U.S. patent application number 10/770013 was filed with the patent office on 2004-08-12 for shaped charge detonation system and method.
Invention is credited to Barnhart, Charles R..
Application Number | 20040154492 10/770013 |
Document ID | / |
Family ID | 30444315 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040154492 |
Kind Code |
A1 |
Barnhart, Charles R. |
August 12, 2004 |
Shaped charge detonation system and method
Abstract
Encapsulated shaped charge for efficient initiation of
hydrodynamic velocity detonation of explosives column. A water
tight capsule with angled sides containing sufficient quantities of
explosive and a detonator means where the capsule substantially
occupies the cross-section of the bore-hole. The capsule contains
up to 30 pounds of explosives. The capsule efficiently and
sufficiently initiates a column of explosives whereby the amount of
Nitrogen Dioxide is substantially decreased.
Inventors: |
Barnhart, Charles R.;
(Cheyenne, WY) |
Correspondence
Address: |
William G. Ackerman
2309 S. Joyce Street
Arlington
VA
22202
US
|
Family ID: |
30444315 |
Appl. No.: |
10/770013 |
Filed: |
February 3, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10770013 |
Feb 3, 2004 |
|
|
|
09589132 |
Jun 8, 2000 |
|
|
|
6684791 |
|
|
|
|
Current U.S.
Class: |
102/475 |
Current CPC
Class: |
F42B 3/00 20130101 |
Class at
Publication: |
102/475 |
International
Class: |
F42B 010/00 |
Claims
I claim:
1. A shaped charge detonation device with a shaped charge of
explosive material used to initiate a column of blasting agent,
said shaped charge detonation device comprising, a capsule filled
with the explosive material, said capsule has a shape to direct an
initiation energy towards the column of blasting agent, said
capsule shape includes a tapered end, a flat end opposite the
tapered end and a passage from the flat end to the tapered end
along the centerline of the capsule with a tube located in the
passage, said capsule is formed from a plastic material, a
detonator means for initiating the explosive material, and a
detonation cord means to initiate the detonator means.
2. A shaped charge detonation device as claimed in claim 1 wherein
the capsule includes a recess in the tapered end for the detonator
means.
3. A shaped charge detonation device as claimed in claim 1 wherein
the detonator means is a cast booster.
4. A shaped charge detonation device as claimed in claim 3 wherein
the detonator means is a cylindrical cast booster.
5. A shaped charge detonation device as claimed in claim 1 wherein
the capsule shape is substantially cylindrical.
6. A shaped charge detonation device as claimed in claim 1 wherein
the capsule shape includes an outer shape and an inner shape, the
outer shape includes the tapered end to allow the capsule to be
lowered past obstructions in a borehole and the inner shape
includes the shape to direct the initiation energy.
7. A shaped charge detonation device as claimed in claim 6 wherein
the capsule shape includes angled sides.
8. A shaped charge detonation device as claimed in claim 7 wherein
the angled sides are angled between 13 to 18 degrees.
9. A shaped charge detonation device as claimed in claim 8 wherein
the angled sides are angled between 16 to 17 degrees.
10. A shaped charge detonation device as claimed in claim 7 wherein
the capsule shape includes draft sides above the angled sides, the
draft sides are angled between 3 to 4 degrees.
11. A shaped charge detonation device as claimed in claim 1 wherein
the plastic material of the capsule above the recess is thinner
than other areas of the capsule.
12. A shaped charge detonation device as claimed in claim 1 wherein
the tapered end is frustoconical.
13. A shaped charge detonation device as claimed in claim 1 wherein
the capsule includes a watertight lid.
14. A shaped charge detonation device as claimed in claim 1 wherein
the capsule is formed in one piece.
15. A shaped charge detonation device as claimed in claim 14
wherein the capsule includes a sealable fill hole in the flat
end.
16. A shaped charge detonation device as claimed in claim 1 wherein
the capsule has a diameter at the flat end substantially equal to a
diameter of the column of blasting agent.
17. A shaped charge detonation device as claimed in claim 14
wherein the tube is integral with the capsule.
18. A shaped charge detonation device as claimed in claim 1 wherein
the capsule includes handholds located at the flat end.
19. A shaped charge detonation device as claimed in claim 1 wherein
the capsule contains between 20 to 30 pounds of the explosive
material.
20. A shaped charge detonation device as claimed in claim 19
wherein the capsule contains between 23 to 27 pounds of the
explosive material.
21. A shaped charge detonation device as claimed in claim 1 wherein
the explosive material and the blasting agent are like
materials.
22. A shaped charge detonation device as claimed in claim 1 wherein
the blasting agent is Ammonium Nitrate/Fuel Oil.
23. A shaped charge detonation device as claimed in claim 1 wherein
said capsule includes internal baffles to strengthen the
capsule.
24. A shaped charge detonation device as claimed in claim 1 wherein
said capsule is formed of plastic.
25. A shaped charge detonation device with a shaped charge of
explosive material used to initiate a column of blasting agent
contained within a borehole, the shape charge detonation device
includes a detonation means for initiating the explosive material
and a detonation cord means to initiate the detonation means, said
device comprising, a capsule filled with the explosive material
wherein the capsule has a shape to direct an initiation energy
towards the column of blasting agent, the capsule shape includes a
tapered end, a substantially flat end and a passage through the
center of the capsule with a tube located in the passage, said
tapered end is frustoconical to allow the capsule to be lowered
past obstructions in the borehole the shape of the capsule includes
sides angled from the tapered end at between 13 to 18 degrees from
the capsule centerline to direct the initiation energy at an
outermost diameter of the column of blasting agent.
26. A shaped charge detonation device as claimed in claim 25
wherein the capsule is plastic and watertight to allow 20 to 30
pounds of the explosive material to remain in the borehole for long
periods of time while remaining unaffected by conditions in the
borehole.
27. A shaped charge detonation device as claimed in claim 25
wherein the capsule includes a recess in the tapered end for
locating the detonator means.
28. A capsule for use in a shaped charge detonation system whereby
the capsule may be transported empty and filled with explosive
materials on a blast site, said capsule comprising: a tapered end
to allow the capsule to be lowered past obstructions in a borehole,
a flat end to maximize an interface surface area between an
initiation energy produced by detonation of the explosive material
and a column of blasting agent, a passage from the flat end to the
tapered end through a centerline of the capsule to isolate the
explosive material from a detonation cord, and a recess in the
tapered end for a detonator.
29. A capsule as claimed in claim 28 wherein said capsule includes
angled sides for forming the explosive material into a shaped
charge.
30. A capsule as claimed in claim 29 wherein said angled sides are
angled between 13 to 18 degrees from the capsule centerline.
31. A capsule as claimed in claim 30 wherein said angled sides are
angled between 16 to 17 degrees from the capsule centerline.
32. A capsule as claimed in claim 28 wherein said capsule includes
handhold means located on the flat end of the capsule to allow
handling of the capsule.
33. A capsule as claimed in claim 28 wherein said capsule includes
internal baffles to strengthen the capsule.
34. A shaped charge detonation device for reducing emissions of
Nitrogen Oxides from blasting, whereby a shaped charge of an
explosive material contained within a capsule releases an
initiation energy upwardly into a column of blasting agent in order
to ensure a resultant detonation reaction attains steady state
velocity of detonation in the blasting agent column closer to the
shaped charge device and thereby prevent deflagration of the
blasting agent, said device comprising said capsule, a detonator
means for initiating the explosive material, and a detonation cord
means for initiating the detonator means.
35. A shaped charge detonation device as claimed in claim 34
wherein said capsule contains between 20 to 30 pounds of the
explosive material.
