making potassium (per) chlorate

[juicebox1155]

Cool idea, will definitely keep up with this one!

[WSM]

In the afternoon of the day after I started the sodium chlorate cell, I saw that the power supply had shut down. It must not have been long because everything was still quite warm (about 50^oC), and when the power supply had cooled enough, it functioned normally. I think the thermal cutoff in the power supply caused the problem. It's likely that the power supply is probably overheating because of the heavy load plus the little fan in it isn't able to draw enough airflow to keep it cool enough.

 

I think I could either place a small computer fan near it to force more air across it, or better; replace it with a stout, large power supply I bought years ago with an output of 5 Vdc and 60 Amps.

 

I shut the system down, removed the lid and electrodes plus covered the cell to keep debris and contaminants out of the electrolyte.

 

Also, something several members here suggested, makes me consider re-plumbing the cell to pump the hot electrolyte through a salt crystal reservoir and back into the cell; recharging the electrolyte with chloride as it's consumed in the cell. The reason is the chloride concentration doesn't produce enough chlorate to make a saturated chlorate solution. BUT, if we keep the chloride level high enough the chlorate levels WILL eventually become saturated and additional chloride will cause the chlorate to begin to drop out of solution, similar to the way potassium chlorate crystals drop out of saturated electrolyte as it's formed.

 

I'm formulating a system to try this theory, but in a way where I can alter the fluid flow, at will; and control the functioning of the cell manually.

 

I'll add more (plus photographs), later...

 

WSM

Edited May 21, 2016 by WSM

[schroedinger]

Well i think adding chloride by pumping the liquor throug fresh chloride could be a really good thing, since your cell will be hotter a the top, then on the bottom. If everything gets setup right, you maybe are able to adjust the cell in a way that the chlorate precipates out at the bottom.

[Arthur]

To extract sodium chlorate you need to electrolyse sodium chloride then cool the product til something ppts out. The trouble is that a fully saturated chloride solution yields a well under saturated chlorate solution so either you have to boil off lots (half!) of the volume or you have to add more chloride and electrolyse again for there to be enough chlorate that it will ppt out on cooling.

 

From here https://en.wikipedia.org/wiki/Solubility_table#S

100ml water will hold

79.6 87.6 95.9 105 115 137 167 184 204 g of sodium chlorate at

0......10....20....30....40...60 .80 . 90 . 100 centigrade

 

SO a solution saturated at 60c with chlorate, should yield 137 - 96 = 41g of chlorate crystals per 100ml. when cooled to 20C

 

To get this concentration of chlorate it will be necessary to keep replenishing the used chloride

[schroedinger]

Well you even won't get the 79.6 g/100ml @0ºC after th3 first run.

[Arthur]

Agreed! 370g of NaCl should dissolve in 1000ml warm water, this will make 370 x 108 / 58 g of chlorate and give 688g chlorate -below the zeroC saturation point. To get chlorate close to hot saturation you need to add another 370g of chloride and electrolyse that as well, this will give about 688 x 2 g of chlorate = 1376g approximately. This approximates to the 60C solubility limit. cooling this to 20C should cause 400g or so to ppt out. Then each batch of 400g chlorate requires that you dissolve 400 x 58 / 108 = 215g of sodium chloride crystals into the liquor and electrolyse the mix completely.

 

You also need to account for the fact that no process is 100% efficient, and that no electrolysis goes to completion simply, expect the electrolysis to only go 80% to completion, so there will always be chloride left in the cell.

[schroedinger]

Yes, and you have to also count in that your cell also shouldn't drop lower then 100 g/l in chloride concentration to avoid extensive anode wear. If you have a conc. Solution of chlorate/chloride, an equilibrium forms depending on the temperature. If i remember right, about 63ºC was the point where so much chlorate is in solution, that you drop below the 100 g/l mark. To manny points to remember.

[WSM]

something several members here suggested, makes me consider re-plumbing the cell to pump the hot electrolyte through a salt crystal reservoir and back into the cell; recharging the electrolyte with chloride as it's consumed in the cell.

 

Today I re-plumbed the cell and added the crystal reservoir. Rather than build the salt chamber from scratch (which I considered), I'm using a filter housing made of PVDF polymer so the whole cell system is PVC, PVDF and PTFE and completely compatible with the mother liquor and additives.

