HPGR has been used for many years and is emerging as an energy-efficient alternative to conventional and AG/SAG comminution circuits. One of the interesting features of HPGR is its capability to produce a particle size distribution with a greater than typical amount of fines, thus reducing the power requirement for the downstream ball mill. This makes the use of standard ball mill analyses based on the K80 inadequate, unless appropriate corrections are made. (This problem is shared by AG/SAG mill circuits.)
High pressure grinding is achieved by an advanced type of grinding roll. Contrary to conventional crushing rolls, the particles are broken by compression in a packed particle bed, and not by direct nipping of the particles between the two rolls.
This particle bed is created between two choke-fed, counter-rotating rolls. Between these rolls, a particle bed is pressed to a density of up to roughly 85%of the actual material density. This compression is achieved by applying high pressure of up to nearly 300Mpa, exceeding the compression strength of the feed material. During this compacting process the material is ground to a wide particle size distribution with a large proportion of fines, compacted into flakes.
High pressure grinding is achieved by an advanced type of grinding roll. Contrary to conventional crushing rolls, the particles are broken by compression in a packed particle bed, and not by direct nipping of the particles between the two rolls.
This particle bed is created between two choke-fed, counter-rotating rolls. Between these rolls, a particle bed is pressed to a density of up to roughly 85%of the actual material density. This compression is achieved by applying high pressure of up to nearly 300Mpa, exceeding the compression strength of the feed material. During this compacting process the material is ground to a wide particle size distribution with a large proportion of fines, compacted into flakes.