36. A shaped charge detonation device as claimed in claim 34
wherein the capsule has a snap-fit lid for sealing and a tube
through a centerline for a passage for the detonation cord
means.
37. A shaped charge detonation device as claimed in claim 34
wherein the capsule has angled sides to form the shaped charge to
direct the initiation energy upwardly into the column of blasting
agent and across an entire cross-section of the column of blasting
agent.
38. A shaped charge detonation device as claimed in claim 37
wherein said angled sides located above the tapered end continue
outwardly and upwardly at between 13 to 18 degrees from the capsule
centerline.
39. A shaped charge detonation device as claimed in claim 34
wherein the capsule has a tapered end to guide the capsule past
obstructions when lowered down a borehole.
40. A shaped charge detonation device as claimed in claim 39
wherein said tapered end has a recess for the detonator means.
41. A method of blasting to ensure a column of blasting agent
attains steady state velocity detonation near a shaped charge
including, providing an empty capsule to a blaster, filling the
capsule with an explosive material to form the shaped charge,
sealing the capsule, locating a detonator at a first end of the
capsule, attaching a detonator cord to the detonator, locating the
capsule and the detonator in a borehole, and detonating the shaped
charge.
42. A method of blasting as claimed in claim 41 wherein the capsule
is shaped to provide a shaped charge when filled with the explosive
material, said capsule includes angled sides, a tapered end to
allow the capsule to move past obstruction in the borehole, and a
recess in the tapered end to locate the detonator means
43. A method of blasting as claimed in claim 41 wherein the capsule
is filled with 20 to 30 pounds of the explosive material.
44. A method of blasting as claimed in claim 41 wherein the
explosive material and the blasting agent are like materials.
45. A method of blasting as claimed in claim 41 wherein the
detonator means is a cast booster.
46. A method of blasting to reduce emissions of pollutants by
ensuring a column of blasting agent attains hydrodynamic velocity
detonation near a shaped charge whereby an initiation energy
released by the shaped charge efficiently and sufficiently
initiates the column of blasting agent, including, providing a
capsule shaped to direct an initiation energy towards a column of
blasting agent, filling the capsule with explosive material to form
the shaped charge, sealing the capsule, placing a detonator means
for detonating the explosive material at a first end, placing a
detonation cord means for detonating the detonator means through a
tube located along a centerline in the capsule, attaching the
detonation cord means to the detonator means, locating the capsule
in a borehole, and detonating the shaped charge such that the
initiation energy spreads across the entire cross-section of the
column of blasting agent and provides sufficient energy to overcome
adverse conditions in the borehole and the column of blasting
agent.
47. A method of blasting as claimed in claim 46 wherein the step of
locating the capsule in a borehole includes lowering the capsule to
the bottom of the borehole by the detonation cord means.
48. A method of blasting as claimed in claim 46 wherein the capsule
has a snap-fit lid for sealing the capsule.
49. A method of blasting as claimed in claim 46 wherein the first
end of the capsule is a tapered end to allow the capsule to easily
move past obstructions in the borehole.
50. A method of blasting as claimed in claim 46 wherein the capsule
includes a recess centered on the capsule centerline at the tapered
end to locate the detonator means.
51. A method of blasting as claimed in claim 46 wherein the capsule
includes angled sides to form a shaped charge with the explosive
material.
52. A method of blasting as claimed in claim 51 wherein the angled
sides are angled at between 13 to 18 degrees from the capsule
centerline.
53. A method of blasting as claimed in claim 51 wherein the angled
sides are angled at between 16 to 17 degrees from the capsule
centerline.
54. A method of blasting as claimed in claim 46 wherein the capsule
is filled with 20 to 30 pounds of the explosive material.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to shaped charges and to the use of
shaped charges in explosive blasting and in particular to the
reduction of Nitrogen Oxides from explosive blasting in the mining
industry.
[0002] The art of shaping a detonation charge to do work is a very
well documented process. Explosions used to perforate well casings,
heavy armor piercing shells and fireworks are all examples of
shaping explosive energy.
[0003] In prior art blasting techniques a booster or primer is
mainly used to further initiate a less sensitive blasting agent.
The boosters usually range from one to five pounds in weight and
are available in several compositions and shapes. During blasting a
detonator or booster is used to provide a sufficient amount of
energy to the blasting agent in order to initiate a sustained
reaction in the blasting agent which travels from the point of
initiation, usually the bottom of a bore-hole, through the entire
column of blasting agent. The dynamics of the reaction in the
blasting agent depend on the amount, shape and direction of the
energy produced by the detonator or booster.
[0004] The direction of the initiation energy has many effects.
Ideally the initiation energy produced by the detonator or booster
directs the energy upward to the column of blasting agent and does
not direct energy downward toward mineral strata. This protects the
strata from damage yet accomplishes the initiation of the blasting
agent column. In a shape charge booster the energy is also directed
upward and not outward radially. If energy is directed radially
outward, other bore-holes may be damaged.
[0005] The shape of the initiation energy has significant effects
on the overall blast as well. The shape of the energy wave produced
by the booster or detonator often determines the dynamics of the
reaction of the column of blasting agent. As shown in U.S. Pat. No.
4,938,143, the increase in surface area of the contact between the
blasting agent column and the booster partially determines whether
the blast is overdriven or underdriven. This corresponds to the
reaction dynamics and the overall effectiveness of the blast. The
ideal reaction of the column of blasting agent is one that reaches
hydrodynamic velocity or steady state velocity immediately at the
point of initiation. By shaping the initiation energy wave a steady
state velocity is reached more quickly and the efficiency or
effectiveness of the blast is improved. Additionally, the initial
shape of the energy wave produced assists in detonating the entire
cross-section of the column of blasting agent. As opposed to a
narrow lance of directed energy, by projecting the energy wave to
encompass the sides of the blasting agent column the initiation
energy initiates the entire cross-section of the column and
produces a more desirable reaction traveling up the blasting agent
column.
[0006] The amount of energy produced by a booster or detonator is
also a concern for the efficient and sufficient detonation of the
blasting agent column. The amount of energy produced by a booster
should be enough to effectively initiate the column of blasting
agent, but not so much as to affect the mineral strata, other
bore-holes or the reaction of the column of blasting agent. Too
much energy from the initiation may produce a blow-out or other
effects that do not react the column of blasting agent. By
controlling the amount shape and direction of the initiation energy
a blast's efficiency and effectiveness is controlled for the
desired results.
[0007] Often the conditions present in blasting greatly affect the
efficiency of the blast. During blasting operations bore-holes are
drilled and set with detonation means, booster means or both and
then the blasting agent is supplied into the bore-hole before the
detonation of the explosives. In some instances the blasting agent
lies in the bore-holes for considerable time before the detonation.
Often the blasting agent is adversely affected when allowed to sit
for extended periods of time. The adverse effects are most profound
near the bottom of the bore-holes where any water or other
contaminants collect and the detonation or boosting means is
located. The adverse effects seen in bore-holes may be wetting of
the blasting agent, breaks or discontinuities in the basting column
or other effects. When adverse conditions are present in blasting
the use of prior art shaped boosters and detonators does not lead
to the desired results that is the efficient initiation of the
blasting agent. If the blasting agent surrounding and immediately
atop the boosters or shaped charges is adversely affected by
conditions present in the bore-hole, the shaped charge or booster
directs a shock wave at blasting agent which does not sufficiently
propagate the desired shock wave or reaction. The boosters in use
may shape the energy wave correctly but the size of the initial
detonation is normally not sufficient in order to overcome effects
of the conditions present in the bore-holes.
