Note: Descriptions are shown in the official language in which they were submitted.
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A method for preparing a sensitised emulsion explosive.
Description:
The present invention relates to a method for preparing a sensitised water-
in-oil emulsion explosive. (Hereafter referred to as "emulsion explosive").
More
particularly, the invention relates to a method of reducing the formation of
toxic
nitrogen oxides (NOx) in the finished emulsion explosive product that is
sensitised
quickly, or gassed with nitrite at low pH values.
Background of the invention:
Emulsion explosives are well known in the art. They are fluid when formed
(and can be designed to remain fluid at temperatures of use) and are used in
both
packaged and bulk forms. They can be used as straight emulsions or be mixed
with ammonium nitrate prills and/or ANFO to form a heavy ANFO product, having
higher energy and, depending on the ratios of components, better water
resistance
than ANFO. Such emulsions can be reduced in density by the addition of voids
in
the form of hollow microspheres, other solid air entraining agents or gas
bubbles,
which materially sensitise the emulsion to detonation. A uniform, stable
dispersion
of air entraining agent or gas bubbles is important to detonation properties
of the
emulsion. Gas bubbles, if present, normally are produced by the reaction of
chemical gassing agents.
When blast-holes are loaded with a chemically gassed or sensitised
emulsion explosive, it is important to have the correct part of the blast-hole
unloaded to prevent fly-rocks and possible damage to man and properties. If
the
gassing process is slow, it is difficult to know when to stop the loading
process and
how much the emulsion will expand upwards in the blast-hole, in order to have
the
correct unloading part of the blast hole.
On the other hand if the gassing process is quick, and of the same order as,
or lower than the time it takes to load a blast-hole, it is easy to find the
correct
loading-height, and the stemming of the blast-hole can be accomplished at
once.
Also in tunnel blasting, is it important to have a gassing and expansion
process
that is as quick as possible, especially when loading upright blast-holes.
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A common sensitising agent is nitrite, which generates nitrogen bubbles in
the emulsion when nitrite reacts with ammonium, preferably in the presence of
an
accelerator.
The reaction between these components may be illustrated as follows:
NH4+ + NO2 - N2 + 2 H20
However, when an emulsion explosive gases rapidly, using nitrite as the
gassing
component and at low pH, there will often be formation of some toxic nitrogen
oxide beside the nitrogen gas as the main gas-product.
Gassed emulsion explosives can under certain conditions fall or slide out of a
blasthole and thereby loose some of the sensitising gas. In bench loading,
some
sensitised emulsion may collapse and loose gas, especially when stemming is
applied to a blast-hole with a low-density emulsion explosive. Under poor
ventilation conditions, people can be exposed to dangerous NO2 levels, when
working close to a sensitised emulsion explosive loosing its sensitising gas,
both in
the field and at laboratory work. NO2 is very toxic gas and has a threshold
limit in
Europe as low as 2 ppm.
The present invention provides a new method for quickly sensitising an
emulsion explosive where the toxic NOx-gas will be reduced or eliminated
during
the gassing process.
Prior art technology:
A process and apparatus for the manufacture of emulsion explosive
components is disclosed in US Patent No. 6,165,297. This patent also refers to
different accelerators, e.g. in claim 12, where thiourea, thiocyanate, iodide,
cyanate, acetate and combinations thereof are mentioned.
In accordance therewith the present invention provides a method for
preparing a sensitised emulsion explosive in a blast hole or a package,
wherein
a) a fuel phase and
b) an oxidizer solution containing ammonium species and oxidizer salt, and
having a pH in the range 0-3,
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are emulsified to form an emulsion, which is subjected to gassing by mixing it
with
c) a gassing solution containing inorganic nitrite,
in the presence of urea as gassing accelerator,
and wherein the emulsion explosive is delivered to a blast hole or a package
by
means of a loading tube or hose, allowing the gassing to take place at the end
of
said tube or hose.
