A new laboratory test for the estimation of wear in high pressure grinding rolls

As 75 up to 85% of the exhausted energy in mining and mineral processing industries is used for comminution processes, more energy efficient crushing technologies such as high pressure grinding rolls (HPGR) can help to reduce the consumption. Differing chemical compositions and physical properties of minerals due to origin and pre-treatment aggravate a wear prediction of the roller material, a key indicator for cost efficiency. To determine the wear characteristic of different minerals with respect to the complex wear system, consisting of abrasive wear (scratching) and surface fatigue (indentation), a laboratory scale apparatus is put into operation. The main wear influencing variables are roll speed, geometry and composition, grinding pressure and characteristics of the feedstock. Scaling up gained data on industrial processes assumes fundamental understanding of the coherences between these variables. Therefore, the influence on wear behavior of three selected parameters, grinding pressure, grain size and moisture of the feedstock are presented in this paper. The tests are carried out with rolls made of the martensitic hardened steel AISI L6 with a diameter of 100 mm. The feedstock consists of silica sand (Bottrop, Germany) with grain sizes ranging from 0.2 mm to 2 mm to meet all demands concerning comminution in a confined material bed. Accompanying to the tests, traces of wear on the roll surface are examined with a scanning electron microscope (SEM). The tests add up to an increase in wear rate, i.e., volume loss per 1000 revs, as a result of increasing grinding pressure, an increase of the maximum feedstock grain size and an increase of feedstock moisture. Assumed wear mechanisms could be verified. The results provide for a better understanding of the complex wear system of HPGRs. More precise wear estimations of varying minerals is part of the ongoing work.