Gwar
Well-known member
Great design !
First attempt at silver refining
- Thread starter Gsracer
- Start date
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Thank you GWAR.
@kurtak
Kurt hoping you can give me some insight.
Cells been running for about 6 hours. Electric is holding steading at 3.5V with 6.60 AMPs. Should be close to 150 grams deposited so far, which is what i would previously do in a whole 24 hours. However...
Im starting to get an accelerated growth and the cell is heating up. It is sitting at 110 degrees F. I've noticed in the past when the cell heats up I've had a similar issue with growth too fast. I'm wondering if i do not have enough anode area causing too high of resistance. Or if its something else im missing entirely.
I didnt see you mention concentration of electrolyte
Specs of the cell.
Im at 550g in 3.8 L
Anode to cathode distance 4.5 inches exactly
Cathode area 9"x5.25 = 47.25 sqin
Anode area 1 kilo bar measuring 4.05" x 2.33" = 9.436 sqin. about 1/8 submerged so if you add that area as well we are at 11.01 Sq in
Current pic below
I dropped the voltage down to 3.00 V which is running at 5.5 amps to see if that helps drop the temp a little bit.
@kurtak
Kurt hoping you can give me some insight.
Cells been running for about 6 hours. Electric is holding steading at 3.5V with 6.60 AMPs. Should be close to 150 grams deposited so far, which is what i would previously do in a whole 24 hours. However...
Im starting to get an accelerated growth and the cell is heating up. It is sitting at 110 degrees F. I've noticed in the past when the cell heats up I've had a similar issue with growth too fast. I'm wondering if i do not have enough anode area causing too high of resistance. Or if its something else im missing entirely.
I didnt see you mention concentration of electrolyte
Specs of the cell.
Im at 550g in 3.8 L
Anode to cathode distance 4.5 inches exactly
Cathode area 9"x5.25 = 47.25 sqin
Anode area 1 kilo bar measuring 4.05" x 2.33" = 9.436 sqin. about 1/8 submerged so if you add that area as well we are at 11.01 Sq in
Current pic below
I dropped the voltage down to 3.00 V which is running at 5.5 amps to see if that helps drop the temp a little bit.
Martijn
Well-known member
Limit the current to a maximum, not the voltage!.
The closer the silver grows to the anode, the lower the resistance is between the anode and the silver on the cathode, lower resistance means bigger current.
more current means more power consumption>> more heat.
Set your current to the desired Amps corresponding to the surface of you smallest surface, be it anode or cathode surface.
if the resistance lowers, the voltage will drop because the current is limited.
How to do this: apply sufficient voltage and turn the current knob down. You will see the voltage adjust automatically.
A good indication I use with all electrolytical cells: no bubbles forming>> no excess current. No depletion zones around anode or cathode.
Martijn.
The closer the silver grows to the anode, the lower the resistance is between the anode and the silver on the cathode, lower resistance means bigger current.
more current means more power consumption>> more heat.
Set your current to the desired Amps corresponding to the surface of you smallest surface, be it anode or cathode surface.
if the resistance lowers, the voltage will drop because the current is limited.
How to do this: apply sufficient voltage and turn the current knob down. You will see the voltage adjust automatically.
A good indication I use with all electrolytical cells: no bubbles forming>> no excess current. No depletion zones around anode or cathode.
Martijn.
Makes sense. Thank you Martin.
What should my maximum amperage be? My smallest surface is the anode of course.
What is the formula I should be applying for current density at the anode? Or is it just trial and error on each particular setup.
What should my maximum amperage be? My smallest surface is the anode of course.
What is the formula I should be applying for current density at the anode? Or is it just trial and error on each particular setup.
Overnight, I lowered the voltage to 1.12 to give me 2 amps, the solution cooled to ambient and crystal growth was much more in line with what i expect to see. Regarding the current density.
Found an old thread from GSP on the subject, mentioning specifically the heating issue...
So using GSPs numbers my anode 9.436 sqin x .35 amps/sqin = max amps of 3.30 Amps
Ill try this setting out today and report back.
Starting to sound like i need bigger anodes.....
Found an old thread from GSP on the subject, mentioning specifically the heating issue...
So using GSPs numbers my anode 9.436 sqin x .35 amps/sqin = max amps of 3.30 Amps
Ill try this setting out today and report back.
