U.S. patent application number 11/046733 was filed with the patent office on 2006-11-02 for explosive compositions.
Invention is credited to Donald J. Houston, William G. McGillis.
Application Number | 20060243362 11/046733 |
Document ID | / |
Family ID | 37233277 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060243362 |
Kind Code |
A1 |
Houston; Donald J. ; et
al. |
November 2, 2006 |
Explosive compositions
Abstract
A pumpable watergel explosive composition comprises 10 to 40 wt
%, based on the total weight of the pumpable explosive composition,
of a continuous liquid phase comprising a solvent, a solubilized
chemical sensitizer and a gelling agent and 60 to 90 wt %, based on
the total weight of the pumpable explosive composition, of a
discontinuous solid phase comprising particulate oxidizer salt
particles having interstitial spaces between the salt particles.
The watergel explosive composition has a density of 1.05-1.4 g/cc
and, a shear thinning rheology such that, when subjected to an
external force, the explosive composition has a viscosity
sufficiently low to render the watergel explosive composition
pumpable. The combination of density and low water content provides
energy numbers normally associated with more expensive aluminized
formulations.
Inventors: |
Houston; Donald J.; (North
Bay, CA) ; McGillis; William G.; (North Bay,
CA) |
Correspondence
Address: |
BERESKIN AND PARR
40 KING STREET WEST
BOX 401
TORONTO
ON
M5H 3Y2
CA
|
Family ID: |
37233277 |
Appl. No.: |
11/046733 |
Filed: |
February 1, 2005 |
Current U.S.
Class: |
149/46 |
Current CPC
Class: |
C06B 23/001 20130101;
C06B 47/14 20130101; C06B 31/285 20130101 |
Class at
Publication: |
149/046 |
International
Class: |
C06B 31/28 20060101
C06B031/28 |
Claims
1. A pumpable watergel explosive composition comprising: a) 10 to
40 wt %, based on the total weight of the pumpable explosive
composition, of a continuous liquid phase comprising a solvent, a
solubilized chemical sensitizer and a gelling agent: and, b) 90 to
60 wt %, based on the total weight of the pumpable explosive
composition, of a discontinuous solid phase comprising particulate
oxidizer salt particles having interstitial spaces between the salt
particles wherein the liquid phase fills the interstitial spaces,
the watergel explosive composition has a density of 1.05-1.4 g/cc
and, when subjected to an external force, has a viscosity
sufficiently low to render the watergel explosive composition
pumpable.
2. The pumpable watergel explosive composition of claim 1 wherein
the particulate oxidizer salt comprises particles having a tapped
bulk density of 0.9-1.05 g/cc.
3. The pumpable watergel explosive composition of claim 1 wherein
the particulate oxidizer salt consists essentially of particles
having a tapped bulk density of 0.9-1.05 g/cc.
4. The pumpable watergel explosive composition of claim 2 wherein
the solubilized chemical sensitizer comprises an organic nitrogen
based salt of an inorganic oxidizing acid.
5. The pumpable watergel explosive composition of claim 4 wherein
the nitrogen based salt comprises an amine salt.
6. The pumpable watergel explosive composition of claim 5 wherein
the solubilized chemical sensitizer further comprises ammonium
nitrate.
7. The pumpable watergel explosive composition of claim 4 wherein
the solvent is selected from the group consisting of water, an
alcohol, a glycol and mixtures thereof.
8. The pumpable watergel explosive composition of claim 6 wherein
the solvent comprises water.
9. The pumpable watergel explosive composition of claim 3 wherein
the particulate oxidizer salt is selected from the group consisting
of alkali metal nitrates and perchlorates, alkaline-earth metal
nitrates and perchlorates and mixtures thereof.
10. The pumpable watergel explosive composition of claim 9 wherein
the particulate oxidizer salt further comprises at least one
additional alkali metal nitrates and perchlorates, alkaline-earth
metal nitrates and perchlorates and mixtures thereof.
11. The pumpable watergel explosive composition of claim 1 wherein
the liquid phase comprises from 30 to 85 wt % solubilized chemical
sensitizer, from 15 to 40 wt % solvent and up to 30 wt %
solubilized oxidizer salt, based on the total weight of the liquid
phase.
12. The pumpable watergel explosive composition of claim 1 wherein
the liquid phase comprises from 50 to 80 wt % solubilized chemical
sensitizer, from 18 to 27 wt % solvent and up to 30 wt %
solubilized oxidizer salt, based on the total weight of the liquid
phase.
13. The pumpable watergel explosive composition of claim 12 wherein
the liquid phase comprises an aqueous MMAN solution and the
oxidizer salt comprises ammonium nitrate.
14. The pumpable watergel explosive composition of claim 1 wherein
the liquid phase comprises 15 to 25 wt % of the solublilized
chemical sensitizer and from 7-12 wt % solvent, based on the total
weight of the liquid phase.
15. The pumpable watergel explosive composition of claim 14 wherein
the solublilized chemical sensitizer consists essentially of nitric
or perchloric acid salts derived from organic amines.
16. The pumpable watergel explosive composition of claim 1 wherein
the pumpable watergel explosive composition comprises from 5 to 15
wt % solvent, based on the total weight of the pumpable explosive
composition.
17. The pumpable watergel explosive composition of claim 1 wherein
the pumpable watergel explosive composition comprises from 7 to 10
wt % solvent, based on the total weight of the pumpable explosive
composition.
18. The pumpable watergel explosive composition of claim 15 wherein
the solvent comprises water.
19. The pumpable watergel explosive composition of claim 1 further
comprising an insoluble sensitizer.
20. The pumpable watergel explosive composition of claim 19 wherein
the insoluble sensitizer comprises perlite, microspheres, a gassing
agent and mixtures thereof.
21. The pumpable watergel explosive composition of claim 1 wherein
the gelling agent comprises guar gum, xanthan gum, locust bean gum,
polyvinyl acetate, polyethylene oxides, polyacrylamide, starch and
mixtures thereof.
22. The pumpable watergel explosive composition of claim 1 further
comprising a cross linking agent.
23. The pumpable watergel explosive composition of claim 1 wherein
the gelling agent comprises a guar gum which, 60 minutes after
9.00.+-.0.01 g of the guar gum is added to a solution of 702 g of
AN, 240 g of sodium nitrate and 258 g of distilled water at
43.degree. C. and stirred for 2 minutes, has a viscosity of
7000-17,000 cps at 25.degree. C.
24. The pumpable watergel explosive composition of claim 1
comprising from 0.3 to 1 wt % of the gelling agent, based on the
total weight of the pumpable explosive composition.
25. The pumpable watergel explosive composition of claim 1
comprising from 0.3 to 0.6 wt % of the gelling agent, based on the
total weight of the pumpable explosive composition.
