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Author: Subject: Woelens Chlorate cell
Little_Ghost_again
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[*] posted on 19-1-2016 at 13:26
Woelens Chlorate cell


Hi,

I have a question regarding the excellent write up on the potassium chlorate cell.
When the chloride is depleted and much oxygen is evolved, is there any effect regarding the current?

The other questions relates to a depleted cell and conservation of the electrodes.

Due to the nature of life etc there are many times I would not be able to check on a cell for upto 12 hours, I would like to build a simple controller that would detect when a cell had reached completion.

As I understand it switching off the PSU is not advised if the electrodes are to be left in the solution, however its also not a great idea to have them producing shed loads of Oxygen.
So what would be a safe voltage or current to apply to the electrodes until such times as a cell could be topped up?

The controller I have in mind is just a simple analogue one that would detect current and the restrict voltage or current to lowest possible level in order to protect the electrodes and produce the least amount of oxygen




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Little_Ghost_again
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[*] posted on 19-1-2016 at 14:29


Anyway can anyone gibe me an idea what voltage to drop the electrodes too in order to protect them, they are MMO and I would like to keep them in as good a condition as I can.

[Edited on 1-20-2016 by zts16]




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[*] posted on 19-1-2016 at 16:03


I'm no expert, but it'd make sense to me if the current did decrease—a decrease in ions in solution=a decrease in amount of electrons flowing between the electrodes.



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[*] posted on 19-1-2016 at 17:46


What about a simple voltage comparator using something like a wall-wart of appropriate voltage?
Basically shutting off the cell when it went off track. I think as long as the electrodes had *some* applied energy, it will deter the "left unplugged in sol." Issue. If you dumped the wallwart power across the electrodes after main power supply was shut down, you'd be left with an appropriate voltage and minimal amperage. Maybe a 150ma or so if you found a convieniet size. Slow the degredation and hard chewing untill you get back to it.

But it doesn't sound super easy to set up. B/c you'd need some flip-flop switching. Once main PSU is triggered off, you then have to reroute your set voltage supply to cover electrodes. Honestly there are WAY WAY smarter electronics guys around. I only learn what I have to in order to complete a project. (If only it was like the matrix... Downloading.. ... ... Brilliant)

It's been a while since I've 're-read the cell dynamics... But as I remember it, when free chloride is low and chlorate is high, it sought to eat the electrodes. Busy with side and reverse reactions that made for horrible effiency on top of the electrode damage.

I don't even have my lap top here on the coast, so I will have to look up the resources again :(

[Edited on 1-20-2016 by zts16]
Ahhh I've been edited!!! Ahhh, j/k it's all good, carry on ;)

[Edited on 20-1-2016 by violet sin]
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Little_Ghost_again
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[*] posted on 19-1-2016 at 18:13


Quote: Originally posted by Velzee  
I'm no expert, but it'd make sense to me if the current did decrease—a decrease in ions in solution=a decrease in amount of electrons flowing between the electrodes.


I wasnt sure, the quote from Woelens site say this on the 3rd run

"After approximately 20 hours quite suddenly a lot of gas was produced at the anode. In one hour the situation changed from hardly any gas production to a lot of gas production at the anode. The gas is not chlorine (no smell), it hence is oxygen."

I am inclined to agree with you but probably I should just use carbon rods as a trial and see what happens to the current.

The more important question is what level of voltage would protect the electrodes on cell depletion and yet keep the oxygen level low?

I was thinking something like a opamp circuit and limit the volts to 0.7, or limit current to 50mA.

As MMO is hard to get here I treat my MMO electrodes like platinum lol. Actually its a sodium chlorate cell I am building first.

I was going to get fancy with a micro but feel like using good old analogue chips




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Little_Ghost_again
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[*] posted on 19-1-2016 at 18:18


Quote: Originally posted by violet sin  
What about a simple voltage comparator using something like a wall-wart of appropriate voltage?
Basically shutting off the cell when it went off track. I think as long as the electrodes had *some* applied energy, it will deter the "left unplugged in sol." Issue. If you dumped the wallwart power across the electrodes after main power supply was shut down, you'd be left with an appropriate voltage and minimal amperage. Maybe a 150ma or so if you found a convieniet size. Slow the degredation and hard chewing untill you get back to it.

But it doesn't sound super easy to set up. B/c you'd need some flip-flop switching. Once main PSU is triggered off, you then have to reroute your set voltage supply to cover electrodes. Honestly there are WAY WAY smarter electronics guys around. I only learn what I have to in order to complete a project. (If only it was like the matrix... Downloading.. ... ... Brilliant)

It's been a while since I've 're-read the cell dynamics... But as I remember it, when free chloride is low and chlorate is high, it sought to eat the electrodes. Busy with side and reverse reactions that made for horrible effiency on top of the electrode damage.

I don't even have my lap top here on the coast, so I will have to look up the resources again :(


sorry you posted as I did!

The electronics are pretty simple, basicaly a opamp that can be used to set voltage via a ten turn pot and a bypass transistor or more likely a MOSFET, then a comparator circuit to monitor the current and voltage.

I might add a decade counter so after say 5 triggers the comparator simple triggers another opamp control circuit that delivers low voltage or current.

That side of it I havnt decided yet and is the easy bit for me, the hard bit is the chemistry :D

[Edited on 1-20-2016 by zts16]




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19-1-2016 at 21:33
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[*] posted on 19-1-2016 at 21:36


Don't mind the prunes and edits, I was just removing the off-topic argument about troll-feeding... carry on



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Little_Ghost_again
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[*] posted on 19-1-2016 at 22:16


Long day today last 2 prelims, if I get home and feel like it I might draw up a circuit, I have been given a neat one for 0.7V using an opamp, it was ment for somthing else but will fit this just fine



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