making potassium (per) chlorate

[greenlight]

Thankyou for all that info WSM. I have started running the cell again anyway until I get some sort of ampmeter.

I mixed some of the crystals that evaporated in the bottom of the cell when i poured out the electrolyte with some powdered sugar. It smolders and almost sustains a weak deflagration on its own which indicates the presence of some chlorate oxidiser which is good news.

Thanks again I will update as I go.

[WSM]

Alright here's an update on the lead dioxide anodes. First of all these are 50mmx150mm titanium mesh lead dioxide coated. I do not have the ability to purchase several hundred of these so I would have to purchase a small quantity at a time and the quote of manufacture and ship from china would make these about $50.00 each, more than some would have hoped for. If their is enough people wanting one I would be willing to attempt a purchase only after someone tries a sample. I can get one sample sent to me but at a hefty $95.00 price tag. If it turns out to be a good sample I would like for whomever tests it out to recomp me for what the anodes will cost $50.00 and I will eat the$45.00 loss on the sample. If it's not up to quality I just ask that you send back to me and owe nothing other than shipping back to me. If the product is good I will make a purchase and offer here in small batches. I quess I'm asking if their is enough people here willing to purchase if the sample checks out ok? What do you guys think? Pass on the deal or have a sample sent?

Wow, that is a hefty price (or maybe I'm not realistic about what they should cost). If we shop around and get quotes from several potential suppliers, maybe we can do better? It's worth a look.

 

WSM

Edited November 5, 2016 by WSM

[Visco]

I already have another supplier working on it. We'll see what they come up with.

Also if I know how much interest their is the price may fall with larger orders. If I can get a price break I just have to make sure I don't end up with a order of anodes that I have to keep because everyone wants one and then decide they don't. My funds are limited and I'm not one to take money before item is in my hand because anything can happen and I'd rather take a loss as to owe people back money for something that fell through. And I think everyone else can respect that too.

Edited November 1, 2016 by Visco

[Maserface]

Where are they coming from?

 

I have nothing to report, entirely because I haven't had time to sit down and work on it.

[Visco]

Small factory in china. All of the larger companies I contacted will only deal in hundreds and sometimes couple thousand at a time.

[WSM]

Thankyou for all that info WSM. I have started running the cell again anyway until I get some sort of ampmeter.

I mixed some of the crystals that evaporated in the bottom of the cell when i poured out the electrolyte with some powdered sugar. It smolders and almost sustains a weak deflagration on its own which indicates the presence of some chlorate oxidiser which is good news.

Thanks again I will update as I go.

I did the same thing with the first crystals pulled from my initial sodium chlorate run.

 

My sample with granulated sugar burned with minor vigor, but enough to confirm my hunch it was chlorate.

 

Congratulations.

 

WSM

[Kevin]

Alright, I'm finally sitting down to post about my recent cell run. Bear with me, this may get a little long.

 

Starting with my electrodes: I used a 1" x 5" piece of MMO sandwiched between two grade 2 titanium plates with the same dimensions. My leads going down to my anode/ cathodes were 1/4" OD tubing, also grade 2 titanium. I tried to file the inside of my tubing to remove some of the oxide prior to filling, but due to their narrow diameter, it's hard to say how much the filing accomplished. I filled them with 8 AWG copper wire as well as lead-free solder.

I wasn't sure how far apart to space my electrodes, so I tested with one cathode and anode. I figured the maximum current to run my cell at was around 19 amps, so my target was 9.5 amps when experimenting. I figured that another cathode on the opposite side, an equal distance apart should roughly double the current (I equated it with being like parallel resistors). After spot welding the cathodes together I tested and found my current was considerably lower than I'd wanted. I managed to bend the titanium straps connecting the cathodes to bring them closer together, thus raising the current, but I'll elaborate on this later.

To make my electrical connections, I cast some aluminum blocks. I drilled through them lengthwise to fit over the electrodes and to allow the wires from the electrodes and power supplies to overlap one another. I drilled and tapped two holes along to side of the aluminum blocks for one bolt to hold onto the titanium tubing and another bolt to firmly press together the wires from the electrodes and power supply.

