# Smelting



## 4metals

OK smelting it is.

First let me say that the majority of medium to the small side of large refiners today are running circuit boards today by smelting and refining the copper. The more time you can put into segregating and separating the material the better the payoff. That is why this is done in countries where labor is cheap. Having 15 or 20 sorters picking through the boards and cutting off components is effective at producing a feedstock which lends itself to electrolytic copper refining to concentrate the PM's in slimes. Poor sorting results in smelting lower grades of copper with metals like lead which are a nuisance metal in the copper refining process and they are a reason copper smelters will charge you extra when these metals are in the mix. 

So assuming we all have the sorting process down pat, we end up with boards and components which we need to burn. The ideal scenario is controlled pyrolysis, followed by incineration, and then either sifting or smelting. If we go the smelting route generally circuit boards need copper added to get up to about 15% metal weight for the best collection. 

When smelting the ideal system involves melting in a rotary kiln. These are pricey and not very versatile. 

So let's start out with me showing you a photo of a small tilting pour gas furnace, this is a center pivot furnace and this is about as small as they get.




The center pivot refers to the pivot points on the tripod stand which means the unit pivots from the center when pouring. These are the least expensive units to produce and they are challenging to pour bars with. As you tip the furnace more and more when pouring, the spout where the metal comes out moves closer to the furnace center line. At full tilt, you are under the furnace. So you have to move your mold to catch all of the pour. To define the challenge a little better, if you have a furnace 24" in diameter, the pour spout moves in an arc which will drop 12" down and 12" towards the centerline of the furnace. A hydraulic melt table will make this do-able but it has to be moved in and down as the pour proceeds. It's a skill you acquire with practice, or maybe spills and practice.

The alternative is a nose pour furnace which has the pivot point from the stand on the outside edge in a line tangent to the outside diameter of the furnace body. This results in less travel of the pour point when pouring bars. 

this is a catalog cut from a Baker gas nose tilt furnace.




So you might ask, why not a lift and pour crucible? My answer is capacity. I tend to work on bigger stuff so i think along those lines. Plus for a lot of members here on GRF who work alone, lifting and pouring a large crucible is a 2 man proposition. A tilting pour is a one man show. 

You could build a furnace into the ground. Just like the refiner in Thailand from this thread posted by Gaurav.http://goldrefiningforum.com/phpBB3/viewtopic.php?f=38&t=23609

To pour from this furnace they need to lift the crucible out and pour it. Generally a crucible is lifted with a pair of these tongs.



These can lift 2 ways, one by having one man on each end, and the other by using a hoist on the ring in the center, the hoist pulls up and the tongs cradle the crucible from the sides tapering to the bottom so it doesn't slip. Then to pour it has to be transferred to a pouring cradle. 

That is why I like a tilt pour setup. 

The unit I am working on for my client in Mexico is a hybrid of 3 different pieces of equipment. It has a nose tilt crucible furnace which is poured by tilting the furnace with a hoist pulling on a cable attached to the lower half of the furnace 180 degrees opposite the pour spout. Pretty basic. 

Then there are different lids. The regular melting furnace lid, the limit the oxygen and deflect the smoke into the afterburner lid, and the actual afterburner.

Now here is a catch. These lids are refractory and quite heavy so you will need an overhead lift. I prefer this type of crane but an overhead I beam would do as well. In a smelting shop an overhead hoist is a blessing. When you shot metal into water, you need a good quantity of water and you don't want to change it often. (climate change, drought, California is a desert, you know the drill) So the shot tank has a rigid metal liner on chains that fits the bottom of the tank and after you pour, you hoist out the liner and all of your nice shot comes with it.

This is the style of hoist crane I prefer;



I made this furnace representation in Paint on my laptop so some of this makes sense. The red is obviously the flame. The bottom flame heats the crucible and its contents. There is no crucible shown in the sketch. I prefer nose pour crucibles but it will also take a standard crucible and you can add a launder to direct the molten metal. The top section is an afterburner. When using the unit for pyrolysis, a lid is added over the charge so all of the smoke comes out the center. The afterburner section is just an extended burn chamber with its own flame which I like to run with excess air as the combustion smoke is air starved at this point. This is pretty effective at burning the smoke off from the pyrolysis providing the hole in the top between the top and bottom (also not shown) limits the smoke and uncombusted fume discharge rate.




The rings on top of the top unit have a chain which is picked up by a hoist to remove the afterburner. A gas quick disconnect is helpful here. 

So to operate the unit with a batch of unburnt circuitry first the crucible is filled. Then the air restricting lid is placed on top with the hoist, then the afterburner is put in place. The afterburner fires first and when it is hot (glowing is nice) the lower unit is lit. For pyrolysis this is a low heat not full blast but warm enough to get the pyrolysis going. I toyed with the idea of putting a bottom on the afterburner unit to eliminate the need for the lid to control the smoke entering the afterburner. The bottom would obviously have a small hole to emit the smoke. I chose to not do that because I may need the afterburner for mild smoke conditions at some point and no lid would be needed, so for versatility I chose to keep it separate. 

When the pyrolysis is done, a # 150 crucible should take about 1 hour, the burners are shut off and the afterburner is removed, the inner lid is removed, and the furnace (bottom) is re-lit. Then the carbon is burned off to complete the pyrolysis/incineration process. I would be putting the afterburner back on for this process until you learn how long to burn to complete pyrolysis, but that's me, I've inhaled enough crap in my life already. 

The furnace can now be either emptied out to sift and flux the powders or flux can be added to the charge in place. A second lid for melting is placed on top of the furnace, it too is placed with the hoist. I added a pin at the rear opposite the pour spout so the lid doesn't slip off while pouring. The pin slides into an oversized sleeve on the furnace so it is easy to place the lid on. For the smelting part of the cycle, copper is added to get the metallic fraction over 15% and I like to rock the furnace. Remember it pivots, so getting the molten pool swirling by slow rocking using the tilt hoist will aid in collection. The molten charge is periodically slagged off by pouring into a slag mold. Large slag molds are sold by Legend and they attach to a buggy so you can roll them around.




After the furnace has melted all of the flux/sweeps charge, the majority of the slag is poured off until the metal starts to flow into a sample ladle then the charge is shot into water to make grain. 

The copper based grain is cast into anodes. The furnace is too large to make the high surface area thin anodes needed for the copper cells so that is why grain is cast. It is easily weighed out and cast into individual anodes. 

So that is smelting, we do need to cover fluxes and a few details but this is the hardware, the rest is chemistry. 

The actual furnace I just described is currently being cast, the 1/4 scale model worked very well, It takes a # 40 crucible. They plan on using the little guy as well as the one being built. The first unit was built by the maintenance crew at the shop from some rather crude drawings I had made, they completely understood the concept (not from my Spanish, from the boss's translation!) and went with it. The bigger unit is more of the same. So for a moderately handy person, this is definitely within reach.


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## 4metals

This is the bottom section pivoting to pour




Please excuse my sorry representation of the flame path!


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## alexxx

One can smelt many types of material. 
As I understand it, the success and profitability of the smelting depends a lot on material preparation.

Is this aspect of material preparation will be covered depending on the feedstock ? 

A few examples of various types of scrap one can get : 

-Circuit boards
-Sulfide ores 
-low grade PGM bearing material (car spark plugs mentioned earlier)


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## UncleBenBen

I know I've seen lead mentioned several times as a problem metal for the copper refinery, and spoke of again here by 4metals. What are the other problem metals?

That might help me wrap my head around a little thought bubble that's trying to percolate, but right now my lips keep covering my eye teeth and i can't quite see what I'm trying to say.


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## kurtak

FrugalRefiner said:


> Splitting the thread is not a problem. I've already PMd 4metals about it and I'll split the smelting portion off after I get his response.
> 
> Dave



Thanks Dave --- I will be adding to the smelting thread after you have split it off to its own discussion so as not to clutter this thread 

Kurt


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## 4metals

I always prefer to remove the incinerated material from the furnace to crush and screen it before fluxing and smelting. This is for a number of reasons, first, there is a fraction that is metallic and if it can be separated by crushing and sifting, it can be melted with copper directly to make anodes. Often the highest percentage of values is in this "metallic" fraction. For years I used to incinerate boards and crush and sift them to make copper based bullion (which I assayed and shipped to a copper refinery) and shipped the powder to low grade refiners as sweeps. For the purpose of this thread, we are going to use the approach that we will process this material through the copper electrolytic process to concentrate and recover all of the values and pure electrolytically refined copper.

Some guys just flux the load in place and melt. I do not like to do this because for one, we do not know an after burn weight so we do not know how much flux to add. Second, without mixing the flux and ash well, a good amount of the benefit of fluxing is never realized. I have seen refiners pour melted sweeps only to see a nice smooth flux pour off first followed by a lump that never melted because it wasn't fluxed properly. 

Another benefit of crushing the lot is you can do test fusions in an assay crucible in a kiln to determine the best flux mixture. Then you can flux the entire lot and smelt it. 

In the prototype furnace I described earlier it was easy to onload a lot after incineration by lifting off the lid and tilting the furnace 90 degrees and raking the ash into a tray positioned in front of and below the crucible. A hoe fashioned out of steel and having a radius to match the crucible does a nice job. The larger furnace won't be as easy to lift off the lid for additions and emptying because it is much heavier and larger so a stand is being fashioned to allow the lid to swing open and rest on while charging the furnace while it is hot. This top down view drawing made in Paint may make this easier to understand. A removable steel rod will slide into a sleeve on the lid to make a handle to lift and swing the furnace open. The green circle represents the cover opening allowing material to be fed into the furnace.




Originally I was planning on making a lift mechanism similar to what Mifco uses but considering this lid needs to come off entirely when using the afterburner, I opted for simple. Remember heavily used equipment in refineries break, simple is better. The mechanism for a Mifco lifting lid can be seen in this drawing;




Once you have your ash out of the furnace it is a good idea to do a magnetic separation, a hand magnet like this can de-mag a lot of ash quickly and drop it into your magnetics pile. This is a nice hand magnet in action;




Now you can ball mill the ash without any magnetics in it, this is the best option but most small refiners do not have a ball mill. Some use cement mixers with a few balls to break up the ash. It works, kind of, remember it isn't really a ball mill.

Another option for nice crumbly ash is to sift it on a mechanical sifter and a hand full of 1" steel balls to crush and help the material go through the screen. A -20 mesh screen would be the largest I would use, a -40 mesh is better. A nice sifter for a small refiner is a drum top sifter. This little beauty sits on a 30 gallon drum and sifts right into the drum.




Another sifter for a small operation is a Ro Tap sieve shaker. These come in a size to shake 8" screens or 12" screens. This actually does not need balls as the Tap portion of the name implies, there is a weighted arm that pounds on the top of the sieve frame every few seconds to help break things up. 




It is always a good idea to keep an eye out for these at auctions, there are lots of industries that use them and you never know when the people bidding have no idea what it is used for.

This pretty much describes what you will need to smelt. Next we should discuss fluxes. The right flux will make the melt more fluid and allow the metallic fraction to collect in a pool of molten metal.


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## alexxx

What would be the targeted temperature for pyrolysis ? If the charge is heated too high, some metals are going to melt obviously.
Aluminum, Tin, Lead... Any problems resulting from melting these metals in the pyrolysis stage or does the right fluxing will get rid of them ?


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## kurtak

alexxx said:


> What would be the targeted temperature for pyrolysis ?



between 600 & 750 F



> If the charge is heated too high, some metals are going to melt obviously.
> Aluminum, Tin, Lead... Any problems resulting from melting these metals in the pyrolysis stage or does the right fluxing will get rid of them



Per the under lined above - the answer is both yes & no --- in order to have metals go off in the slag (flux) they need to be in an oxidized state --- this can be "somewhat" effected/influenced with fluxing - furnace flame environment also plays "somewhat" of a factor here (whether the flame is an oxidizing flame or reducing flame)

in other words though some metal may be oxidized & carried off in the slag it wont be complete 

Kurt


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## Irons

Great thread 4Metals, thanks.


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## Shark

I am understanding the furnace design correct in that is acts as both the furnace and crucible? And the pour is directly from the furnace as a crucible?


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## 4metals

This particular furnace is a crucible furnace. The flame enters the bottom and heats the crucible holding the charge.


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## Shark

That makes more sense, and now that you explain it, I can see it in the Mifco design. This is looking to be a great post, Thanks for all the input.


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## 4metals

If I remember correctly Harold made a furnace that was a direct melt furnace. I seem to remember him posting pictures of it on the forum. He is quite the craftsman!

Maybe he will chime in here with some pictures and his experiences with his furnace.


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## FrugalRefiner

As Alexx mentioned, there are many materials where smelting might be the best process. I'll add to his list by suggesting posts on MLCCs and ICs. 

I don't deal with the quantities of e-waste that many of you do, but I do accumulate a bit of it. I'd be interested to know what those with experience would consider minimum batch sizes. Everyone collects MLCCs, and as I understand it, smelting is the best way to process them. If someone has an appropriate sized furnace and crucible, could they smelt a few ounces, a pound, a few pounds?

I'm sure some of our prospectors will be looking forward to coverage of ores. Keep it coming guys. I see a great Library thread in the making here. 

Dave


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## 4metals

I posted this exact post on a thread about melting gold but I also realize it is pertinent here as well, so at the risk of being banned for double posting I have copied it here as well. 

