making potassium (per) chlorate

[Simoski]

I find the plastic used to develop x-rays onto is very inert in a chlorate cell, I will use that and test when I get home in the new year

[WSM]

Happy New Year.

 

Progress on my workshop is coming along nicely. It's good to have a place indoors for my tools and project materials. I'll write more about my research when I settle in and continue my experiments.

 

WSM

[PTFE]

I got my plans reconsidered and i will use ti rods for the connections through the Lid for easy sealing.

 

 

[WSM]

I got my plans reconsidered and i will use ti rods for the connections through the Lid for easy sealing.

 

300A 20L.JPG

 

Be sure the titanium is CP grade. Alloys don't work as well.

 

Nice drawings.

 

WSM

[PTFE]

Be sure the titanium is CP grade. Alloys don't work as well.

 

Nice drawings.

 

WSM

Thank you

I'll only use Ti Gr. 2 since i've read in this thread that Grade 3-5 will not work well.

 

first i thought about Brass for the Connection-Bushing on top of the Cell but with Titanium i will be on the save side.

I'm just concerned about the voltage drop through all connections. But we'll see

Later in a full documentary i will give you all details about that too.

[MrB]

Looking at the drawing, i realized that i was thinking about a somewhat different design then what you are working with. I was thinking along the lines of the first image, where the anode cathode pairs are connected in series, rather then parallel. At this point i can, well to some extent, understand why you are going for a more then average A PSU.

With the cells in series you'd need more voltage, but less A, with them in parallel, you'll need a bunch of A, but not much voltage.

 

Not sure you'd need 300A, that would be at the very top of what MMO is suggested to be run at, but 200A would seem kinda ok, for a power density of 200mA / square cm. Still enough to weld with, so i suppose it doesn't really matter. Just make sure you leave yourself some room to fiddle with the distances between the anode / cathode setups, since it will be distance & voltage determining the current, and you might not want to have to turn the voltage up to eleven, just to get the current density you are shooting for... You probably already thought about it, but i thought i'd steal captain obvious hat n' shield for a moment there ;- )

[PTFE]

Looking at the drawing, i realized that i was thinking about a somewhat different design then what you are working with. I was thinking along the lines of the first image, where the anode cathode pairs are connected in series, rather then parallel. At this point i can, well to some extent, understand why you are going for a more then average A PSU.

With the cells in series you'd need more voltage, but less A, with them in parallel, you'll need a bunch of A, but not much voltage.

 

Hey Mr.B Im not sure, what picture you are talking about.

The 300A Cell is planned to run with 4 Anodes (1mm substrate) in parallel (4*(9cm*40cm)=1440cm² and both sides of the anodes give 2880cm² in total.(all dimensions in the drawing)

If you like to run 200ma/cm² i have to turn up to 570Amps which would be much more overkill than 300A

With other words this block of electrodes could handle 865Amps without damaging the coating

 

The only thing i worry about: If the current density is around 100mA/cm², is there a significant loss in effiziency?

Also im not 100% sure, if 360mm²Ti ((1mm*90mm)*4) on a lenght of 400mm is enough diameter to handle 300Amps without significant voltage drop from top to the bottom of the Anodes (which makes 800 Amps incredibly hard to handle without the use of immpractical and expensive Titanium Bars to connect the Electrodes) Also the Temperature would be a huge problem.

 

Another thing that comes in mind when handling large cells with high currents.

Those cells have to be PH controled unless you have wasts of energy and you have to treat the chlorine in some way.

Also the ventilation gets more important.

Edited January 2, 2018 by PTFE

[MrB]

Hey Mr.B Im not sure, what picture you are talking about.

The 300A Cell is planned to run with 4 Anodes (1mm substrate) in parallel (4*(9cm*40cm)=1440cm² and both sides of the anodes give 2880cm² in total.(all dimensions in the drawing)

If you like to run 200ma/cm² i have to turn up to 570Amps which would be much more overkill than 300A

With other words this block of electrodes could handle 865Amps without damaging the coating

 

The only thing i worry about: If the current density is around 100mA/cm², is there a significant loss in effiziency?

