making potassium (per) chlorate

[abc159201]

If you read through Swede's blog, the acid injection problem is solved by introducing it slowly, deep UNDER the surface of the electrolyte so the HCl stays in the solution (doing its work), rather than boiling off.

 

Remember, the PVC is not in direct contact with the hot electrolyte, just above it. The temperature the PVC rises to is yet to be determined. The original patent writer used 1" thick plexiglas for a lid, in a similar setup.

 

We'll see how it works in practice, rather than doom it before we try.

 

WSM

 

The lid isn't directly contacting the hot solution for sure,but it contacts hot water vapor.Heating the PVC lid above 82°C isn't that hard at all. After checking wiki,I think plexiglass/PMMA is much sensible since PMMA has higher Tg(between 85 to 165 °C ) But still looking forward to your results

Edited November 20, 2019 by abc159201

[FrankRizzo]

Swede used CPVC, IIRC. It's chlorinated, which reduces breakdown and is also stable at higher temperature.

[WSM]

The lid isn't directly contacting the hot solution for sure,but it contacts hot water vapor.Heating the PVC lid above 82°C isn't that hard at all. After checking wiki,I think plexiglass/PMMA is much sensible since PMMA has higher Tg(between 85 to 165 °C ) But still looking forward to your results

 

 

PVC polymer IS rated to 60 degrees C, but that's at rated pressure and intimate contact with the liquid heat source.

 

My lid is several inches away and the cell is running at 1 atm pressure with an unimpeded outgas flow through a large vent. This means, no direct contact with hot electrolyte and no pressure, so I expect the PVC plate to see minimal impact in this application.

 

CPVC is rated to roughly 90 degrees C, and would probably work reasonably well. PVDF would have been my first choice, but I can't find a large enough piece at a reasonable cost, so that's out. PTFE would be wonderful, but pricey.

 

I have the thick PVC plate on hand, so I'll give it a try and see how (or if) it works.

 

WSM

Edited November 24, 2019 by WSM

[WSM]

Swede used CPVC, IIRC. It's chlorinated, which reduces breakdown and is also stable at higher temperature.

 

Yes he did, and I DO have a sturdy CPVC tank I built several years ago. I plan to keep it in reserve for another project I have in mind.

 

My plan with the borosilicate glass cell, is to try the method proposed in the patent Arthur shared, i.e., run the cell at an average of 110 degrees C to maximize the sodium chlorate cell efficiency plus boil off enough water in the process to naturally concentrate the NaClO3 to where it will drop out of solution when it cools to just room temperature (not 0 degrees, like with a normal system, plus it'll save on refrigeration costs as well). Another advantage of the setup is it'll be recharged with purified brine rather than salt which I'd have to make from my pure brine (saving me several more steps).

 

If you read through the patent, it promises a lot of advantages over the "normal" methods used. I expect it'll produce more sodium chlorate faster, with lower costs and less effort.

 

We'll see...

 

WSM

Edited November 27, 2019 by WSM

[WSM]

PVDF would have been my first choice, but I can't find a large enough piece at a reasonable cost, so that's out.

WSM

 

Well, I just found a large and thick enough piece of PVDF sheet on Ebay and ordered it, so I'll make the high temperature cell's lid of PVDF instead of PVC. As a cell lid, it aught to work very well. We'll see...

 

In a recent study of the characteristics of PVDF, I learned that it won't tolerate high alkalinity, so if in contact with chlor-alkali electrolyte, pH control is HIGHLY recommended. This is good to keep in mind if designing a system incorporating PVDF in direct contact with the mother liquor in an operating cell.

 

How soon I'm able to progress with this research is in question. Sadly, my work schedule and family obligations will not allow me to work on this project until at least mid-January, and on till spring.

 

We'll see how it goes, but work will be VERY time consuming until mid-April.

 

WSM

Edited December 4, 2019 by WSM

[abc159201]

Well, I just found a large and thick enough piece of PVDF sheet on Ebay and ordered it, so I'll make the high temperature cell's lid of PVDF instead of PVC. As a cell lid, it aught to work very well. We'll see...

 

In a recent study of the characteristics of PVDF, I learned that it won't tolerate high alkalinity, so if in contact with chlor-alkali electrolyte, pH control is HIGHLY recommended. This is good to keep in mind if designing a system incorporating PVDF in direct contact with the mother liquor in an operating cell.

 

How soon I'm able to progress with this research is in question. Sadly, my work schedule and family obligations will not allow me to work on this project until at least mid-January, and on till spring.

 

We'll see how it goes, but work will be VERY time consuming until mid-April.

 

WSM

 

Just out of curiosity, can a thick piece of Bakelite inlayed with thin fluoropolymer plate hold? If it can,that should greatly reduce the cost.

[WSM]

Just out of curiosity, can a thick piece of Bakelite inlayed with thin fluoropolymer plate hold? If it can,that should greatly reduce the cost.

 

Possibly. The trick is sealing the Bakelite perfectly from the mother liquor.

 

I agree, if done carefully, it would greatly reduce the cost of the lid.