My power supply was a computer PSU rated for 32A on the 5 volt rail. I had ordered a voltage/ current panel meter from China and here's how everything looked once wired up

 

For my lid I used some HDPE puck board and cut a circle using a router. I drilled and tapped holes for my vent (3/8 NPT-1/2 hose barb) and compression fittings for my electrodes (1/4 NPT-1/4 compression). To seal it I made a silicone O-ring by using a router to make a circular groove in a piece of HDPE, filling it with silicone and then smoothing up the top. After a 1.5 to 2 days it was cured enough to remove. Silicone doesn't bond to HDPE, so with a little care it can be removed. Every O-ring I made had air bubbles trapped at the bottom that I'm not sure yet how to avoid. I put the bubbly side face-up and it didn't seem to cause any issues. A groove was cut into the lid for the O-ring to fit into and it looked something like this

I think I posted this picture over a year ago, but it shows the concept clearer than any pictures I have with clear silicone.

I was very pleased with how the seal worked as there was no definitive salt-creep. The only problematic salt-creep I had came through where the compression fittings were threaded into the lid, so I may use a little teflon tape next run to seal that. Here's what it looked like all hooked up

 

 

I prepared a saturated KCl solution by filling a jar with distilled water and adding a bunch of salt, stirring occasionally over a few days. The cell current proved hard to maintain where my target was. It started at 13.6A (19A- 19.6A was my aim) but rose steadily until I had to stop the run (by removing the electrodes) when the current reached 27.2A and was still rising. I'd read that current efficiency goes up with temperature, but I did not expect that much! The next morning I bent the cathode straps to increase their spacing and I restarted the cell. The current was again getting too high (24.9A) so I tried adding a fan to cool off the cell. This proved to be my required solution as the current started to decline afterwards. I added another fan later because the current was still too high. After this experience it's clear why a variable power supply is recommended- and it's for this reason that I'm working on modifying my PSU's voltage reference to be able to adjust its output.

 

I had initially planned to run this cell with pH control, but I ran out of time to figure it out. Since my cell body was glass I also wanted to keep the temperature down to decrease the rate or avoid altogether any etching of the glass by the high pH, potentially ruining my anode. Once I have pH control I hope to run my cell hotter, for this run I tried to keep it in between low 30's to low 40's °C by moving my fans.

 

Overall, my cell ran for 25 days before I stopped it and placed it in the shop fridge to precipitate out as much KClO₃ as I could. After drying, my final yield was 1236 grams and a quick burn test with icing sugar burned quite vigorously with a violet color, as I was expecting/ hoping to see!

 

My next steps are to finish modifying my PSU to be able to lower its voltage, figure out a pH system and setup some sort of vacuum filtration. My current filtering method involves using polyester board shorts (I got the polyester idea from Richard Nakka's rocketry site) and squeezing out as much excess cell liquor as I can by hand (with gloves). It worked okay when I was working with nitrates/ chlorates in small amounts, but this yield took me quite a while to filter and when I scale up it'll hardly be feasible to filter by hand. I would also like to buy a temperature probe to insert into the cell liquor rather than just taping a thermocouple to the outside of the cell I'm hoping I can get these issues figured out by Christmas break as I'll have 2-3 weeks to give the cell another run!

Edited November 1, 2016 by Kevin

[WSM]

Nice job, Kevin.

 

Your description reminds me of a (nearly forgotten) detail about an experimental cell I did years ago, and the way it performed. I expected my cell to run at 24 Amps, but it started at about 16 Amps. I kept running it and the current (and temperature) slowly climbed till it reached a maximum of about 24.5 Amps and then slowly dropped till I shut the run down at about 11 Amps. The temperature maxed at 55^oC and stabilized.

 

My cell was also in a one gallon glass jar and ran KCl to KClO₃. I think the starting amperage was what the electrodes could use, limited by the temperature, initial resistance, electrode size and possibly other inefficiencies. I think as things got going, conditions improved as the temperature increased and the internal chemistry shifted. After the maximum current draw had been reached, the optimal conditions were passed and as the chloride levels decreased (converted to chlorate, which started dropping out of solution) the current draw correspondingly lowered. My plan was to stop the run when the current dropped to roughly 50% of the maximum level reached.

