Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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AECI 771
THIS INVENTION relates, broadly, to an explosive. More particularly the
invention relates to a method and apparatus suitable for m~king a flowable explosive,
in particular an emulsion explosive.
According to the invention there is provided a method of m~king a sensitized flowable explosive, the method comprising the steps of:
pumping a non-detonatable explosive base from a supply of said base by
means of an explosive base pump along a conduit having a mixing device at or
adjacent a downstream end thereof;
simultanéously pumping a lubricant liquid from a supply of said lubricant0 liquid along the conduit by means of a lubricant pump;
simultaneously pumping a flowable gassing agent for gassing the base from
a supply of said gassing agent by means of a gassing agent pump along a separateflow line into the conduit, upstream of and at or adjacent the mixing device; and
mixing the base and lubricant liquid together with the gassing agent in the5 mixing device to form a sensitized explosive.
Examples of flowable explosives of the type in question are slurry explosives
and emulsion explosives having respectively a slurry or emulsion base, so that the
mixing results in a sensitized slurry or emulsion explosive, as the case may be.
The pumping of the gassing agent into the conduit will preferably be at a
20 position as close as possible to or imrnediately upstream of the mixing device. In
particular, the mixing device may be at the downstream end of the conduit, the
pumping of the gassing agent into the conduit being at a position immediately
upstream of the mixing device.
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The gassing agent may be a chemical gassing solution such as a solution
having a solvent which comprises water and a solute which comprises nitrite ions.
A sodium nitrite solution will usually be employed, the base and/or lubricant liquid
containing ammonium ions so that the explosive is sensitized by chemical gassing5 caused by the formation of nitrogen bubbles in the base in accordance with the reaction:
NH 4 + NO 2 ~ 2H2O + N2
Each pump may be a reciprocable positive displacement dosing pump and the
pumps may be interconnected or otherwise synchronised with one another to deliver
10 accurately matched outputs. In other words, pumping of the explosive base, pumping
of the lubricarit liquid and pumping of the gassing agent may be by means of
reciprocable positive displacement dosing pumps which are synchronized with one
another to deliver accurately matched outputs. The lubricant liquid will typically be
fed into the conduit at or adjacent the point of feed of the base into the conduit, so
15 that the lubricant liquid forms an annular lubricating layer around the base as they
pass along the conduit. In particular, the explosive base and the lubricant liquid may
be pumped into the conduit at the same position, the lubricant liquid and explosive
base being pumped into the conduit so that they pass simultaneously along the
conduit with the lubricant liquid forming an annular lubricating layer around a core
20 of explosive base, between the core and the conduit.The lubricant may comprise
water and/or a suitable organic liquid for forming a fuel in the eventual sensitized
explosive, such as a glycol, having a suitably low viscosity; and it may comprise
ammonium ions. More particularly, the lubricant liquid may be selected from water,
ethylene glycol, diethylene glycol and mixtures thereof.
The conduit and the flow line may comprise flexible hoses, suitable for
loading an explosive into boreholes, the conduit usually comprising a lance at its
downstream end and the mixing device being mounted in the downstream end of the
lance. The hoses may be strapped together so that they extend side-by-side in use.
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An important advantage of the method is that, when the method has been used
for eg loading sensitized explosive into boreholes and is discontinued, only themixing device and such parts of the conduit (hose or lance), if any, as are
downstream of the mixing device need contain sensitized explosive. Danger is
5 reduced; and the need to discard this sensitized explosive, eg when the method has
been discontinued for a period long enough for this sensitized explosive to become
unsuitable for use, results in loss of relatively small amounts, if any, of explosive.
A further advantage of the invention is that the rate of gassing of the base canbe increased and mixing can be carried out at relatively low pressures with a
10 relatively accurately controlled rate of gassing of the base. Furthermore, as the
gassing solutior; is not used for lubrication, relatively small amounts of water in the
gassing solution can be employed.