 

The most difficult part was building a frame (which I assembled from aluminum angle) to support the housing, I need to get some glass cloth and wool to keep the salt in place as the electrolyte is pumped through. The plumbing is mainly PVC fittings, including many ball valves, so I can reconfigure the flow to suit the process. The pumps are well suited to this system because they have considerable slippage in case they're running against a closed line (no damage to the pump).

 

As soon as I get the glass cloth to hold the salt back, add the pool salt to the chamber, tie in the Teflon tubing and change the power supply; I'll run the cell again and see how it does without pH control. Later I'll run it with pH control and try to dial it in.

 

This project is getting huge, but it is coming together (I'm almost there). More later...

 

WSM

Edited May 22, 2016 by WSM

[TomasBrod]

Today I re-plumbed the cell and added the crystal reservoir. Rather than build the salt chamber from scratch (which I considered), I'm using a filter housing made of PVDF polymer so the whole cell system is PVC, PVDF and PTFE and completely compatible with the mother liquor and additives.

 

The most difficult part was building a frame (which I assembled from aluminum angle) to support the housing, I need to get some glass cloth and wool to keep the salt in place as the electrolyte is pumped through. The plumbing is mainly PVC fittings, including many ball valves, so I can reconfigure the flow to suit the process. The pumps are well suited to this system because they have considerable slippage in case they're running against a closed line (no damage to the pump).

 

As soon as I get the glass cloth to hold the salt back, add the pool salt to the chamber, tie in the Teflon tubing and change the power supply; I'll run the cell again and see how it does without pH control. Later I'll run it with pH control and try to dial it in.

 

You want to pump your electrolyte trough solid pieces of sodium chloride to re-saturate it with chloride?

If more chloride is going to dissolve in solution rich of chlorate, it can cause (not verified) some chlorate to crystallize. And I am afraid of chlorate build-up in the re-saturation chamber and in the pipes leading back to the cell.

 

 

I saw that the power supply had shut down.

I hope no damage was done to the cell/electrodes/liquid. Did you use plain PC-AT or ATX power supply?

I use AT too, but I modified the feedback signal to enable voltage adjustment 2.5-14V. It's easy to modify TL494 chip based one. Still I blew up one (not based on 494).

Edited May 22, 2016 by TomasBrod

[WSM]

You want to pump your electrolyte trough solid pieces of sodium chloride to re-saturate it with chloride?

If more chloride is going to dissolve in solution rich of chlorate, it can cause (not verified) some chlorate to crystallize. And I am afraid of chlorate build-up in the re-saturation chamber and in the pipes leading back to the cell.

I hope no damage was done to the cell/electrodes/liquid. Did you use plain PC-AT or ATX power supply?

I use AT too, but I modified the feedback signal to enable voltage adjustment 2.5-14V. It's easy to modify TL494 chip based one. Still I blew up one (not based on 494).

 

The filter housing is positioned above the cell (to one side) and the pump takes the hot electrolyte from the bottom of the cell and pumps it up through the filter housing full of pool salt crystals, and then the electrolyte gravity feeds back into the running cell. Everything is valved and fluid flow can be modified on-the-fly, or shut off altogether.

 

The power supply is like the type (or is the type) that's used for LED displays. It's rated at 5 Vdc and 55 Amps. I have never yet used a modified computer supply or built one from a microwave oven transformer (though I have the ability to do so).

 

I think the weatherization box I built for the power supply, though I used perforated metal on the ends, doesn't allow for sufficient airflow and proper cooling of the supply. It apparently has an automatic thermal cutoff built in, and resets when things cool down sufficiently. I suppose I could add a supplemental high-flow fan to force more air through the housing, but I've decided to use a different supply instead, for now.

 

Thanks for the comments and suggestions. If they don't help me, they may well help someone else, and it's good to see them here.

 

WSM

 

Edit: I don't think too much damage was done to the electrodes or electrolyte (the cell housing is impervious to the contents; the beauty of PVC in this application). I removed them from the cell and set them aside to dry, till I can put it back together. Nice catch, by the way.

Edited May 23, 2016 by WSM

[WSM]

As I said earlier, I took the time to re-plumb the cell side of my experimental setup.