*Types of flames for melting*

When melting the 2 fuel sources mix together to form a specific type of flame depending on their ratio. Those 3 types are the Oxidizing flame, the Neutral flame, and the Reducing flame (also called the carburizing flame)





So by controlling the airflow to the fuel and the quantity of fuel you control the flame. Some torches burn oxygen and a pressurized gas but blower type furnaces use air but the thing in the air that is doing the work is the oxygen.

A reducing flame is a flame that is starved of oxygen, when a flame is starved of oxygen it tries to make it up wherever it can. A potential source is metals that are oxidized in the melt. The flame wants that oxygen bad and it grabs it from the oxidized metals in the melt and in the process reduces those metals. A reducing flame is made by cutting back the oxygen supply by throttling down the air supply. This makes the flame start to roar. A reducing flame is the loudest flame in a melt furnace. 

A neutral flame is a flame burning with a balanced quantity of oxygen and fuel. For metals melting it will get your charge hot enough to melt but will neither oxidize or reduce any of the charge.

An oxidizing flame is one that has an excess of oxygen and it gives up oxygen to any metals in the melt that can be oxidized. Fortunately for precious metal refiners the Noble Metals are noble because they resist corrosion and oxidation so they will not come out of the charge as an oxide. 

In practice you never have the gas or the air wide open, usually you set both to light the furnace and get it pre heated and then start lowering each independently a little at a time to get the flame you desire. 

The catch in all of this is that in a crucible melt, it really has little effect because the flame does not contact the charge other than passing over the surface of the melt which usually has some sort of flux covering it. 

When incinerating and having an open flame on the charge it does make a difference as the flame (and the excess or lack of oxygen) reacts directly with the charge. I have also done quite a bit of sweeps melting using a rotary kiln which actually uses the kiln as the crucible and the flame heats the charge directly. For this type of melting the ability to control the reducing power or oxidizing power of the flame matters. 

For crucible melting if you desire to remove metals from a melt and encourage them to collect in the flux, an oxygen wand immersed in the molten pool with a slow steady flow of oxygen rising through the melt is very effective at removing a lot of metals. The exception being obviously the noble metals and copper. Copper doesn't like to gas off into the flux with oxygen. While in theory it should, in practice it just doesn't. The trick here is to have an open center of molten metal in the crucible and a donut shaped pool of flux to collect the oxides when gassing oxygen with a wand.

I have found most melt and incineration setups lack the sophisticated gauges and valves to precisely control either the gas or the oxidized. So you learn to work the valves and listen to the sound of the burner. Remember, louder is reducing, a more quiet roar is oxidizing. You can also judge from the flame color coming out of the top of the furnace when it is running. 

This furnace is running an oxidizing flame




And this furnace is running a lean or a reducing flame, and quite likely more noisy than the previous furnace.





I have seen large gas melt furnaces that have the mass to absorb the sound (my guess) combined with a large top hole that only produce a gentle roar regardless of the type of flame. But the flame color coming out the top is still an indication.


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## alexxx

Great post again, wow, I love smelting already.

I can see the uses around an oxidizing flame.
Again, with a prepared feed stock of boards like you mentioned earlier, if you want to remove as much base metals as possible from the charge, injecting oxygen into the melt and with the right flux recipe, one could achieve a good copper anode quality ? For that specific scenario, it's a great thing that copper doesn't react like the other base metals.

Do you have examples of when a neutral or reducing flame would be used when dealing with precious metals bearing materials ?


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## 4metals

Choosing a reducing or oxidizing preference is almost like asking a kid if he wants vanilla or chocolate today. It all depends.

I believe in the initial separation of the values and metals from the ash in circuit boards you want to assure you don't lose any metals to volitalization, you want to catch them all in the metal pool so you don't lose any values. I do this using a reducing flame and a reducing flux mixture. Notice I said I believe, I am sure there are other opinions and good discussion is healthy!

In all of this type of material I have processed in my day, the metals I've had to contend with are;

Zinc
Lead
Iron
Tin
Antimony
Nickel
Aluminum
Copper

And of course silver, gold, and the PGM's but they stay with the copper. 

I went back to the data I personally collected from 3 setups I have done for this and came up with a range of each of the above metals. Since this is scrap after all, we can never control the source and the manufacturer or the age of the circuitry so these numbers vary but in the analyses I've done on the collected metals after smelt these are the percentages determined by atomic absorption on the metal poured out and sampled. I've tabulated this on Excel so it is quasi understandable. They all represent a % of the base metals in the final pour less the weight of copper added and, of course based on the pre burn weights.




So from my experience the metals I want to collect in the metal pool are listed above. Less the precious stuff obviously. 

So my flux needs to have the power to reduce the metals. Now most metals that are metallic to start only need to be melted but often from things like resins that have been roasted you want to reduce the metal which may have been captivated as a salt. One example of this are refining residues with chlorides or burnt cloths from spill clean ups of aqua regia or test papers. By melting them in a reducing environment you are assured better collection. 

I also tabulated some information about different fluxes for our discussion.




What this all tells us is how different ingredients in our basic flux will react to our charge. It has been my experience that PCB ash is pretty much a pH neutral charge and its components are really pretty easily reduced into the pool. For some ores and different materials some of the reducing agents will need to be added or possibly some desulfurization aids. But for PCB's I always just used a flux made up of Borax glass, Soda ash, and Silica. Together they will give you a fluid melt. To start off I would add a mixture with 10 pounds of Soda Ash, 5 pounds of Borax and 2 pounds of silica. Mix that up well and add it to the ash in the ratio of 1 pound mixed flux to 1 pound ash. Experience will teach you to tweak the formulations or you can simply add a half pound of flux and a half pound of ash to a melt crucible and fuse it in a gas melter to assure you get the fluidity in the melt and that everything is fluid so it stirs easily and pours smooth. If it is lumpy that says more flux to ash in the mix. This flux will be effective at collecting all of the metals in the molten pool. Generally printed circuit boards have enough metal in the overall percentage that they do not need additional copper. 

Once molten, the melt is allowed to rest at full heat so the metal in the pool collects in the bottom of the crucible. The slag is poured off and when you get down to the metal pool it is either cast into bars or shot. This metal has mostly copper, all of the PM's and the other metals listed above if they are there. Remember, the better you clean up your boards before smelting, the less you have to deal with in the alloy you just poured. It's just like a computer, garbage in garbage out.


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## 4metals

Before we can recover our precious metals from the slimes in the anode bags of our copper cells, we need to make sure we can get the feed copper to be as pure as we can up front. If you did your work up front and removed a lot of the iron and aluminum this part is easier. 

I have cleaned my copper up while it is molten in a crucible by slowly bubbling oxygen into the melt to form oxides of the metals we are looking to remove. I have tabulated the metals we are looking to remove in this table. Copper is on the list but it comes off last so all of the other contaminants will react first. This is also done with compressed air as the source of oxygen. When refining copper electrolytically, Tin, Bismuth, Antimony and Lead all dissolve and end up in the slimes. Keeping this in mind it may be more desirable to skip the oxygen sparging (which is an extreme step) and allow the undesirable metals either end up in the slimes or dilute them with clean copper so you can go directly to the anode phase here. 




This shows us that the metals will form oxides which we can collect in a flux ring which forms when there is not enough flux to cover the entire melt surface. This thin donut of flux is made up of borax, silica, and soda ash 1:1:1 to gather any oxides that form and capture them in the flux. Sometimes the flux gets so thick with the metals you need to skim it off and add new. This process is not fast and usually it goes 6 to 8 hours to make the copper 99% copper. (actually 99% copper plus precious metals content)

So this is the point where all of the others who have done this can comment and make this more interesting. For now we should limit the discussion to printed circuit scrap, maybe we can get to ore concentrates later if Deano gives his opinions. 

Have a Happy Easter!


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## Smack

Thanks for the Easter present 4metals. Gonna have to read that a few times.


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## alexxx

A few questions regarding the table that was posted;

- The last 2 columns "oxide melting points in C / F"
Are those temperatures the temperatures needed to form an oxide or the temperature needed to melt the oxided elements in order for them to report into the slag? In other words, do you need to reach the oxide melting point in order to drive the oxide into the slag?

- since fluxes are also playing an important role in lowering the melting points of various elements, are they also lowering the melting points of their respective oxides?


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## kurtak

First I want to say I am sorry for my delay in responding to this thread but yesterday I had to filter/wash & dry about 2 lbs of silver (with PGMs in it) & drop, wash & dry about a 1/2 ozt gold - all of which came from some "waste" that was given to me from another local guy that was trying to get into PM refining - I was "trying" to coach him but he wasn't a very good listener - he made a lot of messes with value lost into his waste which I now have & I expect I will recover several thousand dollars in value from what he gave me - the above recovery was just the "start" of what he gave me --- anyway ---------

4metals --- I love your combo furnace/incinerator design & have actually been thinking down those same lines of thought as an improvement/up grade to my bigger furnace 8) --- thanks - you just made the brain work a lot easier :mrgreen: --- now I just have to find the time to make the build - that may be awhile with everything else I have on my plate  

Now to back up a bit & comment on some of what you have already posted



> The more time you can put into segregating and separating the material the better the payoff.



Absolutely - as the saying goes --- garbage in - garbage out --- garbage on the out put end can prove to be problematic on the final processing end of things (all of which can be dealt with - but) the larger you go in material to be processed the harder it is to control

Examples; - on a smaller scale - say you are handling between 1,000 to 4,000 or 5,000 lbs of CBs a year you can likely take the time to depopulate the boards for there higher yield components (like ICs & pins) & thereby "significantly" reduce the "garbage in" problem (& then sell the depopulated boards out right as low grade copper recovery) --- start working with more then a couple tons of boards a year & you have to go to complete board processing (or scrape "everything" off the board) in which case at best you can "maybe" take the time to pull larger pieces of iron, aluminum & plastic (or sort them out) so your garbage in ratio goes up significantly (tin & aluminum in particular - iron can always be magnetically separated)

One point I see you did not make mention of (when dealing with whole CBs) is that they need to be shredded "before" going to pyrolysis/incineration --- if you don't shred them you will encounter problems at both the ball milling & sifting stages due to over size - the ball mill in the first place simply will not handle (effectively) the larger size of a pyrolized "whole" CB - you would have to load the mill with less material AND run the mill for a longer time to get it to break the boards down AND the sheets of copper layered in the CBs will ball up trapping everything from iron (making magnetic separation less effective) to carbon/ash (that then does not fully mill down) to values that then end up in your over size fraction during sifting

So you need to first shed the boards by running them through a knife mill or hammer mill first to reduce them to shredded material around 1 inch or 3/4 inch material going into the pyrolysis/incineration 



> Once you have your ash out of the furnace it is a good idea to do a magnetic separation



This should actually be done after both milling & sifting other wise you will pull large piece's of pryrolized material out that are holding values (IC chip in particular) which you will then have to mill, sift & then re-do a magnetic separation on anyway

So you really want to mill first (after pyrolysis/incineration) then sift (to remove the over size) which may or may not need re-milling depending on how well it milled the first time --- as long as the over size was well milled (meaning it is for the most part made up of only metal) you then want to do your magnetic separation on both the over size & the ash that went through the sifter (the over size to remove the iron fraction from the copper fraction so the copper can be used as your collector metal in the smelting)

concerning the over size fraction from the sifting process - there should be "little" or "no" values tied up in the iron that you removed with the magnet (provided you spread it thin enough that it doesn't drag some of the copper fraction with it) the copper fraction will carry some (small) value with it due to copper sheet (layered in the CBs) balling up in the mill thereby collecting bond wires &/or pins &/or the fact that some CBs have gold plating on the top layer of copper under the solder mask - but that ok because the copper fraction is going back into your smelt as the collector anyway

Concerning the sifted fraction - when you do the magnetic separation here you are going to drag values out of the ash - this can not be helped - even if you spread the ash "very" thin - what happens is that the magnet does not just lift the magnetics straight up out of the ash - but rather it pulls the magnetics together "through" the ash & in the process of coming together it will grasp ahold of values & drag them out --- you can get "some" of it to fall back out by shaking &/or tapping the magnet --- then thinner you spread the ash the better you will minimize the value drag out 

So - one way or another you have to deal with this magnetic fraction to recover the values that were dragged out with it - you can dissolve the magnets away with acid - or - you can re-run it as another magnetic separation - but there is a trick to the magnetic re-run

You want to first spread the magnetic fraction very, VERY thin - then when you run the magnet over it you want to hold the magnet further away "to start with" when running it over the material - far enough away that it is just barely picking up the magnetics (picking up some but not all) in other words you want the magnet to "pick" iron up - not drag it up --- you want to then keep making passes over it - each time running the magnet closer to the material then the time before --- in other words you want to slowly "pick" the iron away from the non-magnetic fraction rather then trying to drag it away --- done right you can remove the magnetic from the none magnetic with little or no value lost to the magnetic fraction

Kurt


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## kurtak

4metals said:


> This shows us that the metals will form oxides which we can collect in a flux ring which forms when there is not enough flux to cover the entire melt surface. This thin donut of flux is made up of borax, silica, and soda ash 1:1:1 to gather any oxides that form and capture them in the flux. Sometimes the flux gets so thick with the metals you need to skim it off and add new. This process is not fast and usually it goes 6 to 8 hours to make the copper 99% copper. (actually 99% copper plus precious metals content)



One thing I would like to add here (per the underlined above) is that due to the silicon dies in the IC chips you don't need to add silica to your borax/soda ash flux - especially if you are processing IC chips only that you have depopulated from the boards --- if you are doing whole boards you may need to add "some" additional silica

when you (ball) mill the incinerated boards/chips the silica from the silicon dies will mill down to a fine pulverized powder

Edit to correct my above statement; - Actually in rethinking you should not need to add any silica to a whole CB smelt ether as there will be silica provided by the fiberglass used to make up the layers of the CB its self 

Kurt


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## kurtak

Ok - I just talked to Ken who is the owner of the RPM web site (Refinement of Precious Metals) a while back we had a discussion there about smelting in which I posted some extensive info about smelting - I asked if it was Ok for me to copy & paste what I posted on his site over to here & he said no problem --- This will help me time wise in that I wont have to re-type things I have already typed & posted elsewhere

The discussion on RPM started with someone asking if he could smelt boards by simply putting them in the crucible, then in the furnace & heating it up to a melt temp 

So as not to over whelm this discussion I will limit what I copy from RPM to here to only one or two post a day - My next post will be the first copy from RPM (which was my first reply to the above question)

Kurt


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## 4metals

Alexx,

No you do not have to reach the oxide melting temperatures for them to form. It is posted to show they will exist in the oxide form and not decompose or volatilize until you exceed those temperatures. Most are quite high and not attainable in a gas furnace. 

