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Topic: oil on surfaces  (Read 5735 times)

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Offline gudenlau

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oil on surfaces
« on: January 23, 2013, 07:47:48 AM »
Hi. I am working on a project with an oil purifier. We use rounded marbles where we create a bigger surface for the water to vaporate at 8 to 10 millibars and at about 40-50 oC from the oil-water emulsion. The surface that water can vaporate is then bigger than it would be in a thing where the oil lies vertical. We want to make the surface bigger. So I was wondering if there was a substance that could do this?

thanks in advance

Offline Enthalpy

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Re: oil on surfaces
« Reply #1 on: January 23, 2013, 10:35:27 PM »
Hi Gudenlau, welcome!

A substance to increase the area, I don't see... but you could try to spray your oil, if it's not too thick. Many small droplets would increase its area a lot. Varied injectors (search keyword) exist, including some (for rocket engines) that blow a gas at the centre of each "coaxial injector" and let the gas pulverize the liquid brought around the gas jet. Please use a neutral gas, not air with oil  ;D

A smoother process, wasting less power, might perhaps use rotating disks similar to what I describe there
http://www.chemicalforums.com/index.php?topic=57335.0
all disks would operate "in parallel" in your case. The original was meant for fractional distillation, so just remove all separations at the liquid and at the vapour sides.

Marc Schaefer, aka Enthalpy

Offline curiouscat

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Re: oil on surfaces
« Reply #2 on: January 23, 2013, 11:11:16 PM »
Use smaller marbles?

Offline Arkcon

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Re: oil on surfaces
« Reply #3 on: January 23, 2013, 11:26:25 PM »
Use smaller marbles?

The dilemma with smaller particle size is, although efficiency goes up, you end up with other problems, in this case loss, that rises greater than the benefit from more area.  The same thing happens in say, chromatographic media, smaller particles improve efficiency multiple times, but pressure rises by a squared function.  Enthalpy:'s disks, or some sort of spraying of the oil or bubbling air through would be good ideas.  The question is: how good is it now, and how good does it have to be?  Maybe, if only a small improvement i needed, slightly smaller marbles are all that's needed.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline curiouscat

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Re: oil on surfaces
« Reply #4 on: January 23, 2013, 11:39:22 PM »
Use smaller marbles?

The dilemma with smaller particle size is, although efficiency goes up, you end up with other problems, in this case loss, that rises greater than the benefit from more area.  The same thing happens in say, chromatographic media, smaller particles improve efficiency multiple times, but pressure rises by a squared function.  Enthalpy:'s disks, or some sort of spraying of the oil or bubbling air through would be good ideas.  The question is: how good is it now, and how good does it have to be?  Maybe, if only a small improvement i needed, slightly smaller marbles are all that's needed.

Agreed. Eventually the squared function will catch up.

Depends though on the details. What's the current ΔP. How much more can it be allowed etc.

Some sort of structured packing may be suitable. In vacuum duties that's common. Much lower ΔP and better Surface areas.

Offline Enthalpy

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Re: oil on surfaces
« Reply #5 on: February 10, 2013, 07:55:46 PM »
A general idea, when a stream is divided more and more finely but you don't want to drop more pressure, is to make the paths shorter and put more in parallel.

Maybe it doesn't adapt to chromatography - but maybe it does; this depends on how you wish to clean the column. For oil drying, it looks better. And it's perfect in a heat exchanger (if the fluids contain no particles) or to distribute oxygen and glucose to cells.

The perfect combination is to distribute the fluid through arteries, subdivided in arterioles and so on, down to many very short capillaries, then collect the fluid into veinules and so on, that end in a vein. With the proper tree you get as much fluid in capillaries as thin as desired, with a pressure drop as small as wished. Particle size if any, and manufacturing capability, are the only limits.

But then the engineer may have some sense of not being the original inventor.

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As an alternative to the many disks rotating slowly, one can use fewer disks (one?) that spins quickly so that the oil film is really thin, like 5µm, so it dries quickly. Like a spinning disk reactor, but used with vacuum or a dry gas instead of a reactant.

Offline Enthalpy

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Re: oil on surfaces
« Reply #6 on: February 11, 2013, 08:55:07 AM »
Thanks for having split to 65797.0 my off-topic message about chromatography - it's clearer that way.

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To dry the oil: as an alternative to the many disks rotating slowly, one can use fewer disks (one?) that spins quickly so that the oil film is really thin, like 5µm, so it dries quickly. Like a spinning disk reactor, but used with vacuum or a dry gas instead of a reactant.

Offline curiouscat

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Re: oil on surfaces
« Reply #7 on: February 11, 2013, 08:57:16 AM »
To dry the oil: as an alternative to the many disks rotating slowly, one can use fewer disks (one?) that spins quickly so that the oil film is really thin, like 5µm, so it dries quickly. Like a spinning disk reactor, but used with vacuum or a dry gas instead of a reactant.

Why would that work better? What's the math behind the tradeoff?

Offline gudenlau

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Re: oil on surfaces
« Reply #8 on: February 25, 2013, 07:42:01 AM »
Thanks for the answers. I and not the inventor, just a student. :)

I did forget to say one thing! The oil purifier got 2 drying phases where the other is air-stripping. Reducing the amount of marbles inside the coloumn did little to no effect. We belive that the air-stripping has the most effect on cleaning the mineral oil for water. So we have abandoned the idea on getting something else than marbles inside the coloumn.(we want to reduce the size on the machine to get it more mobile)

Do you guys think that the air-stripping phase kinda makes the step that leaves the contaminated oil in the coloumn less valuable?

Heres the design: http://www.ellingsen.biz/fabrications/hydrovac-oil-purifier and sorry if this restrict any rules on advertising.

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