# Smelting for Cu - Where is the gold going?



## snoman701 (May 18, 2017)

It has been said by many that when you send a load to one of the small processors, that you aren't actually getting a realistic payment of what your boards actually had in them. That they cheat you out of whatever they can. 

So, short of it being straight up fraud, because there was no umpire and they just cooked it in their favor...how do "they" steal the gold?

In another thread, Butcher describes how salt can cause gold to become more volatile at high temperatures by oxidizing it. 

Along the way, from pyrolyzation to incineration to crushing etc....where are the "danger points"? Is it during the actual pyrolyzation / incineration?


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## snoman701 (May 18, 2017)

Then in another thread for incinerator design, Lou plainly states 450C for pyrolysis and not greater than 650C for controlled oxidation of carbon. 

Just wondering from a chemistry perspective, what is happening that pushes gold into the baghouse, or in some other cavern that the "refiner" could hide.


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## justinhcase (May 19, 2017)

From my research it seems to be one of quantity.
If the material is far too divers to value accurately by eye..
The best method is to granulate and homogenise ,take samples, smelt and take samples .all very time consuming and labour intensive.
Not a service you can expect unless you are putting out a five ton lot of high grade sorted boards every month.
There is a marked difference when it come's to small lot's, how can you expect expensive method's of valuation when the cost would be more than the value of the lot most of the time?
If I showed you a savings account that was tax free and paid out 100% interest over five years would you not plough every penny you could afford to save into it? 
The issue is one of space, if you have a safe dry space that has a low cost what harm is there is saving up kit until you have a lot suitable for monitored processing. Shipping containers are very good ,no need to unpack just fill up and ship off.
If you need money to day and have no room for a few tons' of material in long-term storage then you have to make do with what you are offered.


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## 4metals (May 19, 2017)

> Just wondering from a chemistry perspective, what is happening that pushes gold into the baghouse, or in some other cavern that the "refiner" could hide.



The biggest culprit for incinerated materials is aggressive raking during the burn process accompanied by a high velocity exhaust into the baghouse. It would be interesting to be a fly on the wall when the baghouse assays are done.

In all fairness to refiners, almost every inch of an active refinery accumulates valuable dust or sludges. All the way down to the metal hydroxides recovered in the waste treatment process. All of the slags as well. Refining is not a clean room process, so it is really not possible to avoid some losses to individual lots. But that doesn't translate into losses for the refinery. All of this stuff is collected, processed into a sample-able form and shipped as a low grade material to a smelter.


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## snoman701 (May 19, 2017)

Ok...so this is done quickly then. Ceramics guy...when I burn things I let it soak at temperature. No raking required...the heat will get it in time.

After ball milling...what remains that will be greater than 10 mesh? Any metallics? 


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## 4metals (May 19, 2017)

> After ball milling...what remains that will be greater than 10 mesh? Any metallics?



That all depends on what went into the burn. Years ago when I incinerated PC boards, the majority of the value was in the oversize, most of the copper fraction. And as far as the heat reaching everything by letting it soak at temperature, that takes time, time is money, you know how that goes.


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## Topher_osAUrus (May 20, 2017)

I know the basis of this thread was more along the lines of escrap, and its reduction from circuit board, to small pieces of metallics and ash, then smelting. But, the title of the thread made me think of a portion of TK Rose's "The Metallurgy of Gold". In it, he goes over the volatility of gold, and how being alloyed with base metals, copper, zinc, etc.. (and tellurium in particular showed most volatility), which will increase the rate of losses of the gold itself.

Other variables that held an effect on the gold, were the type of dish used, as well as the temperature and the atmosphere the melts were done in. (If the gasses were creating "currents" or just ambient) At one operation they melted and poured 30lbs of gold copper alloy, with an inverted beaker above the crucible, they recovered some 4.5 grains of gold. 

Sure, doesn't sound like a lot, but, carelessness can add to that number, as well as many other variables can too. I recall the number that Harold said he recovered from his filtration system biannually (which was remarkable), so, it would be more than interesting to hear what the HUGE refining corporations recover from their bag house or other filtration systems.


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## 4metals (May 20, 2017)

> it would be more than interesting to hear what the HUGE refining corporations recover from their baghouse or other filtration systems.



A well guarded secret, never discussed. Even the assay department may know the assay but not the weight. That information is on a need to know basis and most don't need to know.


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## snoman701 (May 20, 2017)

So given that, my next question, would they routinely change operating parameters so that most efficient burn (lots of initial intense heat, lots of raking) is used to increase throughput....knowing full well that THEY will recover all product, and better yet, that they'll pay less for it.


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## Topher_osAUrus (May 20, 2017)

4metals said:


> A well guarded secret, never discussed. Even the assay department may know the assay but not the weight. That information is on a need to know basis and most don't need to know.


I would imagine so!

Loose lips sink ships. If word got around that a company was getting X amount of gold back after a year of running. A few of their bigger customers who sent in very very large amounts of material, multiple times, may be holding out their hands waiting for renumeration (or, I guess remuneration, since they didn't get paid initially on that portion). While the mystery of "why was the assay off" was finally solved.

The Mint in Sidney, the sweepings from the top coping-stone of the chimeny, 70ft high, contained 1.46% gold and 6.06% silver. ...indeed it boggles the mind to think of the other numbers that could be associated with that assay... How much in the rest of the chimney? How much in the filtration system? How much elsewhere?

We'll never know, but it's interesting to wonder, nonetheless.


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## trdking (May 21, 2019)

A friend of mine who ran a VERY large incineration and processing plant for E scrap told me that he recovers more than a dollar per pound from his dust


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