# Chain impact mill



## kjavanb123

Hi

I finally delivered my latest milling equipment. The design was initially copied by the membets of treasurenet forum which I should thank.

The electromotor used is a 1.5 HP 3000 rpm single phase. The pulley system used increases the mill rpm more than 3000 rpm.



The main shaft used is a 20mm diameter, and 3 sets of modified chains are attached to shaft with screws so chain replacement is easy. As it can be noted, unlike the designs by treasurenet members, I used a length for chains that when it is running, only 1-1.5mm gap is left to the body of mill.

Output holes are 5mm in diameter. This pulverizes rocks into 93% passing mesh 100, and for circuit boards 90% passing mesh 100.



It literally instantly pulverizes rocks or circuit boards into fine powder. Here is an example when I dropped a closed feast size hematite ore into the mill.



I will be using this mill to pulverize left over depopulated circuit boards, then run them on homemade shaker table to recover copper.

Best regards
Kj


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## goldandsilver123

Very good!


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## kernels

Agreed, very nice KJ, thanks for sharing. A few more pictures of the various parts would be great, looks like I have another project to do . . .


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## snoman701

They work great but the dust is horrible. I taped a plastic bag to the output and then bungee it to the collection can. Even then I have to wear a respirator.



Sent from my iPhone using Tapatalk


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## kjavanb123

Goldandsilver123
Thanks for your kind words. I shall thank Treasurenet forum members for main concept.

Kernels,
Thanks for your comment. I will take more photos of inside and outside and post them along the dimensions.

Snoman
Indeed at 3000 plus rpm the dust is crazy, I use 3 bucket system, their caps are sealed using tapes, and output is connected to first bucket, an output connect the first bucket to second bucket and same goes to third bucket and last pipe exit the last bucket to a bag.

I will run a test with the dust control system and post more photos.


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## kjavanb123

Dust control using a bucket and woven bag as cap for the bucket, and output from mill is inserted to woven bag and in the bucket.

The door which is screwed to mill, used glue to seal.

Ran few pieces of cut circuit boards and no dusts were visible. So it seems to be working.



More detail photos of inside and out of mill tommorow.


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## mls26cwru

please be careful and stay on top of that dust control system and do whatever you can to keep it in tip top shape... I got word of a company around here that was shut down recently because they were grinding PCB boards without use of a fume/dust control... everyone of their employees got lead poisoning.


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## 4metals

There is a company in Connecticut that makes customized dust control sleeves out of any type material you need. A great option for controlling the path the dust can fly between the mill and the drum. I always said as a refiner what you make for a living is dirt and if you are doing any production milling you know what that means, it goes everywhere! Check out Siftex,https://www.siftex.com/ they can help you put the valuable dust where you want it.


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## kjavanb123

4metals
Thank you for the link.

Kernels,
Here are some more photos of inside the mill eth their dimensions.

The chains are 132mm when standing, and screwed to plates which are welded to shaft.



And here is how they are attached,



Here are the output holes, 5mm in diameter. I am going to use water jet and do these holes at 0.1mm that would be really fine powder.



Here is output of 1kg of circuit boards that was ran in the mill. Noticed the mill does much better job pulverizing hard quartz than does circuit boards.



And lastly some of the copper panned from the mix above. More on that subject once they dried and weighed.



Best
KJ


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## philddreamer

Very nice, KJ!
What size pipe is the main chamber?
I have a piece of 16 inch round tube, 3/8 in. wall 11 inches long... I think it will do the trick! :mrgreen: 

Thanks!
Phil


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## kernels

Hi KJ, how does the front 'lid' work ? Is there another bearing that supports the shaft ? Do you remove the front lid every time you want to clean it out ?


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## kjavanb123

philddreamer said:


> Very nice, KJ!
> What size pipe is the main chamber?
> I have a piece of 16 inch round tube, 3/8 in. wall 11 inches long... I think it will do the trick! :mrgreen:
> 
> Thanks!
> Phil



Hi Phil,

My main chamber is 280mm in diameter, 8mm thick wall, 130mm lentgh of the main pipe.