Further according to the invention there is provided an apparatus for m~king
a sensitized explosive, the apparatus comprising:
an explosive base pump having an inlet for explosive base emulsion and an
outlet which is connected to a conduit;
a mixing device connected in line with the conduit at or adjacent a
downstream end thereof;
a flowable gassing agent pump having an inlet for a flowable gassing agent
20 and an outlet which is connected to a separate flow line, the separate flow line
having a downstream end which is connected to the conduit at or adjacent and
upstream of the mixing device; and
a lubricant liquid pump having an inlet for a lubricant liquid and an outlet
which is connected to the conduit,
25 the explosive base pump and the lubricant liquid pump having their outlets connected
to the conduit at positions which are at or adjacent each other.
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The pumps may be operatively interconnected or otherwise synchronised as
described above, and may be positive displacement dosing pumps. In particular, the
explosive base pump, the lubricant pump and the gassing agent pump may be
positive displacement dosing pumps which are operatively interconnected to one
S another for synchronous use in the delivery of matched outputs.
The apparatus may include:
a supply of explosive base connected to the inlet of the base pump;
a supply of gassing agent connected to the inlet of the gassing agent pump;
and
10a supply of lubricant liquid connected to the inlet of the lubricant liquid pump.
The conduit and the separate flow line may each be a flexible hose or pipe,
and the conduit may comprise a lance at its downstream end for loading sensitized
explosive into boreholes, the mixing device, which may be a rotary mixer, staticmixer or the like, being associated with the lance, and being mounted eg at the free
15 or downstream end thereof, in line therewith. In a particular embodiment, theconduit and separate flow line may each comprise a flexible hose, the flexible hose
of the conduit having a downstream end connected to an inlet of a lance for loading
sensitized explosive into boreholes, the mixing device being mounted on the lance.
The hoses may be strapped together, eg at spaced intervals along their lengths,
20 so that, in use, they extend alongside each other. In particular, the hoses may be
connected to each other at a plurality of positions spaced along their lengths so that
they extend alongside each other, the mixing device being selected from rotary
mixers and static mixers and the lance having a downstream end, at or adjacent
which the mixing device is mounted.
25While the apparatus may be fixed in place, so that it forms part of an
installation, it will typically be portable by no more than two persons, the apparatus
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comprising a support frame on which the pumps are mounted, the support frame
being provided with a pair of carry handles and a motor, the motor being mountedon the support frame and being operatively interconnected to the pumps for
simultaneously driving the pumps.
S The motor may be an air motor drivable by a compressed air supply, the
support frame being in the form of a sled having a pair of runners for engaging the
ground with the frame in an upright operative attitude.
The invention will now be described, by way of example, with reference to
the accompanying diagrammatic drawings, in which:
Figure l'shows a schematic side elevation of an apparatus in accordance with
the invention; and
Figure 2 shows a schematic plan view of the apparatus of Figure 1.
In the drawings, reference numeral 10 generally an apparatus in accordance
with the present invention. The apparatus 10 is portable by two persons and
comprises an elongated support frame 12 of metal tubing providing pairs of carryhandles 14 at opposite ends thereof. The support frame is in the form of a sled
having a pair of runners 15 on which it can be pushed and pulled along the ground.
An emulsion base supply in the form of a tank 16 is mounted on the frame 12, as are
a gassing agent supply in the form of a tank 18, and a lubricant liquid supply in the
form of a tank 20. The tank 20 is omitted from and is not illustrated in Figure 1,
for clarity of illustration.
A reciprocable piston and cylinder type positive displacement base pump 22
is shown having an inlet connected to the tank 16, an outlet provided with a non-
return valve 24, and an air motor 26 drivingly connected thereto, all being mounted
directly or indirectly on the frame 12. The pump has, mounted on opposite sides
thereof and operatively connected alongside it for simultaneous synchronous
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operation, a gassing agent pump 28 and a lubricant liquid pump 30, having
respective piston rods 32 and 34 connected by respective links 36 and 38 to a piston
40 of the pump 22.
