Thursday, March 28, 2013

OGPSS - future natural gas supplies and Cyprus

This post began as a view on the developments in Cyprus, and I am grateful to Gail for the suggestion, and it is my fault that it morphed a little from that simple original objective.

One of the problems that one faces in marketing natural gas is that there is so much of it coming onto the market that it makes it difficult to set a price for future production. Even when the fields and reserves are estimated to be large, having some confidence in the price that the gas will bring helps provide confidence, in turn, with investors that there will be a positive return on the cost of bring that gas to the market. However, once that initial commitment is made to invest the money, then the need for a return often drives an expeditious program to bring in revenue, even if the market is already reasonably well supplied. Prices may then fall, and the investment becomes a losing one.

The current cold weather in the United Kingdom, and the threat of gas rationing has raised the price some 30% this month and the market appears lucrative. But the UK market, in the short term, can be rescued by 3 tankers of LNG from Qatar with more available if needed. (Provided it is ordered soon.) And then, though there remains a need to refill storage, the crisis will be over for now, and the price will likely fall back. (Although likely not completely since the UK is in process of shutting down coal-fired power stations to comply with EU edicts and natural gas is the replacement fuel of the moment.) Looking further down the road Centrica, a major energy supplier in the UK, has agreed to a 20-year agreement with a US supplier to buy LNG from the US (out of the Sabine Pass terminal). This would take a fifth LNG train, at a facility where the first train is expected to come on line in 2015, and the second in 2016. Each train has a liquefaction capacity of 4.5 million tons pa or 220 bcf of NG, and customers have already been found for the first four trains – again for a 20-year period. The UK supply is therefore not anticipated to start until 2018.

In the meantime Qatar has no plans to increase production in the face of the overall growing glut in supply, although it potentially could. And this availability of alternate supply is not good news for the Big Daddy of natural gas exporters, those in Russia. Russia has already seen Turkmenistan sell its natural gas to China directly, rather than through Russian middlemen. To date this has reached 1.7 tcf with further expansion in the works.

To make the situation more volatile the natural gas discoveries in the eastern end of the Mediterranean over the course of the last five years have been found to be of increasing size, as exploration continues.

Figure 1. Relative location of the gas fields (the green region) being explored in the Eastern Mediterranean (Google Earth)

Three of these fields, Leviathan, Tamar and Dalit are in Israeli waters, while the fourth, Cyprus A, belongs to Cyprus.

Figure 2. The location of the different fields that are being developed by Noble Energy in the Eastern Mediterranean.

In terms of relative size, Cyprus A is at 7 tcf, Leviathan was initially projected at 17 tcf, Tamar at 9 tcf and Dalit is at 0.6 tcf. Since the original projection Leviathan has now been increased to 15 to 21 tcf, with a likely value of 18 tcf.

The Russian natural gas heavyweight, Gazprom has not been neglectful of these developments, occurring as they do in a region where it would not be difficult to challenge their supplies into Southern Europe. Thus Gazprom has been the high bidder in a project to float an LNG plant over the Tamar field and to liquefy that gas so that it can be sold into Asia. The goal for the start of that project is in 2017.

Turning to Leviathan, which is expected to come on line in 2016, with 750 mcfd being supplied to Israel. The interesting question is what to do with the rest. There is talk of a pipeline to run up into Turkey and thence on into Europe. This would have the advantage of further diminishing the European dependence on Gazprom and Russian gas, but there are some political problems. One is that the pipeline would run through the Greek controlled waters off Cyprus, another is that Turkey gets most of its natural gas from Russia and Iran, and they would be displeased. (Though it would help Turkey over the difficult problem of Iranian sanctions).

Figure 3. A pipeline to send the natural gas to Turkey (

When one looks at the Cyprus field, with these ramifications going on in the rest of the global gas market, it becomes a little more evident why Russia has not been willing to dash into the financial scene and bail the Cyprus economy out by buying a future stake in the Cyprus natural gas.

There was an alternative proposal (H/t Gail) for the pipeline to run instead through Cypriot waters and then on up into Europe directly.

Figure 4. An alternate route for the natural gas to reach Europe. (John Galt )

With Cyprus in a financial mess they offered their natural gas to Russia, as part of the security for immediate help. In the end Russia did not bail out the Cypriots. At the same time that Cyprus was talking to the Russians they were also talking with the European Union, and it appears that perhaps the threat of Russian control of Cypriot gas helped expedite an EU rescue move.

There is, I believe, more in this for the EU than for Russia. The benefit to Russia would come more from controlling a relatively small amount of competitive natural gas, at a time when they are trying to maintain the market for their own. And while they likely did not anticipate the hit that Russian bank deposits are taking, the overall cost to them does not translate into an adequate return on the investment that they would have had to make to keep Cyprus stable.

On the other hand this has benefits for the EU if it can further expand the availability of an alternate source of supply to that from Gazprom, then they can possibly lower future projected prices for natural gas. Set against which is the history of Gazprom sitting on the sidelines waiting for an investment opportunity later in the game, and then stepping in and gaining control for a lower price. It will be interesting to see how this one plays out.

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Tuesday, March 26, 2013

Waterjetting 7c - higher pressure washing with power

In the last post, on surface cleaning, I showed how the jet from a fan nozzle spread very quickly once the water left the orifice. With this spread the stream got thinner, to the point that, very rapidly the jet broke into droplets. These droplets decelerate very rapidly in the air, and disintegrate into mist which rapidly slows down. That mist has little capacity but to get a surface wet, and thus, within a very short few inches, the jet loses power and the ability to clean.

