I do not think he is trolling, but as 4metals has pointed out, he is asking all around without following through with feed back on his questions.
Which may not only be confusing to the rest of the forum but himself too.
Edit spelling.
Last edited:
One step pyrometallurgy process for PCB
- Thread starter Ayham Hafez
- Start date
Help Support Gold Refining Forum:
Which may not only be confusing to the rest of the forum but himself too.
Edit spelling.
Ayham, can you please stay on one topic until it has been resolved or at least give feedback on the replies to your questions?
You are bouncing all around in a way that leave us with the impression you do not understand our replies.
manorman
Well-known member
Are the batteries the biggest issue that refiners have with whole boards, it seems I have read that even a few lithium batteries will wreak a large run in the furnace?The BIG BOYS do it ALL the time
They certainly don't spend time "depopulating" CBs
What they do is shred the boards - them incinerate - then smelt
In the smelt some base metals are able to be slagged off with different fluxes that allow them to be oxidized in the smelt - other base metals are able to be slagged off by sparging air through the molten smelt load to oxidize those base metals (& slag them off) --- they also add A LOT of extra copper to the smelt
Concerning the electrolytic capacitors - they are only an explosion concern when they are "whole" capacitors because pressure builds up in them as the electrolyte starts to boil in them from the heat - shedding of the CBs takes care of that problem as the capacitors are shredded/crushed in the shredding process
Kurt
I've watched television programs on PCB recycling, with some knowledge one can fill in the blanks of the narration. I don't know what percentage use one method vs. another, but the emissions from burning PCBs becomes a invitation for special interest groups to show a company or individual attention. If I'm not wrong the preferred and effective method is mechanical grinding and separating metals from other materials before further procedures such as electrolysis, press filtering, ect. I don't think that putting PCBs into one big pot of molten flux soup is cost effective, would even work or provide a respectable yield even with using a collector metal such as bismuth or lead. The required steps to process the doré would be extensive and again not cost effective.
Unfortunately, the engineers who design circuitry, pay little to no attention to how their creations will be processed in their “afterlife”. So no attention is paid to future environmental challenges.
As refiners we are left with 2 options, airborne pollutants or waterborne pollutants.
From my experience a pyrolysis followed by incineration is less polluting than straight incineration because afterburners alone are inefficient. Pyrolysis allows the gaseous volatiles driven off to be more efficiently combusted before the burning of the remaining carbon. Is it perfect, no, but more efficient than straight incineration for sure.
Once the refiner is left with the metallics fraction one option is to chemically refine the metals or to “clean up” the metallic faction by smelting. Smelting involves oxidizing the base metals that are undesirable for electrolytic copper refining and leaves the refiner with a slag which has metals in it as a waste. Fortunately this solid waste often passes the TCLP protocol testing because it is “glass” encased. So this waste is classified non hazardous. (if it passes TCLP testing.)
If the refiner chooses the chemical refining process there is the issue with water borne pollutants to treat.
So bottom line, there are options, all with consequences. It is our job to determine the most cost effective way to process these materials with (in a perfect world) an eye towards minimizing environmental consequences.
I guess we can blame it all on the electrical engineers who design these circuits!
As refiners we are left with 2 options, airborne pollutants or waterborne pollutants.
From my experience a pyrolysis followed by incineration is less polluting than straight incineration because afterburners alone are inefficient. Pyrolysis allows the gaseous volatiles driven off to be more efficiently combusted before the burning of the remaining carbon. Is it perfect, no, but more efficient than straight incineration for sure.
Once the refiner is left with the metallics fraction one option is to chemically refine the metals or to “clean up” the metallic faction by smelting. Smelting involves oxidizing the base metals that are undesirable for electrolytic copper refining and leaves the refiner with a slag which has metals in it as a waste. Fortunately this solid waste often passes the TCLP protocol testing because it is “glass” encased. So this waste is classified non hazardous. (if it passes TCLP testing.)
If the refiner chooses the chemical refining process there is the issue with water borne pollutants to treat.
So bottom line, there are options, all with consequences. It is our job to determine the most cost effective way to process these materials with (in a perfect world) an eye towards minimizing environmental consequences.
I guess we can blame it all on the electrical engineers who design these circuits!
Yeah, I am aware of the multiple stages, I just wanted to simplify it to be understandable. Also aware of some design features, like recuperation of heat from combustion to pre-heat the air which is blown to the bottom etc.
This is the process which I could not imagine doing somewhere in the backyard or anywhere near people in DIY setup...
I have done some experiments with two step sequential process, just with several kilos of PCBs... And I stumbled across so many issues with it, that I straightly abandoned that idea long ago. In order to be profitable, scale of the operation will need to be huge, and I simply do not have resources and premises which will allow such venture.
My refining partner always wanted to build such system, semi-industrial scale, working with few hundred kg´s of PCBs a day. As engineer in the field, he calculated all the theoretical parameters, size of rotary pyrolysis/incineration furnance, approximate neccessary power and natgas input to onset the burning, air blowers and feeds, gas heat exchanger to pre-heat air from incineration heat to aid smelting, fluxing parameters, he had done several experiments regarding fluxing of the incinerated PCBs, designed the shaft furnance, lining, dimensions, emergency afterburner, scrubber... Experiments with oxidative cleaning of the melted mixed metal alloy, scorifying, electrolysis tub, electrode shapes, casting molds, rectifiers... Everything.
It was his dream, so I learned a lot from him regarding this toppic. Such a shame he will never pursue his dreams...
