VENTILATION
According to Erasmus, factors in the mine’ s overall operations were taken into consideration and the team concluded that a complex design would not be suitable for fulfilling the ventilation needs of the mine.“ Our main goal was to ensure that our ventilation solution provided higher efficiency while at the same using less energy. This led to a simpler design and installation plan for the fans which also carried the benefit of lower costs and more efficient operation for Subika,” Erasmus explained. The installed fans will run at an optimal efficiency of 87.5 %.
Vent network design
Last year, Howden acquired Chasm Consulting and its widely used Ventsim™ software. Earlier this year Howden released the latest version – Ventsim DESIGN 5.0. This is a major upgrade to Ventsim 4, and includes many new features and improvements.
It has now been integrated with the Howden Fan Selection Tool – which allows users to connect directly to the manufacturer’ s web-site to recommend a fan to meet the pressure / flow required by the model, and then automatically import available fan curves into a VentSim DESIGN model. New features of Ventsim™ DESIGN 5.0 include: n Faster and more efficient – new algorithms, memory management and parallel processing greatly improves simulation performance n New simulation tools – a wide range of new simulation tools for heat, moisture, airflow and error finding build on the existing power of Ventsim n CONNECT option to link Ventsim to the real world – view and control underground ventilation devices( such as fans and regulators) directly from the ventilation model and see instant feedback n New VentLOG™ version with stronger integration to Ventsim – a significant upgrade to the popular VentLOG tool There is an improved Graphics Engine; faster and smoother graphics, particularly on large models – Ventsim graphics libraries have been optimised for modern computers. Parallel processing and multi-thread technology means simulations and screen graphics can update independently and simulations can run faster.
Sensitivity analysis and error checking can check and predict areas of models where users are more likely to create problems from input errors.
Batteries and automation
Global ventilation expert and a regular correspondent of IM, Pierre Mousset-Jones of the University of Reno, has provided comments made by members of the SME Underground Ventilation Community( UVC), noting that“ a big issue these
days is the impact of battery powered equipment on mine ventilation needs. Many mines use their main haulage decline as their intake airway, so diesels are going full power dumping all their fumes in the clean air.” So there is a“ big advantage for battery, also the heat output difference is significant which impacts hot mines and cooling needs.”
There is a drive in Sweden and Finland where“ ventilation can be reduced when all machineries are automated.”
One aim of automation is to reduce the number of mineworkers inside an underground mine, and hence reduce OH & S risk. An example is the Volvo driverless mining truck that is being trialled at Kristineberg mine in Sweden, https:// www. youtube. com / watch? v = uOlsTeNqt Q8. Of course, there has been a Sandvik autonomous truck fleet at Finsch diamond mine for some years, and there are others in Canada and elsewhere.
Brian Huff, Chief Technical Officer of Artisan Vehicles presented Heat Generation in Battery Electric Underground Haul Trucks at this year’ s CIM meeting in Vancouver, stating: n A diesel truck produces 7.5 times the heat of a battery electric truck n 40 t diesel truck produces 3.75 kWh of heat per tonne per km n Z40 battery electric truck produces 0.5 kWh per tonne per km n At 960 t / d hauling 2 km on a 15 % grade, a diesel truck produces 6.2 MWh more heat than a battery electric truck in one day n Enough surplus heat to heat the average home for one year. Mousset-Jones comments:“ I’ m yet to be asked about whether ventilation can be reduced when all machineries are automated. But I believe that this question will arise sooner or later, especially as the SIMS( Sustainable Intelligent Mining Systems) project is going into its second year and I’ m also involved in another work package about outreach and dissemination which covers communicating SIMS project results to public, students and mineworkers.” So his answer to that question would be:
“ Yes, there is a case to reduce ventilation when all machineries are automated. However, these machineries still need maintenance which is done by a human. Moreover, these machineries can break down at working faces and require a human to fix them. There is also a risk of these machineries catching fire and damage to the automated fire suppression system, which requires human intervention to extinguish the fire.“ So I believe that the ventilation system can be scaled down compared to the one in the nonautomated mines, but the system must still have an ability to provide adequate ventilation to
allow a safe atmosphere for humans to work in. For example, the airflow might have to be increased in the event of machineries breaking down or catching fire. The underground workshop, fuel bay are certainly manned and therefore must have adequate ventilation for humans to work there. The explosive magazine also needs to be adequately ventilated to keep its temperature low and to manage fire risk.”
Another thing to consider is that in deep hot mines, high temperatures and humidity might affect the electronics of the automation system and robots, so in this case a significant amount of airflow might be required to create‘ safe’ environment for these automated machineries.
There is also a need to keep the ground support in good working condition. Without minimum flows humidity and temperatures can rise and cause degradation of bolts and mesh and infrastructure. There have been many examples of this where teams return to mines that have been placed on care and maintenance.
It is unlikely we will ever get to no people underground but we will definitely reduce the number.
For the BEV mine SIMS has come up with a minimum flow to enable temp control and air movement. One aim of SIMS is to improve safety in underground hard rock mines by replacing diesels with battery machineries, introducing automation of mining machineries, and develop mining robotics. Much work is directed at reducing the number of personnel inside an underground hard rock mine.
The project will demonstrate the feasibility of Epiroc ' s large battery powered LHD( 14 t) and truck( 42 t), and jumbo( two booms) in term of their operational performance and financial benefits compared to their diesel counterparts. They will be trialled in Agnico Eagle Finland ' s Kittilä mine between April and December next year. Productivity, availability and ventilation reduction will be measured. The plan is also to observe and solve operational issues such as battery replacement, battery charging, maintenance issues, operators and maintenance personnel concerns, and calculate cashflow of using these machineries. Similar tasks will be undertaken on the existing mine diesel LHDs, trucks and jumbos and then the results of these tasks for both types of machinery will be compared. The project will be the first to measure and quantify ventilation reduction because the ones available in published articles and presentations are based on the comparison between the efficiency of electric motors and diesel engines. It is believed that no-one has ever measured and quantified the ventilation reduction of replacing diesels with battery machineries.
Basically the project aims to show that it is now feasible to start replacing diesels with
46 International Mining | JULY 2018