CA1259492A - Emulsion-containing explosive compositions - Google Patents

Abstract

TITLE
Emulsion-Containing Explosive Compositions ABSTRACT OF THE DISCLOSURE
In emulsion blend explosives, the replacement of coarse salt particles, e.g., prills, by fines, i.e., particles which pass a No. 50 U.S. sieve, increases the water resistance of the explosive without deleteriously affecting its shelf life provided that the explosive, prior to such replacement, is storage-stable as determined by the Salt Extraction and lead compression tests described herein. Products containing a combination of whole and crushed ammonium nitrate prills, and emulsions made with an anionic emulsifying agent such as a fatty acid salt, are preferred. Depending on the fines content and chemical compostion, other properties such as sensitivity to initiation and detonation velocity also may be improved.

Description

~25~
~P-0057 T I TLE
Emulsion-50ntaining Explo~ive Composition6 BACKGROUND OP l'HE_INV~TION
~ield of the Invention The present invention relate~ to explo6ive compositions comprising a 6enfiitized blend of a water-in-oil emulfiion and ~olid particulate inorganic oxidizing ~alt, preferably ammonium nitrate (AN).
DescriPtion of the Prior Art Explo~ive~ which compri6e a blend of a water-in-oil emulsion and solid particulate AN, e.g., AN~O (AN prill6 coated with fuel oil), are becoming increasingly popular with blaster~ owing to the fact tha~ they are able to offer the advantage6 of high bulk density and blasting energy characteristic of emul~ion explosives, while at the same time resulting ~n c06t reductions owing ~o the lower cost of the AN.
In ~ome ~n~ance6, howevec, the~e blend explosive products, refer~e~ to here~n ~8 "emul~ion blend explosives", have been found to have a ~hort 6helf life, requiring the use of the products im~ediately after they have been ~ormed. "Short 6helf life" means that an explosive product lack~ 6tability, undergoing deleteriou6 change(s) in ~tructure and/or compo~ition to the degree that it cannot be depended upon to detonate at the required velocity at the required time. lf the product's 6helf life i very short, it almost cectainly i~ un6uitable for u6e in packaged form, and can be un6uitable for ufie in bulk form, e6pecially if it need~ to be transported to the place of u6e or allowed ~o ~tand in a borehole for some time after loadingO
U.S. Patent No. 4 555 278 issued November 26, 1985 to L. A. Cescon and N. J. Millet, Jr., describes the formation of emulsion blend explosives having imploved storage stability.
This application states that in these explosives, the blend-destabilizing transport or loss of water from the emulsion's aqueous dispersed phase across the continuous oil phase to the admixed nitrate par~icles i6 minimized by virtue of a barrier or medium, resistive to wa~er-transport, ~ormed preferably b~ the continuous emulsion phase itself, e.g., by the pre6ence of an anionic emulsifying system comprising a lo atty acid ~alt and a free fatty acid, the latter in solution in an oil as the continuous emulsion phase.
The same patent application further states that a water-transport-resistive barrier also can be provided, for example, by a low-diffusivity (to water) coating on the nitrate particles.
One of the ma~erials which is commonly employed as the particulate solid component of emulsion blend explosives is ANFO. While ANFO i& a popular blasting product in its own right because of economy and convenience, it~ lack of water resistance and low product density are well-recognized as product deficiencies. ~he blending of ANFO with a water-in-oil emulsion results in a product of higher densi~y, and a certain degree of water resistance may be achieved in the blend product, especially if the emulsion~olids weight ratio is high. Thus, some unpackaged emulsion blend product~ can be used in wet boreholes. Nevertheless, even those emulsion blend explosive~ which are storage-6table could be utilized in a more economic manner, i.e., in bulk form with for~ulations of high ~olids content, if their water resi6tance could be improved.
SUMMARy OF THE INVENTION
The present invention provides an improvement in an emulsion blend explosive which comprises a :~S~ 3~