How can we overcome this? Obviously the jet would work better if it could carry the energy to a greater distance. And the jet that does that (as we know from trips to Disney) is a cylindrical stream. In some parts of the cleaning trade this is known as a zero degree jet, to distinguish it from the fifteen degree or other angular designation of the fan jet nozzles that it is often sold with.

But the problem with a single cylindrical jet is that it has a very narrow point of application. Depending on the standoff from the nozzle to the target this will increase a little as the distance grows, but is still likely to be less than a tenth of an inch. That, by itself, would make cleaning a bridge deck a long and laborious job. But consider that if we spun the jet so that it is tilted out to cover a 15 degree cone, the same angle as the best of the fan jets, the water would travel further. With a good nozzle it is possible to extend the range to 3 ft, rather than the typical 4 inches of a fan jet.

Figure 1. The gain in performance when a fan spray is changed to a rotating cylindrical jet. (initially proposed by Veltrup, these are our numbers).

In both cases the water flows out of the orifice at the same volume and pressure. But with the rotating jet the water is able to carry the energy some 9 times as far. As a result the area covered is 9-times as wide, and the job is carried out faster.

You can also look at it another way. It takes only about 10% of the water and the power to clean the surface with the rotating jet, as opposed to the amount required to clean with the fan jet. This is even though the pump unit and the flow rates are the same in both cases. This is why, when you buy some of the smaller pressure washers, they include a nozzle that has a round orifice and which then oscillates within a holder. Not quite as efficient as a controlled movement, but at least it is a start.

Now, of course, life is never quite as simple as it at first appears. Because the jet is being rotated there is sometimes, if the jet is being spun fast enough, some breakup of the jet because of the speed of rotation. And so, in the above example, too high rotation speed would have a disadvantage. Doug Wright showed this in a paper he presented to the WJTA in 2007.
Figure 2. The effectiveness of a rotating jet, at two speeds and at different distances (Doug Wright 2007 WJTA Conference Houston).

On the other hand because the jet has to make a complete rotation before it comes back to the same point on the coverage width, if the lance is moving too fast relative to that turning speed, then the jet will miss part of the surface that it is supposed to be cleaning.

I can illustrate this with a sort of an example. To make it obvious the rotating jet has enough power to cut into the material that it is being spun, and moved over. If the rotation speed is too slow, relative to the speed that the head is moving over the surface, then the grooves cut into the surface won’t touch one another and small ribs of material are left in the surface. This is not a good thing, either from a cleaning or mining perspective. The material we were cutting in this case was a simulated radioactive waste, that an improved design later went on to extract as a “hot” material in a real world project. These materials tend to be unforgiving if they are not properly cleaned off.

Figure 3. Cutting path into simulant showing the grooves and ribs where the rotation speed is not properly matched to the speed of the head over the surface.

There is another answer, which is becoming more popular for a couple of different reasons. If the pressure of the water is increased, then the jet will remain coherent for a greater distance, at a higher rotation speed. Going to a higher rotation speed, also brings in an additional change in the design of the cleaning head.

Figure 4. Cleaning head concept sectioned to show vacuum capture of the debris through the suction line after the jet has removed the material and washed it into the blue cylinder.

As the pressure increases, so the energy of the water and the debris rebounding from the surface increase. To a point this is good, since once they are away from the surface it is relatively simple, if the cleaning operation is confined within a small space by a covering dome, to attach a vacuum line to the dome, and suck all the water and debris into a recovery line. The surface remains relatively dry, all the water and debris is captured, and the tool can be made small enough, and light enough, that it can be moved either by a man or on the end of a robotically controlled arm. (The arm we designed the head for was over 30-ft long, which means that the forces from the jets had to be quite small).

With the higher pressure also comes the advantage that the amount of water that is required, for example to remove a lead-bearing paint from a surface, is much lower. If the water becomes contaminated by the material being washed off, then not only has the total volume to be collected, which is an expense, but it also must be stored and then properly be disposed of. And that may cost several times the cost of the actual cleaning operation, if the contaminant is particularly nasty. So reducing the volume of the water is particularly useful.

A friend of mine called Andrew Conn came up with the idea, for removing asbestos coatings from buildings, of tailoring the pressure and the flow from the nozzles, so that the amount of water required was just enough that it was absorbed by the asbestos as it was removed. Simplified and reduced the costs of cleanup, where that was a significant part of the overall price.

And speaking of using higher-pressure water, this means that there is no need for the abrasive additive, when cleaning say a ship hull. And that means that there is no need to buy, collect, and dispose of the abrasive during the operation.

Figure 5. Spent cleaning abrasive at a shipyard.

There are other advantages to the use of high pressure water over abrasive when cleaning metal, and I’ll talk about that subject a little next time.

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Friday, March 22, 2013

OGPSS - The EXXonMobil future - a review

It is the time of year when the major oil companies issue their predictions for the future, and h/t Art Berman, ExxonMobil just released their view of the world, looking forward to 2040. And this is downloadable. If I remember correctly, I first viewed their future projections back in 2011, and with a 2-year step it might be more interesting to see how differences in their world view have evolved in that period.

By 2040 EM anticipates that the global population will be approaching 9 billion, up by around 25% from current numbers. Of that nearly 2 billion additional folk most are expected to be born in the developing countries such as India and in Africa, with the former gaining 300 million and the latter 800 million. Because the majority of the growth occurs in these countries, and the improvement in living standards and working conditions are more energy intensive, (whether air conditioning or iPhones) from a lower base and demand growth is concentrated more in electrical energy demand than that of transportation fuels.