The beauty of the sodium chlorate system I'm building is it takes full advantage of the solubility of sodium salts and the ability to move things around with valves and pumps.

I've designed it for maximum versatility, with two surplus Iwaki magnetically coupled chemical pumps, and numerous threaded PVC ball valves (eleven, so far). I've used threaded PVC fittings for a great deal of the plumbing, plus flexible clear vinyl tubing for the brine side and clear PTFE (Teflon) tubing for the cell side, and PVDF (Kynar) compression fittings for the Teflon tubing attachment points.

As an experimental setup, I've planned for the ability to modify the configuration and flow paths as needed, even on-the-fly, if required or desired.

We'll see how this works out as the experiment continues...

WSM

Edit: the filter housing connecting tubing isn't landed yet, until glass filter pads are installed and the salt is placed inside. I also have to put the replacement power supply in service and the cell will be ready to run again, once everything is buttoned up.

Edited May 22, 2016 by WSM

[WSM]

Rather than build the salt chamber from scratch (which I considered), I'm using a filter housing

 

My first thoughts on the salt crystal chamber was to use a 4" clear PVC, schedule 40 pipe remnant bought years ago, to build a clear salt chamber. It would be nice to see the salt levels as the system runs, but since the filter housing was already there, sitting idle, I chose to save time and apply it to the task, instead. We'll see how this works out.

 

If the pool salt crystals are fine enough, I may be able to put them into the filter housing through a 1/4" NPT port in the lid.

 

Maybe and maybe not. I'm sure it would be best to valve that section out of the flow circuit first (or at least shut the pump down, momentarily while adding salt), then run it again when the port is sealed closed.

 

There are many options and we'll decide as this project develops, which is best for this particular setup.

 

WSM

Edited May 23, 2016 by WSM

[WSM]

I hope no damage was done to the cell/electrodes/liquid. Did you use plain PC-AT or ATX power supply?

I use AT too, but I modified the feedback signal to enable voltage adjustment 2.5-14V. It's easy to modify TL494 chip based one. Still I blew up one (not based on 494).

 

Hi TomasBrod,

 

Can you share the method you used to set up the computer power supply, particularly for voltage adjustment and the use of the TL494 chip. It would probably be best to post it in the electronics section, but I'd love to see it. Thanks.

 

WSM

[Arthur]

For a sodium cell (IMO) you need twice the solubility limit of chloride in there to start being able to pull chlorate crystals out by cooling. SO rather than free supply of chloride, having the same amount of "extra" chloride in the top up system could help, when it's gone it's time to do the next process.

 

You may need to use the electrolysis power supply to keep the reaction tank warm if you will be returning cold extracted liquor back from the crystalliser. The reaction needs to happen at about 40C above your crystallising place so that there is a reasonable precipitation every time

[WSM]

For a sodium cell (IMO) you need twice the solubility limit of chloride in there to start being able to pull chlorate crystals out by cooling. SO rather than free supply of chloride, having the same amount of "extra" chloride in the top up system could help, when it's gone it's time to do the next process.

You may need to use the electrolysis power supply to keep the reaction tank warm if you will be returning cold extracted liquor back from the crystalliser. The reaction needs to happen at about 40C above your crystallising place so that there is a reasonable precipitation every time

 

I've set the sodium experiment up so the cell runs continuously, but the salt chamber is valved so it can either be connected or bypassed when the pump is running; or the valves can all be closed and the cell run alone.

 

The sodium experiment is set up uniquely and not like the continuous potassium chlorate cell. There is only the RC, plus brine tank and now the salt chamber connected (plumbed) to the sodium system (no crystallizer is there). Because everything stays in solution, I've plumbed separate drains for both the brine tank and RC, which can be opened or closed as desired, for moving liquids to other containers which will be carried to crystallization stations or setups elsewhere (I'm still working out the details for my sodium chlorate recovery system).

 

WSM

[WSM]

I haven't decided yet how I plan to recover dry sodium chlorate crystals from my sodium experiment. I've left the system with draining options, but everything is planned around the fluids remaining in liquid form (which can be moved around by pump or gravity).

 

I may yet add in a crystallizer. Arthur suggested in a PM, getting something like a beer cooler which would cool the mother liquor, causing the chlorate harvesting to be accelerated. I like the idea, but haven't worked on implementing anything yet.

