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.

Tech Talk - Energy cost, additive engineering and cavitation

I paid $2.85 for a gallon of gasoline this weekend, at the gas station just up the road from our house, here in South Central Missouri. A couple of weeks ago while I was in the UK the price my brother paid was around $8.00 a gallon. The BBC calculator that I used to check the UK price tells me that I am paying $6.89 less per tank than the regional average here, and that were I to live in Italy my tank-full would have cost me $95 more, while it Venezuela it would have cost $43 less. (It cost $45 to fill my tank).

The low cost of fuel is one of the benefits from the increased crude oil production in North America, sustained as it is by the increase in production from Saudi Arabia to balance the global market losses from other countries around the world. Further the EIA explains the refineries are helped with this low price by the high demand for diesel and the premium that it has achieved – causing refineries to run at record levels to meet the demand, and producing, as a secondary product, more gasoline that is thus being marketed at the lower price. It is a situation that the EIA expects to continue for a while.

Figure 1. US refinery inputs (EIA TWIP Nov 6, 2013)

The relatively low price of fuel, here in the United States, particularly relative to Europe is starting to attract industries historically located abroad. The move to date is being led by those attracted by the cheap price of natural gas, particularly in the chemical industry. BASF, for example, cut the ribbon last week on a plant expansion in Vidalia, LA and just recently announced plans to expand its research facility in Beachwood, Ohio.

It was, however, another report on manufacturing that really caught my attention this week. It was the news that 3D Printer technology had advanced enough to now make a gun from metal parts. The process involved is somewhat more complicated than that used in earlier guns manufactured using this new generation of equipment. Earlier in the year a gun had been made from plastic parts and made some additional news when a version fired nine shots without falling apart. The evolution of the plastic gun is worth noting in that the first one reported was built from components printed with an $8,000 second-hand Stratasys Dimension SST 3D printer. And while it fired a shot successfully, the gun blew up on the second trial. The second gun, however, was made on a $1,725 Lulzbot A0-101 3D printer, that was available from Amazon, made by Aleph Objects and it survived firing nine rounds. For a variety of reasons the plastic gun contained some metal parts, but it marked the advent of this new technology. Prices for these replicator units are already down below $2,000 and they are limited, at present, to working with different types of thermoplastic. (But they can make, for example, shoes.)

The difference in being able to move to making parts from metal, particularly those that allow the repeated (over 600 times) firing of the gun is a very significant step forward. Thirty-four parts were made from stainless steel and Inconel 625 and then a grip was made from nylon, using a classic 1911 design.

Figure 2. The metal gun made by Solid Concepts (Solid Concepts )

It is the different metal part of this that is worth underlining. The components were made by laser-sintering (which simplistically means that they used a laser to melt tiny particles of metal so that they would fuse together to make the model). The machine that is used to do this, at the present time costs between $400,000 and $1,000,000. It also has power and other logistic needs that require it be run in a commercial, rather than residential environment.

But, as Sold Concepts notes:

Solid Concepts has been using metal sintering for some time now to successfully create parts for a wide array of products. The 1911 gun is well known and people can relate to it in respect to its power and need for precise components. This story is about how additive manufacturing can be used to produce real, accurate parts in your industry whether it’s aerospace, transportation, medical, energy, consumer products, etc.

The changes that this will make in industrial manufacturing, and in the global market for materials cannot be underestimated. At present parts are generally made by subtraction, taking large billets of material and milling and machining away all the un-needed bits, producing large volumes of scrap chips. None of that waste will be generated with this new process.

Chris Hechtl has already produced The Wandering Engineer” series of Science Fiction books, starting with New Dawn that uses the concept widely as one of the bases for the stories. (Worth a read just to get some idea of the scope of what is to come - though I am also enjoying the series, as the books are written).

