His this is Jason Gaber with Mt. Baker Mining and Metals, and we have a customer coming
up here shortly to run some circuit boards through our recycling system. And I wanted
to walk you through system first and show you how it all works.
So the first part of the system is our 24 by 16 inch hammer mill up there. The lid is
sitting there on the ground so we can take a look at the inside. And that’s going to
be, essentially, a pre-shredder. We have a half inch by three and a half inch screen
in there we’ll take a look at in a minute. It’s going to come out on the discharge
conveyor here, come up under the magnetic cross belt, to pull out all the steel and
the magnetics. Then off the end of the conveyor, this is a zig zag machine, it’s an air separator
that we use for some other recycling. But for the boards I don’t want to turn it on
and suck up any of the fine particles up, I want to get all of those down on the shaker
table so we’re not losing any precious metals.
Here’s a look at the inside of the hammer mill. You can see the screen down below, they’re
half inch by three and a half inch slots, so the boards have to grind up small enough
to get through those slots.
Here’s the rotor assembly, and the hammers are just on pins there. And for our ore-grinding
hammer mills, we have hammers on every slot all the way across, but for boards we learned
you don’t need that many hammers especially if it only has to go through that half-inch
slot there instead of a real fine screen.
Once the material has been shredded, we’re going to feed it into our smaller 16 inch
by 12 inch hammer mill. This hammer mill has a quarter inch punch plate screen in it, and
the reason we do that is we’ve found that a lot of the metals, copper and aluminum especially,
they’re large enough pieces that if you try to grind them very very fine on the first
pass, it bogs down the mill and takes a long time and your throughput suffers.
So all the metal rolls up into little balls, and as soon as they reach quarter inch or
smaller they’ll come out of the screen, plastic as well. And by doing this, your throughput
doesn’t suffer, and the metallic material even in balls can come across the table and
down into the high-grade stuff.
All the metals and dense materials are going to come across the table this way, right up
under the water bar, and down into the number one and number two high grade. There’s going
to be a large band of base metals that come down here into the middlings. The plastic
and fine fiberglass go down into the tailings but there’s a sump in the bottom there,
that pumps it up into the hydrocyclone.
Here’s looking down into the hydrocyclone. And the premise here is the sump from the
tailings pumps up and discharges here, starting a swirl around the bottom of the hydrocyclone.
The dense material stays in the bottom and goes down this hole with the water, and back
into the hammer mill for regrinding. And only the lightest materials are carried up in the
column of water and go down the center hole here, and that’s the true tailings. It’s
very similar to a blue bol, for separating fine gold from black sand, it’s a density
separator. And you can see the material we’re regrinding still has some metallic values
there. And so they go down and regrind over and over in the system until the fine metals
are liberated and the fine fiberglass floats up and out the top of the hydrocyclone.
[Grinding noises]
So here’s the number one and the number two high grade, from the run we just did.
You can see it’s pretty much pure metal. Lots and lots of copper in there. And this
is the number one here, and all the free metallic gold and precious metal ends up in the number
one. Number two catches a lot of the base metals and we’ve also found that a lot of
the material, the precious metals that aren’t liberated, end up in number two.
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