Monday, April 21, 2014

Tech Talk - is coal that dirty?

So when was the last time, reading an article about the coal industry, that you saw a photograph of the land after the mine has closed, and the site reclaimed? Or, in talking about an oil or gas rig, how many times do you see the relatively small footprint at the site, once the rigs have left, and the site is reclaimed so that all that is left is the production tree?

The fossil industry tends to be vilified at regular intervals with very few voices raised to murmur slight protest as to the picture painted of its evils. The Economist had an article this week which said, in part:
And coal would indeed be a boon, were it not for one small problem: it is devastatingly dirty. Mining, transport, storage and burning are fraught with mess, as well as danger. Deep mines put workers in intolerably filthy and dangerous conditions. But opencast mining, now the source of much of the world’s coal, rips away topsoil and gobbles water. Transporting coal brings a host of environmental problems.
Note that there is no comment about putting the topsoil back in place after the mine has passed, or re-establishing the land fertility. Laws passed in the 1970’s have ensured that the land reclamation is to a much higher standard than previously, and reclaimed land in Ohio, for example, is now harvested for hay and used for pasture. And it was possible to get 43 acres of recreational land filled with lakes full of fish etc for some $107,000 only a couple of years ago.


Figure 1. Reclaimed mine land that was for sale in Illinois (MidWest Energy News).

Now it is true that working underground will get you dirty – in the same way as it will if you are working in the tunnels of a subway system, or on a farm, not to mention repairing sewers – but unless it is the color of the dirt that leads to the discrimination – working in a job that can get you dirty has not, in the past, led to the disapprobation that one sees in papers such as the Economist these days.

The concept of working underground by itself cannot, surely be something of concern. There are all sorts of buildings that have been built underground – either in regions where the site was first an active mine which then converted into offices, warehouses and storage facilities, or where the plan, from the beginning was to mine the space for a specific purpose (whether a subway line, an underground school or public baths or other useful place). For example, consider Springfield Underground which I first visited over four decades ago, and which can run up to 100 ft below the surface, although there are entries where trains and trucks can have access.
At 2.4 million square feet, Springfield Underground continues to grow; we have ample space available for your unique application. While we can accommodate all sorts of businesses, Springfield Underground is home to warehousing, laboratories, food storage, records storage and data centers. Our location is convenient to railways and highways – which makes us ideal for distribution centers and manufacturers.



Figure 2. Cutaway showing the location of available space at Springfield Underground (Springfield Underground)

By utilizing the space between pillars (shown in white against the blue available space) and building temporary walls work spaces of thousands of square feet are located underground where they are safe from tornadoes, which are a hazard for the state, at a constant temperature and in relative quiet and security.

Similarly there are facilities under downtown Kansas City and in a number of other locations around the country.

“Intolerably filthy and dangerous” – well that dates the information that the writer is basing this on. Of course there are the images and stories of the past:


Figure 3. The Penitent by Hildebrand

When I was young I lay on my side and worked with a pick and shovel in low coal, not that much different from the conditions shown in Anthony Burton’s “The Miners.”


Figure 4. Mining in Low Coal at Condering Colliery. (The Miners)

But that was over 50 years ago, when Britain still desperately needed the coal to fuel its restoration and modernization, and where there was also a provision to keep mines open to help with employment.

Now those narrow seams are largely not economic to mine (though there are ways) and modern coal mines use large mechanized methods to remove the coal, often remotely from the work force. But the image remains.

Increasingly mines are much safer, there is a fair amount of white stone dust on the walls so that, as well as being better lit, it is also just a brighter place to be.


Figure 5. A modern longwall production face (Maple Creek via West Virginia University )

While, in the unregulated mines of the past there were death rates of up to 1,500 or more in the United States (at one time explosions underground could kill all the miners underground at the time of the explosion, and this could add up to more than 200) there were 19 miners killed in 2012. And while one death is too many there are sadly other industries that have a worse record.

According to Forbes, the ten most dangerous jobs in 2012 were:
1. Logging workers

2. Fishers and related fishing workers

3. Aircraft pilot and flight engineers

4. Roofers

5. Structural iron and steel workers

6. Refuse and recyclable material collectors

7. Electrical power-line installers and repairers

 8. Drivers/sales workers and truck drivers

9. Farmers, ranchers, and other agricultural managers

10. Construction laborers

Mining didn’t even make the list, nor of the more extended list of the 15 most dangerous jobs, as listed by AOL.

