The BBE Group has released the 2021 version of its flagship mine ventilation simulation software, VUMA-network, which is being offered free to the mining industry. MechChem Africa talks to Russell Hattingh, MD of BBE Consulting and Hannes Potgieter, Senior Ventilation Consultant for BBE Consulting.
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“My background is mine ventilation and refrigeration in the mining industry and as a ventilation consultant I use VUMA-network software to define mine ventilation systems and determine underground cooling needs. Once the requirements are defined, BBE refrigeration engineers design the specific refrigeration stations,” begins Hannes Potgieter, Senior Ventilation Consultant for BBE Consulting.
“VUMA software adds a huge amount of value to our offering at BBE. We can use it to simulate a whole range of scenarios in the underground mining environment to help us design better ventilation solutions and to help clients to manage their underground environments in terms of energy efficiency, workplace ambient conditions and safety,” adds Russell Hattingh, MD of BBE Consulting.
The development of an underground mine, according to Potgieter, starts with accurate knowledge of the ore body. Then, mine design experts develop the mining methodology and mining methods. “Our role is to design the systems needed to enable people to work safely underground in a well-ventilated atmosphere at temperatures that are conducive to the hard work miners do,” he continues.
“The first thing we tend to see is a mine plan given to us by the developers. We then identify how best to ventilate and cool the areas where the mining will take place.
“Initial mine planning is based on geology, rock engineering and how best to access the ore body. We get involved early in the design process to give guidance on additional requirements for delivering chilled air, for example, and provide recommendations as to mine plan changes required from a ventilation perspective to enhance economical and safety outcomes,” notes Hattingh.
BBE’s VUMA-network software is able to create a 3D model of an underground mine network, which can almost always be established relatively quickly by importing data from an AutoCAD model of the mine layout, for example. Once an accurate model has been established, algorithms developed from 20 years of experience in underground conditions are used to calculate how the target air quality and temperatures can be achieved. “We typically design to an average working wet bulb temperature of between 27.5 and 28.5 °C. This target temperature directly influences the ventilation and cooling requirements,” explains Potgieter.
Describing heat sources underground, he says heat from rock, machinery and auto compression in deep mines are the main contributors. “At the Mponeng Gold Mine, which is the deepest mine in the world, for example, heat due to auto-compression accounts for almost 50 MW of heat. In addition to this, the typical virgin rock temperature (VRT) at a 2.0 km depth in South Africa will be between 40 and 50 °C, but can be as high as 70 °C in some cases,” he notes.
“Every kW of electricity that is consumed underground – by equipment, lights, or vehicles – also converts directly into heat, which typically adds up to several megawatts of heat. All this heat has to be removed, either by chilled air sent down from the surface, and/or by chilled water produced underground or pumped from surface and delivered to underground air coolers,” Potgieter explains.
“Having built an accurate 3D model of the mine, VUMA-Network first does an air flow solution. Then, by adding the heat specifications to VUMA for all contributors and the working locations, we will get a clear idea of the ventilation and refrigeration requirements necessary to meet the mine’s needs. We can then run various scenarios involving different ventilation and refrigeration technology options to find an optimum solution that will offer the mine the best value for money in terms of energy efficiency and capital investment,” he informs MechChem Africa.
Potgieter explains the two broad options open to ventilation and refrigeration engineers for maintaining a healthy air flow and temperature: “As air descends into a mine the temperature increases due to auto-compression, significantly reducing the potential cooling capability of the ambient intake air; to such an extent that in ultra-deep mines in South Africa, ambient intake air adds to the mine’s heat load. In these scenarios, circulated air must be kept to a minimum with mechanical air cooling from chilled water and/or ice being used to cool the underground environment.
“For mines of up to 1 500 m, large scale bulk air coolers on the surface, typically producing 400 to 500 m3/s of chilled air at 10 to 12 °C, are used to provide cooling, with powerful fans exhausting the chilled air through the mine.
“Chilled water can also be used as service water for drilling, dust suppression, cleaning and other underground maintenance tasks, while still contributing to offsetting the heat load,” notes Potgieter, adding that VUMA software is able to optimise the ventilation and chilled water balance very accurately and quickly between all available options.
“There are a lot of other variables apart from depth that need to be considered, though. For mines making use of diesel equipment, chilled water may be needed at much shallower depths due to the heat given off by machinery. Mines in Ghana mining at depths of less than 600 m rely on big surface coolers that provide up to
14 MW of air cooling due to the massive heat loads associated with the underground machinery, and the elevated ambient temperature in central Africa on the surface, which can be as high as 27 °C wet bulb,” Potgieter informs MechChem Africa.
Hattingh continues: “Ventilation and refrigeration are among the most costly operational expenses on a deep mine, so minimising the energy required becomes a critical aspect of mine design. There is, therefore, growing interest in the use of electric vehicles underground, because of their potential energy savings and emissions performance.
“Mines also tend to be extensive and subject to constant change. They have a magnitude of branches that affect the flow of air getting to where it is needed. VUMA gives users the reliable answers they need to accurately optimise air and heat flow – to within a degree. And best of all, the software is free, not only for mine developers but also to help mine operators manage their ventilation and refrigeration resources on an ongoing basis,” he adds.
“For new mines, we can plan for the life-of-mine operation and consider initial, build up and ultimate requirements, while for operating mines, the software can identify how to best respond to changes.
Mine managers are routinely shutting down depleted workfaces and opening up new areas in search of profitable ore bodies. This changes the air and heat flow paths. BBE’s VUMA-network simulations can accurately determine the effects of these changes and how to optimise and manage changes to the system,” Hattingh explains.
Other software capabilities include:
- Transient modelling: “Mining companies value their workforce and take great care to ensure work is carried out as safely as possible. To achieve this, mine management establishes evacuation procedures in the event of a total power failure. VUMA can quickly determine the time it would take for the temperature to rise to dangerous levels,” explains Potgieter.
- Underground fires: VUMA is able to simulate where the gases would go, the concentrations of smoke and the temperatures in different areas of a mine.
- When designing a ventilation system, all airborne contaminants must be considered, such as, flammable gases, dust, vehicle exhaust fumes and a host of other potential dangers on a mine. Factors related to these hazards are built into VUMA as design criteria to address associated risks.
VUMA gives our clients a clear view of actual and potential underground ventilation and cooling requirements and how best to meet these needs. The product is free, and we at BBE are available to add our expertise to implement any new needs that VUMA predicts are necessary,” Hattingh concludes.
