Optimal utilization of a three-chamber pipe feeder system

Abstract

South African gold production is decreasing year-on-year. This can be attributed to numerous challenges faced by the gold mining industry. One of these challenges is high operating costs of which electricity forms a large portion. This is especially due to the electricity intensive nature of the gold mining industry, inefficient use of electricity and the aggressive rate of electricity price increases in South Africa. However, unlike most of the other challenges faced by this industry, this portion offers large potential for improvement. A large number of energy savings initiatives have been implemented over the years on the electricity intensive systems of gold mines. One of these systems is the water reticulation system because of its large potential for improvement in terms of electricity consumption and cost. The problem, however, is that maximised benefits are often overseen, especially with the implementation of multiple initiatives on this system. Specific reference is made to a three-chamber pump feeder system (3CPFS), which is an energy efficiency initiative that influences the performance of the load management initiatives. The main cause of the 3CPFS influencing the performance of load management initiatives was identified as the lack of integrated control between the sub-systems of the water reticulation system. These sub-systems include the 3CPFS, dewatering and refrigeration systems. A need was therefore identified to develop an integrated control philosophy to optimally utilise the 3CPFS to improve the performance of load management initiatives on the other two sub-systems. A water reticulation system of a South African deep-level gold mine (Mine A) was identified for the implementation of optimised strategies. Mine A has a 3CPFS installed and load management initiatives were implemented on both the refrigeration and dewatering systems. The performance of the load management initiatives was negatively influenced by the operation of the 3CPFS, which made the water reticulation system of Mine A an ideal case study for the implementation of optimised strategies. A step-by-step methodology was followed to develop a control philosophy that would integrate the operation and control of the 3CPFS with the other two sub-systems. The main focus with the control philosophy was to maximise the cost savings potential on the water reticulation system without negatively affecting the operational parameters of the system, hence influencing production. A verified simulation model proved the feasibility of the developed control philosophy in terms of complying with the operational limitations. The control philosophy was therefore implemented by incorporating it within a real time energy management system at Mine A. For redundancy, the control room operators were also provided with adequate training to manually implement the control philosophy in the case of emergencies. Mine A realised an average load shift of 6.3 MW on its water reticulation system with the optimised control philosophy. This was an improvement of 4.8 MW from the performance prior to implementation. This accumulates to a financial cost saving of approximately R4.4 million per annum. It was also proven that the operational parameters were not influenced by the control philosophy, which also validated the accuracy of the predicted results through simulation. All in all the optimal utilisation of a 3CPFS in a water reticulation system was proven.