Sadly the industry has been stereotyped with an antiquated, and largely out of date set of images. (Though admittedly in parts of Asia particularly the low cost of labor and the need for both jobs and fuel can still lead to the odd dismal picture, yet even there, as regulations set in the picture is improving by the year).

One has to look no further than to the photographs of power stations that use coal to see the evidence of this bias. The only visible vapors that leave a modern plant are the steam clouds and yet in paper after paper the photographer has maneuvered so that, with the sun behind the steam, it looks grey or black.

These distortions are having less and less impact, as the real long-term need for coal is clearly evident, but it just makes the debates less honest. Unfortunately the image of underground workers are too often associated with the Trolls and Orcs of Tolkien's Middle Earth in contrast to the desired world where we see the contrast to the idyllic but unrealistic dream of us all living in the Shire in bucolic joy for ever.

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Saturday, April 19, 2014

Waterjetting 20b - cutting slots in coal

There are several ways in which a high-pressure waterjet can be used to interact with a surface or material. It can be aimed to make a high-precision cut into or through a material, it can be used to clean a surface, or it can be used to bulk remove material – to name but three applications. At the moment, in these posts, we are concentrating on the third of these, and last time I mentioned that, if working with soft material, such as clay or soil, that there was an advantage to using two simultaneous jets cutting over a surface, to improve the efficiency of material removal by a factor of perhaps more than ten-fold.

I want to revisit that topic this week, and stepping for a moment away from soil and into coal, which is a harder material, I want to illustrate that the point (of concurrent dual jet use) is still valid but there is a wrinkle, if you are cutting along the edge of an advancing mining machine.

Cutting coal with water jets is not new. But I am going to skip that historical review today, and rather continue on the theme of dual-jet use. When I was first taught to mine coal, there had not been a huge amount of new technology in the industry – and for that matter there still has not been the need for much advanced sophistication where the basic ideas still work.

If you are going to break a material from the solid, it really helps to have a second free surface (as well as the face that you are attacking through). Thus when miners used to work the coal they would first undercut the coal seam using a pick to swing across the surface ad successively chip out a strip of coal about a couple of inches wide at the bottom of the seam, and going back as far as they could reach (about two to three feet). The pattern that this leaves isn’t usually seen in coal mines (since they move on) but I have seen it in the salt mines of Wielicza, the underground rooms in the castle in Naples, and in the old workings of the quarries around Bath in the UK.


Figure 1. Grooved wall at Wielicza salt mine (Wielicza Salt Mine ) The grooves are formed by the successive swings of the pick in the cut that incrementally chip a deeper groove into and along the back of the slot.

Of course cutting the slot in thinner seam coal mines was a little less comfortable (this from the days when smoking was yet to be banned in mines).

Figure 2. Miner “corving” at Seaton Delaval mine (Beamish Collection)

When mechanized machines were first developed for use underground, it was logical to begin with a machine that would cut this slot (the most arduous of mining labor) and replace the miner. To do this the machine developed was, to a very large extent, a variation of what you would think of as a chain saw. Driven by either compressed air or electricity, a long cutter bar would (like the chain saw) drag the cutters along a path (in the mining case perhaps six feet deep) that would create the slot required as a second free surface into which to break down the coal. (You learn very early in the game that a slot less than about two inches high is fairly useless, since the pressure of the overlying ground will just squeeze too narrow a slot closed, and the effort to cut the slot is wasted.)

Once that slot has been made along the perhaps 200-yard long face, then small holes were drilled, at perhaps 4 – 6 ft intervals in the middle of the face, sticks of explosive were placed in those holes, and, at the end of the shift the explosive was fired, breaking down the coal into the immediately surrounding area, and ready for the coaling shift to come on and shovel the coal (in 15 yard intervals per miner) onto the conveyor. (My job at one time).

One of the early advances in mining machines was the Meco-Moore, a machine that cut a slot not only under the coal, but also at the top and back of the seam.