I think 3/8 inch wall may be too thin as the main chamber, takes beating. I noticed that when I dropped a sample of limestone, there were fine pieces of iron cut from the body or chain and showed up in the powder.


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## kjavanb123

kernels said:


> Hi KJ, how does the front 'lid' work ? Is there another bearing that supports the shaft ? Do you remove the front lid every time you want to clean it out ?



Front lid is rarely open, because when testing the mill I noticed there was zero of materials left in the mill. 

There is a bearing on front lid which is screwed to a "L" shape iron piece welded to the lid.

Based on couple experiments I noticed some iron is eroded from either body or chain and end up in output. So maybe using a hard steel would be better choice for main chamber and chains.

Here is the final shot of copper recovered from 1 kg of circuit boards, pulverized by the mill and panned out.



Copper collected from 1 kg of circuit boards



I will pyrolize this copper as it has some pieces of boards, smelt it to find the final weight of copper from a kilogram of circuit boards.

I also check the tailing from panning to see how much copper ended up there.


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## kernels

Nice KJ, appreciate your posts, always love seeing your DIY machines.


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## nickvc

Nice Kevin.
Are you going to run the copper through a cell or sell as is? I’m asking because I suspect the values have been removed but the copper may well have contaminants from the solder.


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## kjavanb123

Kernels
Your welcome. Glad my post can help.

Here is a circuit board I cut to run in the mill and observe its output;



Cut into smaller pieces so it fits the feeding shute,



I ran the piece with big IC and the one with two connection ports on it, here is the result not sifted yet,



Panning not-sifted pulverized board,



Here is final clean up pan, as you can see the heavy gray materials possibly solders follow that copper and lighter materials at the bottom, could not see any visible gold but I will dissolve in acids to see if gold was recovered,



Learned from this experiment I need to cut the holes to 0.2mm instead of 5mm they are now to liberate gold.

Best regards
Kj


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## kjavanb123

nickvc said:


> Nice Kevin.
> Are you going to run the copper through a cell or sell as is? I’m asking because I suspect the values have been removed but the copper may well have contaminants from the solder.



I will try to dissolve a sample from it in hcl to see if it can remove solders, then market it as fine powder as price for fine powder is higher locally than melted copper.


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## 4metals

Nice piece of equipment, what would you estimate the weight of boards that could be fed into this mill per hour?

And how noisy is it while operating?


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## snoman701

Very very noisy! At least the one I use. 



On addition - ever hit a rock with the lawn mower? 

Just imagine it never leaves the deck, and bounces around until it's ground very very fine.

Sent from my iPhone using Tapatalk


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## 4metals

I know it's noisy, but a steel ball mill with 3" steel balls isn't exactly quiet either. I just would like an idea if it's noisier than a ball mill if he has the two to compare noise levels.


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## snoman701

4metals said:


> I know it's noisy, but a steel ball mill with 3" steel balls isn't exactly quiet either. I just would like an idea if it's noisier than a ball mill if he has the two to compare noise levels.



Tough call...I'd say it's a different noise.

Looking at his design, there's some very specific things that I'd do to reduce the noise. One is increase wall thickness to 1" on the impact faces using at least AR400 steel. The chain should be the consumable, not the walls. Then I'd increase the thickness of the front and back face to at least 1/2". 

Efficiency can be increased by using an octagonal shape instead of round. It will force grinding, instead of having pieces get spun around. 

The design should be three bearings, not two. One inside, one outside, and one further out where it attaches to the motor. It will reduce vibrations. The front face encapsulates it, instead of having a hole. Get the whole thing sprayed with rhino lining following that.

