Note: Descriptions are shown in the official language in which they were submitted.
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MODIFIED BLASTING AGENT
TECHNICAL FIELD
[0001] The present invention relates generally to blasting agents and
explosive compositions and to methods of making, using and the delivery of
such agents. More particularly, the present invention concerns a multi-
component explosive formulation which utilises waste materials which
otherwise would have been destined for landfill or high temperature
incineration. In particularly, though not exclusively, the present invention
relates to the manufacture, use and delivery of blasting agents comprising
various forms of ammonium nitrate based emulsion explosives, which have
been modified by the incorporation of waste material as a component of the
explosive.
BACKGROUND ART
[0002] Once a material has served a purpose or is a by-product of an
industrial process, it becomes a waste material. There are generally a number
of different ways in which it can be managed for its safe and environmentally
sustainable disposal. One way is separation, recycling and eventual re-use.
Another way is to manufacture the material from easily biodegradable
material; so that when the material is finally disposed of in landfill, it has
a
shorter lifespan there compared to non-biodegradable materials.
[0003] However, there are some materials which cannot be either
recycled or made of biodegradable materials. In this situation, the material
is
managed by either incinerating it or by burying in landfill where it will
degrade
only slowly. The disposing of waste material in land fill then constrains the
use
of this land, for example with some waste material such as plastics taking up
to 400 years to decay. The burning of waste material such as plastics often
requires high temperatures, so that it is difficult and costly to do. But this
process may also release harmful pollutants, often in industrial areas where
pollution may already be an issue.
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[0004] One way to address these issues is to incorporate such difficult to
recycle or degrade waste material into an explosive composition. The extreme
conditions and high temperatures generated when such an explosive
composition detonates achieves the purpose of disposing of the material, in an
analogous manner to high temperature incineration, but achieving a useful
result, and potentially at lower cost.
[0005] This approach has previously shown to be achievable for the
addition of particulate rubber with solid ammonium nitrate as disclosed in
U.S.
Patent No. 5,505,800 (Harries et al). This citation is primarily directed to
creating "low shock energy explosives" (LSEE). The rubber can be sourced
from shredding used tyres. However, the rubber particulates produced have
rough edges, which it has since been found can lead to crystallisation in the
explosive mixture when the rubber is mixed with ammonium nitrate based
emulsions. Crystallisation can prevent the mixture detonating or it will give
a
poor result.
[0006] Another attempt to use waste material in this manner, involves
mixing of energetic waste with different explosive compositions such as AN,
ANFO, water gels and emulsions, as disclosed in U.S. Patent No. 5,536,897
(Clark et al). This citation generally concerns using waste material
contaminated by rocketry fuel. The waste material is then shredded. The
presence of residual rocket fuel in the waste ensures that the waste material
contributes to the blasting performance of the final explosive. However, the
absence of such fuel material in the waste material can result in the
explosive
composition not detonating.
[0007] The presence of shredded material in an emulsion blend may
create material with rough edges and these edges can lead to crystallisation
of
a product. The crystallisation of a product can result in poor performance of
the explosive with reduced water resistance and increased risk of post blast
fumes.
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[0008] Accordingly, it would be useful to provide a solution that avoids
or
ameliorates any of the disadvantages present in the prior art, or which
provides another alternative to prior art approaches.
SUMMARY OF THE INVENTION
[0009] According to one aspect of the invention there is provided an
explosive composition comprising an aqueous emulsion of: an oxidizer
component, a hydrocarbon fuel component containing emulsifier, and fuel-type
waste material, as a bulking agent, being in a solid particulate form that
substantially lacks rough surfaces and sharp edges sufficiently so as to not
promote crystallisation of the emulsion.
[0010] Another aspect of the invention involves a method of providing an
explosive composition to a blast site having one or more blastholes for
receiving the composition, by means of a conventional mobile processing unit
(MPU), said unit comprising a truck having separate compartments adapted
for holding (a) hydrocarbon fuel component such as fuel oil, (b) the dry
oxidiser component such as dry ammonium nitrate prill, and (c) the wet
oxidiser component such as ammonium nitrate based emulsion, and the unit
having means for mixing two or more of the components from compartments
(a), (b) and (c) together and injecting the resulting mixture in a blasthole,
characterised in that compartment (b) instead holds the bulking agent in the
form of particulate waste material, and where a density reducing agent is
added to the mixture from compartments (a), (b) and (c) just prior to it being
injected into a blast hole, preferably by an auger on the MPU, and wherein the
composition is in accordance with the invention.
[0011] Yet another aspect of the invention concerns a method of blasting
soft and wet ground, which comprises injecting into one or more blast holes in
the soft and wet ground a sufficient quantity of the composition according to
the invention, and then setting off the composition.
[0012] The oxidizer component of the emulsion is generally an aqueous
solution or melt containing an oxygen-releasing salt. Preferably the oxygen-
releasing salt is selected from one or more of ammonium nitrate, sodium
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nitrate, calcium nitrate, or ammonium perchlorate, and most preferably it is
ammonium nitrate.
BRIEF DESCRIPTION OF DRAWINGS
[0013] Preferred embodiments of the invention will now be described, by
way of example only, with reference to the accompanying drawings in which:
Figure 1 is a schematic of a truck able to be used for delivering blasting
explosives, according to the present invention:
Figures 2a and 2b show photographs (not to scale) of two products (A & B) of
waste material pellet components that may be used in the invention; and
Figure 2c shows another photograph (not to scale) of product B (Figure 2b)
waste pellets showing their smooth appearance that may be used in the
invention,
Figure 2d shows a photograph (not to scale) of another product of waste
pellets, for use in the invention, and
Figures 3a and 3b, show photographs (not to scale) of comparison waste
products that do not form part of the invention, showing the roughness and
jagged nature of their surfaces, and the sharp edges and corners present.
DESCRIPTION OF EMBODIMENTS
[0014] According to the present invention, there is provided an explosive
composition, preferably comprising an ammonium nitrate (AN) type based
emulsion and a waste material as a bulking agent. The waste material is in
solid particulate form.
[0015] The waste material is fuel-type waste material, generally being
waste that can combust at high temperatures in the presence of an oxidiser.
Generally this waste may be carboniferous materials, such as waste plastics,
rubber, paper, waxes, and the like. Some suitable sources of waste material
includes nylon pellets, cardboard, polyethylene, wax, and commingled plastic
waste. Preferably the solid particulate form is in the form of pellets or the
waste material. Some other suitable sources of waste include readily
oxidisable metal, such as aluminium.
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[0016] Commingled plastics wastes, including a substantial amount of
polyethylene and similar plastics, sourced from plastics from domestic waste
collections may be utilised. These are generally finely chopped and ground to
a
powder, and the powder melted or compressed together, and then extruded to
form smooth surfaced waste plastic pellets, with rounded corners and edges.
Other materials such as commingled paper and cardboard wastes optionally
with a waxy wastes, may be shredded and compressed together to form
smooth pellets with rounded edges.
[0017] The waste material is in a granular or particulate form, preferably
having an average particle size of for 0.5 to 10 mm, and more preferable from
around 1 to 4 mm, and most preferably around 2 to 3 mm in size. These
pellets may be spherical, cylindrical, cube shaped, as square or rectangular
blocks, or irregular in shape, with generally smooth surfaces and rounded
edges.
[0018] It is also a preferred feature that the granular waste material in
particulate form should be of a similar size to the particulate solid AN prill
that
is in the blasting composition. AN prill is typically between 1 to 4 mm in
size,
and so using particulate waste material that has a similar size distribution
is
advantageous. The loading equipment is able to function effectively with the
prill particles, and so by using waste particles of a similar size, the
equipment
will also function efficiently with that.
[0019] It is also advantageous that the waste material have a density
that is not too low, as very low density additives, such as nnicroballoons or
styrene beads are known to be added as sensitising agents. Preferably the
waste particles can have a density of around 0.2 to 1.0 g/cnn3, and more
preferably around 0.4 to 0.7 g/cnn3. Ideally the waste material particles
themselves should not substantially affect the sensitisation of the blasting
emulsion.
[0020] As described below in more detail, these waste material particles
should have relatively smooth surfaces and a minimum of sharp edges,
sufficiently so, that they do not destabilise the emulsion, or do not promote
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the crystallisation of the emulsion. The stability of the emulsion can be
measured using the Rod Rating test, as described below, and preferably,
waste type pellets that provide a Rod Rating test result of 6 or higher when
mixed with an AN emulsion are ideal for the invention.
[0021] Figures 2a, 2b, 2c, and 2d, show photographs (not to scale) of
samples of some pellets that may be used in the present invention. The
sample in Figure 2a is sourced from paper and cardboard. The samples in
Figures 2b, 2c and 2d, show samples sourced from waste plastics. In these
samples, waste high density polyethylene is the major constituent. These
samples show smooth outer surfaces and rounded edges and corners. In
contrast the samples shown in the photographs for Figures 3a, and 3b show
prior art bulking agents, which have rough surfaces, with sharp edges and
corners, as well as small sharp whiskers, that destroy the emulsion, if these
were to be used in an analogous blasting composition.
[0022] The waste material has the advantage of being unwanted, and
also will often be a cost effective material to use as a consequence. Its use
also permits the waste to be removed from the environment, by being
incinerated in the explosion. Alternatively, fresh plastics material may be
used
as the source of some (or all), of the fuel type waste material. The term
"waste material" is to interpreted broadly in this invention, and while it is
preferred to use plastics waste, recycled from other applications, the use of
fresh material is also permitted, if it fulfils the same purposes. It is
intended
that recycled waste would be the primary source, due to its low cost, but at
times, there may be shortages of such material, or temporary price rises, or
unexpected increase in demand for the blasting composition, and in these
circumstances some fresh material may be substituted for the waste.
[0023] In addition, other difficult or expensive to dispose of materials
may be included in the waste, especially those that may be expensive to
dispose of apart from in a high temperature incinerator, which may be
expensive to do. Waste disposal companies may pay to have these
components added to the explosive by incorporation in the waste particulate
material, thereby improving the economic benefit of producing the blasting
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agent of the invention. Any such materials should be included if they will not
damage the environment if small quantities do not get completely incinerated.
This option is also advantageous if the blasting is of coal, for example that
is
to be burnt to produce electricity, so that any such materials will then be
burnt
in any case. Such materials are ideally carboniferous waste products that
would otherwise be incinerated, but which can instead be included in the
blasting composition. Colourants, such as waste organic dyes and similar
materials may be examples of such materials.
[0024] The oxidizer component used in the invention is preferably an
ammonium nitrate (AN) based emulsion. However, other oxidizers may be
used in place of, or in addition to, ammonium nitrate. These may include
alkaline earth nitrates such as calcium nitrate, or alkali metal nitrates such
as
sodium nitrate, and urea. Some other example may include alkaline earth or
alkali metal perchlorates such as for instance, ammonium perchlorate,
although these are not often used due to environmental concerns. Most
preferably, an aqueous solution of ammonium nitrate is used alone as the
oxidizer.
[0025] The hydrocarbon fuel component of the invention is generally fuel
oil, such as mineral or diesel oil, as used with conventional ANFO blasting
explosives in the quarrying, mining, and civil construction industries.
[0026] The hydrocarbon fuel component contains emulsifier that is a
generally any of the emulsifiers used with AN emulsion blasting explosives. A
single emulsifier or a combination of emulsifiers may be used. Some preferred
emulsifiers may be selected from the group of emulsifiers that result from
condensation reactions between PIBSA and amines or alkanolannines. Another
example of a suitable emulsifying agent is sorbitan mono-oleate, or the like.
A
preferered emulsifier may be selected from of at least one derivative of
poly(isobutylene) succinic anhydride or poly(isobutylene) succinic acid
emulsifier with diethylethanolamine or other alkanolamines. The emulsifying
agent preferably constitutes between 0.3 to 3.5% by weight of the total
composition and most preferably from 0.5 to 1.5% by weight.
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[0027] Most preferably the waste material used is such that, when mixed
with the other AN emulsion components, it does not sensitise the emulsion so
as to permit an explosion. This operates as a safety feature to prevent
accidental triggering of an uncontrolled explosion.
[0028] Ideally, the mixture of the AN emulsion and the waste material is
then sensitised, preferably at the time it is injected into a blast hole, by
the
addition of a separate sensitisation component. This sensitisation component
may be a density reducing agent. One preferred example of a suitable such
sensitisation agent is an alkali metal nitrite, and an acid, which when mixed
together produce nitrogen gas, thereby reducing the density of the explosive
blasting emulsion. Ideally, the density of the emulsion is reduced to less
than
1.15 g/cnn3 and preferably between 0.80 g/cnn3 and 1.15 g/cnn3, by selecting a
suitable quantity of sensitisation agent to mix with the emulsion.
[0029] The particulate waste material is in solid particulate form, which
has particles that substantially lack rough surfaces and sharp edges. This
feature will therefore not promote the emulsion crystallising. The absence of
sharp/rough edges does not provide a means for disruption, and therefore
crystallisation, of the emulsion droplets.
[0030] An amount of simple testing may be carried out to test if any
potentially suitable waste particulate will work in the invention. Ideally any
waste product may be utilised if it is able to be oxidised in the resulting
explosion, and will not destabilise the emulsion. Preferably also, the waste
product should not provide sensitisation to the product, to allow the blasting
agent to be sensitised separately, at the time it is pumped into the shot
holes,
by gassing the emulsion to reduce its density, for example.
[0031] Preferably, the waste particulates are in the form of pellets,
ideally pellets having rounded and smooth surfaces and edges. These pellets
may have an average particle size that is similar to that of AN prill, for
example ideally being around 2 to 3 mm in diameter.
[0032] Preferably, the waste matter comprises from 1% to 50% by
weight of the total composition, when all the components are combined, prior
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to triggering an explosion. More preferably, the waste material comprises from
10% to 40% of the composition.
[0033] The blasting agents of the invention are particularly useful in wet
soft ground. Generally an explosive composition has good water resistance if
there is 60% or greater emulsion content in the explosive. Therefore, the
explosive composition of this invention would generally be good for use in wet
ground.
[0034] Soft ground requires less energy for the ground to move. The
calculated energy of ANFO is 3.7 MJ/kg compared to one of the formulations
for the invention being 2.0 MJ/kg. The relative weight strength of that
formulation is 0.54 compared to ANFO of 1.0 and the relative bulk strength at
a density of 1.05 g/cc is 0.69 compared to 1.0 for ANFO. Therefore the energy
of this product is less than ANFO or even emulsion-ANFO blends and so is
better suited for soft ground.
[0035] Preferably the compositions of the invention are delivered to the
site where the blasting is to take place using a conventional mobile
processing
unit (MPU) truck, which is carrying the components in the sections normally
used to hold the components of traditional AN emulsion blasting agents. The
waste material is stored in and sourced from the storage container usually
reserved for the ammonium nitrate used in dry addition, ie section (b). The
explosive composition is delivered from an auger of the MPU. The density
reducing agent is ideally added to the explosive composition before the
explosive composition exits from the auger into the blast holes.
EXAMPLES
[0036] Laboratory batches of the ammonium nitrate based emulsion
were manufactured as outlined below. Table 1 lists the ingredients and
weights used to manufacture the emulsion. Other formulations also fall within
the present invention.
[0037] GENERAL EMULSION MANUFACTURE PROCEDURE
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The ingredients of the oxidizer phase were heated to 75 C to form an aqueous
solution. Separately, the ingredients of the fuel phase were mixed while
heating to 65 C. The hot oxidizer phase was then poured into the fuel phase
slowly, with agitation provided by a "Lightnin' LabmasterTM" mixer fitted with
a
65 mm "JiffyTm" stirring blade rotating initially at 600 rpm for 30 seconds.
The
crude emulsion was refined by stirring at 1000 rpm for 30 seconds, 1400 rpm
for 30 seconds and 1700 rpm until the stated viscosity was achieved. The
quantity of product prepared in each sample was 2.0 kg.
[0038] This represents a standard formulation that was used as the
emulsion source for the different blends. The formulation is shown in Table 1
below.
[0039] The emulsifier was selected from the group of emulsifiers that
result from condensation reactions between PIBSA and amines or
alkanolamines. The mineral oil used was predominantly paraffinic with some
aromatic and naphthentic constituent compounds. The emulsion was formed
with a viscosity about 25,000 cP.
[0040] Table 1 - Standard Emulsion Formulation
Oxidiser Component 94%
- Ammonium Nitrate 75%
- Water 25%
Hydrocarbon Fuel Component 6%
- Emulsifier 15%
- Mineral Oil/ Fuel Oil 85%
TABLE 1.
[0041] The waste material was supplied by "Australian Composite
Technology" company ("Plasmar") of Victoria Australia. In these examples, the
material was supplied in two versions, either in a shredded form or as a
pellet.
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The material that was shredded generally had sharp edges and this resulted in
the
destabilisation of the ammonium nitrate based emulsion due to the sharp edges
interacting
with the droplets in the emulsion and causing crystallisation. The other form,
pelletised
material, generally did not destabilise the emulsion, although this was also
dependent on the
material used.
[0042] Four materials were tested, these included (1) nylon pellets, (2)
cardboard
pellets, (3) pellets which consist of a mixture of cardboard, polyethylene and
wax, (called
"Product A") and (4) pellets which consist of comingled plastics (called
"Product B"). A
photograph (not to scale) of Product A is shown in the drawings as Figure 2a,
and of Product
B as Figures 2b and 2c, where in Figure 2b a ruler is shown, indicating that
the particles are
about 3mm in diameter. Figure 2d shows an alternate pellet of Product B of the
present
invention.
[0043] It should be noted that cardboard does contain somewhat rough
fibres and this
in theory can lead to destabilisation of an emulsion. However, if the
cardboard is pelletised,
this reduces the surface area sufficiently that some ammonium nitrate based
emulsions can
be used with it. In particular, formulations whereby the fuel phase only
consists of emulsifiers
and mineral oil with no diesel fuel oil present appear to be particularly
suitable in this
combination.
[0044] To retain the water resistance ability of the emulsion, at least
50% emulsion
should be retained in the blend, although ideally it should be 60% or greater.
Conversely the
level of waste material can be between 1 to 50%, although preferably it will
be between 10
and 40%.
[0045] A dry mix can be added to the ammonium nitrate based emulsion. The
dry mix
can consist of ammonium nitrate or a mixture of ammonium nitrate and diesel
oil (ANFO).
The dry addition, if used, comprises from 0 to 40%, by weight of the total
composition. The
blasting profile may be modified by the addition of ANFO, for example, by
providing more
heave to the blasting profile.
[0046] The waste materials preferably are pelletised so as to provide a
compact
structure devoid of any significant cavities in the material. As a result, the
waste material
provides no sensitisation and does not participate in
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the explosive reaction. Furthermore, the size of the material, approximately
3nnnn in size, means that there is decoupling between the oxidiser and fuel.
This was observed to be the case when the Product B pellets were mixed with
ammonium nitrate in a ratio of 93% by weight ammonium nitrate and 7% by
weight pellets. The product was fired in 223 mm diameter PVC pipes and the
composition failed to detonate. Only when 1.5% of the ammonium nitrate was
replaced with diesel fuel did the material detonate at low order at 1,700
nn/s.
[0047] Sensitisation may be provided by the addition of a density
reducing agent. Such density reducing agents can be any of the many
described in the art, such as glass or plastic nnicroballoons, occluded air or
by
being chemically gassed. It is preferred that the material is chemically
gassed
using alkali metal nitrites salts such as sodium nitrite or potassium nitrite.
