A new model between the Bond and Hardgrove grindability based on volumetric powder filling by using limestones

Abstract

Grindability measurement as a testing method can be divided into two general categories; the Bond (Gbg) and the Hardgrove grindability index (HGI). Grindability of coal and minerals is influenced by mineralogical parameters, machine parameters and operating parameters. In this study, a Hardgrove mill was used to investigate the grinding behavior of six limestone samples due to the simplicity and the potential usage of the method for the determination of the grindability of limestone on a comparative scale. Up to now, a study determining the effects of the HGI values according to volumetric powder filling still does not exist, especially based on the relation between the HGI and the Gbg. In this study, the six different limestones were tested to determine the effect of powder filling which is one from shortcomings of the Hardgrove grindability. Then, a relationship was establish between the Hardgrove grindability, which was obtained depending on three different volumetric powder fillings, and the standard Bond grindability of limestones. As a result of tests, it was seen that the volumetric powder filling could be important in the grindability in Hardgrove mill that can simulate vertical grinding mills. Additionally, a good relationship was found between the HGI and the Gbg from the presented model, and the validity of the model was proved by a high regression coefficient (R2 = 0.971).