No welding on the shaft, just get a piece of 4" diameter piece of steel, have someone drill a 1 1/2 hole for the shaft (and key it). Diametrically opposite positions on this, cut a slot for your chain. Then drill the holes for bolts to hold the chain in. 

The goal is just to reduce ALL vibration except the grinding. That's where the noise comes from. Heavier it is, the quieter it will be. Steel is cheap. 

Give up on the granulator?? I've wanted to buy a small one.


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## kjavanb123

4metals said:


> Nice piece of equipment, what would you estimate the weight of boards that could be fed into this mill per hour?
> 
> And how noisy is it while operating?



I have not measured the throughput yet, but by just visual observation, it takes longer to mill circuit boards either depopulated or as whole, than it does quartz ore.

Had I chose a 3HP or bigger motor, it might had decreased milling time.

As for noise, it is noisy, using 12mm thick chamber would decrease the noise.


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## nickvc

Kevin you could wrap it in thin polystyrene sheet to deaden some of the noise but if it’s away from people the noise will not really matter.


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## Smack

I would say the chain/hammer mill is slightly louder. If I'm going to be in my shop when the ball mill is running, I will put a large cardboard box over it. The 5 layer gaylords really quiet it down.


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## kjavanb123

Smack said:


> I would say the chain/hammer mill is slightly louder. If I'm going to be in my shop when the ball mill is running, I will put a large cardboard box over it. The 5 layer gaylords really quiet it down.



Thanks for the tip. I will try this out.


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## kjavanb123

All,

Here is some update on results for running and panning depopulated and whole circuit boards.

After running a kilogram of depopulated circuit boards mostly motherboards, in my hammer mill and pan copper, dissolved it in hydrochlorid acid to clean any solders, incinerate it and will melt tommorow so I can find copper recovery rate for this chain mill.

I also ran 4 chips as can be seen from picture below, 



Panned the result and dissolved in hcl to remove any ferrous or tin, incinerated, follow dissolution in nitric acid, after some shaking the pan, the gold bonding wires show up,



Here is a close up,



My next experiement would be manually depopulate a kilogram of motherboards, smelt the components and record the amount of gold, silver and palladium recovered,

Then take another kilogram of similar circuit boards and run it in mill, sift and run the result on gravity separation equipment, and recover gold, silver and palladium from concentrated.

This experiement will assist in finding out milling vs smelting recovery rates.


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## Shark

Great job, I love seeing your equipment and how you work to make it all come together.


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## kjavanb123

Shark,

Thanks. I enjoy your post specially about copper electrolysis.

Today I melted down incinerated copper powder from milling and panning exactly 1009 grams of depopulated PCBs.

My furnace insulation was broken so melt did not complete, but over all 210 grams of copper was recovered.



And some left over that did not pool,



I will re melt these to get a solid copper bar to have final amount of copper recovered from a kilogram of depopulated PCBs.

But 21% copper from depopulated board seems about right.

Best regards
Kj


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## 4metals

> But 21% copper from depopulated board seems about right.



That fits right in with the 15 to 20% average copper content I have experienced. So this mill actually allowed you to skip the incineration step and go right to powder and metallics. I would bet the powder, if incinerated and fire assayed, would be holding values as well. It would be interesting to process a large enough batch and assay the fine powder.


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## kjavanb123

4metals,
My main goal was to skip the pyro and incineration steps, if I change my mill output from 5mm to 1mm or even 0.5mm the finer the result would be hence more copper recovery.

As far as values I highly doubt they do have any, as these were already depopulated and processed for values, what I ran for copper recovery was just bare boards with some solders on them which I cleaned by hcl.

My crucible broke upon re melting, but copper fine melted. I let them cool so I can weigh it and have an assay.