 

My main focus at this point is creating the sodium chlorate; recovering and purifying it (making it chloride-free) will be the next hurdle.

 

WSM

Edited May 24, 2016 by WSM

[Arthur]

I have no idea whether the under bar beer cooler available for beer money during a bar refit here is available in your country/county/state (etc) but having a place where chloride low chlorate high liquor can be chilled means having a place where sodium chlorate can be crystallised out. BUT having chilled the liquor getting enough chloride back into solution may demand the IR heating of high current.

 

for example

 

http://www.micro-matic.se/category-cid-7297.html

 

Just the one that google found

Edited May 24, 2016 by Arthur

[WSM]

I have no idea whether the under bar beer cooler available for beer money during a bar refit here is available in your country/county/state (etc) but having a place where chloride low chlorate high liquor can be chilled means having a place where sodium chlorate can be crystallised out. BUT having chilled the liquor getting enough chloride back into solution may demand the IR heating of high current.

There may be so many takers for a surplus beer cooler, that the price could rival a new unit.

 

I'm starting to think a four liter beaker full of chlorate-rich electrolyte, placed in a refrigerator may do the trick. Vacuum filtration would separate the solution from the crystals fairly quickly.

 

The depleted liquor could be dumped into the brine tank, re-saturated with chloride, and used for make-up water.

 

WSM

[WSM]

For that matter, placing the depleted liquor back into the four liter beaker, putting it on a hotplate stirrer and replenishing the chlorides while it heats and stirs there wouldn't be much trouble.

 

Heating to about 50 C, before returning it to the cell should do nicely, I would think.

 

WSM

Edited May 24, 2016 by WSM

[Arthur]

Clearly a refrigeration unit is OTT but the only sodium chlorate that will crystallise out is that between finished saturation and cool saturation, so the bigger the cooling the bigger the yield per cycle.

[WSM]

Clearly a refrigeration unit is OTT but the only sodium chlorate that will crystallise out is that between finished saturation and cool saturation, so the bigger the cooling the bigger the yield per cycle.

Yes, that's the way I see it too. I may be on the hunt for a mini-fridge to dedicate to harvesting my crops of sodium chlorate.

 

Sometimes, people practically give those things away. I'll keep my eyes open for a deal on one.

 

WSM

Edited May 24, 2016 by WSM

[memo]

got the second run done today and the 3rd in the cell, this one looks to be a lot more productive, hoping for around 900 grams. on the 4th run I am going to try just potassium choride and see what comes of that. wsm you are so far ahead of me. I just need to keep plugging along.

 

memo

[WSM]

got the second run done today and the 3rd in the cell, this one looks to be a lot more productive, hoping for around 900 grams. on the 4th run I am going to try just potassium choride and see what comes of that. wsm you are so far ahead of me. I just need to keep plugging along.

memo

 

After the first run, the precursors are established and subsequent runs are producing much more chlorate. The first run spends much of it's energy just making the precursors (hypochlorite, hypochlorous acid and dissolved chlorates), so the first run will drop out little to no chlorate.

 

This is true of both sodium and potassium systems. The potassium system is more fun to watch, because as the chlorate forms, it quickly reaches saturation due to its lower solubility, and the chlorate begins to drop out, looking like snowflakes that float down to the bottom of the cell.

 

If I'm far ahead, it's because I've been traveling this road for so much longer (I've been studying chlorates and perchlorates for roughly 15 years now and I'm in my 60's [time flies when you're having fun]). Also I like to share.

 

You'll get there, just keep at it.

 

WSM

Edited May 25, 2016 by WSM

[memo]

we will be without power today for 5 hours my back up power is only good for a couple of hours, I pulled everything out of the cell. will it be ok ? it only has 20 hours of run time. if there is no problem should I reheat the electrolyte ?

 

memo

[WSM]

I pulled everything out of the cell. will it be ok ?

it only has 20 hours of run time. if there is no problem should I reheat the electrolyte ?

memo

I recommend removing the electrodes, rinsing them with water, dry and store them in a safe place till you can start up again

 

No need to heat the electrolyte, the running cell will come up to temperature, slowly as it runs.

 

At least you got prior warning about the power outage!!!

 

WSM

Edited May 25, 2016 by WSM