making potassium (per) chlorate

[WSM]

The Electrodes

 

After some research and discussions with a good friend (and fellow electrochemist), I've determined which size anode to use for the high temperature experimental cell. I've decided to use a larger anode that would run up to 126 Amperes (at 0.3 A / cm²).

 

The actual current demand will depend on the temperature the cell liquor is running at (the goal is between 105^oC and 110^oC). The power supply will be set to run in constant current mode, at whichever amperage maintains the proper temperature in the cell. I'm hoping the temperature will be at least somewhat stable with the fixed current input.

 

The cell material is PVDF (Kynar) which one source listed as rated to 121^oC, but another source is claiming it's serviceable to 150^oC without any compromise to its characteristics. Either will work but higher thermal stability is always preferred.

 

The initial electrode configuration will be a single (MMO mesh) anode surrounded by two CP titanium cathode plates, bonded to each other with CP titanium strips; with a gap between the positive and negative poles of about a quarter inch (~6.4 mm), for adequate fluid flow.

 

I'll try to make progress on building the electrodes today, and mounting them in the bottom plate of the cell tank. If I'm able to progress far enough, I'll reassemble the tank and seal it up for a water-test to be sure it's watertight.

 

After all that, the system can be set up to run.

 

WSM

Edited December 30, 2016 by WSM

[greenlight]

Sorry for the late reply.

Yes, it is a D85 3051.

Thankyou very much for the help WSM.

I can put it together without any worry now.

Edited December 28, 2016 by greenlight

[WSM]

Sorry for the late reply.

Yes, it is a D85 3051.

Thankyou very much for the help WSM.

I can put it together without any worry now.

 

Awesome, good luck.

 

WSM

[WSM]

The initial electrode configuration will be a single (MMO mesh) anode surrounded by two CP titanium cathode plates, bonded to each other with CP titanium strips; with a gap between the positive and negative poles of about a quarter inch (~6.4 mm), for adequate fluid flow.

I'll try to make progress on building the electrodes today, and mounting them in the bottom plate of the cell tank. If I'm able to progress far enough, I'll reassemble the tank and seal it up for a water-test to be sure it's watertight.

 

When I started putting the electrodes together (Today, not yesterday), I chose to make the gap 1/2" rather than 1/4" for convenience in assembly by spot welding. The size of the anode is 4.875" x 6.750", and the current demand at 0.3 A / cm² will be 127 Amps!!!

 

I think it might run at a lower current level and still get to 105^o-110^oC. We'll see when it gets running (the patent suggests a current load at 0.15 A / cm², which would make the electrodes in the system last much longer).

 

 

I made good progress but ran out of steam by early evening, so I'll continue when the weather cooperates. I have a lot more drilling and tapping of the end plates to do before I can reassemble the tank. I'll try to take more photos to share as I get further along.

 

I'll see if more can be done on the 31^st, because I have other things I need to do tomorrow.

 

WSM

Edited January 2, 2017 by WSM

[pyrojig]

Wow cool , that's some big electrodes !!! Love the engineering!!!! How do you propose opening the cell for servicing? If you run that hot won't the Naclo3 drop out as crystals and potentially bridge the electrodes ?

[WSM]

Wow cool , that's some big electrodes !!! Love the engineering!!!! How do you propose opening the cell for servicing? If you run that hot won't the Naclo3 drop out as crystals and potentially bridge the electrodes ?

 

Yes, it's a departure from the way I've done things in the past and much larger electrodes.

 

The way it's opened is by disassembly from the top, but only after the cell is emptied by draining it into a holding tank.

 

The patent I'm following says that at the boiling point of the electrolyte (between 105^oC and 110^oC) the chlorate stays in solution, but crystals will drop out when two things happen:

1. the fluid level in the cell drops to 50% of the starting level (raising the NaClO₃ concentration), and
2. the electrolyte temperature is lowered to 45^oC

Actually, I plan to lower the harvested electrolyte to ambient temperatures rather than at as high as 45^oC; so I expect higher yields.

 

I'm thinking of designing the system so I don't need to open the cell very often. I think I can move fluids around by using chemical handling pumps, or gravity fed with compatible valves.

 

A lot of insulation will probably be needed to keep temperatures up until the electrolyte is delivered to a crystallization chamber (CC) where the sodium chlorate can drop out and be harvested. If things don't cool enough in the CC on its own, I may add an air cooled heat exchanger with a fan and radiator, as sometimes used for cooling computer circuits.

 

WSM

 

Edit: the system, as I'm beginning to envision it, will easily lend itself to being a continuous system; making NaClO₃ constantly, as long as it's fed with purified brine and current.

