Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to such explosive compositions frequently
called slurry explosives consisting of an aqueous composition of oxygen-
supplying salts and a fuel. More particularly, the invention relates to such
explosive compositions in which the fuel is or comprises a liquid substance
substantially insoluble in water.
In the patent literature substances of most various kinds have
been discussed as oxidant and fuel components in the so-called slurry explos- :
ives. Among solid substances which are not self-explosive, bituminous sub-
stances and many other organic substances and various metals have been sug-
gested and put into use. These substances have in common that the degree to
which these fuels are finely dispersed is important to the properties of the
explosive manufactured therefrom.
Slurry explosives which contain a liquid, substantially water-
insoluble fuel are known. The most frequently discussed slurry explosives of
this group contain hydrocarbons of various kinds, normally petroleum fractions
called fuel oils or diesel oils as the fuel component of the composition.
Thus, the manufacture of explosives of this kind is known from
U.S. Patent Specification 3,161,551. In said specification the use of a hydro-
phobic emulsifier is also suggested, in which the emulsifier is able to form a
water-in-oil emulsion as a characterising feature of the explosive disclosed.
In Australian Patent 281,537 similar explosives have been disclosed and also
the use of anionic surface active substances therein. Such explosives which
contain a substantially water insoluble liquid fuel normally also contain
thickening agents of known character, preferably guar gum and, naturally, also
can contain other components. Thus, explosives which contain aluminium pow-
der in addition to a fuel oil have been disclosed in IJ.S. Patent Specifica-
tion 3,094,069.
Naturally, in the case also of such liquid fuel aqueous explos-
ives, there are a number of important factors governing the properties of the
product, namely: the extent to which such fuels are finely dispersed, how the
emulsion of fuel and the aqueous salt solution is provided and the stability
of the emulsion or dispersion. Thus, it has been stated that the emulsifiers
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used should be hydrophobic and stabilize a water-in-oil emulsion. It has
also been suggested to allow the fuel to be absorbed by the ammonium ni-
trate in the form of porous prills before this is used in the production of
the final composition.
The present invention is based on the discovery that lignosul- ;
phonates available from the so-called sulphite liquors in the production of
wood pulp according to the sulphite cellulose process, is particularly well
suited to the preparation of aqueous slurry explosives containing a liquid
fuel, in that the liquid fuel is very easily dispersed in an aqueous salt
solution containing such lignosulphonates and the emulsion obtained is very
stable. These lignosulphonates are water soluble, in contrast to the pre-
viously suggested emulsifiers for slurry explosives comprising liquid fuels,
and it is presumed that the lignosulphonates stabilize an emulsion of the
oil-in-water type. The emulsifying and emulsion stabilizing effect of lig-
nosulphonates is previously known ~ se, but it has not been known that
this effect is so evident in a system in which the water phase is a saturated
solution of oxygen supplying salts, especially the preferred nitrates.
Using lignosulphonates in slurry explosives is previously known
from Canadian Patent 784,636, issued May 7, 1968 to Canadian Industries
Limited. In this patent there are disclosed only slurry explosives in which
the fuel consists of solid substances or water soluble substances. The spe-
' cification does not disclose any use of or particular advantages of lignosul-
phonates in connection with watér-insoluble liquid fuels which is a character-
ising feature of the present invention.
In said Canadian patent lignosulphonates are designated a sensi-
f tizer, i.e. an agent which increases the sensitivity o~ the explosive to ini-
~i tiators, however, without presenting any explanation of, or theory for, this
; sensitizing effect. This sensitivity increasing effect is present also when
the fuel is a water-soluble liquid substance.
