New process for PCB scap

[Chumbawamba]

I found this snippet in the E-scrap Newsletter I receive via e-mail:

Patent Application No. 20090288956 has been filed by a team of
inventors - led by James Dills - describing a method of recycling
printed circuit boards by pyrolyzing them to an ash and then
separating out metals by their differing densities.

Here's a link to the full patent application:

http://www.freepatentsonline.com/y2009/0288956.html

Maybe someone more knowledgeable in this field can explain the gist of this. Seems like a form of "reverse electroplating"?

 

[goldsilverpro]

I read the entire patent application and I wonder if the inventors have really tried this. It sounds as though it was done theoretically rather than experimentally. I admit that I can be an eternal cynic when it comes to these things.

There are 2 steps: First, pyrolysis and then the selective plating out of the individual metals in order, based on voltage adjustment. I see problems with both of these steps, from a practical viewpoint.

Pyrolysis. This is the removal of organic materials by distillation instead of incineration. The material is heated in a totally sealed chamber and the organics are vaporized and then condensed to collect an oil. The practical problem is that the whole thing must be 100% sealed. Any slight leakage of air will immediately raise the temperature and cause an explosion. If you look in the patent literature, you will find patents for pyrolyzing all sorts of things - tires, the PET plastic from x-ray film, circuit boards, etc. Although pyrolysis sounds wonderfully green, I know of no large scale pyrolytic destruction of any of these things. If this did work, I would think there would be no more tires going to the landfills. Theoretically, you get a drum or two of usable oil and a lot of carbon black from a ton of tires. That should more than pay for the process.

Selective deposition of the various metals at different voltages (It reminds me of trying to precipitate metals from a solution as hydroxides, one by one, in order, by adjusting the pH - in practice, there's always an overlap). In order for this to work, you would have to get a 100% separation - 99% wouldn't work because the metals would have to be re-refined. As a old plater, this doesn't seem plausible. In practice, there is always an overlap of the metals during deposition, no matter how tight you control the voltage - just read any good book on electroplating theory.

If you notice, everything in the patent is very green. It sounds like they invented this thing just to get money from the government. By using pyrolysis, they eliminate incineration. By using this "slurry" anode, they eliminate melting of the metallics. In essence, if the plating separation part would actually work, you would have the exact same thing by incineration and then melting the metals and forming anodes.

 

[Rhodium]

Pyrolysis. This is the removal of organic materials by distillation instead of incineration. The material is heated in a totally sealed chamber and the organics are vaporized and then condensed to collect an oil.

Is that like Thermal depolymerization Chris ? Like the guy you use to know who keep blowing his machine up trying to perfect the process ? :lol:

 

[goldsilverpro]

Is that like Thermal depolymerization Chris ? Like the guy you use to know who keep blowing his machine up trying to perfect the process ?

Yes. The German guy in Portland trying to do tires. Every time I saw him, every inch of him was covered in carbon. All you could see was his eyes. Reminded me of Pigpen in Peanuts. Always having explosions.

 

[Chumbawamba]

Sounds like your German friend needs to speak with someone highly experienced in high-pressure containment chambers. I know such a guy, and there's a shop around the corner from me that does this sort of work as well for national labs.

 

[goldsilverpro]

I think the difficulties and costs of containment are dependent on volume. I'm not talking about a simple to do lab setup. All those things I mentioned - tires, film, boards - would require a huge operation in order to make a dent in the supply and turn a profit. I think the German guy's pilot setup was for 5 or 10 tons of tires at a time.

 

[NoIdea]

Morning all, One of the main reasons pyrolysis has not taken off is due to it's past. Early seventies lead to a boom in pyrolysis technologies, with all the major petroleum companies owning the patients, or owning the companies that owned the patients. The few plants that did make it into full production were made way way too big and thus ran out of supply to make the system economical. They failed and that has made people weary and scared.

In an effeceint system, it only takes 10% of the energy available in the feedstock to keep the process going, so one could use either the gas or liquid products produced to keep the system self sufficient.

Deano

 

[alexxx]

I'm happy to read that recovering oil from pyrolyzed pcbs is possible (I kept dreaming about that) while thinking about these shredded tires they make diesel from..
This procedure will be for sure most common soon enough. Imagine replacing toxic fumes and gases from combustion by an actual commodity that you can sell for a fair price.

Aren't the chinese or the indians selling such pyrolysis reactors for cheap ? I remember seeing a few over the internet...

edit...

After pyrolysis of the material, could one just melt everything into anodes the "classic way" ?
I am seeing the pyrolysis step just a way to recover more valuable materials (oil).

 

[Marcel]

I doubt that this kind of equipment will ever be available for small scale recycling. The toxic stuff that will develop and needs to be disposed is a nightmare in my view.

 

[Geo]

Marcel, during the operation, most of the toxins are consumed.

 

[skippy]

I think if you try to recover the liquid pyrolysis products they would be quite toxic. You are producing and distilling something much more complicated than oil. The combustion, afterburner and scrubber is what renders the vast majority of the pyrolysis products harmless.

 

[bswartzwelder]

From what I'm reading, this isn't really a new process at all, but a combination of old technologies. Now that I think about it, I guess separating the metals by differing voltage levels might be considered new, but seems to be a long way from having been perfected. I wonder if they could use something like cyanide leaching to remove the gold and then other processes for the other metals? At any rate, it sound like it may not be econimically/environmentally feasible. I would think they could take all the metals from a "batch" and melt them into an ingot (or who knows, cornflakes) and then find a way to selectively remove metals by groups. Maybe PGM's. I would suspect there is more copper in there than anything else. Once you get rid of the copper, what's the next most abundant metal, or what's the next easiest metal to remove completely? Sounds like a nightmare, but interesting reading about it. I doubt anyone on the forum will ever use that process to any extent.

