Investigation of microcrack formation in vanadium-titanium magnetite using different crushing processes

Abstract

Characteristics of microcracks in vanadium-titanium magnetite crushed by high pressure grinding roll (HPGR) and conventional jaw crusher (JC) were investigated. In crushing by both HPGR and JC, stress cracks, intragranular cracks, and cleavage cracks were developed. Stress cracking was the initial stage and fundamental basis of fracture. The intragranular cracking could accelerate the comminution process and thus increase the content of fine particles in the crushed products. Cleavage cracking could enhance the liberation of valuable minerals and gangue minerals. Narrow size fraction samples were prepared and characterized by optical microscopy, scanning electron microscopy (SEM), the Brunauer, Emmett, and Teller (BET) method, mineral liberation analyser (MLA), and Bond ball mill. The specific surface area and pore volume of the HPGR products were found to be significantly higher than for JC products due to the presence of abundant microcracks and a higher fraction of fine particles. Compared to the JC products, the HPGR products showed a better degree of liberation and lower Bond ball mill work index (BWI), although the difference gradually decreased with increasing fineness of grind. The application of HPGR not only reduces the energy consumption in the subsequent grinding process, but also optimizes the separation of vanadium-titanium magnetite and improves the TiO2 recovery in ilmenite.