It is going to change the way in which components are built, but it will also change the way in which minerals are processed once they are mined from the earth. It will be no longer necessary to cast metals into large ingots and then forge them down into smaller shapes. It is likely that, for many items in the near future that process will still be cheaper, but as time progresses and the costs of the process reduce (bear in mind that this is laser-based and remember how those costs have come down as lasers have become ubiquitous in society) that even large parts may be better made this way. Further it allows intricate melding of different materials to make products that are stronger and better suited to the need.

Thus the objective of mineral processing in the years to come will be aimed at making fine powders rather than going through all the steps to make the larger ingots. That will, in turn, impact earlier stages of processing, and, while I don’t normally discuss my own work in these posts, I would draw your attention to a recent post from October 31st, down below, which includes a video of a small piece of equipment virtually instantly breaking half-inch coal into 5-micron pieces, which can be done with a pressure washer from the local hardware store. It also works in breaking out minerals from their host rock.

The world indeed will change, and with those changes the power requirements of the future are also going to undergo drastic revision.

Waterjetting 14e - Cavitation and Comminution

In the last post on this subject I discussed how, by adjusting the back pressure in the relatively stationary fluid surrounding a high-speed jet of water, it is possible to intensify cavitation damage. The simple way to find the optimal value for the back pressure for a given jet pressure and size was, we found, to listen to the sound of the cavitation collapse, and by adjusting the back pressure tweek both the sound and range of the cavitation cloud surrounding the jet.

The damage that the cavitation would induce on samples of rock is a function of the time that the cloud plays on the surface. By slowly moving the sample under the nozzle, in a confined cell, different levels of damage could be achieved, based on the speed at which the sample moved.

Figure 1. Traversing specimen cell, with the front cover removed to show the sample in the holder.

When the sample was moved under the nozzle at 2-inches a minute, the cavitation cloud attacked the surface relatively uniformly, with only localized increases in damage. In Figure 2 the red lines mark the width of the cavitation cloud on impact, it then spreads and collapses over the surface to give the wider erosion path.

Figure 2. Traverse over the surface of a dolomite sample at 2-inches a minute. The red lines define the width of the jet. Note the additional depth of removal under the sample ID (15) where the ink chemical had slightly weakened the rock making it more susceptible to erosion.

As the speed of the sample movement is slowed, however, the cavitation attack starts to find weakness planes in the rock and preferentially begins to erode these. As these channels are formed so the jet will flow into them to escape from the following flow of water in the consequent jet flow. As the cloud moves into these narrower spaces, so the pressure increases, inducing more of the bubbles to collapse and thus intensifying the erosion attack along that weakness plane (Figure 3).

Figure 3. Traverse of a cavitating jet over dolomite at a speed of 0.5-inches per minute. Note how the jet is now eating into zones of weakness which are beginning to define pieces of rock that are then liberated as cracks grow all around them.

As the traverse speed is further reduced to 0.4-inches per minute the erosion pattern which is developing in Figure 2 becomes consistent under the full width of the cavitation cloud, and the intersection of developing cracks means that the rock is now being removed in larger pieces and the erosion rate suddenly increases significantly.

Figure 4. Effects of moving the cavitating jet over the rock at 0.4-inches per minute. The cavitation is now developing cracks in the rock that join and break out larger pieces of rock, to a depth of around 0.5 inches over the cloud width.

This ability to focus the jet attack on weaknesses in the rock structure can be useful if, for example, the rock under attack is a mineral ore. Because the ore is defined with weakness planes around the individual constituent grains of the minerals and host rock, at a slow traverse speed the cavitation cloud will preferentially attack those boundaries, in the process liberating the individual grains, and separating the rock into its constituent materials. This liberation can be achieved as the rock is being mined (we have demonstrated this in the lab) so that the valuable mineral can be separated from the waste rock at the mining machine. This means that the waste can be left, in a larger size range than is conventionally left after separation, at the mining site, and does not have to be transported to the surface and ground to powder in order to separate out the valuable minerals. The energy savings that this achieves can be potentially as high as 75% of the total energy currently used at the mine.

