Abstract
This paper deals with the development of a volume based closed-cycle grindability test method based on the recently introduced Universal Hardgrove mill and procedure. Five model materials with various origin and material characteris- tics (hardness, grindability, heterogeneity) were chosen for the experiments, i.e. limestone, quartz, andesite, basalt and cement clinker. The grindability of the material was characterized simultaneously in four various ways: 1) the standard Hardgrove Grindability test (HGI), 2) Bond work index calculated from HGI, 3) the conventional Bond test and 4) the closed-cycle volume based grindability test in the Universal Hardgrove mill. The grindability coefficient (G), and the cumulative particle size distribution of 80% passing size (x80) of the product of the closed-cycle Hardgrove test were determined. Relative deviation of the above parameters was very good (in most cases lower than 3%) which indicates the new proposed method as a robust procedure for rapid determination of specific grinding energy of closed cycle grinding in ring mills. Therefore, this test is able to ease the optimization of grinding conditions relatively fast and reliably.
Highlights
Grinding has a very wide range of application in the industry, i.e. minerals, wastes, biomass, chemicals, pharmaceuticals, etc. (Juhász and Opoczky, 1990; Nagy, 2010; Mucsi and Rácz, 2017; Mucsi et al, 2019)
Using an Australian and a Chinese coal sample collected from power stations, this paper demonstrates the effects of particle size and density on coal breakage, and elucidates the deficiencies associated with the traditional Hardgrove Grindability Index (HGI) test
The particle size distribution (PSD) of the ground material was measured by a HORIBA LA-950V2 laser diffraction particle size analyzer in wet mode using distilled water as a dispersing media and sodium-pyrophosphate as a dispersing agent applying the Mie-theory as an evaluation method
Summary
Grinding has a very wide range of application in the industry, i.e. minerals, wastes, biomass, chemicals, pharmaceuticals, etc. (Juhász and Opoczky, 1990; Nagy, 2010; Mucsi and Rácz, 2017; Mucsi et al, 2019). The grindability or the resistance of materials against a mechanical effect is a very important material characteristic. This property significantly affects the milling operation, the efficiency of the grinding process, the power requirement of the grinding, etc. Optimization and the specific energy demand determination are based on the knowledge of the grindability of a given material. Grindability is generally characterized by the grinding work required for a unit weight or a unit volume of material. This material property is determined in a standardized apparatus under exactly defined conditions. The most widely known and utilized grindability tests are the Bond, Hardgrove and Zeisel methods (ASTM D409-71, 1931; Bond, 1943; Zeisel, 1953)
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