U.S. Patent 3,617,407 to Craig and Falconer, issued November 2,
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1971 refers to slurry explosives comprising a combination of cross-linked
galactomannan with psyllium flour as a thickener. Certain examples of slurry
explosive compositions containing ammonium lignosulphonate are given, but
none includes this agent together with a liquid fuel. -
Thus, the inventive concept resides mainly in the fact that the
very same substance is both an effective emulsifier for liquid fuels and a
sensitivity increasing component of the composition. Furthermore, it is a
feature of the present invention that lignosulphonates have additional advan-
tageous effects relative to previously known emulsifiers for slurry explos-
ives comprising liquid fuels. In many cases it is advisable to convert the
aqueous thickened salt solution of the explosive into a gel by means of a
so-called crosslinking agent for the high polymer molecules of the thickener,
thereby providing inter alia a considerably improved water resistance to the
explosive. As crosslinking agents, compounds of heavy metals from
Groups IV, V and VI of the Periodic System in their highest valence states
are particularly mentioned, such as chromates, antimonates or titanates. It
is known that such crosslinking reactions or gel formation proceed more ra-
pidly or more completely in the presence of reducing agents. Thus, it is
also a feature of the present invention that lignosulphonates are suitable as
such reducing agents for promoting gel formation, a property not shared with
previously suggested emulsifiers. Thus, considered as a whole, it has sur-
prisingly been found that lignosulphonates have no less than three separate
advantageous effects in the explosives of the present invention, which rend-
ers the use of different components for each of said functions superfluous.
Finally, it is a feature of the present invention that the use
of lignosulphonates in connection with liquid fuels gives rise to consider-
able economic advantages. Lignosulphonates are much cheaper than most known
or suggested emulsifiers for slurry explosives comprising liquid fuels. They
are also cheaper than the reducing agents which have been suggested for
crosslinking reactions with chromates and antimonates. Also, considered in
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relation to the use of solid fuels, the present invention means that all ex- -
penses for crushing and grinding of the solids are avoided, since the disper-
sion of the liquid fuels takes place during the mixing operation for preparing
the finished explosive. Furthermore, an economic advantage lies in the fact
that common fuel oil is cheaper than most solids which have been suggested up
to now as fuels in slurry explosives.
Accordingly,the present invention provides an aqueous, slurry type
explosive composition comprising an inorganic oxidant, a fuel, a thickener and
a surface active agentJ said composition being free from any self-explosive
component, the improvement which comprises using in combination a fuel com-
ponent which is a liquid, substantially water-insoluble hydrocarbon and, as
surface active agent, a lignosulphonate in an amount of about 0.5 to 5% by
weight of the composition.
In the practice of the present invention no method is critically
important and the mixing of the explosive components may be carried out in
many different ways. A preferred method is to prepare an aqueous solution of
the oxygen supplying saltts), thickener(s) and lignosulphonates and thereafter
add the liquid fuel in a simple mixing operation, wherein certain quantities
of undissolved salts and other combustible substances, such as metal powder
or the like, may be added. Auxiliary agents in small quantities to control
the density and consistency of the explosive, such as gas generating reagents,
e.g. sodium nitrite and crosslinking agents such as chromates, titanates or
antimonates, respectively, may be added in the same mixing operation, if de-
slred.
The mixing operation and the equipment for carrying out the oper-
ation are neither critical to the practice of the invention, but a certain
effect of the mixing intensity can sometimes be observed on such quality
parameters of the explosive as the critical diameter.
Thus, a prepared solution of oxygen supplying salts, thickeners
and a lignosulphonate may be brought together with the liquid fuel and op-
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tionaLlly other components in a plastic bottle and shaken by hand, whereby
within one minute a sufficiently intimate mixture is obtained which can be
squeezed out of the plastic bottle into suitable tubes or the like and then
successfully detonated by means of conventional initiators. Obviously, the
same mixing operation may be performed chargewise in so to say any size
mixing equipment whereby mixing periods of the order of one ~r a few minutes
usually will be sufficient. A particularly preferred method in carrying out
the mixing operation is to allow the aqueous solution of the oxygen supplying
salt or salts, thickeners and the lignosulphonate to continuously run to-
gether with the liquid fuel, optionally simultaneous supply of some quantities
of undissolved salt and combustible solids and other agents, into a mixing
chamber with a mechanical stirrer, from which chamber the ready prepared ex-
plosive flows continuously and is pumped either directly into a blast hole or
to a cartridging machine of suitable kind.
In such a continuous mixing operation whereby accumulation of
large quantities of ready made and detonable explosive is avoided, the volume
of the mixing chamber may be as small as 1 to 2 litres for a flow through of
an explosive quantity with a volume of about 20 litres per minute. By such
means the mixing operation may be carried out between 3 to 6 seconds as an
average with such an effective emulsification of the liquid fuel in the salt
solution that the explosive produced is fully satisfactory for application in
blast holes of diameters above 2 inches.
W~en practising the invention it is not critical what kind of lig-
nosulphonates are being used or in which form they are present. Thus, so-
called sulphite liquors evaporated to a solids content of about 50%, the rest
substantially being water or substances evaporated to dryness and present as
powder may be used. Lignosulphonates of sodium, calcium, magnesium and am-
monium may be used, dependent of which bases are used in the sulphite cellu-
lose process. Nor is it critical in any way in practising the invention
whether the lignosulphonate material contains various other water soluble com-
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ponents, such as various sugars extracted from the raw material for the pro-
duction of cellulose, or whether these sugars are removed by fermentation be-
fore evaporating to about 50% or nearly to 100% dry content.
The lignosulphonates which according to the invention should be
included in the final explosive composition are being used in amounts of up
to 5% of the total composition and preferably in amounts of between 0.5 and
2%.
To further illustrate the invention the following examples are
given on some embodiments of the invention wherein both the mixing operations
are carried out in different ways and wherein some examples have been carried
out without lignosulphonates for comparison of the obtained results.
Examples
In the following table a total of five examples are summarized,
Examples 4 and 5 ~eing outside the scope of the invention and included for
reasons of co~parison since they either do not contain lignosulphonate or do -
not contain a liquid fuel.
The method of preparation is also varied, but all examples have
in common that a solution consisting substantially of nitrates and water is
first prepared and maintained at a temperature of about 45C. until the mixing
1 20 operation with the remaining components is taking place. In this solution
! there are also included: the thickener guar gum which is first dispersed in
glycol to prevent lump formation; furthermore, thiourea as a reaction partner
for the nitrite aerating agent so that a certain amount of nitrogen is gener-
ated and finely distributed throughout the final mixture; and also the anti-
foaming agent "Foamaster* 50D", marketed by the company Nopco Senco, to avoid
, varying occlusions of air in the explosive composition. Finally, the solution
according to all examples except Example 4 contains a lignosulphonate, viz.,
the commercial product denoted "Totanin MG" from A/S Toten Cellulosefabrikk,
Nygard, Norway.
The ammoniu~ nitrate used is a commercial grade available in
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prilled form. The lime saltpeter being used is also a commercial grade in
the iorm of prills containing about 15% of water and about 6% of ammonium
nitrate in addition to calcium nitrate.
As fuel a diesel oil of normal commercial grade was used except
Example 5, where the fuel was a finely ground gilsonite which is a high car-
bon, low ash, natural asphalt.
The auxiliary substances sodium dichromate for crosslinking the
guar gum and sodium nitrite for generating nitrogen are added during the
final mixing operation in the form of separate solutions, 50% and 25% concen-
tration, respectively. All figures in the composition table are given in
weight percent.
TABLE I is
Composition No. 1 2 3 4 5
Solution:
Ammonium nitrate 29.0029.00 29.00 29.33 29.00
Lime saltpeter, 28.1828.18 28.18 28.18 28.18
Commercial grade
Water 6.29 6.29 6.29 6.29 6.29
Thiourea 0.13 0.13 0.13 0.13 0.13
Guar gum 0.36 0.36 0.36 0.36 0.36
Lignosulphonate 0.53 0.53 0.53 - 0.53
Ethylene glycol 0.78 0.78 0.78 0.98 0.78
Ant foaming agent 0.03 0.03 0.03 0.03 0.03
Fuels:
Diesel oil (fuel oil) 6.50 6.50 6.50 6.50
Gilsonite - - - - 6.50
Undissolved ammonium nitrate28.00 28.00 28.00 28.00 28.00
uxiliary substances:
,. .
Sodium dichromate 0.10 0.10 0.10 0.10 0.10
Sodium nitrite 0.10 0.10 0.10 0.10 0.10
Different mixture methods are used in the various embodiment
examples.