EM continues to believe that, while the economies of the OECD nations will contribute significantly to global growth, with economic output increasing by 80% over the 27-year period, energy demand will remain stable. Growth in demand for power will come from the rest of the world, powering an average 2.8% growth in the global economy over that interval.

Perhaps the greatest change has been in the amount of energy that the company anticipates will not now be needed in that future, as improving energy efficiency cuts back the amount that must be supplied. If we look at the energy projections through 2030 that were made by BP and EM back in 2011, the total growth was expected to continue in an almost linear mode through 2030.

Figure 1. Projections of growth from BP and EM in 2011, looking to 2030.

If one now looks at the shape (the units differ) of the new EM curve there is a dramatic emphasis on a continued improvement in energy efficiency particularly as we get further into the out years. (Note the remaining illustrations all come from the EM document “The Outlook for Energy: A View to 2040”).

Figure 2. Current EM projections for global energy demand in the years to 2040.

The report breaks down the growth in demand into several sectors. And this, at first, is a little irritating. The reason is that, in describing, for example, the growth in residential/commercial energy demand, the track-back on the power sources stops at the point where electric current comes out of the wall. Given that it is the growth in electricity consumption, projected to grow overall by 85%, that is the greatest contributor over the period this is a little disingenuous. Now it is true that there is a whole section devoted to electricity generation, but the lack of the source fuel portrays a little bit of sleight of hand.

Figure 3. Projected residential/commercial energy growth through 2040, by power source.

There is a similar restriction in source categories for the suppliers of industrial power:

Figure 4. Projected residential/commercial energy growth through 2040, by power source.

However, as recognized, the document does have a chapter that deals with the generation of electrical power. EM anticipate that coal will continue to gain market until 2025, but from that point forward, its share will decline as the main competitors, renewables, nuclear and natural gas take an increasing part of the supply.

Figure 5. Change in the source of electrical power and its growth.

Figure 6. The breakdown of electric power fuel sources between OECD and non-OECD countries

One of the reasons for the change, particularly the change to natural gas from coal, comes with the increasing burden of carbon costs, as EM projects.

Figure 7. Anticipated fuel source costs for electricity in 2030.

The low price that is anticipated to continue for natural gas makes it therefore the growth fuel, as figure 5 suggests. When this is combined with the anticipated changes in liquid fuels for transportation, which will see a 40% growth overall, with heavy duty transportation showing the greatest growth, investors in oil and natural gas should be reassured. Cars are expected to achieve an average performance of 47 mpg, which is achieved with the anticipated mix being:

Figure 8. The anticipated growth in automobile performance through the years

Nevertheless the increasing growth of personal transportation in the developing countries is expected to continue to increase demand for oil. With the growth in power generation from natural gas, the two combine to paint a glowing picture of the future of the hydrocarbon industry.

EM project that overall the demand for liquid fuels will rise to 113 million barrels of oil equivalent (mboe) per day by 2040, a 30% growth over 2010 with most of the demand remaining with the transportation needs. The company seems comfortable with industry being able to achieve that level of supply, although the mix will change considerably from that which currently prevails.

Figure 9. Change in the liquid fuel sources that are anticipated over the coming years.

And it is here that I fear that the report becomes overly optimistic. By looking at the relative size of the remaining resource, relative to the production achieved to date, EM foresee no problem in providing the supply targets that are shown in the above figure. EM expect that technical innovation will continue to dramatically improve production from the United States and North America in total. Supply growth is anticipated from tight oil in places such as the Bakken, Deepwater from the Gulf and the tar sands. They project that these will combine to lift North American total liquids production by another 40%. When the production from the offshore Brazilian fields and the heavy oil sands of Venezuela are added, then this reinforces the view that they hold of an achievable target.

Figure 10. Growth in supply of liquid fuels in North America

Yet it is in the Middle East, a region they hardly discuss, that they see the largest growth.

Figure 11. Sources of future growth in liquid fuel supply.

EM don’t actually say where that great growth is likely to come from, but it is very likely heavily weighted towards the most optimistic of estimates for the future production of Iraq, with the ongoing turmoil of the “Arab Spring” being totally discounted.

Well it makes a nice pipe dream, as, I’m afraid, is their anticipation that industry will be able to produce and distribute the target volumes of natural gas that they anticipate will come to save us all from the increasingly higher costs of power. Dare one gently cough and mutter "decline rates"?

If I can put it another way. At the beginning of the report, after projecting a reasonable estimate of global growth over the next 25 years, EM put in a very optimistic level of improvement in energy efficiency in order to significantly lower energy demand. Then, to balance supply to that lower level of demand, they seem to have picked the most optimistic of assumptions about potential growths in that supply. I rather suspect that they are seeing the writing on the wall, but obfuscating it with optimism beyond the bounds of realistic expectation.

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Monday, March 18, 2013

Waterjetting 7b - more insight into jet structure

In last week’s post I showed some high-speed photographs of the plain water jets that come from the small diamond and sapphire orifices and that are useful in cutting a wide variety of target materials. Before moving away from the subject of high-speed photography, this post will use results from that technique to talk about why pressure washer nozzles may not work well, and have limited range. From there it will raise the topic of adding abrasive to a waterjet stream.

