Pyrolysis

[haveagojoe]

Many videos on YouTube show IC chips being burned to ash on an open fire, which releases harmful dioxins. It appears that many e-scrappers interpret the terms "pyrolysis" and "incineration" interchangably when they are not at at all the same thing.

I have only been able to find one short video on YouTube showing chips apparently being pyrolized in a safe and effective way: here. The video shows fumes being condensed to oil which I don't think is entirely necessary, but the use of an afterburner as shown is essential.

I thought it would be good to make this opportunity to revisit the discussion on the proper method of pyrolysis prior to incineration.

Any comments welcomed, especially with photos of pyrolysis rigs. In particular I would be interested to hear thoughts on the widely held notion that pyrolysis can lead to losses as gold is trapped by carbon. I think this is probably a myth, used as justification for the highly dangerous method of wet-ashing, and I think in fact greater losses would occur if pyrolysis was not performed prior to incineration, due to chlorine present in the plastic. In any case, if incineration is completed after pyrolysis, there should be no carbon remaining to trap gold anyway.

 

[Yggdrasil]

Many videos on YouTube show IC chips being burned to ash on an open fire, which releases harmful dioxins. It appears that many e-scrappers interpret the terms "pyrolization" and "incineration" interchangably when they are not at at all the same thing.

I have only been able to find one short video on YouTube showing chips apparently being pyrolized in a safe and effective way: here. The video shows fumes being condensed to oil which I don't think is entirely necessary, but the use of an afterburner as shown is essential.

I thought it would be good to make this opportunity to revisit the discussion on the proper method of pyrolization prior to incineration.

Any comments welcomed, especially with photos of pyrolization rigs. In particular I would be interested to hear thoughts on the widely held notion that pyrolization can lead to losses as gold is trapped by carbon. I think this is probably a myth, used as justification for the highly dangerous method of wet-ashing, and I think in fact greater losses would occur if pyrolization was not performed prior to incineration, due to chlorine present in the plastic. In any case, if incineration is completed after pyrolization, there should be no carbon remaining to trap gold anyway.

In here we recommend Pyrolizing followed by Incineration(Ashing).
What you and everyone of us need to understand,
is that the majority of the video's out there are made for one purpose, money (Clicks and views).

You do not need to condense the gases, the easiest is to have a pipe leading deep enough into the fire so it will be burned with sufficient retention time.
One positive thing with this, is that it will reduce the amount of fuel used to pyrolize them.

Besides that there are many ways to make proper pyrolizing vessels.

 

[haveagojoe]

the majority of the video's out there are made for one purpose, money (Clicks and views).

Yes indeed; my intention with this thread is to address the spread of harmful practices by renewing discussion of the topic of proper pyrolysis since it is almost completely absent on Youtube, where increasing numbers begin their journey. I would hope that a video showing and explaining the correct approach would receive the views it would deserve, it's a pity that the only one I found is so short.

 

[4metals]

Pyrolysis as a concept has been around for a very long time. Think of it as the process used to make charcoal, burn off the volatile fraction of the material and limit the oxygen so the fire dies out. The result is charcoal. If you have ever seen charcoal made by the classical covered burn pile method you will notice it can be quite smoky.

But the scraps we are talking about burning contain a lot more nasty compounds than an oak tree has. For effective pyrolysis we need a vessel to seal the material in with a vent to direct the volatiles. Years ago, before pyrolysis came to be viewed as the preferred method to completely combust the volatiles, a normal incinerator was used and the treatment for the smoke was an afterburner. There was typically a choke point or a donut in the afterburner air path where the smoke was re-burned and a retention time of 1 to 2 seconds in the afterburner at high enough temperatures was effective. When I started burning e-scrap I quickly realized that filling a tray that held a 55 gallon drum of boards and incinerating it just didn't cut it. So we controlled the process by slowing the feed so the afterburner wasn't overwhelmed by smoke. I did not do enough e-scrap back in the day to need any form of pyrolysis so I used the slow feed hot afterburner approach. The thing that convinced me to use controlled pyrolysis were carpets from jewelers shops. My God can they generate smoke.

My approach was use the incinerator I already had and help it better burn the volatiles efficiently. I did this with a 55 gallon drum. It had a removable lid and a 2" threaded bung. I welded on 2 rails so the drum sat above the floor of the incinerator and loaded the drum with carpet. The lid was clamped on and the bung connected to a pipe that went under the drum between the rails and had holes drilled along the length to allow the gasses to escape. The pipe was located on the high side of the drum so the pressure forced the gas down and through the pipe and under the drum.

The burner of the incinerator shot a flame under the drum from the back of the incinerator. The key to burning the smoke is sufficient oxygen. I was able to adjust the burner on the incinerator enough to supply enough air for the flame and enough extra for the burning of the "fuel" the pyrolysis provided. I soon realized that when the incinerator was about 700º to 750ºF the burner shut down and pretty quickly the free fuel stopped burning and smoked its way up to the afterburner, overwhelming it. I corrected this by controlling the temperature with a thermostat that shut the gas but not the fan. Problem solved.

My incinerator had a peep hole. I could look down to see inside the chamber so all I had to do was keep the incinerator at temperature (700-750ºF) until all of the volatiles were gassed off and burned themselves out. All the while the afterburner was kept at 1500ºF to burn the balance of the smoke that got to the afterburner.

When the drum cooled, typically overnight, we would empty the drum into a tray and burn off the "charcoal" completely to a fine ash. This smoked very little and produced a fine sweep.

With e-scrap, this will produce a powdered fraction and a metallics fraction. The metallics were smelted to make copper based bullion and the powders were crushed and sifted and assayed to ship to a sweeps smelter as low grade sweeps. There was always payable metals in the powder.

As much as I enjoyed consulting and building refineries, I still fondly remember the days getting dirty actually doing the processing too.

 

[4metals]

Upon re-reading this I realized I did not say the drum lies down on its side and the rails are welded on the sides so it sits a few inches above the incinerator floor. I guess if your incinerator is large enough you could stand it on end but the one I made lay on its side.

 

[kurtak]

Many videos on YouTube show IC chips being burned to ash on an open fire, which releases harmful dioxins.

I agree - most youtube back yard hacks have gold fever & simply do not care about their own health let alone the environment around them & that includes but certainly not limited only to their methods of incineration/pyrolysis

Safety & health is the last thing on their minds as they go in pursuit of a "few grams" of gold along with the pursuit of youtube "look at what I can do" clicks - to achieve their "few grams" of gold fever

I thought it would be good to make this opportunity to revisit the discussion on the proper method of pyrolysis prior to incineration.

Pyrolysis/incineration is indeed a VERY TOXIC part of the process & you are correct in pointing out that for the sake of your own health & the health of the environment around you it NEEDS to be done properly - & "open burning" in your back yard is "far from" proper

You can read some of what I have posted about this in these threads ------------

https://goldrefiningforum.com/threads/what-about-beryllium-in-ic-chips.27671/page-2#post-301648

https://goldrefiningforum.com/threa...s-from-carbon-and-organics.28551/#post-301413

https://goldrefiningforum.com/threads/pyrolysis-reactor.22581/#p237092

Kurt