 

I used a 5 Vdc, 30 A power supply and an analog ammeter with a matching shunt. The leads to my electrodes were too short (so the electrodes were in the upper half of the jar) and I experienced thermal layering in the cell till I bubbled air through the cell to mix up the electrolyte, and that worked well till the air tube (1/4" PTFE tubing) plugged up with crystals. I had to clear the tube a few times until the run was completed.

 

Longer leads would have put the electrodes deeper into the cell and promoted better mixing by hydrogen lift and natural circulation. The bubbling air would have worked better if I ran a coil of the air tubing in a heated water bath before into the cell, so cold air wouldn't have encouraged crystals to drop out of solution and plug the air tube end, over and over.

 

A lot was learned in that experimental cell, and I've progressed in my designs and successes with the things learned from it.

 

I share these details so others can avoid some pitfalls I encountered on this path. Thank you for doing the same. If we put our experiences in words and share them here, we'll all benefit and progress.

 

WSM

Edited November 2, 2016 by WSM

[WSM]

Small factory in china. All of the larger companies I contacted will only deal in hundreds and sometimes couple thousand at a time.

 

China is one source and India might be another.

 

WSM

[Kevin]

I'm trying to figure out my acid dosing system. I'm planning to do my next run in my shop so I need everything to be gas tight to prevent HCl from corroding any metals in the shop- or my lungs.

I'm thinking of cementing PVC pipe and other required pieces together to form the reservoir, with a vent in the lid connecting to the cell's vent. The bottom of the reservoir will have tubing connecting it with a PTFE solenoid valve, then in to a needle valve and finally in to the cell. I'm planning to use 1/4" OD HDPE tubing to run from the needle valve, through a compression fitting, into the cell solution. I'll drill several small holes in the bottom inch or so of the tubing to hopefully feed it in nicely. Also, teflon or kynar needle valves are proving hard to find (at least at what I'd consider a decent price), but I found what might be a good one from US plastics: http://www.usplastic.com/catalog/item.aspx?itemid=32208&catid=662

The only issue I can see is with the EPDM seal. Looking at datasheets I've found EPDM to be good for 3M HCl but not full strength. And since I don't know at what rate I'll be adding HCl or how quickly I'll lose water, I'm not sure how far I'll be able dilute the muriatic acid. Any suggestions?

[WSM]

I'm trying to figure out my acid dosing system. I'm planning to do my next run in my shop so I need everything to be gas tight to prevent HCl from corroding any metals in the shop- or my lungs.

I'm thinking of cementing PVC pipe and other required pieces together to form the reservoir, with a vent in the lid connecting to the cell's vent. The bottom of the reservoir will have tubing connecting it with a PTFE solenoid valve, then in to a needle valve and finally in to the cell. I'm planning to use 1/4" OD HDPE tubing to run from the needle valve, through a compression fitting, into the cell solution. I'll drill several small holes in the bottom inch or so of the tubing to hopefully feed it in nicely. Also, teflon or kynar needle valves are proving hard to find (at least at what I'd consider a decent price), but I found what might be a good one from US plastics: http://www.usplastic.com/catalog/item.aspx?itemid=32208&catid=662

The only issue I can see is with the EPDM seal. Looking at datasheets I've found EPDM to be good for 3M HCl but not full strength. And since I don't know at what rate I'll be adding HCl or how quickly I'll lose water, I'm not sure how far I'll be able dilute the muriatic acid. Any suggestions?

If you read my blog, Homegrown Oxidizers Part Four in the Blog section, it shows some ideas about pH control and acid dosing. Swede also had several pH control ideas, well documented with numerous photos in his blogs.

 

To prevent acid leaks, I suggest testing your home made tanks very carefully. I made an acid reservoir from an XLPE (cross-linked polyethylene) pipette cleaner, because that material is rated to withstand HCl very well (and I had the tank available to me). I had to work very hard to get the modified tank sealed so well that after hours of testing it with water, no leakage was detected. Carefully prepared seals and lots of Teflon tape helped.

 

Leaking acid can cause serious problems for all sorts of things (mostly persons and property). Another thought is to place the tank or whole system in a compatible, secondary containment to capture any leak.

 

I need to set up my sodium chlorate cell with the pH control system for the run after next. I guess we're in the same boat.