Where the mining breaks out the rock without achieving complete liberation a secondary process can be used where the particles of material are fed into a secondary tube, where the particles pass through a second cavitation cloud. The attack of the very small bubbles on the mineral particles is such that the fragments of ore are rapidly broken (comminuted) into much smaller sizes in a process which, because there are so many events occurring sequentially , can appear almost instantaneous.

Tests at Missouri University of Science and Technology, for example, have shown that 0.5-inch sized pieces of coal can be reduced to 5-micron size in a single step. There is a video attached to this post of one of these tests. Figure 5 shows the equipment, with the coal in the inner metal tube, while the surrounding space is filled with water under slight pressure. 

Figure 5. Equipment to comminute coal to 5-microns (The size of the feed coal can be seen in the plastic box on the right).

Water to the cell does not have to be at any great pressure. The test has been successfully run with the water fed from a pressure washer obtained from the local hardware store for less than $100.

Figure 5a. Early in the test the water flowing out of the inner tube is filled with fine particles of coal as the cavitation breaks the pieces down to the required size.

B) A short while later and the outer tube begins to fill with the fine material.

One of the advantages of coal at 5-microns is that it can be mixed with water in about a 50% slurry and fed into a diesel engine, which will then run. GE has tested a locomotive and shown that it is possible to run the engine on the mixture, should conventional diesel no longer be economically available.

The process also works when a harder rock, such as dolomite (a host for galena and other minerals) is placed in the inner tube. The cloud color in this case is white.

Figure 6. Using cavitation to crush dolomite. The original particle sizes are in the box on the left, the cloud of particles is at around 5-microns.

Gold Rush Alaska - a gentle cough about shaker tables

I do not normally yell at my TV, nor usually want to throw things at it. However I almost reached that point of reaction on Sunday. I had been told about the show “Gold Rush – Alaska” by a couple of folks in my old Department, including a graduate advisee, but had not thought to go and look for it. But setting up to exercise I ran through the channels and an episode had just started. So I watched it as I worked out. (And it did get me more exercised than usual). In this particular episode they were having problems with their Wave table. (Which looks as though it works in a similar way to a table of similar appearance called a Wilfey table, and which I have recently used, as I will show in a photo added to the bottom of this post).

It became very clear, early in the episode, that the folks running it had no clue as to what it was supposed to do, and after a demonstration (which I am not sure wasn’t faked for the camera) where it failed to separate gold from the material run through it, the table was shut down. So I want to explain in very simple detail how the table is supposed to work, and show a photo, albeit with lead rather than gold ore – but that was what we were looking at when I last ran it). This is not rocket science.


The table starts out as a flat surface, onto which a number of thin strips of wood are attached. (Modern ones are of molded plastic ) The strips taper a little as they move along the table. The table is mounted so that it can be tilted in two dimensions, what I will call down the table, and along the table. And for the explanation I am going to use sketches initially.

Schematic of the basic components of a Wifley table.

The crushed ore feeds onto the table in a slurry and water sprays along the top edge of the table are set to give enough fluid to allow the vibration of the table (caused by some sort of eccentric cam resting on the underside) to provide a partial buoyancy to the particles, as well as helping with separation. The combined action of the water flow and the vibration help to move the crushed material both down and along the table, until it hits the top bar (or riffle).

The vibrating action helps to lift the lighter and smaller particles so that they float over this riffle, but the denser valuable particles are not lifted enough. (Remember Archimedes) Instead these then move along the feed edge surface of the riffle and table. If the riffles are of reducing height along the table this means that at some point intermediate weight ores can be separated from the lightest, (which run almost straight down the table) since although initially confined they can lift over a lower barrier. They are also separated from the heaviest ore (gold or lead), which remains confined by the riffles and thus runs down the far end of the table. Smaller particles of the heavier material that get over the top riffle do not have as much water on the lower riffles, and thus become trapped and fed over to the collection stream at the end of the riffles, but lower down the table.



