The mining industry is always looking for better and safer ways of using explosive technologies, but blasting still remains one of the most hazardous aspects of mining
Explosives and mining go way back. Even today, drilling and blasting are essential parts of the mining cycle – the principal methods of rock-breaking and production within the African mining industry, in fact.
Blasting, used in both open pit mining and underground mining, is the process of fracturing predetermined amounts of material by use of a carefully calculated amount of explosive. Blasting technologies and techniques lend themselves to steady development, in explosives, detonating and delaying techniques, and the like. There are several types of blasting design: bench blasting (including short-hole blasting and longhole bench blasting); ring drilling and blasting; crater or VCR blasting. If you don’t know what any of that means, it’s not important right now, but you probably shouldn’t try any kind of blasting operation until you do. Just a word of advice. In any case, from 9th century CE to the mid-1800s, black powder (gunpowder) was the only explosive available. The Industrial Revolution carried new discoveries in explosives and initiation technologies – now explosives come in a variety of types, and are used in a variety of ways in the mining industry (coal mines, incidentally, need special explosives, called permissible explosives, because it’s unwise to just go blasting all willy-billy in a coal seam). Blasting agents are high explosive agents (much like those used in military explosives, rather than the low explosives used in guns and firecrackers). The best known, naturally is dynamite, developed by Alfred Nobel (see Timeline below), a mixture of nitroglycerin and kieselguhr. ANFO (ammonium nitrate + fuel oils) is most often used for excavation.
Many companies (for example BME, AEL, Maxam.Sasol Dyno Nobel, Orica Mining Services) are involved in developing and supplying explosive technologies to the mining industry over the years, new chemical explosives have been devised – allowing for cheaper, more powerful, more controlled blasts.There have also been amazing developments in the computer simulations of blasts – allowing for a better understanding of how to employ emplosives in particular mining situations, and providing a measure of risk management. Even simple-seeming advances, like those in explosive emulsion pumps have helped improve power consumption and product life (locally led by the German pumps company Netzh Pump & Systems) can have a big effect on the way mines operate.
But perhaps the simplest and most effective improvements have come in the timing systems for explosive detonation. Electric detonation used to be all the rage, but it is hardly compatible with long range initiation due to voltage drop. Over the last decade (the first wireless system entered the market in 2000), systems have been devised to deal with this issue. Electronic delay detonators (EDDs) are prized for their accuracy – usually to the millisecond – and their flexibility of programming possibilities, especially as regards timing. Take, for example, BME’s new AXXIS system, a robust system for achieving a high degree of accuracy in blasting, which employs centralised programming to make timing easier and is often used by quarries for controlling vibration and air blast levels and limiting back damage. Shock tube detonators are another safe and useful explosive development – e.g. AEL’s environmentally-friendly third-generation detonators, with safety improvements including improved impact resistance, a reduction of primary explosives in the 200 milliseconds out-of-hole delay detonator and a significant reduction in lead compounds.
“I’m excited about using electronic detonators or shock tube initiators to improve the quality of timing of the blast, while also making blasting safer,” explains Dr Dedan Vogt, Strategic Research Manager at the CSIR Centre for Mining Innovation. “For surface blasting, the introduction of blast management systems by companies such as AEL can improve productivity and safety.”
Explosives experts are quick to point out that explosives are actually a lot safer than most people think. But that doesn’t mean they should not be handled with care. Blasting is still one of the more hazardous aspects of mining. Workers can be struck by rock, poisoned by fumes, and otherwise affected by improperly handled or faulty explosives.
“Safe use of explosives is all about training and following procedures and safety systems,” says Charles Hurly, Marketing Manager of BME. “There are various regulations laid done by the Explosives Act which advise exactly what is needed.”
That may be why the technology around explosive use is also improving. In some cases, the end result of some of these technologies may be to do away with the need for explosives altogether. There have been a number of breakthroughs in this regard since the 1960s including machines that extract coal from underground seams, hydraulic fracking for freeing natural gas from underground shale, and so on.
Gold mining hasn’t yet been changed by these developments. But the AngloGold Ashanti Technology and Innovation Consortium (AGATIC) partnership, created in 2010 with a number of capital goods manufacturers and research groups as members, hopes to do something about that. AGATIC has been working towards develop¬ing thermal breaking, hydro breaking, microwaves, laser drilling, and several other alternatives to the blasting way of doing things.
AGATIC aims to develop machines to replace mineworkers at the slope face, and eventually do away with the risks of blasting entirely. It’s a dream shared by the Council for Scientific and Industrial Research (CSIR), which has been working on a mining robot programme for several years. Led by researcher Jeremy Green, they hope to complete a prototype to replace blasting by 2018, – and by next year, to introduce a robot that merely improves on drilling-and-blasting methods. Unlike human miners, it won’t have to wait for hours for gases and dust to ventilate and seismicity to settle after blasting, and so could enter the drive and inspect it, giving miners a 3D representation of the area and examining rock looseness. The result: much less lost productivity – shorter inspection times, fewer missed rounds of blasting – and a lower risk of harm to a human inspector.
Another blasting-replacing technique is electro-breaking – sending a high-frequency alternating current of electricity through rock using electrodes. It’s an effective technique, but experts aren’t quite sure why yet. It could be related to what is within the specific rock and how these elements react to the alternating current. Or perhaps it’s something else entirely.
This article was originally published in the November 2012 edition of Mining Prospectus