[Enthalpy]

Hello nice people!

Here a bizarre idea to let liquids and gas react together: see the attached sketch.

It's essentially the same hardware used to humidify air: many disks soaked partially in a liquid are rotated; they shall be wetted at each turn to expose a big area of liquid to the gas and promote the reaction.

The (better detachable) disks surface is close to the liquid-gas interface and can also be a catalyst, or be itself a reagent, for instance copper-activated zinc. This must be an advantage over other processes, like a mist or bubbles.

The gas could also be an other liquid if it's hard to mix - in case no better method exists. One could even superimpose several liquids and a gas, for instance to expose a single-molecular layer of liquid to the gas.

Sub-sub-details:

The vessel would better withstand pressure and vacuum. You can fit pumps compressors heater coolers exchangers separators and all that stuff.

Screws around the shaft between the disks and the bearings can prevent liquid wetting the shaft from seeping into the bearings - but they won't stop the gas... You can try to inject grease at high pressure in the bearing to prevent leaks there, as usual. At least no chemical has to be pumped to mix in this reactor.

You can vary the rotation speed to adjust the thickness of the liquid film. If the disk surface must be exposed to the gas close to the liquid, it could be made hydrophobic from place to place. Corrugations at the disk could even, as the disk rotates, pour the liquid at places that were in contact with the gas.

Your opinion please? Exists already? Or the Schaefer reactor is fabulous in some cases? Or it's worse than existing methods?
Marc Schaefer, aka Enthalpy

[Arkcon]

I believe the "Schaefer reactor" is a major component of the classic design of the Heart-Lung machine.  Although Wikipedia doesn't support that factoid I'd heard.  Blood was oxygenated by splashing across stainless steel disks just as you described.  Now membrane based oxygenation is done, and that method appears to be more common these days for a variety of applications -- both for blood and industrial uses.

[Enthalpy]

Thanks Arkcon!

Any progress is only half a picometre beyond the knowledge common to all Mankind, so if that design was used to oxygenate blood but not to react chemicals, or was used to react chemicals but not with catalyst disks or reactant disks, I'd consider it a slight improvement and be satisfied with it, with much self-indulgence and wishful thinking...

More comments?

[Enthalpy]

A description of the heart-lung machine, indeed with rotating disks:
www.ncbi.nlm.nih.gov/pmc/articles/PMC2028454
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2028454/pdf/brmedj03398-0009.pdf

Maximize the contact area between a liquid and a gas by creating a liquid film on a moving surface... Very similar, well done Arkcon!

Some humidifiers as well use the rotating disk stack.

It may be good for chemicals, for instance when these are difficult to pump into bubbles or droplets, or if the disks have a chemical role.

[roy]

Thanks for sharing Schaefer! It's a new knowledge for me.

I would like to give you some suggestion regarding this. May I?

The surface area for contacting had been sufficiently large for phases to contact.
But I wonder, how is the mass transfer in the liquid phase. Since the liquid in the bottom is remains static, the mass transfer is slow that it become the rate limiting step instead of the reaction rate.
So, I think it'll be better if you add something or little modification which promotes turbulence in the liquid phase. Isn't it?

[Enthalpy]

Thanks for your interest!

The liquid has its biggest contact area with the rotating disks. This will drag the liquid to make a loop, along the disks at the upper part of the bath, and returning at the lower part. This mixes the liquid in the rotation plane, and as the disks can be thin, diffusion across a few mm can be efficient enough in many cases.

[Drawing in the first post, displays for users logged in]

The axial direction is less favourable, with no natural flow there. I imagine the tank's inner face can have fins that take advantage of the loop to create some axial movement as well.

A different approach would replace the many disks by a helix, which achieves an additional global axial flow. Or, as disks are simpler to produce and fit, especially if they're consumed by the reaction, a durable helix could occupy the smaller radii near the shaft, and the consumed disks the bigger radii. Or keep individual disks, but cut and warp some fins in them to get an axial flow component.

It's new for me as well! I don't even know if something similar is commonly used.

[Enthalpy]

Wipers, standing brushes or mobile brushes, liquid jets... can wipe away from the disks reaction products or poisons that would slow down the reaction or bring other unwanted effects, maybe undesired further reaction steps. This can be done for instance where the disks enter the liquid bath.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Also to react a liquid with a gas, but while the former one was all quiet, this one is all fury... Sketch here under if you're logged in.

Inspired by the spinning apparatus that coat(ed) semiconductor wafers with photoresist. The ones I used had 50mm diameter and made around 6,000rpm. They achieved few µm thickness of a viscous liquid. A single drop at the center was mostly eject in maybe 0.1s.

Again, the disk puts the liquid reactant as a thin film in contact with the gas reactant. The quick rotation lets maybe 3mm³ flow in 0.1s, or 100cm³/h as a 3µm film, with one small disk. Increase the size and number as needed, like: 100m³/month with 100* D0.7m. Or accept a thicker film.

The disk's surface can be a catalyst; it might even be a solid reactant, but mind an unsymmetric mass loss...

The reactant gas can move just from contact with the spinning disk.

A bit unclear: bearings in the reactant gas. Or how to separate both. The disk could be fully levitated, and rotated magnetically.

Marc Schaefer, aka Enthalpy

[curiouscat]

These reactors already exist: Spinning Disk Reactors.

You might be reinventing the wheel.

[curiouscat]

A bit unclear: bearings in the reactant gas. Or how to separate both. The disk could be fully levitated, and rotated magnetically.

A stuffing box?

[Enthalpy]

These reactors already exist: Spinning Disk Reactors.

Well done, thank you!
http://alexandria.tue.nl/extra2/702643.pdf page 7.
Reinventing the wheel indeed.

[Enthalpy]

Here's an other reactor that brings a liquid and a gas in large contact - sketch appended.

The paddles can have many pourer spouts to create more droplets in a better controlled way and let the droplets fall well within the rotating drum. Bubbles created in the liquid enhance the reaction area too.

This apparatus can also react immiscible liquids, for instance molten sodium and dioxane containing a reactant. The liquids can fill the vessel completely.

The paddle wheel shall cope with dirty, hot, corrosive compounds more easily than other dousing and bubbling reactors that use pumps - for liquid metals loaded with salt for instance. While the previously described rotating disks run more smoothly and create possibly a bigger contact area, the paddle wheel doesn't need the liquid to wet any surface, hence it can accept more dirty and corrosive environments that stain the surfaces.

The paddle wheel can remove solid products or by-products if they settle under the liquid and keep mobile, as the mud will fall from the paddles after the liquid.

Some materials were developed for fast neutron reactors to resist liquid sodium and metals. If I remember properly, the base alloy gets protected from dissolution by adding a layer of metal like molybdenum, which is refractory and builds no oxide layer.

Marc Schaefer, aka Enthalpy