The development of, among others, the Cerro Verde and Boddington projects over recent years has helped to establish the use of HPGr-based comminution circuit designs for large-scale hard-rock applications. These projects mark a return to the traditional stage-crush and ball mill plant designs that were commonplace before the widespread adoption of sAG milling, but with HPGRs now replacing cone crushers in the tertiary crushing stage.
The guidelines applicable to stage-crushing plant design and equipment selection are generally relevant also to HPGr-based plants, but the nature of HPGr technology requires the introduction of a variety of new rules to ensure a successful plant design.
The shift several decades ago to AG- and sAG-based designs resulted in a steep decline in the number of stage-crushing plants being installed in new projects, leading to the dissipation of the global stage-crushing knowledge base through reassignment and eventual retirement of experienced design and operating personnel. It is evident from some recent examples of sta- ge-crushing projects, both conventional and HPGr-based, that many of the principles governing plant design in this area have been largely lost to the minerals processing community. Experience that was once widespread is now focused in limited geographic areas or resides within a few individuals or engineering companies.
It is against this backdrop that this paper has been prepared, as a refresher for stage-crushing plant design practice and as a vehicle for communicating the special rules that apply to equipment selection in HPGr-based circuits. The paper addresses all stages of comminution and classification, from blas- ting to cyclone overflow, and includes infrastructure and ancillaries such as materials handling, dust control and tramp metal management.