The effect of feed moisture on the comminution efficiency of HPGR circuits

The comminution efficiency of high-pressure-grinding-rolls (HPGRs) is a well described function of a number of feed parameters including grindability, abrasion index, granulometric composition, top size and particle size distribution. Far less studied is the effect of feed moisture. This paper investigates both the overall and the specific comminution efficiency of a circuit consisting of a pilot HPGR unit followed by a batch ball mill as a function of the moisture level in the HPGR feed. Forsterite olivine sand (−7 mm) supplied by Sibelco Nordic was used as feed material. The results showed that the relationship between moisture and crushing efficiency for both the HPGR and the circuit can be described successfully by means of a parabolic function. Dry material, as well as that with the highest moisture content, showed the lowest particle size reduction ratios irrespective of the specific grinding force level. The paper also analyses the phenomenon of flake generation and shows that the feed moisture influences the flake content in the coarser size fractions of the HPGR product.

► Relationship between the feed material moisture and reduction ratio has a parabolic form.
► Flakes generation is generally more intensive for olivine feed with higher moisture content.
► Moisture content increase has unfavorable influence on the process energy consumption.
► Product size reduction in downstream ball mill operations is higher for HPGR feed with higher moisture content.