The pH should be adjusted to a value in the range of 0-3, preferably by
means of an organic acid having at least 3 carbon atoms, such as citric and/or
tartaric acid. A preferred pH is in the range of 0,4-2,0 in particular about
1.
This means that the oxidizer solution of the emulsion normally should
contain the organic acid such as citric acid in a concentration of from 0,2 to
5 %
preferably from 1,5 to 3%.
When urea is used as a gassing accelerator there is practically no
generation of nitrous gasses (NOx), or any other toxic gases that might be
produced using other gassing accelerators.
Urea has been used or suggested for use in water-bearing blasting agents
of the emulsion or water-gel type and in ANFO blasting agents. For example,
U.S.
Pat. No. 5,159,153 discloses the use of urea in the oxidizer salt solution
phase of
an emulsion blasting-agent for purposes of stabilizing the blasting agent
against
thermal degradation in the presence of reactive sulfide and pyrite ores. U.S.
Pat.
No. 4,338,146 discloses the use of urea as an additive in a cap-sensitive
emulsion
explosive in an amount of less than 5% by weight. U.S. Pat. No. 4,500,369
discloses the use of urea in an emulsion blasting-agent to lower its
crystallization
temperature. U.S. Pat. No. 3,708,356 discloses the use of urea to stabilize
ANFO
against reaction with pyrite ores.
U.S. Pat. No. 5,608,185 discloses a method of reducing the formation of
toxic nitrogen oxides (NO<sub>x</sub>) in after-blast fumes by using an emulsion
blasting
agent that has an appreciable amount of urea in its discontinuous oxidizer
salt
solution phase. Thus, the urea in said patent is used for reducing the amount
of
nitrogen oxides formed in after-blast fumes, while according to the present
invention the urea is used together with the gassing agent in connection with
the
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sensitising of the emulsion explosive, to avoid the formation of NOx in the
sensitised emulsion before it is detonated.
USP 5,972,137 relates to the gassing of an emulsion explosive, but the
purpose is not to reduce the amount of NOx in the sensitised emulsion, but to
use
an organic solvent for the gassing agent in order to minimize the total amount
of
water in the explosive composition, and thereby increasing the energy of the
explosive. A relative high pH is used, and the gassing agent is a combined
hose
lubricant and gassing agent. The gassing accelerator is added to the fuel
phase
and will extract over to the oxidizer solution as the emulsion is formed.
Rapid
gassing using a low oxidizer pH is not possible with this patent as urea
(gassing
accelerator) will decompose under these conditions.
In USP 3,711,678 a gassing technique is also described, but in this case
the gassing takes place at very early stage, namely at the stage where the
initial
emulsion is formed. The process of this patent cannot be used for rapid
gassing,
as the emulsion has to be formed at an elevated temperature of about 60 C, and
under these conditions trying to use a low pH will cause the emulsion to gas
within
seconds, as shown in the present invention, see example 14 below. Rapid
gassing
of an emulsion can only be done by using an end of hose mixing device,
otherwise
the emulsion will loose its sensitising gas in the emulsion pump and in the
loading
hose.
The sensitised emulsion explosive prepared according to the present
invention is delivered to a blast hole or a package (cartridge) by means of a
loading tube or hose, which may suitably be lubricated by lubricating water to
reduce the friction of the emulsion explosive through the tube or house.
Suitably,
urea may be added to said lubricating water. It is also possible to add
further
desired substances to the lubricating water, and examples of such other
substances are organic acids to reduce the pH value to the necessary level and
also energy and flame reducing agents.
In the gassing solution the concentration of urea should preferably be from
10 to 45%, in particular from 20 to 30% by weight. In the lubricating water
the
concentration of urea should preferably be from 5 to 50%, preferably from 20
to
40% by weight.
