Spontaneous combustion is a serious safety hazard in underground coal mines, particularly in mined-out areas (e.g., gob). It is estimated to be the cause of more than 20% of coal mine fires. Pressure balancing is a ventilation technique that can be used to reduce or eliminate the ingress of oxygen to the mine gob (in-gassing), thus reducing the risk of spontaneous combustion. At the same time, pressure balancing can also be used to reduce the risk of methane seeping into the mine ventilation circuits from the gob (out-gassing), due to barometric pressure changes on the surface. Two pressure balancing chambers have been constructed at the West Elk Mine, Colorado, operated by the Mountain Coal Company (MCC): one in a mined-out area, and another close to the active area, near a longwall mine gob. Each chamber is equipped with an isolation stopping, safety doors, a nitrogen injection system, and a set of pressure and environmental monitoring sensors. Several pressure balancing tests for different ventilation conditions have been conducted in these chambers. This study presents a summary of a procedure used to conduct these tests, the results achieved, and the steps taken to reduce the risk of spontaneous combustion.

A ventilation study was conducted on Kucing Liar (KL) mine. KL is the addition to PT Freeport Indonesia (PTFI) panel cave operations and is anticipated to operate in parallel to Grasberg Block Cave (GBC). The study consisted of model construction, budget preparation and investigating multiple scenarios to meet the minimum budget requirements. Utilization of new engine technologies, controlled partial air reuse, push-pull and utilization of Battery Electric Vehicles (BEVs) were considered during this feasibility study. A main intake and exhaust drift size optimization study was also conducted to determine the number of additional main fans and drift sizes required to support the KL mine. The results show the requirement for two additional 5MW main fans, two intake drifts and two exhaust drifts (7 m x7 m). The results also show the requirement for eight 6m ventilation raises to support primary air delivery to KL mine. Proof of concept trials are deemed necessary to determine the feasibility of applying some of the proposed concepts in underground operations (such as BEVs). The trial results will be used to complete a detailed ventilation network design.

A fan's operational reliability is a critical factor in ensuring that an underground mine's primary ventilation system enables and sustains the mine's continuous operation. At a time when underground mining operations are required to access ore bodies located at ever greater depths, primary ventilation systems are having to deliver volumes of fresh air over longer distances, thereby increasing the operating pressures applied to the ventilation fans. Increased production levels require larger volumes of air and increasing the ventilation system resistance or, alternatively, adding more primary ventilation fans to the ventilation network, which may result in the fan(s) entering the unstable part of their performance curve (i.e. the fan stall region). The search is therefore on for ventilation systems with a higher degree of operational flexibility and reliability to cope with constantly changing mine conditions.