on the differences in performance between the two designs, as I have only run the bubble up till now, so I am very interested to try them out side by side for myself.
They tend to use perforated to do the grunt work of shifting the bulk of the water back into the boiler. If the column gets dirty or the boiler foams into the column then the perforated plates are more able to self clean.
A bubble cap does not really drain, but a perforated plate can continually flush and is more able to cope with a bit of contamination. To some extent it is able to self clean. Not really from solids (unless it has big perforations) but it can cope with foam.
This is mostly referring to petrochemical. It all depends how hard you run your configuration and whether you incorporate a foam breaker into the base of the column.
If you are running stripped low wines you are less likely to have problems, compared to a foam likely molasses wash for example.
There are a lot of variables that impact onto things, and in some cases it won't make any difference which order you put them into the column.
I would say though that you should only mix plates if there is a clear advantage in doing so. Both work and I am dubious if a mix works better than an either / or setup.
My goal of mixing the plates is because I had the plates already and I'm a tight arse and did not want to buy any more bits for awhile :\">
Very intersesting, I'm going to put one perforated plate under 2 bubble plates for my molasses frements. The first plate gets the most scale and it is a lot of work to clean.