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In the state of the art, such as USP 6,165,297 mentioned above, urea is
added in small quantities in the gas forming composition. In the referred USP
6,165,297 it is necessary to mix two different gassing ingredients just prior
to the
gassing process, as the gassing ingredients in said patent otherwise will self
gas.
s USP 6,165297 (see col.12; line 8-31) describes the gassing process in
Example 3
as follows: "An aqueous solution sodium nitrite (SNI) and urea was stored in
one
container of the apparatus of the current invention, while an aqueous solution
of
the ammonium nitrate (AN) and urea was stored in a separate container. The SNI
solution and AN/urea solution were pumped from their containers through
separate conduits into a small tank and were mixed together using a rapidly
turning propeller. The premix so formed was then injected into the water-in
oil
,emulsion just prior to the water-in-oil emulsion passing through a series of
static
mixing elements, which evenly distributed the components suitable for gas
formation throughout the water-in-oil emulsion. The water-in-oil emulsion
1s incorporating the components passed through the remaining length of
stainless
steel conduit into a flexible loading hose, the other end of which was loaded
in a
blasthole.
The blasthole was filled with the combinations of water-in-oil emulsions and
mixed components. The mixed components started to react after about 30
seconds and it took about 30 minutes for the gassing reaction to be completed.
The density of the gassed water-in-oil emulsion was 1,00 g/cc compared with
1,38
g/cc for the ungassed water-in-oil emulsion. The blasthole was detonated
successfully. USP 6,165,297 describes a gassing process very different from
that
of the present invention. Although USP 6,165,297 and the present invention
both
comprises the use of urea, these two patents are very different:
= USP 6,165,297 gasses slowly (typical 30 min. to reach a density of 1,05
g/cc), and is not concerned about the NOx that might be formed in the
gassing process itself.
= The goal with the present invention is rapid gassing, and at the same time
to eliminate or minimize the NOx formed in the gassing process. This is
achieved by using an organic acid in the oxidizer solution, where citric acid
and/or tartaric acid are the preferred organic acid.
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= USP 6,165,297 mixes two gassing ingredients just prior to injection to the
emulsion. This premix is self-gassing, and the water-in-oil emulsion itself
has a relatively high pH of 4,2 (See co1.10, line 45), and the ammonium
species in the oxidizer solution do not (or very slowly) react directly with
the nitrite in the gassing solution.
= In the present method, a urea solution is used as a loading hose lubricant,
and is mixed with the emulsion in a spray nozzle at the end of the loading
hose. The pH of the water-on-oil emulsion is very low (less than 3). The
gassing component can alternatively be added as a string in the centre of
the emulsion (See W099/14554) or be blended with a static mixer or
in a mechanical mixer just before the emulsion enters the ioading hose.
USP 5,608,185 uses urea as a component in the discontinuous oxidizer salt
phase
to reduce the formation of nitrogen oxide in the after-blast fumes. This
patent is
also very different from the present invention for the following reasons:
= USP 5,608,185 uses urea to reduce after-blast fumes.
= The present invention uses urea to eliminate Qre-detonation nitrogen oxides
that can generate during rapid gassing.
= USP 5,608,185 uses from 5 to 30% urea. Preferably the urea is dissolved in
oxidizer salt solution.
= The present invention uses urea as an additive to the water lubrication
solution, which is necessary to use, in order to pump the emuision through
a long and thin loading hose. At the end of the loading hose (or conduit)
the emulsion and the lubrication solution are mixed in a mixing nozzle.
= According to the present invention the goai is to sensitise the emulsion
rapidly, and therefore gas rapidiy. In order to gas rapidly the emulsion
should have a low pH in the oxidizer solution, and in this case is it
impossible to have urea as a component in the oxidizer solution, as urea
will decompose slowly in acid solution. Under these conditions urea will
decompose to carbon dioxide and ammonia, which raises the pH and
slows down the gassing rate.
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USP 5,159,153 also describes the use of urea in water-in-oil emulsion
explosives,
but said patent is also very different from the present invention for the
following
reasons:
= In USP 5,159,153 urea is added with the purpose of stabilizing the emulsion
against thermal degradation with reactive sulfide/pyrite ores. So the
purpose with this patent is completely different than in USP 5,08,185 and
the current patent application where the purpose is to reduce after blast
fumes and to eliminate NOx during the gassing-process (or sensitivitation)
of the emulsion respectively.
= In USP 5,159,153 urea is added from 5-20% preferably dissolved in the
oxidizer phase, but may also be added as a powdered or solid phase.
= In the present method, urea is dissolved in the water-I u bri cation
solution,
and mixed with the emulsion at the end of the conduit, where urea acts as
a gassing accelerator and minimizes or reduces the NOx normally formed
during a rapid gassing process, or alternatively urea is used in the gassing
solution or in both the gassing solution and the water lubrication solution.
Several patents describe the use of gassing accelerators to accelerate the
rate of gas generation by the chemical gassing agent. USP 4,960,475; USP
5,017,251; USP 5,076,867;USP 5,346,564 and USP 6,165,297 all mention the
use of gassing accelerators, but none of them mentions urea as a gassing
accelerator.
USP 6,165,297 is mentioning gassing accelerators such as thiocyanate
salts, iodides, sulphanic acid and its salts or thiourea. (Se column 3, line
11-12)
In these patents it most common to add the gassing accelerator to the oxidizer
solution of the water-in-oil emulsion, or add the gassing accelerator in the
gassing
solution.
In the present method urea is used as a gassing accelerator, and is added
to the water lubrication solution or to the gassing solution. Alternatively
urea can
be added both to the water lubrication solution and to the chemical gassing
solution.
USP 4,273,147 and USP 4,259,977 describe a method of reducing the
pumping pressure in conduits using a lubricant fluid that moves in an annular
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stream around the emulsion. The lubricating fluid comprises a solution of
ammonium nftrate, or an aqueous salt solution wherein the salt of the said
lubricating fluid corresponds to the major salt present in the explosive
emulsion.
The main purpose with these two patents is to lower the pumping pressure of an
s emulsion in a conduit, and to prevent the conduit to plug up during
interruption of
the pumping.
In the present invention lubricating fluid does not contain a salt present in
explosive emulsion, and the main presence of urea in the lubricating fluid is
not to
lower the pumping pressure, but to eliminate or reduce the amount of NOx
created
during the gassing process with nitrite.
Conclusion:
The purpose with this patent is to be able to chemically gas an emulsion
explosive rapidly both at low and high temperatures without creating NOx
during
1s the gassing process. To accomplish this it is necessary to have an emuision
with a
low pH and to use a gassing accelerator. It has surprisingly been found that
by
lowering the pH by using an organic acid such as citric acid practically
eliminates
the production of NOx during the gassing process, when urea is used as a
gassing
accelerator.
According to one aspect of the present invention, there is provided a
method for preparing a sensitised emulsion explosive in a blast hole or a
package, wherein (a) a fuel phase and an oxidizer solution, comprising
ammonium species and oxidizer salt, are emulsified to form an emulsion, and
(b)
said emulsion is subjected to gassing by mixing it with a gassing solution
comprising inorganic nitrite in the presence of urea as gassing accelerator,
and
wherein: the emulsion is delivered to the blast hole or the package by means
of
a loading tube or hose, allowing the gassing to take place at the end of said
tube
or hose, the oxidizer solution has a pH value in the range 0-3 and comprises
one
or more organic acid(s) having at least three carbon atoms, and urea is
present
in the gassing solution and/or is present in a lubrication fluid added to the
loading tube or hose.
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The invention comprises the addition of urea as a gassing accelerator in the
gassing solution, andlor using urea as a gassing accelerator in the
lubrication fluid.
It is also surprisingly found that by lowering the pH of the oxidizer solution
in the
emulsion by using citric acid (CA), completely eliminate NOx during the
gassing
process. As can be seen from the given examples an increased amount of CA
gives a decreasing pH, but also reduced NOx as the amount of CA is increased.