Starting to sound like i need bigger anodes.....
Martijn
Well-known member
I think the advised current is now 25Amp / square feet, but that could be for one side of the cathode plate.
I just setup a cell and test at which current there are no more bubbles forming by turning it down.
Thats your highest desirable amp setting.
Then its a game of try and see what happens. Slow crystal growth at low amps, thin long hairs at high amps.
It all depends on what you want.
Play around with the current.
I just setup a cell and test at which current there are no more bubbles forming by turning it down.
Thats your highest desirable amp setting.
Then its a game of try and see what happens. Slow crystal growth at low amps, thin long hairs at high amps.
It all depends on what you want.
Play around with the current.
So just to update.
Today I poured a new anode, i upped the area from 9.436 sq in to 12.386 sq in (the biggest mold i had) so i added 30 percent area.
I have experimented with the amperage with the power supply set to limit current.
If i don't set limiting, i can hit 6.72a at 3.51v. However the crystal growth is way too fast with long, spindly crystals. It would short out in no time.
All in all this cell appears to be working twice as fast as my previous one which would max out around 1.4 amps consistently to get nice crystal. Im a little disappointed that i cant turn up the voltage and utilize the amperage available. Open to suggestions...
Pics
I think i found the sweet spot, with current limiting to 3.00 amps at 1.57 Volts. The crystal growth speed is manageable, every once in a while there is an offshoot that i have to knock down but it appears to be making denser crystal. Current density at the anode is .24a per sq in and at the cathode im sure its low.
Growth so far after 32 hours, should be somewhere around 384 grams
At this amperage the cell temperature doesnt go over 95 degrees.
Today I poured a new anode, i upped the area from 9.436 sq in to 12.386 sq in (the biggest mold i had) so i added 30 percent area.
I have experimented with the amperage with the power supply set to limit current.
If i don't set limiting, i can hit 6.72a at 3.51v. However the crystal growth is way too fast with long, spindly crystals. It would short out in no time.
All in all this cell appears to be working twice as fast as my previous one which would max out around 1.4 amps consistently to get nice crystal. Im a little disappointed that i cant turn up the voltage and utilize the amperage available. Open to suggestions...
Pics
I think i found the sweet spot, with current limiting to 3.00 amps at 1.57 Volts. The crystal growth speed is manageable, every once in a while there is an offshoot that i have to knock down but it appears to be making denser crystal. Current density at the anode is .24a per sq in and at the cathode im sure its low.
Growth so far after 32 hours, should be somewhere around 384 grams
At this amperage the cell temperature doesnt go over 95 degrees.
Martijn
Well-known member
Sounds like you found your cell's sweet spot.
To find out what the limit of your power supply is, set the course and fine knobs to maximum and read the voltage with open terminals.
Short the outputs plus and minus with one lead to see how far you can turn up the current. What are the specs? 30 volts at 10 Amps?
To find out what the limit of your power supply is, set the course and fine knobs to maximum and read the voltage with open terminals.Short the outputs plus and minus with one lead to see how far you can turn up the current. What are the specs? 30 volts at 10 Amps?
What you are experiencing is what sent me down the rabbit hole of rotating cathode design.
This was my first prototype. I built a large production model with a wiper blade that i sold to a client. If i can find the old pictures i will post them.
This was my first prototype. I built a large production model with a wiper blade that i sold to a client. If i can find the old pictures i will post them.
Sounds like you found your cell's sweet spot.
Short the outputs plus and minus with one lead to see how far you can turn up the current. What are the specs? 30 volts at 10 Amps?
Martin. Yea it seems like it. The power supply is 30v10a. When I say the previous design which was much smaller by comparison would max out at 1.4amps. I meant it in the sense, all I could run was 1.4a to get dense crystal growth. One thing to note. When I went to bed last night I was thinking back and reviewing previous pictures of the previous design. As It’s been over 6 months since I last ran it, Was that when the electrolyte concentration was fresh. Ie pure. I had a similar crystal growth speed and had to lower the amperage to around 1a till the copper concentration came up a bit. Maybe this will follow a similar trend. I’m probably around 2-4g/l copper by now. Let’s see how it goes when it gets to 10g/l of copper. I know many professionals start out by adding copper. So I guess I’ll see.