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## 4metals

The boards you cut up to fit into the feed chute weren't totally depopulated, the good stuff was gone but there are likely values from fingers. I would think a mill like yours with larger holes would pass the metallic fraction easier and faster, then sifting is a quick and inexpensive way to get the metallics for smelting. If you had solder joints they could possibly have been soldered to a gold plated hole in the board and removing tin with HCl would take the gold stannate as well but if the solder was left in and the molten copper air sparged, you would upgrade the copper and leave just copper and PM's. Plus an acid step involves an entire environmental issue as well as handling. I'm a fire guy! 

My thinking is to minimize the manual depopulating to the easy picking parts and knowing any remaining PM's can be recovered. Then a second mill with very fine mesh on the discharge will yield fine powder which can be sampled and assayed. You may be able to ship the powder once or twice but the refiner will figure out that it is still unburned circuitry and make you burn it. But from experience with powders from motherboards, they do hold values. The prospect of processing them without pyrolysis or incineration is intriguing. Without the incineration process I would think the fire assay would be very challenging to reduce.

Here in the US, the scrubbing of a smelt operation on the copper is very do-able but the burning is what the EPA doesn't really care for. The labor to manually depopulate is costly in the US but if it can be limited to easily picked components it isn't as costly if the remaining powders and copper recovered this way can be "mined" for their copper and PM values effectively. The potential of this approach is worth discussing further.


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## IdahoMole

Thanks Kevin for showing us the build and use of your mill, it is very interesting. 4metals got me thinking this morning, if the burning of the boards can be eliminated it would remove a huge obstacle for myself and probably many others. 
Let me think out loud for a moment and see if i am understanding the theory. I could take populated boards and mill them, concentrate the material with a sluice or blue bowl etc., smelt the concentrates, pour impure copper anodes for a copper cell and process the resulting slimes for PM's?
This is all theory for me because i have no hands on experience with this particular process but the threads on smelting and copper cells have intrigued me. I did build a furnace this winter with the intention of trying my hand at smelting and now that the weather is beginning to warm up a bit i am getting excited about getting into the lab. I would like to build a copper cell soon. 
I will be watching this thread and i appreciate everyone's comments.


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## kjavanb123

Idahomole

Thanks for your interest. I have already done a similar project with Mt Baker Mining And Metals company, where I sent them pulverized populated circuit boards and they ran it on their shaker table and assay the concentrates.

If you have not seen the thread about, please let me know so I can put it here, there is whole discussion about assay results and recovery rate.

In my opinion milling sifting then gravity separation following smelting and sparging to get 99% copper with all the PMs would work instead of pyrolysis and incineration.

The mill I built would pulverize the populated circuit board, about 90% of it pass mesh 100, and 10% over size, which can either be pyrolized or I am thinking ball milling.

Soon I will do an experiment to see how efficent this milling and separation process is, by depopulating and lead smelting 1 kg (~2lbs) of identical circuit boards, and process the same 1 kg circuit board using milling spearation and copper smelting.

I will try to post that here as I am currently shrdding my left over depopulated boards to pulverize and separate copper.

Best regards
Kj


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## 4metals

Back in the day I incinerated boards and crushed the burnt remains and sifted off the metallic fraction. The metallic fraction was passed over with strong magnets to remove any magnetic material and the rest was copper, solder and PM's. The boards we received in had their heat sinks and batteries and, in some cases, even processors removed before we got them.

The copper fraction as we called it was smelted and oxygen sparged to slag off just about everything but copper and the PM's. Then we, at first, assayed the bars and shipped them to a copper smelter and were paid on copper and PM's. Eventually when the feed was consistent we began to run copper cells. 

The powder was sifted to a -60 mesh. As a fine powder it could be sampled and shipped to a refiner in Europe who processed sweeps. The only difference I see here is the powders Kevin is producing have never been incinerated so they will not perform the same as incinerated powders and the end refiner will likely balk. Since the boards we burned had visible values on them, fingers etc., we knew some of those values would end up in the fines. But the trade off is the labor to snip off everything of value is huge, unless labor is cheap.