The adjustments to the table are made so that the slope is enough, and the water flow enough, so that the mineral to be collected does not have enough buoyancy from the water and table action to get over all the riffles. It therefore collects at the far end, while the waste material is carried over the riffles then down and off the table. If the table is tilted too steeply, or the flow of water is too high, then even the heaviest particles will be swept over the riffles. (Which was one of the things they wre doing wrong). On the other hand, as is noted below, gold is not a rich ore and so there will be a lot of material swept over the table for very few ounces of recovery.

That is the basic principle, and by more careful adjustment it is possible to separate a mixture of different minerals into separate streams, as I just mentioned, as the particle move across and down the table, and these can be collected at different points along the bottom of the table (ours has holes in the table that feed to collection buckets).

There are different forms of table, based on this initial concept. An initial Google search showed this one at an on-line tutoring site

There is a video of a table working here, and one that, as with the second illustration uses groves that the heavier ore can’t escape from, here using a gold sample.

At the end of writing this rant I did find the Web site where the table makers respond to the Gold Rush Alaska video. They comment (in part)

Mike happened to be up there at John Schnabel’s . . . . so the two of them went over to the Hoffman’s site. Mike adjusted the table, ran a sample that Dorsey had, and got a gold line. It was filmed and will hopefully be shown on the next episode.

here’s our answers to what they did wrong…..

They destabilized the table by taking the slab out of the ground and loading it onto a floor jack.

All the raising and lowering of the table was wrong. Once the material is screened properly, you find the correct height adjustment and leave it there. Dorsey almost had it running, and then it was sabotaged. (Ed note that was the first thing I noticed).

No classification – large flakes should have never even been on the table (according to Dorsey’s blog, it probably was not even on the table).

The wave table does not make gold, it recovers gold. . . . .From the onset, their desperation (and script acting) caused mistake after mistake. No professional miner would work this way. There’s definitely gold on this property, but 30 buckets of concentrate and only 2½ oz of gold total! Wrong area to work……

Sadly it is often shows such as this that lead folk to believe that technology is some form of black art, whereas with just a little more accuracy and demonstration it could have been shown to be a very valuable tool.

The ore that we were processing the other month was a lead ore, and the table was set up just to show that we had liberated the galena, so that it was not tuned to give the separation right on the edge of the riffles (I had too much dip along the table) but you can clearly see, in the photo below how the heaviests parts of the ore had been carried to the edge of the riffles, and the galena (the silver stream) is clearly separated from the rest of the minerals.



It has sadly been my experience that folk often spend large amounts of money on equipment (in my field usually pumps etc) but fail to focus their investment and knowledge on the critical aspect of the entire operation that determines whether or not it works. In my case this is the small nozzle at the end of the delivery line that controls the jet that comes from the pump, (which because it wears out is usually of a poor quality, because they are cheap) - in this case the entire operation was centered around the use of the table to achieve the final separation of the gold. But without that running properly the entire investment was threatened. (But then, as a thought, if it all worked properly maybe there wouldn't have been enough drama to justify the series - tsk, tsk, what a cynic!)

The other meaning of "Clean Coal", and related mineral preparation

There is a lot of talk about Clean Coal these days. The Federal Government are issuing, though DoE, a significant number of requests for proposal (RFP’s) seeking those ideas to improve the combustion and reduce the carbon dioxide emissions when coal is burned. Largely these are related to the combustion process itself and the consequent separation of the carbon dioxide, which is where there is a relatively large body of expertise within the Universities, and where progress is likely to be incremental, given that most of the technologies in place are relatively mature and well-known.

Of lesser importance, it would appear, are the pre-cursor parts of the coal cycle that prepare coal for combustion, or those post-combustion parts where the gas, after concentration, is to be sequestered. Part of this lack of interest, I suspect, comes from the lack of experience within the Government and the funding agencies in these areas. Thus there is no-one to speak for them when the funding pie is divided and money is allocated to the different processes seen to be contributing to solving the problems.

Yet in the end these are the parts of the process that will prove to have as great a contribution to the solution of the problems as any. Coal is inherently a dirty fuel – by which I mean that is it virtually impossible to go into a coal mine or operation where coal is being processed without the dust leaving a residue on your skin, requiring that you either wash or take a shower to become clean again. That dust is part of the coal structure – we used to call it fusain – and it is defined as

the only constituent in coal which blackens objects with which it comes in contact.