sensitized blend of inorganic oxidizing salt particles and a water-in-uil emulsion compriing a carbonaceou~
fuel having components which form a continuous emulsion phase, an aqueous 601ution of an inorganic oxidizing 6alt forming a di6continuou emulsion phase disper~ed as discrete droplet6 within the continuous phase, and an emul ifying agent. More particularly, the improve~ent provided by this invention applies to a storage-stable blend of the type described above and compri6es, in ~aid blend, inorganic oxidizing 6alt particles containing at least about 15, and preferably at least about 20, percent by weight of a component comprised of particles which are 6maller than ~97 micrometers, i.e., pass a No. 50 sieve (U.S. ~eries), which has a 0.297 mm sieve opening, the weight ratio of the emulsion to the total inorganic oxidizing salt particles being in the range of about from 20/80 to 70/30.
The particulate oxidizing salt component which consists of particles smaller than 297 micrometer6 is referred to herein a6 "fines" or a "fines component". This fines component may constitute the entire particulate oxidizing 6alt portion of the emul~ion blend explosive, i.e., 100 percen~ by weight of the oxidizinq 6alt particles i~
composed of fines. ~owever, in an alternative, and in many in~tances preferred, embodiment, the fines component is present together with coarser particles, preferably with a coar6e component containing particles which are larger than 420 micrometer6, i.e., are retained on a No. 40 6ieve (U.S. 6eries), which has a 0.420 mm 6ieve opening. Preferably, the coar6e component contains AN or ANFO prill6.
One of the beneficial effect6 of a ~ines component in the particulate oxidizing 6alt portion of emulsion blend explosives is increa6ed water res;~ta~ce (i.e., the explo~ive~6 rezi~tance to attack by outside wa~er), thereby making the explo~ive ~uitable for u~e in unpackaged form in wet borehole~.
This increased water re~i6tance result6 with tho~e blend explo6ive~ which characteri6tically have a 6uficiently long shelf life as to be ~tGrable. e.g., products de~cribed in ~he afocementioned U.S. Patent 4 555 278. In these s~orable products, the solid oxidizing salt is less vulnerable to attack by internal or external water by virtue of a water-transport-re6i6tive medium or barrier which ~ay be the emulsion'~ continuous phase per ~e. Provided that the 6tability of a blend lS product is protected by this barrier or medium, fines may be &ubstituted for some or all of the 601id inorganic oxidizing salt in the blend with essentially no decrease in the blend's shelf life. In the normal situation, the higher-surface-area fines would be expected to ~ve greate~ ~tt~a~tion for the water in the emulsion~ 6 discontinuous phase, causing the blend to become destabilized. As will be discussed hereinafter, ~he finding that fines can be added to shelf-6table emul6ion blends without deleteriously affecting their ~helf life is important in several ~espects~ including the aforementioned increa6e in the blends' water resistance.
The term ~storage-6table emul6ion blend explosive", a6 used herein in reference to a product containing all-coar6e (i.e., larger than 420 micrometers) particulate inorganic oxidizing 6alt which i~ able ~o maintain its 6tability when 60me or all of the coarse particles are replaced by fine6, denotes a blend made from ~uch all-coarse particulate ~alt and a ~storage-6table emulsion". A "~torage-~'~S9~

6table emulsion", as the term is used herein. i6 onewhich, when blended at 3000-3500 poi~e viscosity with AN blasting prill5 in a 50/50 weight ratio, ~esults in a lead compeession of the blend o~ at least 3.8 centimeters on initiation with a 40-g initiator after blend 6torage for a period of 7 days, as determined by the lead compression test de~cribed herein. Any emulsion which gives this result in the desccibed 50/50 blend is "storage-stable~ and gives a blend lQ which is termed "storage-stable~ herein with any all-coarse particulate inorganic oxidizing salt in the 20/80 to 70/30 emulsion/salt range.
Another way of identifying a storage-stable emulsion and a storage-stable emulsion blend, in the sense that the terms are used herein, is to make a 50/50 blend of the emulsion at 3000-3500 poi~e viscosity with AN blasting prills and to subject the blend to the Salt Extraction Test described herein.
Thi~ test ~easuce~ the amount of inorganic oxidizing ~alt extracted fcom a blen~ by water. this amount being expressed as a percen~age of the total solid and dissolved salt in the blend. Although the percen~
salt extraction can be expected to increase as the emulsion content of emulsion blends decreases, the expression "storage-6table", in terms of a blend's behavior on fines inclusion, applies herein to blends containing less than 50 percent emulsion by weight (down to about 20 percent), as well as ~o those containing more (up to about 70 percent), and to blends made with any coarse particulate inor~anic oxidizing salt, provided that a ~alt extraction test performed on a 50/50 blend of the same emulsion and AN
prillfi result6 in a salt extraction not in excess of about 7 percent.