Also im not 100% sure, if 360mm²Ti ((1mm*90mm)*4) on a lenght of 400mm is enough diameter to handle 300Amps without significant voltage drop from top to the bottom of the Anodes (which makes 800 Amps incredibly hard to handle without the use of immpractical and expensive Titanium Bars to connect the Electrodes) Also the Temperature would be a huge problem.

 

Another thing that comes in mind when handling large cells with high currents.

Those cells have to be PH controled unless you have wasts of energy and you have to treat the chlorine in some way.

Also the ventilation gets more important.

 

This picture, which, is irrelevant at this point :- )

 

xx.JPG

 

maybe i'll try it out in a very small scale 5x 50ml or so

 

I did the math, but only accounted for one side. Silly me.

 

If the current density is low, you do lose efficiency, but i suspect you will still be OK at 100mA.

 

Speaking of 300A over the skinny Ti strip... I think you'll be fine. If it starts glowing i was wrong, and you probably should unplug it.

[WSM]

Thank you

I'll only use Ti Gr. 2 since i've read in this thread that Grade 3-5 will not work well.

first i thought about Brass for the Connection-Bushing on top of the Cell but with Titanium i will be on the save side.

I'm just concerned about the voltage drop through all connections. But we'll see

Later in a full documentary i will give you all details about that too.

Grades 1-4 plus a few others are CP (commercially pure) and suitable for use in chlor-alkali cells (so long as current flows).

 

I look forward to reading about your progress.

 

WSM

[Arthur]

Titanium has a much lower electrical conductivity than copper so calculate CSA for copper (there are tables) and multiply by at least 10 for a Ti conductor. Salt creep is a permanent problem where the electrode hangers penetrate the cell lid, keeping the area easy to clean will be a great help.

 

The Microwave Oven Transformer has been rewound and used to spot weld Ti (and DSA/MMO ) so you may save lots of bolts or rivets, threads are hard to find in CP1 and CP2 Ti stock.

[WSM]

Titanium has a much lower electrical conductivity than copper so calculate CSA for copper (there are tables) and multiply by at least 10 for a Ti conductor. Salt creep is a permanent problem where the electrode hangers penetrate the cell lid, keeping the area easy to clean will be a great help.

The Microwave Oven Transformer has been rewound and used to spot weld Ti (and DSA/MMO ) so you may save lots of bolts or rivets, threads are hard to find in CP1 and CP2 Ti stock.

 

The list I have for the conductivity of metals compares many of them to copper.

 

If copper is listed as having a conductivity of 100, then titanium is 3.1 by comparison!

 

Titanium is still conductive, even if it's so much less conductive than copper.

 

WSM

Edited January 3, 2018 by WSM

[WSM]

Titanium has a much lower electrical conductivity than copper so calculate CSA for copper (there are tables) and multiply by at least 10 for a Ti conductor. Salt creep is a permanent problem where the electrode hangers penetrate the cell lid, keeping the area easy to clean will be a great help.

The Microwave Oven Transformer has been rewound and used to spot weld Ti (and DSA/MMO ) so you may save lots of bolts or rivets, threads are hard to find in CP1 and CP2 Ti stock.

 

One person here, a few years ago, used titanium wire to (loosely) "stitch" together the electrodes to their power leads, for use in the electrolyte. I wondered about the effectiveness of such an approach but research into this method agreed with the feasibility of it. The report I read suggested that even if the contact between the parts wasn't particularly solid, that the electrical conductivity of the electrolyte would allow it to work.

 

As for riveting, I have a hand rivet setter for 1/8" (~3mm) rivets, and purchased a length of 1/8" CP titanium rod to form my own rivets from. I haven't made any yet, but I'm confident (in the tool and my ability to use it) that it will work well.

 

As for my spot welder, the first one (Harbor Freight model, made in Armenia) has a failed switch which I plan to repair at some point. In the mean time, I bought a new one on eBay (Made in China) which works better than the HF model and even came with extra electrode tips! The Chinese model costs less than the HF unit as well, runs quieter, heats faster and I'm quite pleased with it.

 

WSM

 

Edit: If you have the tools and skills, I suppose that CP titanium screws and nuts could be fabricated in a home workshop as well. I never bothered, since spot welding (more expensive, but worth it) has served my needs so far.

