39 replies to this topic

[Swede]

Months ago, Tentacles and I kicked around a concept we called the Bucket Cell adapter for the (per)chlorate process. Rather than spend $150+ on sheet PVC and sweat blood making a cell, why not use an HDPE bucket lid fitted with truly durable hardware? It could be shifted to a fresh bucket when the current bucket succumbs to chlorine and other noxious chemicals, and as cheap as the buckets are, it does make a lot of sense.

This is my interpretation of the Bucket Cell Adapter, usable on 2.5 gallon on up to any larger size, so long as the bucket lid is reasonably flat. It's first use will be to collect data real-time, comparing voltage, current, and temperature throughout a run; the next will be the long-delayed test of the lead dioxide anode to create perchlorate.






Read all about it in my new blog entry:
The Bucket Cell Adapter

Thoughts and observations are always appreciated.

[asilentbob]

I am impressed!

[TheSidewinder]

Way cool, Swede!

(It's the Featured Entry now.)

[WSM]

Read all about it in my new blog entry:
The Bucket Cell Adapter

Thoughts and observations are always appreciated.

Very nice work, Swede. I'm looking forward to seeing how the bucket cell holds up under normal cell environmental conditions. I'm sure we're all waiting to see low the lead dioxide anode performs as well. Good luck with it!

[Swede]

Thanks guys. The only thing that concerns me is the placement of the O-ring stock relative to the clamp bolts. I had the choice of having the clamp bolts inside the O-ring, or outside, both with advantages and disadvantages. I think this will work. The bulk of gas and salt creep comes straight up from the electrodes; the splash and mist will contact the upper sandwich piece, creep radially outward, and contact the O-ring, which should prevent any leaks. The only real path for leakage is up the flat straps, or through the bolt holes, and I don't think the latter will happen, since I've got 1/2" thick PVC threaded 10-32, and tightly bolted. Those holes can be considered sealed.

There's a lot of room for modification. I tend to overcomplicate, and it can definitely be simplified... a solitary fitting that clamps on to a bucket and converts it into a cell, with all of the quality in the BCA rather than the big cell itself.

[tentacles]

Swede: If the bolt holes do present a problem, all you need to do is wrap the threads with 1-2 wraps of teflon tape. I can't wait to see how the LDA performs. Not sure I'll be doing much experimentation this winter, as I've bought a new (used, antique?) lathe that's going to need some TLC. A South Bend 10k 42" bed. Should be a big upgrade from the Myford ML7.

[Swede]

Hey Tentacles, good luck with the lathe. I know that rebuilding one can be a real project. It is very easy to nitpick and go for perfection rather than function.

I don't expect any probs at all with the Ti bolts and holes. The interface is just too tight. There's no way anything is going to creep through. But a wrap of PTFE tape would probably be smart regardless to keep the threads clean for assembly and disassembly.

[Swede]

The Bucket Cell Adapter - preliminary report. The run started with pure KCl (so as to collect valuable data) rather than used/recharged electrolyte. The dry yield was 2 fat bags of KClO3, both over 1 kilogram, out of an 8.7 liter cell; barely more than 2 gallons.

For those into efficiencies, I have calculated the following numbers that may be helpful with their own systems. This particular run yielded probably the greatest amount of chlorate per liter electrolyte of any chlorate run that I have eve done, mainly because I dissolved (and started) the KCl at an elevated temperature, yielding a higher % chloride ion than all previous runs.

Cell volume:

8.7 liters

KCl:

375 grams per liter, total 3262.5 grams

Avg. Temp:

62 degrees C.

Chloride:

Starting Chloride (Molar-basis): 1552.6 grams
Starting Chloride % (Molar basis): 17.84%
Starting Chloride % (Hach Titration strips): 17.9%
Ending Chloride % (Hach): 5.5%

This shows that the Hach strips are accurate. Given a known amount of chloride in a given volume, there should have been 17.84% chloride in the electrolyte, and the Hach strips confirmed this beautifully, despite the need to dilute 50:1 with care.


