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Патент USA US3032460

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United States Patent O?ice
2
1
3,032,450
AMMONIUM NITRATE EXPLOSIVE AND
ITS PRODUCTION
Jennings P. Blackwell, Bartlesville, Okla, assignor to
Phillips Petroleum Company, a corporation of Dela
ware
No Drawing. Filed Apr. 1, 1958, Ser. No. 725,480
19 Claims. (Cl. 149-7)
> 3,032,450
Patented May 1, 1962
trate. A still further object of the invention is to pro
duce a combustible-coated ammonium nitrate particle.
A further object still is the production of a combustible
coated ammonium nitrate particle in which the coating is,
at least in part, found within cracks in the surfaces of the
particle.
'
Other aspects, objects and several advantages of the
invention are apparent from this description and the
claims.
According to the present invention, there is provided
This invention relates to an ammonium nitrate explo 10
a method for the preparation of a detonatable ammonium
sive and to its production. In one of its aspects, the
nitrate composition from a coated ammonium nitrate
invention relates to the conversion of an ammonium
product unsuitable for use as an explosive because of its
nitrate fertilizer which has been clay-coated and which
poor detonatability which comprises intimately contacting
is not readily detonatable to a readily detonatable explo
sive ‘by removing the clay coating and adding a com 15 said coated ammonium nitrate with a combustible which
is liquid under the treating conditions for a time and in
bustible liquid. In another of its aspects, the invention
a manner so as to remove the coating from the ammo
relates to a method of converting such a fertilizer grade
nium nitrate and to coat the same with said combustible,
ammonium nitrate as has been described in a manner as
and recovering said combustible-coated ammonium ni
described by heating and agitating together a combustible
which is liquid under the conditions of operation and 20 gtrate from the treating mass.
said ammonium nitrate until the clay-coating thereon has
been substantially replaced with said combustible mate
rial. In another of its aspects, the invention provides
an improved ammonium nitrate explosive by heating the
Thus, the process of the present invention comprises
the steps of removing the clay coating from the ammo
nium nitrate and forming an explosive composition of
uncoated ammonium nitrate which is soaked with a com
combustible-coated nitrate to a temperature at which the 25 bustible which is liquid under the treating conditions
and such that it will not hinder the detonation of the
nitrate passes through a phase transition which causes
?nal product of the invention, the combustible being
cracking of the nitrate and allows the oil to soak into
usually a petroleum hydrocarbon such as diesel oil, gas
the individual particles thereof.
oil, etc. The process can be practiced readily by form
The conventional clay-coated ammonium nitrate which
is the ordinary commercial product used for fertilizer is 30 ing, for example, in a jet-agitated vessel, a slurry of coated
not readily detonatable and when mixed with the proper
amount of combustible material, such as petroleum hy
drocarbon, which is used in the preparation of detonatable
ammonium nitrate prills with diesel fuels or oils, such
as a gas oil, the moving hydrocarbon removing the clay
from the prills and forming a suspension of the clay in
ammonium nitrate, the said commercial product produces
the hydrocarbon. The clay is removed by draining the
old in the art. The ammonium nitrate is intimately
off the excess liquid hydrocarbon and suspended clay.
Continuous operation is within the scope of the invention
35 excess hydrocarbon and suspended clay from the prills.
a rather difficulty detonatable material.
This is accomplished in a batch operation by draining
Explosives with ammonium nitrate as the oxidizer are
mixed with or ‘soaked with a combustible material such as
and can be practiced by providing an agitating zone adja
materials. It has been established that detonation char 40 cent a conveyor zone, the coated prills being fed to the
agitation zone for agitation with the oil and passed
acteristics are favorably affected by low moisture content
through the conveying zone wherein the prills are allowed
of the ammonium nitrate, this ordinarily being below 1.5
to settle and the supernatant oil layer is decanted. The
weight percent, and by intimate contact between the am
prills are allowed to drain until the oil-soaked prills are
monium nitrate and the combustible material.
about ?ve to ten percent by weight oil and the remainder,
It is known that there are a number of variables which
peat, petroleum distillates or residues, coke, and similar
a?ect the ease of detonation of ammonium nitrate ex
ammonium nitrate. The explosive composition is then
ready for use. Agitation is ordinarily discontinued while
plosives. Included among these variables, which are
draining away the hydrocarbon containing the suspended
known to one skilled in the art of ammonium explosives,
clay. However, some agitation, at least of the hydro
are the following which are applicable to ammonium
nitrate and mineral oil mixtures: ?neness of ammonium 50 carbon phase, can be provided to insure good suspension
of the clay therein, in the event some settling of the clay
nitrate; ?neness of combustible, when it is a solid at ordi
which is, in the speci?c instance, undesirable, is occur
nary temperatures; 'diiferences in the method of coating
ring. Ordinarily, some clay in the ?nal product, not
the ammonium nitrate with the combustible; differences
usually more than that suspended in the oil coating, will
in the speci?c types of combustible materials used; varia
tion of the moisture content.‘
55 not be objectionable. Indeed, the ?nal product appears
to be quite suitable when it contains some clay.