In cases where you will exceed the oxide melt temperatures, like lead, checking the boiling point for that oxide shows a temperature not likely to be seen (2961F) so it will remain fluid and not gas off significantly until it is caught up in a slag. Antimony oxide also melts at a low temperature but doesn't boil until it gets to 2597F.


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## 4metals

Kurt,

The circuit board refining processing I set up were all out of the US where labor is cheap so boards are depopulated by many hands. Without ever realizing its necessity (which you have pointed out) the stripped boards were always sheared to thin strips either manually or by a machine. So all I ever saw was a rather well burnt ash. The fact that the smaller pieces aided this makes perfect sense. 

And I welcome your posts from the Refinement of Precious Metals forum.


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## 4metals

I have always believed that a successful refinery has good strong analytical support. To that end, all of the materials I collected as shot from the molten pool discussed above were analysed for metals other than copper. 

Please note that the process of oxygen or air sparging will cause the less noble metals to oxidize first and when the base metals are mostly gone and a majority copper remains, some copper will begin to oxidize as well. For this reason, good analytics and experience with gassing time and gas flow vs. the relative starting concentrations of less noble metals than copper allowed us to learn to control the gassing without too much copper oxidation. I do have concerns with this process (O2 sparging) being used without a proper lab to support it. 

I would like to see this thread evolve to the more realistic approach as the analytics will not exist for smaller producers. The more realistic approach involves obviously better pre treating by removing components and dealing with the accumulation in the slimes of some of the undesirable metals. Some metals will go into the electrolyte and cause issues with copper purity necessitating electrolyte change but I think that will be easier to deal with for a medium sized producer without a decent analytical lab.


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## kurtak

Here is are a couple pics of a hammer mill I picked up last year (just before the snow started to fly here) that I hope to incorporate into my processing - now I have to find a motor to run it - it going to have to be a gas motor as its going to take "at least" 20 horse power & when you go over 10 horse (electric) you need three phase which I don't have --- paid $350 for the hammer mill

Also a pic of a roller mill I picked as free scrap - not sure if,how or where I will incorporate it - but its not going to the scrap yard any time soon

I am using a cement mixer for my ball mill - it works "very well" but it is a small one & may have to up grade to a bigger one 

Kurt

Edit; - opps - forgot to add the pics


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## kurtak

Something that is important to understand about smelting (which 4metals has sort of pointed to but not really explained) is that when smelting you are actually preforming chemistry - in other words there are actually chemical reactions taking place in the crucible - things are not just melting - but rather when things reach certain temps - reactions start to take place - some reactions start to take place even before things start to become molten while other reactions take place once things become molten

Here is another post I made on RPM that "in part" explains this - it was in response to a question asking if baking soda could be used as a flux & also if glass (silica) could be used as a thinning agent instead of fluorspar --------

There needs to be a few corrections to the above (question asked on RPM) - first baking soda is sodium Bi - carbonate not sodium carbonate --- soda ash (or washing soda) is sodium carbonate

baking soda produces most of the same results as soda ash - however it (baking soda) liberates a lot of carbon dioxide at molten temps which has some "reducing" effects in the smelt (part of the chemistry) BUT - the escaping gases also tend to carry off precious metals as a mechanical loss & therefore is NOT recommended for use in smelting flux --- it is "sometimes" used in assay flux of "lead assays" to help reduce lead complexes to lead

Glass (silica) is not a thinning agent - at least not to any degree to make your flux fluid enough to achieve the good circulation you are looking for

soda ash (sodium carbonate) will help make the flux run "a bit" thinner - but likely not thin enough --- which is why I said earlier that if your initial flux/material load is not running fluid enough when it all gets molten you may need to add some fluorspar along with some soda ash - the fluorspar is doing the real thinning & the soda ash is bringing the melt temp down on the fluorspar so it can do its job of thinning

Fluorspar - like silica has a "high" melt point & like silica needs the other flux components to liquefy it (the chemistry again) --- also it is not the fluorspar in & of its self that is hard on the crucibles

Flux chemistry ---- Fluorspar as a flux by its self is a "neutral" agent - being neutral it has no "corrosive" properties in & of its self

On the other hand - other flux components have ether acidic or basic properties - both of which are corrosive - though bases & acids work to cancel each other out (make neutral) you are not going to get a neutral flux nor do you want one - you need chemistry to happen --- so you are going to have the corrosive effects caused by ether basic or acidic flux --- what happens is that when you add the fluorspar - due to the thinning - the effect of ether the base or the acid corrosion becomes more effective ------ handling the slag (after it cools of course) will cause chemical burns just like getting acid or sodium hydroxide on your hands - wear gloves

Because of the acid or base properties of different flux components you get the chemistry happening that then preforms tasks in the smelt - those tasks are oxidation &/or reduction &/or complexing (complexing being both oxidation & reduction at the same time by the same flux component)

Some flux components (in fact most) are complexing fluxes whether they be acidic, basic --- what that means is they do both oxidation & reduction in the smelt - dependent on what they are reacting with in the material being smelted

Soda ash is a "basic" (chemically speaking) flux - but also a complexing flux

Borax & silica are both acidic fluxes (in fact silica is a "powerful" acid flux) - they are both also complexing fluxes 

There are other components that can be added as well - all dependent on the material being smelted & the tasks you need preformed in the smelt 

I will make a more complete list along with there tasks later

Kurt


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## 4metals

Nice hammer mill Kurt. If the bearings are still good in those old things you can't kill them. You mentioned using a gasoline motor for the mill. That will likely be the most cost effective option but you then have to move outdoors to use it. Kind of like fair weather milling. 

Then I was thinking about what a local friend of mine did. He is a wood turner not a refiner but he had multiple big belt driven machines to power. He ran a long axle inside his shop with a big old bearing on each end to turn multiple pulleys located along the axle behind each machine. The pulleys on the axle have a clutch to engage or disengage when he needs the machine in front of a particular pulley. (He has to shut the engine and wait for the axle to stop spinning before he engages or disengages any machine on the system, but that is really not all that long of a wait.) His gas engine is mounted outdoors in a little wooden shed where you barely hear it and it turns the axle so he can use any machine along the line as needed. Last summer he added a homemade version of a car starting remote so he can power the gas engine from the warmth of his shop. So his machines stay inside, dry and out of the elements, (and rust) while he stays dry and warm inside using them all year regardless of the weather. 

If you could come up with a pulley driven ball mill you could use a gas engine for multiple machines as well. That will help offset the motor cost. I am sure there are other machines useful for refineries that run off a drive train but at the moment I am drawing a blank at naming them.


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## kurtak

Opps - I thought I had posted this "before" my last post (which was copied from RPM) but see now that I didn't


The discussion on RPM started with someone asking if he could smelt boards by simply putting them in the crucible, then in the furnace & heating it up to a melt temp --- the following was my reply to that question (& should have been posted before my last post) ------------

You "first" need to incinerate your material - you then need to mill it - then you need to make up a flux of 50 % borax & 50% soda ash - this is the basic "starting" make up for your flux which you may want to alter a bit one way or another depending on your material composition

You will "most likely" want to add some fluorspar to that borax/soda ash mix - the fluorspar is a thinning agent that helps your slag (flux after it becomes molten) run more fluid thereby providing better circulation in the crucible which in turn improves "metal collecting" during the smelt as well as allowing the metals to settle to the bottom of your cone mold when you make the pour (it doesn't take a lot)

Also - if ceramics are involved (like ceramic capacitors) you will need to ad some cryolite to the flux

It is best if you get anhydrous borax to make your flux rather then using regular borax (like 20 mule team) in order to reduce the problem of excessive foaming up

Once your starting material has been incinerated & milled you then want to mix your flux in with it using 2 - 3 time flux to the material to be smelted - just how much flux to material depends on the material - that depends on how much & what you are trying to "slag off" in order to collect your metals

In other words how much ash, glass (from fiberglass) silicon (from chips) metals oxides, ceramics, etc. needs to be slagged off from the metals - so its a question of organics/nonmetals to metals content question

Your metal content also needs to be high enough so that you get "good" collection of the metal other wise you will have a problem with "small" balls/beads of metal hanging up in the slag - that means you "may" have to add more copper if the copper content is not high enough in your starting material

Smelting copper requires both a relatively high metal (copper) content & a very "fluid" molten flux/slag (which is why I say you will most likely need fluorspar in you flux) to get good collection of the metal

Your flux needs to be "well mixed" with your material - I mix mine by running it back though my ball mill before going to smelt

Some things you need to know

1) When smelting you are not just melting things by bringing them to a high enough temp to get everything molten - chemistry is also happening meaning chemical reactions of oxidation &/or reduction are also taking place - that means "fumes" (not smoke) are being produced so fume control needs to be considered

2) "Some" fumes (not all but some) that are of concern are beryllium, cadmium, & lead if those metals are present - these metal vaporize at the high smelting temps

3) The flux is hard (very hard) on crucibles - so you want "good quality" crucibles like these - http://www.morganmms.com/produtos/cadinhos/salamander-super or these http://www.morganmms.com/products/crucibles/ultramelt 

4) You will have an initial foaming up as things get molten & reactions start to happen so you want to start with your crucible only about 1/3 full & no more then 1/2 full - the foaming will eventually go down & you can then make small additions of more flux/material watching the foam up so they don't over flow the crucible

5) you will have a greater problem with foaming if you use regular borax instead of anhydrous borax

6) after the foaming settles down & everything is molten you want to see the flux/slag rolling & fluid - not sputtering - this indicates you have good circulation & therefore good collecting (of the metal) going on - if you are not getting good circulation add some more fluorspar (it doesn't take much) & some more soda ash

7) be sure your mold is HOT when you pour to it or you may have an explosion 

(8) your mold needs to have a layer of carbon lining it or your pour won't release from the mold - I do this by putting a little cooking oil in the bottom of the mold & brushing it up on the sides & let it get "smoking" hot --- the excess oil will flame up when making the pour so watch out for that

Kurt


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## kurtak

4metals has already posted a list of flux ingredients - here is another one - it has a few ingredients that where not in 4metals list 

Flux used in smelting &/or fire assay along with there chemical properties & the tasks they preform

1) Lead Oxide (Litharge) chemical = basic - task = complexing

2) Sodium Carbonate (Soda Ash) chem = basic - task = complexing

3) Sodium Bicarbonate (Baking Soda) chem = basic - task = complexing

4) Potasium Carbonate (Pot Ash) chem = basic - task = complexing

5) Silica (Quartz, Sand, Glass) chem = acidic - task = complexing

6) Borax (decahydrate - like 20 mule team) chem = acidic - task complexing

7) borax (Anhydrous = no H2O = glass) chem = acidic - task = complexing

(8) Calcium Fluoride (Fluorspar) chem = neutral - task = thinning agent

9) Calcium Oxide (Lime) chem = basic - task = complexing

10) Ferric Oxide (Hematite) chem = basic - task = oxidizing

11) Potassium Bitartrate (Tartar) chem = basic - task = reducing

12) Charcoal (Carbon) chem = neutral - task = reducing

13) Flour or Sugar (Carbon) chem = neutral - task = reducing

14)Potassium Cyanide (Cyanide) chem = neutral - task = reducing

15) Potassium Nitrate (Saltpeter) chem = basic - task oxidizing

16) Iron (Iron) Chem = basic - task = reducing

17) Sodium Chloride (salt) chem = neutral - task = used as an assay cover

Edit to add; - (18) Cryolite --- used to dissolve ceramic (alumina/aluminum oxide) in smelting & I am not sure of the chem properties & or the actual task but assume it is a base due to being a sodium complex (Na3AIF6) & believe it would be considered a complexing task as it works by breaking the oxygen bond in the alumina (reduction) but does not completely reduce the alumina to aluminum thereby allowing the remaining (now dissolved) aluminum complex to be carried of in the slag 

Kurt


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## kurtak

Collector metal in smelting

The discussion about collector metal so far has been focused on copper & copper is a good collector especially if your starting material is already high in copper content such as the case with smelting whole circuit boards - silver is another option as a collector & in my opinion a better choice *IF* the material being smelted has "little or no" copper to start with --- also - lead can be used as your collector (which kjavanb123 has posted a fair amount about in some of his threads)

Here is a bit about copper vs. silver as collectors that I posted on RPM 

In assaying lead is used as a collector metal - in smelting copper &/or silver are the common metals used for collecting 

Silver is a much better collector then copper for two reasons - first it does a better job of collecting & second it is easier to part the gold from &/or PGMs with the exception of palladium due to solubility of Pd in nitric (whether direct dissolving in nitric or running a silver cell)

To better understand what I mean by silver doing a better job of "collecting" you can do an experiment - melt some silver "powder" in a melting dish - you will get some silver that forms balls/beads on the walls of the dish - now - once you have a nice molten pool of silver in the bottom of your dish rotate the dish around & watch the pool of silver "suck" up the balls/beads with an almost vacuum like effect as it makes contact with the balls/beads

Now - do the same thing with some copper powder (the powder helps to cause the beading you want for the experiment) now try rotating the molten copper pool to collect the beads - you will see that the copper pool does not "suck" the beads up like the silver did & that you actually need to use some jiggling of the dish in order to create some force in the copper pool hitting the beads to get the copper pool to collect all the beads

What that means is when using copper as your collector - you need your flux/slag to run "more" fluid so that you get better "circulation" in the crucible in order for the copper to do its job of collecting --- so - thinning becomes more important with copper smelt collecting & the prevention of metals hanging up in the slag 

Kurt


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## bmgold2

Are there any other "thinning agents" besides Calcium Fluoride?