Ampere-Hours consumed:

Exactly 4,300

Mass Yield:

Dry Yield KClO3: 2120 grams
Wet Yield KClO3: 870 grams
Total Yield KClO3: 2990 grams, +/- 87 grams

The wet yield is based upon the solubility of KClO3 in electrolyte at 30 degrees C, which is 100 grams per liter. The actual wet yield is impossible to determine, and is only an estimate. It will probably vary by 10%.

Current Efficiency (CE): KCl --> KClO3 CE = 131.22 * grams/Ah

CE = 131.22*2990 / 4300
CE = 91%

That is a WONDERFUL efficiency for a home cell. Frankly I am a bit shocked, but decent pH control and a good anode is going to produce such efficiencies. If I assume that the wet yield is not 870 grams (likely because the remnants are a mix of chlorate with other species, and the amount of KClO3 in solution will not reach theoretical - assume that the wet yield is minus 20%, 696 grams vs 870, the CE would be:

CE = 131.22*2816 / 4300 = 86%

The probable efficiency was between 86% and 91%, still excellent, and I am very pleased. Without pH control, the best that can truly be expected is 66%. A modern chlorate plant with all the bells and whistles will panic if the efficiency drops below 95%, because their product will not be price-competitive due to power costs.

Further notes: The bucket cell hardware performed well. Only a moderate salt creep between the PVC sandwich and the lid. The Titanium fasteners came through untouched.

Yield of chlorate per liter of electrolyte...

Dry: 243 g/l
Dry + Wet: 344 g/l

Leftover KCl: 5.5% chloride yields 11.56% KCl. 116 grams pr liter * 8.7 liters = 1009 grams.

Total KCl consumed = 2253 grams

.

pH:

pH varied from 6.37 to 7.27, average of 6.6 over the run, based upon manual measurements. Definitely a best estimation but probably pretty close.
HCl consumed: 550 ml of 16% (half-strength) HCl; approximate mass of 88 grams of pure HCl molecule.
HCl consumed per ampere-hour: 0.0205 grams per aH

Probably the most interesting observation (aside from the electric chart-recorder data, to come later after analysis) is the HCl consumed per amp-hour. The classic rule of thumb is as follows:

Published, recommended HCl consumption:

0.057 ml of concentrated (32%) HCl per ampere, per hour
0.114 ml of diluted (16%) HCl per ampere, per hour

Actual HCl Consumption:

16% HCl consumed per ampere-hour: 0.128 ml per aH

Edit: I made a math error earlier. The actual amount of 16% HCl consumed per amp-hour is right in line with the official recommendations:

Official: 0.114 ml 16% HCl per aH
Me: 0.128 ml 16% HCl per aH

Additionally, as the cell chemistry matures, there is some speculation that a buffering action takes place, meaning that less HCl is needed below about 12% chloride, or when KClO3 crytstals begin to form.

Everything went perfectly with the exception of the HCl. It would be best to start low, and adjust as needed to seek a pH of 6.7, but anything between 6.5 and 7.0 is very good. The data stream from this run will be amalyzed and published soon.

If you have read this far, you are a dork! Welcome to the club.

Edited by Swede, 28 November 2009 - 09:43 AM.

[patsroom]

Fanatic! That is a fanatic results from a home made chlorate cell. Keep up the Great work you been doing as for those whose wish is to follow in your steps will have a path to help them along the way. With such work it well be hard to compete with you for the knowledge that you have given to the rest of us.
I can not wait for your lead dixiode anode to be tested with the hopes that you are just as successful with it as well.
What makes the rest of us "dorks" is not reading all of your post, but that we must run to caught up with you in the experience in the production of the cell and it's contents. Pat

[Ventsi]

Thou be crowned King Geeketh!

Kidding aside, those are some marvelous results!! 91% is incredibly high CE for even a setup such as yours. Kudos.
Are the BCA's going to be available for sale VIA custom requests? If so I might look into one!.

[bikemaster]

Wow!!! 91%-86% efficiency. Swede seriously, did you kill someone (can't get the quote from sciencemadness, but I remember that you said that you can kill for and efficiency of 90%).

I will wait for your DAQ data, I expect to see nice correlation between the temperature, the chloride concentration and de voltage. Bye bye titration!

