Efficiency, Economics, Energy and Emissions – Emerging Criteria for Comminution Circuit Decision Making

The ‘smarter’ approach to processing described in this paper is limited to the benefi ts of a more effi cient high pressure grinding roll (HPGR) circuit over a traditional semi-autogenous grinding (SAG) comminution circuit. The effi ciency challenge described concerns comminution circuit designs that are relatively risk averse and compliment current mainstream engineering practice. The HPGR effi ciency assessment aims to motivate more widespread use of HPGR technology, particularly for the copper and gold mining industry. The summarised results presented stem from the completion of several SAG versus HPGR trade-off studies conducted in the past few years. Trade-off studies primarily relate to evaluating effi ciency in engineering studies in terms of energy and project economics. In this paper, an additional sustainable aspect incorporating the impact on environment is evaluated. The concept is presented through the analysis of three case studies where ‘typical’ mines A, B and C are viewed by considering the impact the design has on the environment. The methodology followed culminates in new measures, standards and targets that can be used by engineers to aid the decision making and process that ultimately justifi es plant designs which are eco-effi cient and more sustainable. The results show that a 15 20 per cent reduction in direct energy (kWh/t or ‘energy cost’) is achievable through the use of HPGR circuit designs. HPGR circuits eliminate the need for grinding media and result in a 23 25 per cent reduction in operating “dollar” costs. The salient feature from evaluating HPGR circuits over SAG-based circuits in terms of reduced environmental impact (or reduced carbon footprint) showed that up to 26 39 per cent less total energy (direct + embodied energy) was required to process the same quantity of ore and produce the same quantity of metal. This appears to be a generic feature of HPGR circuits irrespective of the operating conditions.