Most of us, I suspect, by this point in time, have used a pressure washer to do some cleaning, typically around the house or perhaps at a car wash. The jet that comes out of the end of the nozzle is typically a fan-shaped stream that widens as the water moves away from the orifice. This flattening of the jet stream, and the resulting spreading jet is achieved by cutting a groove across the end of the nozzle to intersect either a conic or ball-ended feed channel from the back end of the nozzle.

Figure 1. Schematic of how a fan–generating orifice is often made.

One of the problems with this simple manufacturing process is that the very sharp edge that is produced to give a clean jet leaving the nozzle is very thin at the end. This means that with water that is not that clean (and most folk don’t filter or treat pressure washer water) the edge can wear rapidly. I have noted several designs (and we tested many) where the jet lost its performance within an hour of being installed, particularly with softer metal orifices. And in an earlier post I did show the big difference between the performance of a good fan jet and a bad.

So how do photographs help understand the difference, and explain why you should generally keep a fan jet nozzle within about 4-inches of a surface it you are trying to clean it. That does, however, depend on the cone angle that the jet diverges at, once it leaves the nozzle. We found that a 15-degree angle seemed to work best of the different combinations that we tried. If the jet remained of sufficient power, this would mean that it would clean a swath about half-an inch wide with the nozzle held 2-inches above the surface. At 4-inch standoff it will clean a swath about an inch wide, and at 6 inches, this goes up to over an inch-and-a-half. But that would require that the jet be of good quality, and evenly distributed.

Figure 2. Back-lit flash photograph of a fan jet, at a jet pressure of around 1,000 psi. It is less than 6 inches from the end of the orifice to the rhs of the picture.

In Figure 2, the lack of water on the outer edges of the stream shows that the water is not being evenly distributed over the fan. As the water volume leaves the orifice, the sheet of water begins to spread out into the wider, but thinner, sheet that forms the fan. But as it gets wider it also gets thinner, and, like a balloon, water can only be spread so thin before the sheet begins to break up. As soon as it starts to do so, the surface tension in the water causes it to pull back into roughly circular rings of droplets.

Figure 3. Fan jet breakup from a spreading sheet into rings (or strings) of large droplets that rapidly break down into mist.

These droplets start out as relatively large in size, but they are moving at several hundred feet per second, and as single droplets moving through stationary air the air rapidly breaks them up into smaller droplet sizes, and then into mist, while at the same time slowing the droplets down. The smaller they get the quicker that deceleration occurs. When droplets get below 50 microns in size they become ineffective. (From a study that was done on determining the effect of rain on supersonic aircraft).

Figure 4. Showing the stages of the fan jet breakup from a solid sheet to mist that does little but wet the surface that it strikes.

However, if the nozzle is held just in that short range where the droplets have formed, but have not broken down, then the jet will be more effective than it would have been at any other point along its length. This is because of something that was first discovered when scientists at the Royal Aircraft Establishment-Farnborough and at the Cavendish Lab at Cambridge University were studying what would happen if they flew a Concorde into rain, while it was still going supersonic. (They actually tried this in a heavy rain storm in Asia and found it was a seriously bad idea).

The pressures that can develop under the spherical droplet can exceed twice the water hammer pressure so that the impact pressure on the surface can exceed 20-times the driving pressure supplied by the pump. But the region effected is very small, and the effect diminishes as the surface gets wetter. And the problem, as with all waterjet streams, is that it is very hard to know where that critical half-inch range is. It varies even within the same nozzle design models due to small changes on the edge of the orifice. And as a very rough rule of thumb, a perfect droplet moving at a speed of around 1,000 ft/sec will travel 138 diameters before it is all mist. Most drops aren’t perfect and thus will travel around 30 – 50 diameters and once they turn into mist they will decelerate to having no power in less than quarter-of-an-inch. The implication of this, which we checked with field experiments, is that if you hold a pressure washer nozzle with a fan tip more than 4-6 inches from the target you are largely just wetting the surface, and spending a fair amount of money in creating turbulent air.

This story of jet breakup is a somewhat necessary introduction to two posts that I will be along before long. The first will be to discuss how we can use a different idea for nozzle designs to do a much better job, at greater standoff distances, and I will tie that in with some of the advantages of going to much higher pressure to do the cleaning job.

The other avenue that this discussion opens relates to how we mix abrasive within the mixing chamber of an abrasive nozzle design, and that will come along a little later.

(For those interested in more reading there have been a series of Conferences on Rain Erosion, and then “Erosion by Solid and Liquid Impact” which were held under the aegis of John Field at Cambridge for many years. See, for e.g.. Field, J.E., Lesser, M.B. and Davies, P.N.H., "Theoretical and Experimental Studies of Two-Dimensional Liquid Impact," paper 2, 5th International Conference on Erosion by Liquid and Solid Impact, Cambridge, UK, September, 1979, pp. 2-1 to 2-8. The founding conference was held under the imprimatur of the Royal Society, which devoted a volume to the Proceedings. Phil. Trans. Royal Society, London, Vol. 260A.)

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Thursday, March 14, 2013

OGPSS - The Pope, Poverty and Power

The new Pope Francis comes from Latin America and has an understanding of the true depths of poverty that is not that common in the United States and Western Europe. Outside the very Western urban part of downtown Buenos Aires lie the barrios and the shanties of the Argentinian poor. Life is more transient in neighborhoods where there is a lack of water, food and opportunity, and where sanitation is a sometime thing. Government programs do not extend far enough, or help many at the bottom of the ladder and government statistics seem to hide much of the problem.