Figure 3. Meco-Moore Mining Machine

This worked fairly well as a concept, but the small cross conveyor that was put on the machine to move the coal from the back of the cut to the conveyor had been adapted from a farm conveyor, and coal is a lot heavier and more aggressive than wheat. As a result the conveyor, and hence the machine, was always breaking down, and so it was replaced with shearers and plows, and the world moved on.

But shearers generate a lot of dust and sparks from the picks that rotate through the coal and adjacent rock, and occasionally hit sandstone. This led to explosions that killed many miners, and so, in the early 1970’s we were asked to develop a new method of mining. The logical thought was to build on the success of the Meco-Moore as a slot cutting tool, and add a plow shape to move the central volume of coal over to the conveyor. Jets would replace the cutter bars at the top, back and bottom of the seam, as a way of freeing the central block.


Figure 4. Original concept for the Hydrominer

We quickly found that using a single jet to cut a slot in coal did not help as much as we had expected. If we cut it horizontally then, as I explained above, the slot would close before it could be effectively used. And if it were cut vertically then the movement of the machine forward meant that every cut had to start afresh and could not take advantage of the previous pass to cut deeper.

And so we came to the idea of using two adjacent jets to cut into the coal at the same time, spacing the jets about an inch apart, and, in this way, removing the rib of coal with the slot cutting, to give a passage into which the nozzle holder, and plow blade edge could advance.

But if the two jets were parallel then the forward movement of the nozzles during each pass would mean that the second oscillating pass would be cutting fresh coal along its length and thus the depth of cut achieved would be only a couple of inches.

So we (Clark Barker, Marian Mazurkiewicz and I) decided to put the two orifices one above the other in a single nozzle block, with the jets pointing out at about fifteen degrees to the line of advance, but divergent from one another.


Figure 5. One versus two jet arrangement

In this way the jets cut a slot about two-inches wide, but as the nozzle moved into this slot it moved into an air space, so that when the jets made the second pass along the surface they did not hit coal until the back end of the previous cut. Within a few passes the two jets were cutting over a foot ahead of the plow face, instead of a couple of inches. This additional leverage from the wedge head of the plow as it entered the cut now meant that the force on the plow was dramatically reduced, and the machine could plow off a strip of coal some 2-3 ft deep and perhaps 6 ft high at rates of between 10 and 20 ft a minute. Given that the jets infused the coal as they cut it, virtually eliminating coal dust from the air, and there are no sparks since cutting occurs by water, under water, so the technique is safer.


Figure 6. Slot cut by the two jet system (about 2 inches wide) and the leverage this gives in breaking off large pieces of coal shown in a surface test.

Unfortunately the world market at the time was only about ten machines a year, and so the design was dropped (after an underground test) – but that is another story.

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Wednesday, April 16, 2014

Tech Talk - Of production stability, peaks and the future

Jeffrey Brown (Westexas from TOD) is quoted extensively in Kurt Cobb’s recent piece that points out that global crude production has pretty reasonably stayed constant at between 64 and 67 mbd since 2005. (H/t Nate Hagens). While there has been a total increase in the total refined products side of the house (with the total number floating around 90 mbd) this includes a number of different sources that, within generally defined standards, are not considered crude. The four main culprits that he lists are biofuels, natural gas plant liquids (NGLs), lease condensate and refinery gains. He makes a good point.


Figure 1. Crude oil production alone over the past decade (Kurt Cobb)

I can remember that it was some years ago, when looking at the OPEC reports on production, that I suddenly realized that the projected increases in NGL production made a significant difference in the overall volumes that they were producing. (It is anticipated to average 5.95 mbd in 2014). Back in 2001 OPEC just defined the fluid as natural gas liquids, but went through significant revisions of numbers in 2002 and in March 2004 redefined the volume counted as “OPEC natural gas liquids and non-conventional oils”.


Figure 2. NGL and unconventional oil production by OPEC (OPEC MOMR )

Over the past decade volumes have almost doubled. In the United States, with the increased development of the shale gases, production has also increased.