[0008] When using blasting as a tool for mining or other industries
the bore-holes are sometimes angled to effectuate a desired use of
the energy released during blasting. Often the angled bore-holes
adversely affect the results of the blast. Blasting agent may
settle to one side of the bore-holes. When using prior art type
boosters the orientation of the booster is critical in obtaining
efficient use of the explosives. In angled bore-holes the
orientation of most prior art boosters are suspect. When a small
shaped charge or booster is placed in a bore-hole, the booster or
charge aligns with gravity forces and is often directed out of the
perpendicular cross-section of the explosives column. While the
prior art mentions the critical orientation of the shaped charge in
relation to the cross-section of the blasting column it does not
mention the means of achieving such orientation of the booster in
the bore-holes and in particular the orientation in angled
bore-holes.
[0009] Shaped charge detonation is a technique known to the mining
industry, and almost all of the manufacturers of cast boosters sell
a shaped booster for various applications. The art of shaping a
charge is thoroughly explained in U.S. Pat. No. 4,938,143. U.S.
Pat. No. 4,938,143 provides experimental proof that "steady state
velocity" is reached as quickly as possible with shaped detonation.
Though it is not explained in the patent, molten explosives were
poured into a conical shaped mold and then solidified to make the
shaped booster. U.S. Pat. No. 5,705,768 takes the invention in U.S.
Pat. No. 4,938,143 one-step further by adding a shaped form on top
of a cast booster. This invention fills the cylindrical end with
inert material rather than explosive. The explosive incorporated
into the design is a conical form at the top of the device. The
explosive is conical shaped, and the resulting explosion is shaped
because it takes the form of the cone through which the energy is
broadcast. It also addresses the use of shaped charges to more
effectively initiate the blast to remove overburden from mineral
strata. In U.S. Pat. No. 5,705,768, the shaped charge directs
energy with the use of a concave recess atop the shaped charge
whereby the energy wave is broadened outwardly and up through the
powder column. However, the arrangement disclosed in U.S. Pat. No.
5,705,768 does not solve orientation problems within bore-holes or
address blast initiation of the entire cross section of the powder
column to achieve faster steady state or hydrodynamic velocity.
Though U.S. Pat. No. 5,705,768 does not have experimental findings
it does reference U.S. Pat. No. 4,938,143 as the document to prove
the value of the shaped charge. In fact, the technique of shaping a
detonation is well known in the art. U.S. Pat. No. 4,938,143 is
hereby incorporated by reference to demonstrate that shaped
detonation is more efficient.
[0010] The present art is specific to casting explosive material in
various shapes, the largest of which is 4 pounds. Research has
demonstrated that a shaped booster is far more efficient in
obtaining hydrodynamic velocity than the commonly used cylindrical
booster; however, the shaped booster is not successfully used in
cast blasting. The disadvantage of the present art is that a small
booster will not be orientated correctly when it reaches the bottom
of a bore-hole. If the shaped detonator were upside down it would
extremely compound the problem of low detonation velocity and
concern about orientation may be the primary reason for not using
the existing technology. Although shaped boosters are not being
used in cast blasting the low profile boosters are. These flat
boosters are being used like a shaped charge booster because they
have a large surface area in contact with the Ammonium Nitrate
blasting agent. This large area spreads the energy across the face
of the powder column, just as the shaped charge would do, but there
is no fear of incorrect orientation with this type of symmetrical
booster.
[0011] According to the prior art, shaped boosters of many designs
address the need for attaining a steady state velocity of the
explosive wave front within inches of the booster. Additionally,
some of the prior art addresses the need for shaping the wave front
produced by the booster in order to obtain a more efficient blast.
However, the prior art does not address the initiation of the
entire cross-section of the explosives column with sufficient
energy to overcome adverse conditions.
[0012] In addressing the efficiency, effectiveness and sufficiency
of a blast, a specific problem with blasting is also addressed. In
many blasts the production of pollutants is of great concern. The
pollutants are a direct result of an improper reaction occurring
during detonation. Particular blasting agents have a tendency to
produce environmental pollutants during and after a blast is
initiated. In particular, ANFO produces orange clouds of Nitrogen
Dioxide. Although much of the description is directed toward the
production of pollutants from an Ammonium Nitrate Fuel Oil (ANFO)
blast, the illustration of the reaction is equally applicable to
other types of explosives and their consequent improper detonation
reactions. Similarly, the use of explosives is emphasized by way of
example for the mining industry and in particular the coal mining
industry. However, the discussion and invention are applicable to
other uses of explosives and any limitation contained herein is for
illustration purposes.
[0013] The surface mining industry has long been plagued by the
formation of toxic Nitrogen Dioxide from Ammonium Nitrate and fuel
oil blasts, but more so with the now common technique of Cast
Blasting. The Cast Blast pattern is set up to throw the overburden
(dirt) off of the coal seam, which allows the mine to produce more
tons of coal at a reasonable cost. The problem with Cast Blasting
is that the ANFO columns are 100 feet deep and the blasting agent
must be put into the bore-hole days before the blast. The longer
the ANFO is in the bore hole the greater the chance the blasting
agent immediately around the detonator is affected by temperature,
pressure and water. If the blasting agent integrity is compromised
around the detonator, the blasting agent does not ignite with
sufficient energy and noxious Nitrogen Dioxide gases are formed.
The Nitrogen Dioxide is very visible as large clouds of orange
smoke.
[0014] Clouds of Nitrogen Dioxide gas have become common and severe
since the cast blasting technique was introduced. Although changes
in blasting schemes have helped reduce the Nitrogen Dioxide, the
pollutant still has not been eliminated and the mining industry's
profitability is being affected.
[0015] Deflagration and the subsequent Nitrogen Dioxide (NO.sub.2)
formation is not a new problem, but the magnitude of the problem
has intensified to become an environmental concern. In 1994, the
technique called cast blasting began to be the standard practice
for breaking up the overburden to get to coal seams. Not only did
the technique make the dirt shoveling easier; it cast 35% of the
dirt into the mined out trough so that it did not have to be
shoveled at all. However, it is the cast blasting technique that
became notorious for producing huge clouds of Nitrogen Dioxide gas
with every blast. An estimate of the concentration of Nitrogen
Dioxide in a typical "orange cloud" is about 1,000 pounds and this
new source of Nitrogen Dioxide has become a significant
environmental concern as well as a public health threat.
[0016] The change from load-and-shoot blasting to cast blasting has
undoubtedly affected the chemistry of the blast and has lead to the
creation of Nitrogen Dioxide clouds. The bore holes are three times
deeper, the blasting agent "sleeps" in the ground for many days,
and there is no way of knowing if the detonator is surrounded by
active blasting agent at the bottom of these bore holes. It would
appear that some basic principle of blasting was violated when cast
blasting was introduced to some areas.
[0017] The particular type of blasting that has lead to the
creation of the Nitrogen Dioxide problem is cast blasting. The
blasting technique was investigated to determine the factors that
might affect the chemistry. The sequence of a cast blast is
disclosed below.
[0018] The cast blast is set up to kick the overburden off into the
already mined out trough left by the coal seam. The bore holes are
drilled at a 20.degree. angle to ensure that the toe of the bench
slides into the trough. The holes are pushed all the way to the
coal seam and then back filled with ten feet of dirt to position
the blast just above the coal seam. When the blast is detonated,
the front row of holes initiates first. This breaks up the
overburden and starts it moving outward and downward toward the
trough. Blowing the front row provides relief for the next row so
that the new blast wave can broadcast the dirt outward.