An option to recover the values from the powders may be to leach out the values in a Deano-ish style leach circuit. I still think there will be difficulty fire assaying the unburnt powders but since they can be sampled efficiently because of their particle size a small sample can be incinerated just to simplify the assay process. 

It is an intriguing prospect, just because the incineration process is so onerous. Eliminating it entirely is, well, intriguing!


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## snoman701

Intriguing, yes, but is it viable on the large scale? 

You've said yourself, you are a pyro guy. When you compare the efficiency of the pyrometallurgy process, on a large scale, do you really think it's reasonable to try to shred/mill/concentrate the stuff? 

I can look at a lot of boards and say, "yeah, that's going to refine at $10 a lb, and I'm only getting $5", but even at $5 a lb gross profit, I'd have to refine 20,000 lbs of that board before I can pay the startup costs on a very lean professionally set up line to shred, mill, concentrate, smelt, refine. That's a huge undertaking. 

I don't mind dealing in e-scrap, but at the end of the day, it still seems that the best thing to do is simply sell it upstream. I guess if I was already dealing in loads of weird, high yielding telecom, there might be a niche where the refining costs will support an operation such as this, but then I question if you could find the quantity of this product to make such an operation profitable. 

But then, the above could apply to just about any business proposition.


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## rickzeien

Here is an interesting paper on PCB pyrolysis in molten salt. 

May not be viable on a small scale but I wonder how the EPA would view this process. 

https://www.sciencedirect.com/science/article/pii/S2215016115000138

Sent from my LG-H872 using Tapatalk


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## 4metals

> When you compare the efficiency of the pyrometallurgy process, on a large scale, do you really think it's reasonable to try to shred/mill/concentrate the stuff?



To even begin to start the pyrometallurgy process you need incinerate, crush and sift to get the material to melt. To use Kevin's method you would need to shred, and sift to get the material to melt. 

Incineration is expensive between air permits and buying an incinerator. Entry level small incinerators go for $20K just for the unit, not talking stacks and permitting. 

Chain mills (I have since looked them up after reading this thread) are available for $5K and their capacity is greater than incineration on a daily basis.  http://gold-mill.com/Products.html
 Kevin has proven that for circuit boards they will separate the metal fraction from the boards. That is a big plus. 

When I refined, the only reason I went through all of the effort to produce a sample-able powder and a sample-able copper base bullion was to be paid for what was there from the smelter / refiner. You give that up when you sell it upstream.


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## rickzeien

On a small scale I read about (but cannot find) a article/post for PCB pyrolysis using a Dutch kettle cast iron pot with a lid. 

A pipe was threaded into the bottom center of the pot. The pipe top was a few inches from the top to allow the gas to vent into the flame from a burner that the pot sat on. 

I wish I could find the link because I thought it was a genius way to simply process SMDs and PCB on a small scale. 

Sent from my LG-H872 using Tapatalk


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## rickzeien

With the "mill and separate" via shaker table model there is still a very large fraction of the material that is hazardous waste. What is the cost and logistics involved with proper disposal of this waste stream?

My research has not yielded any suitable "buyers" for this material. 

In the "burn" model the slag encapsulates the solid waste stream and is sold as aggregate.

Sent from my LG-H872 using Tapatalk


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## kjavanb123

rickzeien said:


> With the "mill and separate" via shaker table model there is still a very large fraction of the material that is hazardous waste. What is the cost and logistics involved with proper disposal of this waste stream?
> 
> My research has not yielded any suitable "buyers" for this material.
> 
> In the "burn" model the slag encapsulates the solid waste stream and is sold as aggregate.
> 
> Sent from my LG-H872 using Tapatalk



I remember seeing a link of company in China or in East EU where they processed failed circuit boards, collected copper and fabrics turned into a brick that was used in contruction, I think Patnor101 provided the link.