I have been playing around with trying to cupel a tiny piece of sterling silver with some store bought flux. I have been using a MAPP gas torch running on propane from a 20# tank. That did get the lead beads to form from the flux but getting the lead to reduce and soak into the tiny homemade cupels is taking a long time. Since I used silver and not gold for this experiment, it is hard to tell when all the lead is gone. The remaining bead has not "sprouted" when it cools so it either isn't absorbing oxygen from the torch flame (probably not an oxidizing flame) or there is still copper or lead in the bead and not pure silver.

The whole idea was from the Butler torch assay manual. I was just trying to use a more portable torch than oxy/acetylene. I'm convinced that a chemical test will be better for what I was looking for but the torch assay and smelting has always interested me.


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## 4metals

The list that Kurt has posted is a rather complete list which can be found in some of the older assaying texts. The list I posted contains a some but not all of those ingredients. The reason I left some out is because they are obscure and rarely used and the reason I left lead and lead oxide out is, well because it's lead. 

Lead is used as a collector in fusion assays and it is very effective. It is also added in ratios greatly in excess of what we will add in a smelt, so it is effective but you need a lot. However fusion assays are followed up with cupellation which removes the lead and absorbs it into the cupel along with base metals. If we were wanting to refine large lots in 3 to 5 gram increments, that would be wonderful but not practical. In general for smelting you don't want to add anything that will be an issue to remove later on. 

Silver is a better collector and I encourage readers to try the little experiment (that Kurt proposed above) involving the beads collecting in a melt dish just to see it. The silver is a better collector in the absence of flux because, being noble, the little balls of silver don't oxidize while the little balls of copper get an ever so slight oxide surface which makes them not as efficient at coming together. However, add a few grains of flux to the little test and you will see, as Kurt mentioned, that slight resistance is gone.


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## kurtak

4metals said:


> Silver is a better collector and I encourage readers to try the little experiment (that Kurt proposed above) involving the beads collecting in a melt dish just to see it. The silver is a better collector in the absence of flux because, being noble, the little balls of silver don't oxidize while the little balls of copper get an ever so slight oxide surface which makes them not as efficient at coming together. However, add a few grains of flux to the little test and you will see, as Kurt mentioned, that slight resistance is gone.



Correct - When smelting - the copper gets the surface oxidation when the smelt load is heating up & before things become molten - this surface oxide does not just "suddenly" go away as the load becomes molten - like any chemical reaction it takes time for the reaction to work (in this case for the copper oxide to dissolve & go off in the slag) as the load becomes molten it starts forming beads/balls of molten metal & in the case of copper the beads have the surface oxide on them - the more fluid the flux is when the whole load becomes fully molten the more effective the chemistry of the flux is at dissolving the oxide away so that when the beads/balls contact the pool of metal forming at the bottom of the crucible the pool will collect them 

It is important to have a fluid flux whether smelting with silver as your collector or copper as your collector - it just more important if copper is your collector

I was made aware of this when reading my book on fire assay (Fire Assay Home Study Course) from Action Mining - which states --- "When using copper as a collector, the proper constitution (thinning) "must" be produced that will allow circulation within the crucible to cause the ore to come into contact with the pool of copper at the bottom" 

And by the way - I *highly recommend* that anyone wanting to get into smelting to get a book(s) on fire assay - smelting is a part of fire assay & so a good book on fire assay is like reading Hokes for a clear understanding of the wet chemistry - where as a book on fire assay will give you a clear understanding of smelting

Kurt


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## kurtak

General Flux Chemistry &/or purpose

As already mentioned flux preforms different tasks for the purpose of allowing certain impurities to be carried off in the slag leaving you with molten metals that can then be separated from the slag when poured to a cone mold

The separation of the impurities is made possible due to chemistry taking place in the crucible when the flux becomes molten --- or in some cases at different temps such as in the case of converting silver chloride to silver wherein soda ash is used as the flux but you need to bring the Na3CO2/AgCl mix up to a temp just below the melting point of the Na3CO2 (I believe 800F - will have to double check that) & hold it there for a time for the chemical reaction (reduction) of the AgCl to Ag & then after the reduction has taken place raise the temp to finish the flux/Ag molten stage of the smelt

The amount of impurity separation you can achieve depends on the make up of the material you are smelting as well as on the make up of the flux ingredient - organics for the most part are not a problem - however when it comes to metals & there complex's it another story because some metals can "at least to a degree" be oxidized & slagged off & on the other hand some metal complexes will under go reduction & end up in the metal as a part of the metal alloy

So the separation of impurities has limitations based on the material being smelted along with the ingredients in the flux make up & the chemical reactions they are preforming

The reactions (tasks &/or flux chemistry) taking place in the crucible are oxidation - reduction - complexing --- the problem being that generally these reactions are in combination with each other - meaning that while some things in the smelt are being oxidized - something are also being reduced & yet other things are being complexed - "depending on the material being smelted" - you can "influence" the task you want preformed in the smelt - whether it be oxidation, reduction or complexing by adjusting &/or adding different ingredients to the flux make up based on the material being smelted --- the less complex the material the better you can control your smelt out come with your flux composition (ingredients used in your flux make up)

Examples - AgCl (as mentioned above) a less complex material (you just need to break the chloride bond to achieve the reduction from AgCl to Ag) & you only need soda ash as your flux to achieve reduction with smelting --- now on the other hand - incinerated circuit boards which is a more complex material because of organics, metals & most likely metal oxides so your flux ingredients also become more complex - starting with your basic flux of borax/soda ash which as a complexing flux will slag off the organics - but it will also cause some oxidation of some metals but also some reduction of some metal oxides depending on what metals &/or oxides are involved - so besides upping the soda ash &/or adding fluorspar for thinning you may want to add cryolite if the ceramic capacitors are left on the boards &/or you may want to add charcoal (carbon) to help reduction (prevent oxidation) of base metals acting as your collector &/or add some potassium nitrate to effect better oxidation of things in the smelt --- or you can add silver as your collector along with litharge to oxidize the base metals leaving you with PMs collected in silver instead of copper --- in other words you can "influence" to a point the out come of your smelt with adjustment of flux ingredients

In the list of flux ingredients you see that some are acidic some bases & some neutral & they preform tasks of oxidation or reduction all of which is kinda self explained but then there is also the complexing fluxes - I have kinda explained this but will try to do a better job here

Complexing fluxes are fluxes that preform both oxidation & reduction in the crucible - what that means is that they (complexing flux) can perform ether oxidation - or - reduction --- depending on what it is they are reacting with - in other words they may oxidize one component of the material while also reducing another component of the material being smelted - or - they cause more oxidation but also some reduction or visa versa

In other words - a complexing reaction in smelting is like a redox reaction in wet chemistry - redox being both reduction & oxidation taking place in the same reaction

A good example of a redox reaction in wet chemistry is cementing silver with copper where in the copper is being oxidized (dissolving & thereby going into a copper plus state of copper nitrate) & at the same time in the same reaction the silver is being reduced from its silver plus state (silver nitrate) to elemental silver

A good example of a complexing reaction in smelting is using iron to smelt silver sulfide to silver with soda ash as the flux - the sulfur in the silver sulfide oxidizes the iron (putting it in an iron plus state) which in turn reduces the silver sulfide to silver with the iron (plus) then being carried off by the soda ash flux to form the slag

Kurt


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## alexxx

A few more questions...

- neutral flux & neutral flame
Not sure if I understand it the right way. But a neutral flux/flame will accomplish nothing on the "chemistry" taking place during fusion. No reduction nor oxidation. A neutral setup would be used in a scenario where one would simply want to melt and recast. Like when 4metals suggests making an anode from previously poured shots. In this scenario, I have no oxides to remove, no base metals to oxidize further and I dont want to lose copper.

- when to stop the melt
for anyone wanting to introduce forced air/oxygen into a molten pool to drive oxidation of base metals. Or simply in a scenario where I want to oxidize my base metals and want to preserve as much copper as possible. What signs are telling me that it's enough? When do I know that most of my base metals are gone and I need to stop the reaction taking place to save the copper? When do I know that I have removed enough slag and I dont need to add more flux to clean the melt further?
Any specific signs ? Color of the slag ? Color of the molten pool? Color of the cold alloy? 

-Lead as a collector
Kevin posted many procedures on recovery/refining using lead /PbO as a collector (+ silver also).
How viable is this route for the magnetic fraction removed from the fines & oversizes?
I prefer the approach of cupellation & parting instead of skimming the pool of oxidized lead on the final stage in order to drive the lead.

edit : 1 more here 

- Is it possible to change the type of flux during the same melt ?
Let's say I first want to get rid of a maximum of base metals by using a oxidizing flux & flame, than, after skimming a few times my slag full of base metal oxides I want to introduce a reducing agent in the melt, is it practical ? Is it something that is done ? Like a 2 stage smelting to get the benefits from both oxidizing & reducing agents after the complexing fluxes have worked to their full potential ?


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## mls26cwru

This is a phenomenal post guys! 

I have had a number of questions about smelting over the last year but never really got to into it because I don't have a furnace... Recently I have been toying around with the idea of building on to test out some smelting. Thanks you so much for the ideas and information. Are there any books on the subject matter that you guys would recommend for home reading/studying?

I am closely following this thread, so thanks again guys!


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## Lou

Great information! 

One quip on the AgCl conversion via carbonate:

"The separation of the impurities is made possible due to chemistry taking place in the crucible when the flux becomes molten --- or in some cases at different temps such as in the case of converting silver chloride to silver wherein soda ash is used as the flux but you need to bring the *Na2CO3*/AgCl mix up to a temp just below the melting point of the *Na2CO3*(I believe 800F - will have to double check that) & hold it there for a time for the chemical reaction (reduction) of the AgCl to Ag & then after the reduction has taken place raise the temp to finish the flux/Ag molten stage of the smelt"

The AgCl is actually the solvent for the carbonate. I should emphasize that is imperative NOT to "finish" it off in that fashion though Kurt. You will have silver losses, greatly damaged crucible and quite a bit of unnecessary and unhealthy smoke.

This is what is occurring:
(1) 2AgCl + Na2CO3 → Ag2CO3 + NaCl
(2) Ag2CO3 → Ag2O + CO2
(3) 2Ag2O → 4Ag + O2
Reactions (2) and (3) occur by thermal decomposition (disproportionation to the elements). The silver carbonate of reaction (2) will completely decompose by 225°C. The Ag2O of reaction (3) completely decomposes at 340°C.

Wasyl Kunda optimized this procedure and found that the ideal holding range for conversion is 500-600 C. Too high and sintering of the silver cake occurs and it is difficult to leach out the NaCl, too low and the reaction is either incomplete or very slow. Time is dependent mostly on how long it takes the middle portion of the AgCl to melt and react with the solid carbonate. 

In any event, if using this method, the silver should be leached in hot water before subsequent melting to remove the NaCl.


As for books to recommend--anything to do with fire assaying.

As for Alexx's question about when to stop the melt, that's kind of difficult to do--there is a lot of visual feed back but not as much as with the Miller chlorination process. When I used to do this, I would test it out in a #16 SiC crucible with SiC pipe to supply the compressed air. When melting 5K oz heats for anodes, you can pin tube a sample, quench and XRF to follow the progress of the removal of the Sn(basic flux)/Cu(borax)/Pb(borax/silica). Rocking reverbatory furnaces are of course ideal for this, but silver does report to the bag house and refractory erosion is always an issue. It is possible to take a bunch of "low" grade (say 70-85% Ag basis) and upgrade to the high 90s and preserve electrolyte life. Little silver is lost and usually paid upon when the copper/tin slags go off for refining. 

A similar process can be done for deoxidation of silver (or copper) by sparging with methane, town gas, or hydrogen.


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## richard2013

Just a clarification calcium fluoride or calcium fluorite? Am having trouble where to buy these please


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## 4metals

It is calcium fluoride also called Fluorspar.


