Sustainable use of inlet guide vanes to reduce energy consumption of main ventilation fans

Abstract

The rising cost of electricity has urged mines to research and implement new energy-saving initiatives. Little research has focused on energy saving techniques on main ventilation fans (MVFs). MVFs extract hot, humid air from underground operations, which induces fresh air via a downcast shaft. However, the operation of MVFs is an energy-intensive operation, with installations ranging from 1 MW to 10 MW. Incidentally, inlet guide vanes (IGVs) are one of the many methods that can be implemented to reduce the energy consumption of the MVFs. IGVs reduce the work of the impeller by reducing the volume drawn through the impeller. IGVs are primarily installed as an energy-savings initiative on the MVF. However, IGV control must be implemented with care to ensure that adequate ventilation is provided to underground working areas. Therefore, a generic solution is proposed which aims to guide project engineers and site personnel toward the sustainable implementation of IGV control on MVFs. The solution will maintain ventilation requirements by actively monitoring real-time data from underground environmental sensors measuring ventilation flow, dry-bulb, wet-bulb temperatures and air pressure. Furthermore, the integrity and operation of the MVF are maintained by condition monitoring of vibrations and bearing temperatures. Sustainable benefits can be feasible and realised through active monitoring in the control of IGVs. Therefore, to ensure sustainable operation of IGVs, a comprehensive investigation was done into common issues that arise from IGV control and the main cause behind previous installations’ failures. A case study was used to implement IGV control where previous IGVs had been installed but never utilised. The chosen IGV control strategy determines the sustainability of IGV control. The proposed strategy mentioned in this document was revised with the feedback from the active monitoring of various factors, including condition monitoring of the MVF and underground ventilation. Furthermore, to construct a sustainable control strategy, extensive testing was conducted to ensure MVF vibrations were acceptable throughout all IGV positions. Upper and lower limits were set on the corresponding actuators to prevent detrimental vibrations from not occurring during normal operation. A calibrated ventilation simulation model was used to ensure adequate ventilation flow is provided to maintain a safe underground environment. Previous IGV installations made use of an “open-design” that commonly corroded inside the MVF which resulted in detrimental failures that led to vanes being sucked through the impeller. These design flaws were rectified by installing a sealed central hub. This unit is sealed from corrosion and offers reduced maintenance intervals. Condition monitoring alongside the maintenance of key performance indicators improved IGV control on the MVF. With condition monitoring capabilities alongside a maintenance plan, IGV control could be implemented on mining main fans to realise sustainable energy savings. It was found that the energy consumption can be reduced by 9% with a mere 2% reduction in volume extraction. The implementation of IGV control was able to achieve daily energy savings of 16.03 MWh in this case study, while realising electrical cost saving of R 4.6 million for the first year of implementation. With real-time data monitoring, underground ventilation requirements are met to ensure a safe underground environment. The implementation of the generic solution proposed by the author that revealed that IGV control can achieve major energy savings, provide fan performance and, most importantly, sustain mining ventilation. The study further revealed that the improvements made to the initial IGV design ultimately led to the sustainable implementation of IGV control on the main fans.