 

WSM

Edited November 5, 2016 by WSM

[Arthur]

Bellows pumps by Iwaki (and others) are available on ebay they will pump a high rate, but then can be turned down on the driver cam and then can be time proportioned with a plug in timer. Iwaki pumps were common pumping the replenisher chems on photo processing machines for E6 C41 and print chemistry, there should still be lots around from machine breakers, it's more a problem to find them in your area.

[WSM]

Bellows pumps by Iwaki (and others) are available on ebay they will pump a high rate, but then can be turned down on the driver cam and then can be time proportioned with a plug in timer. Iwaki pumps were common pumping the replenisher chems on photo processing machines for E6 C41 and print chemistry, there should still be lots around from machine breakers, it's more a problem to find them in your area.

 

At Arthur's suggestion a few years ago, I found a low-cost source for these excellent pumps and bought several from a surplus seller on eBay. As Arthur says, they're surplused from photofinishing equipment, so the first order of business was to test them electrically for function, and next clean* them out to remove traces of smelly, liquid residue from their former duties.

 

The Iwaki bellows pumps are well made, small, light weight, quiet in operation and excellent for applying to our purposes. Some run on low voltage DC, but most are rated for about 100 VAC, which is no problem as they work fine on 120 Vac, 60hz power, here in the US. I believe they also come in the 200 Vac range for places where 240 Vac or 250 Vac is the main voltage delivery. I don't think the different frequency of power will negatively affect them either (but just alters the speed they operate at, if I'm not mistaken).

 

I'm also a fan of the Iwaki magnetically coupled chemical handling pumps, which move a lot more fluid and serve well for brine preparation and specialized fluid moving in larger cells. Arthur also made me aware of them and they come from the same source, but since the photo-finishing machines are rapidly disappearing, the low-cost supply of these excellent pumps seem to be dwindling.

 

WSM

 

Edit - *they were cleaned out by pumping tap water through them for a period of time, and the exteriors were cleaned with clear water or mild soap solutions, followed by clear water wiping (don't immerse in water). I circulated the water in a scrap bucket and carefully disposed of the dilute residue, so as not to pollute.

Edited November 8, 2016 by WSM

[WSM]

I'm trying to figure out my acid dosing system. I'm planning to do my next run in my shop so I need everything to be gas tight to prevent HCl from corroding any metals in the shop- or my lungs.

I'm thinking of cementing PVC pipe and other required pieces together to form the reservoir, with a vent in the lid connecting to the cell's vent. The bottom of the reservoir will have tubing connecting it with a PTFE solenoid valve, then in to a needle valve and finally in to the cell. I'm planning to use 1/4" OD HDPE tubing to run from the needle valve, through a compression fitting, into the cell solution. I'll drill several small holes in the bottom inch or so of the tubing to hopefully feed it in nicely. Also, teflon or kynar needle valves are proving hard to find (at least at what I'd consider a decent price), but I found what might be a good one from US plastics: http://www.usplastic.com/catalog/item.aspx?itemid=32208&catid=662

The only issue I can see is with the EPDM seal. Looking at datasheets I've found EPDM to be good for 3M HCl but not full strength. And since I don't know at what rate I'll be adding HCl or how quickly I'll lose water, I'm not sure how far I'll be able dilute the muriatic acid. Any suggestions?

 

Teflon needle valves are hard to find, but vigilant searching has helped me locate several over the years, generally in the $15-$45 range. Most are Teflon but I was able to secure a few PVDF needle valves, also. I have a few PVC needle valves,too but haven't tried them yet.

 

One reason I've avoided running a chlorate cell in my shop, is I don't want to see my expensive machine tools turn brown ! I suppose a proper ventilation system coupled to a cabinet (to isolate the cell from the rest of the shop) would solve my concerns. The cabinet idea would also help in an outdoor setup to help protect it and keep things secure. A fellow enthusiast has done so and it works well. His cabinet looks similar in design to a rabbit hutch (but with more solid walls) and secures his modest experiments from the elements.

 

Good luck.

 

WSM

Edited November 8, 2016 by WSM

[WSM]

Several months ago, Arthur shared a patent he found with me for producing sodium chlorate. In the patent (Circa 1962, when graphite anodes were state-of-the-art), it recommends switching to platinized titanium anodes and running at greatly increased temperatures (between 105^oC and 115^oC) so the water will evaporate as the cell runs, naturally concentrating the liquor so sodium chlorate levels will be high enough to harvest from the cell in greatly increased amounts. Another benefit is feeding the cell with purified brine and not dry salt, eliminating many extra steps.

