Increasing yield from the orebody through blasting entails identifying a number of critical elements that have to be implemented, mainly drilling, choice of explosives, increasing levels of safety and productivity, and training of crew.
In order to ensure long-term sustainability of their operations, mining companies are, mainly, focused on three areas: increasing efficiency in operations, cost containment and enhancing safety in their operations from pit to port. And one of the obvious target areas is drilling and blasting, which is the bedrock of a mining business. Generally, yield from an orebody is very closely linked to the fragmentation performance of the blasting process.
Getting the desired output requires meticulous planning and implementation in the process of drilling and blasting. In fact, all factors should be taken into account.
Frik Fourie, Head of New Mining Technology for Platinum at Anglo American, describes to African Mining Brief what is involved to increase yield from fragmentation in blasting: “The yield is a mixture of quite a few drivers that need to be set up correctly to give the best fragmentation. In this manner, you can recover the largest percentage of metal in the process circuit at the lowest cost in order to create value.”
Elements central to increasing yield
Essentially, increasing yield entails identifying a number of critical elements that have to be implemented, mainly drilling, choice of explosives, increasing levels of safety and productivity, and training of crew.
Otto Coetzer from Vula Drilling, who regularly works with Anglo American in complex hard rock drilling and blasting projects, says that, in drilling, hydraulic drilling technique in this context, appropriate equipment and consumables must prioritised. That is why quality and relevant consumables have to be used unfailingly, he highlights.
“For instance, in hard rock mining, nature of the rock determines the type of drill bit to be used. In platinum mining, different reefs have different rock conditions – there is nothing like one-size-fits-all in drill bits. Rock conditions determine the drill bit to be used. A product that works in certain rock conditions won’t necessarily work in another,” demonstrates Otto, adding that, before drilling, parameters like distance between holes and concentration of energy into a hole have to be considered and the type of explosive to be used.
Fourie mentions the key role of the energy that is used and distributed per square metre in blasting. “The driver is the energy/ m2 for the rock type that depends on the timing, burden and explosive type that is used. The properties of the rock material and the hardness play a big role in this process.”
The quality and relevance of explosives contributes to better dimensional control and fragmentation, and faster cleaning cycles. This improves safety and performance in the underground mines.
- Safety and efficiency
As much as possible, the idea is to take out risks posed to the crew, both from handling the equipment and from the environment, by endeavouring to increase safety measures, explains Coetzer.
For instance, firstly, where there is requirement for sufficient lighting, light technologies that can make the environment safer should be provided, suggests Fourie.
Furthermore, physical and mental fatigue can have a toll on performance of the personnel, on top of increasing the risk of injury in the course of drilling. The use of new technologies eliminates those risks. For example, new electro hydraulic drilling systems make the drilling cycle on the working face faster, lowers noise and vibration levels significantly. The technology improves fragmentation and throw capabilities of the explosive that is applied.
One of the means of increasing productivity in drilling and blasting is reducing the time dedicated to anchor installation and other tasks. Anchor installation, a time-consuming exercise, is one of the biggest hindrances to crew productivity.
- Training of crews
Last but certainly not least, it is worth noting that, in underground mining, labour constitutes up to 70% of the total cost. And this is the most expensive resource that needs to be optimised. And so, regular training of staff on best practices in productivity and safety is essential, Foure mentions. “Training of crews and obtaining their buy-in at the outset is critical.”
Generally, as Coetzer says, it is important to ‘Get the balance right”, by sparing no effort in implementing each of the abovementioned elements to get the expected yield from fragmentation, and in the long run, improve life of mine.