This holds true in many parts of the world. I was struck, at the time of my first visit to China in 1987 by the contrast between the opulence of the walled community in which the “Western” hotels were located in Shanghai and the desperate poverty of the communities just the other side of that wall. Move forward some fifteen years and the cities of China are much different, across much of the landscape. It is a transition that has been effected through large-scale industrialization and the vast quantities of power that is expended in the growth and continuation of that industry. Such a transition is the vision for many countries in the world, but the role of power in that change, and the increasing costs that it imposes, must be recognized. Just having a nominal power available is not, in itself, enough. Consider the case that India, a potential challenger to the Chinese in the market place, now finds itself in. As with China the country has desperate poverty, but it also has a developing industrial base that is driving change. But the rate of that change has, for some time, been limited by the amount of power available.

Power cuts in India are so commonplace that the Times of India recently ran an article detailing some things to do during these “incessant” cuts. And while it is only the major blackouts, such as the power failures at the end of last July that garner global headlines because of the scale, some 600 million people being without power in that event, it is the daily, smaller scale events that are making it increasingly difficult to run a business. In Coimbatore, for example, a city of some 3.5 million people, power outages can last up to 14 hours a day, and “load-shedding”, where power outages are rotated around the neighborhoods is an accepted part of daily life in the country. The ubiquity of these cuts mean that many folk have purchased stand-by generators, which in turn drives up the demand for fuel. But it is difficult to run a business – whether it be a factory or a restaurant, if you don’t have a reliable source of power. And if cuts are frequent enough, and the alternative power costs are too high, then business either closes or moves somewhere else. It is such a decision that is apparently facing small business owners in places such as Coimbatore, but it has the potential to spread to the larger, and now more dependant communities such as Bangalore, the third largest city in the nation, and the Silicon Valley of India.

The city consumes some 2,300 MW a day which it draws from the state grid. About 1,000 MW is generated in the state from nuclear power stations, with the majority of the rest coming from coal, gas and diesel power plants. Because of the prestige of the community it is likely that the city won’t see the worst of the anticipated power shortages this summer, which already have the state trying to buy an additional 1,500 MW. Current supply shortage is around 180 MW but is expected to grow as the weather warms into summer. And since overall Indian supply is challenged by a greater demand, the state can only hope to acquire 1,000 MW to meet the expected demand. They hope that this will be enough to keep the lights and power on in their “Valley.”

This is one of the drivers, expanded to a national scale, that is facing India as it decides what to do over sanctions on Iranian oil. Earlier in that debate India switched out of paying for the oil with US dollars to paying in gold. Given the volumes involved, India imported around 285 kbd from Iran in January, this does nice things (if you are a gold miner) for the price of gold, in dollars. But that can only go so far, and there are suggestions that the payments are becoming more about barter. As a result India has become Iran’s top customer and it is a difficult relationship to change, since some of the Indian refineries are designed only to take Iranian crude. However, as sanctions are growing to include insurance companies, Indian refineries that process the Iranian crude are threatened with the loss of coverage. Whether this will force a change in source of supply, or whether the Indian Government will find a way around the dilemma is an ongoing debate, complicated by the “good deal” that India is getting as a price.

The other fuel on which India is critically dependent is coal. And although the country has large reserves of coal, it is not developing them fast enough to meet demand, and thus must increasingly import both thermal and metallurgical coal.

Figure 1. Indian Coal Statistics (Energy Export Databrowser )

By 2017 imports are anticipated to rise to some 266 million tons of coal, in total. And while much of the press has focused on the Chinese development of new coal-fired power plants, India is planning some 455 new plants, while China has only 363 on the books. This comprises the majority of the 1200 plants currently being planned around the world.

Apart from challenging the opinions of those who suggest that coal demand has, or will soon peak, this speaks to the burgeoning need for fuel sources as nations struggle to bring their poor into a better standard of living. It may well be a debate that now acquires a religious overtone.

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Tuesday, March 12, 2013

Waterjetting 7a - An intro to jet structure

Once a waterjet starts to move out of the nozzle with any significant speed, as the pump pressure begins to build, it becomes more and more difficult to look at the stream of water and get any realistic idea of its structure. Mainly what is seen is the very fine mist that surrounds the main body of the jet, and while some idea of the structure can be obtained by making cuts through material, it can be quite expensive to actually see within that structure. Part of the problem is that though the mist is very fine, it is also moving at speeds in the range of a couple of thousand feet per second. The human eyeball isn’t quite that fast. But we can use a very high-speed flash (in this case it was on for two millionths of a second) which has the effect of “freezing” the motion.

Figure 1. 40,000 psi jet issuing from a 0.005 inch diameter orifice, front lit.

However this mist still hides the solid internal structure of the jet and does not change much in relative structure, even when the internal jet conditions can be quite different. Fundamentally the internal structure was described by Yanaida at the 1974 BHR Group Waterjet Conference, and his description has been validated by many studies since.

Figure 2. The break-up pattern of a waterjet (Yanaida K. “Flow Characteristics of Waterjets,” 2nd BHRA Conf. 1974, paper A2.)

This structure holds for jets across a wide range of pressure and flow volumes, but it is difficult to determine the exact transition points of that structure conventionally. And this can lead to very unfortunate results. I have twice seen people back a nozzle away and then move their hand in front of the jet to show that even high-pressure jets (these were being used to cut paper products and had no abrasive in them at the time) could be “safe.” If both cases the individuals were very lucky to escape injury (water can penetrate the pores of the skin and lacerate the internal parts without any surficial signs of injury, and, as I showed last time, if the nozzle is too close it will slice through flesh and bone). I thought to take today’s post to show, though the use of photographs, why that was such a stupid action.

