Sciencemadness Discussion Board

The ozone generators with ceramic plates, useful?

Mateo_swe - 19-5-2020 at 09:05

The ozone generators with the ceramic plates that are everywhere on auctionsites, anyone tried them for chemistry?
I know the levels advertised should be taken with a grain of salt, or maybe more of a box of salt.
I just wonder if the ceramic plates are better than the glasstube elements.
I might buy some of the ceramic plates as they are just 3.5US$ and try out making some ozone as an experiment.
I have seen the HV units they are sold together with overheat easily but i can add my own HV supply.
Maybe one can get 5-10% of the advertised amount of ozone if lucky and i can add many plates.

The ozone units made for chemistry i have seen used 2 thin glass tubes (one inside the other) with a small distance between them, maybe 0.5 to 1mm and the inner glass tube filled with conducting liquid and same on the outside tube so there is the 0.5 -1mm space between them and then oxygen slowly pumped through.
This way only the air/oxygen between the glasstubes ionizes.
I read simple soda glass preformed better in this application than the chemglass.
Maybe this is a much better way to do it but my glass working skills are very limited.
Someone tried these ceramic plate ozone generators?

Plate_and_Trafo.jpg - 92kB 5g_ozone_per_hour_ha_ha.jpg - 36kB

Twospoons - 19-5-2020 at 13:47

I borrowed one once, and it certainly produced plenty of ozone. I would have thought the cylindrical ones more practical for chemistry, as it is far easier to attach gas tubing to take the ozone to where you need it. Plenty of those of Ebay, Aliexpress etc.

SWIM - 19-5-2020 at 16:08

Yes, cylindrical ones are the way to go. Since they only make ozone on the inside of the tube, you can use LOTS of cooling air outside and blow just enough oxygen through the middle to get good concentrations of ozone.

With the plate ones the cooling airflow and the gas the ozone is generated in is the same thing so controlling cooling and ozone production at the same time is more problematic.

Either the ones with a finned heat sink around them.

Or the cheaper un-finned ones that need extra cooling like a fan.

The 3 gram per hour tubular ones with 1 liter/min dry oxygen flow through them give decent Ozone concentrations.
Was it like 5%? EDIT: that was the 5 G/hr one, sorry.

Flow rates must be much higher for regular air, and the ozone production suffers.

From what I've read it seems that if you want high ozone levels from relatively simple equipment then electrolysis of water/sulfuric acid with an appropriate overvoltage might be a good option.

Percentages got very high, but platinum electrodes were used with really high current densities.
Cooling the solution and electrodes was vital to high yields.

[Edited on 20-5-2020 by SWIM]

[Edited on 20-5-2020 by SWIM]

G-Coupled - 19-5-2020 at 17:14

Those units look impressive, if those specs are realistic. Otherwise, you could always go with the old skool option of UVC lamps. Also might well come in handy in these dark days of pestilence. :cool:

Mateo_swe - 20-5-2020 at 04:18

The ozone production using UV produces too little ozone for chemistry applications. The discharge method produces very much more ozone.

I could build an enclosure around the ceramic plate "electrodes" and feed air or oxygen through to get all ozone produced. Same principle as the glasstube variants just applied to a flat design.

If you look into it, it seems the advertised ozone figures for the cheap ozone generators found on for example ebay are not realistic.
One youtube guy tried the glass tube variant that was advertised as 3grams/hour and got 200mg/hour out of it.
It should be said he used air for this measurement and he tried pure oxygen also getting better figures but not the advertised ones.
Here is a link to one of his youtube videos trying out the cheap 30$ ozone generator (he has several videos trying out the generator).

If the ceramic plate ozone electrodes are little better than the quartz glass variants one might get something like 500mg/h - 1gram/h out of say 1-3pcs of ceramic electrodes using just air and higher values using pure oxygen.
The HV supply usually shipped with these are not built to handle continous usage. They produce around 3.5 kV for a single plate and little more for the units using several plates.
I dont think the HV-supply will manage this continuously even if fans are applied.
But another HV-supply can be used and voltage levels adjusted for best ozone production.
I wonder if they use DC or AC voltage for the electrodes. Probably just a diode or diode bridge to get a rough DC.
Maybe a HV cap to smooth the DC will increase lifespan of the ceramic plates.

I searched my computer for a nice PDF explaining the function of a ozone generator designed for chemistry use but i havent found it yet in all the ozone PDFs i have, i continue search for it.
I include some other PDF about ozone genertors.

