What is a Mill and how Big should it be?

Milling is about taking the sorted crushed, mineralized rock from the Mine, and making into a slurry so we can float the minerals off. How do we do that.

First we put it into a ball mill for a first mill, the size we want to float we send straight to the float cells, anything larger, then we regrind it to the size we want for the float plant, and send it on its way, etc.

So how do we determine the grind size. We engaged Metsolve Metallurgical Lab’s of Langley BC, Canada, to do the testing to determine the best grind size for maximum flotation recovery. P80 was what they came up with.

That is a fancy way of saying best recovery grind size is 80 microns, very fine beach sand

A 100 and 200 ton a day mill is actually quite large, as there are a lot of rocks we have to grind to fine beach sand size, so why is ours so small?

At the Mine, we sort the rocks to get rid of all non-mineralized material, and one would be surprised to see how much of that is mined, The ore-sorter obviously eliminates a lot of that, but there is material that holds a lot of mineralization that bypasses the Ore-Sorter, so our milling floating capacity is geared to that, or a approximately 50 ton/day

We now have the upgraded Bayhorse Mill back together and operating with the larger grinding capacity. Although we have the ability to process up to 4 tons per hour, or a maximum 96 tons per day, in practical terms we operate at 65% – 70% capacity, or from 2.6 tons o 2.8 tons per hour, or between 62 tons – 68 tons/day

The major (heavy work) completed consisted of a larger grinding mill, with the original mill becoming a regrind mill.

So we coarse crush, then send it to a cyclone separator through a high capacity pump. The input into cyclone, just as in a natural cyclone, has substantial rotational forces, so the heavy material (typically oversize), drops out the bottom as an underflow, while the smaller particles go out the top to a conditioning tank.

We now add a reagent (PAX) in very small amounts (50 grams/tonne) and that attaches to the sulphides. We then add another two reagents, MIBC and Aerophine, that assists in creating bubble in the float cells, where it is very vigorously agitated. The sulphide minerals attach to the bubbles, and we scrape them off in a well proven, low-tech process.

We take that, what is now float concentrate, thicken it, pump it into a dewatering screen, and sack it in 1 tonne supersacks.

Now what happens? We are in the sampling and testing phase, that takes some time. Each 1 tonne back needs to be sampled, and an official assay established, as well as a Material Safety Data Sheet (MSDS) so the buyer of any concentrate we make knows exactly what we are selling, and they are buying. Needless to say, this “Due Diligence” is a time consuming process, and we must have the Lab results before we can officially say, ready for sale. (Contractual Agreements are very precise, and confidential, so we cannot say much about it)

With the addition of all the dewatering circuits and the precipitation circuit, a substantial amount of the piping and pumps between the circuits has gone in. All the equipment we have installed is on a plug and play basis, to allow for flexibility of easy interchange of modules.

Grinding mills on left, reagent addition circuits center, float cell on right