The photos were taken down at Baxter Springs, KS in the early 1970’s and involved the use of what was then a MacCartney Manufacturing Co intensifier, to shoot jets of varying pressure, and nozzle diameter along a path, so that we could see how coherent the jets were. As I mentioned above, the problem with looking directly at the jet is that the internal structure is hidden by the surrounding mist. To overcome that part of the problem we shone the light along a ground glass screen (to diffuse it) that was placed behind the jet, so that we could see the outline of the internal structure.

Figure 3. Arrangement for taking photographs of a high-speed jet.

This more of the downstream mist from the photograph, and a much better idea of the internal structure of the jet, and where the solid section ended could be measured.

Figure 4. Backlit, 30,000 psi jet issuing from a 0.01 inch diameter nozzle, the distance across the photograph is 6 inches.

The benefit of the technique is perhaps more evident when nozzles at different pressures and diameters and different chemistry are compared. First consider the change with an increase in jet diameter. From the front-lit view there is little difference in the jets. From the backlit, it is clear that the smaller diameter jet only reaches 3-inches across the screen, while the larger jet barely reaches the end of the range.

Figure 5. The effect of doubling the orifice diameter at the same jet pressure on jet range, the photo length is 6 inches.

One of the parts of the study we were carrying out in 1974 was to examine the effect that adding different long-chain polymers had on jet structure. The ones that we were looking at include some that are now used in the oil and natural gas industry to make the “slick water” that is used in the fracking industry to improve production from shale reservoirs. But it also has an advantage in “binding” the jet together. And so, in the study, Dr. Jack Zakin and I tested a wide range of different polymers to see which would be give the best jet.

There were a number of different things we were looking for. In cutting paper, soft tissue and water sensitive material for example, the polymer can bind the water sufficiently well as to further lower wetting to the point where it doesn’t have an effect. It also can improve jet cutting under water – but I’ll cover those in a few post on polymer effects that will come to later in the series.

The effect of a polymer (in this case an AP273) is shown in two tests where the only change was to add the polymer to the water for the lower one.

Figure 6. Jets with an orifice diameter of 0.01 inches at a pressure of 20,000 psi, the range is 6 inches, and the lower jet has had the polymer AP273 added to the water.

The narrower stream in the lower frame is the effect that we were looking for. Putting change in diameter and the better polymers together gave, as an example, the following:

Figure 7. The effect of changing jet pressure, nozzle diameter and polymer content on jet cohesion.

It might be noted that the jet in the bottom frame has as much relative concentration (and power) at the end of the range as the top jet had at the beginning of the range.

Now it all depends on what you want the jet to do, as to which condition you wish to achieve. Inside abrasive mixing chambers the object is much different than it is when the object is to cut a foot or more of foam with high quality edges. And there have been some interesting developments with different polymers over the years, but I’ll save those stories for another day.

But bear in mind that those individuals who could slide their fingers under the jet in the top frame of figure 7 would have had them all cut off if the jet had been running instead under the conditions of the bottom two frames, and in all three cases, to the naked eye the jets looked the same.

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Monday, March 11, 2013

The California Urban Heat Island Effect

Last week Anthony Watts had a post at WUWT in which he talked about a new effort to find out just how much the urban environment was affecting the temperatures at Californian weather stations. The study is being carried out in conjunction with the EPA, and the announcement came by e-mail rather than a more conventional press release.

I was interested since, as part of series that I carried out looking at the US Historic Climate Network (USHCN) data, I plotted temperatures for the stations in each state as a function of latitude, longitude, elevation and local population. The first three values were identified with the information at each station. The local population for a town can be found on the web in several different places, and very largely I relied on the city-data web sites for information (see, for e.g. this for Sacremento).

The question arose as to which particular temperature should be used for that of the station, since the USHCN provides annual average temperatures, as raw data, Time of Observation (TOBS) corrected and “adjusted.” When the original post for California was written, only the last of these was available, and thus it formed the basis of the analysis. Shortly thereafter, in 2010, the USHCN site also provided the raw data, and the TOBS temperatures for each station, each year. The data was therefore re-analyzed using the TOBS values. But the plot that was originally generated was plotting the current population against the average temperature since 1895.

As the study grew to include more states, that plot seemed to be an error, since populations can change very rapidly, and go up as well as down. So, towards the end of the series the average temperature was taken only for the past five years, since this was likely to reflect the impact of current populations. At the same time, since there is little difference between the two sets of values in this period, the “adjusted” values were used to derive the plot. It looks like this:

Figure 1. The comparison of average California station temperature plotted relative to adjacent population, with a log-normal plot.

Now the “discovery” of a log-normal relationship is not new. Oke has been studying the topic for decades, and has proposed such a relationship. But it does have a side effect. Consider what happens when the trend line is shown on a normal plot:

Figure 2. The comparison of average California station temperature plotted relative to adjacent population, with a normal scale on both axes.

There is a “kick-over” in the rate of temperature rise at around a population of 10,000. (In fact this is a curve and the sharp transition is an artifact of the software, but it illustrates the trend). Temperature gains for smaller gains in population are higher below that level, while those above that population require a larger population growth to get the same increase. (Failure to recognize this is one of the underlying faults of the Berkeley Earth Project work on the topic.) Since the GISS data on temperatures also does not recognize any difference in population size below 10,000 it is also a fault of that data set.