 

[Traveller11]

Is that like Thermal depolymerization Chris ? Like the guy you use to know who keep blowing his machine up trying to perfect the process ?

Yes. The German guy in Portland trying to do tires. Every time I saw him, every inch of him was covered in carbon. All you could see was his eyes. Reminded me of Pigpen in Peanuts. Always having explosions.

LOL You should warn us before you post something like this. I laughed so hard, I sprayed a mouthful of coffee all over my computer screen.

For some reason, it made me think of that Thomas Edison quote: "I have not failed. I've just found 10,000 ways that won't work."

I wonder how often Edison was also covered in carbon and looked like Wile E. Coyote after one of his Acme contraptions went awry. :lol:

 

[bswartzwelder]

You guys are too much!

 

[rickbb]

Too bad you don't have to prove that your method works to get a patent on it. 90% of patents filed are people on a fishing expidition hoping to cash in when someone else eventually does get the thing working. (If ever.)

 

[NoIdea]

Howdy Do-dy All, ah my favorite topic 8) .

I, many years ago made a electric pyrolysis unit, the gas I pumped into old car inner tubes and the liquid was condensed and later fractionally distilled, the liquid distillate, BP in the same range (I forget) as car petrol, was mixed with 20% mentholated sprites and used to run my lawn mower with great results.

It is, as mentioned, very important to keep a positive pressure within the unit; large systems are more susceptible to mishaps than smaller ones.

One of the main reasons I now feed all gas/liquid products straight into a burner is to prevent air entering the system, I have yet to have any explosions or anything close to it, and I am not covered in soot either :mrgreen:

It’s one thing reading about it, an entirely different thing doing it.

Cheers

Deano

 

[bswartzwelder]

Hi Deano,

I have always enjoyed your posts. They have been informative and yet, you kept the subject interesting. I am in the process of building a small (very small) pyrolyzer/incinerator unit. It will be two pieces with the pyrolyzer chamber sitting 1.25 inches above the combustion chamber. Without going into all the details, most of it will be made from 1/4 inch plate steel with all corners welded. The size will be approximately 10.625 inches square and the inside of the combustion chamber will be lined with firebricks. There will be 2 parallel pipes run across the bottom and through the wall at the lower end of the combustioin chamber. They will have a series of holes to allow/force air into the combustion chamber. I will use a blow dryer for my supply of extra air for the combustion chamber. The entire top of the combustion chamber will be open to the atmosphere so all the hot gasses from the burning charcoal can exit with little obstruction. There should be no way for pressure to build up inside the combustion chamber. There will also be a hole in the combustion chamber with a pipe running through it to accept gasses from the upper unit. On the outside, the gas piping will be terminated in an open socket. (More on this later.) The toxic gasses will then be introduced to the burning charcoal and hopefully the toxic gasses will be rendered harmless.

Approximanetly 1.25 inches above the combustion chamber will be the pyrolysis chamber. It will also be a square steel box (all 1/4 inch welded steel) with a lid which will be held on by approximately 8 or 12 bolts with nuts. I plan to drill a hole in the center of the lid and weld a black iron elbow to it. From there, I will run the pipe over to the edge of the unit and down the side. The open end of the pipe will fit snugly into the socket which feeds into the combustion chamber.

You said it is very important to keep a positive pressure within the unit. I am confused a little by this. Where in your design, do you need to keep a positive pressure? If the combustion chamber is under pressure, it could explode. A buildup of pressure in the pyrolysis chamber would not allow the gasses to off vent back into the combustion chamber. If pressure builds up in the pyrolysis unit, wouldn't it also be susceptible to explosion?

Another question is the placement of the pipe being used to introduce the toxic gasses into the combustion chamber. I assume it should be low to allow the gasses time to rise up through the burning embers. The entire combustion chamber will be about 12 inches high. Should the gasses come in at floor level, up 6 inches, or higher? You're the guru. Any comments will be greatly appreciated as I'm still in the design phase and almost ready to order steel plate. Safety is my number one priority and if it isn't going to be safe, I'll abandon the idea completely. THANKS DEANO

 

[Geo]

bswartzwelder, by forcing air through charcoal, you can easily melt steel of that thickness.in a true pyrolysis chamber, the air supply isnt forced.

 

[bswartzwelder]

Thank you, Geo. When I said "forcing" air into the combustion chamber, I meant that it would be under extermely low pressure. That's why I wanted to build something to allow me to slow the blow dryer fan way down. I realize I don't need enough additional oxygen to melt steel, just enough to boost the temperature of the charcoal a tiny little bit. I have sleep apnea and use a CPAP machine to aid my breathing at night. The pressure is measured in centimeters of water column. At 10 centimeters of water column, this pressure would be completely excessive. Also, I don't want the temperature high enough to vaporize the gold in the upper chamber and then send it to the flames below. Sorry for the confusion. If by some chance I could use this unit without any additional air, that would be totally acceptable too me as well. Thank you.

 

[Traveller11]

Thank you, Geo. When I said "forcing" air into the combustion chamber, I meant that it would be under extermely low pressure. That's why I wanted to build something to allow me to slow the blow dryer fan way down. I realize I don't need enough additional oxygen to melt steel, just enough to boost the temperature of the charcoal a tiny little bit. I have sleep apnea and use a CPAP machine to aid my breathing at night. The pressure is measured in centimeters of water column. At 10 centimeters of water column, this pressure would be completely excessive. Also, I don't want the temperature high enough to vaporize the gold in the upper chamber and then send it to the flames below. Sorry for the confusion. If by some chance I could use this unit without any additional air, that would be totally acceptable too me as well. Thank you.

LOL Forgive me, bswartzwelder, sometimes I just can't help myself. :lol: