Note: Descriptions are shown in the official language in which they were submitted.
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Title: AMMONIUM NITRATE FUEL OIL BLASTING COMPOSITION
HAVING IMPROVED WATER RESISTANCE
FIELD OF THE INVENTION
This invention relates to the field of explosive compositions
comprising organic carbonaceous fuel and an inorganic oxidizing salt.
These compositions include ammonium nitrate and fuel oil (hereinafter
referred to as "ANFO") blasting explosive compositions. This invention
relates to an ANFO explosive composition having both good water
resistance and good explosive characteristics.
BACKGROUND TO THE INVENTION
Explosive compositions comprising ammonium nitrate
have been widely used throughout the world for many years. As
ammonium nitrate is not readily detonatable in and of itself, it is
typically mixed with carbonaceous fuels in order to obtain a mixture
which is detonatable. Additional compounds such as sensitizers,
densifiers, modifiers and surfactants may also be added to an ANFO
explosive composition to improve various properties of the explosive
composition including the sensitivity to detonation of the explosive, the
energy of the explosion and the flowability of the explosive composition.
Typically, explosive compositions containing ammonium
nitrate are manufactured at the location where they are to be utilized. For
example, an ANFO explosive composition could be prepared at a mine
and immediately loaded into a series of boreholes. The ANFO explosive
composition would be loaded into the boreholes (typically from about 10
to 15 holes to more than about 100 holes) over a period of days. Typically,
an ANFO explosive composition may be kept in a borehole anywhere
from one hour up to fourteen days prior to being detonated. If the
explosive is a prepackaged explosive composition, then due to shipping
and handling time, the explosive composition must be stable for
extended periods of time. A prepackaged explosive may also be stored for
an extended period of time in a borehole prior to detonation. In some
cases, the length of time between mixing the explosive composition and
detonation of the explosive composition may be up to ninety days.
After being drilled, a borehole may remain dry for an
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extended period of time. However, in some cases, water will accumulate
in boreholes, such as from the inflow of ground water. ANFO explosive
compositions are adversely affected by water penetration and water
absorption. Accordingly, if an ANFO explosive composition is loaded
into a wet borehole or a borehole into which water subsequently seeps
prior to detonation, then the ANFO explosive composition may
deflagrate or, in fact, fail to detonate.
Typically, in order to increase resistance of the explosive
composition to water, a gelling agent has been added to the explosive
composition. The gelling agent may comprise guar gum, or guar gum
and a mixture which includes, for example, sulphur and gilsonite (eg.
ADTECTM) which is added to the ammonium nitrate.
Additionally, U.S. Patent No. 5,480,500 (Richard et al)
discloses an improved water resistant ANFO explosive, having a wide
particle size distribution as well as a gelling agent as above described. The
wide particle size distribution, together with the gelling agent, increases
the resistance of the explosive composition to water. However, this
patent teaches that the addition of a gelling agent such as guar gum is
necessary to achieve a satisfactory water resistant product. The theory is
that in the wide particle size distribution, the small particles (eg.
miniprills) fill some of the interstitial spaces in the larger ammonium
nitrate particles. The gelling agent swells or hydrates upon contact with
water to form a gel. The gel acts as a barrier which reduces the absorption
of water by the ammonium nitrate particles, thus increasing the overall
water resistance of the explosive composition.
SUMMARY OF THE INVENTION
It has been surprisingly found by the present inventors that
an explosive composition having a satisfactory water resistance level
may be achieved by controlling only the particle size distribution of the
inorganic oxidizing salt and the particulate filler material, without the
addition of a gelling agent such as guar gum. More surprisingly, it has
also been found that, after exposure to water, such an explosive
composition may have a velocity of explosion greater than that of an
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explosive composition of Richard et al after being similarly exposed to
water.
In accordance with the present invention, there is provided
a blasting explosive comprising an organic carbonaceous fuel, an
inorganic oxidizing salt, and particulate filler material, wherein prior to
exposing the particulate filler material and the inorganic oxidizing salt to
the organic carbonaceous fuel, from about 15 to about 60 wt % of the
particulate filler material and the inorganic oxidizing salt are retained on
a Tyler 10 sieve, from about 15 to about 60 wt % of the particulate filler
material and the inorganic oxidizing salt are retained on a Tyler 14 sieve
and from about 20 to about 60 wt % of the particulate filler material and
the inorganic oxidizing salt are retained on a Tyler 20 sieve, the explosive
containing less than 0.1 wt % of gelling agent based on the weight of the
explosive composition.
The particulate filler material may have a different particle
size distribution from the inorganic oxidizing salt. By using the forgoing
parameters, the particle size distribution of the particulate filler material
and the particle size distribution of the inorganic oxidizing salt are
selected to increase the water resistance of the blasting explosive, without
the addition of an effective amount of a gelling agent, and preferably,
without the addition of any gelling agent. The particulate filler material
may be incorporated into the blasting explosive by mixing the particulate
filler material, inorganic oxidizing salt, and fuel oil together in any order.
The particulate filler material may be selected so as to
enhance the explosive force of the explosive composition. For example,
the particulate material may be an inorganic oxidizing salt, aluminum
flakes, aluminum granules or a mixture thereof. Preferably, the filler
material is ammonium nitrate and, most preferably, the particulate
material comprises miniprills.
Preferably, the inorganic oxidizing salt comprises
ammonium nitrate. The organic carbonaceous fuel is preferably fuel oil,
such as No. 2 fuel oil.
It is preferred that the organic carbonaceous fuel is present
in an amount from about 2 to about 10 wt % based upon the weight of
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the inorganic oxidizing salt and the fuel. More preferably, the organic
carbonaceous fuel is present in an amount from about 4 to about 8 wt
and, most preferably, the ratio of inorganic oxidizing salt to organic
carbonaceous fuel is about 94:6. The explosive composition when loaded
into a borehole is a sensitized blend of inorganic oxidizing salt, and
organic carbonaceous fuel.
The constituents of the particulate filler material preferably
have a smaller particle size than the inorganic oxidizing salt particles.
The particulate filler material will situate itself in interstitial spaces
between the inorganic oxidizing salt particles. Accordingly, the
particulate filler material decreases the voidage of the ammonium
nitrate/particulate filler material mixture, thus increasing the water
resistance of the explosive composition.
The particle size distribution of the particulate filler
material and the inorganic oxidizing salt may be mutually selected to
produce an explosive composition which is sensitized and has increased
water resistance. Alternately, the particle size distribution, and the
quantity of, the particulate filler material may be selected, in view of the
characteristics of an ANFO explosive composition, to produce an
explosive composition having increased water resistance. For example,
in one embodiment, the explosive composition may be an ANFO
explosive to which miniprills are added. The miniprills may be added to
an existing ANFO explosive composition or, alternately, the miniprills
may be added to the ammonium nitrate prior to the production of the
ANFO explosive composition.
In one embodiment, the particulate filler material and the
inorganic oxidizing salt are sized such that from about 25 to about
60 wt % of the particulate filler material and the inorganic oxidizing salt
are retained on a Tyler 10 sieve, from about 15 to about 45 wt % of the
particulate filler material and the inorganic oxidizing salt are retained on
a Tyler 14 sieve and from about 20 to about 40 wt % of the particulate
filler material and the inorganic oxidizing salt are retained on a Tyler 20
sieve.
In another embodiment, the particulate filler material and
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the inorganic oxidizing salt are sized such that from about 35 to about 50
wt % of the particulate filler material and the inorganic oxidizing salt are
retained on a Tyler 10 sieve, from about 20 to about 40 wt % of the
particulate filler material and the inorganic oxidizing salt are retained on
a Tyler 14 sieve and from about 20 to about 40 wt % of the particulate
filler material and the inorganic oxidizing salt are retained on a Tyler 20
sieve.
The ANFO explosive composition may comprise from
about 5 to about 50% miniprills, more preferably from about 5 to about
30% miniprills and, most preferably about 30% miniprills, based upon
the weight of the ammonium nitrate. This produces an explosive
composition having a wider particle size distribution and a decreased
voidage.
In another embodiment, instead of adding a particulate
filler material such as miniprills to the ammonium nitrate, ammonium
nitrate may be passed through a plurality of sieves to provide
ammonium nitrate for incorporation into an ANFO explosive
composition wherein the particle size distribution of the ammonium
nitrate has been selected to increase the water resistance of the blasting
explosive.
In a further embodiment, the grill manufacturing process,
eg. the operating parameters of the grilling tower, may be adjusted to
produce ammonium nitrate having a particle size distribution which is
selected to increase the water resistance of the blasting explosive.
According to these latter two embodiments, a blasting
explosive comprises an organic carbonaceous fuel and an inorganic
oxidizing salt, wherein prior to exposing said inorganic oxidizing salt to
the organic carbonaceous fuel, from about 15 to about 60 wt % of the
inorganic oxidizing salt is retained on a Tyler 10 sieve, from about 15 to
about 60 wt % of the inorganic oxidizing salt is retained on a Tyler 14
sieve and from about 20 to about 60 wt % of the inorganic oxidizing salt is
retained on a Tyler 20 sieve.
In a further embodiment, there is provided a method of
increasing the water resistance of a blasting explosive comprising an
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organic carbonaceous fuel, an inorganic oxidizing salt and less than 0.1 wt
of gelling agent based on the weight of the explosive composition. The
method comprises the step of incorporating particulate filler material as
part of the blasting explosive, the particle size distribution of the
particulate filler material sized to fill a portion of the interstitial spaces
between the inorganic oxidizing salt particles to increase the water
resistance of the blasting explosive.
The method may comprise the steps of mixing the inorganic
oxidizing salt and the particulate filler material to produce a first mixture
and mixing the first mixture with the organic carbonaceous fuel to form
the blasting explosive. Alternately, the method may comprises the steps
of producing a sensitized blasting explosive comprising a mixture of the
inorganic oxidizing salt and the organic carbonaceous fuel; and, mixing
this blasting explosive with the particulate filler material to produce the
blasting explosive having improved water resistance.
In a further embodiment, there is provided a method of
increasing the water resistance of a blasting explosive comprising an
organic carbonaceous fuel, an inorganic oxidizing salt and less than 0.1 wt
of gelling agent based on the weight of the explosive composition. The
method comprises selecting an inorganic oxidizing salt to reduce the
voidage in the blasting explosive and to increase the water resistance of
the blasting explosive. The method may comprise the steps of mixing
together at least two sets of inorganic oxidizing salt particles, each of the
sets having a different particle size distribution, to produce the inorganic
oxidizing salt having a particular particle size distribution.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The explosive composition of the present invention
comprises an explosive mixture of organic carbonaceous fuel and
inorganic oxidizing salts, which is substantially free of gelling agents.
The organic carbonaceous fuel may be selected from any fuel
known in the art. The fuel may be a solid (e.g. a wax) or a liquid (e.g. fuel
oil, heating oil, diesel fuel, jet fuel, kerosene, mineral oils, saturated
fatty
acids such as lauric acid and stearic acid, alcohols such as cetyl alcohol,
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corn oil, soy bean oil and the like) or a mixture of solid and liquid fuels.
Such fuels may also be supplemented with fuel-soluble ingredients such
as glucose, mannose, fructose, waxes, such as microcrystalline wax,
paraffin wax, petroleum wax and the like. Preferably, the organic
carbonaceous fuel comprises fuel oil, such as No. 2 fuel oil.
The inorganic oxidizing salt may comprise ammonium
nitrate. The ammonium nitrate is in the form of separate discrete
particles, such as prills, granules, pellets and/or fines as opposed to cast
or
powdered ammonium nitrate or solutions thereof. Particulate
ammonium nitrate suitable in ANFO blasting explosive compositions
are known in the art.
The size of the ammonium nitrate particles may be
sufficiently small to pass through a 6 TylerTM sieve but sufficiently large
so that most particles are retained on a 35 Tyler sieve. Typically,
ammonium nitrate used in explosive compositions comprises particles
wherein about 95% or more pass through a Tyler 6 sieve but are retained
on a 35 TylerTM sieve. Typically, such prills have a particle density of
from about 1.35 g/cc to about 1.5 g/cc and a poured density of 0.7 g/cc to
0.85 g/cc, preferably from about 0.75 g/cc to about 0.85 g/cc. In the trade,
such porous ammonium nitrate particles are known as prilled
ammonium nitrate.
A portion of the ammonium nitrate component may be
replaced by other inorganic oxidizer salts known in the art including
alkali metal nitrates and perchlorates (such as sodium nitrate and
potassium nitrate) or alkaline-earth metal nitrates and perchlorates (such
as calcium nitrate, magnesium nitrate and barium nitrate). These
additional components may be added in an amount from about 0 to
about 20 wt % and, more preferably from about 0 to about 15 wt % based
upon the weight of the ammonium nitrate particles.
It is preferred that the organic carbonaceous fuel is present
in an amount from about 2 to about 10 wt % based upon the weight of
the carbonaceous fuel and inorganic oxidizing salts. More preferably, the
organic carbonaceous fuel is present in an amount from about 4 to about
8 wt % and, most preferably, the ratio of inorganic oxidizing salts to
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carbonaceous fuel is about 94:6.
The explosive composition of the present invention
contains sufficient organic carbonaceous fuel so that the explosive
composition is essentially oxygen balanced, taking into consideration the
5 total oxidizing salts, fuel, sensitizers and other additives present in the
explosive. Preferably the blend has an oxygen balance more positive than
about -25% and, more preferably, in the range of about -10 to +10%.
It was previously believed that in order to prepare an ANFO
explosive composition having a satisfactory water resistance, it was
10 necessary to add a gelling agent to the explosive composition. The theory
was that the gelling agent present would swell or hydrate upon contact
with water, forming a Bell. The Bell would then act as a barrier which
reduces or prevents the absorption of water by the inorganic oxidizing
salt particles. Although the previously mentioned United States Patent
15 No. 5,480,500 discloses that the water resistance of an ANFO explosive
composition may be improved by providing a wide particle size
distribution, the inventors in that patent still believed that in order to
satisfactorily increase water resistance, it was necessary to add a gelling
agent such as guar gum to the ANFO composition. This was particularly
20 so since a preferred embodiment of Richard et al was the use of mini-
prills which are relatively small particles and, due to their relatively high
surface area, are particularly soluble.
However, the present inventors have surprisingly
discovered that, in many instances, the gelling agent may be omitted,
25 while still providing a good or adequate water resistance. The addition of
a gelling agent such as guar gum, while an organic compound,
desensitizes the explosive composition and thus significantly reduces the
velocity (and therefore the force) of the ANFO composition when
detonated. It was expected that by removing the guar gum, the explosive
30 composition would be susceptible to water damage and that the explosive
composition may deflagrate. Unexpectedly, by omitting the gelling agent,
the amount of energy available upon detonation is significantly
increased. After similar exposure to water, a higher energy explosion may
be obtained by omitting the gelling agent from the explosive composition
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of this invention as compared to the explosive composition of Richard et
al. Further, a higher energy explosion may be obtained compared with
the energy typical for standard ANFO explosive compositions not having
a wide particle distribution, while still providing an increased water
5 resistance over such prior ANFO explosive compositions which do not
contain a gelling agent.
The gelling agent will be present in an amount less than
about 0.1 wt. % based upon the weight of the explosive composition and,
preferably, the explosive composition with contain no gelling agent.
10 In one embodiment, the explosive composition further
includes particulate filler material. The particulate filler material may be
any compound which would not have a deleterious effect on the
explosive composition. Accordingly, the particulate filler material may be
an inert substance which produces a neutral effect on the force of the
15 explosion on detonation of the explosive composition. Alternately, the
particulate filler material may be an active ingredient which would act as
a fuel increasing the force of the explosive composition. Accordingly, the
particulate filler material preferably comprises an inorganic oxidizing
salt, aluminum flake, granular aluminum or mixtures thereof and, most
20 preferably, ammonium nitrate.
