Sciencemadness Discussion Board

Making an Ozone Generator

DFliyerz - 4-2-2015 at 11:07

I've always been somewhat interested in ozone, and have a fan that's been broken for a while, which had an air ionizing function. Would it be possible to, in theory, modify the air ionizing parts to work as a small-scale ozone generator?

macckone - 4-2-2015 at 11:45

Better to just buy a cheap ozone generator.
Or make a real ozone generator using the correct parts.
I doubt the ionizer on the fan actually provides enough
power for real ozone generation.

Zyklon-A - 5-2-2015 at 11:17

I have an ionizer that goes up to about 15 KV. It uses so little current that it's nearly useless for ozone or nitrogen oxides production. Sealed in a tube ionizing the air all night doesn't even make enough NO2 to be visibly brown-orange.
I bet yours is the same.

Jimmymajesty - 12-4-2015 at 09:35

I have just tried to use a homemade ozone generator to oxidize ethyl alcohol to acetic acid.

The parts:
flyback transformer scavenged from an old tv
2N3055 transistor and a couple of power resistors, you will se the drawing if you google on the "flyback transistor" term.

Take a glass tube with ~0,5cm diameter, wrap some aluminium foil around it this will be one electrode. put a copper wire inside the glass tube, this goes to the second electrode. switch it on it will generate a lot of O3. I think it will be enough to make considerable amount of acetic acid if you run it through a flask with Et-OH under reflux.

hissingnoise - 13-4-2015 at 02:32

. . . switch it on it will generate a lot of O3. .

Airfed generators produce ~3% ozone BV, but any moisture in the air will lead to production of nitric oxides!

Tetranitromethane isn't something you want in your Et/Ac?

Industrial ozone generators use efficient air-dryers for airfed types or compressed oxygen for production of high-purity ozone . . .

[Typo correction]

[Edited on 13-4-2015 by hissingnoise]

Sulaiman - 13-4-2015 at 14:17

I've experimented/played with ignition/flyback/Tesla coils etc.
I've always associated ozone with high voltages
but I can't ever remember smelling even a hint of N2O.

does ozone de-sensitise the sense of smell to N2O
or is N2O produced in only negligible quantities?

Marvin - 13-4-2015 at 15:22

Quote: Originally posted by Jimmymajesty  

flyback transformer scavenged from an old tv

To work properly in this circuit it needs to be a flyback without a multiplier or rectifier.

violet sin - 13-4-2015 at 20:19

@Marvin: HVAC only? could you elaborate?

I use an old neon sign transformer for O3. I made a simple little setup that used cheap parts I had or from ACE for the most part. only the transformer was not from there, but it was still cheap. 10 or 15$ from a yard sale for a broken-tube neon beer sign.

-used a mason jar for the main chamber( had already), a ~4" handled drain pipe cover ( 0.79$), 2x NPT threaded nylon hose barb( 1.25$), 4" length of PVC 1"ID( ~1$ per 12" , short length of expanded aluminum mesh gutter guard( had already), small square of small mesh aluminum door/window screen( had already), some 5min epoxy( ~2$), 2 strands of aluminum wire( had already), and a couple short lengths of vinyl tubing for the lead wires and 2 for the air pumped in and out from an aquarium pump.

the drain cover fit over the mouth of the mason jar snugly, and through it was drilled 2 holes for air supply, 2 holes for electrodes. the 1" PVC tube is epoxy attached to the lid as well, extending into the jar. thick aluminum gutter guard was wrapped around the out side of this PVC tube, and the smaller mesh was folded into a star shape and fit inside the tube. that was the dielectric barrier and both electrodes. the air supply used no drier, filter or anything else. just a little diaphragm guy we had for an old fish tank.

it would make a decently strong smell of ozone, and clear a room of funky( cat room) smell in less than 10 min :) left for 10 or 15 min to clear it was nice in there. I was looking through my lab notebooks last night and came across the page I laid out for the project, always love it when the finished product look very close the the drawings. I may try to put it in the improvised labware thread when I get a chance.

over this last week I made a 12KV full wave rectifier for the oil burner transformer(OBT) from microwave oven scraps. fun lill project. one 2" domed PVC end-cap, 4- holes drilled, 4- 12KV diodes, 4- bolts and 8- nuts. really friggin simple. it allowed me to use the center-tapped OBT to power the voltage trippler I found last year!!!( needed DC) big angry sparks + magnets = small plasma disk. I spent 2 nights trying just to get the disk without the DC-HV output or trippler, got frustrated and built the rectifier, and then a couple more nights playing around after I got it built and all going. very fun and rewarding series of projects and decent notes taken. ozone was unmistakeable when the tantalum electrodes were too far apart, much less so when actively arcing. DC or AC- HV mattered not. in the end I got over an inch sparks continuous, not much over 1" but better than 1/4" or so at the beginning.