Typically a 20 to 30% solution of sodium nitrite is added to an acidified
ammonium nitrate based emulsion. The nitrite ions are protonated and then
react with the ammonium ions to generate nitrogen gas. Generation of the gas
is normally completed within 20 to 60 minutes. The amount of the sodium
nitrite solution used determines the final density of the explosive
composition.
Density of the final explosive composition should ideally be under 1.15
gnn/cnn3 and most preferably between 0.8 to 1.15 g/cc to ensure the
composition will detonate.
[0048] Below various examples of the invention are shown. These are
examples only and do not in any way limit the invention.
[0049] COMPARATIVE EXAMPLE 1 (not this invention)
In the first example, not part of this invention, TITANTm 2000 emulsion 70%
by weight was mixed with ANFO 30% by weight. The mixture was acidified
with a 50% acetic acid solution and then a 25% by weight sodium nitrite
solution was added to the explosive composition at 0.30% weight of the total
explosive composition. This addition reduced the explosive composition from
1.32 g/cc to 1.10 g/cc. The explosive composition was loaded into 102 mm
diameter PVC pipes and detonated using a 400g Pentolite booster fitted with a
#12 strength detonator. A VOD of 4,000 m/s was recorded. The stability of
the mixture was determined to have a Rod Rating of 6 after 28 days.
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[0050] COMPARATIVE EXAMPLE 2 (not this invention)
In the second example, not part of this invention, TITANTm 2000 emulsion 80%
by weight was mixed with Product B 20% by weight and no sensitisation was
added. The mixture had a density of 1.17 g/cc and was loaded into 152 mm
diameter PVC pipes and detonated. The product failed to detonate when
initiated with a 400g Pentolite booster fitted with a #12 strength detonator.
These results indicate that the Product B does not provide sensitisation to
the
emulsion.
[0051] The following examples show that sensitisation is required.
[0052] EXAMPLE 3
In the third example, TITANTm 7000 emulsion 80% by weight was mixed with
Product A at 20% by weight. The mixture was acidified with a 50% by weight
acetic acid solution and then a 25% by weight sodium nitrite solution was
added to the explosive composition at 0.3% by weight of the total explosive
composition. This addition reduced the explosive composition from 1.27 g/cc
to 1.10 g/cc. The explosive composition was loaded into 152 mm diameter
PVC pipes and detonated using a 400g Pentolite booster fitted with a #12
strength detonator. A VOD of 3,800 m/s was recorded. The stability of the
mixture was determined to have a Rod Rating of 6 after 20 days, and the
blend breaks down after 28 days.
[0053] EXAMPLE 4
In a fourth example, TITANTm 2000 emulsion 80% by weight was mixed with
Product B 20% by weight. The mixture was acidified with a 50% acetic acid
solution and then a 25% by weight sodium nitrite solution was added to the
explosive composition at 0.2% weight of the total explosive composition. This
addition reduced the explosive composition from 1.17 g/cc to 1.02 g/cc. The
explosive composition was loaded into 152 mm diameter PVC pipes and
detonated using a 400g Pentolite booster fitted with a #12 strength detonator.
A VOD of 4,000 m/s was recorded. The stability of the mixture was
determined to have a Rod Rating of 7 after 28 days.
[0054] EXAMPLE 5
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In a fifth example, TITANTm 7000 emulsion 80 % by weight was mixed with
Product B 20 % by weight. The mixture was acidified with a 50% by weight
acetic acid solution and then a 25% by weight sodium nitrite solution was
added to the explosive composition at 0.2% by weight of the total explosive
composition. This addition reduced the explosive composition from 1.22 g/cc
to 1.03 g/cc. The explosive composition was loaded into 152 mm diameter
PVC pipes and detonated using a 400g Pentolite booster fitted with a #12
strength detonator. A VOD of 5,100 m/s was recorded.
