A pilot-scale examination of a novel high pressure grinding roll / stirred mill comminution circuit for hard-rock mining applications

The mining industry will be faced with new challenges as the need to develop lower grade ore deposits expands to meet the rising demand for raw resources. Low-grade deposits require a substantially increased tonnage to achieve adequate metal production and have caused the consumption of energy in mining practices such as comminution to rise dramatically. If improvements could be made in the processes employed for metal extraction, the mining industry could remain sustainable for future generations. This research focused on the development of a novel comminution circuit design to addresses these issues. The circuit design incorporated two, known energy efficient technologies, the High Pressure Grinding Roll (HPGR) and the horizontal high-speed stirred mill, and examined the technical feasibility of a circuit operating without the need for a tumbling mill. The main objectives of this research were to setup pilot-scale research equipment and develop the design criteria necessary to operate an HPGR / stirred mill circuit. Testing consisted of using a copper-nickel sulphide ore from Teck Limited’s Mesaba deposit to evaluate a circuit comprised of two stages of HPGR comminution followed by stirred mill grinding. To evaluate the potential energy benefits of this novel circuit arrangement, energy consumption related to comminution was calculated for the circuit using power draw readings off the main motor and the throughput recorded during testing. To provide a basis for comparison, the energy requirements for two conventional circuits, a cone crusher / ball mill and an HPGR / ball mill, were determined through HPGR pilot-scale testing, Bond grindability testing and JK SimMet® flowsheet simulation. Results from this research showed that operating the first-stage HPGR in open circuit and the second stage in closed circuit with a 710µm screen, resulted in a circuit energy requirement of 14.85kWh/t, a reduction of 9.2 and 16.7% over the HPGR / ball mill and cone crusher / ball mill circuits, respectively. To assist in future HPGR / stirred mill studies, a refined testing procedure was developed with a reduced sample commitment and the ability to perform an energy comparison with a Semi-Autogenous Grinding (SAG) mill / ball mill circuit.Applied Science, Faculty ofMining Engineering, Keevil Institute ofGraduat