New process for PCB scap

[bswartzwelder]

Traveller11<

THANKS. I liked that one.

 

[NoIdea]

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

Hi bswartzwelder, positive pressure is maintained by the heat produced from the furnace, I add a wee bit of water into the pyro unit (at start up) produces enough steam to expel any air before pyrolysis commences

Positive pressure will be maintained by pyrolysis itself, it’s only after pyrolysis has completed, no more gasses produced, and that any drop in temperature will cause a negative pressure to result, by introducing a wee bit of water (a millilitre or two) into the unit at this stage will help during cooling

Note: Charcoal (start up) is only required before and after pyrolysis, in between the pyrolysis gasses will be enough to keep the system running, with too much fuel and not enough air will result in incomplete combustion and your nasty gasses will not be burnt

I feed the pyrolysis gasses into the blower tube, about an inch or two from the blower exit so the gasses burn first, this also allows you to gauge how mush extra fuel to add for complete pyrolysis, in addition, the blower acts like a venturi system and helps Sucks the gasses out of the pyrolysis unit

Hope this helps

Deano

 

[bswartzwelder]

Thanks Deano. I have spent the last two days reading and re-reading every post and topic where you have had input and it sounded like you were burning (OOPS pyrolyzing) something. I saw the water addition early on. Great idea.

Very good explanation of the positive pressures and negative pressures. I kinda suspected that was the way things would end up, but wasn't entirely sure.

I didn't personally like the idea of sucking the fumes through the blow dryer and just threw that out as an option. If the blow dryer has brushes, the brushes produce sparks. Those sparks would most likely put a quick end to the blow dryer. Allowing the fumes to go into the manifold which supplies air to the combustion chamber (utilizing the venturi effect) really seems like the way to go. I had no idea (no pun intended) that there would be enough off gasses as to keep the combustion going. Looks like I will need to add charcoal at the start up, run the system on the gasses produced and add charcoal to complete the pyrolyzation process after the gas runs out. Slight design changes at this point.

 

[kurt]

Hi All - good thread being as how I to am working on a "incinerator" system

I say "incinerate" because don't you need to get complete incineration to burn up the carbon (produce white ash) especially if you are going to leach the metals from the ash - which requires a hot oxidizing fire to burn up the carbon

when you pyrolyze you don't burn up all the carbon (due to lack of oxygen in the burn chamber) & wont carbon act as a sponge absorbing your chemical metal compounds in the leaching process there by hindering full value recovery (actived carbon can be used to recover values from low PPM solutions)

Also (& I am not sure about this) but I believe carbon will also interfere with full recovery even in a smelting process - although that could be dealt with (at least to some degree with the right flux mix - like potassium nitrate in the flux mix)

When you pyrolyze you drive off the gases (& oils in the case of plastic) with with heat in an oxygen free atmospher with a byproduct of carbon - carbon is a problem to getting full recovery in the following processing - so wouldn't you still need to "incinerate" after pyrolyzing?

Kurt

 

[bswartzwelder]

Kurt,

Right you are. If you only incinerate, you will eventually get the gray/white ash you are looking for. However, you will produce copious amounts of toxic gasses in the process. I wasn't aware of the amounts produced until I started reading some of Deano's (NoIdea) posts. In actual fact the amount of toxic gasses produced are high enough to sustain the pyrolyzing process almost to the end where additional fuel will be needed. 1. Why pollute the air around you when it can be cleaned fairly easily? and 2. Why not use the toxic gasses to your benefit by saving on the fuel to pyrolyze?

Once pyrolyzed, you still have to incinerate the left over remnants. That will give you the gray/white ash your looking for. As has been pointed out to me, it's the responsible thing to do.