Operating Characteristics of HPGR
There are many factors to be considered when specifying an HPGR and selecting an appropriate flowsheet for a given application. The following subsections summarize the more important issues.
The compressive strength of the material to be crushed determines the amount of useful energy that can be absorbed by the material, which in turn dictates the bearing and motor sizes required for a given duty.
With studded roll wear surfaces, the compressive strength of the ore, in combination with the feed particle top size and operating pressure, will largely determine the probability of stud damage—the higher the values of each of these variables, particularly when they occur together, the higher the likelihood of incurring stud damage. Ongoing development of stud technology is aimed at reducing the sensitivity of the studs to these variables.
The abrasion index of the material being crushed will determine the wear rate (as distinct from the breakage rate) of the studs, as well as that of the substrate metal. For example, the wear life at the iron ore operations at Los Colorados and Empire are about 14,000 and 10,000 hours, respectively, while those at the Argyle and Ekati diamond mines were about 4,000 hours initially, but increased to 6,000–8,000 hours and beyond with ongoing development of stud and edge protection configurations.
HPGRs are not generally suitable for the treatment of highly weathered ores or feeds containing a large proportion of fines. (This of course does not apply to applications where all the feed material is fine, such as fine grinding of concentrates.) Fine and weathered material tends to cushion the action of the rolls and so reduces the efficiency of comminution of the larger feed particles. For example, Argyle bypasses its primary HPGRs when very fine ore is being mined. On these ore types, the fine or weathered material should be removed by prescreening if HPGR treatment of the coarser compo- nent is required.
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