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Topic: Distillation by rotating disks  (Read 10233 times)

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Offline Enthalpy

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Distillation by rotating disks
« on: March 21, 2012, 11:19:54 AM »
Hello nice people!

Fractional distillation is accomplished by varied apparatus:
http://en.wikipedia.org/wiki/Fractional_distillation
http://en.wikipedia.org/wiki/Spinning_cone
http://www.solvent--recycling.com/spinning_band_packed_column.html
but I haven't seen precisely the one I imagine, sketch below (if you're logged in):

The rotating disks expose a good area of liquid film for evaporation and condensation, while the pools are separated excepted for narrow pipes that avoid diffusion. This permits one temperature per pool and disk, and hundreds of disks are feasible.

The rotation axis is essentially horizontal; a slight tilt can let the liquid flow gently in the direction opposite to the vapour, possibly with active valves at the pipes - or use pumps.

Limited clearances between the disks and the upper part of the vessel shall minimize vapour diffusion between the stages - use labyrinths or even seals if you prefer. Active valves at the liquid can regulate to zero the pressure differences between the stages.

The vessel can resist over- or under-pressure. Adding a carrier gas to the vapour would allow the liquid to evaporate gently, without bubbles: this makes evaporation more selective. The disks can be corrugated or sintered for increased area. The apparatus can have several feeds and exits as usual.

What uses? I expect the rotating disks to evaporate and condense the compounds less quickly than other methods do, but:
- The gentle process, without spat nor local pressure and temperature fluctuations, keeps the evaporation selectivity;
- Hundreds of disks cumulate their selectivity;
- The process wastes very little power (one evaporation heat for hundreds of repeated steps) so it can be upscaled;
- The horizontal axis eases upscaling as well.

Hence I hope distillation by rotating disks may find some use where compounds are difficult to separate.

Your opinion please? Is the Schaefer distillation ::) cr*p? Or exists already? Useless? Or maybe useful in some rare cases?
Thanks!

Marc Schaefer, aka Enthalpy

Offline typhoon2028

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Re: Distillation by rotating disks
« Reply #1 on: March 21, 2012, 02:38:19 PM »
Any advantage to a cone shaped chamber with varying diameter disks?

Offline Enthalpy

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Re: Distillation by rotating disks
« Reply #2 on: March 23, 2012, 07:17:56 AM »
Any advantage to a cone shaped chamber with varying diameter disks?

- Stages are well separated
- No brutal movements and spat
this shall achieve theoretical efficiency

Offline Enthalpy

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Re: Distillation by rotating disks
« Reply #3 on: May 03, 2012, 10:36:42 AM »
Take 2mm thick stiff metal if the disks are seriously wide, then you can stack them at 8mm intervals for instance, which means 1000 disks and separation steps in an apparatus only 8m long - this is a difference with competing methods, the reason why I suggested the use for difficult separations. Other methods like particle beds can have more steps but don't separate properly the liquids at each step.

One apparatus can be flexibly divided into several sections aligned, with warmer and cooler ends alternating between them, and many inlets and outlets. That way, when you don't need 1000 successive separation steps but 10, you get the throughput of 100 apparatus in parallel - or the combination you prefer. Now it looks compact even if you evaporate without boiling.

I mentioned helices at the shaft between the disks, to prevent mixing the liquid trickling from adjacent disks. The helices don't need to be machined in the shaft; spring wire fit around the shaft should suffice.

Marc Schaefer, aka Enthalpy

Offline fledarmus

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Re: Distillation by rotating disks
« Reply #4 on: May 03, 2012, 01:32:32 PM »
Now you're getting something very close to a spinning band column. There was a time when that was the state of the art in separation technique.

Offline Enthalpy

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Re: Distillation by rotating disks
« Reply #5 on: May 03, 2012, 06:25:10 PM »
There are similarities, but the rotating disks separate properly each distillation step, both at the liquid and the gas.
They can also be 1000 rather than around 10 for a spinning band.

Offline Enthalpy

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Re: Distillation by rotating disks
« Reply #6 on: October 03, 2015, 10:39:59 AM »
Nearly the same setup can clean a gaz from impurities, including gases, fumes and aerosols - or dissolve the gas completely, or load a gas with a vapour. Home air humidifiers built similarly also claim to remove tobacco smoke after all.

The gas and the catching liquid flow transversally as on one appended sketch. This may reduce the pressure drop but it separates imperfectly the clean liquid from the used one, though wipers can improve that. Several stages would improve the exhaust cleanliness for the same liquid consumption.

Or the flows can be axial as on the other sketch. This one separates better the cleanliness stages of both the gas and the liquid but is expected to cost some more pressure. Passages permit the gas and liquid to flow by: holes on the sketch, could be slits, cuts-and-bends, stampings... Offsetting them from one disk to the next lets the gas and liquid pass by the disk faces where the useful action occurs. Many small passages ease the flow between the disks. While keeping a good ratio between the holes diameter, holes spacing and disks spacing, these can be reduced together to shrink the apparatus.

Combined designs can let the gas and liquid flow transversally in several steps through the apparatus split in sections.

Such setups accept corrosive, hot, dirty fluids more easily than other designs do with pumps. For instance, the gas can be hot SO3 + SO2 + O2 and the liquid H2SO4 dissolving SO3. I see no reason against a reaction in the same vessel. The disks can carry a catalyst too. A magnetic coupling can rotate the shaft.

Marc Schaefer, aka Enthalpy

Offline ATMyller

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Re: Distillation by rotating disks
« Reply #7 on: October 05, 2015, 04:12:05 AM »
I think it is essentially the same as spinning cone column, but trading gravity assisted solution flow for more efficient packing of evaporation surface area.
Chemists do it periodically on table.

Offline Enthalpy

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Re: Distillation by rotating disks
« Reply #8 on: October 07, 2015, 07:35:33 AM »
Thanks ATMyller, I appreciate!

https://en.wikipedia.org/wiki/Spinning_cone
http://www.conetech.com/spinning-cone-column/ (drawings there)

Both methods to evaporate dissolved gases or dissolve a separate gas are similar indeed. Comparing:
- The more gentle disks relying on capillarity, they restrict more the operation conditions, for instance cleanliness.
- Muds could disturb the cones more if they settle near the shaft. Maybe.
- Disks can pack more contact area but the cones' turbulent flow is more efficient.
- If an other reaction accompanies a dissolution, the disks can carry a catalyst over a bigger area and closer to the liquid-gas interface.
- Assembling and servicing favours the disks.

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