as always respect your projects, plan n play safe = survive to do more experiments.

edited for spelling

[Edited on 14-4-2015 by violet sin]

Marvin - 14-4-2015 at 08:52

It's generally held that the best mechanism for nitric oxides is thermal in the arc and the best one for ozone avoids thermal decomposition as much as possible by maintaining a low density discharge. It will have been covered before I expect.

Jimmy's description is one version of a dielectric barrier discharge, the barrier which prevents the discharge collapsing into an arc blocks DC, it's a capacitor.

Molecular Manipulations - 14-4-2015 at 09:53

Quote: Originally posted by Sulaiman  

but I can't ever remember smelling even a hint of N2O.

does ozone de-sensitise the sense of smell to N2O
or is N2O produced in only negligible quantities?

You keep mentioning nitrous oxide, nitrogen in the lowest oxidation state bonded to oxygen. This gas has almost no odor (slightly sweet), and is colorless. I don't think nitrous can be made from an arc, and you wouldn't be able to detect it anyway. Also, it would almost undoubtedly react with ozone:
N2O + O3 → N2 + 2O2.
Higher oxidation states of nitrogen however can form in an electric discharge under certain conditions. I find the smell of ozone to be way stronger than nitrogen (IV) oxide, which is probably the reason it's hard to detect.
Also, this may be irrelevant, but ozone also oxidizes nitrogen (IV) oxide to nitrogen (V) oxide (nitric acid anhydride):
N2O4 + O3 → N2O5 + O2.

violet sin - 14-4-2015 at 17:10

@ Marvin

how does AC or DC matter in that regard though? both can be kept in arcing or glow discharge modes... based on dielectric( or none) and/or electrode spacing. at least from my experiments. the O3 mason jar-PVC-aluminum mesh thing I mentioned works great with a beautiful purple glow, from an AC source( I will attach my DC transformer to it minus trippler next time I'm home) there are numerous DC ozonisers as well. quick google shows both. though a DC arc does have one electrode hotter than the other, well described in a MIG/TIG welding book I have when covering the subject of electrode polarization. yet just the other day I was looking up nitrogen fixation patents and AC or DC wasn't really important as the electrode tip wasn't doing the work( like in welding), the arc was. that patent clearly stated either AC/DC in a magnetic field was fine... having trouble finding it in the search history... was last month, geeze, seemed like 3 days ago.

"... A process for producing NO gas from a feed flow of air or oxygen enriched air, by means of moving an electric arc through the air flow by using a magnetic field and AC or DC currents, in a reactor, wherein a pressure lower than 1 bar is applied, wherein the temperature in the exited arc is adjusted to be within the range of 3000 to 5000 Kelvin, and wherein the air flow is quenched by applying a spray of fine water droplets upstream or just downstream the arc, excess air feed or bypassed air to obtain a stable NO-containing plasma having a temperature below 2000 Kelvin.... "

so it would seem that neither O3 nor NO2 are entirely dependent on a specific AC or DC current supply. various processes have been chosen by big industry of course. but on a hobby scale I don't see a problem here.
-Violet Sin-
edited for wording

[Edited on 15-4-2015 by violet sin]

Marvin - 15-4-2015 at 16:00

A dielectric barrier discharge cannot be done with DC.

macckone - 16-4-2015 at 09:19

Quote: Originally posted by Marvin  
A dielectric barrier discharge cannot be done with DC.

That is only true with a perfect insulator and true dc.
In the real world there is sufficient leakage and pulsation on diodes
that you don't have to remove the diode from the flyback.
It isn't as good as ac but it works.

Jimmymajesty - 19-4-2015 at 07:25

For those who want to build an ozone generator with flyback, the oldest the tv is the better, in the old setups the rectifier is a physically aseparate unit while in the new ones they are built together with the transformer.

Make a HV capacitor from foils and such, connect one terminal, get the second close and if you get a constant arc, the transformer is able to generate "useful" amount of ozone.

Based on last days' experience I do not really know how much is "useful" or that you can use it to oxidize alcohols at all. In theory you can, in practice I am not so sure...