26. The pumpable watergel explosive composition of claim i wherein
watergel explosive composition has a viscosity of 10,000-35,000 cps
at 20 rpm and 21.degree. C.
27. The pumpable watergel explosive composition of claim 13 wherein
watergel explosive composition has a viscosity of from 50,000 to
300,000 cps at 2 rpm and 21.degree. C.
28. The pumpable watergel explosive composition of claim 1 wherein
the particulate oxidizer salt is associated with an organic
combustible fuel.
29. The pumpable watergel explosive composition of claim 28 wherein
the particulate oxidizer salt is combined with the organic
combustible fuel to form a mixture prior to mixing the liquid phase
with the mixture.
30. The pumpable watergel explosive composition of claim 29 wherein
the particulate oxidizer salt comprises an ANFO blend.
31. The pumpable watergel explosive composition of claim 1 wherein
the watergel explosive composition comprises less than 15 wt. %
aluminum.
32. The pumpable watergel explosive composition of claim 1 wherein
the watergel explosive composition comprises essentially no
aluminum.
33. The pumpable watergel explosive composition of claim 1 wherein
the watergel explosive composition comprises 15 to 35 wt % of the
continuous liquid phase and 85 to 65 wt %, of the discontinuous
solid phase, based on the total weight of the pumpable explosive
composition.
34. The pumpable watergel explosive composition of claim 1 wherein
the watergel explosive composition comprises 20 to 30 wt % of the
continuous liquid phase and 80 to 70 wt %, of the discontinuous
solid phase, based on the total weight of the pumpable explosive
composition.
35. The pumpable watergel explosive composition of claim 2 wherein
the particles comprise ammonium nitrate particles.
36. A method of manufacturing a pumpable watergel explosive
composition comprising: a) preparing a liquid chemical sensitizer
solution comprising a solvent a solubilized chemical sensitizer and
a gelling agent at a first location; b) transporting the liquid
chemical sensitizer solution to a second location; c) combining 10
to 40 wt % of the liquid chemical sensitizer solution, based on the
total weight of the pumpable explosive composition, with 90-60 wt %
of a solid phase comprising particulate oxidizer salt particles
having a tapped bulk density of 0.9-1.05 g/cc and having
interstitial spaces between the salt particles, based on the total
weight of the pumpable explosive composition, to form the pumpable
explosive composition wherein a gelling agent is added either to
the liquid chemical sensitizer prior to combining the liquid
chemical sensitizer with the solid phase, or during step (c), the
liquid chemical sensitizer solution fills the interstitial spaces,
the watergel explosive composition has a density of 1.05-1.4 g/cc
and, when subjected to an external force, has a viscosity
sufficiently low to render the watergel explosive composition
pumpable.
37. The method of claim 36 wherein the pumpable watergel explosive
composition also comprises an insoluble sensitizer, the liquid
chemical sensitizer solution is a booster sensitive explosive and
the method further comprises transporting the liquid chemical
sensitizer solution as a booster sensitive explosive to the second
location and transporting the solid phase as a non-explosive to the
second location.
38. The method of claim 37 wherein the second location is a
location at which the watergel explosive composition will be used
and the method further comprises adding a cross linking agent to
the explosive composition contemporaneous with loading the watergel
explosive composition into a bore hole.
39. The method of claim 36 further comprising selecting as the
gelling agent a guar gum which, 60 minutes after 9.00.+-.0.01 g of
the guar gum is added to a solution of 702 g of AN, 240 g of sodium
nitrate and 258 g of distilled water at 43.degree. C. and stirred
for 2 minutes, has a viscosity of 7,000-12,000 cps at 25.degree.
C.
40. The method of claim 39 wherein the second location is a
location at which the watergel explosive composition will be used
and the method further comprises adding a cross linking agent to
the explosive composition contemporaneous with loading the watergel
explosive composition into a bore hole.
41. The method of claim 36 further comprising adding at least one
of a) an organic combustible fuel, b) at least one additional
alkali metal nitrates and perchlorates, alkaline-earth metal
nitrates and perchlorates and mixtures thereof; and, c) and
mixtures of (a) and (b).
42. A pumpable watergel explosive composition comprising: a) 10 to
40 wt %, based on the total weight of the pumpable explosive
composition, of a continuous liquid phase comprising a solvent, a
solubilized chemical sensitizer, and a gelling agent: and, b) 90 to
60 wt %, based on the total weight of the pumpable explosive
composition, of a discontinuous solid phase comprising particulate
oxidizer salt particles wherein, the gelling agent comprises a guar
gum which, 60 minutes after 9.00.+-.0.01 g of the guar gum is added
to a solution of 702 g of AN, 240 g of sodium nitrate and 258 g of
distilled water at 43.degree. C. and stirred for 2 minutes, has a
viscosity of 9000-12,000 cps at 25.degree. C., the watergel
explosive composition has a density of 1.05-1.4 g/cc and, when
subjected to an external force, has a viscosity sufficiently low to
render the watergel explosive composition pumpable.
43. The pumpable watergel explosive composition of claim 42 wherein
the particulate oxidizer salt is selected from the group consisting
of alkali metal nitrates and perchlorates, alkaline-earth metal
nitrates and perchlorates and mixtures thereof.
44. The pumpable watergel explosive composition of claim 43 wherein
the particulate oxidizer salt comprises ammonium nitrate particles
having a tapped bulk density of 0.9-1.05 g/cc.
45. The pumpable watergel explosive composition of claim 43 wherein
the particulate oxidizer salt consists essentially of ammonium
nitrate particles having a tapped bulk density of 0.9-1.05
g/cc.
46. The pumpable watergel explosive composition of claim 44 wherein
the particulate oxidizer salt further comprises at least one
additional alkali metal nitrates and perchlorates, alkaline-earth
metal nitrates and perchlorates and mixtures thereof.
47. The pumpable watergel explosive composition of claim 42 wherein
the solubilized chemical sensitizer comprises an organic nitrogen
based salt of an inorganic oxidizing acid.
48. The pumpable watergel explosive composition of claim 47 wherein
the nitrogen based salt comprises an amine salt.
49. The pumpable watergel explosive composition of claim 42 wherein
the solvent is selected from the group consisting of water, an
alcohol, a glycol and mixtures thereof.
50. The pumpable watergel explosive composition of claim 48 wherein
the solvent comprises water.
51. The pumpable watergel explosive composition of claim 50 wherein
the liquid phase comprises from 30 to 85 wt %. solubilized chemical
sensitizer, from 15-40 wt % solvent and up to 30 wt % solubilized
oxidizer salt, based on the total weight of the liquid phase.
