In grinding, the use of steel media in a rod/ball mill circuit clearly diminishes the subsequent froth flotation performance over purely autogenous grinding. The use of recycle water in grinding also clearly diminishes the subsequent froth flotation performance associated with fresh tap water. Some of these flotation deficiencies
Two different circumstances must be addressed for the reduction or elimination of overload risk: a) in existing operations, or b) in the design of new grinding circuits. The methods necessary are in the first case an adjustment of operating conditions; and in the second an adjustment of mill shapes.
Existing Operations: from Equation
Fines may be defined as any material smaller than a specified product size, and “coarse” as any material that is larger. The target 80 percent passing size of the grinding circuit product is a convenient reference point, as it is often used to express the grind size objective. This size is close to the modal value of typical size distributions
Once the basic operating conditions have been defined for the mill designer then, and only then, can he begin taking into account shell and head stresses and trunnion bearing sizes required to carry the load and to give the required openings for feeding and discharging the mills.
Mill heads are key structural components of any grinding mill. They
Ff the drill cores indicate that the ore could contain sufficient lumps in the sizes needed for ore media in autogenous and semi-autogenous grinding, then bulk samples (750 kg) of mine run or primary crushed ore, with an even distribution by quantity in the size fractions between 100 mm and 200 mm, should be obtained for media competency tests. The
The factors upon which the rate of flow of the pulp through a mill depends appear not to have received extensive investigation. In an article by Anselm translated by Pearson a method for the calculation of the time of passage of cement through a ball mill was given. The basis of the method is that the volume rate of throughput is
The phenomenon of “surging” in a mill is a subject upon which very little has been written; presumably because it is a condition which cannot be tolerated in mill operation and which must be eliminated by variation of some or many of the physical dimensions or characteristics of the mill or mill charge. The phenomenon known as “surging”
In the previous chapter the influence of the various physical quantities defining the mill and mill charge has been studied in connection with the performance of a mill as a device for the creation of new surface in the powder. For some purposes, however, it is also desirable that the product should have a preferred form of size distribution curve.