 

I suppose I'd choose PTFE to protect the Bakelite, rather than lesser fluoropolymers (maybe because I already have some).

 

WSM

Edited December 9, 2019 by WSM

[markx]

Possibly. The trick is sealing the Bakelite perfectly from the mother liquor.

 

I agree, if done carefully, it would greatly reduce the cost of the lid.

 

I suppose I'd choose PTFE to protect the Bakelite, rather than lesser fluoropolymers (maybe because I already have some).

 

WSM

 

Do you have any possibility to machine materials? If so then you can create sealing surfaces and seats around electrode stems and ports that penetrate the lid and ptfe sheet. Then back it up with bakelite or something similar for structural integrity. Actually bakelite seems pretty resistant towards the action of at least gaseous chlorine and TiCl4 vapours, even at high temperatures....can not be sure about the action of cell liqour. Once upon a time I worked with high temperature chlorination reactors (rotary and fluidized bed types) that operated at an excess of 900C. The high temperature cores were made from quartz tubes and the protruding ends were sealed with lids made from bakelite type of material. Granted the reactor ends never saw the scorching temperature of the core, but they went up to 100+C on regular basis. And they worked pretty damn good as far as longevity in these conditions goes. They lasted years of corrosive abuse in chlorine and TiCl4 vapours without any major damage.

[WSM]

Do you have any possibility to machine materials? If so then you can create sealing surfaces and seats around electrode stems and ports that penetrate the lid and ptfe sheet. Then back it up with bakelite or something similar for structural integrity. Actually bakelite seems pretty resistant towards the action of at least gaseous chlorine and TiCl4 vapours, even at high temperatures....can not be sure about the action of cell liqour. Once upon a time I worked with high temperature chlorination reactors (rotary and fluidized bed types) that operated at an excess of 900C. The high temperature cores were made from quartz tubes and the protruding ends were sealed with lids made from bakelite type of material. Granted the reactor ends never saw the scorching temperature of the core, but they went up to 100+C on regular basis. And they worked pretty damn good as far as longevity in these conditions goes. They lasted years of corrosive abuse in chlorine and TiCl4 vapours without any major damage.

 

 

Fascinating, I wonder which Bakelite material was used? I DO have machining capability, but haven't machined much Bakelite.

 

This bears further investigation, and opens other opportunities. I suppose I'd better research the compatibility of phenolic resin to hypochlorite, before pursuing this further.

 

Thanks for the information and suggestion. I'll look into it.

 

WSM

[WSM]

Come to think of it, I HAVE considered other sealing methods on flat surfaces.

 

I've used Viton rubber sheet as flat gaskets to seal cell components when in direct contact with the mother liquor.

 

Viton B holds up very well.

 

WSM

Edited December 9, 2019 by WSM

[WSM]

The reason I mention flat surfaces, is the top of the borosilicate reaction vessel I plan to use is flat with an O-ring groove in it.

 

If I use a flat sheet of a fluoroelastomer like Viton B, I won't even need to add an O-ring to get a good seal on the lid of the cell. This will depend on the lid of thick PVC or PVDF being solidly clamped on the glass cell from the outside, with the Viton gasket in between the lid and the reaction vessel.

 

This may well be the way I go with this experiment. We'll see...

 

WSM

Edited December 14, 2019 by WSM

[Arthur]

Bakelite may not be nice to machine, according to the compounding.

[WSM]

Bakelite may not be nice to machine, according to the compounding.

So if my Bakelite contains nasties, forget about it and go back to plan A.

 

Thanks, Arthur.

 

WSM

Edited December 10, 2019 by WSM

[markx]

So if my Bakelite contains nasties, forget about it and go back to plan A.

 

Thanks, Arthur.

 

WSM

 

It should not be that nasty. If it contains hard glass fibre reinforcement then HSS steel tools will suffer, but carbide makes short work of it. The kind of bakelite we used was pretty easy to machine, although it created a lot of very fine chips and dust that needed to be contained with a vaccum cleaner.

Workhardening chromium containing steels, certain stainless and some Ti alloys are lightyears ahead on the "not so nice to machine" curve

[Arthur]

By nasty to machine read "may contain asbestos" in the UK early bakelites were compounded with 30% asbestos fluff for reinforcing fiber and heat transmission resistance. Obviously this stopped here with the awareness of the hazards of asbestos, New bakelite sheet is asbestos free, but old asbestos stock material could contain asbestos and not be nice to machine due to asbestos loaded dust and turnings.

[markx]

By nasty to machine read "may contain asbestos" in the UK early bakelites were compounded with 30% asbestos fluff for reinforcing fiber and heat transmission resistance. Obviously this stopped here with the awareness of the hazards of asbestos, New bakelite sheet is asbestos free, but old asbestos stock material could contain asbestos and not be nice to machine due to asbestos loaded dust and turnings.

 

Oh, I see.....well that could be viewed as not very nice to machine indeed In case the lid is backed with ptfe sheet, the rigidity providing part could be made from about anything being able to withstand the moderately high temperatures of the cell. Does not have to be bakelite. Even a disk machined from cheap wooden blank could be a viable option to some degree.