Figure 3. Increase in production of NGL in the United States (EIA )

The price obtained for these fluids, however, falls below that of conventional gasoline. For example:


Figure 4. Relative prices of NGL fuels relative to crude and gasoline. (EIA)

The EIA is reporting a continued growth in US production:
Altogether, in the Bakken, Niobrara, Permian, and Eagle Ford, oil production is expected to increase by 70,000 bbl/d in May 2014. The monthly growth rate is 3,000 bbl/d more than in April 2014 due to solid gains in Permian rig count and continuous rig productivity gains across the regions. While the DPR does not forecast weather impact, the spring thaw season has officially started in the Bakken region and may disrupt some drilling activity between now and June.
These additional resources take on an increasing importance as world demand is anticipated to increase another 1.14 mbd this year, slightly up on this year’s figure. This gain in demand was largely offset by increased production from the Americas, though OPEC note that overall global suppliy decreased last month to average 90.63 mbd but is expected to reach peak demand in the fall, at 92.24 mbd.

Looking at the supply side for this year, and bearing in mind that gains must more than offset lost production if the total increase in supply OPEC are projecting an overall gain in supply of 1.34 mbd, largely to come from outside of OPEC. This is expected to come from the OECD Americas (the USA, Canada and Mexico) group, while the increased production from countries such as those of the Former Soviet Union is expected, to rise by 150 kbd or less.

There has been relatively little change in the estimates of where the increases in North American production are anticipated to come. By the end of the year US production is expected to reach 12.45 mbd by the last quarter of the year. As OPEC noted:
Based on the US Energy Information Administration (EIA)’s monthly oil production report for January, regular crude oil output registered at 4.93 mb/d, tight oil production increased to 3 mb/d, NGLs output reached 2.64 mb/d and biofuels and other non- conventional oils recorded the highest output at 1.22 mb/d. The use of energy from biomass resources in the United States grew by more than 60% over the decade between 2002 and 2013 — primarily through increased use of biofuels like ethanol and biodiesel which are produced from biomass. According to the EIA, biomass accounted for about half of all renewable energy consumed in 2013 and 5% of total US energy consumed.
This month the OPEC MOMR focused on increased production from the Gulf of Mexico, with anticipated gains from the Olympus project at Mars B.

The total gain in production from the Gulf is currently anticipated to increase, this year alone, to perhaps 1.55 mbd, and to pass the previous record Gulf production of 1.8 mbd by 2016. In addition the Cardamom project is expected to add 50 kbd to the Olympus figure, and the start of oil production from Phase 3 of the Na Kika field is expected to add an additional 40 kbd to the 130 kbd which Na Kika is currently producing. However Gulf wells have a habit of going south a little earlier than predicted and I have borrowed the following graph from Ron Patterson which illustrates the cumulative fate of the combined Atlantis, Thunder Horse, Tahiti and Blind Faith fields.


Figure 5. Changes in production from major Gulf of Mexico fields over time (Ron Patterson )

When this is combined with Dennis Coyle’s prediction that the Eagle Ford field will peak in 2015, at 1.4 mbd, with a declining rate of production increase as one reaches that peak. Similarly the number of wells that can continue to be drilled in North Dakota in the sweeter counties of the state are limited, and beyond that there is a concern (which I have expressed before, and which others have explained much better than I) that as the estimates of production fall in the less successful regions of the state that it will become harder to raise the capital for the new wells needed to sustain and increase production.

That being said, I am beginning to suspect that this may be the year that the OPEC estimates for US production may get a bit ahead of what actually is produced. And if that is the case, then that means that the following two years will become even more interesting as the nations of the world start to realize that yes, there is a peak. Which might mean that the coal resurrection might be greater than I currently anticipate, but perhaps I will have more on that next time.

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Wednesday, April 9, 2014

Waterjetting 20a - Making holes in soil

There are two problems that often arise when applying waterjets to a soil-like material. The first of these is that the water can spread into the surrounding soil around the hole being excavated so that it loses its strength and can collapse into the hole. (This can be used to advantage in some cases.) This is a particular problem when excavating trenches, where the hole has to be as small as possible, yet the sides have to be stable so that work can be done at the bottom. The other is that, once the soil is loosened it has to be picked up and moved, and a way has to be found to be sure that the particles don’t settle out before they should.


Figure 1. Three consecutive frames from a video record of a jet firing into glass beads behind a glass wall. The framing rate was 30 fps.

