With the growing concerns about energy shortage and demand supply imbalance, demand side management (DSM) activities has found its way into the mining industry. This study analyzes the potential to save energy and energy-costs in underground mine ventilation networks, by application of DSM techniques. Energy saving is achieved by optimally adjusting the speed of the main fan to match the time-varying flow demand in the network, which is known as ventilation on demand (VOD). Further cost saving is achieved by shifting load to off-peak or standard times according to a time of use (TOU) tariff, i.e. finding the optimal mining schedule. The network is modelled using graph theory and Kirchhoff’s laws; which is used to form a non-linear, constrained, optimization problem. The objective of this problem is formulated to minimize the energy cost; and hence it is directly given as a function of the fan speed, which is the control variable. As such, the operating point is found for every change in the fan speed, by incorporating the fan laws and the system curve. The problem is solved using the fmincon solver in Matlab’s optimization toolbox. The model is analyzed for different scenarios, including varying the flow rate requirements and tariff structure. Although the results are preliminary and very case specific, the study suggests that significant energy and energy-cost saving can be achieved in a financially viable manner. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Electrical, Electronic and Computer Engineering / MEng / Unrestricted

Ventilation on demand (VOD) concept has earned significant worldwide attention by several mining companies in recent years. It is a concept where airflow is provided only to areas that require ventilation. The implementation of the concept has resulted in significant savings in annual energy consumption and cost for several companies globally. The research presented in this thesis sought to present the VOD system as an alternative solution and strategy to improve the ventilation system of Konsuln mine. The system is expected to cope with a planned increase in production rate and meet requirements in the new Swedish Occupational Health & Safety (OH&S) regulations, Arbetsmiljöverkets förtfattningssamling (AFS) 2018:1, which is based on the EU directive 2017/164 where Threshold Limit Value (TLV) for gases have been significantly reduced and provide safe work environment for workers in the mine. The thesis work started with planning and execution of a PQ (Pressure – Quantity) survey to calibrate the existing ventilation model of Konsuln mine. This was to ensure that the model is reasonably accurate to give reliable simulation predictions of the performance of Konsuln ventilation system in its current state and for the future. The good correlation between the modelled and underground measured values validated the model for further ventilation planning. The study further investigated and analyzed the current and future ventilation demand of LKAB test mine, Konsuln, to design a VOD system for its operations.The work outlined three main VOD design scenarios I, II, and III based on the proposed production plan, schedule, and the mining process that present the underground working conditions on the three main levels (436, 486 and 536) of Konsuln mine. Diesel, battery-powered, heat, and blast simulations were carried out for all the scenarios in the calibrated ventilation model using VentSim Design simulation software. The model was again used to estimate the annual ventilation power cost for the VOD scenarios to highlight the benefit and cost savings advantage under the VOD design system to deliver enough airflow quantity compared to the conventional system of ventilation. Simulation results showed that about 15.6% – 49.1% and 76.4% - 86.7% of significant cost savings will be achieved for diesel and battery-powered machineries respectively, while still supplying the needed amount of air to working areas to keep contaminants below their Threshold Limit Value -Time Weighted Average (TLV-TWA) and provide a good working environment. For additional benefits and savings of the Ventilation on Demand (VOD) system implementation, some considerations for equipment, personnel positioning and identification, monitoring system, and stations have also been discussed in this work.  These include; (i) Utilization of LKAB’s database system, Giron, in addition to mounting tags with unique IDs on machineries, to track the route of LHDs and trucks to deal with the challenge of airflow supply shortfall associated with auxiliary fans adjustment to affect target locations. (ii) Installation of temperature sensors, flow meters, gases and Diesel Particulate Matter (DPM) monitoring systems at specific, appropriate, and optimal locations in the mine for efficient implementation of the VOD system strategy. The heat simulations for both diesel and battery-powered machineries were carried out for the month of July when the highest temperatures in Kiruna are often recorded for the summer. They predicted the highest temperatures in working areas to be well below the limit used in Australia, 28°C Wet Bulb (WB). Four scenarios A, B, C and D were also considered for blast clearance time simulation using both the ramp and exhaust shaft. The blast simulation results indicated that the time to dilute and clear blast fumes through the exhaust shaft saves some clearance time compared to exhaustion through the ramp, although the shaft exhaustion will require additional financial commitment to purchase and install exhaust fans on each of the three main levels of the mine. Nevertheless, major ventilation work and practices such as removal of regulator in front of primary fans, additional radon measurement, and good auxiliary ventilation practices have been recommended to improve and actualize the benefits outlined in this work.