For the difference in the need of HCl, I am not sure that it really come from the buffering effect of the different ion in the cell (ClO-, ClO2-,ClO3). Because if it was true, the need in HCL will not be different, the only difference is that it will be much harder (or easier) to keep the pH steady. Maybe these ion acted has buffer, I don't know, but that will not make difference in the HCl consumption. Maybe that a mature cell just produce less chlorine??? That will be traduce in a smaller need of HCl.



Not really in link with this, but did you have outputs analogs on your DAQ from dataq? That can be the the best way to reach the big plant efficiency. Imagine of a pH control at ±0,1 and a cell steady at the best temperature, it is also possible to get a control on the chloride concentration (adding the salt during the process).

[Swede]

Thank you guys, these results did work well. I made a bad math error in calculating HCl consumption, and the reality was, my HCl use was very close to officially published numbers. Diluting the 32% HCl in half to 16%, the industry usage would be

0.114 ml 16% HCl per aH

and my own usage was

0.128 ml 16% HCl per aH

Given that the pH was a bit low the whole time, the industry rule of thumb is accurate. I am glad I discovered the mistake, because that was the only thing that was really odd about the whole run, a 5-fold difference in HCl consumption. So in an attempt to control pH, using the following figures is a good start:

0.057 ml of concentrated (32%) HCl per ampere, per hour
0.114 ml of diluted (16%) HCl per ampere, per hour

The only trick is that HCl demand is higher at the beginning, and is going to taper as Cl- declines. I am going to try and incorporate aH used into the equation, creating a dynamic delivery based upon the age of the cell.

[Swede]

Not really in link with this, but did you have outputs analogs on your DAQ from dataq? That can be the the best way to reach the big plant efficiency. Imagine of a pH control at ±0,1 and a cell steady at the best temperature, it is also possible to get a control on the chloride concentration (adding the salt during the process)

The real joy would be to have a true pH controlled system, but the theory of pH electrodes, the nature of the electrolyte, and the fact that they go bad just sitting on a self for a year, even with the tip immersed in pH probe storage solution, tells us that their lifetime in a cell would probably be measured in hours.

Tentacles found a very specialized pH probe that was GUARANTEED not to be poisoned - it was a true revolution in technology - but the cost was something like $900. Just not practical for a few Kg of oxidizer.

The data acquisition stuff amplifies and outputs typically 0 to 10V for the basic parameters; voltage, current, and temperature. The first two are set at the power supply. Probably the only truly useful analog output would be temperature. It could be used to trigger external cooling devices like fans, or possibly even set up to slowly increase current until a certain maximum is reached, either T or A, and then control that for a constant temperature run, which would help in determining end-of-run conditions, since we have learned that power requirements vary wildly with the temperature of the cell.

It is going to require a very close look at the data (V and A) to see if there is a usable correlation between the two. It might be possible to incorporate the temperature as part of a mathematical equation and from there calculate (roughly) the remaining chloride.

[bikemaster]

900$ for maybe 6% or 7% of increase in efficiency don't seem to be very pocket friendly...
I think that the best wait for us to know the HCl need of the cell is to make a plot of the HCl consumption related with the chloride level of the cell, which can be roughly find by the voltage/amp/temp relation.
The probleme is that all of those calculs need to be made during the acquisition. I don't know how your program is working, but if it can make all of those calculs and ajust the timer (for the HCl), it can be a very good way to make a really good and accurate pH control without a pH probe.

[patsroom]

Swede,

I see that it would be hard to adjust the concentration of the HCI as it is being introduced into the Chlorate Cell by a dose meter. It may be able to control the concentration with a gravity flow system such as the design in the PDF download below. It is a simple enough solution to add water to the concentration at varies time to decrease the percentage of the HCL acid. As you can see the starting HCL solution would be at its maximum until it began to go lower than the first water flow inlet. (The tank is sealed and has only one opening to allow air to enter the tank as the water empties). The solution would lose strength as it continue to lower until the first holding tank for the water was empty. The solution would then stabilize at that concentration until it reached the next water flow inlet and again would ramp down in concentration until that hold tank is empty. By using a siding math scale one would be able to have the concentration decline at a rate that would be appropriate for the pH balance at the desired intervals. It would be possible to get very close to the desired pH balance and hopefully help you in your quest for a perfect Chlorate Cell.