CA is found to be particularly advantageous and at a level of 2% CA, where the
NOx from the gassing process is completely eliminated. The gassing rate is
also
increased as the amount of CA is increased. Also tartaric acid (TA) was found
to
,o have a positive effect on the reduction of NOx in the gassed emulsion.
On the other and hand, if CA is replaced by acetic acid (HAc), this also
gives increased gassing rate, but it is also gives more NOx. And as the amount
HAc is increased, more NOx are produced, so HAc does not have the same
advantageous effect as CA and TA.
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It was also surprisingly found that the gassing rate at these low pH
emulsions also increased by replacing some ammonium nitrate (AN) in a straight
AN emulsion (see example 16), by other inorganic nitrates like sodium nitrate
(see
exampies 6-8 and t0-15) and calcium nitrate. (Se example 17). The NOx
produced during the gassing process was still kept at a very low level.
To illustrate that urea acts as a gassing accelerator as claimed in this
current invention, the gassing rate using different gassing accelerators in
the
gassing composition were tested. The NOx level in the finished sensitised
ernuision explosives were also measured.
All different gassing compositions had the same level of 15% sodium nitrite
and were tested at a 1% level in the given standard emulsion.
The percentage values recited herein for the components of the oxidizer
solution
represent percentages by weight.
EXAMPLE 1(not according to the invention)
A standard water-in-oil emulsion of the following composition was preparetl
for use
in the foliowing examples:
Oxidiser soiution:
94 wt % comprising:
Ammonium nitrate 72,5 wt %
Sodium nitrate 9,8 wt %
Water . 15,7 wt 10
Citric acid 2,0 wt %
pH of the oxidiser was measured to 0,98
i=uei Phase :
6 wt % comprising:
A hydrocarbon oil and emuisifier mix
The emulsifier was of a polymeric type.
The emulsion was prepared by slowly adding a stream of oxidiser solution
to the fuel phase, with rapid stirring to form a homogeneous water-in-oil
emulsion.
Both phases kept at an elevated temperature of 80 oC during the preparation of
the emuision. The resulting standard emulsion was left for a day to cool down
to
room temperature,
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The foilowing components in aqueous solution were combined to provide
the following gas forming composition:
Sodium nitrite 15,0 %
s Water 85,0 %
1,0 % of this gas forming composition was added to the water-in-oil
emuision. The blend was mixed for 40 seconds, and transferred to a 160 cc
plastic
cup. The emulsion was filled to the top of the cup, and levelled off using a
stiff,
plane blade. As the emulsion in the cup gassed, the emulsion expanded beyond
the top of the cup, and was scraped off to en even level. The levelled off cup
was
weighted every minute and the weight of the emulsion explosive was recorded.
The density of gassing emulsion explosive was found by dividing its weight by
the
cup volume of 160 cc. When the emulsion explosive had reached its final
density,
1s the cup with the sensitised emulsion explosive was transferred to self-made
glove-
box. The glove-box contained a volume of 100 litres, and was equipped with a
small 12-volt fan for mixing the air in the box, and a Multi-gas monitor (pm-
7400)
from Metrosonics Inc. The box had a removable Plexiglas top, and the mounted
gloves enabled one to use a spatula to stir out the sensitising gas from the
emulsion.explosive. The fan efficiently mixed the sensitising gas with the
total of
100 litres of air in the box, and the Multi-gas monitor measured the NOx
concentration. For this particular blend, no accelerator was used in the gas
forming composition, and the gassing rate was found to be more than 3 hours,
and
a concentration of 10 ppm NOx was measured in the glove-box.
EXAMPLE 2 (not according to the invention)
The following gassing component was made for this experiment:
Sodium Nitrite 15 %
Sodium thiocyanate 30 %
Water 55 %
*Trade-mark
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1% of this gassing component was added to the standard emulsion, and
mixed for 40 seconds. The gassing rate was recorded, and it was found that
this
emulsion composition reached a density of 0,80 g/cc in 6 minutes, and the
final
cup density ended at 0,68 g/cc. When the gas was stirred out of the emulsion
in
the glove-box, the Multi-gas monitor from Metrosonics showed a NOx
concentration of 130ppm.
EXAMPLE 3 (not according to the invention)
The following gassing component was made for this experiment:
Sodium Nitrite 15 %
Thiourea 5 %
Water 80 %
1% of this gassing component was added to the standard emulsion, and
1s mixed for 40 seconds. The gassing rate was recorded, and it was found that
this
emulsion composition reached a density of 0,80 g/cc after 55 minutes, and
ended
up with a final cup density of 0,75 g/cc. after 2 hours. When the gas was
wiped
out of the emulsion in the glovebox, the Multi-gas monitor from Metrosonics,
showed a NOx level of 300ppm.
EXAMPLE 4 (not according to the invention)
The following gassing component was made for this experiment:
Sodium Nitrite 15 %
Potassium iodine 30 lo
Water 55 %
1% of this gassing component was added to the standard emulsion, and
mixed for 40 seconds. The gassing rate was recorded, and it was found that
this
emulsion composition reached a density of 0,80 g/cc after 70 minutes, and
ended
up with a final cup density of 0,75 g/cc. after 2,5 hours. When the gas was
wiped
out of the emulsion in the glovebox, the Multi-gas monitor from Metrosonics,
showed a NOx level of 22ppm.
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EXAMPLE 5 (not according to the invention)
The following gassing component was made for this experiment:
Sodium Nitrite 15 %
Ammonium sulphate 30 %
Water 55 %
1% of this gassing component was added to the standard emulsion, and
mixed for 40 seconds. The gassing rate was recorded, and it was found that
this
emulsion composition reached a density of 0,80 g/cc after 160 minutes. When
the
gas was stirred out of the emulsion in the glovebox, the Multi-gas monitor
from
Metrosonics, showed a NOx concentration of 33ppm.
EXAMPLE 6 (according to the invention)
The same emulsion and the same type and amount of gassing component
as in EXAMPLE 1 were added. In addition 2% of lubricating solution, containing
50% urea and 50% water, was also added. This was done by first blending in the
gassing component for 10 seconds, and then mixing in 2% of the lubricating
water
in 40 seconds. The gassing rate was measured. It was found that this emulsion
composition gassed to density of 0,80 g/cc in 9 min., and reached a final
density of
0,68 g/cc. When the sensitising gas was stirred out of the emulsion in the
glove
box, no NOx could be detected. This example shows that urea both acts as an
accelerator and eliminates the NOx formation during the gassing process.
EXAMPLE 7 (according to the invention)
The following gassing component was made for this experiment:
Sodium Nitrite 15 %
Urea 42%
Water 43 %
1% of this gassing component was added to the standard emulsion and
mixed for 40 seconds. The gassing rate was recorded, and it was found that
this
emulsion composition reached a density of 0,80 g/cc after 9 min., reaching a
final
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cup density of 0,68 g/cc. When the gas was stirred out of the emulsion in the
glovebox, the Multi-gas monitor from Metrosonics could not detect any NOx.
EXAMPLE 8 (according to the invention)
The standard emulsion and the same type and amount of gassing
component as in EXAMPLE 7 were added. In addition 2% of lubricating water
containing 50% urea, was also added. This was done by, first blending in the
gassing component for 10 seconds, and then mixing in 2% of the lubrication
water
for 40 seconds. The gassing rate was measured. It was found that this emulsion
composition gassed to density of 0,80 g/cc in 9 min., and reached a final cup
density of 0,68 g/cc. When the gas was stirred out of the emulsion in the
glove
box, no NOx could be detected.
EXAMPLE 9 (not according to the invention)
The following gassing component was made for this experiment:
Sodium Nitrite 15 %
Urea 42 %
Water 43 %
__ 1 % of this gassing component was added to an emulsion where the 2% of
citric acid was replaced by 2% of Acetic acid (60%). The gassing component and
this emulsion was blended for 40 seconds. The gassing rate was recorded, and
it
was found that this emulsion composition reached a density of 0,80 g/cc after
40
min. When the gas was stirred out of the emulsion in the glovebox, the Multi-
gas
monitor from Metrosonics detected a NOx-concentration of 45 ppm.
EXAMPLE 10 (according to the invention)
The following gassing component was made for this experiment:
Sodium Nitrite 15 %
Water 85 %
And the following water lubrication solution was made:
Water 60 %
Urea 40%
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1% of this gassing component was added to the standard emulsion
together with 2% of the water lubrication solution, and mixed for 40 seconds,
at
temperature of 50 C. The gassing rate was recorded, and it was found that
this
emulsion composition reached a density of 0,80 g/cc after I min., and reaching
a
final cup density of 0,68 g/cc. after 3 min. When the gas was stirred out of
the
emulsion in the glovebox, the Multi-gas monitor from Metrosonics could not
detect
any NOx.
EXAMPLE 11 (according to the invention)
The following gassing component was made for this experiment:
Sodium Nitrite 15 %
Urea 42%
Water 43 %
1% of this gassing component was added to a standard emulsion
containing 0,3% citric acid in the oxidizer solution, and was mixed for 40
seconds,
at room temperature. The gassing rate was recorded, and it was found that this
emulsion composition reached a density of 0,80 g/cc after 180 min. When the
gas
was stirred out of the emulsion in the glovebox, the Multi-gas monitor from
Metrosonics detected a NOx-concentration of 2,5 ppm.
EXAMPLE 12 (according to the invention)
The following gassing component was made for this experiment:
Sodium Nitrite 15 %
Urea 20 %
Water 65 %
And the following water lubrication solution was made:
Water 50 %
Urea 50%
1 lo of this gassing component was added to a modified standard emulsion
together with 2% of the water lubrication solution, and mixed for 40 seconds,
at
temperature of 23 C. The modified standard emulsion had 3% of citric acid in
the
oxidizer solution, instead of 2% as described in example 1. The pH-value on
this
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oxidizer solution was 0,65. The gassing rate was recorded, and it was found
that
this emulsion composition reached a density of 0,80 g/cc after 9 min. When the
gas was stirred out of the emulsion in the glovebox, the Multi-gas monitor
from
Metrosonics detected a NOx -concentration of 2,9 ppm.
5
EXAMPLE 13 (according to the invention)
The following gassing component was made for this experiment:
Sodium Nitrite 15 %
Urea 42%
10 Water 43 %
And the following water lubrication solution was made:
Urea 42%
Citric acid 14 %
Water 44 %
1% of this gassing component was added to a standard emulsion
containing 0,8% citric acid in the oxidizer solution, and was mixed for 10
seconds.
Then 2% of the water lubrication solution was added, and mixed for 40 seconds,
at
room temperature. The gassing rate was recorded, and it was found that this
emulsion composition reached a density of 0,80 g/cc after 15 min., with a
final cup
density of 0,76 g/cc. after 20 min. When the gas was stirred out of the
emulsion in
the glovebox, the Multi-gas monitor from Metrosonics detected a NOx-
concentration of 0,2 ppm .
EXAMPLE 14 (according to the invention)
The following gassing component was prepared for this experiment:
Sodium Nitrite 15 %
Urea 20 %
Water 65 %
And the following water lubrication solution was made:
Water 70 %
Urea 30%
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16
These solutions were filled into the containers of Dyno's SME (Site Mixes
Emulsion) truck. The SME-truck produced an emulsion equal to the one given in
EXAMPLE 1, except that the fuel-phase contains sorbitan mono-oleate (SMO) as
an emulsifier rather than a polymeric type. The emulsion is produced at a
temperature of about 80 C, pumped through an 80 meter long loading hose, into
the borehole.