52. The pumpable watergel explosive composition of claim 51 wherein
the liquid phase comprises from 50 to 80 wt % solubilized chemical
sensitizer, from 18 to 27 wt % solvent and up to 30 wt %
solubilized oxidizer salt, based on the total weight of the liquid
phase.
53. The pumpable watergel explosive composition of claim 42 wherein
the liquid phase comprises an aqueous MMAN solution and the
oxidizer salt comprises ammonium nitrate particles having a tapped
bulk density of 0.9-1.05 g.
54. The pumpable watergel explosive composition of claim 42 wherein
the liquid phase comprises 15 to 25 wt % of the solublilized
chemical sensitizer and from 7-12 wt % solvent, based on the total
weight of the liquid phase.
55. The pumpable watergel explosive composition of claim 54 wherein
the solublilized chemical sensitizer consists essentially of nitric
or perchloric acid salts derived from organic amines.
56. The pumpable watergel explosive composition of claim 42 wherein
the pumpable watergel explosive composition comprises from 5 to 15
wt % solvent, based on the total weight of the pumpable explosive
composition.
57. The pumpable watergel explosive composition of claim 42 wherein
the pumpable watergel explosive composition comprises from 7 to 10
wt % solvent, based on the total weight of the pumpable explosive
composition.
58. The pumpable watergel explosive composition of claim 56 wherein
the solvent comprises water.
59. The pumpable watergel explosive composition of claim 42 further
comprising an insoluble sensitizer.
60. The pumpable watergel explosive composition of claim 42 wherein
the gelling agent comprises guar gum, xanthan gum, locust bean gum,
polyvinyl acetate, polyethylene oxides, polyacrylamide, starch and
mixtures thereof.
61. The pumpable watergel explosive composition of claim 42 further
comprising a cross linking agent.
62. The pumpable watergel explosive composition of claim 42 wherein
the gelling agent comprises a guar gum which, 60 minutes after
9.00.+-.0.01 g of the guar gum is added to a solution of 702 g of
AN, 240 g of sodium nitrate and 258 g of distilled water at
43.degree. C. and stirred for 2 minutes, has a viscosity of
7000-17,000 cps at 25.degree. C.
63. The pumpable watergel explosive composition of claim 42 wherein
the gelling agent comprises a guar gum which, 60 minutes after
9.00.+-.0.01 g of the guar gum is added to a solution of 702 g of
AN, 240 g of sodium nitrate and 258 g of distilled water at
43.degree. C. and stirred for 2 minutes, has a viscosity of
7,000-12,000 cps at 25.degree. C.
64. The pumpable watergel explosive composition of claim 42
comprising from 0.3 to 1 wt % of the gelling agent, based on the
total weight of the pumpable explosive composition.
65. The pumpable Watergel explosive composition of claim 42
comprising from 0.3 to 0.6 wt % of the gelling agent, based on the
total weight of the pumpable explosive composition.
66. The pumpable watergel explosive composition of claim 42 wherein
watergel explosive composition has a viscosity of 10,000-35,000 cps
at 20 rpm and 21.degree. C.
67. The pumpable watergel explosive composition of claim 53 wherein
watergel explosive composition has a viscosity of from 50,000 to
300,000 cps at 2 rpm and 21.degree. C.
68. The pumpable watergel explosive composition of claim 42 wherein
the particulate oxidizer salt is associated with an organic
combustible fuel.
69. The pumpable watergel explosive composition of claim 42 wherein
the particulate oxidizer salt comprises an ANFO blend.
70. The pumpable watergel explosive composition of claim 42 wherein
the watergel explosive composition comprises less than 15 wt. %
aluminum.
71. The pumpable watergel explosive composition of claim 42 wherein
the watergel explosive composition comprises essentially no
aluminum.
72. The pumpable watergel explosive composition of claim 42 wherein
the watergel explosive composition comprises 15 to 35 wt % of the
continuous liquid phase and 85 to 65 wt %, of the discontinuous
solid phase, based on the total weight of the pumpable explosive
composition.
73. The pumpable watergel explosive composition of claim 42 wherein
the watergel explosive composition comprises 20 to 30 wt % of the
continuous liquid phase and 80 to 70 wt %, of the discontinuous
solid phase, based on the total weight of the pumpable explosive
composition.
Description
FIELD OF THE INVENTION
[0001] This invention relates to explosive compositions utilizing a
continuous liquid phase and a discontinuous solid phase. In
particular, the invention relates to ammonium nitrate fuel oil
(ANFO) or ammonium nitrate (AN)/watergel blend explosive
compositions. In another aspect, this invention also relates to
different methods to manufacture the explosive composition.
BACKGROUND OF THE INVENTION
[0002] Various different forms of explosive compositions are known
including ANFO explosive compositions, watergel, explosive
compositions, slurry-type explosive compositions and emulsion
explosive compositions. Each type of explosive compositions has its
own advantages and disadvantages. For example, ANFO explosive
compositions are useful in applications not requiring a water
resistant explosive formulation, due to its low cost.
[0003] Watergel blasting explosives may be selected when a
combination of water resistance and superior heave is required.
[0004] Slurry-type blasting explosives may be selected when water
resistance is required and superior sensitivity is not
required.
[0005] Emulsion explosive compositions might be selected when water
resistance is required and superior heave is not required.
[0006] In all cases, the explosive composition must have
characteristics which will allow it to be readily loadable into a
bore hole while, at the same time, ensuring that the explosive
composition will not degrade if the explosive composition remains
in the bore hole for an extended period of time while a site is
prepared for initiation. For example, the explosive composition
might be loaded into a plurality of boreholes (typically from about
50-100 holes to more than about 200 holes) over a period of hours
to days. Accordingly, the explosive composition could be kept in a
borehole for from several days to several months prior to being
detonated. The explosive composition must be sufficiently stable to
not segregate into its component parts thereby permitting the
explosive composition to detonate after being stored in a borehole
for an extended period of time.
[0007] In addition, water may accumulate in a borehole, such as
from the inflow of ground water. Particulate ammonium nitrate will
readily dissolve in water. Accordingly, if the explosive
composition contains ammonium nitrate, such as in the case on an
ANFO explosive composition or a blended explosive composition that
contains particulate ammonium nitrate, the explosive composition
must be sufficiently water resistant so as to permit the explosive
composition to detonate, even after being stored for an extended
period of time in a wet borehole.
[0008] Many different approaches have been suggested in the prior
art for producing explosive compositions that can be formulated
from readily available materials and which will have the required
stability and water resistance characteristics. For example,
Sandell (U.S. Pat. No. 4,380,482) discloses water-bearing explosive
compositions comprising oxidizer, fuel and sensitizer components in
a thickened or gelled continuous aqueous phase wherein the aqueous
phase is stabilized against degradation of its thickened or gelled
structure by the incorporation therein of iodide and/or iodate
ions.
