Monday, January 21, 2013

Atlantean Mining Technology Rediscovered and Modernized





You do want to go to the original on this one in order to work through the excellent pictures.  Way more important however is that this clears up a major problem that I have had with Bronze Age, or Atlantean mining technology between about 2500 BC and 1159 BC. 

The Bronze Age assumption we have all accepted has involved the use of an open fire on the ore face to induce spalling to collect ore.  It is a really bad idea simply because there is a loss of control of airflow almost immediately.  Carbon monoxide makes it impossible and the heat delivery is terribly low.  On top of all that, any manpower calculations required a huge input for every pound collected.  Yet deep mines are amply in evidence in Cornwall that made air a certain problem.

Prior work using hydrogen attempted to induce rock spalling, but never got much past the hydrogen production problem.

What this modern technological solution does is use diesel duel and a strong air flow to ignite a burn front that becomes a hot zone up against the working face operating at an astounding 1800 C.  This easily shatters the face and allows the material to fall away in small particles ideal for even blowing back.

My key point that I want to make though is that I could easily set up this system using Bronze Age technology.  The Chinese had continuous bellows and even ordinary bellows will create the necessary head pressure.  For fuel we can now use any suitable liquid oil including animal fats.  The torch head will be very hot and the oils will vaporize coming through the head to create a continuous ignition front.

The economics are easily superior to blasting economics in even large underground veins and clearly superb for small vein structures simply because it naturally minimizes dilution with waste rock.  I now understand the nature of some of those old workings.  This is actually a huge breakthrough for underground mining that allows us to go after ore that once was chased with hand steel.

Now we know what to look for the evidence will start to show up.  We already have a Mayan glyph demonstrating the processes at work.  Even better, A friend of mine some thirty years ago chose to inform me that a decade earlier, he had worked underground in Scotland to drive a passage for a dam penstock.  They encountered a borehole that was two feet across in host rock lacking any volcanic nature that was clearly a man made bore hole.  The hole itself had naturally infilled with calcite and was sealed tight.  Yet there was no mistaking what it was.

This demonstration clearly tells us just how such a bore hole came about.  Note that there was no technology then known to do this.  Even now, it still takes centuries to calcite such a hole.

The Atlantean Age had an insatiable appetite for metal as it was hoarded by a globally expanding economy.  Their traces are found all over.   Yet one needs to only closely read ancient texts to understand the centrality of metal in this economy

THERMAL FRAGMENTATION: REDUCING MINING WIDTH WHEN EXTRACTING
NARROW PRECIOUS METAL VEINS

Donald Brisebois and Jean-Philippe Brisebois
Rocmec Mining, Canada



ABSTRACT

The mining of high-grade, narrow vein deposits is an important field of activity in the precious metal mining sector. The principle factor that has undermined the profitability and effectiveness of mining such ore zones is the substantial dilution that occurs when blasting with explosives during extraction.

In order to minimise dilution, the Thermal Fragmentation Mining Method enables the operator to extract a narrow mineralised corridor, 50 cm to 1 metre wide (according to the width of the vein), between two sub-level drifts. By inserting  a strong burner powered by diesel fuel and compressed air into a pilot hole previously drilled directly into the vein, a thermal reaction is created, spalling the rock and enlarging the hole to 80 cm in diameter. The remaining ore between the thermal holes is broken loose using low powered explosives, leaving the waste walls intact. This patented method produces highly concentrated ore, resulting in 400% - 500% less dilution when compared to conventional mining methods.

The mining method reduces the environmental affects of mining operations since much smaller quantities of rock are displaced, stockpiled, and treated using chemical agents. The fully mechanised equipment operated by a 2-person team (1 thermal fragmentation operator, 1 drilling operator) maximises the effectiveness of skilled personnel, and increases productivity and safety. 
The Thermal Fragmentation is currently employed in 3 mining operations in North America.

INTRODUCTION

The mining of high-grade, narrow vein deposits is a predominant field of activity in the precious metal sector. These types of deposits are located throughout the globe and have a significant presence in mining operations. The principle factor that has undermined the profitability and effectiveness of mining such ore zones is the substantial dilution that occurs when blasting with explosives during extraction and the low productivity associated with today’s common extraction methods. The Thermal Fragmentation Mining Method has been conceived to mine a narrow mineralised corridor in a productive and cost efficient manner in order to solve these particular challenges. The following describes this mining method in depth and outlines its successes in improving the extraction process of such ore bodies.

