Ann: Annual Report to shareholders, page-129

Hey Bdigii,

To quote your reference "Have I got it right in thinking you monitor the output product to ensure that the output grade is as required, and that to do that you have flexibility to change numerous variables, such that you can increase grade by adapting the mixtures and energy usage, in effect making your process more efficient relative to the % recovery (say taking 90% recovery to 95%) at the cost of increased input / energy costs?"

In a nutshell that is correct, my job as a control room operator is to operate and run the systems designed that control all the plant variables in a processing plant. ie,

if I change or increase the tonnes into the plant by a variance of 5-10% (100-250tonnes) lets say that's what that equates to, it will have a flow on effect or a "butterfly effect" in the entire process, it will change the density in your hoppers, as you are adding more product and increasing the throughput, so the increased density as more particle's are now in the circuit, will then have a flow on effect on your pumps, they will have to work harder to pump more volume and solids, which then will effect your water consumption as it will require you to add more water to your hopper to reduce density. if your running your system in a density controlled way.

there is a thing called "cascade loops" its a control processing feature that takes 3-4 different controllers lets say "new feed, mill speed, and pump speed" it combines them all and tries to control them all evenly.. so if one changes they all change to suit.

back to the increased tonnage, that will also effect the end process by adding more volume to hoppers and in part increase yield and recovery.

so many variables can be changed in a process, to improve the recovery and final product grade..

you can put in 1000tph and achieve poor results in the end, if you aren't controlling all the effects of the process philosophy, or the process itself.. each section, each bit needs to be controlled and things added/taken away.

like HPAL that has slurry pumps, heat, pressure, chemicals (acid being added) it has so many variables, that the smallest change to any of them effects the entire process and output you desire..

that's my role.. to control the plant and know what each change I make has on the whole process, how one small variable and change can effect the entire process downstream.

JD.