[0009] Honeyman et al (U.S. Pat. No. 4,585,495) discloses an
explosive composition comprising a sensitized blend of ANFO and an
aqueous slurry composition. In the blends of Honeyman et al,
storage-stability is achieved because of the water-retentive
character of the slurry per se, in contrast to the film barriers
and waterproof prill coatings previously required (column 3, lines
4-8).
[0010] Machacek et al (U.S. Pat. No. 4,718,954) discloses an
explosive composition comprising 5 to 60 parts by weight of a gel
concentrate and 95 to 40 parts by weight of a particulate oxidizer.
In the composition, the gel concentrate partially, but not
completely, fills the interstitial voids between the particles of
the oxidizer (column 2, lines 39-47). One disadvantage of some of
the explosive compositions is limited sensitivity. For example, as
shown in tables 2 and 3 of this patent, the explosive composition
failed in some three inch and four inch diameter tests.
[0011] Another approach is set out in Cranney et al (U.S. Pat. No.
5,490,887) which discloses a watergel explosive composition having
a density of 0.8 g/cc. The explosive composition is described as
being advantageous for use in soft blasting operations and is water
resistant (column 1, line 61-67).
[0012] Richard et al (U.S. Pat. No. 5,925,846) discloses an ANFO
blasting composition having improved water resistance.
SUMMARY OF THE INVENTION
[0013] In accordance with this invention, a watergel type explosive
composition is prepared which has a high prill content, a high
energy level yet is still pumpable. Accordingly, in accordance with
one embodiment of the instant invention, there is provided a
pumpable explosive composition comprising:
[0014] a) 10 to 40 wt %, based on the total weight of the pumpable
explosive composition, of a continuous liquid phase comprising a
solvent, a solubilized chemical sensitizer and a gelling agent:
and,
[0015] b) 90 to 60 wt %, based on the total weight of the pumpable
explosive composition, of a discontinuous solid phase comprising
particulate oxidizer salt particles having interstitial spaces
between the salt particles
[0016] wherein the liquid phase fills the interstitial spaces, the
watergel explosive composition has a density of 1.05-1.4 g/cc and,
when subjected to an external force, has a viscosity sufficiently
low to render the watergel explosive composition pumpable.
[0017] In accordance with another embodiment of the instant
invention there is provided a pumpable explosive composition
comprising:
[0018] a) 10 to 40 wt %, based on the total weight of the pumpable
explosive composition, of a continuous liquid phase comprising a
solvent, a solubilized chemical sensitizer, and a gelling agent:
and,
[0019] b) 90 to 60 wt %, based on the total weight of the pumpable
explosive composition, of a discontinuous solid phase comprising
particulate oxidizer salt particles
[0020] wherein, the gelling agent comprises a guar gum which, 60
minutes after 9.00.+-.0.01 g of the guar gum is added to a solution
of 702 g of AN, 240 g of sodium nitrate and 258 g of distilled
water at 43.degree. C. and stirred for 2 minutes, has a viscosity
of 9000-12,000 cps at 25.degree. C., the watergel explosive
composition has a density of 1.05-1.4 g/cc and, when subjected to
an external force, has a viscosity sufficiently low to render the
watergel explosive composition pumpable.
[0021] The solid phase preferably comprises a substantial portion
of ammonium nitrate and, may consist essentially of ammonium
nitrate particles. Ammonium nitrate is generally one of the lower
cost ingredients used in explosive compositions. Accordingly, the
use of substantial quantities of ammonium nitrate in the explosive
composition permits a reduction in the cost of the explosive
composition while still providing an explosive composition that has
good explosive characteristics (e.g. velocity of detonation) as
well as good pumpability.
[0022] In practice, aluminum is commonly added to increase the
energy in explosive compositions, such as ANFO, emulsions and
watergels. While aluminum is one of the most expensive ingredients
which is included in explosive compositions, the energy provided by
the aluminum is generally required to offset the amount of water
which is required in prior art watergel explosive compositions to
render the explosive composition pumpable. In accordance with the
instant invention, the explosive composition has a relatively low
water content, preferably from 5 to 13 wt. % water, and, more
preferably, from 7 to 10 wt. % water. At such water levels, the
explosive composition of the instant invention remains pumpable.
Due to this lower water content, the explosive composition may
utilize a reduced amount of aluminum and, preferably, no aluminum
depending on the energy required for a particular application. In
particular, the explosive composition preferably comprises less
than 15%, more preferably less than 5% and, most preferably no
aluminum.
[0023] Accordingly, the explosive compositions of the instant
invention have a higher energy, which increases heave and
fragmentation compared to previous non-aluminized bulk water gels
of the same density.
[0024] A further advantage of the instant invention is that the
increased energy of the explosive composition permits an alteration
in the drill pattern required at a blasting site. For example,
essentially the same performance can be obtained at a reduced
powder factor (i.e. in the amount of rock which is broken by an
explosion using fewer holes) than would be required if a prior art
watergels having the same density was used. Further, the pattern of
the blasting may be expanded with no loss of fragmentation of
heave.
[0025] The explosive composition of the instant invention also
exhibits a shear-thinning rheology. Pursuant to this rheology, when
the explosive composition is subjected to shear forces (e.g. the
explosive composition is passed through a pump so as to load the
explosive composition into a bore hole), the shear forces result in
the viscosity of the explosive composition being reduced thereby
facilitating the pumping of the explosive composition. When the
shear force is removed, the viscosity increases. This results in
reduced slumping (i.e. the explosive composition is less likely to
flow into imperfections in a borehole). This reduced slumping can
result in the explosive being less environmentally hazardous. For
example, if less of the explosive composition seeps into cracks in
the walls of the borehole, this will result in less low-order
detonation or deflagration. The lower order detonation can result
in toxic fumes being produced during detonation. Further, it is
less likely that undetonated product will be left in the broken
rock thereby reducing the environmental impact of utilizing the
explosive composition.
[0026] In order to be pumpable, it is preferred that the explosive
composition has a viscosity of less than 35,000 cps at 20 rpm, more
preferably less than 20,000 cps, and, most preferably less than
15,000 cps at 21.degree. C. The shear thinning rheology is
evidenced by the viscosity of the explosive composition at rest. In
order to simulate the viscosity of the explosive composition at
rest, the viscosity of the explosive composition at 21.degree. C.
and 2 rpm was measured. Preferably, at these conditions, the
explosive composition has a viscosity from 50,000 to 300,000 cps,
more preferably from 75,000 to 200,000 cps and, most preferably,
from 100,000 to 150,000 cps.
[0027] In one embodiment, the solubilized chemical sensitizer
comprises an organic nitrogen based salt of an inorganic oxidizing
acid. Preferably, the nitrogen based salt comprises an amine salt.
Optionally, the solubilized chemical sensitizer further comprises
ammonium nitrate.
[0028] In another embodiment, the solvent is selected from the
group consisting of water, an alcohol, a glycol and mixtures
thereof. Preferably, the solvent comprises water.
[0029] In another embodiment, the particulate oxidizer salt is
selected from the group consisting of alkali metal nitrates and
perchlorates, alkaline-earth metal nitrates and perchlorates and
mixtures thereof.
[0030] In another embodiment, the particulate oxidizer salt
comprises, and preferably consists essentially of, ammonium nitrate
particles having a tapped bulk density of 0.9-1.05 g/cc. The
particulate oxidizer salt may further comprise at least one
additional alkali metal nitrates and perchlorates, alkaline-earth
metal nitrates and perchlorates and mixtures thereof.
[0031] In another embodiment, the liquid phase comprises from 30 to
85 wt% solubilized chemical sensitizer, from 15-40 wt % solvent and
up to 30 wt % solubilized oxidizer salt, based on the total weight
of the liquid phase.
[0032] In another embodiment, the liquid phase comprises from 50 to
80 wt % solubilized chemical sensitizer, from 18 to 27 wt % solvent
and up to 30 wt % solubilized oxidizer salt, based on the total
weight of the liquid phase.
[0033] In another embodiment, the liquid phase comprises an aqueous
MMAN solution and the oxidizer salt comprises ammonium nitrate.
[0034] In another embodiment, the explosive composition comprises
12 to 21 wt % of the solubilized chemical sensitizer and from 7-10
wt % solvent, based on the total weight of the liquid phase.
[0035] In another embodiment, the solubilized chemical sensitizer
consists essentially of nitric or perchloric acid salts derived
from organic amines.
[0036] In another embodiment, the pumpable watergel explosive
composition comprises from 5 to 15 wt %, and preferably 7 to 10 wt
% solvent, based on the total weight of the pumpable explosive
composition.
[0037] In another embodiment, the pumpable watergel explosive
composition further comprises an insoluble sensitizer. Preferably,
the insoluble sensitizer comprises perlite, microspheres, a gassing
agent and mixtures thereof.
[0038] In another embodiment, the gelling agent comprises guar gum,
xanthan gum, locust bean gum, polyvinyl acetate, polyethylene
oxides, polyacrylamide, starch and mixtures thereof.
[0039] In another embodiment, the pumpable watergel explosive
composition further comprises a cross linking agent.
[0040] In another embodiment, the gelling agent comprises a guar
gum which, 60 minutes after 9.00.+-.0.01 g of the guar gum is added
to a solution of 702 g of AN, 240 g of sodium nitrate and 258 g of
distilled water at 43.degree. C. and stirred for 2 minutes, has a
viscosity of 7000-17,000 cps at 25.degree. C.
[0041] In another embodiment, the pumpable watergel explosive
composition comprises from 0.3 to. 1 wt %, and preferably 0.3 to
0.6 wt %, of the gelling agent, based on the total weight of the
pumpable explosive composition.
[0042] In another embodiment, the watergel explosive composition
has a viscosity of 10,000-35,000 cps at 20 rpm and 21.degree.
C.
[0043] In another embodiment, the watergel explosive composition
has a viscosity of from 50,000 to 300,000 cps at 2 rpm and
21.degree. C.
[0044] In another embodiment, the particulate oxidizer salt is
associated with an organic combustible fuel.
[0045] In another embodiment, the particulate oxidizer salt is
combined with the organic combustible fuel to form a mixture prior
to mixing the liquid phase with the mixture.
[0046] In another embodiment, the particulate oxidizer salt
comprises an ANFO blend.
[0047] In another embodiment, the watergel explosive composition
comprises less than 15% aluminum.
[0048] In another embodiment, the watergel explosive composition
comprises essentially no aluminum.
[0049] In another embodiment, the watergel explosive composition
comprises 15 to 35 wt % of the continuous liquid phase and 85 to 65
wt %, of the discontinuous solid phase, based on the total weight
of the pumpable explosive composition.
[0050] In another embodiment, the watergel explosive composition
comprises 20 to 30 wt % of the continuous liquid phase and 80 to 70
wt %, of the discontinuous solid phase, based on the total weight
of the pumpable explosive composition.
[0051] In accordance with another embodiment of the instant
invention, there is provided a method of manufacturing a pumpable
watergel explosive composition comprising:
[0052] a) preparing a liquid chemical sensitizer solution
comprising a solvent a solubilized chemical sensitizer and a
gelling agent at a first location;
[0053] b) transporting the liquid chemical sensitizer solution to a
second location;
[0054] c) combining 10 to 40 wt % of the liquid chemical sensitizer
solution, based on the total weight of the pumpable explosive
composition, with 90 to 60 wt % of a solid phase comprising
particulate oxidizer salt having interstitial spaces between the
salt particles, based on the total weight of the pumpable explosive
composition, to form the pumpable explosive composition
[0055] wherein a gelling agent is added either to the liquid
chemical sensitizer prior to combining the liquid chemical
sensitizer with the solid phase, or during step (c), the liquid
chemical sensitizer solution fills the interstitial spaces, the
watergel explosive composition has a density of 1.05-1.4 g/cc and,
when subjected to an external force, has a viscosity sufficiently
low to render the watergel explosive composition pumpable.
[0056] An advantage of this embodiment of the invention is that the
liquid chemical sensitizer solution (preferably an aqueous MMAN
solution) may be made at one central location and then shipped to a
site at which the watergel explosive composition will be prepared.
Aqueous MMAN solutions are classified as explosives. Accordingly,
as explosives, special handling is required for storing and
transporting MMAN solutions. However, the liquid chemical
sensitizer comprises only a small proportion of the explosive
composition. A substantial portion of the explosive composition
comprises a solid phase (e.g. AN) that may be shipped and stored as
non-explosives thereby reducing transportation and storage costs.
In some cases, blasting sites are accessible only on winter roads.
In such cases, either a year's worth of the explosive composition
must be stored at site or, alternately, the explosive composition
must be manufactured at site. For example, if the explosive
composition is a 70/30 blend of an emulsion explosive and ANFO,
then 70% of the formula by weight would be classified as an
explosive and must be transported and stored as an explosive. In
such cases, it may be cheaper to build a production plant to
produce the emulsion explosive at site as opposed to transporting
and storing the explosive composition at the site.
[0057] In a preferred embodiment of the instant invention, the
explosive composition comprises only 20 to 30 wt. % of a
composition which is classified as being a booster sensitive
explosive. Accordingly, a substantial portion of the ingredients
for the explosive composition may be stored at site as a
non-explosive thereby simplifying the storage of substantial
quantities of the explosive composition at site.
