Hello everyone - it's been a long time! There was a period where I was posting a blog almost weekly. Then, I ended up working on projects that weren't blog-worthy. I also need to get my rear in gear for the fourth of July. Last year, I shamed myself with a paltry performance with a few festival balls and such. This year will be different!

I have also been busy welding up electrodes - shameless plug, go to my web page for details on ordering. These encompass all of my experience in making durable and effective MMO anodes. I've also obtained some bulk platinized Ti sheet for creation into perchlorate anodes after the moderately disastrous PbO2 project, which I have not given up on, but I do need some perchlorate via a process that I know will work.

The original T-Cell was a 2-chambered pump system that failed dramatically in its first run, via clogging of the Tygon tubing as crystallization began. I rejected (temporarily) the two-chambered concept, and went back to basics - a big-assed cell that produces 4 or more kilos per run, with few problems.

The original T-Cell crystallization chamber that I turned into a stand-alone cell:

After several successful runs, I tore it down and began modifying it into the ultimate one-celled operation. Some of the problems I corrected...

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• Excess salt creep at certain spots on the lid
  
• An HCl delivery system that relies on a dosing pump; overly complex
  
• A liquid level sight glass that worked until it jammed with crystals
  
• Most annoying of all was that the air pump, used for ciculation, would also jam with crystals
  

The first was corrected by simply adding four more 316 SS studs to clamp the lid more evenly. The lid is gasketed with a 0.234" Viton cord, and Viton has proven itself to be 100% compatible with the cell chemistry... no degradation.

The second improvement - the HCl dosing pump worked, but delivery of the HCl was rather coarse, and during idle moments, the delivery tube gathered gas, and pushed the HCl back along the delivery tube (Tygon), so that when it started again, based upon my precision timer, much of the initial pumping delivered gas only - thus, HCl delivery was more hit or miss than I wanted. I swapped this system with a gravity-fed setup. The HCl vat is positioned one meter above the cell, and the delivery tubing is attached to a surplus PTFE-bodied solenoid valve, which is activated by the same precision timer I had created for the original pumped system. From there, it is routed into an AALBORG PTFE needle valve which meters the otherwise aggressive flow. This system provides excellent and accurate HCl delivery.

Acid additions are crucial if you want your efficiency to crack 90%... otherwise, with no pH control, the best you will achieve will probably be 60% at best. Probably lower.

After passing the solenoid valve and needle valve combination, the HCl (1/2 dilute) is routed into a simple CPVC pipe with cross-drilled holes- the HCl diffusion tube inside the cell. This minimizes pH spikes, as the acid is forced to diffuse through the holes into the bulk of the cell contents. The HCl system is to the left in this picture, with the solenoid above the needle valve. The solenoid was an eBay score at maybe $10, and the valve (unfortunately) was purchased direct from Aalborg. Probably about $65, but it can be used for any number of aggressive chemistry experiments that require precise metering of caustics.

For checking on the liquor level, I went simple rather than complex. Consider a soda straw in a coke. If you close off the end and elevate it, it will retain the liquid. I did something similar by cutting and flame polishing an old pipette. By fingering the top and elevating, I can check liquid level by simply examining the pipette scale. There is a PTFE collar mounted on it to both seal the cell a bit and retain consistency.

Finally, the last problem - circulation. It is possible to use the hydrogen bubbles created at the electrodes to enable a limited circulation in the cell, but even with the best of setups, such a circulation can be utterly lost inside a huge cell. I decided to go with mechanical stirring.

There are two problems with this. First, if you buy a mechanical stirrer, be prepared to spend more money than you'd probably want. Second, the interface between shaft and cell lid must be reasonably gas tight, or salt creep will be a real problem. Yet it must be loose enough to allow free-turning.

I decided to make use of a surplus 24VDC motor. To that, I created and added a stainless collar, a PTFE shaft, which was mated to a PTFE bearing that was pressed into a male, threaded PVC fitting. The teflon shaft was tapped at the end for a 10-32 titanium bolt. A simple paddle was created from titanium sheet and secured with the bolt:

In place on the cell lid, using a PVC construct bracket:

It is critical, if you want to replicate this, that the motor be powered with a variable supply, and it must be fused. If the shafting galls, binds, or salts up, the current will soar and blow the fuse rather than the motor. This is infinitely preferable to waking up one morning and finding your motor a smoking wreck, or even worse, a fire breaking out.

So, from left to right, we have the HCl system, the mechanical stirrer,, and the ventilation tower. On the latter - I have learned from experience that misting, condensation, etc, will rapidly climb a narrow tube, only to be ejected at the end of your vent tubing. A narrow vent system also increases back-pressure into the cell, increasing salt creep, which can be a real annoyance.

Finally, I added a viton gasket to the anode shank clamp. Previously, chlorine gas had leaked upwards and severely pitted the aluminum shank clamp. Hopefully, the viton will prevent this. I also added a heavy heat sink onto the shank clamp.

On the business side of the lid, I am using dual Ti cathodes surrounding a single anode, which is swappable between MMO and any anode compatible with perchorates.

Above the electrode sandwich is a PTFE thermowell for temperature measurements, while to the lower right are the HCl diffusion tube and the mechanical stir paddle and shaft. Note the bleaching of the gray PVC sheet. While the color has changed, the plastic is, in itself, still structurally sound.

I need to calibrate the gravity HCl system to determine volume delivered, but otherwise, T-Cell III is ready to go! I am also in communication with an individual who is making an enormous 2-chambered system that will make use of a crystallization chamber that measures 4 feet by 2 feet in size! Plumbing between the electrode chamber and the crystal collection vat will probably be 1.5" or 2" PVC pipe which will prevent any premature crystallization. I am nagging him a bit to provide photos and details. We shall see!