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## 4metals

Lou said:


> A similar process can be done for deoxidation of silver (or copper) by sparging with methane, town gas, or hydrogen.



Now that's a horse of a different color. 

Care to go into a little more detail Lou?


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## g_axelsson

I was going to say it sounded like the classical method of poling to remove oxide from copper by sticking fresh tree poles into the melt. When I googled it first and found the wikipedia article https://en.wikipedia.org/wiki/Poling_%28metallurgy%29 I realized it was the same process that Lou is talking about.

Göran


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## ericrm

when you are blowing gazes into a melt ,what do you use for the part tha goes inside the crucible? do anyone have a picture to help me visualise it?


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## 4metals

> when you are blowing gasses into a melt ,what do you use for the part that goes inside the crucible?



usually a quartz glass tube

http://www.technicalglass.com/product_pages/fused_quartz_tubing/fused_quartz_tubing.html


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## ericrm

thank you for the answer and... for the corect spelling it made me laught and im kind of stress right now and i have apreciated it.


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## kurtak

Lou

Thank you for clarifying the AgCl smelting --- I have only done it once & that was quite some time ago - I followed these instructions by samual-a (wherein Sam says to bring it up to the decomposition temp & then when decomposed take it up to melt temp) :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=15882&p=160137&hilit=smelting#p160137

This was back before I had a silver cell set up so I was still making AgCl deliberately & doing the lye sugar conversion so tried the smelt method in the link above - shortly after I got my cell set up & quite making AgCl deliberately

I do have some that has been accumulated from testing solutions etc. so may give it another try based on the info you just posted just for the learning experience

Kurt


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## kurtak

4metals said:


> when you are blowing gasses into a melt ,what do you use for the part that goes inside the crucible?
> 
> 
> 
> 
> usually a quartz glass tube
Click to expand...


Or these :arrow: http://www.morganmms.com/produtos/produtos-para-fundi%C3%A7%C3%A3o/degassing-tubes 

Or :arrow: http://www.morganmms.com/products/foundry-products/degassing-rotors

Kurt


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## kurtak

When first started posting about smelting on RPM it was because a guy was trying to smelt some boards by simply putting them in his furnace & bringing it up to melt temp - after posting the info I have copied to this thread he then asked --- why can't you just put the boards in the crucible & add the flux - why do you have to incinerate & mill first 

Though the answer to that (for most) may be obvious - it was actually a good question prompting my following answer -----------

There are "several" reasons why you incinerate & mill the circuit boards first 

First & foremost is that you "need" to break down the chemical composition of the epoxy resin - epoxy resin & its hardeners are just that - "compositions of chemicals" - including acids --- when you heat epoxy (to the temps we are talking about with smelting) chemical reactions of the epoxy its self take place (reduction) producing a wide range of (chemicals) gasses &/or vapors (some of the vapors being acidic) --- as these gasses & vapors are released in the higher smelting temps they are going to produce chemical reactions of there very own thereby having a direct effect &/or altering of the "desired" smelting flux chemistry --- in other words if you don't first incinerate it will cause unknown & most likely undesired reactions to occur

Incineration of CBs is the same principal that is often used with ores by first (before smelting) doing a reduction &/or oxidation roasting to them to drive off (for lack of better term) chemical components that can cause undesirable reactions in your smelt & its flux chemistry 

Incineration drives off the chemicals that make up the epoxy as gasses & vapors thereby "reducing" it to ash - ash being comprised of sodium, potassium & calcium all of which are readily handled by your basic flux composition (borax/soda ash)

Also - because incineration reduces the epoxy to ash you can reduce its particle size with milling --- just like with wet chemistry particle size plays a roll in both the time & how hard the process has to work to do its job --- it takes more time to dissolve a chunk of metal with acid then dissolving fine powders of metal & the acid has to work harder on the chunk then on the powders (which is why we usually add heat when dissolving solid metals) 

The same is true with smelting - the finer the ash, silica (fiberglass, etc.) ceramic (ceramic capacitors) etc. is - the less hard the flux has to work to slag off the impurities & that means less time for the smelt to do its job & that means the less time it is in the crucible which in turn gives the flux less time to work at destroying the crucible

Also - having the flux "well mixed" with the material being smelted is important & again can be compared to wet chemistry - if you have say a 1/2 inch of metal powders covering the bottom of a beaker - when you first pour you acid in you get a real good reaction (lots of foaming etc.) but then it settles down & slows down working at dissolving just the metal on top that the acid is in contact with but not the metals in the middle &/or bottom - now give the metal powders a good stir so they lift off the bottom up into the acid & the reaction will take off with more aggression again because the acid is now making better & more complete contact with all of the fine metal particles (its more homogenized) 

So pre-mixing the flux & material to get it homogenized to start with is just more practical then trying to do it during the smelting - which for one thing would require un-necessary opening of the furnace

And finally - by incinerating & milling you can now concentrate the material you are smelting down to a higher concentration of metal & lower concentration of organics which in turn reduces the amount of flux needed to slag the organics off in order to melt & collet the metals you are after - in other words you not only reduce the volume of material to be smelted - but the amount of flux as well which in turn reduces the amount of slag produced

So as you can see - incineration & milling play a BIG & important roll in the process before smelting

Kurt


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## alexxx

How carbon can affect your melt ?
Let's say that your incineration is incomplete and lots of carbon remains in your ash.


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## butcher

How carbon can affect your melt ?
Let's say that your incineration is incomplete and lots of carbon remains in your ash.

Carbon is a reducing agent in a melt. 

With carbon or materials in a flux, like sugar, sawdust, or flour that will break down into carbon with the high temperatures, the carbon acts as a reducing agent, lets look at reducing copper oxide in the melt.
Copper oxide + carbon
CuO + C --> Cu (s) + CO (g)
2CuO + C --> 2Cu (s) + CO2 (g)

Above we see where the oxidized copper salts of copper oxide (CuO) is reduced to metal copper {Cu (s)},in the melt, with carbon (C), in this reaction this results in (-->), the carbon (C) removes the oxygen (O) from the copper oxide (CuO) to form carbon oxide gas {CuO(g)}, or carbon dioxide gas {CO2(g)},and the metal copper {Cu(s)}, depending on the ratio of the carbon and the oxides or oxygen of the melt.

Many metals salts or oxides above copper in the reactivity series can be reduced to metal by carbon in a melt.
Some metals are so reactive that carbon will have a hard time reducing them.
Then we also have some of the very reactive metals which cannot be reduced at all by carbon in a melt.
This is why in many reactivity series of metals we see carbon added in the list of reactivity.

Carbon can also take oxygen from other sources like the oxidizing nature of the flame of your torch, say you are trying to oxidize a metal with the torch's oxidizing flame, and you have carbon involved in your melt (or flux), the carbon will take the oxygen so that you may not be able to use the torches flame as an oxidizer, carbon in the melt may also take oxygen from other ingredients in your melt, like an oxidizing agent or flux (PbO, KNO3...).

Lets take lead oxide (litharge) for example.
Say we have added litharge (PbO) to a melt for two reasons, for an oxidizer to oxidize base metals, and in doing so becomes itself a metal of molten lead to collect the values in the melt.

Having carbon in the melt or an added ingredient of the flux, can counter-react with the oxidizing nature of our oxide in the lead oxide (litharge), where we may not be able to oxidize the base metals in this melt, with too much carbon all of the metals that can be reduced by carbon could be reduced with the lead, and remain with our values, defeating one our our purposes for choosing litharge (lead oxide) in our flux, instead of the choice of using metal lead in the melt.

Everything that can react in the melt can, or may react, some metal oxides can act as oxidizers for other metals, as well as oxygen from the air, or even from your heating source, like air from the atmosphere, or oxygen from your torch or burner.
Metals can act as reducing agents in the melt, or oxides of metals can act as oxidizing agents in the melt.

Salts of metals like silver chloride can act as an oxidizing agent for many metals, even gold (which normally is very hard to oxidize), with AgCl in the melt the gold can more easily be oxidized, where some of our gold can vaporized off as gold fumes causing loss of values from the melt as a chemical reaction of the melt. A flux like sodium carbonate and controlling the temperature during the melt can help to chemically react with the silver chloride converting the silver to metal and the chloride to a salt or fumes of chlorine gas, so that the silver chloride does not react with our gold as easily.
Flux ingredients like carbon, can be chosen to change these chemical reactions.

For example we may wish to add a strong oxidizing agent like KNO3, to a melt high in carbon to chemically react with the carbon, so that we can oxidize the base metals in that melt...


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## 4metals

alexx said:


> How carbon can affect your melt ?


Smelting is a process not unlike a chemical reaction you have going on in a beaker in your hood. Except it happens at a higher temperature, much higher. But let me phrase the question a little differently, because more of us can relate to the beaker. 

So why don't you just keep shoveling in the sodium metabisulfite when you drop the gold until no more goes into solution? Unfortunately we do get questions on the forum like this and every time, they are asking because they made a mess. But why a mess? Because the sodium metabisulfite is selective to reduce the gold, to a point. Too much brings on unintended consequences.

Well carbon is also a powerful reducing agent, and if we knew how much was in there to start with we could possibly use it to our advantage. But in most cases there is too much. So just like the beaker example of adding too much metabisulfite, not knowing how much carbon is in the ash to start can lead to problems. Refiners, and smelters, like to work under controlled conditions when possible. By eliminating carbon by incineration, we can now add flux components in a way to better control our results. We can add some carbon, but we know how much and can measure its effect.

Whenever I had large smelt lots, I always fused small samples to determine the best flux combinations and applied that to the entire batch. In sweeps fusions they call that determining the reducing power of the flux. By using this procedure I knew what proportions would give the best results and that little bit of analytics could be applied to the entire lot. 

So to summarize, we like to get rid of as much of the carbon as possible so we can selectively add flux components to attain predictable results.


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## Lou

4metals said:


> Lou said:
> 
> 
> 
> A similar process can be done for deoxidation of silver (or copper) by sparging with methane, town gas, or hydrogen.
> 
> 
> 
> 
> Now that's a horse of a different color.
> 
> Care to go into a little more detail Lou?
Click to expand...



Yes, but it's a horse worth betting on if you seek to produce a high purity product on more than a metallics basis. This method I have done on pure silver to remove the oxygen from the silver. Many large refiners that we both know have oxygen issues with their silver product. I attribute it to two things: 

1. Poor atmosphere control during granulation and casting (I always shotted under an H2 flame with Ar over the top to which I fed the silver crystal).
2. The direct remelting of pure silver solids that had been melted once or more before in uncontrolled conditions or "clean up silver" done upon feeds like silver/Ag2S flake that is done with nitre and borax but specs at 3N. This is to say that some large volume refiners may not refine every feed material. 
The oxygen is undesirable for more than cosmetics: oxygen saturated solid silver does not have the physical or electrical properties.

For the lowest O content (and impurities in general), one can have no better material than large crystals out of the silver cell. Silver sponge made with formate always carries more O content, similarly with cement silver. I do not know why. Maybe it has to do with atmospheric absorption. In any event it may be remedied in several fashions, but the easiest is:

by sparging the melt with an iron pipe (driven to a half inch of the bottom of the crucible) and a reducing gas through the silver for a period of time sufficient to deoxidize it. In some instances the silver will react violently to the treatment at first. When the melt quiets down the pure silver may be cast into finished bars with no eruption of oxygen from the cooled bar top surface. If conducting this treatment on copper, a silica pipe is used. 


Excess carbon that survives the incineration process is usually detrimental to the coalescence of the melt because it forms gas pockets. One will observe popping at the top of the melt/flux as the carbon gets oxidized into CO then CO2.

So much with smelting is situational, and I echo 4metals' advice that small samples should be tested first to optimize the process. This is to ensure no "prill holdup" in the slag. Slag chemistry and slag temperature dictate slag viscosity which is what determines if all the values pool or get held up.

Lou


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## Barren Realms 007

Lou said:


> 4metals said:
> 
> 
> 
> 
> 
> Lou said:
> 
> 
> 
> A similar process can be done for deoxidation of silver (or copper) by sparging with methane, town gas, or hydrogen.
> 
> 
> 
> 
> Now that's a horse of a different color.
> 
> Care to go into a little more detail Lou?
> 
> Click to expand...
> 
> 
> 
> 
> 
> The oxygen is undesirable for more than cosmetics: oxygen saturated solid silver does not have the physical or electrical properties.
> 
> 
> 
> 
> 
> 
> Lou
Click to expand...


Lou can you point me to some information on the fact that the silver lacks the electrical properties because of the oxygen content? I'm not saying you are wrong in this I would just like to read up on this if you have a link to an artical on this. Is this true for just impure silver that needs to be run through a cell or is it true for silver that has been run through a cell also?

Thanks


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## butcher

I cannot point to specific papers, and I cannot say about oxygen in silver (silver oxide) crystals?
But in electrical contact points silver oxide can be a problem silver points can burn up easier or hold the arc longer while the points open burning the points up faster or being unreliable, example a higher resistance across the points and a higher amperage of the circuit... 

Many contacts, or switches are made to mechanically "wipe" as they open or close to clear them of an oxide film, which can degrade the continuity.

Many times the silver has other metal or even metal oxides added to change the properties of the silver to better suit their use in different electrical or mechanical conditions.

