MechChem Africa May-June 2024

Ventilation on demand: the opportunities and the risks Russell Hattingh, MD of BBE consulting, and specialist ventilation consultant, Hannes Potgieter, present their perspectives on ventilation on demand (VoD), what it is, why the mining industry should be interested and how to best apply it to optimise mine ventilation while minimising risks.

Primary ventilation involves drawing surface air through the mine, usually using an exhaust fan on the surface that pulls clean and cool air through the mine’s ventilation shafts.

W hen planning a mine ventila tion system, Hattingh says some key decisions need to be made in terms of the pri mary and secondary ventilation strategies. Primary ventilation involves drawing surface air through the mine, usually using an exhaust fan on the surface that pulls clean and cool air through the mine’s ventilation shafts and, once it has been distributed to active mining areas, bringing that ‘used’ air back up to the surface through the main exhaust-air shafts. Once underground, the air has to be distributed to wherever miners are work ing. This is done through secondary under ground ventilation systems that draw the fresh air off the main intake airways, usually via ducting, and distribute it to the working places – the production zones and develop ment ends. Every mine has a well-defined ventilation network that enables ventilation practitio ners to know and control exactly where the air is coming from, where it is going, how it is being routed safely via return airways to the surface and finally discharged back into the atmosphere. It is important, Hattingh cautions, to remember that the core purpose of ventilat

fully productive in that environment. Ventilation and refrigeration are, in many cases, the largest consumers of electricity in underground mines, especially as mines become deeper. To draw in and exhaust say 500 m 3 /s of air for 24 hours, 7 days a week needs a primary ventilation fan, drawing anywhere between 600 kW and 3.5 MW, a huge amount of electrical power. “The idea underpinning VoD,” Potgieter says, “is to pull in only the air that is needed by the operating production zones. By apply ing a VoD strategy, we strive to optimise the ventilation requirements at all the points of need; which, if done well, can lower a mine’s electricity use by a huge amount.” While primary ventilation systems con sisting of main intake and return airways remain fairly constant, the dynamic nature of production scheduling may call for venti lation supply in active production zones to be adjusted on a shift-by-shift basis. A VoD design involves mostly secondary networks, which tend to use smaller fans and ducting. “This is the dream,” continues Hattingh, “to minimise the ventilation power require ments without affecting miner safety or production targets. VoD can turn ventilation on and off, like lights turn on and off when

ing a mine is to enable mining to progress safely. “Our job as ventilation specialists,” he says, “is not to provide office-type air conditioning, but to ensure that we support the dynamic process of mining and safeguard those working underground from harmful airborne contaminants and heat.” Every ventilation strategy must be developed around the layout and mining method of the mine. This is particularly true of the secondary ventilation system, as these areas differ considerably from mine to mine, depending on the type of mine, mining method, mining equipment, nature of the ore body, as well as airborne pollutants and heat associated with the orebody and mining process. The key question here is: how do we effectively and efficiently ventilate pro duction areas to enable mining to progress unhindered?

Which is where ventilation on demand comes in.

Highlighting the motivation underpinning VoD, Potgieter points out that ventilation needs to remove and dilute heat and air-born pollutants, such as blast and diesel exhaust fumes, flammable gases and dust, so as to keep miners safe and to enable them to stay

24 ¦ MechChem Africa • May-June 2024