Edited January 2, 2017 by WSM

[WSM]

I realized I needed some more PVDF fittings, so I placed an order this morning for them.

 

Swede had done a lot of work in the short time he posted here, and listed several developments and discoveries that furthered our ability to make oxidizers on a small scale. Buried deep in his postings and blogs are some sources for PVDF (Kynar) fittings which greatly help when handling such corrosive liquids as the mother liquor in our chlorate cells. Two sources are U.S.Plastics (http://www.usplastic.com/), who has a large listing (& periodic catalog sent out) and excellent customer service; and Ozone Solutions (http://www.ozonesolutions.com/products/Ozone-Compatible-Fittings), who carry excellent fittings at good prices.

 

I'm passing on these sources for the benefit of those desiring to make chlorate cells with hardware designed to handle the harsh chemicals without breaking down. I use them both, but I must add that Ozone Solutions has a much more limited variety of fittings, BUT their prices are a bit lower, they offer quantity breaks sooner and offer free shipping (to the US and Canada) if the order totals over $50 US (which isn't hard to do when you really get into this)!

 

All that said, I recommend Ozone Solutions to the Amateur Electrochemists who reside in the United States and Canada !

 

WSM

Edited December 30, 2016 by WSM

[PTFE]

Hey wsm,

im pretty buisy atm so i will reply later in a more entire way.

For cooling its in some ways difficult.

If you place cooling spirals (PTFE/titanium) it wil be pretty expensive.

also you have to take care about crystals forming at the cool parts, which is not a big problem isnce you've got your electrodes at he bottom and also a very large tank.

The biggest problem is, if you use PTFE it will be difficult to hold it in place when it gets hot and titanium will be difficult to bend without creasing i think.

 

I found out, that it brings a nice cooling effect if you pump in cool air via an aquarium pump or similar.

It also brings the advantage of an better circulation.

 

i wish you a nice new years eve,

ptfe

[WSM]

Hey wsm,

im pretty buisy atm so i will reply later in a more entire way.

For cooling its in some ways difficult.

If you place cooling spirals (PTFE/titanium) it wil be pretty expensive.

also you have to take care about crystals forming at the cool parts, which is not a big problem isnce you've got your electrodes at he bottom and also a very large tank.

The biggest problem is, if you use PTFE it will be difficult to hold it in place when it gets hot and titanium will be difficult to bend without creasing i think.

I found out, that it brings a nice cooling effect if you pump in cool air via an aquarium pump or similar.

It also brings the advantage of an better circulation.

i wish you a nice new years eve,

ptfe

 

Thanks, PTFE. Happy New Year (Sylvester) to you too.

 

I have many other steps to take before I tackle the cooling problem. First is to finish building the cell, then assemble the whole system, charge it with recycled electrolyte and fresh brine, and then do a trial run to begin dialing the parameters in.

 

There's a lot of work ahead but I look forward to it.

 

WSM

[greenlight]

I forgot to say before as well:

That setup you are constructing sounds awesome WSM. I can't wait to see the results.

Those are some huge electrodes!!!

Edited December 31, 2016 by greenlight

[WSM]

I forgot to say before as well:

1) That setup you are constructing sounds awesome WSM.

2) I can't wait to see the results.

3) Those are some huge electrodes!!!

 

1) Thanks, greenlight.

 

2) Me too.

 

3) Yes, they are.

 

WSM

Edited December 31, 2016 by WSM

[WSM]

Happy New Year!

 

I need to slow down the progress on my experiment till some material that I ordered arrives, but I'm planning more of the details of the cell till then. I'm looking forward to getting it built and ready to run.

 

I'll post the details (and more photos) as it comes together and begins to run.

 

WSM

Edited January 2, 2017 by WSM

[greenlight]

I went out and brough the wiring to connect the shunt and meter to my cell and ended up buying the same thick wiring that I used ro connect the electrodes to the cell from the power supply minus the meter.

Should I be using smaller wiring or is it better to use the same diameter through the whole setup?

Edited January 2, 2017 by greenlight

[WSM]

I went out and brough the wiring to connect the shunt and meter to my cell and ended up buying the same thick wiring that I used ro connect the electrodes to the cell from the power supply minus the meter.

Should I be using smaller wiring or is it better to use the same diameter through the whole setup?

 

Using heavier (than required) wire shouldn't hurt the setup. Economically, it makes more sense to use finer wire for the sensing portion of the meter circuit and heavier wire for the current carrying portion.