[0058] In one embodiment, the pumpable watergel explosive
composition also comprises an insoluble sensitizer, the liquid
chemical sensitizer solution is a booster sensitive explosive and
the method further comprises transporting the liquid chemical
sensitizer solution as a booster sensitive explosive to the second
location and transporting the solid phase as a non-explosive to the
second location.
[0059] In another embodiment, the second location is a location at
which the watergel explosive composition will be used and the
method further comprises adding a crosslinking agent to the
explosive composition contemporaneous with loading the watergel
explosive composition into a borehole.
[0060] In another embodiment, the method further comprises
selecting as the gelling agent a guar gum which, 60 minutes after
9.00.+-.0.01 g of the guar gum is added to a solution of 702 g of
AN, 240 g of sodium nitrate and 258 g of distilled water at
43.degree. C. and stirred for 2 minutes, has a viscosity of
7,000-12,000 cps at 25.degree. C.
[0061] In another embodiment,.the method further comprises adding
at least one of (a) an organic combustible fuel, (b) at least one
additional alkali metal nitrates and perchlorates, alkaline-earth
metal nitrates and perchlorates and mixtures thereof; and mixtures
of (a) and (b).
[0062] In another embodiment, the method further comprises
selecting ammonium nitrate particles having a tapped bulk density
of 0.9-1.05 g/cc as the particulate oxidizer salt.
DETAILED DESCRIPTION OF THE INVENTION
[0063] In accordance with this invention, the explosive composition
comprises a blend of a liquid phase and a solid phase. The liquid
phase comprises the continuous phase of the explosive composition
and the solid phase comprises a discontinuous phase of the
explosive composition. Preferably, the liquid and solid phases are
combined so that the liquid phase at least essentially fills the
interstitial spaces between the particles of the solid phase of the
explosive composition.
[0064] The explosive composition may comprises from about 10 to
about 40, preferably from about 15 to about 35 and more preferably
about 20 to about 30 wt. % of the continuous liquid phase and from
about 60 to about 90, preferably from about 85 to about 65 and more
preferably about 80 to about 70 wt. % of the discontinuous solid
phase, based upon the total weight of the pumpable explosive
composition.
[0065] The liquid and solid phases may be combined by any means
known in the art. Preferably, the explosive composition is prepared
by adding the liquid phase to a mixing vessel, followed by addition
of the solids, oil, and particulate oxidizer phase.
[0066] The liquid phase comprises a solvent, a solubilized chemical
sensitizer and a gelling agent. In addition, the liquid phase may
also include an insoluble sensitizer and a cross linking agent.
Optionally, the liquid phase may also include other additives known
in the art such as additives for control of the pH such as fumaric
acid or organic fuels such as oil.
[0067] The solid phase comprises particulate oxidizer salt
particles and may optionally include an organic combustible fuel,
an insoluble sensitizer as well as other additives known in the art
including microspheres, perlite, non-soluble fuels such as aluminum
or rubber, non-soluble explosives such as TNT, PETN, or black
powder.
[0068] Solubilized Chemical Sensitizer
[0069] The chemical sensitizer may be any sensitizer known in the
explosive art which is soluble in a solvent. The chemical
sensitizer may be a water-soluble explosive, preferably nitric or
perchloric acid salts derived from organic amines, including the
nitrates and perchlorates of aliphatic amines, more preferably an
organic salt such as nitrogen-based salts of inorganic oxidizing
acids, preferably amine nitrates, and most preferably nitrates of
1-3 carbon aliphatic amines, such as monomethylamine nitrate (MMAN)
ethylamine nitrate, ethanolamine nitrate, propanolamine nitrate and
ethylenediamine dinitrate. Other amine nitrates may be utilized
such as hexamine nitrate.
[0070] The chemical sensitizer preferably comprises from about 30
to about 85, more preferably from about 50 to about 80 and, most
preferably from about 60 to about 70 wt. % of the liquid phase,
based upon the total weight of the liquid phase. Accordingly, the
amine nitrate will comprise from about 10 to about 30, more
preferably from about 15 to 25 and, most preferably from about 12
to about 18 wt. % of the watergel explosive composition, based upon
the total weight of the water gel explosive composition.
[0071] Solvent
[0072] The solvent may be any liquid in which the chemical
sensitizer may be solubilized. Preferably, the solvent is selected
from the group consisting of water, alcohol, glycol and mixtures
thereof. More preferably, the solvent comprises water and, more
preferably consists essentially of water.
[0073] The solvent may comprise from about 15 to about 40 wt. %,
more preferably from about 18 to about 27 wt. % and most preferably
from about 20 to about 25 wt. % of the liquid phase, based upon the
total weight of the liquid phase. This corresponds to the solvent
comprising from about 5 to about 15 wt. %, preferably from about 7
to about 12 and, most preferably from about 7 to about 10 wt. % of
the explosive composition based upon the total weight of the
explosive composition. Accordingly, while the explosive composition
may comprise less than about 15 wt. % water, and may comprise a
majority of particulate ammonium nitrate, the explosive composition
is still pumpable as a fluid.
[0074] Gelling Agent
[0075] The gelling agent may be any thickening agent known in the
art for water gels. For example, the gelling agent may be one or
more of guar gum, xanthan gum, locust bean gum, polyvinyl acetate,
polyethylene oxides, polyacrylamide or starch. Preferably, the
gelling agent comprises guar gum and, most preferably, consists
essentially of guar gum.
[0076] The gelling agent may comprise from about 0.3 to about 1 wt.
% and, preferably, from about 0.3 to about 0.6 wt. % of the
explosive composition, based upon the total weight of the explosive
composition. This corresponds to the gelling agent comprising about
1-2 wt. % of the liquid phase, based upon the total weight of the
liquid phase.
[0077] Preferably, the guar gum which is utilized is a low
viscosity guar gum. In this application, a low viscosity guar gum
refers to a guar gum which meets the requirements of the following
test. First, a test liquor is prepared utilizing 702 g of ammonium
nitrate, 240 g of sodium nitrate and 258 g of distilled water. The
nitrates are dissolved in the distilled water at an elevated
temperature, but below 85.degree. C. to prevent ammonia from being
lost. When all of the nitrate salts have been dissolved, the test
liquor is cooled to about 47.degree. C. Make up water is added to
account for any evaporative loss so as to obtain 1,200 g of test
liquor. The test liquor is brought to 43.degree. C. and 9 g of guar
gum are added to the test liquor. The guar gum is added in about 7
seconds while mixing at 1650 rpm. The guar gum and test liquor are
mixed for two minutes from the initial addition of the guar gum. A
Brookfield R.V. viscometer with a number 5 spindle is utilized to
determine the viscosity of the test liquor. The test liquor is
allowed to cool to about 25.degree. C. At 60 minutes, the viscosity
of the mixture is measured. The viscosity of the mixture is
preferably 7,000-17,000 cps, more preferably 7,000-12,000 cps and,
most preferably 7,000-10,000 cps at 20 rpm.