[0055] EXAMPLE 6
In a sixth example, TITANTm 2000 emulsion 60% by weight was mixed with
Product B 10% by weight and ANFO 30% by weight. The mixture was acidified
with a 50 % by weight acetic acid solution and then a 25% by weight sodium
nitrite solution was added to the explosive composition at 0.2% by weight of
the total explosive composition. This addition reduced the explosive
composition from 1.23 g/cc to 1.12 g/cc. The explosive composition was
loaded into 152 mm diameter PVC pipes and detonated using a 400g Pentolite
booster fitted with a #12 strength detonator. A VOD of 4,500 m/s was
recorded.
[0056] EXAMPLE 7
In a seventh example, TITANTm 2000 emulsion 60% by weight was mixed with
Product B 20 % by weight and ANFO 20% by weight. The mixture was
acidified with a 50% acetic acid solution and then a 25% by weight sodium
nitrite solution was added to the explosive composition at 0.1% weight of the
total explosive composition. This addition reduced the explosive composition
from 1.18 g/cc to 1.10 g/cc. The explosive composition was loaded into 152
mm diameter PVC pipes and detonated using a 400g Pentolite booster fitted
with a #12 strength detonator. A VOD of 4,200 m/s was recorded.
[0057] EXAMPLE 8
In an eighth example, TITANTm 7000 emulsion 80% by weight was mixed with
Product B 20% by weight. The mixture was acidified with a 50% by weight
acetic acid solution and then a 25% by weight sodium nitrite solution was
added to the explosive composition at 0.1% by weight of the total explosive
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composition. This addition reduced the explosive composition from 1.22 g/cc
to 1.15 g/cc. The explosive composition was loaded into 152 mm diameter
PVC pipes and detonated using a 400g Pentolite booster fitted with a #12
strength detonator. A VOD of 4,900 m/s was recorded.
[0058] ROD RATING TESTING
Various components were tested for their stability, as indicated in Table 2.
This test involved mixing the bulking agent, ANFO and/or emulsion and then
monitoring the level of crystallisation in the emulsion as a function of time.
This was achieved by using a 10 mm glass rod that is dipped into the blend at
a 45 degree angle to a depth of approximately 20 mm to coat one side of the
glass rod with blend. The glass rod is then lightly tapped to remove excess
bulking agent, prill and/or emulsion. The glass rod is held toward a light
source with the side coated with emulsion is facing away and allowing the
light
to pass through the glass rod. The emulsion is than lightly rubbed along the
glass rod three times and the proportion of crystals are measured as follows:-
8 = no crystals; 7 = small amount of crystals; 6 = half emulsion/half
crystals;
5 = mostly crystals with some emulsion; 4 = All crystals with no emulsion.
The blend is continually rated for the proportion of crystal formation over
time
at known intervals.
[0059] EXAMPLE 9 - Stability Testing
A first test was carried out, in accordance with the invention, using TITANTm
2000 emulsion 80% by weight was mixed with Product B 20% by weight, and
gassed to a density of 0.99 g/cc, and this gave a Rod Rating of 7 after 28
days.
[0060] In contrast, tests with other substances as the waste component
gave inferior results for the stability of the emulsions. It is highly
preferred
that such emulsions must be stable for at least 14 days, and preferably are
stable for 28 days. The test for stability is preferably the Rod Rating test,
described herein, and a suitable stability will be an emulsion that has a Rod
Rating of 6 or higher, for at least 14 days.
[0061] Results for these tests are given in Table 2, below.
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Composition Density Period Rod Rating
g/cc
80% T2000 and 20% Product B 0.99 28 days 7
(Fig 2c) (invention)
80% T2000 and 20% shredded 1.03 8 hours >4
tires (Fig 3a)
10% comingled plastic shredded 0.95 1 day 4
(Fig 3b), 54% T2000 and 36%
ANFO - no gassing
5% comingled plastic shredded (Fig 1.23 1 day 4
3b), 54% T2000 and 36% ANFO -
no gassing
10% HDPE pellets, 54% T2000 and 1.25 28 days 6
36% ANFO ¨ no gassing
10% compacted vinyl, 54% T2000 1.21 5 days 4
and 36% ANFO - no gassing
TABLE 2. STABILITY TESTING
[0062] It can be seen from the microscope photographs in Figures 2b,
2c, 2d, 3a and 3b of the various waste material tested, that the material in
accordance with the invention in Figures 2b, 2c and 2d has significantly
smoother surfaces and edges, than with the shredded tyres in Figure 3a or
comingled plastics in Figure 3b. The stability tests in Table 2 show that
crystallisation occurs and the emulsion is destabilised as a result.