Edited January 7, 2018 by WSM

[PTFE]

 

One person here, a few years ago, used titanium wire to (loosely) "stitch" together the electrodes to their power leads, for use in the electrolyte. I wondered about the effectiveness of such an approach but research into this method agreed with the feasibility of it. The report I read suggested that even if the contact between the parts wasn't particularly solid, that the electrical conductivity of the electrolyte would allow it to work.

 

As for riveting, I have a hand rivet setter for 1/8" (~3mm) rivets, and purchased a length of 1/8" CP titanium rod to form my own rivets from. I haven't made any yet, but I'm confident (in the tool and my ability to use it) that it will work well.

 

As for my spot welder, the first one (Harbor Freight model, made in Armenia) has a failed switch which I plan to repair at some point. In the mean time, I bought a new one on eBay (Made in China) which works better than the HF model and even came with extra electrode tips! The Chinese model costs less than the HF unit as well, runs quieter, heats faster and I'm quite pleased with it.

 

WSM

 

Edit: If you have the tools and skills, I suppose that CP titanium screws and nuts could be fabricated in a home workshop as well. I never bothered, since spot welding (more expensive, but worth it) has served my needs so far.

Riveting sounds nice, but its not easy to take apart without the loss of titanium.

I like the idea of using screws for my 300A cell because of the opportunity to change anodes to PbO2.

A Spot welder which is capable of welding two 1mm Sheets together can easily be made out of an MOT at home as you can see on page 225.

With the use of an more powerful transformer (maybe rewinding an old Welding transformer) you might have the potential to weld thicker sheets.

 

In the Meantime i've built a tiny 80ml cell which is now operating at 5v12Amps.

The cell gets quite hot so it sits in a waterbath outside but its still boiling i think.

 

I just want to try out, how long the MMO will last at high temperature in an uncontrolled Cell.

The electrolyte was made out of 70ml water and 35g of table salt which will be replenished tomorrow eve by another 35g of salt. This will be done until a precipitant of NaClO3 appears.

This also might be the size i will use for an array of Cells imersed in the same electrolyte.

Edited January 7, 2018 by PTFE

[PTFE]

Hey guys.

Im back from work now and had a quick look at the small cell.

During the day the Cell-volume dropped to ~50ml and only half of the cathode was still under the surface. The current had fallen to 2A but rises quickly afer the cell was replenished and placed outside of the cooling-jar and after 5min i was back at 8Amps.

[PTFE]

Today i got myself some nice 2x3m of 120mm² flexible Cu-conductor and the 30mmx600mm Titanium rod for connecting the electrodes.

Just to give you an impression of the currents that this cell will handle.

 

The voltage drop at 5V/300A 6m120mm² is 5,36% or with other words: the voltage at the end of the line is (5*0.9464)= 4,73V

That means 0,27V are lost over the lenght of the Cu-conductor and ( 300A*0,27V)/2=40,5W are lost per conductor, or 81W in total.

 

I think, the line will get a little warm at 300+ Amps.

 

But since 120mm² is rated at 344A for group 3 I don't think it will be a problem.

 

at max 30°C ambient temperature:

Group 1 292A: one or more single lines in a tube;

Group 2 292A: one or more multicore cables in an open wireway

Group 3 344A: one or more single lines in open air with distance to each other (minimum as the diameter of the cable)

 

The biggest problem will be the Ti-rods. If they get to hot, the cell lid will get soft and damaged. If this is the case, I will turn a hole inside each of the rods and push in a copper rod to get a much better current rating.

 

greetings

PTFE

Edited January 17, 2018 by PTFE

[Arthur]

30mm DIA is 700mm² so should carry enough current. I'd suggest that you run at much less current initially if you can, things happen very fast if you leave that much current unattended and something unintended happens. If you leave 300a flowing for long a lot of chloride will be converted into chlorate, should you ever run low on dissolved chloride the electrodes may suffer.

[PTFE]

Hey Arthur, thank you

Sure i have to make supervised test runs first because the power supply and the cooling of it has to be tested too.

Im also not sure, how hot it will get in the cell and how much cooling and refilling i need.

Low chloride will not be a hughe problem since i'll use 7000g NaCl / 20l which should be consumed after 4,5 days assuming 60%CE.