0,8% of the gassing component was added to centre of the emulsion as
described in PCT/NO/00275, and 2% of the water lubrication solution was used
for
lubricating the loading hose. A mixing nozzle was mounted at the end of the
loading hose. 100 kg/min was pumped through the loading hose into the
boreholes, and the gassing component and the water lubrication solution were
mixed with the emulsion at the end of the loading hose. This blend was loaded
into
40 blastholes off a diameter of 102mm. The whole round was successfully shot.
During the loading process the gassing rate was recorded in a small density
cup,
1s and it was found that this emulsion gassed completely within 10 seconds,
reaching
a final cup density of 0,80 g/cc. When the gas was stirred out of the emulsion
in
the glove-box, the Multi-gas monitor from Metrosonics could not detect any NOx
.
EXAMPLE 15 (according to the invention)
The following gassing component was prepared for this experiment:
Sodium Nitrite 15 %
Urea 20 %
Water 65 %
And the following water lubrication solution was made:
Water 50 %
Urea 50%
1% of this gassing component and 2% of the water lubrication component
was added to a standard emulsion where the 2% of citric acid was replaced by
2%
of Tartaric Acid. The oxidizer solution had a pH of 0,55 before the emulsion
was
made. The gassing solution plus the water lubrication solution were added to
the
emulsion was blended for 40 seconds. The gassing rate was recorded, and it was
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17
found that this emulsion composition reached a density of 0,80 g/cc after 6
min.
When the gas was stirred out of the emulsion in the glovebox, the Multi-gas
monitor from Metrosonics detected a NOx-concentration of 2,1 ppm.
EXAMPLE 16 (according to the invention)
The following gassing component was prepared for this experiment:
Sodium Nitrite 15 %
Urea 20 %
Water 65 %
And the following water lubrication solution was made:
Water 50 %
Urea 50%
1% of this gassing component and 2% of the water lubrication component
were added to an emulsion prepared as described in EXAMPLE 1 using an
oxidizer solution of the following composition:
Ammonium nitrate 55 %
Calcium nitrate (Hydro TQ) 30 %
Water 13%
Citric acid 2 %
and 6,5 % of the polymeric fuel phase. The pH of oxidizer solution was
measured
to 0,0 before the emulsion was made. The gassing solution plus the water
lubrication solution were added to the emulsion, and blended for 40 seconds.
The
gassing rate was recorded, and it was found that this emulsion composition
reached a density of 0,80 g/cc after 4 min. When the gas was stirred out of
the
emulsion in the glovebox, the Multi-gas monitor from Metrosonics detected a
NOx-
concentration of 0,0 ppm.
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EXAMPLE 17 (according to the invention)
The following gassing component was prepared for this experiment:
Sodium Nitrite 15 %
Urea 20 %
Water 65 %
And the following water lubrication solution was made:
Water 50 %
Urea 50%
1% of this gassing component and 2% of the water lubrication component was
added to an emulsion prepared as described in EXAMPLE I using an oxidizer
solution:
Ammonium nitrate 82 %
Water 16%
Citric acid 2 %
and 5,6 % of the polymeric fuel phase. The pH of the oxidizer solution was
measured to 0,75 before the emulsion was made. The gassing solution plus'the
water lubrication solution were added to the emulsion, and blended for 40
seconds. The gassing rate was recorded, and it was found that this emulsion
composition reached a density of 0,80 g/cc after 18 min. When the gas was
stirred
out of the emulsion in the glovebox, the Multi-gas monitor from Metrosonics
detected a NOx-concentration of 1,7 ppm.
The examples are summarized in the following table
CA 02469783 2004-06-09
WO 03/055830 PCT/N002/00494
19
q:9 >'d m,_z~ p m m ~ ~ si a. ~ m õx-~
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