An integrated approach towards the optimization of ventilation, air cooling and pumping requirements for hot mines
Webbeer-Youngman, Ronald Clifford William
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This thesis contends that optimization of energy resources through active control and predictive simulation modelling is possible, and that such monitoring l e d to large savings in the electricity costs of hot mines (where refrigeration has to be employed). In addition, active monitoring and control can positively affect the establishment of a safe, healthy and productive working environment. In the entire optimization process certain guidelines were set to ensure that the requirements of the Mine Health and Safety Act were met. Varying the quantity of air supplied underground by means of Variable Speed Drives (VSD's) is one of the crucial factors in the interactive approach towards the optimization of ventilation, as is refrigeration and the pumping requirements associated with refrigeration. This research highlights the interaction between the amount of air supplied and the effect it has on refrigeration requirements underground. This thesis also considers the effect that this would have on contaminant control. Various tools are available for ventilation and cooling design for mining. These tools are based on the assumption of steady state conditions and do not take into account instantaneous changes in conditions day to day or hour to hour (such as for temperature and contaminants). They also do not take into account the optimization of energy resources related to the creation of the acceptable underground conditions. With these tools worst case and best-case scenarios are identified and strategic decisions are made accordingly. Currently, the amount of the fresh air, the velocity of the air, and its general temperature in the mine are only changed when one production phase changes into another (or when unacceptable conditions occur as a result of poor design or neglect). This means that during a specific production phase (which can last for several months), there can be an oversupply, or undersupply, of energy resources, which will obviously affect the concentration levels of the various contaminants (through under or oversupply of air). Studies done at the Target Mine in the Free State, South Africa, investigated the possibility of optimizing air cooling, air supply, and water pumping. A unique simulation programme was designed for the mine - initially to monitor how the mine normally utilized energy resources in air-supply cooling and water pumping. Once this had been done, an 'optimization schedule' for energy use on the mine was established using predictive simulation. A potential saving in energy costs of approximately R2.6 million per annum was identified This study en& with recommendations for the implementation of simulation programmes, as well as with suggestions for future work.
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