Darkthirty
Well-known member
- Joined
- Dec 21, 2016
- Messages
- 289
Polychlorinated Biphenyls?
Because of the Carbon
PCB Printed Circuit Board
PCBs Printed Circuit Boards
I should of not have been lazy and typed it out, at the time I wasn't thinking i was giving the chemical formula for Polychlorinated Biphenyls. Thank you for questioning and pointing it out.
Martijn
Well-known member
Pakistan Cricket Board?
Parti Communiste de Belgique?
Ayham Hafez
Well-known member
Any thoughts about my experience in acid batteries smelting using rotary furnace with adoption it in PCBs recycling?
The air pollution control unit will handle the gases carrying small valuable components, and regard carbon it will not be mixed in the molten metals since carbon always float above the molten metals and it uses as flux to seperate base metals such as iron.
The air pollution control unit will handle the gases carrying small valuable components, and regard carbon it will not be mixed in the molten metals since carbon always float above the molten metals and it uses as flux to seperate base metals such as iron.
Typically, from my hands on experience with rotary furnaces, effective fume scrubbing was a challenge. I was using the furnace on previously incinerated jewelers sweeps which had given up it’s volatiles on incineration. The rotary furnace was strictly to facilitate using copper as a collector metal to produce copper based bullion.
In the late ‘80’s e-waste was starting to become a common feed and, having the rotary furnace seemed like a good fit. That’s when I learned just how much circuit boards smoke when burnt. And at the same time I learned just how difficult it is to scrub the fume the open end of the rotary emitted. In the end it did burn but it generated a substantial quantity of ash mixed with flux containing base metals and a lot of values hung up in the dense slag.
If we had processed the boards in an incinerator, which we had as well, they still would have overwhelmed the afterburner but we would have had the benefit of unloading it and crushing and sifting the ash to generate 2 feeds one of processed powders (homogeneous and sample able) and one of all of the metallics.
At that point passing it through a rotary would have been an environmental nightmare as all of the lead would volatilize and pass off into the atmosphere. Smelting with a flux layer would have oxidized a lot of the undesirable metals and been placed directly into the copper cells.
Fortunately, for my lungs and the local bird population, we had more than enough prepared jewelers sweep to smelt that we didn’t venture into the up and coming e-waste scene.
Electrolytic canister capacitors do indeed go boom when incinerated. I actually melt them in a cast iron pipe in my incinerator furnace because the aluminum is exceedingly pure. Lots of popping and fire!
In the PCBs pyrometallurgical process, TBRC furnace (Top Blown Rotary Converter) are used, also known as Kaldo furnace. It is a rotary oven with a single mouth that works inclined between 20° and 30° and its burner is a water cooled stainless steel lance, it is introduced into the furnace and strikes with its flame almost on the surface of the molten bath, they are very versatile and efficient, they reach temperatures of 1500°C because they can operate with natural gas and pure oxygen and the variable speed rotation allows the temperature homogeneity due to stirring of the molten charge. The Boliden company uses them to melt and refine, in a single step, about 150,000 tons/year of previously classified and crushed uncalcined PCBs and uses the heat energy from the oxidation of plastics and base metals for the fusion of the charge and the residual carbon, while burning, as a reducing agent. They are also used to treat anodic sludge in a single step ending in copper anodes with precious metals. These furnaces require a significant gas treatment system. I leave you a video of an experimental prototype in operation.
Attachments
Instead of "copper anodes" it should say silver anode or silver doré capable of being electrolyzed or hydrometallurgically treated.
kurtak
Well-known member
They are two completely different things
With the batteries you only have two things to deal with (1) burning off the plastic (2) recovery of the molten lead
With PCBs you have MANY things to deal with (as somewhat explained by 4metals - as well as by me)
The plastics have already been discussed & if they were the only concern would not be that big of a deal - but --------
Besides the PMs (silver gold & palladium) you have multiple base metals to deal with (copper, iron, aluminum, tin etc. etc.) most if not all of those - except the copper - you want/need to eliminate in the smelt (oxidize so they slag off - or remove before going to the smelt)
You also have things like ceramics, silica & silicon etc. that need to be slagged off (& for what it is worth - the silicon will alloy with your copper/PM dore - if not properly slagged off)
So simply put - smelting PCBs - is not as simple as smelting something like lead acid batteries because you have MANY more elements to deal with then just the plastic & lead found in lead acid batteries
Or as I said earlier - trying to smelt PCBs - in a one step process - will result in A BIG MESS !!!
Kurt
Excellent video about a beautiful piece of equipment. My one question. All of that burn time (4 hours) and flux, and at the end they had maybe 20 pounds of lead! Lead, as in $2 a pound lead! Expect to see that furnace on ebay if that is the best he has to process. His ROI melting lead is likely 2 lifetimes if ever.
I also thought the same thing, it is a small experimental pilot furnace, the interesting thing about the video is that you can see it working and you can see its structure, the lance burner whose entry depth to the oven is adjustable, the hoses that supply gas, oxygen, and inlet and outlet of the cooling water and the gas extraction hood.
The unit I had used air for the O2 source and the flame entered from the rear. The feed was from the rear as well. It was a real workhorse.
But like I said I would never use it for anything that wasn't pyrolyzed first.Cutler stopped making these things a long while ago. I called them a few years back and they said they would sell the engineering if anyone wanted it.
But like I said I would never use it for anything that wasn't pyrolyzed first.Cutler stopped making these things a long while ago. I called them a few years back and they said they would sell the engineering if anyone wanted it.