The tank 18 is connected by a flexible hose 42 to an inlet to the pump 28; and
S the tank 20 is connected by a flexible hose 44 (not shown in Figure 1) to an inlet to
the pump 30. The valve 24 in turn feeds into a conduit in the form of a flexible hose
46; and the pump 30 has an outlet feeding via a flexible hose 48 into the hose 46,
immediately downstream of and adjacent the valve 24, the pump 28 having an outlet
feeding via a flexible hose 50 which extends alongside the hose 46 and is strapped
10 thereto by straps 52 spaced along the length of the hose 46.
The downstream end of the hose 46 is provided with a lance (not shown)
having a rotary or static mixer (also not shown) at its downstream end. The hose 46
feeds into the lance and into the mixer, and the hose 50 extends alongside the lance
up to the mixer, into which it feeds, the mixer in turn feeding into the outlet Or the
15 lance at the tip of the lance.
In use, the apparatus 10 will typically be taken to a blasting site, for exampleunder ground in a mine. The apparatus can conveniently be carried by two personsby means of a handle 14, with the hose 46 and associated lance coiled on the frame
12, and the tanks 16, 18, 20 cont~inin~ the necessary constituents.
Usually the apparatus will be used in accordance with the method of the
present invention to make a sensitized emulsion explosive of the water-in-oil type,
which comprises an oil-based continuous phase and a water-based discontinuous
phase dispersed in the continuous phase.
In this type of system, the tank 16 will contain an emulsion base, and the tank
18 will contain an aqueous sodium nitrite gassing solution. The tank 20 will in turn
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contain a lubricant liquid, for example a suitable water/ethylene glycol mixturecontaining ammonium ions and a gassing reaction catalyst such as a thiourea,
together with pH-controlling additives and the like.
At a blasting site, the motor 26 is used synchronously to drive the pumps 22,
28 and 30. Pump 22 pumps emulsion base from the tank 16 into the upstream end
of the hose 46 via the non-return valve 24; and pump 30 pumps lubricant liquid
which it receives via the hose 44 from the tank 20, into the hose 46 via the hose 48,
at the upstream end of the hose 46, immediately adjacent and downstream of the
valve 24. Emulsion base flows along the hose 46, and its passage along the hose 46
is lubricated by an annular layer of the lubricant liquid which surrounds it, and eases
its travel along ~he hose 46. The pump 28 receives gassing solution via the hose 42
from the tank 18, and pumps it long the hose 50. It should be noted in this regard
with reference to the aforegoing that the gassing solution can contain a proportion
of ethylene glycol, the ethylene glycol in the gassing solution and lubricant liquid
being water-miscible and capable of acting as a fuel, although other water-miscible
fuels may be used instead of the ethylene glycol.
At the downstream end of the hose 46, the hose 46 and hose 50 respectively
feed into the inlet of the mixer in the lance, where the lubricant liquid, emulsion base
and gassing solution are thoroughly and homogeneously mixed together, to form anemulsion explosive.
It should be noted that rapid mixing is permitted between the lubricant liquid
and gassing solution before they become finally incorporated into the emulsion
explosive, thereby permitting thorough reaction of the nitrite ions in the gassing
solution with the ammonium ions in the lubricant liquid, for effective and reliable
nitrogen bubble formation.
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It should be noted in particular, that, in a variation of the method of the
invention, the lubricant liquid can be introduced into the hose 46, or the lance,
somewhat upstream of the mlxer. In this way, the lubricant liquid and gassing
solution, which are readily miscible liqulds, can be given the opportunity to mix
S homogeneously together, to initiate gassing and to bring said ammonium ions into
contact with said nitrite ions, before the lubricant liquid and gassing solution are
emulsified into the emulsion base in the mixer, thereby further promoting efficient
and reliable gassing of the emulsion explosive.
