By Miguel Coelho, Ventilation Engineer at BBE Consulting and Hendrik Botma, Chief Technology Officer at VUMA Software
In December 1986, a mining tradition that dated back to 1911 ended, which saw the use of canaries in coal mines to detect carbon monoxide and other toxic gases before they could harm miners. Since then, technology has come a long way in ensuring ventilation safety which is critical as underground mining has gone deeper than ever before. With the world’s deepest mine extending 4.27 kilometres below ground, the deeper the mine the bigger the risk to worker safety. Engineers battle with rising virgin rock temperatures as depth increases. This necessitates more sophisticated measures for controlling heat and hazardous gases through ventilation, and the expense of establishing appropriate working conditions for deposits that are farther away from surface infrastructure has become a crucial factor in determining whether mining can continue. Here, mining ventilation simulation software has effectively automated and improved on the canary-in-a-cage concept, helping to predict that the subterranean environment is safe and productive for mining, by enabling adequate airflow at the correct approach temperature to work areas to mitigate worker heat stress. This too works to minimise and eliminate dangerous airborne particles below regulatory occupational exposure requirements.
Fresh air is everything
Oxygen is essential and in the underground workings of a mine, providing healthy, breathable air for miners is critical. This requires the removal of noxious gases, dust, and diesel particulates, which must be done according to strict guidelines from the Department of Mineral Resources (DMR), as well as any additional rules stipulated by the mining company itself. At the start of a project, the mining house will typically set a list of ventilation design criteria to guide the design and ensure it is fit for purpose and is energy efficient. Such systems must provide fresh, cool air and must remove heat from rock and vehicles while reducing flammable and machine exhaust gases. Airflow on a mine is managed by utilising surface-based mains fans – as air enters the intake shafts it moves through the mine, directed by various ventilation controls to the working areas of the operation. From the working areas, the air is directed through exhaust shafts and exits the mine through the main fans.
Ventilation is critical to mine safety
Without ventilation, there can be no mining as it has a direct impact on the safety and the productivity of miners. Ventilation is crucial as there is a risk of fatalities, injuries, chronic illness, explosions and low worker productivity as a result of heat exhaustion. Conversely, over-ventilation results in wasted costs in terms of energy consumption as ventilation infrastructure is a significant energy consumer on a mine. With increasing energy costs there is a continuous drive to optimise the ventilation system to reduce energy consumption. Some of the options to reduce energy consumption include the optimisation of airway and duct sizes, the reduction of leakages, sealing unused areas and detecting and resolving recirculation as well as the removal of unnecessary or excess auxiliary fans.
Ventilation on Demand technology
However, thanks to technological advancements, striking the balance between cost efficiency and worker safety doesn’t have to be a trial by error. It is possible to improve the mine planning cycle with the input of a ventilation specialist to inspect the mine design and schedule. This will allow for any necessary improvements to reduce the safety risk encountered when ventilation design criteria are exceeded, and the resulting potential reduction in capital and increase in running costs of ventilation infrastructure.
Smart ventilation controls applied to Ventilation on Demand (VOD) enables the delivery of the correct quantity of air to the correct place at the correct time, which ensures safety and energy efficiency. This mine ventilation software makes it possible to convert existing or planned excavations into airway objects, which can then be further refined by identifying factors affecting airflow (such as the wall roughness and excavations sizes) and heat pickup (such as age, depth and moisture levels). Ventilation equipment (fans, coolers, regulators) are also added to mimic the current ventilation flow. Once a model has been calibrated to current conditions, the user can perform numerous safety-related tasks, such as locating high risk areas, assessing the effect of ventilation changes and confirming the fan requirements.
Safety isn’t just a simulation
These software-based ventilation simulations allow for the accurate portrayal and prediction of expected environmental conditions, which makes it possible to correctly forecast the infrastructure that will be necessary to achieve an optimised ventilation design. For a mine that already exists, such simulation software creates a virtual replica of that mine which can be used to run simulations of any proposed ventilation system changes. This allows mine operators to determine beforehand the effects of changes and associated life of mine costs (both energy and implementation) to the ventilation system, without compromising safety, cost or productivity in any way.