 

Here are some quick calculations of the voltage drop of the Cu-wires and the Ti-rods.

Since i've calculated the current drop of a 20mm ti rod before i was sure that for 300Amps 30mm would be enough.

 

 

 

 

 

The formular is quite easy,

 

 

ΔU =(2*L*I) / (ϰ*q)

 

with units:

ΔU =(2*L(m)*I(A)) / (ϰ(m/Ω*mm²)*q(mm²))

 

ΔU = Voltage drop in Volts

2*L = Length of conductor ( times 2 because you have one length to the consumer and one back)

I = Current trough the system

Kappa ϰ = electric conductivity

q = Cross section of the conductor

 

 

the Kappa-values for various materials can be found on the internet but

 

copper has 58m/Ω*mm²

titanium has 2,56m/Ω*mm²

 

[WSM]

DSC_04681.JPG

Today i got myself some nice 2x3m of 120mm² flexible Cu-conductor and the 30mmx600mm Titanium rod for connecting the electrodes.

Just to give you an impression of the currents that this cell will handle.

The voltage drop at 5V/300A 6m120mm² is 5,36% or with other words: the voltage at the end of the line is (5*0.9464)= 4,73V

That means 0,27V are lost over the lenght of the Cu-conductor and ( 300A*0,27V)/2=40,5W are lost per conductor, or 81W in total.

I think, the line will get a little warm at 300+ Amps.

But since 120mm² is rated at 344A for group 3 I don't think it will be a problem.

at max 30°C ambient temperature:

Group 1 292A: one or more single lines in a tube;

Group 2 292A: one or more multicore cables in an open wireway

Group 3 344A: one or more single lines in open air with distance to each other (minimum as the diameter of the cable)

The biggest problem will be the Ti-rods. If they get to hot, the cell lid will get soft and damaged. If this is the case, I will turn a hole inside each of the rods and push in a copper rod to get a much better current rating.

greetings

PTFE

 

Interesting. It appears that we're thinking alike concerning larger cells with higher current demands.

 

I had a similar thought regarding boring a hole in solid CP titanium leads and filling the space with large diameter copper rods, to increase conductivity and reduce wasted power (which manifests as heat and can damage the polymer compression fittings used to seal the leads in a cell).

 

I've been using welding cable to feed my cells, due to their flexibility and ability to carry large amounts of current with low loss of power. I also use crimped on lugs as your photo shows. I bought an inexpensive lug crimper from the welding supplier and several plated copper lugs to use. They're wonderful, as long as corrosive fumes and liquids are kept away.

 

Keep up the good work. I look forward to seeing your progress.

 

WSM

Edited January 20, 2018 by WSM

[MrB]

IF you are to use a copper rod as your conductor, wouldn't it be better just to use a Ti pipe & threaded end cap, pull it as tight as possible, throw a bit of tin in to the hole, melt it, and try to drop in the copper rod, in such a way that it isn't in contact with the Ti pipe until get gets down to the bottom where the molten tin would help it create a solid connection? (Or just melt enough tin in the pipe to fill it, when the copper rod is pushed in. Preheating it would seem like a good idea at that point.)

 

I mean... Not much point in machining a solid rod Ti into a pipe, just keep it for a rainy day, and get a pipe... At the very most, machine a end cap with a press fit from the rod, if finding a suitable screw on turns out to be a pain.

[PTFE]

 

Interesting. It appears that we're thinking alike concerning larger cells with higher current demands.

 

I had a similar thought regarding boring a hole in solid CP titanium leads and filling the space with large diameter copper rods, to increase conductivity and reduce wasted power (which manifests as heat and can damage the polymer compression fittings used to seal the leads in a cell).

 

I've been using welding cable to feed my cells, due to their flexibility and ability to carry large amounts of current with low loss of power. I also use crimped on lugs as your photo shows. I bought an inexpensive lug crimper from the welding supplier and several plated copper lugs to use. They're wonderful, as long as corrosive fumes and liquids are kept away.

 

Keep up the good work. I look forward to seeing your progress.

 

WSM

 

Hi WSM

I Think the use of high power Cells gives out more advantages, especially because im an electronic engineer for industrial engineering and i know how to set up and operate high-power applications safely.

