Case study: Energy savings for a deep-mine water reticulation system

Abstract

In deep level mining, water reticulation systems are one of the major consumers of electricity. The refrigeration plants, together with the underground water supply and dewatering systems are integrated to form one complete water reticulation system. This integrated water reticulation system extracts hot water from the mine, cools it down and returns the cold water to the various underground mining levels. As much as 42% of the total energy consumption on a typical deep level gold mine can be ascribed to the water reticulation system. Reducing the overall water demand and therefore electricity costs will depend on climatic conditions, operating strategy, water reservoir capacity, and electricity tariff rates. In this paper, a method is presented to determine the optimum water reticulation strategy for different electricity tariffs. This model minimises the total operating cost of the water reticulation system by a trade-off between the cost involved in providing effective pump control and the savings achieved under a specified electricity tariff. A case study of a typical deep mining operation shows that a reduction of 65% during peak demand and 2% overall electricity reduction is possible by adopting this new control strategy. The corresponding savings in operating cost is 13%. Techniques were developed to integrate, simulate, optimise and control all components of the water reticulation system. This will allow for a quick assessment of the effect of individual components on the complete system. By integrating all these components into a single system, the operation of each component can be assessed and optimally controlled without adversely affecting other operations of the system.