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## kjavanb123

rickzeien said:


> On a small scale I read about (but cannot find) a article/post for PCB pyrolysis using a Dutch kettle cast iron pot with a lid.
> 
> A pipe was threaded into the bottom center of the pot. The pipe top was a few inches from the top to allow the gas to vent into the flame from a burner that the pot sat on.
> 
> I wish I could find the link because I thought it was a genius way to simply process SMDs and PCB on a small scale.
> 
> Sent from my LG-H872 using Tapatalk



Deano had posted the paint design on what you are talking about, I built a system based on that which worked great for pyrolysis of components.

But it was not working for PCBs, so many toxic fumes. I have always try to find alternative to that.


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## kjavanb123

4metals said:


> When you compare the efficiency of the pyrometallurgy process, on a large scale, do you really think it's reasonable to try to shred/mill/concentrate the stuff?
> 
> 
> 
> 
> To even begin to start the pyrometallurgy process you need incinerate, crush and sift to get the material to melt. To use Kevin's method you would need to shred, and sift to get the material to melt.
> 
> Incineration is expensive between air permits and buying an incinerator. Entry level small incinerators go for $20K just for the unit, not talking stacks and permitting.
> 
> Chain mills (I have since looked them up after reading this thread) are available for $5K and their capacity is greater than incineration on a daily basis.  http://gold-mill.com/Products.html
> Kevin has proven that for circuit boards they will separate the metal fraction from the boards. That is a big plus.
> 
> When I refined, the only reason I went through all of the effort to produce a sample-able powder and a sample-able copper base bullion was to be paid for what was there from the smelter / refiner. You give that up when you sell it upstream.
Click to expand...


I will try to run a test with identical populated circuit boards.


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## rickzeien

kjavanb123 said:


> rickzeien said:
> 
> 
> 
> On a small scale I read about (but cannot find) a article/post for PCB pyrolysis using a Dutch kettle cast iron pot with a lid.
> 
> A pipe was threaded into the bottom center of the pot. The pipe top was a few inches from the top to allow the gas to vent into the flame from a burner that the pot sat on.
> 
> I wish I could find the link because I thought it was a genius way to simply process SMDs and PCB on a small scale.
> 
> Sent from my LG-H872 using Tapatalk
> 
> 
> 
> 
> Deano had posted the paint design on what you are talking about, I built a system based on that which worked great for pyrolysis of components.
> 
> But it was not working for PCBs, so many toxic fumes. I have always try to find alternative to that.
Click to expand...

Thanks for the info. I was going to try on PCB but will now keep looking also. 

Sent from my LG-H872 using Tapatalk


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## snoman701

4metals said:


> When you compare the efficiency of the pyrometallurgy process, on a large scale, do you really think it's reasonable to try to shred/mill/concentrate the stuff?
> 
> 
> 
> 
> To even begin to start the pyrometallurgy process you need incinerate, crush and sift to get the material to melt. To use Kevin's method you would need to shred, and sift to get the material to melt.
> 
> Incineration is expensive between air permits and buying an incinerator. Entry level small incinerators go for $20K just for the unit, not talking stacks and permitting.
> 
> Chain mills (I have since looked them up after reading this thread) are available for $5K and their capacity is greater than incineration on a daily basis.  http://gold-mill.com/Products.html
> Kevin has proven that for circuit boards they will separate the metal fraction from the boards. That is a big plus.
> 
> When I refined, the only reason I went through all of the effort to produce a sample-able powder and a sample-able copper base bullion was to be paid for what was there from the smelter / refiner. You give that up when you sell it upstream.
Click to expand...


I'm sorry...I meant processing boards on a large scale with mechanical depopulation/grinding vs just sending them off to one of the large refineries. 

You can get a chain mill much cheaper than 5k. I've used an RJ Rock Crusher and new cost is around 900.


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## IdahoMole

For myself it isn't necessarily about profitability or the most efficiency, it is about learning a process. Smelting anything and building a copper cell is largely new territory. I enjoy the challenge of learning new things. Eliminating the need to burn anything simplifies the process greatly. I can fund a hobby with my day job so the shiney metal at the end is just the reward for hard work.