 

At the time Arthur shared this with me, I was in the development stages of my sodium chlorate cell and thought there were too many issues with running at those temperatures. The limits of the commonly available materials (PVC 60^oC, CPVC 93^oC, silicone rubber is high but chemical resistance can be an issue, et cetera), caused me to set aside the notion of applying the principles advocated in the patent.

 

Since that time, I've gotten more experienced in sodium chlorate manufacture and after considering the process and materials available, I believe I've figured out a way I can try it on an amateur scale.

 

I'm thinking a cell made with PVDF polymer can operate up to 121^oC, so with the average boiling point of sodium chlorate cell liquor (a mixture of NaCl and NaClO₃) being between 105^oC and 115^oC (average 110^oC), this could work. Another option would be a borosilicate (Pyrex) beaker. There are many hurdles to overcome but I think it's at least possible and bears further investigation.

 

WSM

[Visco]

Update. I have found a new supplier for anodes and the prices look good. As long as shipping doesn't become a problem we may be able to make this thing work. I'll let everyone know as I get the full quote and details.

[WSM]

Update. I have found a new supplier for anodes and the prices look good. As long as shipping doesn't become a problem we may be able to make this thing work. I'll let everyone know as I get the full quote and details.

That's great. I look forward to seeing what the unit cost will be, plus how well they work.

 

WSM

Edited November 8, 2016 by WSM

[WSM]

Thankyou for all that info WSM. I have started running the cell again anyway until I get some sort of ampmeter.

I mixed some of the crystals that evaporated in the bottom of the cell when i poured out the electrolyte with some powdered sugar. It smolders and almost sustains a weak deflagration on its own which indicates the presence of some chlorate oxidiser which is good news.

Thanks again I will update as I go.

 

You're welcome, greenlight. You don't have to meter the current to run a cell successfully, but it really helps determine where you are in the run. The more we know, the better we can watch what our cell is doing and also when to stop and harvest our product.

 

With my sodium chlorate experiment, I metered the voltage, current and temperature. I'd love to be able to meter the pH, specific gravity, chlorate and chloride concentration; but I haven't figured out how to do that yet. I imagine there's a way to monitor the pH (and maybe even control it automatically), but we haven't discovered it yet. I wonder if something akin to MMO can be used for a sensor that will survive in an active chlor-alkali cell? It seems possible, but needs to be figured out.

 

Swede researched many different types of pH sensors and found one claiming to be able to withstand the harsh environment of a chlorate cell, but the cost was in the $900 range. Maybe we can find one at a more affordable cost. That would allow active pH control (no more guess work, just set it up and let it work).

 

Till then, we'll keep on guessing using the volume of HCl per amp-hour formula and doing our best.

 

WSM

Edited November 12, 2016 by WSM

[theodusta]

Hey guys,

 

one day ago, I started my chlorate cell and now I have the problem, that I cannot measure the pH. My pH test strips bleach out immediately after dipping in. The problem is that I only have test strips for measuring. I'm open and thankful for any suggestion!

 

Thank you and kind regards!

 

Theo

[TomasBrod]

one day ago, I started my chlorate cell and now I have the problem, that I cannot measure the pH. My pH test strips bleach out immediately after dipping in. The problem is that I only have test strips for measuring. I'm open and thankful for any suggestion!

Hi Odusta! You measure pH only if you want to do a pH control in your cell and you don't need to do that. I fact member WSM is running his cell pH uncontrolled. More important is the current you run your cell at. You should monitor it closely so it does not exceed your electrodes' current rating. Don'ŧ forget to post details of your cell like container, volume, salt type (NaCl or KCl), size and type of your electrodes, current you run your cell, voltage, temperature and power supply type.

[WSM]

Hey guys,

one day ago, I started my chlorate cell and now I have the problem, that I cannot measure the pH. My pH test strips bleach out immediately after dipping in. The problem is that I only have test strips for measuring. I'm open and thankful for any suggestion!

Thank you and kind regards!

Theo

Hi theodusta,

 

Welcome to the discussion.