S~ 3~

D~TAILED DESCRIPTIOM
The e~ul6ion blend product of the invention i~ sen~itîzed, i.e., it contains ~ufficient ~ensitizer, e.g., di~per6ed ga~ bubble6 or ~oid6, a~
to render it detonable by mean~ cu~tomarily u~ed to initiate explo6ive~. ~his ~en6itization can be accompli~hed in any convenient manner. For example, the pre-blended emulsion ~an Per ~e be fully 6en6itized, i.e., it ~an be an explosive emul6ion, ~or example by incorpora~ing di~per~ed air therein, if de~ired in the form of air-carrying 601id ma~e~ials such a6 phenol-formaldehyde microballoon~, glass mic~oballoon~, fly ash, etc. Alternatively, chemical ~ensitiz2~s, e.g., amine nitrate~ 6uch as monomethylamine nitra~e, trinitrotoluene, perchlorates, etc., can be incorpocated in~o the emul~ion. Also, air-carlying solid material~ may be added to the emul6ion at the time of blending, and, in fact, porou~ inorganic nitrate prill~ may themselves serve as ~ir carriers ~p~ble by themselves of ~ensitizing the blend if present in 6ufficient amount, generally about 30 percent or more of the blend by weight. Fu~thermo~e, the fines themselve~ may act as a ~ensitizing cons~ituent o~ the blend, either in combination with one or more additional 6en~itizers, or even as essen~ially the 601e ~en~itizer (~ee Example~ 20-2Z ) .
Oil6 and aqueous inorganic oxidizing 6alt 601ution6 known to the explo6ive emul6ion art may be employed in the emul~ion portion of the blend product~, e.g.~ oil~ and 6alt 601utions di~clo~ed in U.S. Patent 4,2B7,010. Most often, the inorganic oxidixing salt present in the emulsion's aqueous phase will be an ammonium, alkali metal, or ~z~
alkaline-ear~h metal nitrate or perchlorate, prefecably ammonium nitrate, alone or in co~ination ~ith, for example, up to about 50 percent ~odium nitrate (ba~ed on ~he total weiyht of inorganic oxidizing ~alt6 in the ~queou6 pha~e). Salt~ having ~onovalent ca~ions are preferred if ~he ~mul~lfying agent used i~ a ~ombination of a fatty acid ~alt and a fatty acid, as is explained in the aforementioned U.S.
Patent 4,2B7,010. Suitable oil~ for use in ~he carbonaceous fuel include ~uel oil~ and lube oil~ of heavy a~omatic, naphthenic, or paraffinic ~tock, ~ineral oil, dewaxed oil, etc.
The oil content of the emul~ion may be sufficient to pcovide a ~ub~tantially oxygen-balanced emul~ion, or it may contain exce6~ oil (and be oxidizec-deficient), if it i~ to be blended with fuel-deficient or fuel-free solid particulate inorgani~ oxidizing ~alt. The benefits which may be derived from usinq ~uch a "high oil" emulsion are desccibed an the ~forementione~ U.S. Patent 4 555 278.

In addition to ~he possible inclufiion of chemical ~en~itizer~ (~ee above) in the emulsion, e.g., in solution in the discontinuou~ aqueous phase thereof or a~ a di6per6ion of a finely divided ~olid therein, one or more detonation catalystfi such a6 ammonium dichromate, cupric chloride, etc. al60 may be pre6ent, either in the emul6ion or in the particulate ~olid po~tion of the blend.
~arious type6 of emul~ifying agent~ are known for emulsaon6 to be u6ed as explo~ive6 or in emul6ion blend explo~ives. Whether or not a given emul6ifying agent i~ ~uitable for u6e in the emul6ion to be incorporated in the blend product of the invention 9~

