In this week’s blog, we seek to respond to a common question that we hear at MinAssist: what is the return I get on investing in process mineralogy? The short answer is it is not always easy to quantify in reality as there are often many factors at play at any given time, but an effective benchmarking study is of course always a good place to start to give you some indication of the ‘before’ picture – against which to measure changes. The same benchmarking study can be used to also provide a good indication of where to go next with regards testwork, modelling and flowsheet design.
Here, by way of example, we have highlighted 3 recently published case studies that highlight how process mineralogy has been successfully integrated with geometallurgy and metallurgical testwork to provide tangible benefits. One is from Xstrata based on the Nickel Rim South deposit, one from Rio Tinto’s Kennecott operation, and the third from the Anglo Platinum group’s operating concentrators.
Lotter et al (2011) provide an excellent summary of process mineralogy work undertaken by Xstrata on the Nickel Rim South deposit. In particular they describe the challenges they faced in resolving complex mineralogical and textural processing issues, and how the use of process mineralogy allowed the testing of various hypothesis, and the ultimate development and modelling of a new processing flowsheet. The study demonstrates how metallurgical testwork can be combined with mineralogical testwork to effectively and efficiently achieve process diagnosis, flowsheet design and optimisation. It also summarises the return on investment and highlights how process mineralogy can be used to benchmark plant performance, and help predict the effect of changes to the plant operating conditions ahead of time.
Six distinct geometallurgical populations were defined based on their mineralogical characteristics, and flotation tests carried out on representative composite samples from each unit. These demonstrated that each had a unique grade recovery response. Based around this understanding of the behaviour of each unit, a “virtual flowsheet” was developed, tested and subsequently implemented. This was found to lead to a strong recovery improvement across the board (22% Ni, 16% Cu, 23% Pt, 24% Pd for one ore) validating the return on investing in process mineralogy and integrating it with metallurgical testwork.
MacDonald et al (2011) present a study that brings home how critical an understanding of the mineralogy is when trying to reduce losses in a plant. An on-going process mineralogical study was implemented in 2005, monitoring routine samples to evaluate overall plant performance. An important recognition is highlighted: that rock type and element grade do not provide enough information to allow recovery to be optimised. The integration of mineralogical understanding allowed the ‘recovery triangle’ of operating philosophy, plant mechanics and mineralogy to be completed. With plant mechanics set, and the mineralogy of each feed ore understood, variations in recovery could only be down to operating philosophy.
On the basis of this work, over 30 ore units were reduced to 5 processing domains, each with a known metallurgical response. These allowed the plant to be operated in such a way as to maximise recovery from each unit. In addition, a number of ‘tribal myths’ about the cause of copper losses were investigated; and in the most part found to be partially or wholly incorrect. Armed with a full understanding of the real causes, based on statistically sound evidence-based information, suitable decisions could then be made to redress these.
Rule and Schouwstra (2011) summarise how Anglo Platinum have invested heavily in process mineralogical capabilities over the last 20 years to leverage improved metallurgical performance, particularly from increasingly complex ores. They highlight how in order to maintain an ongoing drive for continuos improvement, it is essential that this be based on a high level of understanding of the rocks, minerals and their processing characteristics. This knowledge can then be fed in to improved decision making across the board, from planning of green or brown field projects to plant design and optimisation.
A benchmarking program for each of Anglo’s concentrators was implemented, characterising feed, concentrate and tailings samples on a routine basis to provide data on:
– changes in feed mineralogy, and in particular those that influence the flotation process
– composition of the concentrates, both in terms of the valuable minerals and the mode and occurrence of gangue
– the deportment of valuable minerals to the tailings
This information can then be used to understand the impact of both changes in the feed, and to evaluate the stability of the plant.
Several case studies are presented by way of example, and whilst this optimisation work is an on-going process, PGM recovery rates now regularly exceed 88%.
Rule and Schouwstra summarise this by saying: “process mineralogy has established itself as the key technology supporting the development of better flowsheets”.
For more information on process mineralogy, and to discuss more specifically the potential benefits to your operation, please feel free to contact us at www.minassist.com.au/blog
Lotter, N.O., Kormos, L.J., Oliveira, J., Fragomeni, D., Whiteman, E., 2011. Modern Process Mineralogy: Two case studies. Miner. Eng. 24, 638–650.
MacDonald, M., Adair, B., Bradshaw, D., Dunn, M., Latti, D., 2011. Learnings from five years of on-site MLA at Kennecott Utah Copper Corporation. 10th International Congress for Applied Mineralogy, Trondheim, 2011.
Rule, C., Schouwstra, R. P., 2011. Process mineralogy delivering significant value at Anglo Platinum concentrator operations. Presented at the 10th International Congress for Applied Mineralogy, 1-5 August 2011, ICAM, Trondheim, Norway.