 

It's true that I haven't used pH control in my own experiments, yet. I do intend to, but after I establish the results without pH control first, for a control. Case in point, the sodium chlorate cell experiment. The first run was from scratch using purified NaCl brine. The second run is going to be run with "depleted" electrolyte, recharged with purified NaCl.

 

The third run is planned to be like the second, but with a timed acid injection system to add dilute HCl to the cell at regular intervals, to try keeping the pH as close to 6.8 as possible. This is in an attempt to optimize the CE (current efficiency) and document the differences with the first two runs.

 

The system works without pH control but, if I'm correct, it works faster with less current consumption with pH control. An improvement from about 50% efficiency up to 80% or 90% is possible with pH control vs.without it. A workable system of pH control was well established by Swede in his blogs. I had my own ideas early on, of how to approach this, but I liked the simpler method Swede proposed, so I adopted his method and built up a couple pH control systems similar to his (evidenced by the photos I posted years ago). My pH control equipment is waiting in the wings to be applied to the sodium chlorate experiment, when I can get around to it.

 

As to pH paper, it's tricky to use with the cell electrolyte because of the bleaching that occurs. What I've done is dipped the tip of the pH paper strip (cheap, but effective pH paper strips from China, purchased on eBay) and quickly observed the lead edge of the wet portion, where a hint of the color change exists for a moment before it bleaches out. It's not perfect, but it is an indication of where the pH is.

 

As Swede clearly says in his blogs, pH pens are quickly destroyed and the best pH sensors are slowly destroyed by exposure to the electrolyte. Due to the nature of the pH sensors, they tend to be "poisoned" by the electrolyte and rendered unusable. Swede explains all of this quite well in his blogs (if you haven't guessed yet, I recommend reading his blogs).

 

What type of pH paper are you using, Theo? If it's not the pH paper, maybe your technique can be modified so you can at least use it for an educated guess as to the pH your cell is running at.

 

Good luck.

 

WSM

Edited November 13, 2016 by WSM

[taiwanluthiers]

You have to use a ph meter for this... ph test strips won't work since as you said it bleaches out immediately. However what you can try is dilute them a bit and then use the test strip, but look at the color fringes rather than the wet strip...

[theodusta]

Hi Odusta! You measure pH only if you want to do a pH control in your cell and you don't need to do that. I fact member WSM is running his cell pH uncontrolled. More important is the current you run your cell at. You should monitor it closely so it does not exceed your electrodes' current rating. Don'ŧ forget to post details of your cell like container, volume, salt type (NaCl or KCl), size and type of your electrodes, current you run your cell, voltage, temperature and power supply type.

Hi Tomas,

 

atm the cell run has the following values:

 

Salt Type: 1050g of weed killer (consists of 60% NaCl and 40% NaClO3)

Volume: 2500ml

Voltage: 4,01V

Current: 25A (in constant current mode)

Power Supply: QJE PS3030 900W (voltage and current can be regulated freely between 0-30V and 0-30A)

Electrodes: Anode is MMO Ru-Ir Type / Cathode is titanium

Electrode Size: 15cm x 5cm

Temperature: 72°C

 

Correct me if I am wrong: I thought that pH control is of great advantage within a chlorate cell, because a pH of 6,8 increases cell efficiency and lifetime of the electrodes. The pH control doesn't matter within a perc cell I guess.

Edited November 13, 2016 by theodusta

[WSM]

The pH control doesn't matter within a perc cell I guess.

 

Some documentation says it does and others say it doesn't. I ran my perchlorate cell experiments last year without pH control and they worked great. Maybe on an industrial scale it makes a difference, but on an amateur scale, in my opinion, I don't see the need for it.

 

In chlorate cells, on the other hand; evidence shows a vast improvement when keeping the pH around 7 (6.8 being optimal) rather than higher, where it naturally tends to run.

 

WSM

Edited November 14, 2016 by WSM

[WSM]

Swede explains all of this quite well in his blogs (if you haven't guessed yet, I recommend reading his blogs).

 

I should mention, the blog section is set up to show the latest entry first. To read them chronologically, you may wish to go to the last entry and read them in reverse order. I find that starting on page 11 of Swede's blogs avoids the multiple postings of his excellent article on tubular leads.

 

Happy hunting!

 

WSM