Imagine you have te opportunity to let your cell run for a week once every 1-2 years to keep up your stock of xxClO3/xxClO4.

It saves many hours of effort in time and also you have only a small waste of energy due to a more efficient power consuption over long time comparison.

You might also save some Hcl in high power applications.

The only disadvantage is the consuption of money if you don't get stuff for free to build the cell and the power-supply.

Im planning on that cell for over a year now and gathering of materials started immediately afterwards.

 

The cables i use are the harmonized H07V-K-1x120mm² cables for wiring in industrial applications, I have the benefit to use the tools at work for crimping and also we have large dia. shrinking tube to secure the connections to the cable lug.

The use of the right cable is indispensable even more if you use high amperage.

With the use of the wrong diameter cable, even when you use a PC Power supply, you're always in risk of a fire.

If the current is changing over time, your cable which was working fine might start to burn away it's insulation when the current is rising.

There are several rules that you have to follow as you chose your cable in industrial setups.. but for a home-cell you only have to take a look at the voltage drop and the current rating of your conductor.

Even when a conductor is rated for 300Amps, you might have a lenght of 10m and since we are working with extra low voltages we have to worrie about the Voltage drop over a long distance.

If you loose 0.5V at 300A you also loose 150W of electricity which is enough for some to power their own small cells on the sil.

 

 

IF you are to use a copper rod as your conductor, wouldn't it be better just to use a Ti pipe & threaded end cap, pull it as tight as possible, throw a bit of tin in to the hole, melt it, and try to drop in the copper rod, in such a way that it isn't in contact with the Ti pipe until get gets down to the bottom where the molten tin would help it create a solid connection? (Or just melt enough tin in the pipe to fill it, when the copper rod is pushed in. Preheating it would seem like a good idea at that point.)

 

I mean... Not much point in machining a solid rod Ti into a pipe, just keep it for a rainy day, and get a pipe... At the very most, machine a end cap with a press fit from the rod, if finding a suitable screw on turns out to be a pain.

Hi Mr B

The Idea of a tube filled with a rod came in my mind before, but i don't like the idea of filling a tube with soldering tin or something like this.

Since you have to use flux for the oxide-free coonnection it would get rather messy.

I also have dia.30mm and 20mm Ti Rods at home and three Cu rods with 10mm dia. so i just have to ask for turnig out the inside of the Ti on the lathe and after heat threatment to glowing redhot the pre-cooled copper-rod would be smashed inside of the glowing ti-rod to give a shrink-pressure-fitting (dont know how to translate it from german in better words)

 

 

Here is what i've gathered so far.

Not seen here are the Ti-Seet's i've bought for the Cathodes and the connections inside of the cell, The Anodes shown earlier in this tread and the 300A Supply some pages ago.

 

This is how the cell body will look like.

Those KG2000 tubes are made out of PP and are 5mm thick the fitting will be on top to reduce leakage ability.

 

 

 

Unfortunately one of the 80mm Ti rods is commposed out of 6AL4V and the other seems to be Grade 3.

 

I've planned to lathe them down for the use as nuts in the connection system, and i dont like an unsymmetrical builtup.

 

The Grade 3 piece will be cut in 3 parts.

2 used for nuts inside the cell and the big part will be used for the connection to the Copper bar outside.

The 6AL4V Pice must be used outside i think, and it will only be used for the connection to the copper bar.

Edited January 21, 2018 by PTFE

[Arthur]

PTFE I really like the connecting leads, and the properly crimped lugs. IIRC from old data on plastics compatibility PP is not good PVC is OK, cPVC is good and PTFE is as good as it is expensive. HOWEVER using parts of a plumbing system leaves you at the mercy of the system gaskets, which will be rubbery and suited for drain type liquids NOT pH 10 and strongly oxidising. I had some tanks for a photographic process made from 4" (100mm) PVC soil pipe and fitted them with solid, thick PVC bottom, and some PVC side fittings, all glued in with proper PVC pipe cement.

 

In all cells the current limit is also determined by the cooling available, some of the current is lost as IR heating which goes into the cell and you must achieve steady state temperature balancing heat lost from all surfaces and heat gained from current not used for electrolysis. It's easy for the temperature to exceed the plastic's working temperature, anyway hot plastics degrade faster than when they are cool.

