Non-Chemical Heat control in an electrolytic cell

[bswartzwelder]

Because of the number of references to it on the forum, I know heat buildup becomes a major issue in electrolytic cells. Some have even mentioned an external ice bath or cool water circulating through tubing in a cell to keep the heat down. Both of these are really bad ideas because of the catastrophic results of mixing water or ice with concentrated sulfuric acid. However, I see no reason why a Peltier cooling unit could not be used. Take a sheet of copper which is tall enough to extend well above the top of your cell and mount a Peltier unit on it where it is well above the acid level. Place the copper sheet with the Peltier unit between the copper basket and the side of the glass cell, or between the lead cathode and the glass side of the cell. The power applied to the Peltier unit does not flow into the copper sheet. Copper sheeting would be used because of its great thermal transfer rate and the fact that it has good resistance to sulfuric acid until the temperature gets too high. I have seen Peltier units for sale at MPJA.com (Item 30207 PM) for $5.95 each and they can pump up to 90 BTU's of heat energy. They run from a 12 VDC power supply, so they could be connected to your battery charger or power supply. Could this possibly work? I purchased a couple of these to play with years ago and when power is applied, one side gets hot and the other side gets cold. Reversing the power leads reverses which side heats up and which side gets cold.

 

[NobleMetalWorks]

Electrolytic cells that can operate 24/7 do not have overheating problems.

Sulfuric stripping cells commonly used by hobbyists and refiners on a small scale, can and do generate heat to the point where if you continue you run the risk of dissolving other metals.

At the cut off, where it becomes inefficient to use a sulfuric stripping cell as opposed to other recovery methods, is about the same point you would be heating too much to continue processing your material. In other words, there are better ways to process large amounts of material than in a sulfuric stripping cell. It becomes less efficient as the quantities of materials increase.

So to spend the time, effort and energy to create a way to cool down a sulfuric stripping cell would probably not be worth the money. It might be interesting to create as a hobby project, but would be of little actual practical use.

Your system may have other applications, such as cooling liquid used in a condenser, or in other reactions where the exothermic reaction could case thermal shock, or maybe in a cold finger application. It might be worth investigating any number of applications.

And please don't get me wrong, part of the reason I love this forum so much is all the new ideas for applying different types of technologies, I find it fascinating. But so far as being a viable and cost effective solution, strictly from a business point of view, it wouldn't be worth the effort.

Scott

 

[goldsilverpro]

Keep the current at 5 amps/gallon, or less, and the solution shouldn't overheat.

 

[Harold_V]

So to spend the time, effort and energy to create a way to cool down a sulfuric stripping cell would probably not be worth the money. It might be interesting to create as a hobby project, but would be of little actual practical use.

My experience, back in '75, tends to contradict that comment.

I was flown to New Mexico by a client, so I could witness a water cooled stripping cell in operation. The client desired to have one built.

The cell in question was operated by the government, and had, according to the report I was given, stripped 35,000 ounces of gold the previous year. The cell was water cooled, with a water jacket surrounding the stipping portion of the cell. The water jacket portion was shorter by approximately four inches, so water was not in close proximity to the sulfuric acid. If memory serves, they tried to maintain a pH of 1.68, and used a rectifier capable of up to 300 amps @ 28 volts. As amperage declined, they increased voltage, and stopped stripping when amperage fell below a given point. They considered the items fully stripped when that occurred.

The yard, in the government installation where this cell was observed, was filled with 55 gallon drums of stripped material.

Harold

 

[pgms4me]

Because of the number of references to it on the forum, I know heat buildup becomes a major issue in electrolytic cells. Some have even mentioned an external ice bath or cool water circulating through tubing in a cell to keep the heat down. Both of these are really bad ideas because of the catastrophic results of mixing water or ice with concentrated sulfuric acid. However, I see no reason why a Peltier cooling unit could not be used. Take a sheet of copper which is tall enough to extend well above the top of your cell and mount a Peltier unit on it where it is well above the acid level. Place the copper sheet with the Peltier unit between the copper basket and the side of the glass cell, or between the lead cathode and the glass side of the cell. The power applied to the Peltier unit does not flow into the copper sheet. Copper sheeting would be used because of its great thermal transfer rate and the fact that it has good resistance to sulfuric acid until the temperature gets too high. I have seen Peltier units for sale at MPJA.com (Item 30207 PM) for $5.95 each and they can pump up to 90 BTU's of heat energy. They run from a 12 VDC power supply, so they could be connected to your battery charger or power supply. Could this possibly work? I purchased a couple of these to play with years ago and when power is applied, one side gets hot and the other side gets cold. Reversing the power leads reverses which side heats up and which side gets cold.

This idea does work. I use peltier thermoelectric devices instead of ice baths, however, the copper casing(or sheeting used must be very tight fitting around the glass to efficiently remove the heat. Also the heat being transferred through the peltier device must be readily dissapated on the hot side of the device by use of an adequate heat sink that is fan cooled. My cell does not generate a lot of heat so I use one on the bottom surface only. the peltier devices are fairly inefficient power wise so a small 90 btu one will consume about 6 amps at 12 volts just by itself. I like it because its easier than dealing with swapping between cells. You actually could control cell temperature by connecting the peltier device through a thermostatic control,but you need to insure the sensor used is sealed in lead or something thermally conductive that is not attacked by the Sulfuric. Note: if you reverse the device you can use it to heat things and keep them warm

 

[bswartzwelder]

pgms4me,

Thank you for the confirmation. That's one more tidbit of information to put in my files for future reference. In my idea, the Peltier device would be mounted to a thin copper sheet which could be partially immersed into the cell between either one of the electrodes and the glass side of the dish. Obviously, the Peltier unit itself would have to be well above the level of the acid. Mounting a second copper sheet on the opposite side and using a fan to blow away the waste heat would make it more efficient and help warm your workplace when it's cold. The unit I saw for sale says it draws 6 amps maximum and 4.4 amps at 12 VDC.