It makes sense that the oxides or salts of metals would not be as good of a conductor as the metal, and that if the metal has an oxide film or oxide crystals in its structure it would not be as reliable of a conductor as a more purer metal.

Electrical copper (wire bus bars...) is normally a fairly pure copper metal, if the copper had more other metals involved its resistance or mechanical property could change to the point of not being reliable or uniform for the use in electrical application...

I suspect similar to gold in the jewelry industry, or the metals electronic industry, the purity of the metal becomes very important, especially in electronics as we are running lower current circuits and faster frequency's in the digital switching or pulses...


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## alexxx

Smelting the magnetic fractions

It has been discussed how to smelt the non magnetic fractions of circuit boards.

After sieving and magnetic separation, how do we process the magnetic oversize pieces that remains ?

Lead smelting ? Is there another way to achieve a decent recovery ?
Chemical leaching ?

Any metals worth retrieving besides precious metals ? Nickel maybe ?


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## Barren Realms 007

butcher said:


> I cannot point to specific papers, and I cannot say about oxygen in silver (silver oxide) crystals?
> But in electrical contact points silver oxide can be a problem silver points can burn up easier or hold the arc longer while the points open burning the points up faster or being unreliable, example a higher resistance across the points and a higher amperage of the circuit...
> 
> Many contacts, or switches are made to mechanically "wipe" as they open or close to clear them of an oxide film, which can degrade the continuity.
> 
> Many times the silver has other metal or even metal oxides added to change the properties of the silver to better suit their use in different electrical or mechanical conditions.
> 
> It makes sense that the oxides or salts of metals would not be as good of a conductor as the metal, and that if the metal has an oxide film or oxide crystals in its structure it would not be as reliable of a conductor as a more purer metal.
> 
> Electrical copper (wire bus bars...) is normally a fairly pure copper metal, if the copper had more other metals involved its resistance or mechanical property could change to the point of not being reliable or uniform for the use in electrical application...
> 
> I suspect similar to gold in the jewelry industry, or the metals electronic industry, the purity of the metal becomes very important, especially in electronics as we are running lower current circuits and faster frequency's in the digital switching or pulses...



Yes I know all of that because I am a master electrician. I was more curious about the following statment :

"The oxygen is undesirable for more than cosmetics: oxygen saturated solid silver does not have the physical or electrical properties".

And how it effected the electrical properties.


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## 4metals

I know that years ago I ran a large electroplating shop, we did a lot of silver cyanide plating. The anode stubs that come from the undissolved pieces which remain above the solution level as the anodes dissolve were always melted down and cast into bookmolds to make new anodes from the residues. Because of the way we melted them, in a gas furnace with no gas cover to prevent oxygen absorption, the recast anodes were not oxygen free.

There was a huge difference in the performance of oxygen free anodes vs. the recast anodes we made. The recast anodes dissolved in a way that produced scales which flaked off into the anode bags while the oxygen free anodes dissolved beautifully and left a nice crystal pattern on their surface. To the point where the oxygen free anodes did not need to be bagged but the recast anodes did. So there was definitely something electrical going on because it was essentially the same silver just recast in a way that did not exclude oxygen absorption.


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## Barren Realms 007

4metals said:


> I know that years ago I ran a large electroplating shop, we did a lot of silver cyanide plating. The anode stubs that come from the undissolved pieces which remain above the solution level as the anodes dissolve were always melted down and cast into bookmolds to make new anodes from the residues. Because of the way we melted them, in a gas furnace with no gas cover to prevent oxygen absorption, the recast anodes were not oxygen free.
> 
> There was a huge difference in the performance of oxygen free anodes vs. the recast anodes we made. The recast anodes dissolved in a way that produced scales which flaked off into the anode bags while the oxygen free anodes dissolved beautifully and left a nice crystal pattern on their surface. To the point where the oxygen free anodes did not need to be bagged but the recast anodes did. So there was definitely something electrical going on because it was essentially the same silver just recast in a way that did not exclude oxygen absorption.



Ok now that train of thought makes sense.


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## Lou

Frank, I was told that by a company I sold very high purity silver to, they said the same of gold. I guess interstitial impurities affect the resistivity(?). I'm no physicist, I just figure out how to get a material to fit an application or specification. 

I guess that silver oxide disrupts the flow of electrons to some extent. Maybe like it does for copper:

https://en.m.wikipedia.org/wiki/Oxygen-free_copper

It (O) also seems to be bad for many other metals' physical properties. C, H, N, and O are usually on the spec list for me.


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## Barren Realms 007

Lou said:


> Frank, I was told that by a company I sold very high purity silver to, they said the same of gold. I guess interstitial impurities affect the resistivity(?). I'm no physicist, I just figure out how to get a material to fit an application or specification.
> 
> I guess that silver oxide disrupts the flow of electrons to some extent. Maybe like it does for copper:
> 
> https://en.m.wikipedia.org/wiki/Oxygen-free_copper
> 
> It (O) also seems to be bad for many other metals' physical properties. C, H, N, and O are usually on the spec list for me.



Yea I understand. Theoretcly it it would make sense to me with what 4metals said it does. I was thinking how it would effect it along the line of use in electrical components in which case it probably would not come into play because the manufacturer should know this. But with running silver through a cell I can see now where it would come into play and might pop up in a question from a forum member as an answer to a problem that might be encountered.


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## 4metals

What Barren just said gave me a thought. Everyone casting anode material for silver cells does it by melting and casting without protection from the oxygen in the air surrounding us. So in theory all silver cell anodes have a degree of adsorbed oxygen in them. I have noticed that the copper in sterling makes it behave beautifully and it never seems, I guess seems is the operative word here, to behave as pure silver melted under the same conditions reacts. 

However silver anodes in silver cells (Moebius cells) do slough off and behave in a similar fashion to those recast pure silver anodes I mentioned. And the solids remaining in the anode bag as slimes is always a high percentage silver. I wonder if an anode was cast to be oxygen free if it would dissolve better, faster, and with less silver scale in the anode bag. That could eliminate a large pain in the butt factor in cleaning up anode slimes! Worthy of playing around with I think.


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## alexxx

oxygen sparging to oxidize base metals during smelting.

It was mentioned that O2 could be slowly injected into molten metal during the smelting in order to oxidize base metals and have them driven into the slag.

A few questions here ;

Any additional stirring needed during that process or the sparging is enough to move the pool of metal around and have the O2 in contact with a maximum of metal ?

4Metals has mentioned the use of a quartz glass tube to inject the oxygen into the melt. Any other material could be used to handle the high temperature and the oxidizing nature of the melt ? An alumina tube maybe ? What about a stainless steel tube ?

I understand that O2 sparging might be quite dangerous. What type of appartus is usualy used to control the debit of the injected gas ? A simple regulator ? What debit / pressure would you guys use for a pool of 100 lbs of molten metal and a 10mm diameter tube (material being again ashes & oversize non ferrous from circuit boards)?

Would you suggest to simply use embiant air or an O2 concentrator is preferred for the task ?

How long would you keep injecting O2 into the melt & slagging off ?

cheers !

Alex


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## 4metals

I prefer quartz glass but Morgan materials makes gassing tubes as well
http://www.morganmms.com/produtos/produ ... sing-tubes

When gassing I have used room air pressurized and pumped into the melt, and I have used compressed oxygen. Whichever you choose, start slowly and only begin with a slow bubbling of gas reaching the surface of the melt. Depending on what you are starting with, gassing can take from a half hour up to hours. 

The compressed oxygen obviously delivers more oxygen into the melt which can result in shorter gassing times but I have had good success with compressed air. I will always defer to simplicity. 

I like to periodically ladle off slag and pour it into a cone mold. This way you know if you are pulling out metal as it settles quickly in the molten slag and can be collected at the bottom of the mold. 



> a pool of 100 lbs of molten metal, material being again ashes & oversize non ferrous from circuit boards



Typical PCB metallics are very high in copper to begin with, you are choosing the wrong path if you expect to oxidize all of the copper into the slag, copper is the last to go and usually remains with the PM's. This material is usually shipped to a copper refiner as it produces a homogeneous bar which can be sampled and quantified easily. The copper refiner will upgrade this material to high 90's% copper and refine the copper out electrolytically and segregate the PM's in the slimes. Or you can build a copper cell and refine it yourself.


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## alexxx

4metals said:


> Typical PCB metallics are very high in copper to begin with, you are choosing the wrong path if you expect to oxidize all of the copper into the slag, copper is the last to go and usually remains with the PM's.



The goal is only to remove other base metals besides copper to obtain a 95%+ copper anode quality alloy at the end for a copper cell. 99% prefered, even if it implies a lost of 5% in the copper content.

It was pointed out that copper will react in a different way than other base metals with this procedure, a small % will be oxidized and lost to the slag while a great % of other contaminants such as Zinc, Nickel, aluminum, tin would be removed.

I believe I could live with a sacrifice of a few % in the copper content to save a lot of troubles in prematurely fouling the electrolyte from the copper cell.


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## 4metals

For what you just suggested the oxygen sparging is fine and actually the preferred treatment. I just don't want you to think all of the copper base metal is going into the flux.


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## Lou

The nickel will stay with the copper.


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## 4metals

While the nickel will remain it is not a game ender. 

The nickel will dissolve in the copper cell electrolyte and not report to the slimes. However, since copper plates at a lower applied potential than nickel, the copper will plate out at the cathode and the nickel will accumulate in the electrolyte. So the copper you produce will be very high grade.

Soon I will start working on a thread about electrolytic copper refining.


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## alexxx

4metals said:


> While the nickel will remain it is not a game ender.
> 
> The nickel will dissolve in the copper cell electrolyte and not report to the slimes. However, since copper plates at a lower applied potential than nickel, the copper will plate out at the cathode and the nickel will accumulate in the electrolyte. So the copper you produce will be very high grade.
> 
> Soon I will start working on a thread about electrolytic copper refining.



Here comes the nightmare for me, and for many others I believe, even the big boys...
The Nickel build up in the electrolyte.

Any procedure known to deal with the Nickel at the smelting stage ?


----------



## 4metals

> Any procedure known to deal with the Nickel at the smelting stage ?



Sure, how many million do you want to invest in a flash smelter and a pair of oxygen top blown converters and finishers?

Nickel is tolerable in the electrolyte at a concentration up to 10 times higher than Iron. The upper limit is around 20 grams per liter. It comes down to how much nickel is actually in your copper doré? 

You will be running a copper electrolyte around 40 grams per liter copper and there are methods that have been in use for many years to separate the copper sulfate from the nickel sulfate but for small scale refining, the analytics may be a game breaker. Changing out the electrolyte may prove easier.


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## alexxx

Here's part of an assay from 4 types of pcb that have been prepared for smelting (pyrolized and milled).
Samples are from unsieved material (fines & oversizes mixed together).
No magnetic separation done yet, it sure will be an important step to get rid of some Fe & Ni.





The Ni & Zn values seems very high.
CRT-001 has a Fe content going trough the roof and was sent for processing at a secondary copper smelter.


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## 4metals

I do not understand how a representative sample was made for the analysis shown. Did you melt the metallics fraction into a bar and sample the bar? 

If they were prepared for smelting and unsieved, I don't see the sample as representative.


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## Shark

I would like to Thank everyone for their input on this thread. While I am in no way ready for smelting, I am a small step closer. A very small step, as this furnace is sitting on the bottom of a 10 gallon barrel. I hope to have a small crucible by the weekend to put it to a better test. I can fire it up and bring a 4 inch x 1/2 grade 8 bolt to red/orange hot in less than 3 minutes. I ran it for an hour today with no noticeable problems. It should help to advance my understanding of using a furnace better given time to practice with it.


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## FrugalRefiner

I posted a color vs. temperature chart in the Furnace Temperature Colors thread. At red/orange, you might be just short of the melting point of gold.

Dave


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## Shark

Thanks Dave. That chart will be handy in the future. If you look close you can see the head of a bolt sticking out on the right side of the furnace. That bright yellow looking spot inside is the end of the bolt glowing. I didn't make the furnace itself, but it has two holes so it could be fired using two propane torch's. I just made the burner, if all else fails, I will add another one just like it. I had to start someplace, and it was a lot of fun.


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## Shark

30 second video of it running in the dark, with bolt end still in place.

[youtube]http://www.youtube.com/watch?v=x62eVd2dgus[/youtube]


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## 4metals

If you didn't say what that video was i would have thought you got some amazing photo's of a meteorite hurling through space! 

I hope you do have, or intend to build a lid for the furnace, for that size furnace a hole in the cover about 1 1/2" will suffice. it is amazing how much heat a lid with a hole that large retains in the furnace.


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## Shark

It has a lid on it. The actual inside is 3 1/2" wide by 3 3/4" deep. The opening in the lid is 2 inch's wide. I had been thinking that the lid opening might be made a bit smaller to see if that would help retain some of the heat better. With out the lid it doesn't quite roar as loud.


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## modtheworld44

4metals said:


> If you didn't say what that video was i would have thought you got some amazing photo's of a meteorite hurling through space!
> 
> I hope you do have, or intend to build a lid for the furnace, for that size furnace a hole in the cover about 1 1/2" will suffice. it is amazing how much heat a lid with a hole that large retains in the furnace.



4metals

Umm...you might want to go back and cross reference with the picture of the furnace and the video,the lid is on it.Thanks in advance.