[PTFE]

PTFE I really like the connecting leads, and the properly crimped lugs. IIRC from old data on plastics compatibility PP is not good PVC is OK, cPVC is good and PTFE is as good as it is expensive. HOWEVER using parts of a plumbing system leaves you at the mercy of the system gaskets, which will be rubbery and suited for drain type liquids NOT pH 10 and strongly oxidising. I had some tanks for a photographic process made from 4" (100mm) PVC soil pipe and fitted them with solid, thick PVC bottom, and some PVC side fittings, all glued in with proper PVC pipe cement.

 

In all cells the current limit is also determined by the cooling available, some of the current is lost as IR heating which goes into the cell and you must achieve steady state temperature balancing heat lost from all surfaces and heat gained from current not used for electrolysis. It's easy for the temperature to exceed the plastic's working temperature, anyway hot plastics degrade faster than when they are cool.

Hey Arthur, thanks for your help!

 

https://www.buerkle.de/files_pdf/wissenswertes/technology_properties_of_plastics_en.pdf

https://www.buerkle.de/files_pdf/wissenswertes/chemical_resistance_en.pdf

 

Here are some charts i use for my estimations.

 

Since ive got all that plumbing stuff for free, i don't care if it gets corroded after several runs. Im only concerned if the rubber sealings will withstand.

However it will work out, i could use the Electrodes in any container that is large enough.

 

In the past i used PP Containers intended for food with <1mm thick walls and after 1 week there was significant corrosion but no leakage even after two more runs (1week each) although i run my cells at >75°C.

 

Yes, PP Is not good in regard to corossion resistance but its suitable up to 135°C and the max. working temp. for KG200 is documented as 100°C

 

PVC Is more resistant but only suitable up to 70°C

and The PVC-U used for Plumbing (Wich i get first but then made my thoughts about temperature) is usable up to 60°C.

At 61°C it starts deforming and at 69°C deforming gets significant.

 

Cooling will be a hughe concern and im planning to use pneumatic tubing made out of PE or the flexible PVC aquaristic tube.

Maybe i figure out a way of bending pvc-u pipes used in industrial applications like the guy in a video someone posted some time ago. If bent to spirals they could be installed permanently with nozzles on top to connect the pump.

 

I also plan to built a Vent-cooling system to cool down the escaping vapors and condensing most of the liquid.

Maybe i use a Glass apparatus like a Liebig-cooler or better like the dimroth design. But this would get rather expensive and also i dont like glass anymore.

It would be More recommended if a titanium tube was manteled with a larger diameter StainlesSteel tube, Closed around at the end of the SS tube to built up a Ti/SS Liebig-Condenser wich will not show a sign of corrosion anywhere. But i cant figure out a way, how to seal up the Stainlless against the Titanium.

 

However, Ive got a big 400x400mm copper/aluminium Radiator wich should be capable of cooling most of the waste heat.

with two cooling water reservoirs, one active and the other cooling down, i could switch between them if the radiator is overwhelmed.

Its mostly a trial and error thing once the cell is running but im confident that 200+A will be absolutely no problem.

Since i can vary the voltage between 3,5-6V there is much room to play with.

 

stay tuned guys, i hope you enjoy this project

Edited January 21, 2018 by PTFE

[Arthur]

The reason for Swede's thread about "Bucket Cells" was that you can make a small piece of ©PVC with all the connections to it and through it and use a thin plastic bucket as a disposable cell container. A big container (say 5 gallon ) acts as a buffer to sudden temperature excursions and has a fair external surface area to allow natural convection cooling.

 

As photo processing dies in favour of digital media, look for components in the used lab equipment market. I've mentioned Iwaki Bellows pumps before, -They will pump up to 30% sulphuric acid for ever and do controlled flow if suitably driven.

 

Glass can fail by erosion in the strongly alkaline liquor of a non pH controlled cell.

[WSM]

IF you are to use a copper rod as your conductor, wouldn't it be better just to use a Ti pipe & threaded end cap, pull it as tight as possible, throw a bit of tin in to the hole, melt it, and try to drop in the copper rod, in such a way that it isn't in contact with the Ti pipe until get gets down to the bottom where the molten tin would help it create a solid connection? (Or just melt enough tin in the pipe to fill it, when the copper rod is pushed in. Preheating it would seem like a good idea at that point.)