The particulate filler material is sized to fill at least a portion
of the interstitial spaces between the inorganic oxidizing salt particles. If
too high a percentage of the interstitial spaces are filled, then the
sensitivity of the explosive composition is reduced. Generally, the
25 particle size of typical ammonium nitrate prills which are utilized to
manufacture ANFO explosive compositions have a prill size between
Tyler 6 and 35, with over 90 wt % of the prills being retained on a sieve
size of Tyler 10 or 14. Accordingly, the particle size of a substantial
portion of the particulate filler material preferably passes through Tyler
30 14 sieve. For example more than about 50 wt % of the particulate filler
material may be retained on Tyler sieve sizes 20, 28 or less, preferably
more than about 70 wt % and most preferably about 80 - 90 wt %.
Accordingly, the particle size distribution of the ammonium nitrate and
the particulate filler material may be bimodal.
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By combining the particulate filler material and the
ammonium nitrate prills, the solid particles of the explosive
composition (namely the ammonium nitrate and the particulate filler
material) may comprise from about 15 to about 60 wt % particles which
are retained on a Tyler 10 sieve, from about 15 to about 60 wt % particles
which are retained on a Tyler 14 sieve and from about 20 to about
60 wt % particles which are retained on a Tyler 20 sieve. Preferably, from
about 25 to about 60 wt % of the particles are retained on a Tyler 10 sieve,
from about 15 to about 45 wt % of the particles are retained on a Tyler 14
sieve and from about 20 to about 40 wt % of the particles are retained on a
Tyler 20 sieve. Most preferably, from about 35 to about 50 wt % of the
particles are retained on a Tyler 10 sieve, from about 20 to about 40 wt
of the particles are retained on a Tyler 14 sieve and from about 20 to
about 40 wt % of the particles are retained on a Tyler 20 sieve.
As discussed above, the average particle size of the filler
material is generally less than the average particle size of the inorganic
oxidizing salt. The ratio of average particle size of the particulate filler
material to the inorganic oxidizing salt may be from about 0.3:1 to about
0.8:1 and, preferably from about 0.5:1 to about 0.6:1. At this level, at least
some of the particulate filler material fits within the interstitial spaces of
the inorganic oxidizing salt particles and accordingly decreases the
voidage thereof.
A particularly preferred particulate filler material comprises
miniprills. Miniprills are particulate ammonium nitrate particles
wherein, generally, at least about 95 wt % of the particles pass through a
12 Tyler screen mesh size and at least about 95% of the particles are
retained on a 28 Tyler screen mesh. The particle size of at least 95% of the
ammonium nitrate miniprills will preferably range from about 0.4 mm
to about 2.4 mm and, more preferably, from about 0.6 mm to about 1.4
mm. Miniprills typically have a high density which may range from
about 0.85 to about 1.05 g/cc, preferably, from about 0.90 to about 1.0 g/cc,
and most preferably, about 0.95 g/cc, as determined by weighing an
untapped sample of the prills in a container of known volume.
Miniprills may be prepared by conventional means, such as spraying
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molten ammonium nitrate containing very little moisture (e.g 0.1 to 0.4
wt % water and preferably less than 0.2 wt % water) at elevated
temperature (e.g. 175°C or higher) into a prilling tower countercurrent
to
cooling air which solidifies the droplets into prills which are ultimately
cooled to ambient temperature. This results in the production of
miniprills which are generally round.
The explosive composition may comprise from about 5 to
about 50% miniprills, more preferably from about 5 to about 30%
miniprills and, most preferably about 30% miniprills, based upon a
10 weight of the ammonium nitrate.