In the sequence of frames shown above the jet is seen to first penetrate down through the beads (which were simulating soil, being easier to handle and see through), and then when it reaches about a nine inch depth it stops penetrating and starts to widen and fill the hole, which until the is relatively open. Note that at this stage there is no ejected material from the hole and very little penetration of the water outside the line of the hole. The penetration stops when the water no longer has the energy to push the particles aside, and continue to penetrate. (The test was at relatively low pressure to keep the penetration small enough to remain inside the box). Note also that the hole is largely hollow at this time.

If the jet is allowed to continue to play on the surface, the water will now penetrate into the material on either side. This can be better seen if the fluid color is changed to black by adding fine carbon particles to the water. The pressure was further lowered (to 100 psi) to keep the jet penetration down to below three inches, and in this case the jet was a fan shape to encourage the spread, rather than being projected through a round orifice.


Figure 2. Video frame taken as a waterjet laced with fine carbon penetrates into glass beads, note that the carbon starts to be carried into the surrounding material, and that again, in this short time interval there is very little material being ejected from around the hole.

In passing it might be noted that this is a relatively effective and simple way to inject remedial chemicals into layers of clay and soil that could contain undesirable chemicals (such as PCBs) but where going in to remove the contaminant might be difficult and cause other problems. This could occur if the contaminated layer is now covered with more material, and trying to dig the contaminated material out would cause it to disperse into a stream, river or bay where the problem has been found to lie.

But if we want to remove the soil, then the process, as it stands with using a single jet, is fairly inefficient. The water, at this pressure, is cutting into the soil, making a hole, penetrating into the soil around the hole, but not much is being moved. Again that could be an advantage.

Those who play golf know that good maintenance requires that golf greens need to be aerated at regular intervals to keep the grass healthy. At the same time, pulling plugs of material out of the green is disruptive, and conventional mechanical tools will still make a bit of a mess, and take some time. On the other hand Toro has developed and improved a tool – the Toro Hydroject – which has a series of jets that are spaced at adjustable intervals (but typically around 3 inches) along a distribution manifold, so that when the jets pulse they drive holes down into the soil, with no surface spillage of soil. And this can be done at walking speed – between foursomes, and without disrupting play.


Figure 3. Toro aerator at work. (After Toro )

The tool is also effective in poking holes under pools of water to speed drainage. The most effective pressures vary for different soil types and conditions, but are typically in the low thousands of psi, with penetration depths of up to eight inches. (They are also a potential tool for finding land mines, but that is another story).


Figure 4. Cut through a hole jetted into soil (turned on its side for convenience) (Toro)

Yet these applications again illustrate that the tool might be more difficult to use, where the main purpose is to remove the soil, and where a sequence of passes of a jet over the surface won’t potentially move much material.

The answer to this problem is to use more than one jet at once, and to place them at some distance apart, depending on the soil and jet parameters this might be more than an inch or two. What now happens is that the resistance of the soil is removed when it the jets pass along either side of the intervening rib at the same time. This very rapidly liquefies the rib in the middle, and it is removed as the jets cut past.

This can be seen where, for example, two jets simultaneously traverse over a clay bed. When only one jet was used it cut only a thin slice into the clay, with little material removed.


Figure 5. Single consecutive cuts into clay with a water jet that also contains kaolin so as to show where the cuts were made. (Note that even where the cuts are close together there is no removal of the ribs between cuts.)


Figure 6. Material removed when two jets cut side-by-side into clay. Note that all the intervening clay between the jets has been removed, to a depth of four inches.

The contrast between the two figures shows that by changing the way in which the jets cut into the material (concurrently rather than consecutively) up to ten times or more material can be removed from the surface for the same amount of input energy.


Figure 7. Slot cut in the ground by a combination of jets acting together as a head was moved through the ground (Halliburton - the Soil Saw)

This also works with some rock types, and I will discuss how we used it to design a machine for mining coal in a later post, but it is not the end of the story in developing the soil cutting aspect. The problem that can then arise comes from the type of soil that is being cut, and the distance between the jets. As the soil becomes more coherent (clay laden) the jets need to be brought a little further together (and the more sandy the soil, the further apart they can be.) But if the jets don’t have enough time to totally break up the rib of material into particles (controlled by how fast the jets are being moved over the surface and the relative depth of cut) then the pieces may come out in lumps of varying size and shape. These are more difficult to break up, once they break away from the solid.