Wow. That is cool. I’m wondering if I could incorporate something similar. Would definitely cut down on the constant checking. Maybe not a rotating cathode but some sort of windshield wiper design I can make with a glass rod or the like to go back and forth inside the tank every so often. Should be pretty simple with a bit of tech. I’m a software engineer by trade so that’s more my realm. Thank you. Rabbit hole indeed. Lol.
Just wanted to share, cell has been running for 75 hours. It has digested a little over a kilo of anodes already. Once the copper concentration raised a bit. I was able to get some additions amps into it. I still have to monitor from time to time to make sure it doesn’t short. But it holds steady between 3-4 amps at 1.5-1-2 volts If I turn off constant current and set the voltage to 3.5 volts I get a little over 7 amps. But the cell gets hot and the crystal grows crazy fast. You can watch it.
Copper concentration is right around 5-7 gram / liter.
Crystal growth is pretty dense. So that’s good.
Here’s some pics.
Here is a cool time lapse video with the cell turned up to 7 amps for around 3.5 minutes of time in 38 seconds.
View attachment IMG_7203.MOV
Copper concentration is right around 5-7 gram / liter.
Crystal growth is pretty dense. So that’s good.
Here’s some pics.
Here is a cool time lapse video with the cell turned up to 7 amps for around 3.5 minutes of time in 38 seconds.
View attachment IMG_7203.MOV
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Martijn
Well-known member
Thats very cool to watch it collapse and grow back
Gwar
Well-known member
Great technique !
103 hrs. So far so good. Averaging a little over 3 amps per hour. I turn it down to 2 at night and try to run it close to 4 during the day.
One thing I’ve noticed is the large kilo anodes dissolve from the outside to the middle.
The amperage is steady so it seems the elevated basket design is keeping the slimes at bay.
I can pull the anodes out and they are relatively clean with no slimes sticking to them.
The just fall down into the space between the muslin cloth and the plastic spacer.
One thing I’ve noticed is the large kilo anodes dissolve from the outside to the middle.
The amperage is steady so it seems the elevated basket design is keeping the slimes at bay.
I can pull the anodes out and they are relatively clean with no slimes sticking to them.
The just fall down into the space between the muslin cloth and the plastic spacer.
So i decided to do a harvest today. I was having to go out every hour and knock the crystals down and i didnt want to risk a short through the anode bag at this point.
A small part of the appeal of this setup was i wanted to be able to harvest the crystal without having to breakdown the cell like i would have to do with my beaker setup.
In comes my custom made spoon. Drilled some holes and heated it till it bent so it would fit inside the cell and i could scoop the crystal out.
I was running out of time and had a family engagement so i left them sitting under some distilled water till i can rinse them better and dry them out. Also going to pick up a 3L beaker tomorrow so it will be a little easier. I would guess theres a little over a kilo and a half of crystal in here. But once i complete the run and teardown the cell i will post yeilds.
The whole time i harvested the cell was running, I topped it off with 250ml of electrolyte with another 100 grams of silver crystal dissolved to take account for any depletion. Copper concentration is now around 10 grams per liter. My guess is it will run another 5 or 6 days before the anode bag stuffs up. I should be able to get around 3kilos between breaking down the cell around every 10-12 days. My previous setup would only be able to produce between 1.3-1.5 kilos during the same time period.
A small part of the appeal of this setup was i wanted to be able to harvest the crystal without having to breakdown the cell like i would have to do with my beaker setup.
In comes my custom made spoon. Drilled some holes and heated it till it bent so it would fit inside the cell and i could scoop the crystal out.
I was running out of time and had a family engagement so i left them sitting under some distilled water till i can rinse them better and dry them out. Also going to pick up a 3L beaker tomorrow so it will be a little easier. I would guess theres a little over a kilo and a half of crystal in here. But once i complete the run and teardown the cell i will post yeilds.