I am curious to see how the California study pans out, I did drop a note with this finding to William Dean, as the e-mail suggested, and he was courteous enough to reply noting that this was “an interesting approach.”

As I pointed out to him, the strength of that relationship is, perhaps, borne out not only by the R^2 value, but by the consistency of the coefficient over the plots for a number of states. The tabulation is as follows:

I have had to cut the list in two to allow screen capture.

Figure 3. Correlation Coefficients for the relationship of temperature to local conditions with temperatures in degrees C.

And similarly for the table where I have converted the temperatures to def F.

Figure 4. Correlation Coefficients for the relationship of temperature to local conditions with temperatures in degrees F.

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Friday, March 8, 2013

OGPSS - Venezuela after Hugo Chavez

With the death of the Venezuelan President Hugo Chavez the future production, and exports of Venezuelan crude are gaining a little new attention. I had noted in the last post that there is a difference of around 400 kbd between the 2.379 mbd that outside observers report to OPEC that the country is producing, and the 2.768 mbd that Venezuela itself reported. The question now becomes one as to whether the new President will be able to resurrect an industry that has overseen a slow decline in overall production, with a more rapid decline in exports.

Figure 1. Venezuelan oil statistics (Energy Export Databrowser)

My short answer to that question is No! It is based on a number of reasons, and may be swamped by the voices that note that the country has a vast remaining pool of oil in the Orinoco Basin, that the USGS has estimated to be more than a trillion barrels in size, of which some 513 billion barrels are technically recoverable. But there have been a number of posts about those numbers and the more critical number which is that of the rate of oil production.

Colin Campbell reminded us in his 2006 Review of the country that the Venezuelan Government was one of those urging the creation of OPEC, back in 1960. Back when that piece was written Colin expected that production, which had been falling as the reserves in the Lake Maracaibo region declined, would start to wind back up, as the heavy and extra heavy oils of the Orinoco were brought into a higher level of production. And he anticipated that, by now, the country would be producing around 3 mbd, which it is not.

One of the requirements before one can market the heavy oil is to have refineries that can process the oil. The United States, which imports around 1 mbd of Venezuelan crude, has the Citgo refineries, which are wholly owned by PDVSA (the Venezuelan oil company). Whether that will influence their switch to Canadian crude if the Keystone pipeline is put in place is an open question. But easing the American demand might help with Venezuelan relations with China.

Figure 2. US Monthly imports of crude and Petroleum Products from Venezuela (EIA )

China, which has refineries that Sinopec built that can also handle the crude, has stepped in here and spent over $40 billion with much of this in loans to be repaid through increased oil exports. Back in 2007 China had made the decision to pull out of Canada, and to concentrate its investments in Venezuela instead. Since that time they loaned Venezuela over $20 billion, in return for a commitment for oil exports that were to reach 1 mbd in 2012. The date to reach that target has now slipped to 2015 as overallproduction has continued to decline.

Last August President Chavez announced a $130 billion plan for investment in the Orinoco.
He said that there are 150 different clusters of oil wells in the Belt, but the goal in the next six years is to increase that number to 500. Before the nationalization of the Belt, there were just 37 clusters.

The clusters are comprised of 24 separate oil wells, each of which extract around 1,200 barrels per day. At these facilities, hydrocarbons are extracted using 45-meter drills purchased in Venezuela and assembled in Venezuela.

“All this has been nationalized, which before was the property of multinationals, and production has also been increased,” the president said. He recalled that before the government took control of the Belt, there were just 2,800 wells, while now there are more than 4,000.
Because the Orinoco crude is very heavy, to an API gravity of 9 degrees, it is difficult to produce and requires a considerable energy investment to extract and process the crude.

Last September two joint ventures came on stream. That at Petromiranda, where PDVSA has Russian partners began producing 1,500 bd, after an investment of $800 million, with a goal of eventually reaching 45,000 bd. At the same time Petromacareo, where PDVSA is partnering with the Vietnamese, came on line at 800 bd, with an initial target production of 4,000 bd. (The project has slipped from a target start date of early 2011, and the ultimate goal of 200 kbd from Petrimacareo is in more doubt.)

The crude has to be upgraded, and TNK-BP is partnering to double the capacity of the Petromangas upgrader from 120 to 250 kbd. Until that capacity is increased Orinoco production may be limited.

There is thus a history of project slippage and missed targets that is unlikely to improve in the short term. New plans for further investment either by the Chinese, Indians or Russia are now on hold, while the Presidential election to replace President Chavez is decided, but the experience in the last couple of years is likely indicative that progress in increasing production will be difficult to achieve and when set against a rising domestic consumption (as the Export Land Model predicted) is already leading to a fall in exports.

One of the drivers for that increase in domestic consumption is that the price of gasoline in Venezuela is $0.04 per gallon (four cents). In contrast, in Saudi Arabia it is around $0.61. The low price of gas means that there has been a significant increase in demand, exceeding that domestically available. As a result the country has been importing gas at up to $100 a barrel to sell it for $5 – you can’t balance those books by increasing the volume of sales!!

Yet cutting back on domestic consumption, or increasing prices could prove difficult for the incoming President. So maybe it would be a good idea to invest in the Keystone pipeline, as a simple precaution??