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In Example 1 the solution, fuel, dry ammonium nitrate and auxili- `
ary substances are brought together in the order mentioned in a plastic bottle
having a volume of about 2 litres and shaken together for about 15 seconds.
Thereupon the prepared mixture, before a complete crosslinking of the guar
gum has taken place, is transferred into cardboard tubes of various diameters
for testing of the explosive quality parameters.
In Example 2 the composition has been prepared in a mixing appa-
ratus commonly used for bakery purposes with a mixing vessel having a volume : -
of about 25 litres. After charging the solution the fuel oil was added and
stirred until the mixture looked homogeneous, which was obtained within about ~ -
one minute. During somewhat more vigorous stirring dry ammonium nitrate and
the auxiliary substances were added and stirring maintained for about one
minute. Then the prepared mixture was put into cardboard tubes as in Example
1,
In Examples 3, 4 and 5 a continuous mixing process was used where-
in the components were passed into a mixing chamber having a volume of about
1 litre. The charging rate was about 10 kgs per minute and samples of the
final mixture were brought into cardboard tubes of various diameters for the
determination of the critical diameter. In all cases the density of the pro-
duct was about 1.15 g/cm . The results are stated in Table II. The stated
critical diameter for the explosive mixtures is the smallest diameter where
a tube, having a length 6 times the diameter, detonates completely unconfined
1 having been cooled down to 5C. and initiated with a primer. As primer for
; tube diameters below 84 mm 32 g of trinitro-toluene has been used, in the
table denoted as "A", whilst for larger tube diameters 360 g of pentolite
(55% pentrite, 45~ trinitro-toluene), in the table denoted "B" has been used.
TABLE II
Example No. 1 2 3 4 5
I Primer, type: A A A B B
-' 30 Critical diameter, inches: 2 2 3/4 2 3/4 4 >5 3/4
.. , _ g _
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From the above results it can be seen that with diesel oil as
fuel lignosulphonate provides a critical diameter below 3 inches whilst lack
of lignosulphonate, all other conditions being unchanged, provides a critical
diameter of 4 inches even with a substantially stronger primer. Other lig-
nosulphonate compositions provided results nearly identical to those obtained
with "Totanin MG". For a solid fuel, gilsonite, even with lignosulphonate it
is obtained a critical diameter above 5 3/4 in. which was the largest diameter
tested.
It will also be seen that the rapid mixing by shaking in a plas-
tic bottle provides a somewhat lower critical diameter than a mechanical mix-
ing whilst the continuous mixing and the mechanical chargewise mixing are of
equal value.
A series of tests have been performed with emulsifiers other than
lignosulphonate. The agents tested were stated by the suppliers to be effect-
ive for emulsification of oil in water containing salts, and are presented in
Table III.
TABLE III
Designation Supplier
"LDC Base"~ Company Nopco Senco, Drammen, Norway
"1225-L" " " " " "
"1186 A" " ll
"Type 09" Hexamin Products, R~yken, Norway
"Type 79/02" " " " "
"Berol 525" B~rol Kemi AB, Stenungsund, Sweden
"Berol 259"
Nonylphenol Imperial Chemicals Ltd., London, England
Using the same mixing conditions as applied for Example 1 and
with componen~s otherwise as in Example 4, none of the commercial emulsifiers
stated above produced a homogenity even approximating that achieved by the
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lignosulphonate, and usually non-emulsified oil was observed floating freely
on the surface of the mixture. In no case was a critical diameter determined
below 4 inches for these mixtures.
Finally, it should be mentioned that an explosive mixture having
a composition as in Examples 1, 2 and 3 was produced by a continuous mixing
method according to Example 3 but in a larger apparatus having a mixing
chamber volume of about 8 litres and with a feed rate of 150 kgs per minute.
The discharge from the mixing chamber was pumped through a hose of 1 1/2
inches bore and 82 feet long directly into a blast hole in an open cast iron
; 10 ore mine. The blast hole diameters were from 8 to 12 inches. Upon initiation
with two pentolite primers of 360 g in each blast hole, such compositions de-
tonated completely and showed very satisfactory blasting results.
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