Using comminution energy intensity curves to assess efficiency of gold processing circuits

This was the title of a paper by G R Ballantyne, A Mainza and M S Powell presented at the World Gold Conference 2015, Johannesburg, South Africa, 29 Sep – 1 Oct, 2015. It has just been released by The Coalition for Eco-Efficient Comminution (CEEC) and considers the industry’s need for an effective method and platform to benchmark comminution energy intensity and motivate action to improve productivity and earnings. The familiar cost-curve format has been used to develop an energy curve report which conveys the comminution energy intensity of a specific mine in relation to other operations. The energy curve program allows operators to establish their current operating efficiency. It is designed to motivate the adoption of best practice by creating a competitive incentive to move “down” the curve towards a more cost efficient position i.e. improving energy productivity. The energy curve is populated from a database covering a significant proportion of gold, copper, lead, zinc and silver producers. CEEC International is supporting the industry’s use of this program by making it available to the global industry; in line with their role as an industry-good organisation.

This paper focuses on the use of the comminution energy intensity curves for the characterisation of circuit efficiency as a tool for increasing circuit energy productivity. Five interchangeable metrics have been used including kWh/t, bond work index and size specific energy. The generation of new 75 µm material is used to calculate the Size Specific Energy (SSE) which has been previously been demonstrated to be a practical and fair measure of energy efficiency. The SSE is calculated across individual equipment, sections of a circuit or the full circuit enabling the benchmarking of comminution equipment against each other. The SSE Intensity energy curve is used to highlight the circuit inefficiencies at two mines; reinforced by more detailed circuit analysis. A methodology for assessing performance using energy curves and the calculation of SSE energy has been expanded in this paper. These methodologies clearly show the value that can be gained from improving energy productivity across the circuit.

The picture shows a standard SSE calculation around ball mill circuit 1 at Mine 1