New demand side management opportunities in the precious metals industry

Abstract

Currently there is an increasing demand for energy across the world. As the human population increases and new technologies find their way to previously difficult to reach areas, this is becoming an increasing problem. Various countries have implemented measures to save energy and provide sustainable development for the future. In South Africa this also holds true, and the state electricity supplier, Eskom, has been involved with energy management for a number of years. The most prominent energy management initiative is the Demand Side Management (DSM) program. This program was designed to provide measures to reduce electricity usage, as well as implement mechanisms to shift load from the peak electricity periods. These measures are usually implemented with the help of Energy Service Companies (ESCO's). In South Africa, there are numerous ESCO's, and many successful DSM projects have already been implemented in various industries. Since the precious metals industry is such a large role player in the economy of South Africa, it is natural that a large number of DSM projects comes from this sector. This is true, as can be seen from typical DSM projects on pumps, refrigeration plants, compressed air, and rock winders on South African mines. Since Eskom has not been able to meet its targets for DSM in the previous two years, a renewed effort has been made to identify and implement new types of DSM projects. In order to find new types of DSM projects, this study focused on the precious metals industry. It was found that DSM has not been implemented on precious metal plants such as platinum concentrators and Carbon in Pulp (CIP) gold plants. Since these plants also have various large pieces of machinery that might be amenable to DSM, this provided a starting point for this research. An audit was done on a platinum concentrator to investigate new DSM possibilities. It was found that large mills are used on these facilities that might provide large savings. Unfortunately, there are some problems with the current design of these plants, as well as oxidation of the material that seriously hinder implementation of DSM projects. The attention was focussed to CIP gold plants to the same end. These plants have various sections that have some DSM possibilities. The most prominent savings were shown to be in the milling circuit and the elution boilers. Research has been done to compare the energy cost of using various kinds of fuels to produce steam for the elution columns. It was found that coal is the least expensive fuel for this use. However, various transport and environmental issues preclude the use of these types of boilers. The next best option was the electrode boilers, which can save large amounts of electricity in an environmentally friendly way if controlled correctly. However, one of the most important results of this research was to prove that the milling circuits on gold plants can be used to provide large amounts of load shift from the peak periods. These findings have been enhanced by the development of a unique simulation model to predict the possibility of load shift on the milling circuit of any gold plant. The viability of load shift on the mills, as well as the accuracy of the simulation has been proven by implementing simulated load shift on an actual gold plant. Four other gold plants have also been used as case studies on which to implement the new simulation procedures. This produced valuable lessons in terms of load shift on the milling circuits of gold plants. In order to provide a starting point for future research, the simulation model has been expanded to include other industries. It was adapted slightly to be able to simulate load shift on the milling circuits of cement plants and chrome pelletizing plants. This once again proved the value of this research in terms of contributions to the DSM program in South Africa.