Note: Descriptions are shown in the official language in which they were submitted.
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ANFO Explosives Using an Emulsified Fuel Phase
Field of the Invention
The present invention is related to the explosives art, and in particular, is
related to the production of an ANFO explosive.
Descr~tion of the Related Art
Industrial blasting agents form an important component of the mining
industry. An important form of the explosives used in this industry is in the
form
of a mixture of about 94%, by weight, ammonium nitrate (AN) and about 6%
fuel oil (FO). This material is widely used in the explosives industry as a
safe,
low cost blasting agent, and is generally referred to, in the industry, as an
ANFO explosive.
While ANFO is commonly used in the industry, variations of this product
are also used to provide modified performance properties. These variations
include ANFO products wherein either the ammonium nitrate has been at least
partially replaced by other nitrate salt oxidizers, or wherein the fuel oil
has
been at least partially replaced by other fuel oil-like materials. These other
fuel
oil-like materials include materials such as other organic fuels which may be
chosen from diesel oil, distillate, furnace oil, kerosene, naphtha, waxes,
(e.g.
microcrystalline wax, paraffin wax and slack wax), paraffin oils, benzene,
toluene, xylenes, asphaltic materials, polymeric oils such as the low
molecular
weight polymers of olefins, animal oils, fish oils, vegetable oils, and other
mineral, hydrocarbon or fatty oils, and mixtures thereof. Further, these other
organic fuels may include liquid hydrocarbons which may be generally referred
to as petroleum distillate and include materials such as gasoline, kerosene,
and paraffin oils.
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These ANFO explosives with modified fuel phases may be referred to
as ANFOR explosives wherein ANFOR means ammonium nitrate - fuel oil
replacement. However, for the purposes of this document, the term ANFO is
meant to include ANFO her se, and ANFOR explosives.
ANFO explosives may also be modified by the addition of materials
such as emulsion explosives to provide a material termed as a Heavy ANFO,
or by the addition of thickening materials or chemical cross-linking materials
to
provide improved water resistance.
Generally, the production and use of these ANFO explosives is well
known in the industry. However, while these ANFO explosives are widely used,
there remains a need in the industry for improved ANFO formulations which
have improved properties over the prior art formulations.
In one known variation of interest in the present application, Stromquest
et al., in U.S. Patent No. 5,531,843, describe an ANFO explosive wherein the
fuel oil component is at least partially replaced by a material described as a
"glycol still bottom". These glycol still bottoms are described further and in
more detail, hereinbelow.
In a further variation, McNicol in U.S. Patent No. 5700970 describes an
ANFO explosive wherein the "fuel oil" component is comprised of a
homogeneous mixture of glycol still bottoms and a waste emulsion explosive.
This homogeneous mixture is then used in a conventional manner as a liquid
component in the production of an ANFO explosive.
While these formulations have some improved properties, there
continues to be further interest in developing new ANFO formulations.
Summary of the Invention
Accordingly, the present invention provides a process for the production
of an ANFO-type explosive comprising mixing an oxidizer salt, and preferably,
a nitrate oxidizer salt, with a fuel phase, characterized in that said fuel
phase is
an emulsified fuel blend which comprises an emulsified mixture of an organic
fuel and a glycol, polyglycol or glycol ether material, or a mixture thereof.
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A preferred form of a mixture of the glycol, polyglycol and/or glycol ether
is available as polyglycol still bottoms.
The present invention also provides for an ANFO-type explosive
comprising an oxidizer salt and a fuel phase, characterized in that said fuel
phase is an emulsified fuel blend which comprises an emulsified mixture of an
organic fuel and a glycol, polyglycol or glycol ether material, or a mixture
thereof.