I mean... Not much point in machining a solid rod Ti into a pipe, just keep it for a rainy day, and get a pipe... At the very most, machine a end cap with a press fit from the rod, if finding a suitable screw on turns out to be a pain.

 

If you check the Blog section, Swede has several posts regarding using tubular CP titanium for power leads to the electrodes, so they can be sealed into the cell lid with PVDF compression fittings. He filled them with molten tin. I did something similar but used common 50:50 tin:lead solder to fill the modified tubing.

 

Later, to lower the temperature of the operation (by increasing the electrical conductivity of the titanium leads), I put solid copper rods inside the titanium tubing, and it worked well.

 

My latest efforts had problems with water (I am leak testing the cell with H₂O before setting it up with electrolyte) leaking through the titanium tubing. It's important because my design involves running the electrodes through the bottom of the cell, rather than through the lid.

 

Unless I can get a proper seal in the tubing, I plan to resort to using solid titanium round rods and bore into them (but NOT all the way through them) and fill the open space with solid copper round rods to increase electrical conductivity, reduce resistance and also remove any chance of liquid getting through.

 

I believe there are photos posted several pages ago...

 

WSM

[WSM]

Hey Arthur, thanks for your help!

https://www.buerkle.de/files_pdf/wissenswertes/technology_properties_of_plastics_en.pdf

https://www.buerkle.de/files_pdf/wissenswertes/chemical_resistance_en.pdf

Here are some charts i use for my estimations.

Since ive got all that plumbing stuff for free, i don't care if it gets corroded after several runs. Im only concerned if the rubber sealings will withstand.

However it will work out, i could use the Electrodes in any container that is large enough.

In the past i used PP Containers intended for food with <1mm thick walls and after 1 week there was significant corrosion but no leakage even after two more runs (1week each) although i run my cells at >75°C.

Yes, PP Is not good in regard to corossion resistance but its suitable up to 135°C and the max. working temp. for KG200 is documented as 100°C

PVC Is more resistant but only suitable up to 70°C

and The PVC-U used for Plumbing (Wich i get first but then made my thoughts about temperature) is usable up to 60°C.

At 61°C it starts deforming and at 69°C deforming gets significant.

Cooling will be a hughe concern and im planning to use pneumatic tubing made out of PE or the flexible PVC aquaristic tube.

Maybe i figure out a way of bending pvc-u pipes used in industrial applications like the guy in a video someone posted some time ago. If bent to spirals they could be installed permanently with nozzles on top to connect the pump.

I also plan to built a Vent-cooling system to cool down the escaping vapors and condensing most of the liquid.

Maybe i use a Glass apparatus like a Liebig-cooler or better like the dimroth design. But this would get rather expensive and also i dont like glass anymore.

It would be More recommended if a titanium tube was manteled with a larger diameter StainlesSteel tube, Closed around at the end of the SS tube to built up a Ti/SS Liebig-Condenser wich will not show a sign of corrosion anywhere. But i cant figure out a way, how to seal up the Stainlless against the Titanium.

However, Ive got a big 400x400mm copper/aluminium Radiator wich should be capable of cooling most of the waste heat.

with two cooling water reservoirs, one active and the other cooling down, i could switch between them if the radiator is overwhelmed.

Its mostly a trial and error thing once the cell is running but im confident that 200+A will be absolutely no problem.

Since i can vary the voltage between 3,5-6V there is much room to play with.

stay tuned guys, i hope you enjoy this project

 

The high temperature cell runs into problems unless high temperature fluoro-polymers are used. I don't have access to affordable PTFE so my default is the use PVDF (Kynar), which is marginally temperature resistant enough to do the job. Unfortunately, Kynar plastic requires expensive, specialized welding equipment to weld it into a useful form (it's not able to be solvent welded like PVC or CPVC).

 

I believe borosilicate glass may work for a hot cell, and may do a test with a 4 or 5 liter borosilicate beaker to prove the concept. If it works as expected, it should greatly simplify and accelerate the production of sodium chlorate for making perchlorates from. We'll see...

 

WSM