depends cn ~he 6~0rage ~tability of the re~ulting blend6. This can be de~ermined by ~he previou61y ~entioned lead compre~iorl te~t performed on a~
all-coa~6e 50/50 blend (i.e., a blend of 50 percent emul~ion and 50 percent AN blasting prill6~. ~he previously mentioned Salt Extraction ~e~t al60 can be u6ed. A preferred emulsifying ~y6tem i6 the combination of a fatty acid 6alt and a fatty acid, which afford~ good ~torage 6tability, as i6 explained in the aforemen~ioned U.S. Patent 4 555 278.
With such a system, the free fatty acid i~ in ~olution in an oil, and the oil solution con6titute~ the continuous emul6ion phase. ~he ~atty acid and fatty acid 6alt, together with the oil, foEm the carbonaceous fuel.
In making the preferred emul6ions, the chosen fatty acid i~ added to the oil, and the fatty acid 6alt may be int~oduced in a preformed 6tate, or it can be produced in situ, e.g., as described in U.S. Patent 4,287,0100 from the f~tty ~cid ~n~ a base when the oil and an aqueous 6alt ~olution are combined to form the emulsion. The fatty acid preferably is a 6aturated or mono-, di- or tri-unsaturated monocarboxylic acid containing about from 12 to 22 carbon atoms, and the ~alt preferably i6 an alkali metal, ammonium, and/or alkylammonium 6alt of the fatty acid.
In the blend product of the invention, the emulsion i~ pre6ent in mixture with a partiçulate inorganic oxidizing 6alt in a ~eight ratio of about from 20/80 to 70~30 emulsion to particulate oxidizing 6alt; and at lea6t about 15, and preferably at lea6t about 20, percent by weight of the particulate oxidizing 6alt i6 compri6ed of particle~ which are 6maller than Z97 micrometer~, i.e., at lea6t about 15, and preferably at lea6t abou~ 20, percent "fine6".

~25~

~hile the emulsion can be blended with a particulate oxidizing ~alt that is composed substantially of all $ines, i.e., 80 as to produce a blend containing about f~om 30 to ~0 percen~ fines, ba&ed on total blend weight, it is often preferred ~o use fines in combination with coarser particle6, i.e., particles larger than 297 micrometers. Most preferably, a coarse component is present in which Eome of the particles therein, generally at least about 15 percent by weight of the particulate inorganic oxidizing salt, are larger than 420 micrometers, e.g., are hN or ANFO
~ills.
In blends of from about 20/80 up to 40/60 percent emulsion to oxidizing salt particles, by weight, it is preerred that the particulate salt contain about from 20 to 70 percent fines by weight (giving a fines content of about f~om 12 to 56 percent, based on total blend weight). Optimum results, considered mainly in terms of improved water resistance, are obtained when the particulate salt in these blends contains about from 30 to 60 percent fines by weight (giving a fines content of about fro~
18 to 48 percent, based on total blend weight).
A major benefit of ~he fines/coarse combina~ion in blends containing larger amounts of emulsion, i.e., ~0 percent or more by weight, results from the better distribution of the solid particles in the blend, and in such blends a fines/coarse weight ratio larger than about 34/66 will be selected more on the basis of other desieed propertie6, e.g., sensitivity to initiation, detonation velocity, etc, although ~ome additional improvement in water resistance al60 i8 achieved.
That the addition of solid fines to certain emulsion blends does not cause blend destabilization owing to the higher ~urface area of the f ine~, and actually can bring about an increase in ~he water resistance of ~uch blend~, i6 an unexpected di~covery. The following di6cus~ion i~ pre6ented to provide a more ~pecific understanding of the ~enefit~
achievable by fines addition, a~ re~ated, ~or example, to the emulsion con~ent of the blend. The discu~sion should be understood a~ no~ intended to limit the present invention on the basis of any ~heoretical considerations found therein.
The particulate inorganic oxidizing salt in emul6ion blend explosives, e.g., those described in the afoeementioned U~S. Patent 4 555 278, usually consists of porous AN prills. It has been found that when fines are substituted for &ome of these prills in the previou~ly de~cribed ~torage-stable emulsion blend explosives, a si~nificant improvement in the blend~' water resi~tance begins to become apparent when the fines content of the particulate ~alt portion of the ~lend attains a level of about 15 percent, provided that the emulsion content of the blend is about 20 percent. At this emulsion level and up to a level somewhere in the 30-40 percent range, the blends appear to behave as if they are "emul~ion-deficient~', i.e., as if they contain insufficient emul6ion to cover the particulate inorganic oxidizing salt. In thi~ case, an "all-fines" particulate solid is more de6i~able than one in which no fines are present, but the improvement in wate~ resi6tance, in the cafie of emul6ion-deLi~ient blends, goe~ through an optimum in the fines range of about from 30 to 60 percent (based on the weight of total particulate solid), and other properties 6uch as blend density and flowability follow the 6ame trend.

~5~

~ hen large~ ~mount~ of emulsion are p~e~ent ;n ~he blen~, e.g., ~0 percent Ul more. the blends appear to behave a~ if they are "emulsion-6ufficient", i.e., as if they contain ~ufficient emul6ion to cover ~he particulate inorgani~ oxidizing 6alt. In thi~
ca~e, the water ~e~i~tance continue~ to inclease with increa~ing fine~ content, but the increase ~oderate~
~igr.ificantly when ~he fines/coar6e percen~ weight ratio exceeds about 3~/6~. Blend density appear6 to level off al~o. However, a fines content of about rom 34 to 100 percent, ba~ed on particulate ~olid weight, in ~he emui~ion-~ufficient blend~ may be ~ery useful in affording a product ~hich has not only improved water re~istance but also a hlgher degree of 6ensitivity. The .~ddition of large amount~ of fines in these product~ permi~s the attainment o~ increased sensi~ivity and detonation velocity without the concomitant undesirable decrea~e in density which occur~ with the u~e of the common phy~;cal sensitizers ~uch as microballoons.
The inorganic oxidizing salt which forms the pacticulate ~olid portion of the blend product of the invention can be ammonium nitrate (AN~, ammonium perchlorate, an alkali metal nitrate, e.g., ~odium nitrate ~SN), an alkali metal perchlocate, an alkaline-earth metal nitrate, e.g., calcium nitrate (CN), o~ an alkaline-earth metal perchlorate, or any combination of ~wo or more 6uch nitrate~, in the form of granule6 or prills, or prill~ lightly coated with fuel oil, e.g., the well-known "ANF0", in which the usual AN/~0 ratio i8 about 94/6, and/or coated a~cording to the method de~cribed in the aforementioned IJ,S. Patent 4 555 278. For a course component, AN prills and ANF0 are preferred. The AN prills can be the blasting ~s~
1~
prill~ commonly used in explosives, or agricultural or fertilizer prills. Blasting prills are usually less dense and more porous than fertilizer prills. When only fertilizer prills are used, blends containing at least about 25 per~ent emulsion and higher fines levels, e.g., at least about 25 percent, based on total solid particulate weight, may be required to achieve a desired sensitivity.
The fines component can be ground-up ~N
prills, or an inorganic perchlorate, such as ammonium or an alkali metal pecchlorate, or a combination of AN
and a perchlorate. Regardless of the particular ~al~(~) used, sufficient fuel, preferably oil, should be mixed therewith, or incolporated into the lS emulsion, as described previously, to produce an es6entially oxygen-balanced blend. The use of less porous fines such as SN fines may be advantageous in terms of affording a more easily pumpable blend because greater fluidity results owing to (a) less absorption of the oil required for oxygen-balancing purposes (relative to the amount of oil absorbed by pOlOUS AN f ines), and (b) the larger amount of oil needed to oxygen-balance an SN-containing blend.
The fines useful in this invention can be eroduced in any one of a variety of 6tandard grinding mills. For example, it may be advantageous to utilize existing hammermill facilities found in ~NF0 plants and used ordinarily to gcind ammonium nitrate pcill6 to ANF0-HD dimensions. In grinding the prill6, precautions ~hould be taken to avoid contamination for ceasons of both 6afety and performance. When ammonium ni~rate prills are gcound, sufficient precautions 6hould be taken to minimize exposure to water in any form because water is known to lead to prill degradation. The degree of grinding will depend on ~s~

the intended final use, i.e., the level of fines desired in the f inal product~ This ~eans, of course, that the particulate inorganic oxidizing fialt can be ground directly on a hammermill so that about 15% o~
it has dimension6 smallèr than Z~7 micrometers.
Alternatively, the prills can be ground so that essentially all is smaller than 297 micrometers. ~s previously stated, either can be used directly in a blend or in the latter case the essentially all-fines material can be mixed with ammonium nitrate prills to give the desired fines concentration level in a mixtuce of coarse and fines particles. The specifics of the ~rinding conditions are known to those skilled in the art.
The fines Per se and their mixtures with coarser particles can easily be characterized by standald sieving techniques and a partlcle size distribution determined.
The emulsion blend explosives described in the following examples were prep~red as follows:

a. The Emulsion Emulsions of the following formulations were made by the method described in Example 1 of U.S.
Patent 4,287,010, except that the glass microballoons and the fly ash were omitted:
Emulsion (a) Emulsion !b) %
Ammonium ~itrate (dissolved) 70.9 75.8 Water 15.6 16.6 Oil 7.6 4.3 Oleic Acid 3.B 2.1 Sodium Hydroxide (50% aq.soln.) 2.1 1.2 ~9~
1~
The pe~centages given ~or oleic acid and the ~odium hydroxide solution ~epce6en~ ~he proportions u6ed to ~ake an oleate salt emulsi~ier in ~itu.

b. The Emul6ion Blend Blend6 of emul6ion~ (a) and (b) with ~olid par~iculate AN were made by two method~.
~ccording to one method (re~erred to herein as ~'lab method~), the emul~ion was added to the bowl of a Hobart*~odel C-10~ mixer ~9.6-liter capacity), chosen amount6 of crushed and, where needed, whole AN prill~
were added, and the emulsion and 601id~ were mixed for 4 minute~ at about 60 rpm. ~hen oil needed to be added to oxygen-balance the blend, the oil wa6 added befo~e the AN, and the emul~ion and oil were mixed for two minute6. In the second ~ethod, i.e., the cement-mixer ~ethod, the prill6 (cru~hed and, where required~ vhole) were added to a 45-kg capacity cement ~ixer, set at it~ lowest possible angle. After the addi~ion of the emul~ion, the solid~ and emulsion were mixed at the lowest ~peed ~etting for good tumbling action. Oil, if needed, was added to, and mixed with, the AN before the emulsion was added.

c. Particulate AN
Four different finesJcoar6e combinations were u~ed. ~N Product I was ob~ained by grinding AN
bla~ting pcill~, and AN Products II-IV were blends of cru~hed and whole AN prill6 (obtained from two different ~uppliec6) typical of tho6e attained in ANFO-HD production, no oil having been added ~o the6e product6 per 8 The ~cceen analy6e~ of the four products wece a6 follow6:

* denotes trade mark s~

AN Product I II III IV

% Held on 50*(>297~) = coar6e 14.0 85.5 66.262.5 Through/held 50/100*
(<297~.~149~) 27.9 7.6 3~.S19.5 ~
Through~held 100/140* 3 (<149~,>105~) 14.4 2.4 0.657~351 ~ Through/held 140/200~ l (<105~,>74~) 3.5 0.2 0.05 5.8 ~fines % Through/held 200/325*
(c74~,>44~) 27.6 3.2 ~ 3.7 Through 325*
(<44~) 12.6 1.1 1.05 1.15 * U.S. Sieve Designations ExamPles 1-12 Blends were prepared by the lab method described above, uing the Product I ground AN p~ills, alone or together with whole AN blasting prill~
(larger than 420 micrometers) in varying proportions.
The blends were evaluated for water resistance and 6helf life. Water resistance ~as estimated by the following 6alt extraction test:
One hundred grams of water and then 100 g o~
the blend were weighed into a 237-milliliter, wide-mouth glass jal (10.8 cm high x 5.1 cm in diameter). The ~ealed jar was placed for 15 minutes on a ball mill having a roller 6peed of Z60 rpm.
Fifty milliliters of the agueous layer was then weighed. The inc~ease in the weight of the water i~
due to the amount of ammonium nitrate (particulate and in the emul~ion's aqueous phase) that has been extracted from the blend, larger amount6 denoting ~ ~59'~

poorer blend water resistance. In this test, the difference in the weiyht of S0 milliliters of water before and after the described rotation is the weight of one-half of the ~otal amoun~ o~ ~al~ extracted because only one-half to the water used was weighed.
The percent salt extracted was calculated a6 follows:

% salt extracted =
wt. 50 ml H 0 after extraction - wt. 50 ml H 0 Z _ _ _ 2 x 100 0.5 total wt. of salt in 100 g blend (The total weight of ~alt in 100 grams of the blend is ~he weight of the ammonium nitrate in the emulsion's dispersed agueous phase plus the wsight of the particulate AN in the blend.) The Salt Extraction Test was designed to pro~ide a meaningful estimate of an emulsion blend~s resistance to deterioration by water unde~ conditions commonly encountered in field prac~ice. In the field, blends may be pumped or augured into water-containing holes. In some in~tances, running as well as stagnant water may be encountered in the wet holes. The test, with its rolling action on the water and the emulsion blend, simulates the flowing conditions which may be encountered in boreholes during loading.
Shelf life was evaluated on the basis of the blend's lead block compression afte~ ~everal days' ctocage. The explosive produc~ was placed in a cylindrical 0.95-liter paper cup (16.5 cm high x 8.73 cm internal diameter), and packed to itfi maximum bulk den6ity by tapping the cup on a 6upporting surface.
The cup was then placed on a l.9-cm-thick x 10.8-cm square steel plate, which in turn wa~ positioned on a lead cylinder 10.2 cm high x 6.2 cm in diameter. The lead cylinder wa6 then placed on a ~teel plate similar ~l~5.9~

to the one above it. The product was initiated fcom the cup's open top, the size of the initiator used varying with the sensitivity of the blend. The ~esulting reduction in the height of the lead cylinder was measured.
The ~esults are shown in Table I.

lo ~S9~

~ ~ U~
v a) ~ ~
t ~ E-~ _ X X X K K
a~ I¢ aJ ~D ~ a) K ~
~! ~ V ~ W ~ ~4 O ~ U 5 tn tJ' ~ 3: C7'~ t7` t~
r1 .rl O N O ON N O O C) a~ c ~ ~ C!~ O O ~ ~ ~ c~ o o ~ t~ c~ ,¢ o o ~ a 3c 3 ~ 2 ~ 3 ~ 3 3 ~
~ l ~o - N N CO Ln u~:1 o, ~ u~ u~ u'~ ~ ~ ~ ~ cr, U C _ N t` ~1 0 ~ ~I t` N ~ / N tr~ N N
e-,~ ~, ~ ~ ~ u o o ~ o o ~ o O ~ _ c ~
~o ,I n5 tP N O O t-~ 0 0~ I O ~1 ~o ~ ~ ~ ~ ~I N
N N
~ ~ U~ U~ X

--~ ~, ~¦ ' ~o o o o o N N
E-l ~ o o o o ~ ~ ~1 ~ N N N

O # ~D ~ O N ~ U'\
.,1 U~ . . . ~ ' ' ' ~ Z ~) dO 0:~ U`l ~ O O O ~ ~ O O O ~ ~ ~ ~) O O CC~
.rl I¢ ~:: N ~r N tt~ N ~ r u N
1:~, .
e ~ ~ N O
t.) Ll # ... . ... . - . - . . -~ # ~0 ~1 ~ r` O t` ~D O er Q~ ` `D N ~ ~ ~ ~ ~ r 'a O Z ~ N ~ ~ NL~') N ~ N ~ ~D
~: C,) ~1 _l I #
_I ~
O ~P C~ O C~ O O O O O O O O O O O O O O O
~n ~ 0 ~0 O u X Z ~ $