 

Looking at a cross section of any electrical wire (I use copper almost exclusively), what you'll see is:

• the thicker the wire, the heavier the current carrying capability
• the thicker the insulation the higher the voltage rating

So, a large size conductor with thinner insulation is for low voltage, high current applications. Inversely, Fine wire with thick insulation is for high voltage, low current applications.

 

There is a lot of variety in copper conductors, and the proper choice for any application usually means getting enough conductivity to do the job without excessive heating, while costing no more than is required to accomplish it. Also, there are physical aspects to consider, but I'll leave that discussion for another time.

 

WSM

Edited January 2, 2017 by WSM

[WSM]

Today, I was able to finish the bottom plate of the cell and mount the electrodes to it as well as plug two auxiliary holes. I also treated the MMO anode in hydrochloric acid for an hour to remove some brown smut from it.

 

After assembling the electrodes in the base plate and adding (stabilizing) Teflon spacers between them, I reassembled the cell with the Viton gaskets in place. I also cut a piece of thin Teflon sheet to cover the steel base of the cell assembly, which I'll install later in hopes of protecting the steel from any electrolyte which may escape.

 

I still need to populate the top plate of the cell with ports and fittings, but that's a job for another day.

 

The bottom plate with the electrode assembly mounted.

 

As always, there's more to come...

 

WSM

[WSM]

Here's a photo of the electrodes before the Teflon stabilizing spacers were added:



This view is looking down from the top. The PVDF pipe (main tank body) slides down over the electrodes and is surrounded by the PVC pipes covering the threaded tie rods. The main tank body is clamped between the top and bottom PVDF plates, with Viton gaskets sealing the gaps between them.

I'll show more later.

WSM

Edited January 5, 2017 by WSM

[greenlight]

Looking good WSM...

and thankyou for your answer.

I will use the same diameter cable for the whole setup

Edited January 3, 2017 by greenlight

[WSM]

Looking good WSM...

and thankyou for your answer.

I will use the same diameter cable for the whole setup

 

It's beginning to come together. It's taking time because part of my work is outdoors and we've been having rainy weather more often lately. We'll see how soon I can get the system completed and running.

 

You're welcome. I hope everything works out for you.

 

WSM

[greenlight]

Good luck to you too.

We have the opposite problem here. Too hot to do any work in the day as my workshop is a large metal shed and doesn't cool down til late at night.

Will update when it is all wired together.

Edited January 3, 2017 by greenlight

[WSM]

Good luck to you too.

We have the opposite problem here. Too hot to do any work in the day as my workshop is a large metal shed and doesn't cool down til late at night.

Will update when it is all wired together.

 

What part of the world are you in, greenlight?

 

WSM

[greenlight]

Australia WSM.

[WSM]

Australia WSM.

G'day.

 

Yeah, it's probably too hot during the day there (this time of year anyway).

 

Which territory? I have a cousin who lives in Queensland, if I'm not mistaken.

 

WSM

Edited January 4, 2017 by WSM

[greenlight]

Yeah its 42 degrees C during the day here at the moment.

Its a struggle to store chems in summer and I have to store stars and other compositions in a seperate cool area.

The nights are nice though.

 

I will message you location.

[WSM]

Yeah its 42 degrees C during the day here at the moment.

Its a struggle to store chems in summer and I have to store stars and other compositions in a seperate cool area.

The nights are nice though.

I will message you location.

That sounds like a dry area. Drying stars must be easy. I suppose using your workshop at night during the Summer would be best.

 

WSM

Edited January 5, 2017 by WSM

[WSM]

I mentioned the PTFE (Teflon) sheet to cover the steel base of the new experimental cell. Years ago, a kind friend gave me several feet of thin, white Teflon sheet in a small roll, for use to cut stars on and easy cleanup afterward. This material is roughly one foot wide and several feet long by about 0.030" thick.

 

A couple days ago, I cut a piece of it just long enough to cover the top of the steel base plate (to protect it from the corrosive effects of the electrolyte). The plan is to disassemble the complete cell assembly, cut matching holes in the Teflon sheet, place it over the black steel plate and reassemble the whole arrangement.

 

I also plan to cover the exposed stainless threaded rod under the cell and above the base plate, to protect the tubing and hardware from the sharp threads of the all-thread rods.

 

I still need to drill and tap holes in the PVDF top plate of the cell for compatible fittings and ports required for the proper operation of this cell arrangement.

 

The weather isn't cooperating at the moment, but hopefully the weekend will afford me the opportunity to make more progress on this project.

 

WSM

Edited January 5, 2017 by WSM