[0019] When the second row of holes is initiated the second relief
of dirt follows the first. The cast blast is designed to be
powerful enough to put the first relief of dirt in the trough and
put about half the second relief of dirt on top of the first. A
good cast blast should move 35% of the overburden off of the coal
seam. The loosened rock or muck, blown into the trough, does not
have to be shoveled. The first row will blow the hardest because
the rock is still tight and the gas energy has a solid wall to push
against. As each row blows the ground becomes fractured and
fissures allow some of the gas energy to be lost, which limits the
amount of cast achieved by the last row of holes. The third row
detonation blows into the relief of the second row blast and drops
the muck on top of the coal.
[0020] The cast blast results in a 45% cast. It is the success of
the blasting program that dictates the overburden removal costs.
The more dirt that is cast off of the coal seam the less dirt that
must be shoveled. The overburden to coal ratio is an important
economic number to coal mining, as is the cost per cubic yard to
remove overburden. The end result of a cast blast is an orange
cloud of Nitrogen Dioxide gas. The poisonous gas rises out of the
muck pile for many minutes after a cast blast.
[0021] It is therefore an object of at least one aspect of the
present invention to address the problems and disadvantages
above.
[0022] It is an object of the present invention to overcome the
adverse conditions often times present in bore-holes and to supply
a device which ensures a large amount of dry or unaffected blasting
agent for sufficient initiation of the blast.
[0023] Another object of the present invention is to provide an
effective shaped charge for use in the explosives and mining
industry.
[0024] Yet another object of the present invention is to address
the need to increase detonation power to reach steady state
velocity as quickly as possible.
[0025] It is an object of the present invention to provide a
capsule for the blasting industry that is not an explosive but can
be made into a shaped explosive charge by the user or blaster.
[0026] It is also an object of the present invention to provide a
device that does not require special care to orientate the shaped
charge toward the powder column.
[0027] Another object of the present invention is to provide a
device that can be added on top of the existing system to enhance
the detonation of the booster.
[0028] Yet another object of the present invention is to provide a
device that can slide down an angled bore-hole and orient the
shaped charge toward the powder column.
[0029] Still another object of the present invention is to provide
a device that has enough weight to ensure it reaches the bottom of
a bore-hole greater than 100 feet deep.
[0030] It is an object of the present invention to provide a device
that can be made to have a density greater than water so it can
sink through water.
[0031] Another object of the present invention is to provide a
device to ensure that the blast energy of the detonator contacts 25
pounds of blasting agent that has not been compromised by
temperature, pressure and/or water.
[0032] Still another object of the present invention is to provide
a device that ensures that the blasting agent in intimate contact
with the booster does not diffuse into the formation.
[0033] Yet another object of the present invention is to provide a
device that can be added to the existing system when additional
energy is needed.
[0034] It is an object of the present invention to provide a device
that can be varied to deliver blast energy so the explosion is not
overdriven or under driven.
[0035] It is an object of the present invention to overcome the
adverse conditions often times present in bore-holes and to supply
a device which ensures a large amount of dry or unaffected blasting
agent for initiation of the blast.
[0036] It is yet another object of the present invention to
initiate an entire cross section of a blasting agent column to
produce a steady state hydrodynamic shock wave at or near the
bottom or area of a capsule in order to completely fire the column
efficiently
[0037] Another object of the present invention is to provide a
device that can be placed at varied points in the bore-hole to
accelerate the energy as needed.
[0038] Other objects of this invention will become apparent from
the following description.
BRIEF SUMMARY OF THE INVENTION
[0039] This invention is a shaped charge in the form of a capsule
designed to contain high energy blasting agent. The capsule may be
filled and shipped as an explosive device or may be shipped as a
capsule and filled with explosives at or near the site of blasting
by the end user or blaster. The present invention is a tool to
augment the existing blasting technology. In the event of shipping
the capsule not filled with any explosive materials it does not
qualify as a munitions, ordinance, pyrotechnic, bomb and or any
other DOT Class 1 material so it may be shipped at a reasonable
cost anywhere in the world. The present invention is a shaped
charge that utilizes a capsule to sufficiently, efficiently and
effectively initiate a column of blasting agent. The filled capsule
produces an initiation energy for a detonation of a column of
blasting agent. The amount, shape and direction of the initiation
energy is controlled by the capsule in order to efficiently and
sufficiently react the blasting agent column for an effective
blast. The present invention overcomes the conditions common in
bore-holes such as contamination and corruption of the blasting
agent and column, and the difficulties in the orientation of
boosters and other initiators. The present invention also addresses
the need for a large quantity of explosives to sufficiently and
properly initiate a column of blasting agent. The present invention
also reduces the amount of pollutants emitted by cast blasting.
[0040] This invention utilizes a capsule which shapes detonation
energy to assure hydrodynamic velocity is reached closer to the
initial site of detonation of the explosive blasting agent column
and to prevent the formation of pollutants in mining blasts. By
ensuring the detonation reaches hydrodynamic velocity at or near
the initial site of detonation, the capsule increases the
efficiency of the blasting agent column to achieve the desired
results of the blast. Additionally, focusing the energy of the
initial detonation at the blasting agent ensures the powder column
reaches hydrodynamic velocity so it does not produce pollutants.
The present invention provides a detonation system that can be used
to solve the "orange smoke" problem in cast blasting.
[0041] This invention is a technical solution to the environmental
problem and thus a solution to keeping the mining industry
profitable. By initiating ANFO powder columns with concentrated
energy, the formation of Nitrogen Dioxide is dramatically reduced.
This invention is a plastic capsule that is to be filled with high
energy blasting agent and fitted with a standard detonator means.
The design of the capsule ensures that a large volume of blasting
agent is protected from degradation and further ensures that the
hydrodynamic velocity of the detonation is energetic enough to
prevent Nitrogen Dioxide formation.
[0042] This invention is designed to address two other problems in
the detonation of a bore-hole filled with blasting agent. The
capsule is designed to protect up to 30 pounds of blasting agent
from the affects of temperature, pressure and moisture at the
bottom of the bore hole. The capsule further ensures that a
commonly used cylindrical cast booster or other detonation means is
in intimate contact with a sufficient amount of unadulterated
blasting agent that will immediately initiate the powder column at
hydrodynamic velocity. The capsule is shaped such that it projects
the energy of the detonation directly at the column of blasting
agent to spread the supersonic gas jet to the sides of the
bore-hole. By providing the assurance that the detonator system
will initiate with maximum energy, the Ammonium Nitrate will react
completely and not form environmental pollutants. The capsule will
protect and project the blast energy to ensure hydrodynamic
velocity is obtained at the bottom of the blast hole or at the
capsule location.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0043] FIG. 1 is an illustration of a resultant blast initiated by
a typical detonator.
[0044] FIG. 2 is an illustration of a resultant blast initiated by
a shaped charge booster.
[0045] FIG. 3 is an illustration of a resultant blast initiated by
a large booster.
[0046] FIG. 4 is an illustration of a resultant blast initiated by
the present invention.
[0047] FIG. 5 is an illustration of a desired initiated shock wave
from the present invention.
[0048] FIG. 6a is a sectional view of a bore-hole locating a
capsule according to one form of the present invention.
[0049] FIG. 6b is a sectional view of a bore-hole locating another
capsule according to another form of the present invention.
[0050] FIG. 7a is a sectional side view of a capsule according to
one form of the present invention.
[0051] FIG. 7b is a top view of a capsule according to one form of
the present invention.
[0052] FIG. 8a is a sectional side view of a capsule according to a
form of the present invention.