The alternative is to move the jets relatively rapidly over the surface. This shortens the depth of the soil that is being moved at one time, but if, for example, the jets are being spun around an axis inside a shroud connected to a vacuum system, then the particle sizes can be controlled to fit within the vacuum line, and the depth of cut is small enough to hold the partial vacuum around the edge of the shroud to make sure that all the particles and water are removed and the walls are kept dry enough to remain stable. But, again that brings us into hydro-demolition and I’ll cover more of this in a later post.

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Monday, April 7, 2014

Tech Talk - from 1491 to China, coal, smog and CCS

I have written about my curiosity about the condition of Native Americans at the time that Europeans arrived in the Americas in the past, and so, when I came across Charles Mann’s “1491” at the Brookline Booksmith the other day, I bought a copy. It tells a fascinating story of the developments of agriculture and civilization, largely in South and Central America perhaps pre-dating the time around 10,000 years ago that the first cities were developing in Mesopotamia. He tells, with reference to considerable evidence, of the changing understanding of the state of society, and how it developed pre-Columbus. And if you thought the debate over climate change was rough, apparently that over the changing understanding of such civilizations is at least as intense, although confined to a smaller group.

Conventional theories are that Native Americans crossed over the Bering Straits from Siberia while the land was above water some ten to fifteen thousand years ago. However the discovery of remains at Monte Verde in Chile, with a site that dates back over 13,000 years and with other sites that may date to considerably earlier has thrown this all into debate and controversy – which the book explains in some detail. (It was published in a second edition in 2011, since when DNA tests of skull parts from the Botocudo peoples of Brazil have shown some Polynesian markers suggesting a possible sea route for the first Americans.) I am looking forward to reading the chapter that covers Cahokia.

This is a long introduction to explaining why I was drawn to the cover story in the April Wired that the book's author, Charles Mann, has written on the Future of Coal. It is a fairly rational review of ongoing developments in China to find ways of easing their air pollution problems, while continuing to rely on coal to power the ongoing industrial changes in their society. For as he notes,
Nowhere is the preeminence of coal more apparent than in the planet’s fastest-growing, most populous region: Asia, especially China. In the past few decades, China has lifted several hundred million people out of destitution—arguably history’s biggest, fastest rise in human well-being. That advance couldn’t have happened without industrialization, and that industrialization couldn’t have happened without coal. More than three-quarters of China’s electricity comes from coal, including the power for the giant electronic plants where iPhones are assembled. More coal goes to heating millions of homes, to smelting steel (China produces nearly half the world’s steel), and to baking limestone to make cement (China provides almost half the world’s cement). In its frantic quest to develop, China burns almost as much coal as the rest of the world put together—a fact that makes climatologists shudder.

. . . . . . “Coal is too low-cost, too plentiful, and too available from reliable sources to be replaced,” says fuel analyst John Dean, president of the JD Energy consulting firm. “China is putting in solar and wind power at a tremendous pace, but it will have to use more and more coal just to keep up with rising demand.”

The article then goes on to discuss the facility at Tianjin, where GreenGen is developing a Carbon Capture and Sequestration (CCS) plant. The first phase of the plant was inaugurated in December 2012, and the site is now in Phase 3 construction to develop a 400 MW demonstration IGCC power station.

In the WIRED article, however, lies the sentence “Conceptually speaking, CCS is simple: Industries burn just as much coal as before but remove all the pollutants. “ However, later in the piece this is qualified since one of the problems with the technology is that there is a significant (up to 40%) increase in the amount of power that the station must generate to provide that now needed to capture, liquefy and dispose of the carbon dioxide (by underground injection). Thus the plant burns significantly more coal, for the same effective power supply into the grid. This is one of the reasons that the DOE has concluded that the costs of such a plant will increase electricity costs by 70-80%, making it potentially too expensive. Interestingly that considerable increase in cost is, in part, because power generation using coal is currently relatively inexpensive.