The ready and general availability of fertilizer grade
Also, according to the present invention, there is pro
ammonium nitrate makes it desirable as a material for
vided the important and now preferred feature of drying
use in explosives. However, as noted, the clay-coated
commercial product is unsuited for explosive purposes.
the ammonium nitrate during the removal of the clay
I have now found that if the conventional clay-coated 60 coating therefrom for some time thereafter. This is ac
complished by heating the oil-ammonium nitrate mixture
ammonium nitrate fertilizer is agitated with a petroleum
preferably with agitation and preferably providing for
hydrocarbon, such as a gas oil or diesel fuel, until the
the removal of vaporized water with an entrainer gas, for
clay coating has been removed from the nitrate particles
example, in a ‘sweep stream of natural gas. The liquid
and the oil coated thereon, that the ammonium nitrate
which is thus freed of the clay coating and soaked vwith 65 hydrocarbon used in this modi?cation is preferably a low
volatility fraction such as described since this facilitates
the liquid hydrocarbon has good detonating properties.
nium nitrate explosive. It is another object of this inven
operation without high concentration of vapors of liquid
hydrocarbons being found in the exit sweep gas. Other
tion to provide a method for the preparation of an ammo
wise, more volatile combustible materials can be used
It is an object of this invention to provide an ammo
nium nitrate explosive. It is a further object of the in 70 which would be those known in the art. The liquid hy
drocarbon or other combustible material, if desired, can
vention to provide a method for producing an ammonium
contain particles of carbon black or other materials which
nitrate explosive from a fertilizer grade ammonium ni
3,032,450
are found to preferentially deposit with the combustible
on the nitrate particle.
When heating is practiced according to the invention,
it is practiced for, at least, one of several reasons.
One reason for heating the oil-coated prills is to pass
the prills through a phase transition point which occurs
at about 90° F. Such heating is useful even though no
4
The ammonium nitrate is at least for the most part
available as prills within the range of 10 to 20 mesh in
size. Some of the fertilizer is available as crystallized
ammonium nitrate, and a small part is available as a
ground product. These latter products may contain a
considerable amount of particles ?ner than 20 mesh and
as ?ne as 40 mesh.
The clay coating on the ammonium nitrate is usually
diatomaceous earth, although a relatively minor portion
through a phase transistion point at about 90° F. causes
a rather large volume change to take place which aids 10 of the fertilizer is coated with kaolin, fuller’s earth or
other clays. The amount used varies to some extent, but
in cracking the prills and allowing the oil to enter them
31/2 percent (based on the total) is a representative
more readily. This is also advantageous in the formation
amount.
of a uniform mixture and in contacting intimately the oil
Reasonable variation and modi?cation are possible
and the nitrate.
within the scope of the foregoing disclosure and the ap
Another reason for heating is, of course, the dehydra
pended claims to the invention, the essence of which is
tion of the ?nal product to bring it within the desired
that a fertilizer grade clay-coated ammonium nitrate is
known low water content iimit. The heating can be
rendered suitable for use as an explosive by replacing
accomplished at any time during the operation, for ex
the clay-coating of the ammonium nitrate with a com
ample, during agitation or thereafter. When heating is
practiced, it is practiced to increase substantially the vapor 20 bustible material such as a hydrocarbon, substantially as
set forth and described herein.
pressure of the water and preferably, the temperature
I claim:
will be at or above the boiling point of water, for ex
1. A method for the conversion of a clay-coated fer
ample, in a range of from about 210 to about 225° F.
tilizer grade ammonium nitrate to an explosive which
The heating time usually is in the range of live minutes
to two hours, more usually in the range from about ten 25 comprises admixing said ammonium nitrate with a liquid
petroleum hydrocarbon, agitating the mixture until sub
minutes to one-half hour. The excess oil, if any is pres
stantially the entire clay coating has been removed from
cut when heating occurs, is drained and the oil or com
the particles of the ammonium nitrate and the particles
bustible material coated prills cooled, thus yielding a
have been coated with the liquid petroleum hydrocarbon,
composition ready for use in blasting.
removing any liquid in excess of that wetting the par
The blasting compositions formed by the process of
ticles, and recovering an explosive liquid-coated ammo
this invention can be used in a conventional and known
nium nitrate.
manner, they can be packed in bags or other containers
2. A method according to claim 1 wherein said liquid
for placing in the hole, and, for use in wet locations, the
petroleum hydrocarbon has a boiling point in the range
containers are preferably water-proof. These containers
can be, for example, paper, cloth or plastics such as 35 of about 250° F. to about 800° F.
3. A method according to claim 2 wherein the excess
polyethylene.
liquid is removed until the liquid-coated ammonium ni
Example I
substantial dehydration is practiced. Thus, the passing
Prilled uncoated ammonium nitrate as used in the prep
aration of coated ammonium nitrate of fertilizer grade
and having an average particle size of 14 mesh was
soaked with 7 weight percent diesel fuel and then deto
nated in cardboard tubes with Primacord as an initiator.