[0053] FIG. 8b is a further sectional side view of a capsule
according to another form of the present invention.
[0054] FIG. 8c is a top view of a capsule according to another form
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0055] It should be appreciated that this invention is described by
way of example and that modifications and improvements may be made
to the invention without departing from the scope thereof as
defined by the claims. The present invention sets out to solve the
problems of blasting by producing an initiation detonation that is
shaped, directed and sufficient to efficiently react and detonate a
column of explosives or blasting agent. The problem of the
production of pollution from blasting is also solved by the control
of the blast reaction dynamics by this detonation system.
[0056] The idea that Nitrogen Oxide formation can be stopped with a
shaped energy detonation is novel to the present invention.
Consequently, this disclosure will review the chemistry for the
creation of Nitrogen Oxides from ANFO blasts and how detonation
energy solves the problem.
[0057] The objective in reducing Nitrogen Dioxide formation is to
promote detonation and avoid deflagration. The chemical reaction in
the Ammonium Nitrate/Fuel Oil explosive is the extremely rapid
(explosive) burning of particles. There are many factors that
affect how quickly the particles burn; however, there is more than
just burning that occurs in the detonation process. The rapid
burning of the powder column must be initiated by a shock wave of
sufficient heat and pressure to drive the reaction and, in turn,
the burn must continue to propel the shock wave to sustain the
detonation. This burning occurs at a supersonic speed during
detonation and subsonic speed during deflagration. The supersonic
shock wave travels through the powder column just ahead of the fire
front and brings the ANFO to an optimum state of reactivity. The
intense heat and pressure generated by the rapidly burning chemical
continues to provide the shock front to support the supersonic
reaction. If the particle-burning rate fails to reach supersonic
speed, the reaction will result in deflagration rather than
detonation.
[0058] During deflagration the Ammonium Nitrate/Fuel Oil blasting
agent still burns rapidly enough to make a huge volume of expanding
gas, but deflagration does not produce the shock wave ahead to the
reaction zone. Consequently, deflagration does not fracture the
formation well and is characterized by orange Nitrogen Dioxide
smoke. The Nitrogen Dioxide gas formation is the result of slow
particle burning that happens at a detonation velocity 3,000
feet-per-second slower than the ideal velocity. Thus, the
efficiency of the detonation reaction affects the effectiveness of
the overall blast and the formation of pollutants.
[0059] Theoretically, detonation and deflagration can be depicted
by mathematical formulas that describe the percent involvement of
the chemical reaction. The fraction of the chemical reaction is
proportional to the detonation velocity by the following
equation:
N=(D/D*).sup.2
[0060] Where N represents the Fraction of Reaction, D is the actual
Detonation Velocity and D* is the ideal Detonation Velocity for the
illustrated equation.
[0061] The ideal Detonation Velocity for ANFO is 15,600
feet-per-second. This is achieved in a 10-inch diameter hole, which
will be assumed as the standard bore hole diameter for cast
blasting as well as for this discussion. The following table
illustrates how the Fraction of Reaction is affected by a 3,000
feet-per-second decrease from ideal Detonation Velocity.
1 D D/D* N = (D/D*)2 15,600 100% 100% 14,600 94% 88% 13,600 87% 77%
12,600 81% 66%
[0062] A denotation velocity of 12,600 feet-per-second is the point
of ANFO deflagration in a 10 inch bore hole and the result of only
66% of the blasting agent being completely reacted. The Fraction of
the Reaction can further be related to the Grain Burning Theory
equation as follows:
N=1-(1-t/T).sup.3
[0063] Where N represents the Fraction of Reaction, t is the
Reaction Time, and T is the Grain Burning Time for the illustrated
equation.
[0064] It was previously calculated from the detonation velocity,
that deflagration occurs when the Fraction of the Reaction is only
66%. Using this 66% reaction rate as the point of deflagration it
can be calculated that the particle burning rate is 3.33 times
slower than optimum. This slowing in particle burning rate is
calculated as follows:
2 1 - (1 - t/T).sup.3 = 0.65 (1 - t/T).sup.3 = 0.35 (1 - t/T) =
0.70 t/T = 0.30 T t/T (1 - t/T)3 N = 1 - (1 - t/T)3 1 100% 0% 100%
2 50% 13% 88% 2.5 40% 22% 77% 3.33 30% 34% 66%
[0065] The factor that adversely affect the Fraction of Reaction
are shown in the following table. The decrease from ideal
detonation velocity is aligned with the decrease in particle
burning rate to demonstrate their relationship to each other.
3 Fraction of Detonation Velocity Grain Burning Rate Increase
Reaction 15,600 feet-per-second Optimum 100% 14,600 feet-per-second
Particle burns 2 times slower 88% 13,600 feet-per-second Particle
burns 2.5 times slower 77% 12,600 feet-per-second Particle burns
3.33 times slower 66% deflagration
[0066] The mathematical formulas can be used to demonstrate how the
particle burning rate is related to the amount of reacted blasting
agent and, in turn, how the reaction is related to the detonation
velocity. It then becomes obvious that anything that slows the
particle-burning rate and/or slows the detonation velocity affects
the fraction of the reaction. Consequently, if the fraction of the
reaction is only 66%, the powder column is in a state of
deflagration and orange Nitrogen Dioxide smoke is produced.
[0067] In summary, to achieve detonation rather than deflagration,
the reaction must be initiated at a supersonic rate and the
particle-burning rate must maintain the supersonic reaction. That
is why the energy of the booster is critical to optimum detonation.
Therefore the initiation of an entire cross section of an
explosives column to produce a steady state hydrodynamic shock wave
at or near the bottom or area of the capsule in order to completely
fire the column efficiently and sufficiently in order to reduce or
eliminate the production of pollutants is desired in a shaped
charge detonation system.
[0068] The detonation system is a shaped charge in the shell of a
capsule designed to contain high energy blasting agent. The capsule
may be filled and shipped as an explosive device or may be shipped
as a capsule and filled with explosives at or near the site of
blasting by the end user or blaster. In the event of shipping the
capsule not filled with any explosive materials it does not qualify
as a munitions, ordinance, pyrotechnic, bomb and or any other DOT
Class 1 material so it may be shipped at a reasonable cost anywhere
in the world. By allowing the end user or blaster to fill the
capsule with an explosive of their choice, the cost is reduced. The
design of the capsule reduces the need for complicated
manufacturing and precision in the production of a shaped charge.
Precise casting or filling of the capsule is not needed and can
therefore be done by a blaster on-site. The blaster or end-user may
be the explosives engineer, company or other entity responsible for
setting and producing a blast.
[0069] The detonation system provides a plastic form referred to
herein as a capsule. The detonation system is a shaped charge that
utilizes a capsule to sufficiently, efficiently and effectively
initiate a column of blasting agent. The filled capsule produces an
initiation energy for a detonation of a column of blasting agent.
The amount, shape and direction of the initiation energy is
controlled by the capsule in order to efficiently and sufficiently
react the blasting agent column for an effective blast. The filled
capsule overcomes the conditions common in bore-holes such as
contamination and corruption of the blasting agent and column, and
the difficulties in the orientation of boosters and other
initiators. The detonation system also addresses the need for a
large quantity of explosives to sufficiently and properly initiate
a column of blasting agent.
[0070] The capsule when filled forms a shaped charge from the
explosive material contained inside the capsule. The capsule is
made to contain 12 liters of high energy emulsified blasting agent
for a 10-inch bore-hole. The capsule size may be modified to
conform to other sizes of bore-holes. With smaller bore-holes the
capsule will contain less blasting agent but provide the same
results. The explosive contents of the capsule are to be initiated
with a typical cast booster. However, other detonator means may be
employed to initiate the contents of the capsule. The shape of the
capsule then provides a shape to direct most of the initiation
energy at the blasting agent column.