Reading the story in WIRED made me realize that I must be quite a bit older than Charles Mann. Being raised in the North of England in the years after the Second World War I can remember when the UK was in much the same state as China is now, with the need for as much coal as possible to rebuild the nation’s industry and power the restoration of the economy. As a result the UK had vicious smogs when the air pollution mixed with a fog to create a condition when I can remember not being able to see the hand at the end of my arm, in the middle of the day in Leeds in 1962. The Great London Smog of 1952 was reported to have killed more than 4,000 people and severely affected the health of many others. The 1962 smog killed over 750 Londoners and the pollution from burning coal had long since turned most of the buildings in the cities of Britain into black edifices, with the original stone crusted with soot. I can remember that in the mining villages of the North the windows and steps were washed and “holystoned” every week to minimize the soot, and curtains and windows were constantly washed to remove the residue.

Two major acts were passed by the British Government, the Clean Air Acts of 1956 and 1968. While the advent of North Sea oil and gas removed the need for homes to burn coal in open fires (which I did until I left the UK in 1968) coal has continued to power the island (31% of power is still generated by coal) but the air pollution that contributed to those smogs is gone. The buildings in the major cities have been cleaned and brought back to the golden sandstone, or white limestone finishes that they had when initially built and the dark clouds that are shown issuing from power stations only occur when the photographer puts the steam emission between his camera and the sun.

The same change has occurred across Europe and in the United States (see photographs of Pittsburgh in 1940) - laws were passed, natural gas played a larger part in domestic energy supply, and the air cleared away.

It is likely that China will be able to achieve the same changes, as they increasingly import natural gas (perhaps from Russia, certainly from Turkmenistan) and provided they impose the same standards for air quality as are found in our power plants, then the air can be cleaned up. In this way the more than a million premature deaths that air pollution is currently causing (according to the article) can be ameliorated, perhaps at a lesser cost than the CCS technology, which is still struggling to provide meaningful demonstrations of its effectiveness. And China has to do something for, as the article continues to emphasize:
More important from China’s perspective, more than one-quarter of its citizens still live on less than $2 a day. These people—more than 350 million men, women, and children, an entire United States of destitution—want schools and sewers, warm homes and paved highways, things that people elsewhere enjoy without reflection. China can’t provide enough energy to make and maintain these things with oil or natural gas: The nation has little of either and not much incentive to import them at great cost. (Asian natural gas prices are roughly five times higher than US prices.) Nor can solar, wind, or nuclear fill China’s needs, even though it is deploying all three faster than any other country. Meanwhile, it has the third-biggest coal reserves in the world.

China, like most of the rest of the world, “pretty much has to use coal,” says Dean, the fuel analyst. “Or, I guess, leave people in the dark.”
And in this view of the future, China is not alone.

Good article (and good book)!

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Sunday, April 6, 2014

Waterjetting 19d - waterjets and material removal

When miners first began to use water as a means of moving soil and ore from valuable deposits at, or near the surface, stream flow, or the energy from stored volumes of water was the main source of the power used. However, at these low pressures it was necessary to use large volumes of water (often in flows of over a thousand gallons a minute) to move the material. At the same time, even at these large flow volumes, the flow has to be confined in order to ensure that there is enough water around the particles to keep them in suspension. There is also a certain amount of turbulence required in this flow to retain the suspension and to stop the particles from settling out before the riffles where the gold or other valuable minerals can be collected.

As pressure is increased these jets can be increasingly productive, and can be used for a variety of functions, including the rapid removal of soil. Raising the pressure allows the tool to be used in mining soft rock. As an example there is a layer of relatively soft sandstone that lies in a roughly horizontal layer and appears along the banks of the Mississippi river and can be found, for example, under Minneapolis. There is a sand mine that lies along the banks of the river, that has a high-grade sand that can be used for making glass, but which also has a vein within it that has larger grains that can be used in the fracking stage of increasing oilwell production. However, with conventional mining (using blasting) it was not economic to screen the sand after it had been mixed during mining. The Bureau of Mines of the time (since closed) tried some experiments to see if a waterjet could be used to “high-grade” the sand, mining the larger layer first, and then that surrounding it to let machines and men progress further (and also to produce the sand for glass making).