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Monday, March 4, 2013

Waterjetting 6d - Plywood and Pork, and jet effectiveness

In the last two posts I have tried to show that there is a benefit to running an occasional calibration test on equipment, to ensure that it is giving the best performance. This does not mean that the nozzle needs to be tested every day, although some of the cheaper pressure washer nozzles, for example, will wear out in less than an hour. An operator will learn, over time, about how long a nozzle will last, and can, after a while, tell when it is starting to lose performance. But in working on a number of different jobs in succession that sense of the performance may be missed, and it can be handy to have a standard target that a jet can be pointed at that it should be able to cut in a known time.

One simple target is plywood, and, to continue the saga of nozzle comparisons through a slightly different approach, Mike Woodward used plywood sheets to compare different nozzles in one of the earliest comparisons of performance. We since duplicated his test equipment and ran tests with a more modern selection of nozzles, but the basic results and conclusions remain the same.

In its simplest form the idea is to build a holding frame that will hold small squares of plywood at fixed distances from the nozzle. In the frame shown below the plywood pieces are set at one-foot distances apart, with the nozzle held at a fixed point at the end of the test frame. Tests showed that it takes around 2,700 psi to cut through the plywood.

Figure 1. A simple frame to hold plywood samples

The initial tests that Dr. Woodward ran were run on nozzles that were run at 10,000 psi with a nominal flow rate of 10 gpm. The nozzles that were used cost in the range from $10.00 to $250 apiece. (And these costs were reported in 1985 at the 3rd American Waterjet Conference). Tests such as this are simple to run. Plywood pieces are set into the frame, the nozzle is placed at the end of the frame, and the jet run for ten seconds. Over that time, the jet will cut through any of the pieces of plywood that it reaches with enough power to cut through, and generally the jet will punch a hole through several pieces.

Figure 2. The different designs of nozzle that Mike Woodward tested in 1985.

The profiles show that there was only one of the common nozzles at the time that fitted smoothly onto the end of the feed pipe. In the other cases there is a small gap between the nozzle piece and the feed tube, so that turbulence would be generated just as water entered the acceleration section of the nozzle.

The hole size in each plate was then measured, and that width plotted as a function of the distance from the nozzle, so that a profile of the jet cutting path could then be drawn.

Figure 3. Profiles cut into the different pieces of wood, showing the cutting power of the different jets, as a function of distance and the actual amount of water flow as measured.

As an additional part of the testing a rough measure was kept of the effective nozzle life Some other performance parameters for the different nozzles can be put into a table.

Figure 4. Performance of the different nozzles.

Clearly just going out and buying the most expensive nozzle on the block is not necessarily the best idea. But it also depends on the use to which the nozzle is going to be applied. There are two different applications, that of cleaning a surface, and that of cutting into it. The broader path achieved by nozzle 1, for example, which also removed the largest volume of wood per horsepower, makes it a good selection for cleaning, and for reaching further from the nozzle, as would be needed if one were cleaning the pipes of a heat exchanger bundle.

On the other hand the more coherent flow through nozzle 2, which gave a narrower cut might be a more effective tool in a cutting operation. In other cleaning operations where the nozzle is being operated very close to the surface, then nozzle 3, which has a wider path, might be a better choice, though that is lost if the target surface is further away. And though there was not a great deal of difference in performance between nozzles 1 and 5, there is a considerable difference in price.

A smaller, lighter nozzle may be a beneficial trade-off if the nozzle body is fitting on the end of a lance that will be operated manually for several hours at a time.

There is an alternate way of using plywood as a target that I have also used in teaching class. The student is using a manually operated high-pressure cleaning gun at 10,000 psi and is to swing the gun horizontally so that the jet cuts into a piece of plywood that is set almost parallel with the jet path, but with the stream hitting the wood from the side initially further from the operator, but as the swing completes the jet cuts up where the nozzle almost touches it and then sweeps on past.

The result is that, over the distance that the jet can cut into the wood, a groove is carved into the wood.

Figure 5. Horizontal cuts into plywood. There were about half-a-dozen students who had swiped the nozzle so that it just cleared the left edge of this 4-ft wide piece of plywood, and you may note that the cuts extend roughly ¾ of the way along the surface.

Once the students had seen this cut, I would ask them how far away they thought, based on that measurement, that the jet would cut into a person. Typically they said about three feet, and then, as a precaution, I suggested they add a foot or so more.

Then I took them over to a metal frame where we had hung a piece of pork. We carefully measured off the “safe” distance from the end of the nozzle to the pork.

“Now assume that is you”, I would say, “swing the jet as fast as you can, so that it barely has time to hit “your arm”, and we’ll just check that distance is correct.”

Figure 6. Piece of pork that has been traversed by a 10,000 psi jet several times, with a typical standoff distance from the nozzle of more than four feet.

Invariably we got the result shown in Figure 6. The jet would cut into the meat to a typical depth of around two inches and groove the underlying bone. It was a salutary way of getting their attention about the safe use of the tool, and I noticed that the staff also got a bit more cautious after we ran this class every year.

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Sunday, March 3, 2013

The Iditarod is running

For those who follow these things, this year's Iditarod race has started. Alaskan papers are best for following the race.

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Friday, March 1, 2013

Transient publicity

James Stafford was kind enough to interview me for his site at and the interview has been published at a number of other sites.

One or two may have generated a little discussion. The one at Naked Capitalism has raised enough questions that I did write the occasional response. I will comment more as this develops. Heading Out (Dave to most of you). No more yet.

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