LeftyTheBandit said:
Do you feed items into the hopper I see top left of the picture?
Yes. The ball mill, along with an agitation tank, were built to process a specific lot of ore. I had only four 5 gallon buckets of the stuff, but recovered over 40 ounces of gold. The ore had a head assay that ran about 325 ounces/ton. I say about, because with such a high grade ore, you can get various assay returns, which proved to be the case on the few I had run. So then, the ore, which was crushed to ½" minus, was loaded in the hopper to be fed slowly to the ball mill. It was a continuous operation, not a batch run.
Does the hopper lead to a screw mill? Feed into ball mill?
I designed a feed wheel that had two small buckets. The gear motor you see in the picture reduced speed considerably, then I used the large and small gear belt pulleys you see to power the wheel. I don't recall the RPM now, but it was quite slow. Maybe 10 rpm. The ore was dropped from the wheel into a large funnel/elbow assembly that ran a seal against the ball mill to prevent losses.
If you noticed, there's a cylinder behind the hopper. That contained water that was re-circulated after settling. The water was discharged through a nozzle in the elbow, washing the material into the ball mill. I had a small valve that controlled the volume of water that entered the ball mill, which also regulated the amount of time the solids would stay in the mill. The ball mill sat at a slight angle, to compensate for the large intake than discharge diameter. That was an added feature, when I discovered the original small intake was problematic.
For the record, lime was introduced to the ball mill on a regular basis, to insure that the pH was higher than 9½. The ore was a sulfide, plus likely had tellurium as well. Cyanide alone did very little, but oxidizing with bromine solved the riddle instantly.
I also see that there is a ramp that leads into a scrap box. Does the ramp transfer the mill or does the grind'ed material just flow down the ramp? Is the ramp even part of your mill?
By now you likely understand that the ramp transferred the slurry to the container, where it was classified. I had a fine screen that separated particles that were not fine enough to process with cyanide. They were returned to the mill for a little more punishment. Very little didn't make it through the first screening. To minimize large pieces being discharged, the discharge trunnion had a series of round rods that ran across the bore, preventing anything larger than 1/8" from leaving the ball mill. I had to make the classified size that large because I extracted quite a bit of gold that was up to that size, but nothing larger.
The ore was spectacular----showing bands of gold in areas---although the gold was quite fine in general. Much of it was just a gray looking area, but was gold. A particle magnified @ 400X was totally pocked with tiny bits of gold. It was for that reason that I crushed the ore so fine--so it would all be exposed to cyanide for extraction.
Should any of the readers ever get near my location, I still have samples of the ore, a gift to me from the owner of the ore that was processed. It's a sight to behold! 8)
Hope this answers some of your questions. Feel free to inquire if you have more.
Harold
An added comment.
The chute was made of copper. I originally had hoped to recover the majority of the gold by amalgamation. Turns out the gold wouldn't cooperate. A piece of the recovered gold would float on mercury, and not wet. The solids that I recovered yielded something like 30% gold. It is for that reason I think the ore contained tellurium. I have no way of knowing, not being a chemist