Figure 1. Bureau of Mines experiment washing out sandstone, with 4,000 psi water and cutting about 9 ft. deep. Note the yellow color of the water as the sand settles out but the clay contaminant is suspended in the water and washed away.

The experiment, carried out by Dr. George Savanick’s team, was successful, and had the unexpected advantage, since the grains were all separated, of stripping the small amount of clay contained in the sandstone and carrying it away with the water, while leaving the sand on the floor, where it had to be picked up mechanically.

The use of pressurized water is used both to mine sand, and also, in Cornwall, for example, in the mining of clay, although the pressure and volumes needed are a function of the quality and amount of weathering that the clay has seen.


Figure 2. Mining clay in Cornwall (Pathe video here)

Engineers have even accelerated the movement of landslides, using clay mine pumps, in order to move the soil away faster and allow the slide to be remediated. At Dawlish in the UK, for example, railway engineers have added water under pressure to remove the sliding soil as a slurry, making clean-up faster, safer and less costly.


Figure 3. Moving soil in a landslide that has covered the railway line at the bottom of the slope, Dawlish UK March 2014. (The Packet)

A jet was also used from the bottom of the slide to liquefy the soil, which then flowed through the railway path and into the sea.


Figure 4. Removing the soil from the landslide from above the railway. (From a video at The Packet)

As a comment, for those who watch the video that the above picture was taken from, the jet cuts much more effectively closer to the nozzle, and had they used it to undercut the bank they could slurry the soil lower down, and have removed the material a bit faster than dispersing most of the jet energy in the air as they tried to reach the back of the slope. (If they had undercut the bank then the soil would have slid down towards them shortening the reach and speeding the process).

During the Second World War engineers also used water jets to uncover land mines that had been planted on beaches along the coast. (video from Pathe here ).

However the control of the water, and debris, can quite quickly become a problem, and containing the water and keeping the soil/sand particles suspended in it requires more preparation. As an illustration the civil engineers who work under Minneapolis are aware of the benefits of using higher pressure waterjet streams in driving tunnels (and occasionally rooms) under the city. For example, in driving a sewer tunnel (the St Anthony Park Storm Sewer extension) the engineers set up an extensive train behind the tunnel face, so that the resulting slurry could be pumped out of the tunnel.


Figure 5. Train behind the tunnel face, required to supply the jets and to pump the slurry from the excavation (after Nelson*)

The tunnels can be driven by two main jet operators at speeds of up to 120 ft per day () with a third jet being used to break the larger pieces down to slurry so that it can be pumped down the tunnel to the river, where it is barged and sold as glass-making sand.


Figure 6. Driving the storm sewer tunnel under Minneapolis. Two operators are carving the face into small pieces and the third is slurrying the sand (after Nelson*)

By feeding the sand and water into a channel cut into the floor of the tunnel it was possible to confine it, so that the blocks could be broken up more easily, and this also then provided a catchment for the intake to the slurry pumps.

The tunnels were pre-cut along the profile, so that the arch girders that provided support could be slid into place with the central core of rock still there to support them. This made the support easier to install, and provided immediate support of the working area ahead of the place where the miners were working.

(That ability to use waterjets to penetrate ahead of the tunnel and allow a support to be installed before the main core of the tunnel rock is removed has since been improved, and in the Advanced Austrian Tunneling Method high pressure jets drill out cylindrical bores along the profile ahead of the tunnel, which are filled with a grout that can be generated partially using the surrounding material as the holes are drilled. But I will talk about the use of cement mixed with the jets in a later post).

*Nelson C. Tunneling under Minneapolis, Water jet Workshop, Rolla, MO 1975.

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Friday, April 4, 2014

Iceland becomes a little more active

So I just glanced at the Iceland Earthquake map again tonight, and it has become a little more active than in recent times.


Recent quakes in Iceland (Iceland Met Office)

As a reminder:The colors of the circles show the time since the earthquakes occured (the numbers below the color palette represent hours). The latest earthquakes are shown in red and the dark blue ones occurred over 24 hours ago. The earthquakes stay blue until 48 hours have elapsed since their occurrence, then they disappear. Earthquakes bigger than M3 (on the Richter scale) are represented with green stars that turn yellow after 24 hours.

No more - as yet!

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