[0071] The detonation system utilizes a capsule which shapes
detonation energy to assure hydrodynamic velocity is reached closer
to the initial site of detonation of the explosive blasting agent
column and to prevent the formation of pollutants in mining blasts.
By ensuring the detonation reaches hydrodynamic velocity at or near
the initial site of detonation, the capsule increases the
efficiency of the blasting agent column to achieve the desired
results of the blast. Additionally, focusing the energy of the
initial detonation at the blasting agent ensures the powder column
reaches hydrodynamic velocity and reduces deflagration, so it does
not produce pollutants. The present invention provides a detonation
system that can be used to solve the "orange smoke" problem in cast
blasting.
[0072] The detonation system is designed to promote hydrodynamic
velocity in bore-holes where the conditions of the blasting agent
may be compromised. In the case of ANFO, the Ammonium Nitrate in
the bore-hole has the potential to be affected by water, pressure,
sulfide ore, temperature, loose geological structure, fissures and
break up of the powder column. Wherever the conditions may require
additional detonation energy, the capsule may be added to enhance
the performance of the booster. The capsule may contain up to 30
pounds of explosives in order to provide sufficient energy to the
powder column or column of blasting agent.
[0073] The detonation system is a technical solution to the
environmental problem and thus a solution to keep the mining
industry profitable. By initiating ANFO powder columns with
concentrated energy, the formation of Nitrogen Dioxide is
dramatically reduced. The detonation system is a plastic capsule
that is to be filled with high energy blasting agent and fitted
with a standard detonator means. The design of the capsule ensures
that a large volume of blasting agent is protected from degradation
and further ensures that the hydrodynamic velocity of the
detonation is energetic enough to prevent Nitrogen Dioxide
formation.
[0074] The detonation system is designed to address two other
problems in the detonation of a bore-hole filled with blasting
agent. The capsule is designed to protect up to 30 pounds of
blasting agent from the affects of temperature, pressure, moisture
and other adverse conditions at the bottom of the bore hole. The
capsule further ensures that a commonly used cylindrical cast
booster or other detonator means is in intimate contact with a
sufficient amount of unadulterated blasting agent that will
immediately initiate the powder column at hydrodynamic velocity.
The capsule is shaped such that it projects the energy of the
detonation directly at the column of blasting agent to spread the
supersonic gas jet to the sides of the bore-hole. By providing the
assurance that the detonator system will initiate with maximum
energy, the Ammonium Nitrate or other blasting agent will react
completely and not form environmental pollutants. The capsule will
protect and project the blast energy to ensure hydrodynamic
velocity is obtained at the bottom of the blast hole or at the
capsule location.
[0075] A typical result of a blast 3 initiated with a one pound
booster 1 in the bottom of a bore-hole 2 is shown in FIG. 1. A
bore-hole 2 has been drilled to a pre-selected depth over mineral
strata 4. A booster 1 is placed in the bottom of the bore-hole 2 in
order to initiate a column of explosives placed over the booster.
The one pound booster 1 provides an energy wave to initiate the
column of explosives. The energy wave, however, is not sufficient
enough to produce a steady state velocity shock wave near the
bottom of the bore-hole. The shock wave typically reaches steady
state velocity 5 in the borehole approximately forty feet from the
booster or point of initiation. FIG. 2 shows a similar use of a
shaped charge as described in prior art. The shaped charge 6 is
located in the bottom of the bore-hole 2, but the shaped charge
booster 6 may be misaligned because of the angle of the bore-hole
2. Typically, the shaped charge 6 produces an efficient shock wave,
but due to the misalignment with the column of explosives the shock
wave 7 does not achieve steady state velocity until it has traveled
approximately twenty-five feet from the bottom of the bore-hole 2
or point of initiation. FIG. 3 shows a typical result 8 of a ten
pound booster 9 used for initiation. The shock wave 10 attains
steady state velocity closer to the bottom of the hole, around ten
feet from the bottom or point of initiation, but the increased
energy is not properly directed at the column of explosives and the
mineral strata 4 is often damaged along with the other bore-holes
not yet initiated. Typically, prior art boosters are small due to
the explosives used and economic efficiency. Additionally, if a
prior art booster was composed of 25 pounds of pentolite or other
explosives normally used in boosters, the resulting initiation
explosion would be too large and would result in damage to other
bore-holes and mineral strata.
[0076] The result 11 of using the present invention for initiation
of a column of explosives in a bore-hole 2 is shown in FIG. 4. The
capsule 12 filled with explosives is properly oriented at the
bottom of the bore-hole 2. The result 11 of the shaped charge
sufficiently and efficiently initiates the column of explosives and
the shock wave 13 reaches steady state velocity extremely close to
the bottom of the bore-hole 2 or point of initiation. Even though,
a large amount of explosives is used in the capsule 12 the shaped
charge directs most of the energy up and into the powder column
thereby minimizing the damage to the mineral strata 4 and other
bore-holes.
[0077] The dynamics of the shock wave or reaction interface are
shown in FIG. 5. The capsule 12 filled with explosives is detonated
thereby producing a sufficient amount of energy to efficiently
initiate the blasting agent powder column 14. The shaped charge of
the capsule initiates a reaction or detonation of the blasting
agent near the top of the capsule 12. The detonation shock wave 15
is spread across the entire cross-section of the powder column 14
and produces a reaction interface 16 that travels up the powder
column 14. The resultant supersonic high pressure interface shock
wave 15 drives the blasting agent powder column 14 to detonation.
The result of the efficient detonation is a high temperature volume
of expanding gas 17 that affects the desired results of the
blast.
[0078] The capsule is circular in cross-section. A sturdy collar
around the circumference of the capsule shapes the blast energy
into a supersonic jet of energy that uniformly ignites the circular
cross-section powder column. The body of the capsule has a gradual
taper at a 13 to 18-degree angle from the capsule centerline, to
form the shaped charge and shape the energy as it is created by the
high-energy explosive that fills the capsule. Preferably, the taper
of the capsule is a 17 degree angle. The angle is remarkably
critical in the design because it creates greater energy than does
a straight-sided cylinder. This angle assists in spreading the jet
of exploded gases to the sides of the bore-hole such that steady
state velocity will be obtained as quickly as possible, without
having to have the capsule the same diameter as the bore-hole.
Typically, the capsule will have a 1/4 to 1 inch clearance between
the sides of the capsule and the sides of the bore-hole. The angle
also provides the shaped charge with a proper shape to sufficiently
initiate the entire cross-section of the powder column to achieve a
shock wave that initiates the outer circumference of the powder
column as well. Without the angle, the shock wave does not spread
to an even burn and results in an underpowered condition.
[0079] A filled capsule 12 is placed down a bore-hole 2 in FIG. 6a.
