Controlled Primary Ventilation Recirculation and Re-use with Reconditioning—A Strategy for Deep Mines

Australian underground mines are inevitably getting deeper particularly where steep dipping ore bodies are involved. The mining depths will eventually extend beyond original mine design horizons at which point the installed ventilation infrastructure will generally not be able to sustain mining needs. The ventilation systems will become strained due to system resistance, higher leakage, auto-compression and rock temperatures. Furthermore, with increasing depth, more trucks will generally be required to sustain production rates. These mines will start to experience local hot zones and areas of flow stagnation along the trucking declines. At this stage, the primary ventilation systems will require upgrades, and this could include ventilation raises [surface and u/g], additional refrigeration capacity and high pressure fans [or booster fans]. These infrastructure upgrades will require significant investment with long project lead times. At depth, the technical feasibility of successfully establishing longer raises also becomes an important consideration. Strategies that employ controlled recirculation of the primary ventilation, with reconditioning, can offer solutions that allow deferral of the new infrastructure. Furthermore, if effective scrubber technology can be developed, primary ventilation upgrades could perhaps be avoided. The reconditioning of primary ventilation is technically feasible and advantageous from a mine cooling perspective. However, the issue that has prevented mines from adopting the technology on a wide spread basis has been gas and respirable particulate management. This paper considers the merits of controlled recirculation, advantages of employing these strategies and scrubbing technologies that should be the subject of further research. The paper also examines how a controlled recirculation strategy could conceptually be implemented in a deep mechanized mine. It is argued that the significant cost associated with primary ventilation upgrades warrants a critical review of controlled recirculation and R + D investment into related technologies.