A study on the comminution characteristics of diorite

The focus of this thesis was on the comparison in breakage behavior of heterogeneous diorite rock obtained at two separate quarry locations in Botswana. There are many problems associated with inefficient size reduction of quarry stones. Generally, when the material is left over sized, it will fail in its downstream operation because during separation/ screening the product will not pass to lower screens and it will require a secondary crushing activity resulting in a waste of energy and slimes challenges. Hence proper control of the desired product size range of material is of paramount importance in this industry. Current research efforts in comminution are mainly focused on issues pertaining to energy efficiency. Numerous intrusive activities that occurred during solidification and crystallization lead to development of many inherent material defects that substantially altered intrinsic characteristics of the igneous material thus presenting processing and material selection a very difficult task for many applications. Samples were collected from the central district region (Master quarry) and the north-east district (Panda quarries). Geochemical analysis was carried out via laboratory scale in-situ x-ray diffraction equipment as the initial step to identify composition for elemental contrast purposes. It was observed that a high crystalline phase percentage was identified for Panda rocks while a large amorphous phase constituted the Master diorite rock. An optical microscopy analysis aided in revealing surface characteristics of the samples. The grain distribution, grain orientation and grain size were determined to be the essential factors used to characterize material properties such as fracture toughness and hardness. The diorite rock from the central district showed an average grain distribution with an aphanitic texture or rather porphyritic texture due to fewer grain distribution appearances within a fine-grained matrix while the rock from the north-eastern region was mainly dominated with large crystal grains with a grain size slightly above 1 mm (Anthony & Smart, 2014). Unified crushing circuit comprising of the Jaw crusher, Gyratory crusher and a laboratory planetary ball mill was arranged to further investigate the mechanical properties of each rock species. It was found that the Master quarry rock type was much resistant to breakage as compared to the Panda rock type, a result that can be attributed to poor force distribution and transmission within the material and also numerous material defects like voids and porosity factors. It was also found from the particle size distribution (PSD) analysis of the Jaw crusher product that for each sample of the Master diorite rocks, the device required 41.58 KWh t -1 power to effect breakage while the Panda diorite rocks required only 38.33 KWh t -1 of power to break. The Master diorite rock sample is to a greater extent recommended for civil engineering works and infrastructural construction such as steel reinforcement. The structural intactness of components within the Panda rocks, and a characteristic high percentage (40%) of dark amphibole, this rock type is recommended for road construction and infrastructural work