Attachment: ozone_generator.pdf (48kB)
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Attachment: Ozone Generation by Atmospheric Pressure Dielectric Barrier Discharge.pdf (301kB)
This file has been downloaded 125 times

Attachment: Ozone_Production_With_Dielectric_Barrier_Discharge.pdf (1.6MB)
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morganbw - 20-5-2020 at 14:55

Please look up the term "ozonide", could save you pieces of your body.

SWIM - 20-5-2020 at 19:05

I saw that video:

He was running the thing in a box with no cooling fan.

And he couldn't figure out why the longer it ran, the lower the output was.:D

The oxygen flow rate looked a little high to me for that model too.

As for those plate type generators they probably won't give you a high concentration because either it's too hot for efficient ozone production because of poor cooling or the airflow over it is too high to get a high ozone concentration.

Sure, they'll make lots of ozone, but in lots of air.
That may complicate its use in the lab.

@ Morganbw:Thanks for the warning about ozonides. I'll be careful to keep the ozone generator away from my propenyl benzenes.

G-Coupled - 21-5-2020 at 06:50

Quote: Originally posted by morganbw  
Please look up the term "ozonide", could save you pieces of your body.

People are offing themselves with these generators now?

Sounds like a slow, painful way to shuffle off this mortal coil to me...

morganbw - 21-5-2020 at 14:49

I do not think they do this with intention.
I am speaking about using ozone in a chemical reaction.

I would suggest that any who thinks about this to do some research.

This can be done safely but some knowledge is needed.

Mateo_swe - 23-5-2020 at 07:59

Yes, ozone is not healthy to breathe.
In higher concentrations its toxic like many other gases and can cause permanent damage.
That´s why it says on all ozone generators that it should only be used in an empty room, and after the use the room should be given time to ventilate away the ozone produced.
In a chemical application after the ozonolysis one should connect a tube going outside to ventilate away remaining ozone or use it in a fumehood or outside.
Luckily it smells so one directly notices if there is ozone in the air.

I wonder if one could use a thin PCB, one of the 0,5mm thick ones for ozone generation.
One can buy the empty copper boards, then place 2 of them about 1mm apart with the copper side on the outsides.
Then apply 3.5kVDC to the copper sides and push air between them.
This way the air ionizes just between the glassfibre boards and arent in conact with the copper.
And one can cool the copper on the outsides with a fan without disturbing the ozone production between the boards.
Im sure it would work, but how well it would work i have no idea.

G-Coupled - 23-5-2020 at 09:34

A peltier effect device might be good to cool the outsides of those flat electrodes. :cool:

macckone - 14-6-2020 at 16:17

to get good ozone generation you need AC or straight oxygen with electric discharge. With AC you are looking for corona discharge which is increased and higher frequencies and voltages. You also need a dielectric barrier to prevent sparking which will lead to nitric oxide contamination.

Mateo_swe - 21-6-2020 at 13:58

When one generate the high voltage with a flyback transformer it is AC voltage.
But many high voltage units does rectify the HV AC to a DC voltage with diodes and capacitors depending on the application for the high voltage.
The flyback transformers in the old thick TVs has an built in diode so they output a DC voltage.
One do get corona discharge effects with high voltage DC too but maybe its not as effective as AC high voltage.
In the case of using circuit boards there is an dielectric barrier between the copper and the other side, its the glassfiber.
It might not be the best dielectric material though.

I have ordered some Vycor quartz glass tubes that i will use for a DIY ozone generator.
The idea is that i put 2 quarts glass tubes, one inside the other and pump air or oxygen between them.
The inside tube will be filled with a conductive liquid connected to one side of the HV AC generator.
The outer side of the "outside" tube is wound with thin copper thread or i put conductive liquid there also, connected to other side of HV AC generator.
In the open space between the quarts tubes will fill with corona and have air pumped through.
So no physical connection to the electrodes between the glass tubes, just corona discharge.
It will be an interesting experiment.

cyanureeves - 21-6-2020 at 17:31

we used one of them where i worked and it was okay for the first couple times we used first it would create a fog that smelled a lot like nitric acid.after a couple of uses it would not generate fog anymore but still smelled of nitric some.

hissingnoise - 22-6-2020 at 02:28

Quote: Originally posted by cyanureeves  
we used one of them where i worked and it was okay for the first couple times we used first it would create a fog that smelled a lot like nitric acid. .

Nitric acid is produced by corona (whooops!) discharge in air when the moisture content, by its higher conductivity, causes relatively hot arcing in the plasma, which dissociates N2, allowing the formation of NOX.

The NO2 and N2O5 produced are obviously undesirable since you don't want HNO3.

Ozone generators require anhydrous air or compressed oxygen to produce ozone in better purity.

[Edited on 22-6-2020 by hissingnoise]