How we refine silver without cement silver or silver shot
- Thread starter jeff@performance-construc
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As a general rule we don't purchase any hollowware especially anything that is weighted. We only process knife handles and hollowware that has been split open and the weighted materials removed. Then we clean as regular scarp silver.
Yes, this the way to go we also use a shredder we have started using the clean shredded scarp silver to compress our anode bars in hydraulic press at 150tons and then going directly to refining. So there zero heat and or flames used in the anode bar process. And the compressed bars work exceptionally well for refining. Believe it or not this very easy and much faster than melting scarp silver.
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I like the fact that you are using equipment that is "outside the box" for typical refiners. The burnishing mill and 150 ton press hints to me that your primary business is not refining but you have devised excellent methods to utilize some of the equipment you have.
The shredded silver scrap has to be very clean to be pressed into anodes as you would otherwise experience layers where conductivity suffered in the pressed together surfaces of the anodes. And the interface between .925 material and .800 material may suffer.
Do you ever experience passive layers of anodes when unloading the remnants of dissolved anode material processed this way? When the anode system is either shot or bars, the anode material is homogeneous throughout, I am curious if your pressed anodes suffer from lack of homogeneity.
The shredded silver scrap has to be very clean to be pressed into anodes as you would otherwise experience layers where conductivity suffered in the pressed together surfaces of the anodes. And the interface between .925 material and .800 material may suffer.
Do you ever experience passive layers of anodes when unloading the remnants of dissolved anode material processed this way? When the anode system is either shot or bars, the anode material is homogeneous throughout, I am curious if your pressed anodes suffer from lack of homogeneity.
Yes, we do things that are a bit different but that's the fun part of all this especially when you discover something that actually works. At the end of the day that's all we do is refine and mint our own AG and AU. We also have an eBay store where sell all the silver that we feel is too nice to refine. Currently we are working on granulated. and pressed anode bars as well. (so, it's all a work in progress). When the shredded or granulated bars are cleaned and highly compressed, they work extremally well not much different than a melt anode bar and better than making and using shot. I am attaching a photo showing a compressed shredder bar vs two granulated bars one compressed at 140 tons and the last one compressed at 180 tons. I know it sounds crazy but the next step for us is to compress and stamp the final refined bar which we are already working on right now.
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Very nice, compressed refined Silver needles should produce an interesting looking bar. At 150-180 tons of compression I assume a malleable metal like Silver will remain together well and allow for your minting marks to be pressed in.
One last question, the stainless steel bowl concept of Silver Thum cells is relatively new. And at 19 liters you are using rather large bowls. How long can the cells run before the Silver needles grow enough to short out the cell? Can you run at full power overnight or over a weekend?
One last question, the stainless steel bowl concept of Silver Thum cells is relatively new. And at 19 liters you are using rather large bowls. How long can the cells run before the Silver needles grow enough to short out the cell? Can you run at full power overnight or over a weekend?
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What about other metal as Pd, Pt, Au which may stay in anode slimes? You got any or your scrap sources dont have that metals?
One of the nice things about Thum cells is the ease of collecting anode slimes, you don't have to suck them out of the anode bags, you simply remove the anode fabric and burn it, pyrolytically, to reduce any metals before ashing it. That will put all of your PM's in one place to refine when you accumulate a sufficient quantity.
The cells typically run 15 days. They run at 3.5 volts all the time and after 7 days or as we see a voltage drop, we gently push the silver crystals to the side, or we harvest some of the top crystals to allow more growth and prevent the crystals from shorting out at the basket.
Wanted to share some photos that show several ways we clean refined silver. It's really fast and the refined silver comes out ultra clean without using any hot water. We no longer dry any of our cleaned materials with any kind of heat, just a fan on a sloped surface.
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This is how I like to set up rinsing because it saves on waste. The cascading rinse system is the same as systems used by electroplaters to get quality rinsing with much less water. The first rinse is the dirtiest rinse (however the contaminants are only what is in the electrolyte) then they proceed to the final cleanest rinse. Each time a basket of Silver needles is submerged it is lifted (by the hoist) and allowed to drain. Then it moves along to the next rinse and again dipped and drained until it reaches the clean rinse at the end. As water is used from the dirtiest rinse it is replaced with clean distilled water in the cleanest tank. The "dirty" rinse is used for make-up of new electrolyte and to replace evaporation. By heating the cells, a balance of water usage can be achieved to eliminate any waste water from rinsing. The first picture is the system set up new and the second is it working (actually from a security camera)
A spin drier is used to dry the rinsed needles because it spins off any clinging liquid which increases the purity.
A spin drier is used to dry the rinsed needles because it spins off any clinging liquid which increases the purity.
Your entire process is interesting but I have 1 question. When a bowl's electrolyte is loaded with copper, you change out the electrolyte. Now you are left with solution with Silver Nitrate that has to be recovered. This threads title suggests you do not cement the Silver, how do you recover it?
We do recover the silver. So, the pictures I sent where just how we clean the silver taken directly out the cell which takes about 2 minutes per 25 lbs. of silver.
To process the used electrolyte, we first run it through a 30-gallon tank with variable speed rotating 6" x 15" copper tubes to cement out the silver, then the cement silver is washed and dried. The rinse / wastewater is then neutralized and filtered through resin tanks and recycled back to 0 TDS (distilled water) which we continually reuse. For us the process is very fast, and we end up with zero disposable waste. It might sound a bit quirky, but this process seems to work very well for us so far.
To process the used electrolyte, we first run it through a 30-gallon tank with variable speed rotating 6" x 15" copper tubes to cement out the silver, then the cement silver is washed and dried. The rinse / wastewater is then neutralized and filtered through resin tanks and recycled back to 0 TDS (distilled water) which we continually reuse. For us the process is very fast, and we end up with zero disposable waste. It might sound a bit quirky, but this process seems to work very well for us so far.
Are the resin tanks changed out often? They get loaded up with both Silver and Copper and either need to be back-flushed and eluted or replaced. And do you pass your spent (after cementation) electrolyte through a resin column or treat it some other way?