Detailed Description of the Preferred Embodiments
The glycol, polyglycol or glycol ether materials utilized in the practise of
the present invention are preferably commonly occurring materials which can
be readily, and inexpensively obtained. These include materials having the
formula:
HO-[CR,Rz-CRsR4-OJ"-H
wherein R, to R, are each independently hydrogen or C, to C,o alkyl, and more
preferably hydrogen or C, to Cs alkyl, and 'n' is from 1 to 30 and more
preferably, from 1 to 6; or mixtures thereof and therebetween. Most
preferably,
no more than one of R, to R4 is other than hydrogen.
Accordingly, the glycol, polyglycol or glycol ether materials are
preferably a mono-, bi-, tri- etc. ethylene glycol and their methyl, ethyl,
propyl
etc. ethers. These glycol, polyglycol or glycol ether materials are readily
available from commercial suppliers. However, it is also possible to use waste
glycols or polyglycol materials, such as for example, waste automotive
antifreeze glycols, which are primarily ethylene glycol.
Also, preferably, the glycol, polyglycol or glycol ether materials utilized
is a polyglycol which contains ether and hydroxyl functionality, or is a
mixture
of both glycols and polyglycols containing a variety of ether and hydroxyl
groups. A most preferred material for this application is a "polyglycol still
bottom" material as previously described. One preferred material of the
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polyglycol bottom type is commercially available from, for example, KMCO Inc.
of the United States, under the trade name of PGB-90. This material is
described by the supplier as a mixture of glycols and polyglycols which are
available as a black liquid having a boiling point of (about) 245°C, a
pH of
6.5-9.0, a density of 1.125-1.200 and a freezing point of less than -
45°C.
These polyglycol bottoms are generally supplied containing some water
which is generally not detrimental to the process of the present invention.
These glycol still bottoms are the waste product remaining in distillation
units during the process for making marketable glycol products. Commercial
glycol producers extract ethylene glycol, diethylene glycol, triethylene
glycol
and other lower glycols from a mixed glycol starting material. The remaining
material in the distillation tower is used to extract additional lower
glycols. The
material remaining after extraction of the lower glycols is a still more
concentrated form of a waste material and is known in the industry as "glycol
still bottoms" (or polyglycol still bottoms).
A typical sample of commercially available polyglycol still bottoms
generally comprises a mixture of lower and higher glycols, polyglycols,
glycol-ethers as well as various derivatives, and may have the general
composition as set out in Table 1. However, this composition may vary from
sample to sample.
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Table 1 - Typical Polyglycol Still Bottoms Organic Component Composition'
Com onent % b wei ht
Dieth lene 3.71
I col
Dieth lene 2.41
I col but
I ether
Trieth lenecol 22.68
I
Trieth lenecol eth I ether 3.43
I
Tetraeth I col 26.66
lene
Tetraeth I col eth I ether 2.08
lene
Tetraeth I col but I ether 1.62
lens
Pentaeth I col 13.03
lene
Pentaeth I col eth I ether 2.85
lene
Pentaeth I col hex I ether 1.08
lene
Pentaeth I col but I ether 6.24
lene
Hexaeth I col 2.5
lene
Hexaeth I col but I ether 6.56
lane
He taeth I col but I ether 4.34
lene
Octaeth I col but I ether 0.8
lene
* - Polyglycol still bottoms, as received, typically comprise a mixture of
about 80°r6 organic
material and about 20% by weight of water. The amount of water can vary.
In the practise of the present invention, the polyglycol still bottoms may
be emulsified with any of the fuel phases used in the production of ANFO-type
explosives. This includes the fuel phase materials described hereinabove with
reference to the prior art, and, in particular, includes materials such as
fuel oil,
diesel fuel, vegetable oil, tall oil, motor oil, waste oils (comprising waste
motor
oil, hydraulic oil and the like), and waste emulsion explosive materials.
The level of "fuel" phase in the emulsified fuel blend may vary from 5 to
95%, by weight, more preferably from 10 to 50%, and most preferably, from 15
to 30% by weight, fuel.