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## kjavanb123

Hi everone,

A little update on this project. I cut 25 kg (~ 50 lbs) of depopulated circuit boards and I am guessing at least another 30 kg is left to cut manuallly.




I will time the mill to pulverize the entire cut boards so I can calculate the capacity and speed of mill.

After that there will be panning, smelting copper and sparging it to get pure copper.

Stay tuned.


Best regards
KJ


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## Smack

kjavanb123 said:


> Smack said:
> 
> 
> 
> I would say the chain/hammer mill is slightly louder. If I'm going to be in my shop when the ball mill is running, I will put a large cardboard box over it. The 5 layer gaylords really quiet it down.
> 
> 
> 
> 
> Thanks for the tip. I will try this out.
Click to expand...


Here is a company that makes enclosures and a link to an auction site that has a used enclosure.

http://tamerind.com

https://tinyurl.com/yc92mxrf


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## kjavanb123

Smack said:


> kjavanb123 said:
> 
> 
> 
> 
> 
> Smack said:
> 
> 
> 
> I would say the chain/hammer mill is slightly louder. If I'm going to be in my shop when the ball mill is running, I will put a large cardboard box over it. The 5 layer gaylords really quiet it down.
> 
> 
> 
> 
> Thanks for the tip. I will try this out.
> 
> Click to expand...
> 
> 
> Here is a company that makes enclosures and a link to an auction site that has a used enclosure.
> 
> http://tamerind.com
> 
> https://tinyurl.com/yc92mxrf
Click to expand...


Thanks Smack.


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## kjavanb123

Update,

I used stuff in hand to resolve the dust pollution from this mill.

First change, the output bucket increased from a 10 liter bucket to this 25 gallon bucket with cap on seal.

I also used spare tire, and cut it to seal off the door for the mill, output port the enters the 25 gallon bucket, also to seal off the output pipe that comes out of pucket and goes into another bucket filled with water and soap to collect the dust.




That design did not go well, as there was still dust. So I changed it in a way a vacuum is connected to bucket and is sealed off.

It seemed to work on initial test, will run fee lbs of boards to see if this design works.



I have been timing since the mill starts to the shut down, based on guesstimate this mill is capable of pulverizing about a kilogram of shredded blank boards per hour. 

A more accurate figure will be known once I finished running all boards in the mill.

Thanks 
Kj


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## kjavanb123

Update on dust control with vacuum, it works perfectly no dusts at all and no smell. This size vacuum is good for this size mill.


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## anachronism

kjavanb123 said:


> I have been timing since the mill starts to the shut down, based on guesstimate this mill is capable of pulverizing about a* kilogram of shredded blank boards per hour. *



So it's not viable financially. 24Kg per day with someone to man the process. An interesting diversion at best. Park it and move on Kevin.


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## IdahoMole

A kilogram an hour doesn't seem right to me. I have never used a piece of equipment like this but i would think it would chew up a kilogram of boards in a minute or two.


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## kjavanb123

Hi

This was copied and put together to see its performance for scrap boards, capacity was my second objective.

This design can go bigger on motor and number of chains which also means bigger chamber, that would make processing a kilogram of boards per few minutes viable.

Again this was just prototype, and its output got the 20% recovery rate that was aimed for.

Regards
KJ


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## IdahoMole

How are the chains holding up to the circuit boards?


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## kjavanb123

Hi

I haven't noticed any wear out on the chains yet. So far I processed 20 kg shredded blank board.


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## cuchugold

I'd love to see the shaker table design.


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## kjavanb123

Update,

As I process the blank board in chain mill I time myself, based on what I milled so far and time took, put the capacity of my mill to 3 kg per hour ( ~ 6 lbs / hr ).