Shark 

Looks great,we'll see how well it can melt silver and gold when I come down tomorrow.I'll see how much gold I can round up between now and then,now that we have plenty of nitric it won't take to long to get some of my gold done.The silver is ready to go,I think we can get any kinks sorted out of it.I think the burner you built is going to work just fine.Thanks in advance for the picture and video.



modtheworld44


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## 4metals

> Umm...you might want to go back and cross reference with the picture of the furnace and the video,the lid is on it



OK, I see the ring around the OD where the lid starts and the body ends, I thought you cast it in a plastic tank with little ridges and cut off the plastic after it hardened. 

The reason I thought you had no lid is because your lid has no handle to pick it off the top easily. You do need to remove the lid to add flux and stir and in the course of using it flux will drip on the edge and sometimes it sticks to the top. Even with a handle it can require a yank to remove it. If you need 2 gloved hands to lift it off, you need to re-think it.

It is difficult to see get an idea of size, what is the OD of the furnace?


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## Shark

The external dimension's are 5 1/4" wide by 4" high with out the lid. With the lid it is 6" high. I have been using a large set of pliers to remove the lid, but I would prefer a handle of some sort made into the lid. If I were to make a new one some of the things I would add would be a handle for the lid, only one opening for the burner, brazed connections instead of silver solder, and make it bigger. I am sure there will be others as I go but it is all a learning process. I would like to make one in a gallon sized can dimensions just for more true smelting type tests.


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## 4metals

OK that is a little puppy! Nice job though. See there is a definate use for a beer can for reference in photographs. 

When I make cast lids I like to have a ring of metal around the perimeter. One way to do this would be to cut a metal can of the proper diameter down so it is as thick as you want the cover and cut off the end so you just have an empty "pipe" made from the walls of the can. Then get 4 screws and nuts and put one screw in every 90 degrees and put the nut on the inside to tighten it. when you look down the "pipe" you will see 4 screws stopping about an inch from center. These support the refractory so it doesn't fall out of the ring when you pour the cover. If I were making a furnace this small with walls as thin as you have made I would use a 2 inch length of black iron pipe of the same OD as the furnace body on the lid, and a longer length for the body of the furnace. 

If you add extra nuts to two screws opposite each other so about 1/2" of the bolt head sticks out, you can make a bail type handle which makes removal easy. Just make sure it can swing down and not stand tall and get heated by the flame. 

For the hole in a furnace that size I would use a toilet tissue tube in the form to cast the hole which should make it about one inch. And it burns out in the first heat!

Please post the details of the burner as a furnace this size could be a popular build for forum members. And which refractory cement did you use?

Nice job!


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## Shark

Burner orifice from a King Kooker cast iron burner assembly Model #WKAF2B. (I got mine at Academy Sporting Goods)
A 1/4" to 1/2" Copper reducer.
A 1 inch long piece of copper tubing.
A 6" piece of black iron pipe.
A 3/8" gas line cut off valve. Optional but I am liking it since I added one to mine.
A 8" x 3/16" steel brake line.

Using the orifice, I silver soldered the 1/4" x 1/2" copper reducer to the small end. (orifice end) The orifice is just about right to reach the wider part of the reducer without extending into the the wide area. I then silver soldered the 1 inch copper pipe into the reducer. Once done I drilled four 1/4" holes at right angles through the reducer right in front of the orifice. Take the 1/2 inch black pipe and test fit the copper tubing into it. It should be very tight, almost an exact fit. With a round file I worked the inside of the black pipe to open it up some. I worked the out side leading edge of the copper tubing only slightly, just enough to get a compression fit between it an the black pipe. Don't make it permanent just yet. I drilled a 1/4" hole 1 1/2" in front of the air holes in the copper reducer (this hole is in the black pipe). I cut both ends off the brake line and bent the last inch or so at an angle where the center line of the tubing is centered inside of the black pipe. Then I silver soldered it in place. I cut a strip from a drink can just wide enough to cover the holes in the reducer when lighting it. Once it warms up a little, I uncover the holes and turn the air compressor on.

There is one last piece, an air supply. I tried my small 2 gallon compressor but the regulator on it would not go down low enough. The next best thing I had on hand was a nebulizer. It works great, it is actually what I used in the video. When the air is turned off, the furnace runs completely silent. (I hooked the air line into the brake line.)

As for the furnace, another member, JHS, made it. He had sent it to me quite some time back but health issues had kept me from working with it. I know he has been down in health for the last few days, but maybe he can post up the mix he used for the refractory.


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## Shark

Let's see if I can word this right. If I understand correctly, the crucible needs roughly 1/4 or 25% of the crucible diameter as clearance around the crucible body when heating. This should insure better heat transfer to the material to be melted. This 25% should be measured from the top portion which should also be the widest part of the crucible. So a crucible with a 4 inch wide measurement (at the top) should have roughly a 1/2 inch clearance from the inside of the furnace all the way around. Since my furnace has a 3 1/2 inch opening the crucible should be in the neighbor hood of 3 inch's. Since 3" was unavailable from the local supplier, I went with a 2 1/2 inch diameter crucible. I could have ordered 3 1/8" graphite crucible, but went with the fused silica with a clay bond since he had these in stock. Now the real question is does all that sound about right? Also am I right in thinking that an undersized crucible would be preferred over one that was slightly to big?

Edit for clarity


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## Shark

Made a little progress today, but still have more to do before I am satisfied. After trying three different burners today, I am close. If I can melt copper, I will be happy. Here is the heat almost at it's limit earlier today and it would not quite melt copper.




Late this evening I got the copper to melt, but just barely. Changed burner to the third version which helped greatly. It still needs a bit of tweaking.




Last test for the night.




Finally some little success. Poured copper from a piece of pipe and legs from IC's.




Still a ways to go yet, but I am happy with most of the progress so far.


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## Barren Realms 007

Shark,

Take some bricks and close in the top of your furnace to to about half the size of the opening to retain more heat and it should solve part of your problem. Your hole in the top of your furnace is much larger than it needs to be and you are loosing a lot of heat from it. Once you find that this works better for you then you can have a metal plate made for it or make another top for it.


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## Geo

Yea, I agree. Use some fire clay and make a round puck a little larger than the vent hole. You can slide it across the hole until you have just the right gap. You will know because it will leave a blue flame shooting up through the gap that you may be able to see in the daylight.


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## Shark

I agree guys, the opening can stand to be a lot smaller. The skillet I poured into is one of those ash tray cast iron skillets. I had used it to partially cover the opening and the change was drastic. The color inside went from a orange-red to a yellow-white color very quick. I need to get better set up to control the air flow, and I think a high pressure regulator for the gas would make the move to a fully working furnace. (although quite small) I have been using a regulator from a gas grill, and powering the air from dual nebulizers. I do have an adjustable gas valve but it doesn't seem to give quite the control it needs.


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## Barren Realms 007

Shark said:


> I agree guys, the opening can stand to be a lot smaller. The skillet I poured into is one of those ash tray cast iron skillets. I had used it to partially cover the opening and the change was drastic. The color inside went from a orange-red to a yellow-white color very quick. I need to get better set up to control the air flow, and I think a high pressure regulator for the gas would make the move to a fully working furnace. (although quite small) I have been using a regulator from a gas grill, and powering the air from dual nebulizers. I do have an adjustable gas valve but it doesn't seem to give quite the control it needs.



Are you using propane or natural gas for your furnace? I will get you a picture of my furnace posted when I get a chance. It is a similar design to the furnace you have except for the burner assembly and it will eliminate the need for the nebulizer you are using.


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## Shark

I am using propane. I have changed the burner out to one of the Reil(?) type burners, but it still needs air assist to get hot enough. This is the current burner assembly I am using, it seems to work the best of the three. I scaled everything but the orifice size down by 1/2" to fit the small size of the furnace. My original worked great up to aluminum but that is about as far as I could seem to push it. 




Notice the paper still on the burner pipe. That paper stayed there after a continuous 4 hour burn and I could still hold my hand within 4 inch's of the furnace with out being uncomfortable.


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## FrugalRefiner

You might want to try a larger reducer. I can't tell if that's a 3/4" to 1/2" or a 1" to 1/2", but I'd suggest a 1-1/4" or 1-1/2" to 1/2". As close as the gas inlet pipe is to the 1/2" pipe, it may be restricting the air that is able to pass around the gas pipe.

Dave


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## Shark

Locally the largest single reducer I can find is 3/4 to 1/2. I had thought about using two to achieve a bigger opening but wasn't sure that would help. I just changed the regulator to a high pressure type and heating it up with no added air. I should know pretty soon what the effects that has on it pretty soon.

Edit: fix miss spell check,


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## upcyclist

Shark said:


> My original worked great up to aluminum but that is about as far as I could seem to push it.


I made a Gingery Furnace once upon a time that did aluminum really well, and that was with charcoal and a blowdryer 



Shark said:


> Notice the paper still on the burner pipe. That paper stayed there after a continuous 4 hour burn and I could still hold my hand within 4 inch's of the furnace with out being uncomfortable.


That sounds like good insulation and nice tight tolerances--good job!


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## Barren Realms 007

Here are some pictures of the furnace I use. It is about the same size and setup as yours. It is capable of holding a #6 crucible but I use a #4 in it.


In the first photo you will see that the exhaust opening is a lot smaller than in your furnace. The opening is 2" across and the two side slot are 2" long as well. Most of the time when I am running the furnace I will put a brick over the side slots just to retain heat and not use as much fuel. It doesn't really make much of a difference when I close the side slots off on how the furnace operates.




In this second photo you will see that my burner pipe is a 3/4" pipe with a 3/4" x 1-1/2" bell reducer on the end of it for the inflow of air for the fuel mixture. I have seen these furnaces also setup with an added air supply from a compressor or other source to generate higher heat temperatures. But I don't feel that is necessary for this furnace at this point with everything I have used it for




In the third photo you will see that the burner inlet is a little bit more to the side of the furnace than your is but I don't think that will have much of a difference on your furnace. The reason for the side inlet where it is is so that it will create a vortex motion of the flame in the furnace. I think yours is fine where it is.




In this fourth picture you can see a #4 graphite crucible next to a 300ml beaker for size comparison. This furnace will reach an operating temperature hot enough to melt this crucible full of copper powder in roughly 30-45 minutes from a cold start. Once it reaches its melting temperature the copper can be poured and another load added to the crucible and melt the charge in about 10-15 minutes. The furnace does not have to be run at maximum out put to accomplish this. When my furnace is operating you can not touch the sides because of the heat generated, you have to use gloves even when using the handles to remove the top.

Another tip on the crucible is to not use a cheap clay one when running this furnace, if you look at the picture looking down into the furnace you can see that I used a couple of cheap crucible and they failed during the melt. Go ahead and spend the money to get a graphite crucible. The one in the picture is a salamander crucible I purchased on ebay for about $20.00 if I remember correctly.





1. I think you need to upsize your burner pipe to a 3/4" with a bigger bell reducer on the end for incoming air flow.

2. You need to reduce your exhaust opening.

3. I'm also not so sure that your gas pressure might need to be increased at your burner pipe. I am guessing that the propane is being supplied by the tank that you use on your house and that you are running this at the same pressure that the appliances use inside your house. If this is the case I would look at separating the two lines and using a higher pressure regulator for the furnace than what is used for your house.

4. You should consider making a metal band to go around the lid of your furnace that has handles on it. This can easily be done by taking a piece of a metal can and cutting it the same height as your top on your furnace. Attach a couple of handles on it similar to what mine has with rivets or screws. Then take and drill 4 - 6 holes in the metal band and mark on the cement top where the holes are and then drill these out smaller than the screws that you can take and drill into the metal to attach to the top. This will make it a lot safer to deal with the top when you want to remove it.


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## Shark

I will have to try those suggestions. From all I have studied not many people seem to build them this small, that is why I went with a 1/2" build for the burner. I have the pipe here, but need the 3/4" to 1 1/2" reducer. I am running this one from a 20Lb bottle and have just changed to a high pressure regulator. I now have a cold spot in the crucible where the burn makes initial contact. I think I will wait and try to get the 3/4 burner going before fooling with it much more.


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## Shark

Frank, what is the size tubing you used for the orifice? It looks like 1/4 or 5/16 brass.


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## Barren Realms 007

Shark said:


> Frank, what is the size tubing you used for the orifice? It looks like 1/4 or 5/16 brass.



Looks to be a 1/4" brass nipple. The outside diamater is 3/8".


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## butcher

The orifice for propane is normally around a #55 (0.040) to #60 (0.052) drill bit, depending on the burner size.

You can find plans for that burner and many others on the internet. The simpler burners like that one work well if properly tuned.


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## FrugalRefiner

For decent prices and a wide variety of black iron and brass pipe and fittings, check http://www.zoro.com. My local big box stores only stock the stuff that would commonly be used. Zoro has a much wider selection. I've bought 1-1/2" to 1/2" and 1-1/4" to 1/2" from them. Be sure to look at all the different listings. Sone of the reducers are quite short and "blunt". Others are longer and more gradually tapered, and are much better for this use.

Dave


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## Shark

Thanks Dave, I could use one of those stores closer to home. It will help on another project I have rambling around in my head.