Attached Files

•  Dose_Meter_Fluid.pdf   9.6KB   23 downloads

[bikemaster]

The idea off getting the concentration of the HCl can be a good way to calibrate the pH, but can the HCl climb into the water??? If yes, after some time the concentration will the same everywhere...

[Swede]

Pat, that is really very clever, and well-presented. Most timers that I am aware of, at least the inexpensive ones available to hobbyists, don't allow advanced programming to vary the delivery over a period of days. They would normally require manual intervention at periodic times to slow the HCl delivery.

Your concept has me thinking... if you know your cell volume (of course you do) - and you know the ampere-hours that will be required for transformation, within 15 to 25%, you might be able to get away with a SINGLE water cell above the acid. Picture one water cell above the acid, with a delivery tube (I'd use a section of glass pipette with a narrow bore, so as to minimize transfer of acid until the level is truly below the tube) and with the tube end 1/3 below the top of the reservoir. During the critical initial phase, the system draws pure acid. The acid then reaches the tube level. Each additional dosage pulls more fresh water into the acid vat, gradually diluting. Towards the end of the run, you are probably delivering acid that is diluted by 3 to 5 times, and that will vary with the volume of the water in the water reservoir.

I like the idea. The only two issues I can think of... the mechanical setup will be challenging, but not horribly so. The acid vat needs to be vented, and given the corrosive nature of HCl fumes, a tiny hole at the top would be best, maybe 1/16" or 1mm or so. The hard part would be the water sub-tank. It would have to be absolutely air-tight or the water will flow into the HCl before the acid level falls below the tube. Further, the tube bore needs to be wide enough to allow water delivery at the correct level, but not so wide that water and HCl would mix excessively prior to that point. Since the specific gravity of water is well below HCl, the tendency to mix would probably be minimized.

But all this (mechanical stuff) is not insurmountable. Perhaps there are other means to automatically dilute acid delivery over a period of days... or automatically reducing the VOLUME of acid without user intervention. Thank you for a great idea.

Edited by Swede, 02 December 2009 - 11:04 AM.

[patsroom]

Hello Swede,

Thank you for the nice words.

I hope that the given ideal above is of value to you as I wish to help you in your hard work in the development of your (pre)chlorate cell. There are so many things that one must think about when trying to make a (pre)chlorate cell. I found that your blog that you have spent so much time writing, very helpful and I hope that the design would just return a small favor of saying Thank You for your work.

I wish to be a part of the solution and not part of the problem.

Pat

I have been working on a Dosing Delivery System that would use a homemade solenoid. It seems that it would be possible to inject as much or as little a dose as one would like. If you would ever like to see the initial concept I would post them for you.

Edited by patsroom, 03 December 2009 - 12:40 PM.

[Mumbles]

I just wanted to point out that you guys make this forum worth running. This community is probably going on 10 years old. I have been involved for the past 8 or so, and running it for the last 6, and never have I been happier with what is going on.

I have some things in mind to contribute soon. Much in the way of dye synthesis for pyrotechnic smoke stars, but we shall see how insane I really am to attempt any of that.

[Swede]

The idea off getting the concentration of the HCl can be a good way to calibrate the pH, but can the HCl climb into the water??? If yes, after some time the concentration will the same everywhere...

Bikemaster, I don't think premature mixing would be a problem at all if the bore is small enough. If you've ever worked with a small glass pipette, say 1 to 2 ml, you'd notice that it takes 5 to 20 seconds just to drain that small volume, but the bore is still large enough to allow free-flow when the acid level drops far enough. There would be a slight mixing, but I could not imagine it being more than 1 to 2%, given the specific gravities involved.

I took some cool microphotographs of my home-brew lead dioxide anode in preparation for its first use, coming in a week or two.
Blog entry on LD anode

Nice fuzzy grain structure! It was very cool to look at the indvidual LD xtals under the microscope:



I hope to have it mounted and running next week. If it fails, I'll probably be forced to take a sabbatical to Cancun or Cozumel just to cry a bit and think about how to fix it. And drink and scuba dive too!