Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning 2017-04-21T02:33:06+00:00
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e-Waste Recycling Process & Methods (8 replies)

Marshal Meru
2 years ago
Marshal Meru 2 years ago

I would like to start a new discussion on the treatment of E-waste. The production/consumption of EEEs is ever increasing with the concurrent decrease in their lifespan. How do you see the current status and future of treatment/recovery/recycling of E-waste?

John Koenig
2 years ago
John Koenig 2 years ago

While e-waste processing for seems a great way to proceed, there can be a lot of stumbling blocks. First off most e-waste streams are relatively small (but I will admit high value), this precludes large scale processing efforts. Secondly the reaction by local governmental agencies, who often have no experience with similar operations, is usually negative to the most direct processing methods, cyanidation or leaching (even bio-leaching). Lastly handling the residue, which often includes pcb precursors and other potential toxins from the plastics and similar, is an issue.

One alternative I have recommended to a couple of developers (none of which had any mining background) was to use a gravity process to separate out the light plastics, etc and then ship the resulting concentrate to a central facility where it can be handled more efficiently. The response I have gotten is, "Why, when xxx (plug in cyanidation, acid leaching, direct smelting, bio-leaching, ...) is simpler?"

This potential business can be successful, but it has to be looked at as a major business, not as a small corner process.

Bill Rico
2 years ago
Bill Rico 2 years ago

Recycling of E-waste did not develop well in the world. In China, as far as I knew, a large amount of small recycle companies are beginning to set foot into this field, the industry of e-waste recycling just begins to develop, like a chick or baby. There is a long way to be a mature industry. When a certain amount of people and companies realize the advantages and possibility of e-waste recycling, it will develop fast.In my eyes, it is a potential business and will develop prosperously sooner or later.

Victor Bergman
2 years ago
Victor Bergman 2 years ago

I have a particular interest in using dry gravity separation to concentrate E-waste. We have had unexpectedly good results treating this material to provide a concentrated form of the metal components. My experience in China is that E-waste processing is part of the black economy and results in serious pollution of the environment.

Millions of automobiles and trucks will require recycling in the coming years in China and the facilities to do this are inadequate. Even in the UK the copper contained in wiring looms is rarely recovered. Our problem is that while this is a high value material the waste industry is extremely secretive and unwilling to share technology. This results in very slow take up of new technologies and an unwillingness to adopt established technologies from other industries.

In the UK the industry is dominated by the owners of landfill sites who have little interest or knowledge of recycling technology beyond hand sorting.

Marshal Dienes
2 years ago
Marshal Dienes 2 years ago

In China, some of e-waste recycling process are part of the black economy, because they didn't apply friendly-environmental technology. Meanwhile, some companies are applying advanced process to recycle.

Is there any better process than Pyrometallurgy in the recycling of iron?

I cannot agree any more with your opinion about the no one to share technology.

Maya Rothman
2 years ago
Maya Rothman 2 years ago

I visited Ningbo early this Summer to look at vehicle dismantling and waste recycling.

With limited natural resources, recycling is of potentially great potential in the future to guarantee supplies of raw materials for manufacturing.

As ever the equation relates the amount of waste generated per year with the costs of collecting and processing it. The capital and operating costs relative to the scale of the operation become critical. We have concentrated on low cost plant to provide pre-concentration of the metallic fraction prior to chemical or pyro separation.

Sugar Watkins
2 years ago
Sugar Watkins 2 years ago

I came to e-waste recycling 27 years ago when a client wanted to recover gold from edge connectors by cyanide leaching.

Precious metal (PM) recovery from electronics took off in the 1970s when the “scrap” trade realised that electrical connections within IT equipment were coated with PM. In time, the Electrical & Electronic Equipment (EEE) market has grown, whilst advances in production techniques have seen the reduction of PM content of sub-assemblies. In the 90s, EEE was recognised as one of the fastest growing waste streams. Legislation developed to enforce collection & treatment to minimise the environmental impact of End-of-Life (EOL) EEE. Design for EOL has seen the phasing out certain “hazardous” elements & compounds.

In the UK, over 1.5 million tonnes of EEE was sold in 2013. EEE life ranges from less than 1 year for some small consumer goods, 5-7 years for IT equipment, up to 20 years for large domestic appliances. Design evolves; where practical, reduced size, increased functionality. All EEE has electronic logic or circuitry. In 1965, Gordon Moor, Intel, observed that the number of transistors in a Dense Integrated Circuit doubled every 2 years. The trend continues, though, in 2013 the semiconductor industry suggested a doubling only every 3 years! Life-span is related to continued function & users’ expectation of performance. Whilst the reliability of electronic components improves, there is a reluctance to repair faulty EEE due to high “fix” costs compared to new replacement.

At EOL, EEE becomes Waste EEE (WEEE). There are many specialist processors of WEEE. Compared to mining operations, these may appear to be like “cottage industries” & each does have its own peculiar processing route. Waste is a “dog eat dog” industry; processors believe that their particular route may give them a competitive edge. The “value” of WEEE varies from that with a “cost” to recycle in an environmentally sound manner, such as CRT televisions, to “high value” items, such as PC base units. Centralised processing operations may have a unit process cost advantage, but due to the comparative low bulk density of WEEE, excessive transport distances can be detrimental to the positive environmental impact of recycling. There are substantial benefits to, at least, local pre-treatment.

Hazardous substances must be identified & recovered to prevent escape to the environment & contamination of residues. Variability of types & models, means initial processing tends to be manual. Residue tends to be mainly steel & plastic, with some aluminium & copper. Electronic circuitry represents from 1% to 10% of the original weight & may be of little or significant value depending on the use of precious metals in construction. Extremely low value circuitry may only contain 5% copper with traces of silver, whilst a modern day PC motherboard may contain 90 ppm of gold & 20% copper. Upgrading by the removal of steel, plastic & aluminium is logical. Over the years academics & processors have researched & developed cyanide, alkali & acid based leach systems for the residues. Yield considerations & reagent costs have tended to leave the smelting route as the preferred option. Smelting capacity for electronics containing plastics is limited. Smelting charges for electronics tend to be higher than, say, for a mining concentrate. Low grade electronics may not be of high enough intrinsic value to yield a good return at the smelter. A possible solution is to mill & upgrade. This doesn’t come without risk as the gold plate used in modern electronics can be just an “electro-less” or “immersion gold” plate with a thickness of less than 1 micron applied to a substrate of, normally, nickel plate over copper carrier. Milling will lead to the unwanted liberation of sub-micron gold particles which have a tendency to be lost as dust or tailings. This takes us to the grade versus recovery conundrum.

Alan Carter
2 years ago
Alan Carter 2 years ago

As a manufacturer of milling solutions predominately used for precious metals recovery from larger items, catalytic converters etc, we are used to the principle of metal recovery. But in the last year we have though seen an increase in WEEE applications, including a number of clients looking to mill complete PCBs, as Mark points out the control of the sub micron particles is a challenge, I would think looking towards the Pharmaceutical industry and the way they handle equally high value potent powders would be a sensible step though maybe a mindset change if not a high capital investment cost. Once we run some trials shortly I could post back our findings if anyone is interested.

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years ago

As indicated there is not a unique e-waste profile. Smelting facilities that feed waste material only accept "high grade" e-waste that contain high levels of gold >400 g/t e.g. some circuit boards, CPUs etc. Hence different processes should be developed to suitably treat specific types of e-waste with maximum metal recoveries and low precious metal losses. I agree that we have still a long way

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