Date of Award

2016

Degree Type

Thesis

Degree Name

Master of Science

School

School of Science

First Advisor

Dr David Blake

Second Advisor

Professor William Stock

Abstract

During the last two decades, Western Australian iron ore mining industry experienced an exponential production growth arising from increased global demand for steel. The upturn in the iron ore price and considerably lower production cost encouraged extensive mining and consequently high-grade ore reserves were gradually depleted. Despite the energy-intensive nature of mining, high profitability motivated the mining companies to extract marginal-grade deposits with additional processing requirements, which increased energy consumption and ultimately increased the cost of iron ore production. This thesis sought to identify the energy efficiencies of open-cut iron ore mining operations, in terms of scale of operation as well as within individual mining processes, so that energy consumption could be reduced, and sustainability enhanced.

Efficiency indices were used to determine energy efficiency across different scales of operation. Overall energy consumption (per unit of processed ore) was directly related to the scale of operation, where large-scale mining operations are more energy efficient compared to medium and small scales requiring the lowest amount of energy to process a unit of ore. This suggests that an economy of scale based on energy efficiency can be observed in iron ore mining operations. Small-scale mining operations recorded the highest energy consumption to process a unit of ore, indicating the lowest energy efficiency among the three different scales of operation. However, the composite energy indicator indicated that the energy efficiency of a particular mining operation is also influenced by the geological and physical parameters of individual factors including the waste-ore ratio, grade of ore, average haulage distance and production capacity. The results of the regression analysis confirmed that it is the combined effect of all the aforementioned parameters that has a pronounced effect on the amount of energy consumed to process a unit of ore.

Energy consumption per unit of processed ore at different process stages revealed that the loading and hauling phase is the most energy intensive process stage in an iron ore mining operation regardless of the scale at which it is operating. The milling and stockpiling phase was the second highest energy consuming process stage, while the drilling and blasting phase was the subsequent energy demanding process stage in iron ore mining operations. Small-scale operations recorded a higher energy consumption in loading and hauling than the medium-scale operations, suggesting that the equipment with high load capacities and energy efficient technologies such as overland conveyor belts, and advanced technologies including autonomous haulage trucks resulted lower energy consumption in medium scale mining operations. However, the energy consumed to mill and stockpile a unit of ore in medium-scale operations was high compared to the small-scale operations, suggesting that the energy consumption in milling and stockpiling is mainly influenced by the properties of the mill feed, such as moisture content. Further, the amount of processing needed to achieve sufficient final product quality can also influence energy consumption.

Findings from this study support the idea that an economy of scale can be observed across iron ore mining operations in Western Australia based on energy efficiency. The study also provided essential baseline information for future studies on the variations in energy efficiency across different iron ore mining operational scales in Western Australia.

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