[0063] [0064] EXAMPLE 10 ¨ TESTING OF BLASTING
Tests were conducted in the field, using blasting compositions having as the
bulking agent the pellets in accordance with Figure 2b and 2d. A site was
selected where the natural surface was drilled with shot holes.
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[0065] Results for these tests are given in Table 3, below.
Sample Amount Hole Depth Density VOD (m/s)
(kg/hole) (m) (g/cm3)
2b 250 8 - 10 1.02 - 1.04 3000
2b 230 - 310 7 - 8 0.98 - 1.06 3800
2d 250 8 0.94 - 0.98 3900
TABLE 3
[0066] The blasting testing involved loading several holes the emulsion
according to the invention. Three shots were tested with the results as shown
in Table 3. The product detonated to high order and steady state. No fumes
were observed to originate for any of the locations loaded with the blasting
emulsion including the waste plastics bulking agents.
[0067] DELIVERY OF EXPLOSIVE COMPOSITION
Figure 1 shows a schematic of a truck used for the manufacture and delivery
of bulk explosives into blastholes at a mine. The truck (1), which is also
known
as a mobile processing unit (MPU), has three sections (10, 20, 30). The first
and smallest section (10) is usually for storage of fuel oil, which
traditionally
comprises about just 6% of the ANFO component. The second section (20) is
normally used for storage of the ammonium nitrate for dry addition. The third
section (30) is used for storage of the ammonium nitrate based emulsion.
[0068] It is preferable that the waste material is approximately
spherical
in shape and about 2 to 3 mm in size. This size and shape allows the material
to have similar flow properties to ammonium nitrate for the dry addition. As a
result, the waste material can be substituted into the second section (20) of
the truck. The lack of fines and the flowability of the waste material allow
the
second section (20) to be used for either material (the waste material pellets
or the AN prill) without significant contamination issues. Furthermore, the
lack
of sensitivity of the waste material means that even if there are some
remnants of waste material in this section (20), it will not provide a source
of
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ignition or provide fuel for the ammonium nitrate prill. Therefore the MPU
trucks can be used for either arrangement and easily re-purposed, to carry
either set of blasting components.
[0069] The MPU truck (1) has an auger (40) which allows the mixing of
the waste material with the emulsion. A density reducing agent can also be fed
into the mixture to reduce the density of the explosive composition. If the
density reducing agent is an alkaline metal nitrite salt, then a salt solution
can
be administered through an inlet port (not shown) into the auger arm (42).
The explosive composition is delivered out the auger (40) into a blast hole
(not shown).
[0070] The blasting composition according to the invention, and its
method of delivery to blastholes is particularly of benefit when blasting
soft,
wet ground, such as natural surfaces. The invention is also on benefit when
fume mitigation is of importance, as the blasts will produce a minimum about
of fumes, especially of noxious NO fumes when the nitrogen gas sensitisation
is utilised in the composition.
[0071] In this specification, unless the context clearly indicates
otherwise, the term "comprising" has the non-exclusive meaning of the word,
in the sense of "including at least" rather than the exclusive meaning in the
sense of "consisting only of". The same applies with corresponding
grammatical changes to other forms of the word such as "comprise",
"comprises" and so on.
[0072] Although the invention is described above with reference to
specific embodiments, it will be appreciated by those skilled in the art that
it is
not limited to those embodiments, but may also exist in many other forms.
INDUSTRIAL APPLICABILITY
[0073] The invention can be utilised in industries using blasting
compositions of the invention, including the mining, quarrying, and
construction industries.
