Abstract

Metal mines have to deliver the energy metals that will make it possible to achieve the Green Transition to a low-carbon economy by 2035 and the projected demand for copper and nickel demand by then is significantly higher than current production levels. While mines are used to demand growth of 1-3%pa, the projected metal demand growth is closer to 13-15% compounded annually to 2035 and beyond. The only way for underground mines to meet this demand is to significantly reduce operating labour and energy costs by implementing autonomous, continuous production systems.  

Underground metal mines have relied on the existing production platform since 1985 except for increased scale. Open stoping mines with blasting and backfill activities, as well as block caving operations with auto-fragmentation processes, continue to rely on a batch process LHD and trucks to deliver coarse ore to the crusher and hoisting system. Some operations have automated the LHD or truck activity, but the units themselves remain essentially the same. Batch units leave the ore pile untouched 80% of the time and consume 80% of the energy used to move ore. Other production activities such as access development, production drilling, blasting and backfilling remain essentially manual activities. To avoid safety risks in access development, some mines have trialled mechanical excavation systems, but most mines continue to use drill-blast techniques. The most recent change has been the replacement of diesel engines by electric motors and batteries for haulage units, making the units heavier for the same payload.  

Conveying systems are well-known to be a more time- and energy-efficient and move material faster then batch systems but coarse ore is too dense an abrasive for belt conveyors. Recent innovations such as Railveyor™ and Muckahi™ are more efficient but rely on rail system and the continuous loader has stop loading while new empty cars return to the loader. A series of steel chain conveyor units lined up behind the loader overcomes this limitation and this is the concept behind the rubber-wheeled Mascot™ System. The units are aligned to move coarse ore continuously from the source to the rock or ore pass. The units are stationary while they are conveying, use direct power, using batteries only for relocation when the ore source is exhausted. The system is autonomous and the energy per tonne moved is only 20% of that of an LHD. Simulation of a block caving operation with continuous, autonomous ore flow indicates a production cost of roughly 60% with further cost reduction for lower ventilation demand.      

Autonomous systems will rely on machine-to-machine (M2M) communications and data drones to cover any gaps in the data flow. Low-cost conveying enables ore sorting by managing the reject material efficiently. Continuous, autonomous equipment and fewer personnel underground reduces ventilation demand and allows for smaller access development. Taken together these changes lowers operating costs significantly, lowers cut-off grades, increase mine-life and producing more ore profitably.