⎪ Heating, cooling, ventilation and air conditioning ⎪
Mining occurs at multiple levels and across different time periods. Before mining begins, a level needs to be developed. And depend- ing on the chosen method, one level could be mined while the level below is prepared. At each level, secondary fans channel air from the primary ventilation system into the level being developed or mined. The secondary ventilation system also returns the ‘stale’ air to the primary return system, says Hattingh. “So, the primary system needs to get enough air down to the level in question, while the secondary system distributes the air on each working level,” he adds. When designing a system, because there isn’t an infinite supply of primary air, a fixed quantity is allocated to each level. With ventilation-on-demand, there is a perception that the primary fan is continuously adjusting up and down to match demand. “That's not true. It may be necessary during a brief period if the mine needs to enforce load clipping, for example. In general, however, any disruption in the primary air supply means that mining must stop in some areas because not enough air is available,” Russell Hattingh points out. “So, we design each level for a fixed amount of available flow, using ventilation-on-demand to make sure that each drive, be it a rim drive, an ore drive or just an inspection, receives the necessary pre-allocated air. Ventilation-on- demand must start with mine design, typi- cally with a minimum supply in mind to avoid oversizing the primary fans. We right-size the secondary ventilation systems to match the
mine planning sequence, so that the primary can always meet the secondary demand of all active drives,” he explains. Ventilation-on-demand at Venetia This managed approach is well-suited to mining applications with multiple levels that are not all being worked simultaneously. “We are currently implementing a ventilation-on- demand system at Venetia and going through the process of putting the design together, finalising the control philosophy and how the ventilation system will fit into the way the mine is going to operate,” Hattingh says. The mine is using a progressive sublevel caving operation, where multiple drives will be developed, but only a few will be mined at any one time. “The new on-demand system we are implementing will help them manage the air they are already using by applying a more effective ventilation control system to secondary circuits being fed by the existing primary system installed a few years back,” he explains. The new ventilation strategy aims to sup- port Venetia’s health, safety, and sustainabil- ity objectives, so a fully automated, digitised approach has been chosen. “Instrumentation is key. It is the backbone of any successful control solution. Dampers or duty-controlled fans are used to regulate flow, and sensors monitor the impact of each adjustment. The instrumentation collects flow, temperature and air quality data from each area to ensure that any change to the system achieves expectations, without over-
or undersupply of air, and without causing an unintentional undersupply elsewhere,” he says. “As you can imagine, the infrastructure required to achieve this across a working mine is substantial. Every fan and every area of the mine needs sensors to collect the necessary data. All that data needs to be collected and sent to a central controller via a reliable com- munication network for real-time analysis, and the controller must then continually man- age each fan speed and/or damper position. “It’s an idea that's spoken about a lot, but it's seldom fully automated. At the end of the day, we see it as a way to ensure miners re- ceive the airflow they need, where and when they need it. “Ventilation-on-demand is about giving mine operators peace of mind that the cor- rect quantity of air is going to the right places, which will result in a healthier workforce, better productivity and fewer unplanned work stoppages due to heat exhaustion, overheating equipment or poor air quality,” says Russell Hattingh. “We are in the early phases of implement- ing this strategy at the Venetia diamond mine. We are starting on one level, and once we have proved its functionality in one working environment, we will roll it out level by level as mining progresses. “We are very excited. In South Africa, this will be the first automated ventilation-on- demand system at this level of complexity,” he concludes. https://bbegroup.com
The Venetia diamond mine is transitioning from surface to underground operations, preserving one of the country’s most prominent sites while setting new benchmarks for sustainable mining.
January-February 2025 • MechChem Africa ¦ 31
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