In that classification the other constituents are clarain, durain and vitrain.

But most coal isn’t found as just a mix of these four parts. Coal was formed as vegetation (including trees) collapsed into the mud, and other plants grew on top of it. Mud got into the layers between the plant remains, and occasionally local water floods would carry sand and other material in and over the plants. As the swamps sank, and the vegetation grew thicker the band of material thus had thin layers of other material interspersed with the coal itself. As the layer was buried beneath later sediments (deposition was largely during the Carboniferous era, some 300 million years ago, or roughly a little longer ago than the time it takes the Solar system to go once around the galaxy). it was compressed and while the vegetation turned, in the end, to coal the included beds became shale, and sandstone or limestone layers within it.

When coal was mined a century ago the miners filled tubs of coal that held roughly a ton, with each tub marked with the miner’s “token”. When the tub came to the surface it was judged by management and if it was felt that it contained too much rock, then the tub was not counted as part of the miner’s production for the day. Thus there was a reliance on the miner himself to make sure that the coal being “loaded out” was just coal and did not contain rock, or dirt as it became colloquially known.

As mining became more automated, the pick of an individual miner was replaced with the multitude of picks that are mounted on the rotating drums of most mining machines. These drums are alternately raised and lowered to mine out the full section of the coal, and they indiscriminately mine, break up and load onto shuttle cars, or conveyors, the resulting mixture of small coal with some waste rock. Now there is little control of the coal quality at the face (apart from making sure that little of the rock above and below the coal is also mined). The coal, as a result, comes to the surface with the contained dirt still in it, and in many parts of the world that is what is then sold to the customer.

However the rock contents don’t burn well, and the residue can fuse to form clinkers that clog furnaces and reduce firing efficiency. So as the market grows for the mine from local consumption to a larger market, pressure comes to bear to “clean” the coal by “washing” it. In a simple form this involves running the coal through a bath that contains fluid of a carefully selected density. Coal floats in that medium, while the rock settles to the bottom. And thus the two are separated and the washed coal can then be sold to the customer as something that will burn in a cleaner way.

So why write about this tonight, rather than holding it over for a technical talk on a Sunday? Well the problem comes down to this – in the past the job of cleaning up the minerals that came out of the ground – whether separating the coal from the waste, or getting the valuable mineral components out of the different ores and waste rock in which they are found was allocated, at most universities to the Mineral Preparation division, which often ended up as a sub-group of Metallurgy.

Skip forward a decade or two and now Metallurgy departments have been merged, often with Ceramics, into Mineral Engineering or Science, and it is these departments where some of the more exciting research is done on nano-materials and the components that go into the electronic circuits on which we all rely. These folk also work on materials such as those sought to improve the operational lifetime of existing and planned power plants. Hiring new faculty into these departments will usually bring on board faculty that work at these cutting edges of those areas, and the world makes considerable progress from their efforts. But in the process, since in many departments total faculty numbers remain fixed, this has come at the cost of not replacing those who are experts in the fields of Extractive Metallurgy. Nor has the field of Coal Preparation seen strong support, as other issues have claimed greater visibility and funding.

So now here we are – we need cleaner coal to be supplied to the power stations, so that it can reduce the burden of dealing with the combustion products. As the ores from which valuable minerals come become leaner (the richer veins having been mined) it becomes more important, as part of the economic operation of the mine, to get the most mineral for the least cost from the ore. (Mines have closed when they could not do this well).

Who will provide that knowledge? Who is funding the research to advance it? Sadly the answers in both cases are likely to be almost no-one. It is a critical part of the continuation of our industrial society, but, being neglected, it has lost its voice and champions.

Sadly it takes more than the stroke of the pen by the Administration to create or recreate that collection of experts and as the current generation now retire, we will all, in time, mourn in one way or another, their passing.