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The emulsified blend is manufactured by mixing the fuel phase with the
glycol, polyglycol and/or glycol ether, optionally, in combination with an
emulsifying agent.
Suitable emulsifying agents may be chosen from the wide range of
emulsifying agents, but can include emulsifying agents such as alcohol
alkoxylates, phenol alkoxylates, poly(oxyalkylene) glycols, poly(oxyalkylene)
fatty acid esters, amine alkoxylates, fatty acid esters of sorbitol and
glycerol,
fatty acid salts, sorbitan esters, poly(oxyalkylene) sorbitan esters, fatty
amine
alkoxylates, poly(oxyalkylene)glycol esters, fatty acid amides, fatty acid
amide
alkoxylates, fatty amine, quaternary amines, alkyloxazolines,
alkenyloxazolines, imidazolines, alkyl-sulfonates, alkylarylsulfonates,
alkylsulfosuccinates, alkylphosphates, alkenylphosphates, phosphate esters,
lecithin, copolymers of poly(oxyalkylene) glycols and poly(12-hydroxystearic
acid), condensation products of compounds comprising at least one primary
amine and poly[alk(en)yl]succinic acid or anhydride, and mixtures thereof.
Among the preferred emulsifying agents are the 2-alkyl- and
2-alkenyl-4,4'-bis(hydroxymethyl)oxazolines, the fatty acid esters of
sorbitol,
lecithin, copolymers of poly(oxyalkylene)glycols and poly(12-hydroxystearic
acid), condensation products of compounds comprising at least one primary
amine and poly[alk(en)yl]succinic acid or anhydride, and mixtures thereof.
More preferably the emulsifier component comprises a condensation
product of a compound comprising at least one primary amine and a
poly[alk(en)yl]succinic acid or anhydride. A preferred emulsifier is a
polyisobutylene succinic anhydride (PIBSA) based surfactant, which are known
in the emulsion explosives industry. As an example, suitable PIBSA-based
surfactants can include the condensation product of a poly[alk(en)yl]succinic
anhydride and an amine such as ethylene diamine, diethylene triamine and
ethanolamine. Further examples of preferred condensation products may be
found in the emulsion explosive prior art.
The level of emulsifying agent is preferably from 0 to 5%, by weight of
the emulsified fuel blend. Higher levels of the emulsifier agent may be used
and may serve as a supplemental fuel for the composition, but in general it is
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not necessary to add more than 5% by weight of emulsifier component to
achieve the desired effect. Stable emulsions can be formed using relatively
low
levels of emulsifier component and for reasons of economy, it is preferable to
keep to the minimum amounts of emulsifier necessary to achieve the desired
effect. The preferred level of emulsifier component used is in the range of
from
0.1 to 3.0% by weight of the emulsion explosive.
In a particularly preferred method, however, the glycol, polyglycol, or
glycol ether and fuel mixture is self-emulsifying (that is, that no added
emulsifying agent is required). Further, it has been found that use of a
standard polyglycol still bottom material provides such a self-emulsifying
mixture. The emulsions formed using polyglycol still bottoms are generally
stable over time.
It is believed that the glycol ethers assist in the emulsification process.
Accordingly, it is preferred that the emulsified fuel blend comprise between
0.1
and 50°r6 glycol ether, more preferably between 1 and 30% glycol ether,
and
most preferably, between 3 and 15°~ glycol ether. Suitable glycol
ethers
include any of the glycol ethers listed in Table 1, or mixtures thereof. Most
preferably, the glycol ether is a methyl ether.
Emulsification of the fuel blend is achieved by standard emulsification
techniques, which can include rapidly mixing the two components until an
emulsion forms in the presence of an added emulsifying agent (when added).
The emulsification is generally conducted at ambient temperatures but can be
prepared at any suitable temperature where the polyglycol still bottoms and/or
the fuel phase remains liquid or liquifiable.