A similar mixture made with clay~coated ammonium
nitrate prills would not detonate under the same condi
tions. indeed, it would not detonate when'dynamite
booster was used. Several mixtures of the uncoated
ammonium nitrate soaked with 7 Weight percent diesel
fuel and several of the similar mixtures with clay-coated
ammonium nitrate prills which would not detonate, were
prepared to con?rm the ?rst-reported ?ndings of this ex
ample.
Example If
trate particles are in the range of about 5 to about 10
weight percent liquid petroleum hydrocarbon.
4. A method according to claim 3 wherein the liquid
coated ammonium nitrate particles are heated to pass the
ammonium nitrate through a phase transition which occurs
at about 90° F.
5. A liquid petroleum hydrocarbon ammonium nitrate
explosive prepared according to the method of claim 4.
6. A method for the conversion of a clay~coated fer
tilizer grade ammonium nitrate to an explosive which
comprises admixing said ammonium nitrate with a liquid
petroleum hydrocarbon, agitating the mixture until sub
stantially the entire clay coating has been removed from
the particles of the ammonium nitrate and the particles
have been coated with the liquid petroleum hydrocarbon,
removing any liquid in excess of that wetting the par
grade and diesel fuel and a mixture of uncoated ammo
ticles, and heating the liquid-coated ammonium nitrate
particles to pass the ammonium nitrate through a phase
nium nitrate and diesel fuel were prepared and detonated
transition.
con?ned in an iron pipe. The initiators were dynamite
boosters set off with a small amount of Primacord.
(Samples con?ned in an iron pipe can be detonated in
7. A liquid petroleum hydrocarbon ammonium nitrate
explosive prepared according to the method of claim 6.
A mixture of coated ammonium nitrate of fertilizer
certain instances where the lower degree of con?nement
of a cardboad tube will not result in detonation.) The
uncoated ammonium nitrate and diesel fuel mixture deto~
nated with 54 plastic cards between the initiator and
the explosive. The clay-coated ammonium nitrate-diesel
fuel mixture detonated with a maximum of 12 cards be
8. A method for the preparation of an explosive com
position which comprises intimately contacting ammo
nium nitrate particles with a liquid petroleum hydrocar
bon and heating the thus-formed mixture at least to a
temperature at which the ammonium nitrate passes
through a phase transition, thereby producing cracks in
the surfaces of the ammonium nitrate particles, the cracks
being, at least in part, ?lled with said liquid petroleum
tween the initiator and the explosive. Several of each
of the mixtures were prepared to con?rm the ?ndings
hydrocarbon.
reported in this example.
position which comprises intimately contacting ammo
nium nitrate particles with a liquid petroleum hydrocar
Petroleum hydrocarbons particularly suited for use in
this invention are those boiling in the range of 250° F.
to 800° F., preferably from about 300° F. to 700° F.
These ranges include distillates known in the petroleum
re?ning art as kerosene, gas oil, diesel fuel, stove oil, and
numerous others.
9. A method for the preparation of an explosive com
bon and heating the thus-formed mixture to pass the
ammonium nitrate through a phase transition which occurs
at about 90° F.
10. An explosive composition prepared according to
claim 8.
3,032,450
5
11. An explosive composition prepared according to
claim 9.
12. A method according to claim 1 wherein during
the removal of the coating, said ammonium nitrate and
said liquid petroleum hydrocarbon are heated and an
entrainer gas is passed through the mass to facilitate
removal of water from said ammonium nitrate.
13. A method according to claim 1 wherein the mix
ture is heated during agitation.
14. A method according to claim 1 wherein the mix 10
ture is heated to a temperature in the range of approxi
mately 210-225° F.
15. A method according to claim 1 wherein said liquid
petroleum hydrocarbon is diesel fuel.
16. A method according to claim 1 wherein said liquid
petroleum hydrocarbon is gas oil.
17. A method according to claim 1 wherein an en
trainer gas is passed through the mixture during said step
of agitating.
6
tilizer grade ammonium nitrate to an explosive which
comprises admixing said ammonium nitrate with a hydro
carbon liquid having a low volatility at the boiling point
of water, agitating the mixture until substantially the
entire clay coating has been removed from the particles
of the ammonium nitrate and the particles have been
coated with the hydrocarbon liquid, removing any liquid
in excess of that wetting the particles,‘ and recovering
an explosive liquid-coated ammonium nitrate.
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,071,949
1,992,217
2,590,054
O’Brien ______________ __ Sept. 2, 1913
Kirst et al ____________ .__ Feb. 26, 1935
Taylor et a1 ___________ __ Mar. 18, 1952
OTHER REFERENCES
Perry: Chemical Engineers’ Handbook, 3rd Edition,
18. A method according to claim 17 wherein the en 20 3rd Impression, 1950, p. 1118.
Daugherty: Chemical and Engineering News, October
trainer gas is natural gas.
7, 1957, pp. 62 and 63, 52-05 S & L.
19. A method for the conversion of a clay coated fer
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