[FlipperFuego]

thanks for all the great advice http://freeimagehost.info/i/NvnjCqTNgJ.png

[WSM]

thanks for all the great advice http://freeimagehost.info/i/NvnjCqTNgJ.png

You're welcome.

 

WSM

[Redox]

Hey, I'm doing some research on chlorate cells and I was wondering, if anyone has done any calculations for a continuous process chlorate cell. Most resources tell you that you need a bulk container where the formation of chlorate from hypochlorous acid takes place (normally at pH 6.7), and it needs to be run at high temperatures (60 to 80°C). But has anyone actually calculated what size this vessel must be from the kinetics of hypochlorite decomposition at a given cell amperage and what flow rate to use to prevent hypochlorite saturation in the electrolysis cell?

[WSM]

Hey, I'm doing some research on chlorate cells and I was wondering, if anyone has done any calculations for a continuous process chlorate cell. Most resources tell you that you need a bulk container where the formation of chlorate from hypochlorous acid takes place (normally at pH 6.7), and it needs to be run at high temperatures (60 to 80°C). But has anyone actually calculated what size this vessel must be from the kinetics of hypochlorite decomposition at a given cell amperage and what flow rate to use to prevent hypochlorite saturation in the electrolysis cell?

 

It's my understanding and belief that these electrochemical cells are scalable either up or down if you mind all the physical aspects of chlorate cell design and safety.

 

Of course, the larger the cell, the greater the need for extra controls and forethought in its design and operation.

 

WSM

 

Edit: the optimal pH is more or less 6.7 (slightly acid) and the bulk reaction occurs at this pH when/where the ratio of hypochlorous to hypochlorite ions is about 2:1, according to the researchers I've studied. In any case, cell efficiencies of above 90% aren't possible without active pH control.

 

Plus, without pH control it's difficult to achieve anything much above 50% cell efficiency.

Edited December 29, 2019 by WSM

[WSM]

Hey, I'm doing some research on chlorate cells and I was wondering, if anyone has done any calculations for a continuous process chlorate cell. Most resources tell you that you need a bulk container where the formation of chlorate from hypochlorous acid takes place (normally at pH 6.7), and it needs to be run at high temperatures (60 to 80°C). But has anyone actually calculated what size this vessel must be from the kinetics of hypochlorite decomposition at a given cell amperage and what flow rate to use to prevent hypochlorite saturation in the electrolysis cell?

 

 

Hi Redox,

 

Welcome to the discussion.

 

The "bulk container" you refer to sounds similar to the "bulk reaction" mentioned in literature, as when the pH is optimal for producing chlorate throughout the cell rather than just at the anode. This is based on the ratio of hypochlorous to hypochlorite ions, and not the volume of the cell container. Also, though higher temperatures improve efficiency, the temperature plays a secondary role in the reaction.

 

One must monitor the cell condition and parameters using appropriate sensors to properly gauge any adjustments needed to encourage the bulk reaction in the operating cell.

 

WSM

Edited December 29, 2019 by WSM

[FrankRizzo]

It would be interesting to use a conical vessel with a valve and collection vessel attached at the bottom. Some home beer brewers use tanks like that to collect yeast and protein break material after a fermentation has completed. You could potentially harvest a crop of crystals every few days, and top-up with saturated chlorate while keeping the process running.

 

 

[WSM]

It would be interesting to use a conical vessel with a valve and collection vessel attached at the bottom. Some home beer brewers use tanks like that to collect yeast and protein break material after a fermentation has completed. You could potentially harvest a crop of crystals every few days, and top-up with saturated chlorate while keeping the process running.

 

 

That's an interesting thought.

 

For a potassium chlorate cell, I think it would probably jam with crystals and not operate as planned (I'd love to be proven wrong on this one).

 

For a sodium chlorate cell, I don't know. Since the electrolyte and the products are all liquid, I'm not certain if enough of a density difference between them exists to allow stratification, which would be necessary for such a setup to properly operate.

 

Frank, if you're set up to run such an operation, and willing to give it a try, please let us know how it works.

 

WSM

Edited December 28, 2019 by WSM

[WSM]

On the other hand if, as you mention, you're feeding sodium chlorate electrolyte into a perchlorate cell, to make a continuous perchlorate process; that bears further investigation.

If the densities are different enough, it might work as an intermediary step if not in the active cell. Since the running cell bubbles hydrogen (and some ozone), it might just stir things up too much to allow the needed settling for a separation of different densities in the solution.

We'll have to look into this more carefully.

WSM

Edited December 29, 2019 by WSM

[Andead]

I have finally started running my first perchlorate cell and i cant thank you guys enough !!!

 

Making chlorate has always been a great challenge for the past year and now i can do it at ease thanks to you guys.

 

Now i shall be looking to make potassium and ammonium perchlorate

 

As i have previously stated i cant thank you guys enough for the vast amounts of information and time you have dedicated to this topic.

 

Andead