The whole time i harvested the cell was running, I topped it off with 250ml of electrolyte with another 100 grams of silver crystal dissolved to take account for any depletion. Copper concentration is now around 10 grams per liter. My guess is it will run another 5 or 6 days before the anode bag stuffs up. I should be able to get around 3kilos between breaking down the cell around every 10-12 days. My previous setup would only be able to produce between 1.3-1.5 kilos during the same time period.
kurtak
Well-known member
Gsracer
Have been following you progress - awesome - sorry I have not commented much (busy with other things)
However I would like to make one comment
I see you are using glass rods to hold up your anode basket --- glass has a tendency to break
I use SS rods to hold my anode basket up - just saying - I would hate to see those rods break - like when harvesting crystals from the cell - as accidence do happen
Kurt
Have been following you progress - awesome - sorry I have not commented much (busy with other things)
However I would like to make one comment
I see you are using glass rods to hold up your anode basket --- glass has a tendency to break
I use SS rods to hold my anode basket up - just saying - I would hate to see those rods break - like when harvesting crystals from the cell - as accidence do happen
Kurt
Hey Kurt. Thank you.
Your absolutely right. When I did it originally I only accounted for a 1kilo anode. With that size it didn’t seem like much weight for the 8mm rods. However as I had to change the anode size mid way. They are now closer to 1.3 kilo size. Additionally I didn’t take into account stacking another one on top when the first one starts to dissolve as I did as well.
It’s a bit much for the glass. When I break it down I will swap out to some 1/4 stainless.
Your absolutely right. When I did it originally I only accounted for a 1kilo anode. With that size it didn’t seem like much weight for the 8mm rods. However as I had to change the anode size mid way. They are now closer to 1.3 kilo size. Additionally I didn’t take into account stacking another one on top when the first one starts to dissolve as I did as well.
It’s a bit much for the glass. When I break it down I will swap out to some 1/4 stainless.
Excellent work. Very pleasant to watch your progress and results.
To the overheating issue, I just add one thing. Amperage = electrons make the silver crystals. Not the voltage. It is very easy to calculate the power consumption. Just multiply voltage with current - and you have the result. There is only certain voltage needed to free silver as silver cations, which will flow through the electrolyte and deposite on the cathode. All "excess voltage" will dissipate as heat.
We try to push the cell to the maximum working speed by forcing the voltage up, causing amps to also ramp up. This inevitably lead to the excessive power consumption, and you can clearly see it as rise in operation temperature of cell. It eventually stabilize at certain temperature - as heat is dissipated from the cell to the enviroment/room etc.
Because there is limited ammount of ions in solution, for shorter period of time we can see conductivity as constant. You can push more amps by ramping the voltage up, but this also cause unwanted overheating and also low current efficiency = bigger electricity bill
As you figured out, simplest way how to get better current density and efficiency is to enlarge the surface area of the electrodes. Sreetips goes with shot - and this obviously help to increase surface area. You can go with casting "plate-like" electrodes. Just don´t fill the mold to the top. Cast for example two 0,5kg bars instead of one 1 kg bar. And then stack these thinner plates bit "diagonally" in the basket, leaving spaces in between them.
Another option would be to cool down the setup somehow. Mount small electric fan to the side of the setup, or put the whole container to the bigger vessel with water - to enlarge heat dissipation surface.
To the overheating issue, I just add one thing. Amperage = electrons make the silver crystals. Not the voltage. It is very easy to calculate the power consumption. Just multiply voltage with current - and you have the result. There is only certain voltage needed to free silver as silver cations, which will flow through the electrolyte and deposite on the cathode. All "excess voltage" will dissipate as heat.
We try to push the cell to the maximum working speed by forcing the voltage up, causing amps to also ramp up. This inevitably lead to the excessive power consumption, and you can clearly see it as rise in operation temperature of cell. It eventually stabilize at certain temperature - as heat is dissipated from the cell to the enviroment/room etc.
Because there is limited ammount of ions in solution, for shorter period of time we can see conductivity as constant. You can push more amps by ramping the voltage up, but this also cause unwanted overheating and also low current efficiency = bigger electricity bill
As you figured out, simplest way how to get better current density and efficiency is to enlarge the surface area of the electrodes. Sreetips goes with shot - and this obviously help to increase surface area. You can go with casting "plate-like" electrodes. Just don´t fill the mold to the top. Cast for example two 0,5kg bars instead of one 1 kg bar. And then stack these thinner plates bit "diagonally" in the basket, leaving spaces in between them.
Another option would be to cool down the setup somehow. Mount small electric fan to the side of the setup, or put the whole container to the bigger vessel with water - to enlarge heat dissipation surface.
