Hi Loki,I find myself sceptical that the underpowered IsaMill...

Hi Loki,

I find myself sceptical that the underpowered IsaMill and ball mill had no impact on recovery rates, because I understand that recovery rates depend on grinding the feedstock finely. The fineness improves recovery by improving the degree of exposure of particles to the chemicals used in gold extraction. If the grinding equipment is underpowered, the only way to achieve this fineness is to substantially increase the grinding duration. However, this naturally reduces throughput rates, and thus reduces gold production, so throughput and recovery rates are at odds.

Given that the key performance criterion is gold production, I would expect that PGI would have chosen grind durations that compromised between recovery rates and throughput rates so as to produce the best overall result. Sure, that might produce more wastage through reduced recovery rates, but better to accept that for a few months than risk going broke.

Once substantially increased power levels were available from the IsaMill and ball mill, the grinding durations could be re-optimised to simultanously improve throughput rates, particle size reductions, recovery rates, and gold production. I suspect that we've yet to hear fully how that re-optimisation process has worked out.

Just my speculative interpretation of the situation. I have no inside information, and I could be quite wrong.

Grav