DESCRIPTION OF TECHNOLOGY

A strong burner powered by diesel fuel is inserted into a 152 mm pilot hole drilled into the vein (Figure 1) using a conventional longhole drill. The burner spalls the rock quickly, increasing the diameter of the hole to 30 - 80 cm (Figure 2) producing rock fragments 0 - 13 mm in size. The leftover rock between fragmented holes is broken loose using soft explosives and a narrow mining corridor with widths of 30 cm to 1 metre is thus extracted (Figure 3).  Since the waste walls are left intact, the dilution factor and the inefficiencies associated with traditional mining methods are greatly reduced.

THE BURNER

The burner (Figure 4), powered by diesel fuel and compressed air, creates a thermal cushion of hot air in the pilot hole, which produces a thermal stress when coming in contact with the rock. The temperature difference between the heat cushion and the mass of rock causes the rock to shatter in a similar manner as putting a cold glass in hot water. A spalling effect occurs (Calman and Rolseth, 1968), and the rock is scaled off the hole walls and broken loose by the compressed air.

THE FRAGMENTED ROCK

The process of fragmenting the rock is optimal in hard, dense rock. The spalling process produces rock fragments 0 - 13 mm in size. Figure 5 illustrates the size of the fragmented ore. The finely fragmented ore requires no crushing before entering the milling circuit and can be more efficiently transported since it consumes less space than ore in larger pieces. 

TONNAGE COMPARISON WITH ALTERNATIVE METHOD 

The method produces highly concentrated ore, resulting in 400% - 500% less dilution when compared to conventional mining methods. Table 1 below compares the quantity of rock extracted when mining a 50 cm-wide vein using the thermal fragmentation mining method as opposed to a shrinkage mining method.


The table above shows approximately 4 times less rock needs to be mined for the equivalent mineralised content. This method of extraction allows mine operators to solely extract mineralised zones, thus significantly reducing dilution factors and optimising mine operations as a result. The technology enables the operator to mine ounces and not tonnes.

As a result of less rock being mined, fewer tonnes need to be processed at the mill to extract the precious metals. The quantity of chemical agents needed in the process is greatly reduced and the quantity of energy needed to process the ore is also greatly diminished. The reduced quantity of energy for hauling and processing the ore results in fewer greenhouse gases being emitted. The mining residue that remains once the precious metal contents are removed is 4 times less abundant, using the example above, meaning much smaller tailing areas need to be constructed, maintained, and rehabilitated once mining operations have ceased. The space needed to host the mine site is greatly reduced, the alterations to the landscape are significantly diminished, and the result is a cleaner and more responsible approach to mine operations.

PRODUCTIVITY AND SAFETY 

The shortage of skilled personnel in the mining community has made it essential to find ways to increase productivity per worker while improving working conditions in order to attract and retain skilled miners. 

PRODUCTIVITY

The work group required to operate 1 thermal fragmentation unit consists of a 2 person team (1 thermal fragmentation operator, 1 drilling operator). Table 2 shows the time needed to extract an ore block using the thermal fragmentation mining method in comparison to using a shrinkage mining method.

The table above demonstrates that for the equivalent amount of mineral content, it takes approximately half the time to mine the ore zone using the thermal fragmentation mining method than when using a shrinkage mining method. Furthermore, since less rock needs to be mucked and hauled from the stope, fewer personnel are needed for handling the ore.

MECHANISATION AND EMPLOYEE SAFETY 

Each unit is completely mechanised, reducing the risk of injuries and strain caused by manual manipulation of heavy equipment. The operator stands at a safe distance from the stope, virtually eliminating the risk of flying debris and falling loose rock from the waste walls. Furthermore, unlike shrinkage mining methods, smaller excavations are made (0.5 m compared to 2 m) so the occurrence of falling loose rock is greatly diminished.

OTHER APPLICATIONS - DROP RAISING

The thermal fragmentation equipment is also used to create the centre cut in traditional drop raising. The burner can enlarge a 152 mm pre-drilled pilot hole into an 80 cm cut on a 20 meter distance in approximately 4 hours total. By creating this large centre cut quickly and efficiently, larger sections can be blasted with minimal vibrations (Figure 8), thus avoiding damage to the surrounding rock (Figure 9). The number of blast holes needed and explosives are reduced and the risk of freezing the raise is minimised.

