Tuesday, December 10, 2013

Tech Talk - a gentle cough for Simon Michaux

In response to a post I wrote a couple of weeks ago Marty suggested that I watch a video by Simon Michaux discussing peak mining. So I did.

A quick check through Linked In has Simon Michaux as a Mining Consultant in the Brisbane area, having been a Senior Research Fellow at the Julius Kruttschnitt Mineral Research Center (JKMRC) at the University of Queensland for 14 years. (I should mention I spent a sabbatical at the Mining Department at the University of Queensland in 1987).

In his presentation Simon discusses Sustainability in regard to the mining industry, pointing out that as the population rises and demand for minerals increases, that demand can only be met by mining leaner and deeper ores, once the shallow easy and cheap to mine deposits are gone. (A similar argument to that of peak oil, which he does talk about in his presentation as well as mentioning the predictions that we are nearly at Peak Coal).

I have a number of problems with his approach, and have discussed some of them in various posts over the past few years, but let me discuss them again as a rebuttal to his conclusion that the world is rapidly heading into disaster and the end of the Industrial Age as the costs to mine minerals and the difficulties in finding enough product make it impossible to continue our current trends.

Now it is true that back in the days when Europeans first came to the United States that the local tribes around the Great Lakes were mining pure copper strips and large slabs and nuggets could be found. White Pine Copper Mine in Michigan was still finding these when I visited there some decades ago, but they occurred in a relatively hard host rock and the deposit was going deeper and becoming more expensive and so the mine closed. Because of economies of scale it became cheaper to simply dig much lower grade ores out of the ground. He cites the example of Bingham Canyon where the mine now extracts copper from ores with less than 1% of disseminated copper, rather than the pure copper nuggets of former times. And he points out that as the ore is ground finer it requires more power.

Figure 1. Relationship between energy required to liberate minerals from ore by reducing the particle size, leading to higher energy demands. (Simon Michaux)

There are a couple of points that need to be raised here. The first is that digging ore (and coal) out of a surface mine is a relatively simple and comparatively inexpensive operation. It does not require large applications of exotic technology and the whole process of getting the ore from the solid to the point where the mineral is liberated is straightforward.

The reason that there are steel balls shown on the rhs of the above figure is that after the body of the ore is broken free with explosives the fragments are picked up in a large shovel and loaded into mine trucks that carry hundreds of tons at a time to the main plant where the ore is crushed in part by falling into long rotating drums filled with steel balls that break the rock into fine particles through impact and attrition. (A simplified modern version of pounding the rock fragments with hammers until it gets small enough to free the mineral). Simon makes the point that modern technology is now capable of breaking the ore down to 5 micron particle sizes to free the ore, but that this takes increasing amounts of energy (as shown above), and that hauling all the ore to the plant and crushing it all to this small particle size is leading to unsustainable energy costs – particularly as oil and other fuel prices are set to continuously rise in the future.

But here he makes a critical misjudgment, because his argument rests on the mining industry and the manufacturing industry remaining the same, and following conventional practices into the sunset. But this is unlikely to happen. Just as the increase in prices made it possible to develop hydrofracking of long horizontal wells and thereby develop the oil and gas in the otherwise uneconomic deposits of Dakota and Pennsylvania so technology can find alternate processes that will lower the costs for mining minerals.

For example it is not necessary that the trucks that haul the ore rely on diesel fuel produced from oilwells. Some mines have already switched to biodiesel, which has some advantageous properties for their operations. Other mines use electrical power to run their haulage and GE has demonstrated that diesel engines can run on a mixture of fine coal and water. The reason that countries such as the UK have migrated away from coal use has more to do with the availability of cheaper sources of alternate fuel and for political reasons rather than there being a lack of available coal. (Note that German use of coal for power is increasing as an example).

Secondly the use of ball mills for crushing all the ore is simple but not necessarily all that efficient. I have noted that a more efficient process, wherein ore can be reduced in one step from 1 cm size to 5 micron size, using cavitation, is quite easy to build and operate.

The use of hydroexcavation and instant ore comminution using cavitation means that the ore can be separated into mineral and waste at the mining machine, and (because of the way the process works) both fragments of the ore are broken at the natural grain size, so that there is no need for overgrinding, and the fragmentation is by tensile fracture growth instead of compressive crushing, saving energy. By separating the mineral at the face, and leaving the waste in larger fragment sizes the waste can be relocated close to the mining face, potentially being used to provide support in regions that have been mined out. Only the mineral needs to be moved from the face to the plant – cutting energy costs dramatically.

Once the mineral is available as a fine particle it becomes easier to treat it and process it into the required feedstock which, as 3D Printer technology migrates into the construction of larger and more useful items from metals and more advanced materials so the waste involved in older conventional practice will be minimized and costs in financial and material items contained.

The future is likely therefore to be much more exciting and positive than Simon Michaux foresees, though I do agree that it will become more sensible to mine landfills to reclaim minerals – but then we have been doing that for some time now. But no, we are not coming to the end of the Industrial Revolution, merely moving to a different phase.

1 comment:

  1. hi dave

    thanks much for the detailed and informative response to my query!

    Apologies for just coming across your response today.

    Given the cost of energy, I would imagine there probably remain some scaling issues as well as sunk investment issues before water-jetting/cavitation can begin to replace ball mills.