In this regard it is to be noted that sensitizing water-in-oil emulsion
10 explosives by chemical gassing is problematic when a gassing solution is simply
mixed into an émulsion base cont~ining ammonium ions, as the rate of gassing
reaction is dependent on a number of chemical factors and other factors such as pH,
temperature, time and concentration of catalyst, but in particular, the mixing
efficiency may be rate-determining factor of the gassing reaction. This is because,
15 on addition of the gassing solution to the water-in-oil emulsion base, discrete droplets
of gassing solution can be formed within the continuous oil phase of the emulsion
base. As the ammonium ions in this case are typically contained in the discontinuous
water phase of the emulsion base, for these ammonium ions and the nitrite ions of
the gassing solution to come into contact with one another, ion transport across20 emulsion oil phase/water phase bilayers is necessitated. As the continuous phase is
oil-based, transport by diffusion of the water-soluble ions in question is relatively
slow and can become rate-deterrnining.
It is a particular advantage of the present invention that it can elimin~te thisrate-determining limitation, by providing the ammonium ions in the lubricant solution
25 and ensuring that the lubricant solution and gassing solution, come into contact with
each other and are at least partially admixed with each other before or at least no
later than when they are mixed into the emulsion base. Rapid mixing thereof takes
place as the lubricant liquid and gassing solution are easily miscible aqueous
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solutions, and effective and reliable nitrogen bubble and gasification are promoted,
at least partially prior to isolation of the amrnonium and nitrite ions in separate
droplets separated from one another by the oil phase of the emulsion. The rate of
the gassing reaction is therefor controlled by temperature and chemical factors, and
5 ion diffusion is no longer rate-controlling.
With regard to the aforegoing, it should be noted that the roles of the gassing
solution and lubricant liquid can be reversed, in the sense that, if desired, the
solution cont~ining the nitrite ions may be contained in the tank 20 and pumped by
the pump 30; with the solution cont~ining the ammonium ions being contained in
10 the tank 18 and pumped by the pump 28. This latter possibility will, however,usually not be preferred, as the emulsion base typically contains ammonium ions, so
that some gassing can take place along the whole length of the hose 46, which isundesirable, as it can necessitate discarding the contents of the hose 46 after loading
a borehole has been continued, and before loading a further borehole is initiated.
15 This reversal of roles is however feasible if the emulsion base contains no
ammonium ions, and in this case the nitrite ion-cont:~ining solution will in fact act
as a lubricant solution and the ammonium ion-cont~ining solution will in fact act as
a gassing solution.
Comparative Tests
Comparative tests were carried out whereby the method and apparatus
of the present invention were compared in use with a standard gassing
method and apparatus, using the same emulsion base which was
prepared at 10C, the same lubricant liquid and the same flowable
gassing agent. The present invention resulted in the production, after
20 mimltes, of a sensitized emulsion explosive product having a density
of 1,10 g/cm3, whereas the standard gassing system produced a product
having a final density of 1,18 g/cm3 after 60 minutes.
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In a further test, using a high crystallized emulsion base, it was found
that the abovementioned standard gassing system resulted in hardly any
gassing of the base, whereas the method and apparatus of the present
invention were found to be capable, on this highly crystallized
emulsion base, of achieving a final density of 1,15 g/cm3 after 25
minutes.
Comparative tests on a further emulsion base, having a starting density
of 1,52 g/cm3, resulted in a final density of 1,25 g/cm3 using the
standard gassing system, and a final density of 1,18 g/cm3 using the
method and apparatus of the present invention.
Finally, the standard (control) system was found to be incapable of
gassing an emulsion base having a pH > 3,6, but it was found that this
emulsion base could be gassed to a final density of 1,18 g/cm3 after 25
minlltes, using the method and apparatus of the present invention.
The above tests illustrate that, when the method and apparatus of the present
invention are used, the gassing rate is less dependent on the properties of the
emulsion than is the case with the standard gassing system tested as a control, and
the gassing was found to be more easily and accurately controllable than with the
standard system, when using the method and apparatus of the present invention.