Again, this was my first version, a bigger electro motor 8hp or bigger, and larger chamber with more chains would increase the throughput.

Shaker table will be after I completed the milling of shredded blank boards.

Best regards
Kj


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## IdahoMole

Kevin, if i remember correctly you started with 5mm discharge holes and then discussed making them much smaller. Did you make that change? If so how is it working? What particle size is the mill producing and are you happy with it?
Thanks, 
Jason


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## kjavanb123

Hi Jason,

I did not change the output size of 5mm, based on results I got from processing the fine boards and copper recovered seems like 5mm is the right size.

I will finish pulverizing boards and separate copper soon.

Best regards
KJ


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## kjavanb123

Update,

As I am separating copper from pulverized blank PCBs, noticed the greater volume of shredded boards I feed to mill the greater volume of output becomes fine.

Also as non-metalics grow, I came accross this article about using non metallics of PCBs into bricks.

https://ieeexplore.ieee.org/ielx5/5971803/6076205/06076214.pdf?tp=&arnumber=6076214&isnumber=6076205

Best regards
KJ


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## kjavanb123

Update,

I have promised and planned to test the efficecy of my chain mill to process boards using gravity separation.

Since there is no shredder in the lab as of yet, I manually sheered the board into smaller pieces to feed to chain mill,



It went pretty fast, here is the result.



I use two different sieves, one to separate the very fine powder, and other the coarse pieces, and the oversize part which was minimal.

Using my homemade blue bowl, I separated the non-metalics fine from the metalic fine powder,



Here is the clean up of fine powder, after ferrous pieces were manually removed,



Here is the ferrous fine powder which was removed,



More in next post


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## kjavanb123

The following is the "coarse" pieces cleaned up, and separated into ferrous and non-ferrous parts,

Non-ferrous



Ferrous



First I added dilute hydrochloric acid to dissolve any lead, tin, aluminum etc, as it can seen, reaction is taking place as is evident by the bubbles on surface.



In previous experiment which I depopulated and smelted components of identical circuit board, there was no gold recovered, but I recovered 2.9 grams of silver.

During cleaning up process of non-ferrous fine powders, I did not notice any gold bond wires, only grayish powder which seemed to be the heaviests.

I will update this as I try to recover silver from concentrates recovered from milling and gravity separation, to see how close it will be to silver recovered using lead smelting.


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## kjavanb123

Ok somewhat interesting result so far. I was able to hand pan the hcl solution which still reacting with non-ferrous fine, and see the lovely yellow band of heavies.

I let the fine powder to react with hcl till tommorow so I can neutralize solution then dissolve the remain in nitric acid.




Tommorow if time permit, I will recover silver and report my finding.

Although seeing gold in this process tells me that for whatever reason I could not cupel it right with my last identical sample.

Best
KJ


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## kjavanb123

Hi all,

I have another 20 lbs or so of cut bare boards to run in the chain mill.

So far recovery percents for minus 100 medh and plus mesh 100 to minus mesh 40 in two different batches were as following,

Batch 1:
Percent of pulverized boards that pass mesh 100 screen is 87.56%
Percent of pulverized boards that is bigger than mesl 100 but passes through mesh 40 screen is 12.43%

Batch 2:
Passing mesh 100 is 91.36%
Passing mesh 40 but stay on mesh 100 is 8.63%

I can only think of size of cut boards has to do with smaller output size. For this design mill with 5mm holes, the bigger chunk of boards the smaller the pulverized output size will be.

Also in local lab supply market I found a supplier who is paying $17 per kg of pulverized copper, which is really good.

More updates soon.

Best regards
KJ


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## kjavanb123

All,

Recovery and melting copper from my leftover bare boards partially completed. Here are 6 kg copper ingots. There is another 6 kg of copper which waiting to process boards.

Used salt and lemon to polish the surface.










So far recovery percentage has been 19% of weight of bare circuit boards.

Thanks and best regards
Kj


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