The capsule 12 was filled with explosive material 20 by the blaster
and sealed with a snap-fit lid 21 to produce a water-tight seal as
shown in FIG. 7. The blaster or user then threads detonation cord
means 22 to initiate the detonation through the tube 23 located in
the center of the capsule 12. The tube 23 provides a barrier
between the detonation cord means 22 and the explosive material 20
contained within the capsule 12. The detonation cord means 22 is
then pulled through the tapered end 24 of the capsule and passed
through a detonator means 25. The detonation cord means 22 is then
pulled taught and the detonator means 25 is located in the recess
26 at the tapered end 24 of the capsule 12. The capsule 12 is then
lowered into the bore-hole 2 tapered end 24 down. The rounded end
of the tapered end 24 of the capsule 12 allows the capsule 12 to be
easily passed down the bore-hole 2. The angled sides 27 of the
capsule 12 above the recess 26 is the angle to produce efficient
detonation by way of shaping the detonation wave. The angled sides
27 of the capsule are angled outward and upward from the bottom of
the capsule 12. The sides of the capsule from the bottom of the
capsule 12 to the region of the upper part of the recess 26 are
angled to allow the capsule to easily slide down a bore-hole and
forms the tapered end 24. The sides of the capsule 12 from the
upper region of the recess 26 are angled to shape the detonation
wave and form the angled sides 27 of the capsule. This shaped angle
is between 13 and 18 degrees. Preferably, the shaped angle is 17
degrees to shape the detonation wave. The sides of the capsule 12
continue at the shaped angle until the maximum diameter 28. Above
the shaped angle, the sides 29 of the capsule are straight or not
angled from the shaped angle to the top or lid 21 of the capsule.
In a preferred embodiment, shown in FIGS. 6b and 8a-8c, the angled
sides 27 of the capsule are at the shaped angle, and then the sides
29 are reduced in angle to a 3 or 4 degree draft 30. The sides of
the capsule have a draft 30 from the shaped angle to the top of the
capsule or lid 21. The draft 30 further shapes the detonation wave
and spreads the detonation to the entire cross-section of the
blasting agent column 2.
[0080] Within the capsule is a recession 26 into which a typical
cylindrical booster will fit. A cylindrical booster may be used for
detonation of the explosives in the capsule, but other detonator
means 25 may be used to detonate the explosive material 20 in the
capsule 12. The recession 26 is separated from the cavity of the
capsule by a thin plastic wall 31. The wall 31 is thinner than the
rest of the capsule shell so the explosion can easily ignite into
the explosive material 20 or blasting media inside the capsule 12.
The detonator means recession 26 is orientated at the tapered end
24 of the capsule. The recession 26 is remarkable in the design
because it acts to prevent lateral energy loss from the booster by
encouraging the energy to follow the upward path of least
resistance. The capsule shell may be thicker radially surrounding
the recession 26. The tapered end 24 of the capsule is oriented
down the bore-hole 2 and typically is located at the bottom of a
bore-hole 2.
[0081] When the capsule is lowered into the bore-hole a blasting
agent is then placed on top of the capsule and fills the bore-hole
to the desired level. The capsule 12 as shown in FIG. 6a has a tube
23 or passage which is located through the center of the capsule
12, and the capsule lid 21 forms a watertight seal with the tube 23
to protect the contents of the capsule. The lid 21 has a bevel at
the tube 23 passage to ensure the seal. The tube 23 also forms a
water tight seal at the bottom of the capsule at the recess 26. The
tube may also be a plunger means to initiate the detonator means
25.
[0082] The capsule design incorporates a passage tube 23 from the
flat end of the capsule to the booster recession 26. The passage is
used to attach detonation cord means 22 and non-electric initiation
to the booster. Preferably, the passage is 0.75 inches to
accommodate several known types of detonation cord. The tube 23
acts to confine the burning of the detonation cord means 22 so that
it does not prematurely ignite the confined blasting media inside
the capsule before the booster initiates. The tube 23 is placed
longitudinally through the capsule and symmetrically centered from
top to bottom.
[0083] Preferably, the flat end 37 of the capsule is designed with
a recessed handhold 32 and a 4-inch opening 33 through which the
high energy-blasting agent is added to the capsule. The opening 33
is sealed with a bung after filling. When sealed the system is
watertight. The capsule may be a continuous molded piece for
strength, or the capsule may also employ a snap-fit lid 21 in order
to add or fill the capsule with explosives. The handhold 32, in the
top of the capsule, allows the container to be up righted so the
detonation cord means 22 can be threaded through the longitudinal
tube. The detonation cord means 22 is then threaded through the
booster, knotted and pulled into the recession 26. The cord is used
to lower the capsule down the bore-hole. It may be desirable to
attach non-electric detonation to the booster but a detonation cord
is used to support the weight of the loaded capsule. Other support
means may be used to lower the capsule into the bore-holes. The
capsule is fitted with a handhold and a rope or other support means
may be tied to the handhold for lowering.
[0084] FIG. 6b shows a preferred embodiment of the capsule 12 in a
bore-hole 2. The capsule 12 is filled with explosive material 20
through a fill hole 33 at the top of the capsule 12. The fill hole
33 is then sealed with sealing means. Preferably, the sealing means
is a bung that can be removed after filling the capsule 12 but
produces a sufficient seal. In a preferred embodiment, the capsule
is manufactured to form one piece. The tube 23 or passage for the
detonation cord means 22 is integral with the structure of the
capsule and no sealing means is needed at the top or bottom of the
capsule 12 for the tube 22 or passage. Internal baffles may be
present to provide structural support for the capsule. The
explosive material 20 completely fills the capsule 12 and surrounds
the recess 26 at the bottom of the capsule. The shaped angle of the
angled sides 27 of between 13 to 18 degrees is provided at the
bottom of the capsule, and the sides of the capsule extend upward
and outward at the shaped angle. Above the shaped angle, the
capsule sides further extend upward and outward at a draft 30 of
between 3 to 4 degrees. The top of the capsule is provided with
handholds 32 for ease in transportation and handling. The handholds
32 also provide an alternative or secondary means to support the
capsule when lowered into the bore-hole. The capsule in the
bore-hole has a narrow clearance on each side of the capsule.
Preferably, the clearance between the capsule sides and the
bore-hole sides is 0.5 inches to allow the capsule to be easily
lowered yet still allow the maximum area of the top of the capsule
to contact the cross-section of the powder column.
[0085] The detonation means is placed in the recess and tied or
threaded with the detonation cord means. The detonation means
extends into the recess of the capsule. Preferably, the capsule
wall above the recess is thinner to allow the energy of the
detonation means to penetrate into the interior of the capsule and
come in contact with the explosives therein.
[0086] Chemistry of Nitrogen Oxide Formation in ANFO
Detonation:
[0087] The idea that Nitrogen Oxide formation can be stopped with a
shaped energy detonation is novel to the present invention.
Consequently, this disclosure reviews the chemistry for the
creation of Nitrogen Oxides from ANFO blasts and how detonation
energy solves the problem.