ENVIRONMENTAL IMPACT ANALYSIS

There is a growing need to develop sustainable mining methods that minimise the environmental footprint left behind by mining operations. While developing the Thermal Fragmentation Mining Method, important efforts were made to address and reduce the environmental effects that mine operations have on the surrounding areas. Using the method, mine development is performed directly into ore, resulting in less waste rock being extracted and displaced to the surface. By solely extracting the mineralised zone, only the necessary excavations are made. As shown in Table 1 above, 4 times less rock needs to be mined for the equivalent mineral content. 

As a result of less rock being mined, fewer tonnes need to be processed at the mill to extract the precious metals. The quantity of chemical agents needed in the process is greatly reduced and the quantity of energy needed to process the ore is also greatly diminished. The reduced quantity of energy for hauling and processing the ore results in fewer greenhouse gases being emitted. The mining residue that remains once the precious metal contents are removed is 4 times less abundant, using the example above, meaning much smaller tailing areas need to be constructed, maintained, and rehabilitated once mining operations have ceased. The space needed to host the mine site is greatly reduced, the alterations to the landscape are significantly diminished, and the result is a cleaner and more responsible approach to mine operations.

PRODUCTIVITY AND SAFETY 

The shortage of skilled personnel in the mining community has made it essential to find ways to increase productivity per worker while improving working conditions in order to attract and retain skilled miners. 

PRODUCTIVITY

The work group required to operate 1 thermal fragmentation unit consists of a 2 person team (1 thermal fragmentation operator, 1 drilling operator). Table 2 shows the time needed to extract an ore block using the thermal fragmentation mining method in comparison to using a shrinkage mining method.

The table above demonstrates that for the equivalent amount of mineral content, it takes approximately half the time to mine the ore zone using the thermal fragmentation mining method than when using a shrinkage mining method. Furthermore, since less rock needs to be mucked and hauled from the stope, fewer personnel are needed for handling the ore.

MECHANISATION AND EMPLOYEE SAFETY 

Each unit is completely mechanised, reducing the risk of injuries and strain caused by manual manipulation of heavy equipment. The operator stands at a safe distance from the stope, virtually eliminating the risk of flying debris and falling loose rock from the waste walls. Furthermore, unlike shrinkage mining methods, smaller excavations are made (0.5 m compared to 2 m) so the occurrence of falling loose rock is greatly diminished.

ECONOMIC ANALYSIS

By rendering a greater number of narrow, mineralised zones that are economical to extract, the mining method has the potential to convert a substantial portion of the mineral resources of an operating company into mineral reserves. A large number of mines currently in operation today contain narrow, precious metal veins throughout the ore body, but unless these veins are of significant width (usually 1 m or greater) or very high grade they are often overlooked. As the mine operator develops the zones to be extracted, high grade, narrow ore bodies are often uncovered, but not extracted since it is uneconomical to mine such ore bodies using conventional mining methods (shrinkage, long hole, room and pillar, etc.) Table 3 below demonstrates the cost savings per ounce of using the thermal fragmentation mining method in comparison to the long-hole method. The study was done by Canadian Institute of Mining using 2001 exchange rate figures.

As the analysis above shows, it is approximately 45% less costly to mine a narrow vein ore body using the thermal fragmentation mining method than using a conventional mining method. Overall profitability of mine operations is increased since more precious metals can be economically mined for the same level of development expenditures.

CONCLUSION

Many variations and adjustments have been made to conventional methods of mining narrow precious metal veins, but the serious shortfalls brought upon by dilution remain. The Thermal Fragmentation Mining Method is a new and innovative way of mining narrow vein ore bodies and a foremost solution to solving the problem of ore dilution by reducing it by a factor of 4 to 1. It uses a unique tool, a powerful burner, to mine with precision, a narrow mineralised corridor in an effective and productive manner. The technology is positioned to meet the growing challenges of skilled labour shortages, tougher environmental guidelines, and the depletion of traditional large scale ore deposits mined using conventional methods. As the technology continues to develop and spread through the mining community, the objective remains to optimise the productivity and profitability of mining narrow, high-grade, precious metal ore bodies and to make a substantial, lasting contribution to this sector of activity.

REFERENCES
Canadian Institute of Mining. (2003). Thermal rock fragmentation – Applications in narrow vein extraction. Vol 96, #1071. CIM Bulletin, Canada. pp. 66-71.[1]

Calaman J.J, Rolseth H.C., (1968). Surface Mining First Edition. Chapter 6.4 Society for
Mining Metallurgy and Exploration Inc., Colorado, USA p.325-3

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