Not to be bound by theory, it is believed that polyglycol still bottoms
have improved absorption into the oxidizer salt. It is believed that this
occurs
because of their generally lower surface tension, and because, the oxidizer
salts are slightly soluble in the polyglycol still bottoms. These features
tend to
allow the emulsified fuel blend to be absorbed into the oxidizer salt more
effectively than traditional fuel oil only materials.
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It should also be noted that, typically, the emulsified fuel blend is not an
explosive, or in particular, a sensitized explosive, and thus may be safely
and
readily handled and transported.
The level of the emulsified fuel blend used in the preparation of the
ANFO explosive is dependent on the oxidizer salt chosen and the desired
properties of the explosive to be produced. If possible, it is preferable that
the
ANFO be oxygen balanced in order to minimize or avoid the generation of
noxious, gaseous by-products. Additional components may be added to the
explosive composition to control the oxygen balance of the explosive
composition.
Any one of a variety of solid oxidizer salts may be utilized in this
application. Preferred oxidizer salts in this application include alkali and
alkaline earth metal nitrates, chlorates and perchlorate, and included
materials
such as ammonium nitrate, calcium nitrate, ammonium chlorate, ammonium
perchlorate and mixtures thereof. Most preferably, the oxidizer salt is
ammonium nitrate or a mixture of ammonium nitrate with less than 25%, by
weight, of a second oxidizer salt. Further, it is preferred that the ammonium
nitrate is in grill form. It is also preferable that the ammonium nitrate
grill be an
explosive grade ammonium nitrate (EGAN), which thus, provides sufficient oil
absorption to provide an ANFO-type explosive. However, fertilizer grade
ammonium nitrate may also be used.
In particular, because of the ability of the polyglycol still
bottoms-containing emulsified fuel blend to be more effectively absorbed into
the oxidizer salt, it is possible to use higher density oxidizer salts (and
higher
density ammonium nitrate in particular) to form a higher density ANFO-type
material. Achievement of this higher density provides a method for those
skilled in the art to control the performance of the ANFO explosive.
Additionally, in order to raise the density further, it is possible to add
oxidizer salt "fines" to the mixture to replace some of the grilled material.
These "fines" are small sized particles of the oxidizer salt. Generally, their
particle size is less than 1 mm while the size of an oxidizer salt grill is
5mm or
more. Up to 50% of the oxidizer salt may be present as fines. However, more
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preferably up to 35%, and more preferably, up to 30% of the oxidizer salt is
present as "fines".
In a preferred feature, the ANFO produced according to the present
invention is produced on site and may be loaded directly into the borehole.
However, the product may also be prepared off-site, and may be shipped in
bulk, or as a packaged product, so long as the stability of the individual
composition is satisfactory for the intended use.
Further, the product prepared may then be used as part of various
known explosive compositions utilizing ANFO-type explosives. These include,
for example, Heavy ANFO, doped emulsions, and the like, which are known
within the industry.
The ANFO explosive composition may be used in combination with
other materials to vary the explosive output of the formulation. This
includes,
for example, the addition of materials such as emulsion explosives to produce
Heavy ANFO, or the addition of low weight materials such as polystyrene in
order to lower the density of the ANFO material. These materials are
commonly used in the explosives industry to vary the density and/or the
sensitivity of the explosive composition.
Examples
In the following examples, all percentages are by weight unless otherwise
stated. The primers used for detonation included P-8 and P-16 Pentalite
primers containing 8 oz. (227 g) or 16 oz. (454 g) Pentalite respectively.
Example 1
An ANFO-type explosive was prepared having the following formulation:
Ammonium nitrate (AN) 90%
Polyglycol still bottoms (PGSB) 8%
Diesel Oil 2%
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The diesel oil and polyglycol still bottoms were mixed at high speed until a
stable emulsion formed. The emulsion was then slowly added to the EGAN
prills with stirring. The resulting product was a slightly wet prill.