[0078] The guar gum will commence to hydrate upon addition to the
liquid phase and will therefore commence to thicken the liquid
phase. A portion of the crosslinking system (e.g., a system which
requires two or more components to produce a crosslinking effect,
such as potassium antimony tartrate and sodium dichromate) may be
added to the liquid phase if the portion that is aged does not
affect or does not markedly affect the viscosity of the liquid
phase to a point at which the liquid phase cannot be pumped or
mixed with the solid phase. This crosslinker, such as from about
0.005 to about 0.01 wt % of potassium antimony tartrate, will not
generally affect the viscosity of the liquid phase until the
remainder of the crosslinking system (i.e. the sodium dichromate)
is added to the explosive composition during delivery of the
explosive composition into the borehole. The remainder of the cross
linker, if any, e.g., sodium dichromate, is preferably added
immediately prior to the end of the hose which loads the explosive
composition into a bore hole (e.g. within about the last ten to
fifty feet of the hose).
[0079] Insoluble Sensitizer
[0080] Optionally, the explosive composition may also include an
insoluble sensitizer. The insoluble sensitizer may be incorporated
in to the liquid phase prior to combining the liquid phase with the
solid phase. Alternately, the insoluble sensitizer may be
incorporated as part of the solid phase or may be a separate feed
stream which is added to the liquid phase and the solid phase to
produce the explosive composition.
[0081] The insoluble sensitizer may comprise any material known in
the art which will decrease the density of the explosive
composition and include air or other gasses in the explosive
composition. Preferably, the insoluble sensitizer comprises one or
more of perlite, microspheres and a gassing agent and, more
preferably, one or more of perlite and microspheres.
[0082] In accordance with a particularly preferred embodiment of
the instant invention, the liquid phase fills, or at least
essentially fills, the interstitial spaces between the particles of
the solid phase. In such a case, it is particularly preferred to
include an insoluble sensitizer as part of the explosive
composition.
Particulate Oxidizer Salt Particles
[0083] Particulate oxidizer salt particles are known in the
explosives art. In accordance with the instant invention, the
particulate oxidizer salt particles are preferably selected from
the group consisting of ammonium, alkali metal nitrates and
perchlorates, ammonium, alkaline-earth metal nitrates and
perchlorates and mixtures thereof. The oxidizer salt particles may
comprise or consist essentially of ammonium nitrate particles.
[0084] A portion of the ammonium nitrate particles may be replaced
by other inorganic oxidizer salts known in the art including
alkaline metal nitrates and perchlorates (such as sodium nitrate
and potassium nitrate) or alkaline-earth metal nitrates and
perchlorates (such as calcium nitrate) or other oxidizer salts.
Preferably, the replacement inorganic salts are sodium nitrate
and/or calcium nitrate. These additional nitrates may be added in
an amount up to 20 wt. %, and preferably, up to 15 wt. %, base upon
the weight of the ammonium nitrate particles in the solid
phase.
[0085] The oxidizer salt oxidizer salt particles preferably
comprise and may consist essentially of high density oxidizer salt
particles. It will be appreciated that the density of a particle
will depend upon the salt which is utilized. High density ammonium
nitrate particles, also known as "miniprills" have a tapped bulk
density of 0.9-1.05, preferably 0.9-1 and, most preferably, about
0.95 g/cc.
[0086] Miniprills may be prepared by any conventional means known
in the art such as spraying molten nitrate containing very little
moisture (e.g. 0.1-0.4 wt. % water, and preferably less than about
0.28 wt. % water) at elevated temperatures (e.g. 175.degree. C. or
higher) into a prilling tower countercurrent to cooling air. The
cooling air solidifies the droplets into prills which are cooled to
ambient temperature. This results in the production of miniprills
which are generally round.
[0087] Miniprills have a smaller void volume than low density
ammonium nitrate particles (i.e. those with a density less than
0.85 g/cc). For example, the void volume of miniprills may be up to
12% lower than the void volume for low density prills.
[0088] In accordance with a particularly preferred embodiment of
the instant invention, the liquid phase and the solid phase are
combined so that the liquid phase essentially fills and,
preferably, completely fills the interstitial spaces (the void
volume) of the particulate oxidizer salt particles. Despite the low
water content of the liquid phase, and the relatively small amount
of the liquid phase which is utilized in preparing the explosive
composition, the explosive composition still exhibits fluid like
characteristics (i.e. it is not a paste or too thick to pump at a
reasonable rate and a safe pressure).
[0089] In some embodiments, some particulate oxidizer salt may be
added to the liquid phase in addition to the solubilized
sensitizer. In such a case, the particulate oxidizer salt will be
solubilized in the solvent. For example, the liquid phase may
comprise up to about 30 wt. % solubilized oxidizer salt,
particularly if the liquid phase has a low content of MMAN.
Preferably the oxidizer salt which is utilized in such cases is
ammonium nitrate. Accordingly, the liquid phase may comprise about
30 wt % MMAN, about 30 wt % AN, about 0.5 wt % guar gum and the
balance water.
Organic Combustible Fuel
[0090] The organic combustible fuel may be selected from any fuel
known in the art. The fuel may be a solid (e.g. a wax, ground
rubber) or a liquid (e.g. fuel oil, heating oil, diesel oil, jet
fuel, kerosene, mineral oils, saturated fatty acids such lauric
acid and stearic acid, alcohol such as cetyl alcohol, corn oil, soy
bean oil and the like) or a mixture of solid and liquid fuels.
Preferably, the organic combustible fuel is a liquid fuel and may
comprise fuel oil such as No. 2 fuel oil. The organic combustible
fuel may also be supplemented with fuel-soluble ingredients such as
glucose, mannose, fructose, waxes, such as microcrystalline wax,
paraffin wax, petroleum wax and the like.
[0091] The organic combustible fuel may be associated with the
particulate oxidizer salt in accordance with any method known in
the explosives art. Preferably, the organic combustible fuel is
combined with the particulate oxidizer salt to form the solid phase
that is then combined with the liquid phase. In a particular
preferred embodiment, the solid phase comprises an ANFO blend. The
ammonium nitrate and fuel oil may be blended in any ratio known in
the art and, preferably, the fuel oil is blended at a rate of 2-4
wt. %, based upon the total weight of the explosive composition,
with the amount reduced appropriately when other solid fuels are
added, to maintain the desired oxygen balance.