I did find a 1 1/4" x3/4" reducer yesterday and managed to get it set up with a 3/4" pipe. I used 3/8" copper tubing and a 3/64 drill bit for the orifice. It seemed a bit fussy on start up but worked great once it warmed up. After sitting in the furnace for over an hour without melting copper pipe, it hit me why it wasn't melting...  . I was running the gas at 1.5 PSI. There is a reason for using a gauge on the adjustable regulator, I just forgot about it at the time. As soon as it hit 5PSI, the copper melted in about 1 minute. Now I am wishing I had cleaned the ash tray of the previous attempted pour as the second attempt of the day would have been nice by its self. 





The second attempt was very liquid and poured easy and smoothly. I need to make/buy myself a small mold and learn some more about melting and pouring metal's harder than lead.

Edit: correct measurement


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## Barren Realms 007

Cut you a piece of angle iron and then cut some end plates for it that you can use a C clamp to hold the ends on to use as a mold for a cheap easy fix for now.

I use one similar to this most of the time.

http://www.ebay.com/itm/40-oz-Gold-Bar-Loaf-Cast-Iron-Ingot-Mold-Scrap-Silver-20-oz-Copper-Aluminum-/311530782533?hash=item4888ae7f45:g:7r4AAOSwqrtWn7nT


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## Shark

That ingot mold is nice. I had thought it a bit big, but these little crucibles will hold more weight than I thought. I ran a small experiment today and found at 1.5PSI for 20 minutes, then 3.5 for another 20 minutes then on up to 5PSI I will have my first melted copper (without stressing the furnace to much) in about 45 to 50 minutes. Like Frank mentioned I found my second batch to melt in 10 to 15 minutes. The more I learn about this the more fun it seems. 

Some time back someone in another post mentioned a corn mold thingy and this gave me an idea. 
(found it: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=24289#p257110 )
My first bars. They are only about 3" long.




Again, Thank You, to everyone involved for making this happen for me. This is one of my bucket list-milestone achievements.

Edited for link


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## Barren Realms 007

Glad the changes are working for you.

Where is that copper cemented from? If I didn't know better looking at the bars it looks like you have PM's in the bars, but that could just be rust I am looking at.


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## Shark

Some of the copper was from clean pipe used just for testing the furnace and burners. Some of it was from legs and wire from incinerated IC chips after running a magnet over them and removing the magnetics.


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## Barren Realms 007

Shark said:


> Some of the copper was from clean pipe used just for testing the furnace and burners. Some of it was from legs and wire from incinerated IC chips after running a magnet over them and removing the magnetics.



Ok, so there is a chance that you have PM's in this then.


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## Shark

Some improvement. On my third try with mixed copper and mixed magnetic parts from incinerated IC's. (I only used the internal parts of the IC's with the bars from my previous picture). I still learned a lot from this test batch and I am pleased with the results, for now.

This picture, if I am right, shows what I think is termed as a "mat". The crusty looking parts of iron that layered between the borax and the copper layer.




The bottom. The two beads came from my second attempt. Not quite successful but better than my first.


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## Barren Realms 007

Hey your getting there and making headway. Cool job. Just be patient and don't try to rush things. :mrgreen:


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## 4metals

Are you doing these melts with a flux only or are you oxygen sparging as well?


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## Shark

The corn ear shapes were with borax only, and mainly copper based. This last one was using borax, sodium carbonate and a small pinch of silica sand. I haven't the tools for sparging yet, but would like to try it.


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## 4metals

Then hold off on the iron in the melt for a while until you can get it out with O2 Just do magnetic separations and store it until you are equipped to get more of it out of the melt pyrometallurgically.


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## Shark

4metals said:


> Then hold off on the iron in the melt for a while until you can get it out with O2 Just do magnetic separations and store it until you are equipped to get more of it out of the melt pyrometallurgically.



Thanks for the reply. Your suggestion confirms what I saw while working with this material. The headaches multiply once the non copper parts were added. I have been looking into sparging tubes and most seem quite large for my small furnace. Is there a method for choosing a tube size for a given crucible size? Does the tube need to be submerged into the molten metal or will playing the air across the surface be sufficient?


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## 4metals

Quartz glass tubes come in much smaller diameters for use in a small crucible and flux is actually surface active but sparging needs to bubble through molten metal to contact the oxidizable metal, which on the surface will have a run in with some flux to hold it in the salt form.


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## VanMarco

Hello guys

I find this thread very interesting, im not yet thru with all of it, I have a question for you,
Basically I have a relatively large amounts of PCBs which have gold plating, and some components left on
(no ceramic capacitors or ICs), for now, I dont intend to process them to the final recovery for space and time
reasons, but if I wanted to reduce the bulk of the volume they occupy, may I incinerate them and keep only the ashes bearing PMs and other metals?

Also when you refer to incineration I am not quite clear, I know its a bit of self explanatory, but.
I do use a gasification set-up to recover metals from sources where there is resin, plastics etc, but from my setup
I get metals + carbon (char). How do I turn this carbon into ash?

Thanks a lot


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## 4metals

Carbon char can be burned in open air with little to no smoke until all that remains is ash.


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## butcher

Carbon is the result of incomplete combustion, adding oxygen (air) and heat will finish combustion of carbonaceous materials to carbon dioxide gas leaving you with the white ash.

In pyrolysis, we decompose the carbonous materials to carbon with heat by limiting the oxygen or air to ensure incomplete combustion. 

How they used to make charcoal is by cutting cords of firewood and stacking it, and burying it under a mound of dirt, they would have a hole to get the fire started and after the wood began burning they would cover the whole to starve the fire of air or oxygen, the result was incomplete combustion of the wood to charcoal. if the wood was left in the open air to burn the wood would completely combust to ash.

Electronic materials, (and many ores), can produce a wide array of very toxic gases most of which will not only poison us but also can poison our environment or the are when these gases are in large enough quantity, in pyrolysis re-burning of these dangerous gases, can assist in adding heat to fuel the operation and ensure we are putting less of these deadly gases into the air around us or into our surroundings. Re-burners or re-burning of these gases is required along with scrubbers to scrub the fumes of contaminants,in the industrial setting.


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## Shark

Here is how I made the big bar in the last pictures above. While there are things that I changed later (like my shoes) the basics are the same. I thought I had posted this before, but that is what I get for thinking sometimes.

This is mainly a mixture of copper pipe and non magnetic parts of IC.s At the last minute I added two tablespoons of magnetic parts with a very aggressive flux. (another mistake I wasn't prepared for)

[youtube]http://www.youtube.com/watch?v=w-jfd1Wz4S8[/youtube]


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## Shark

The current working furnace in action. I really like the way this one works with the newest burner, heats well, and fast, and can get way hotter than I ever expected in such a small furnace. The new burner is built on 8x1/2 inch iron pipe with a 1/2x 1 1/4 inch reducer. 1/4 inch copper tubing with a 3/64 hole for the gas to exit from. This combination allowed me to do away with the extra air from the compressor as well. 

[youtube]http://www.youtube.com/watch?v=3KUbKLnq7O4[/youtube]

And a few of the results that still need to be refined yet.


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## kjavanb123

kurtak said:


> One point I see you did not make mention of (when dealing with whole CBs) is that they need to be shredded "before" going to pyrolysis/incineration --- ...
> 
> Kurt



I did a test today on my pyrolized depopulated CBs. I took a sample and cut it to smaller pieces and put them in a mixer that no longer is used for food mixing.

Here is a sample pyrolized CB. Cut into smaller pieces.



Here is the mixer.



Here is the result.



I was trying to pulverize the pyrolized CBs to concentrate the metallics from the ash in my homemade blue bowl, but because the fibers turn into fluffy stuff in the mix, it was not working in blue bowl.

Based on this experiment, in regards tk kurtak statement about shredding boards prior to pyrolize, I think it would be much better to shred boards after pyrolysis/incineration, it would be a lot easier on shredder and it increase the speed of throughput.

Thanks
Kj


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## Palladium

I miss Frank!


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## kjavanb123

Lou said:


> The nickel will stay with the copper.



What about Tantalum? Does it oxidize and report to slag or stays with copper?


Thanks 
Kj


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## Lou

Tantalum is very easily oxidized.

Usually it accompanies any base soluble materials in basic slags as a tantalate. 


Lou


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## Shark

Palladium said:


> I miss Frank!



I know the feeling to well.


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## rickzeien

"Poor sorting results in smelting lower grades of copper with metals like lead which are a nuisance metal in the copper refining process and they are a reason copper smelters will charge you extra when these metals are in the mix. 

So assuming we all have the sorting process down pat, we end up with boards and components which we need to burn."

Is there a thread that outlines best practices for sorting PCB to prep for copper smelting and other recovery processes?

Thanks

Sent from my LG-H872 using Tapatalk


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## snoman701

rickzeien said:


> Is there a thread that outlines best practices for sorting PCB to prep for copper smelting and other recovery processes?



There's lots of them. But you have to read the forum pretty deeply.

Lead is the least of your concerns if you think burning boards / smelting is a process you can take on easily.


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## rickzeien

snoman701 said:


> rickzeien said:
> 
> 
> 
> Is there a thread that outlines best practices for sorting PCB to prep for copper smelting and other recovery processes?
> 
> 
> 
> 
> There's lots of them. But you have to read the forum pretty deeply.
> 
> Lead is the least of your concerns if you think burning boards / smelting is a process you can take on easily.
Click to expand...

Thank you. Yes smelting is what I am plan to do. 

Sent from my LG-H872 using Tapatalk


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## snoman701

Put a physical board in front of you. 

Remove all of the parts off the board. 

Now you've got a board and all the parts. 

Sort them into like piles. 

Weigh them all individually.

Using numbers you find on the forum, determine the individual values of each part in copper and precious metal content. 

Now, it's going to cost you AT LEAST 1 dollar a pound to realize the value within each pile. So if that pile is worth LESS than 1 dollar a pound, you don't want anything to do with processing it and need to find a buyer as is. 

Following that, it's a matter of adjusting the x, in "x" dollar a pound so that you are getting paid appropriately for your labor.


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## ashir

depopulating boards and processing only IC's and mlcc's mix via smelting. what will be suitable process, 
getring slime and process via nitric, 
use silver as collecter and run in silver cell
use copper as collecter and run a copper cell?


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## gaurav_347

Hello,

Hey guys I need you help on another smelting matter. I have a few questions that I need answers to. I have read various threads regarding this topic but I am a little confused. 

So we have been recovering gold from Ic and chips with lead being a collector metal followed by cupellation. Over the past few years in this business we recovered quite a large amount of silver chloride. We were planning to smelt this and sell it. But I had a few questions before taking this step. We want to make some changes in our smelting operations. The questions are as follows. 

1.Can this silver chloride be used as a collector metal as it is?

2. How much Agcl has to be added to the smelt for say one kg of Ic/chip Ash? 

3.Will it be necessary to remove the magnetics/kovar from the Ash before smelting it?( we never do with our process) 

4.Can the same silver dore be used in the next smelt to collect more precious metals//Can we re run the previous recovered dore in our next smelt? 

(We are using pure lead ingots during our smelt along with soda ash, borax, fluorspar, lead oxide, sodium nitrate and a little flour. If we start using silver chloride will the flux recipe change apart from not using lead and lead oxide? We usually run the same lead Dore thrice to collect more precious metals during the next smelt.) 

5. What will happen to the base metals during the smelt? 

We want to stop using lead completely and shift to a safer option. Plus we can eliminate one step by using silver which is cupellation . We were also thinking about using copper but the acid waste will be huge. Since we already have some silver chloride with us why not bring it some use instead of selling it. 

I would really appreciate It you guys can help me out. 
Thanks and Regards, 
Gaurav


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## gaurav_347

I have one more question how will tin/solder play a role in the above steps. Will it get oxidized into the slags or will be a part of silver dore. If so then won't it create problems during nitric leaching?


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## butcher

I believe the use of silver chloride would prove to be a problem, silver chloride is hard to convert to silver in a melt, needing a strong reducing flux high in sodium carbonate.

It would be easier if you at least converted the silver chloride to silver oxide ...

Gold and silver are volatile as chlorides.


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## gaurav_347

butcher said:


> I believe the use of silver chloride would prove to be a problem, silver chloride is hard to convert to silver in a melt, needing a strong reducing flux high in sodium carbonate.
> 
> It would be easier if you at least converted the silver chloride to silver oxide ...
> 
> Gold and silver are volatile as chlorides.



Thank you butcher. I will get the silver chloride converted into silver oxide first then try this out.


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## ION 47

Tell me, will an induction furnace with a graphite crucible melt a mixture of Ag2S and soda ash? I have the option to buy an "Indutherm MU 900" furnace, I want to melt the sulfurous silver to recover to pure Ag, but will it be possible in an induction furnace?


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## modtheworld44

ION 47


Yes it will work,but because it is silver sulphide you will need to put iron in the melt with the sodium carbonate.I speak from experience and not an educated guess.Thanks in advance.



modtheworld44


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## Behnam2070

If I pour gasoline on a board in a dish and match it, do they themselves turn to ashes or do I have to heat from below?


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## FrugalRefiner

Do NOT do that! You will create a lot of toxic gasses that can poison you and anyone down wind from you.

Dave


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## ION 47

modtheworld44 said:


> ION 47
> 
> 
> Yes it will work,but because it is silver sulphide you will need to put iron in the melt with the sodium carbonate.I speak from experience and not an educated guess.Thanks in advance.
> 
> 
> 
> modtheworld44



Thanks for the answer! My doubt was that silver sulfide has an amorphous fraction, which would be a difficulty for Foucault currents to occur. I will try on Your recommendations.


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