The ability of the particulate filler material to fill the
interstitial spaces of the inorganic oxidizing salt is enhanced if the shape
of the inorganic oxidizing salt particles and the particulate filler material
are complimentary. For example, if the inorganic oxidizing salt particles
15 are generally round in shape (e.g. ammonium nitrate prills), then the use
of particulate filler material which is generally round in shape, such as
miniprills prepared in a prilling tower, is preferably utilized. It will be
appreciated that if the inorganic oxidizing salt particles are of a different
shape, then the complimentary shape of the particulate filler material
20 will vary.
The particulate filler material may be incorporated into the
blasting explosive by mixing the particulate filler material, inorganic
oxidizing salt, and fuel oil together in any order. The particulate filler
material is preferably mixed with the inorganic oxidizing salt. The
25 mixture of ammonium nitrate and particulate filler material may then
be mixed with the fuel oil to produce a sensitized blasting explosive
composition of the instant invention. Alternately, the inorgaW c
oxidizing salt and the fuel oil may be mixed in any manner known in the
art to produce a sensitized blasting explosive and the particulate filler
30 material may then be added to the blasting explosive to produce the
blasting explosive of the instant invention having improved water
resistance. Alternately, the particulate filler material may be added at an
intermediate stage.
The forgoing discussion has been premised upon the
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assumption that the particulate filler material is selected based upon the
analysis of the shape and size of an existing supply of inorganic oxidizing
salt particles. This may particularly be the case, for example, where a
manufacturer of explosive compositions had an existing inventory of
5 ammonium nitrate particles but intends to produce and ANFO requiring
enhanced water resistance. In such a case, the manufacturer may
accordingly locate a source of particulate filler material, e.g. miniprills,
having the desired shape and size distribution to produce an explosive
composition according to the instant invention having improved water
resistance.
Alternately, for example if the manufacturer does not have
an inventory of ammonium nitrate, an explosive composition according
to the instant invention may be prepared by mutually selecting the size
and shape of the inorganic oxidizing salt particles and the filler material.
It will also be appreciated that an appropriate size
distribution of ammonium nitrate particles may be prepared, not by
mixing ammonium nitrate and particulate filler material together, but by
producing ammonium nitrate particles having a particle size distribution
such as that which would be obtained by mixing together ammonium
nitrate particles and miniprills. Thus ammonium nitrate having a
decreased voidage would be directly produced. This may be achieved by
screening ammonium nitrate particles to produce particles having a
particle size distribution similar to that which is achieved by mixing
conventional ammonium nitrate particles and miniprills.
In a further embodiment, the grill manufacturing process,
eg. the operating parameters of the grilling tower, may be adjusted to
produce ammonium nitrate having a particle size distribution which is
selected to increase the water resistance of the blasting explosive (e.g.
particles having a particle size distribution similar to that which is
achieved by mixing conventional ammonium nitrate particles and
miniprills).
The invention will be further understood by the following
examples which are not to be construed as a limitation on the invention.
Those skilled in the art will appreciate that other and further
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embodiments are obvious and within the spirit and scope of this
invention from the teachings of the present examples taken with the
accompanying specifications.
Example 1
The water resistance of ANFO explosive compositions
prepared in accordance with the present invention was compared with
(1) "standard" ANFO explosive compositions not containing the particle
distribution described herein, and (2) ANFO explosive compositions
containing 30% miniprills and a guar gum gelling agent. The different
explosive compositions which were prepared are set out in the Table 1
below.
The water resistance of the these explosive compositions
was measured according to the following procedure. The required density
of the explosive composition was first selected. A sufficient weight of
ANFO explosive composition was then placed into a 1,000 ml graduated
cylinder. The cylinder was gently tapped until the contents were level
with the 1,000 ml mark.
100 ml of cold tap water was poured into the centre area of
the ANFO explosive composition in the 1,000 ml graduated cylinder. The
water was gently poured over the top of the ANFO explosive
composition for a period of about 15 seconds. The ANFO explosive
composition and water was then allowed to stand for one hour. At the
end of the hour, the deepest penetration of the liquid in the 1,000 ml
graduated cylinder was measured. The results are set out in Table 1.