The product had a density of about 0.95 to 1.00 g/cc. and was
essentially oxygen balanced. The product detonated in an unconfined 75 mm
tube using a P-16 primer. It had a velocity of detonation of 1.9 km/second.
The
product was not cap-sensitive.
Example 2
A second explosive was prepared using the same procedures as in
Example 1. The explosive had the following formulation:
Ex. 2A Ex. 2B
Ammonium nitrate 85% 90%
PGSB 12% 8%
Waste Motor Oil 3% 2%
The product from example 2A had a tapped density of 1.00 g/cc and had a
velocity of detonation of 2.0 km/second in a 1 OOmm diameter container with a
P-16 primer. The product from example 2B had a tapped density of 0.97 glcc
and had a velocity of detonation of 2.0 kmlsecond in a 88mm diameter
container with a P-16 primer, 2.7 km/second in a 1 OOmm container with a P-8
primer, 2.7 kmlsecond in a 125mm container with a P-8 primer, and 1.9
km/second in a 75mm container with a P-16 primer.
Example 3
A product was prepared having the same formulation as in Example 1
with the exception that the diesel oil was replaced by tall oil. The product
had a
loose density of 0.89 g/cc and a tapped density of 0.99 g/cc. In a 75mm
container, the product detonated at 1.9 km/second using a P-16 primer.
Example 4
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Various products prepared according to the present invention were
compared to a standard ANFO product (94% ammonium nitrate with 6% fuel
oil) and to a ANFO-type product prepared using only polyglycol still bottoms
(85°~ AN with 15°~ PGSB). The products of the present invention
had a
formulation of 90% ammonium nitrate, 8% PGSB and 2% oil. The oil was
selected from vegetable oil, waste oil, diesel oil or tall oil as indicated
below.
The performance of each was compared using a P-8 primer 1 day after
preparation and 2 months after preparation.
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Product Container Diameter VOD (km/secl
mm
After 1 da
O 65 1.4
ANFO 75 2
PGSB 65 Failed
PGSB 75 Failed
Ve etable Oil 65 Failed
Ve etable Oil 75 1.2
Waste Oil 65 Failed
Waste Oil 75 Burned
Diesel Oil 65 1.1
Diesel Oil 75 1.6
Tall Oil 65 1.5
Tall Oil 75 1.9
After 2 months:
ANFO 65 1.7
Ve etable Oil 65 Burned
Ve etable Oil 75 2
Waste Oil 65 1.8
Diesel Oil 65 1.8
Tall Oil 65 1.2
Tall Oil 75 1.8
Example 5
Products having a formulation as in Example 1 were prepared using
different oils in place of the diesel oil. The densities of the product when
poured loosely into a container, and after being tapped down were compared.
Product Density in a/cc
Fuel Oil Tall Oil Waste Oil Corn Oil
Loose Packed0.92 0.93 0.89 0.89
Ta ed Down 0.98 0.97 0.94 0.94
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Example 6
The effect of replacing some of the ammonium nitrate prills with
ammonium nitrate fines was investigated using the following formulations. The
products were prepared by the method of Example 1.
Ex.6A Ex.6B Ex.6
Ammonium nitrate prills 60% 70% 65%
Ammonium nitrate fines 30 20 25
PGSB 8 8 8
Fuel Oil 2 2 2
Density - loose (g/cc) 0.89 0.87 0.86
Density - tapped (g/cc) 1.09 1.05 1.06
VOD(km/sec) - 75mm 2.4 (P-16) - -
- 65mm 1.3 (P-8) - -
Having described specific embodiments of the present invention, it will
be understood that modifications thereof may be suggested to those skilled in
the art, and it is intended to cover all such modifications as fall within the
scope of the appended claims. Additionally, for clarity and unless otherwise
stated, the word "comprise" and variations of the word such as "comprising"
and °comprises", when used in the description and claims of the present
specification, is not intended to exclude other additives, components,
integers
or steps.