[0092] Preferably, the explosive composition contains sufficient
organic combustible fuel so that the explosive composition has a
slightly negative oxygen balance, taking into consideration the
total oxidizing salts, fuel, sensitizers and other additives
present in the explosive composition. Preferably, the negative
oxygen balance is in the range of about -1 to -3.
Cross Linking Agent
[0093] Preferably, the explosive composition also comprises a cross
linking agent. The cross linking agent may be selected from those
known in the art. Preferably, the cross-linking agent is a metal
salt, such as potassium antimony tartrate, potassium
pyroantimonate, sodium dichromate, boric acid, ferric chloride,
zirconium and titanium complexes or other metal compounds.
[0094] Preferably, the cross-linking agent, or the final portion of
the crosslinking system, is incorporated into the explosive
composition subsequent to the explosive composition being passed
through a pump that is used to load the explosive composition into
the borehole. However, a portion of the crosslinking system
(preferably potassium antimony tartrate) may be added to the liquid
phase. It will be appreciated that the cross-linking agent may be
added by any means known in the art.
[0095] The cross linking agent may be added at a rate of 0.01-0.10,
preferably about 0.05 wt. %, based upon the total weight of the
explosive composition.
[0096] The explosive composition may also include other additives
that are known in the explosive art such as potassium iodide and
stearic acid. Preferably, the explosive composition comprises less
than about 15 wt. % aluminum, more preferably less than 5 wt. %
aluminum and, most preferably, essentially no aluminum.
[0097] In one embodiment, the explosive composition may have a pH
from 3 to 7, preferably from 4 to 6 and, most preferably from 4.5
to 5.5. If the pH is less than about 4, then the gelling action of
the guar gum is reduced due to acid hydrolysis and additional
amounts of guar gum must be utilized. If the pH is greater than
about 6, then premature gellation of the guar will commence and
increased microbial attack of the guar is possible.
[0098] The explosive composition utilizing these ingredients
preferably has a density from about 1.05 to. 1.4 g/cc, more
preferably 1.15 to 1.30 g/cc and, most preferably 1.22 to 1.28
g/cc.
[0099] The explosive composition has a viscosity that is
sufficiently low to render the watergel explosive composition
pumpable when passed through a pump. This explosive composition
exhibits a shear thinning rheology. When the explosive composition
is essentially stagnant (e.g. at 2 rpm and 21.degree. C.) the
explosive composition has a viscosity from about 50,000 to 300,000
cps, preferably from 75,000 to 200,000 cps and, most preferably
from 100,000 to 150,000 cps. When passed through a pump, the
viscosity is reduced to render to composition pumpable. It is well
understood by those skilled in the art whether an explosive
composition is pumpable. Preferably, the explosive composition has
a viscosity of less than 35,000 cps at 20 rpm and 21.degree. C.,
preferably less than 20,000 cps and, more preferably less than
15,000 cps. Such explosive compositions can be passed through pumps
that are utilized to load boreholes without the pump being
overstressed and without excessive pressure being applied to the
explosive composition. After being passed through a pump, the
crosslinking agent, or the final portion of the crosslinking
system, is preferably added prior to the end of the hose.
[0100] In accordance with one embodiment of the instant invention,
all of the feed materials may be combined at one particular
location to produce the explosive composition. Alternately, the
liquid phase may be prepared separately and stored for use later or
transported to an alternate location. For example, the liquid
phase, which is classified as an explosive composition may be
prepared at a central facility and then shipped to various sites,
such as blasting sites or secondary manufacturing locations,
whereat the liquid phase is combined with, e.g., miniprills or ANFO
to produce the final explosive composition.
[0101] If the liquid phase is prepared separately, then the liquid
phase may comprise a mixture of the solubilized chemical
sensitizer, the solvent and the gelling agent, and optionally up to
30 wt. % ammonium nitrate or other inorganic oxidizing salt.
Alternately, the liquid phase may also have incorporated therein
some cross linking agent and/or some insoluble sensitizer (e.g.
perlite and/or ceramic microspheres) and, more preferably,
insoluble sensitizer and the cross linking agent. Accordingly, the
explosive composition may be prepared by blending miniprills or
ANFO with a liquid phase comprising the remaining reagents.
EXAMPLE
[0102] An explosive composition was prepared according to the
instant invention by combining the following ingredients which are
set out in Table 1. TABLE-US-00001 TABLE 1 Feed material Weight %
Aqueous MMAN Solution (69 wt. %) MMAN) 21.67 Water 2.50 Potasium
antimony tartrate 0.01 Ceramic Microspheres 2.00 Guar Gum 0.36
Perlite 0.15 ANFO (95.9 wt. % miniprills/4.1 wt. % fuel oil) 73.31
Total 100.00
[0103] The explosive composition was prepared by initially
preparing the aqueous MMAN solution. The aqueous MMAN solution,
additional water and the potassium antimony tartrate were added to
a tank and stirred to blend the ingredients. The ceramic
microspheres was added while the ingredients were being stirred in
the tank. Subsequently, the guar gum was added and the mixing was
continued for two minutes. At the end of two minutes, the perlite
and ANFO were added and the mixing continued until the explosive
composition had a uniform consistency.
[0104] The explosive composition had a pH of 4.9 and a density of
1.28 g/cc. The viscosity of the explosive composition was then
measured as made and after storing the explosive composition
overnight and for four days. The results are set out in Table 2.
TABLE-US-00002 TABLE 2 Mix Units As Made 15 C. pH none 4.9 Density
g/cc 1.28 Visc@2 rpm and 15.degree. C. cps 110,000 Visc@20 rpm and
15.degree. C. cps 16,000 Overnight 24 C. pH none 4.9 Density g/cc
1.28 Visc@2 rpm and 24.degree. C. cps 135,000 Visc@20 rpm and
24.degree. C. cps 19,500 Four Day 20 C. pH none 4.8 Density g/cc
1.32 Visc@2 rpm and 20.degree. C. cps 107,500 Visc@20 rpm and
20.degree. C. cps 18,500
[0105] As can be seen from the forgoing, the viscosity of the
explosive composition at low rpm was over 100,000 cps. However, at
20 rpm (i.e. simulating being passed through a pump), the viscosity
reduced substantially thereby exhibiting a shear thinning
rheology.
[0106] The explosive composition was then crosslinked by adding
0.04 wt. % sodium dichromate before being detonated. The explosive
composition was tested by loading it into a steel pipe, inserting
the appropriate booster, initiating the booster, and measuring the
velocity of detonation.
[0107] The results are set out in Table 3. TABLE-US-00003 TABLE 3
Diameter Booster Velocity of (mm) Weight (grams) Detonation (m/s)
100 454 4900 75 227 4100 50 227 2800
* * * * *