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TABLE 1
EXPLOSIVE MIXTURE DEPTH OF WATER
PENETRATION
cm
SAMPLE A SAMPLE B
94% NITROCHEM PRILLS/6%2B 3p
FUEL OIL
30% MINIPRILLS & NITROCHEM
PRILLS
+ 5% GUAR GUM 8 11
+7% GUAR GUM 7.5 9.0
40% MINIPRILLS & NITROCHEM7 g
PRILLS
+7% GUAR GUM
30% MINIPRILLS & NITROCHEM14 16.6
PRILLS
NO GUAR GUM
40% MINIPRILLS & NITROCHEM15 16
PRILLS
NO GUAR GUM
As can be seen, the explosive composition prepared
according to the present invention showed a significantly reduced water
resistance compared with explosive compositions containing guar gum.
In fact, the explosive composition of this invention absorbed about twice
as much water as the explosive composition of Richard et al. The
explosive composition did demonstrate an improved water absorption
compared with the explosive composition not containing miniprills
(reduced between 44% and 50%).
Example 2
The explosive energy of explosive compositions prepared in
accordance with the present invention (containing 30% miniprills) was
compared with a similar explosive composition according to Richard et
al which also contained 7% guar gum. The conditions and results are set
out in Table 2.
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TABLE 2
PRODUCT DENSITY (g/cc) ENERGY
(tapped density
in 3" - 6"
diameter tubes)
WEFF (RBS)BRISANCE
(RBS)
SOFT MEDIUM HARD
30% miniprills0.95 - 0.98 106 131 140 144
(with 7%
guar
g'um)
30% miniprills0.97-1.00 116 148 159 164
(without
guar
As can be seen, in all cases, the explosive energy of the
product without the addition of guar gum was higher than the explosive
energy of the product including guar gum.
Example 3
Additional tests were conducted to compare the velocity on
detonation of explosive compositions prepared in accordance with the
present invention (containing 30% miniprills) with similar
compositions (also containing 30% miniprills) of Richard et al which also
contained 5.5% guar gum and explosive compositions containing all
miniprills and no guar gum. All of the ANFO explosive compositions
contained 6% fuel oil and 94% ammonium nitrate. The test conditions
and results are set out in Table 3.
TABLE 3
VFT !1!'TTV n7 r n~~rn,.T n mrl,w, i__ .
30% miniprills30% miniprills all miniprills
(no guar with 5.5% no guar
Vim) guar gum g,~
Density = density =
0.94 g/cc) 1.04 g/cc
TestConditions
1 2" sch. 40 3735 - 3735 3175 - 3342 3735 - 3735
steel
1/2 1b. primer (density = 0.91
g/cc)
2 2" sch. 40 3528 - 3256 3342 - 3342 N/A
steel
90 g primer (density = 0.94
g/cc)
3 2" sch. 40 N/A 3175 - 3175 N/A
steel
1/21b. primer (0.95 g/cc)
4 1 1/2" sch. 3528 - 3174 N/A Failure
40 steel
1/21b. primer
5 1 1/2" sch. 3024 - 2886 2886 - 2886 Failure
40 steel
90 g primer
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Tests were also conducted in 3" diameter bore holes, to
compare the velocity or detonation of the different explosive
compositions. The conditions and test results are set out in Table 4 below.
TABLE 4
COMPOSITION DENSITY (g/cc)PRIMER VOD (mps)
30% miniprills0.94 1 1b. cast 3735
(no guar
30% miniprills0.95 2 x 8 Boostrite3300
(5.5%guar gum)
all miniprills1.05
1 1b. cast 3900
As can been seen from the above test results, the explosive
composition of the instant invention containing 30% miniprills without
guar gum consistently showed a higher velocity on detonation than the
composition of Richard et al which contained guar gum. Further, where
data was available, the explosive energy of the compositions prepared
according to the present invention was comparable to the explosive
energy of "standard" ANFO compositions (all miniprills).
Accordingly, it will be appreciated that the present
invention provides an ANFO explosive composition with good water
resistance and explosive characteristics.
