Hello Harmony, your question much too vague. Unless you give specifics you are going to have to read the book. Here is the link:

Mineral Comminution Circuits - Their Operation and Optimisation (T.J. Napier-Munn - S. Morrell) 

Hi, I am not an international expert in this field (not even a national expert), but I'd like to give you some suggestions for where to start reading the book, from what I can recall from the time I was assistant to former Professor Leonard Austin, from Penn State University, during his sabbatical year in Chile (1986). In my opinion, you should be looking at:

1.- F80 and P80, i.e. the particle size you want in the product and the one you have in the feed to your grinding circuit. You want to keep P80 as constant as possible, as this affects the efficiency of downstream operations and/or your specific energy consumption. If F80 goes up, you'll probably have to reduce the passing load in order to compensate the disturbance.

2.- The tonnage you are passing through the circuit and the circulating load you are operating at, if a closed grinding circuit is being used. You can normally pass more when the ore hardness goes down, and vice versa. Circulating load self adjusts and provide indication of how easy or difficult is to break down your ore.

3.- Ball loading and mill power, two operating variables which are interrelated and should be kept within design range. Remember that balls continuously wear out, so that they are regularly made up to maintain a constant ball loading inside the mill. It is often a good operational practice to keep record of your unit steel consumption (i.e. ball weight loss by wear) per ton of ore subject to grinding process (usually in grams steel/ton). Sometimes they sell you poor quality balls, and the consumption will show that.

4.- Related to the previous point is the specific energy consumption, kWh/ton, a key performance indicator most grinding plants are watching closely. Variation on this could be an indication of variation in ore hardness. Poor performance on this indicator could tell you about suboptimal grinding media selection and quantity, suboptimal mill rotational speed or even mill inner liner wrongly specified or in bad shape.

5.- Mill noise, which could tell you if your slurry is too thin or too thick. Also a good practice is to regularly check slurry densities at different points in the circuit. This will tell you if your hydro-cyclones are working properly (spigots are also worn with time, and that affects the way your hydro-cyclone behaves).

Hope this helps and doesn't confuse you anymore, in a subject which is not that easy to grasp at first.

Notice that all of the above refers to ball milling (you also have rod mills, autogenous and semiautogenous milling, etc.).

Juan

Hi,In my opinion, except for the above, according to the tonnage of circulating load in AG/SAG mill and bearing oil pressure is also important.