[0088] The balanced chemical equations that can occur between
Ammonium Nitrate and hydrocarbon (fuel oil) have been written out
to help better understand the system. In the case of an ANFO
explosion the hydrocarbon components are oxidized to form Carbon
Dioxide and water, while the Ammonium Nitrogen is oxidized to
Nitrogen. This oxidation occurs because the Nitrate Nitrogen is
reduced to Nitrogen. This balanced chemical reaction is that of
ANFO detonation:
[0089] 1) Detonation to Carbon Dioxide Formation:
4 1 chemical moles reactant moles product electrons NH.sub.4.sup.+
= 3 N.sup.-3 .fwdarw. 3 N.sup.o - 9 e- NO.sub.3.sup.- = 3 N.sup.+5
.fwdarw. 3 N.sup.o + 15 e- CH.sub.2 = 1 C.sup.o .fwdarw. 1 C.sup.+4
- 4 e- CH.sub.2 = 2 H.sup.o .fwdarw. 2 H.sup.+1 - 2 e-
[0090] It is the Nitrate ion reduction that drives the oxidation of
the hydrocarbon. That is why any Nitrate salt works to oxide a
hydrocarbon; the Nitrate Nitrogen does the work as shown by the
follow reaction between Calcium Nitrate and a hydrocarbon:
[0091] 2) Detonation to Carbon Dioxide Formation:
5 2 chemical moles reactant moles product electrons NO.sub.3.sup.-
= 6 N.sup.+5 .fwdarw. 6 N.sup.o + 30 e- CH.sub.2 = 5 C.sup.o
.fwdarw. 5 C.sup.+4 - 20 e- CH.sub.2 = 10 H.sup.o .fwdarw. 10
H.sup.+1 - 10 e-
[0092] Understanding the role of the Nitrate ion is key to
understanding the formation of Nitrogen Oxide from Ammonium
Nitrate. Even when there is insufficient hydrocarbon fuel the
chemical reaction can still be satisfied by using the Ammonium ion
of the Ammonium Nitrate as the fuel. The deflagration reaction
occurs when the Ammonium Nitrate becomes both the fuel and
oxidizer. The next three chemical equations show how the Ammonium
Nitrate can self oxidize to form Nitrous Oxide, Nitric Oxide and
Nitrogen Dioxide:
[0093] 3) Deflagration to Nitrous Oxide Formation:
6 3 chemical moles reactant moles product electrons NH.sub.4.sup.+
= 1 N.sup.-3 .fwdarw. 1 N.sup.+1 - 4 e- NO.sub.3.sup.- = 1 N.sup.+5
.fwdarw. 1 N.sup.+1 + 4 e-
[0094] 4) Deflagration to Nitric Oxide Formation:
7 4 chemical moles reactant moles product electrons NH.sub.4.sup.+
= 1 N.sup.-3 .fwdarw. 1 N.sup.o + 3 e- NH.sub.4.sup.+ = 1 N.sup.-3
.fwdarw. 1 N.sup.+2 + 5 e- NO.sub.3.sup.- = 1 N.sup.+5 .fwdarw. 1
N.sup.o - 5 e- NO.sub.3.sup.- = 1 N.sup.+5 .fwdarw. 1 N.sup.+2 - 3
e-
[0095] 5) Deflagration to Nitrogen Dioxide Formation:
8 5 chemical moles reactant moles product electrons NH.sub.4.sup.+
= 3 N.sup.-3 .fwdarw. 3 N.sup.o + 9 e- NH.sub.4.sup.+ = 1 N.sup.-3
.fwdarw. 1 N.sup.+4 + 7 e- NO.sub.3.sup.- = 3 N.sup.+5 .fwdarw. 3
N.sup.o - 15 e-- NO.sub.3.sup.- = 1 N.sup.+5 .fwdarw. 1 N.sup.+4 -
1 e-
[0096] The point being made is that deflagration is supported when
there is absence of another source of fuel to oxidize other than
the Ammonium ion. In the case of Ammonium Nitrate, the two
different valance states of Nitrogen, within the same molecule,
allow one species to be oxidized while the other is reduced.
[0097] If the Ammonium Nitrate is over oiled the reaction favors
the formation of Carbon Monoxide rather than Carbon Dioxide. This
chemical species is also unwanted in the environment but goes
without detection because it is colorless. This detonation reaction
occurs by the following equation:
[0098] 6) Detonation to Carbon Monoxide Formation:
9 6 chemical moles reactant moles product electrons NH.sub.4.sup.+
= 2 N.sup.-3 .fwdarw. 2 N.sup.o - 6 e- NO.sub.3.sup.- = 2 N.sup.+5
.fwdarw. 2 N.sup.o + 10 e- CH.sub.2 = 1 C.sup.o .fwdarw. 1 C.sup.+2
- 2 e- CH.sub.2 = 2 H.sup.o .fwdarw. 2 H.sup.+1 - 2 e-
[0099] An attempt was made to calculate the free energy for all of
the ANFO chemical reactions. The table shows a numerical
representation for each reaction .DELTA.G at a blast temperature of
4,750 degrees Fahrenheit:
10 Detonation #1 7 -1,736 kJ/kg Detonation #2 8 -1,716 kJ/kg
Deflagration #1 9 -1,584 kJ/kg Deflagration #2 10 -1,532 kJ/kg
Deflagration #3 11 -1,340 kJ/kg
[0100] Since all the possible reactions involving Ammonium Nitrate
have negative free energy the potential exists for any of the
reactions to occur. The most favored reaction has been termed
detonation #1. This reaction occurs when the molar ratio of
Ammonium Nitrate to fuel oil is stoichiometrically balanced at a 3
to 1 ratio. That molar ratio equates to adding 5.8 weight percent
fuel oil to the Ammonium Nitrate (14 grams/240 grams). If the
oxidizer to fuel ratio is less than 3/1 it will favor the reaction
called detonation #2 and produce Carbon Monoxide if the oxidizer to
fuel ratio is greater than 3/1 there will be deflagration to form
Nitrogen Oxides. Thermodynamically the formation of Nitric Oxide
and Nitrogen Dioxide are about the same but the orange cloud is
attributable to the colored Nitrogen Dioxide gas.
[0101] The fact that under oiling ANFO produces Nitrogen Dioxide
and over oiling ANFO produces Carbon Monoxide is nothing new.
Consequently, the key to not forming Nitrogen Oxides is to keep the
fuel to oxidizer ratio stoichiometric. This does not necessarily
mean just as the ANFO is mixed but also as it is ignited. Research
shows that loss of confinement is the single greatest contributing
factor to the formation of Nitrogen Oxides; consequently, loss of
confinement means loss of fuel. It is theorized that the
hydrocarbon vaporizes away from the Ammonium Nitrate when
confinement is lost and/or the hydrocarbon vaporizes at a different
rate than the Ammonium Nitrate when confinement is lost. Either
way, the resolve for the problem is to retain confinement, put in a
fuel that does not vaporize as quickly as diesel fuel or make the
reaction so fast there is no time for the fuel to escape the
oxidizer.
[0102] Thus, the reaction of the ANFO is controlled by ensuring a
hydrodynamic velocity or steady state velocity reaction through the
ANFO column, and the hydrodynamic velocity or steady state velocity
reaction is ensured by shaping the initiation detonation energy and
directing it at the entire cross-section of the ANFO column.
Thereby, the pollutants associated with a blast are controlled
through an efficient and sufficient shaped charge detonation
system.
[0103] The use of a capsule to enhance the detonation system
addresses many concerns. The capsule prevents damage to the
blasting agent that is in immediate contact with the booster. The
capsule protects up to 30 pounds of high-energy explosive from
dissolving, phase separating, dissociating into the formation
and/or becoming stoichiometrically imbalance for any other
unforeseen reason. An added benefit of the capsule is that it also
promotes confinement by not damaging the bottoms of the bore-holes.
Instead of a symmetrical sphere of blast energy emanating from an
unconfined booster, the capsule confines the booster so it does not
lose lateral energy to the adjacent bore-holes. It can be
envisioned that the shock wave from each explosion pummels the
bore-holes in the next row, causing loss of confinement. The
further back in the drilling pattern the hole is the more shock it
has received before it is detonated. This can be minimized by
confining the lateral shock energy transmitted at the bottom of
each bore-hole, and this confinement is addressed in the design of
the capsule.
[0104] The final benefit of the capsule is to shape the detonation
to ignite a blasting agent column. By shaping the detonation with
the capsule, opposed to shaping a detonation with the present art,
it is guaranteed that the charge will have correct orientation even
in a severely angled hole. The capsule provides the power of
several detonators, while directing the energy so it does not
damage the mineral strata.
* * * * *