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
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 Bulletin ,
Canada
Calaman J.J, Rolseth H.C.,
(1968). Surface Mining First Edition. Chapter 6.4 Society for
Mining Metallurgy and
Exploration Inc., Colorado , USA
No comments:
Post a Comment