I wanted to start our exploration of process mineralogy in the middle of the mine life cycle, with its use in process optimisation and troubleshooting. Why start here you ask? Well process mineralogy can have the biggest impact and finds the most use in this area so it is a great introduction.
As a rule, from my experience the mineralogy of an ore is given lip service in process design and is generally considered the realm of the geologists. Key ore minerals are usually identified but a deep understanding of the minor ore minerals and gangue is rarely obtained through feasibility, piloting and design. Invariably, once commissioning is completed and the plant is operational the name plate recoveries are not achieved and a process of optimisation and general troubleshooting is undertaken. It is at this point that smart project metallurgists get hold of a process mineralogist to help them dig into the fundamentals of why recovery is low or grade targets are not being achieved.
When done to support these optimisation or troubleshooting projects process mineralogy can often quickly and efficiently identify the fundamental cause of problems, hence allowing metallurgical testwork to focus on identifying and validating potential solutions. When used early in the process, mineralogy can effectively focus the program and allow faster progression to results, minimising guesswork and ensuring that improved recoveries are achieved in the shortest possible time.
Where is it best used?
Process mineralogy can find uses in virtually all optimization and troubleshooting studies where ore processing is necessary. Traditionally, this focuses around recovery or grade improvements in flotation or leaching. However, there are numerous innovative ways to use mineralogy in everything from ore sorting or comminution to process contaminant identification. Mineralogy can even be used in tackling problems in water management, through understanding of de-waterability or slurry properties, or environmental management.
These diverse applications also extend to commodities. Copper, Base Metal Sulphides, Nickel, Industrial Minerals and precious metals have been the traditional domains for mineralogical studies but increased applications are being seen in Fe Ore, uranium and even extending to coal.
What this tells us is that process mineralogy can and should be the first thought in establishing optimization or troubleshooting programs in virtually any situation. This can then be further extended for integration in ongoing monitoring of aspects such as feed variability or unit operation performance to reduce the risk of problems arising again.
Where does mineralogy fit in a study?
To use mineralogy most effectively it should be integrated right at the beginning. Using mineralogy at this first step can help define the root cause of problems or inefficiencies and really focus a study. This is especially important if the problem is a complete mystery but even when you have a good idea of what is going on mineralogy can be used to quickly validate those thoughts and give a good basis for justifying further expenditure.
Designed well, a mineralogical study can provide solutions that then must only be validated by metallurgical testwork. This takes a lot of guesswork out of the process, eliminating wasted resources and allowing faster, more efficient completion of the whole project.
How can it be done?
The key to use of mineralogy in these types of studies is to utilize efficient integration with the metallurgical component of the testwork. Numerous methodologies have been presented on how to achieve this and it is beyond the scope of this overview to explore all of them. However, the key theme to remember is that mineralogy can be used to guide what areas should be focused on in metallurgical work.
The emergence of automated mineralogy as an industry, predominantly with QEMSCAN and MLA, has greatly enhanced the usability of mineralogy in metallurgical studies. With these systems it is possible to get statistically relevant information quickly and for important areas that it was previously very difficult to deal with. Huge amounts of data are produced in these systems but the most widely used are analysis for liberation/locking characteristics and mineral associations. An understanding of these fundamentals, along with accurate mineralogy, can immediately show us things like why specific minerals are not being recovered, what other minerals they generally occur with and what needs to be done to liberate them.
In my opinion automated mineralogy, simply by making mineralogy more accessible, has removed most of the hurdles faced by metallurgists in its use. The bottlenecks and ambiguity associated with manual optical mineralogy no longer exist. Metallurgists can now generate mineralogical data tailored specifically to their projects and presented in a fashion that is clear and understandable.
Why go to the extra effort?
If I haven’t made this point enough so far, the reason for using mineralogy in optimization and troubleshooting is simply to streamline the process, giving better results both faster and cheaper. In times like today, where every dollar is hard to come by, spending a little more up-front on a mineralogical study of material can save time and money later in the project. For these types of project turn-around time is a key factor as every day recovery is not improved or sub-standard concentrates are being produced directly affects the profits at the end of the month. If by using mineralogy as the first step in the project you take some of the guesswork out of the metallurgy and only have to validate the solution then you have immediately saved money and produced a faster result.
I have been working in this area for a number of years now and almost every project I have worked on an understanding of the mineralogy has pointed to the solution. Often the mineralogy was done as an afterthought and used to explain why various approaches didn’t work. I believe that by doing it last you are wasting an opportunity that could be gained by getting a direct understanding first up.
I encourage you to think about where you use mineralogy in optimization or troubleshooting and then where you could have used it. I would love to hear your comments on whether it helped solve a problem and if you have any questions please post them or contact me directly.