e o ,, N ~'IP ul ~ I` o~ o~
~C Z

~5~3 ~

C
al ~ ~ .,~ ~ _ u c ~ U~ ~~ . ~ ~ .,, ~
S ~ ~ i~ r r t~ u ~3 ~n ~ Z C ~ b . ~ O
/11 ~ 111 ~ N--I N rl ~ V
~ ~ E~-- K ~ ~ r~
X KX ~ C s: u 4~u C ~8 V 0-~1Z ~ Ll ~-r~ ~ Ll r ~ I ~ ~ ~ t~ 3 C~.~1 lt 51~ c O V ~ t~ U _~ U ~
_~ .r~ O N O N N~O 0 O ~ ~ .a m ~ . o ~ o ~ c, o ~ ~r~ ~ O ~ ,: ~ r z ~r 3 ~ rl ~ E ~ 3 u 3 t~ Z E~ ~) 3 r~
~ I ~ ~ C ~ 3 ~ u c tt) u-,~ C
1~ ~ ~ ) O N ~1 O`~ '1) U~ O_( m ~ t:l --( oP e 4 C ^ ~n N N O .0 0 0 N~ 3 ~ ~ Ci a~ ~ O u~ O
O m ~- ~ ~ :~ ~ ~ u t~~ CO E O --4 a1 to o ~ ~ ~ c ~
,_ I ~a ~ c ~ u ~:
C C N u~ ~0 1~a~ ~ ~ O O ~ rl 1 .r-1-~ 5 ~ O O ~ O ~ C~ X, Ctl ~ Ll o~ ~ ~ a~ v C~ V~ .. ,...... .. ~ ~ C~
1~5 .rl t~ U _I r~l N Nr~l N ~ Z ~ ` Ul E E~ ~1 ~ o z~ ~ o. u Ca~ X u . ~a5 N f~
~ ~ ., :c ~e ~ o 4 ~ 0~
C ~ O~rl C
~Q O O O O u Ll~ O O O ~ 3 ...... .. o ~ . C ~ ~ u ~' O ~ X O
u c ~1 C a) c -~ 4 I C ~ ~ O ~ E~
O ~ ~ N 1~ ~ ~N U V C ~
.,~ ~D ... . . ,~ 0 ~ J O ~ c Z ~ tP N t` ~1 0 0 0 ~ O I ~ 4 '~t e /11 C :~ e ~
.,~ ~ C ~1 ~ ~ r~ ~ C w ~-,~ ~ C ~ _ _~
~ ~ ~ 3 :~3 tr :~ u ~, o ~ u~ ~ m o mC . c~
c a~ ~ u ~ u a~
a~ ,, L~ O ~C C~ a c ~ J~ U
o ~ ~ O ~ C~, ~, ec ~, c., ~, u ~ ., . .. .. ~ o-,~ a -~P o~ ~r o N O O
o Z .,~ e ~u ~ c ,1e E X
C U ~: ~--I ~ ,C tn ~) ~ O U ~-~
~ O ~ ~ C c~ 1 4-~
_~ I ~ 1 bl U ~ c ~o a, ~
::1 0 o~ u~ ~ C C~ V E a) e~ N N N N N ~ ~ o ~ ~-~ ~ N a~ U
1~ ~ ~ c c~ c w 1~
. c a o ~ 0m ~ ~
C o Cl O o O ~ C O O I U~
o 4 K Z ~ ~ ~ ~ Z ~ O ~ N 4 ~ ~.o u ~ u~ U `D ~ I ~
_I C ,1 o C -I ~ ~ CO 11 ~ 11 ~¢ o C 4 ~ d O C~ N C S::
~1 ~ O a~ _l u U
C- ~ L tD O 0 C4 ~D C~ I S
E~ O O ~/ N
X Z ~1 ,I ,-1 ~ ~ 11 ~ ~1 ~-~s~

2~
Table I 6hows that emul~ion blend~ with all-coar~e AN containing 25-50 percent emulsion and which a~e ~torage-~table a~ defined herein (blends made in Control Expts. A, D, G, and 3) have their water resi~tance i~proved by the addition of AM ~ines to the blend6 with no deleteriou6 effect on shelf life (Examples 1, 2, and 3 vs. Control Expt. A; Examples 4, 5, and 6 vs. Control Expt. D; Examples 7, 8, and 9 vs.
Control Expt. G; and Example6 10~ 11, and 12 v6.
Control Expt. J). This table al60 show6 that blend~
which contain 15 percent emul6ion, and those which are not storage-6table, a~ 3udged from the lead compression te~t, do no~ show any significan$
improvement in water resistance, and generally are wor~ened, by the addition of fines thereto ~Control Expt6. B v5. C, E v6. F, H YS. I, K v~. L, and M vs.
N).
ExamPl-es 13 and 14 50~50 Blends of Emul6ion (a) with 601id particulate AN were made by the cement mixer method, packaged in polyetbylene chub cartridge6, and tested periodically for shelf life by attempting to detonate ~hem unconfined. The solid particulate AN con6is~ed of AN product I and whole AN blasting prill6 in amount~ to provide a coarse AN (larger than 297~) content in the blend of 32.~ percent, and a fines content in the blend of 17.2 percent ~65.6 percent coarse AN and 34.4 percent fines, based on the particulate component). ~he cartridge6 were initiated unconfined by mean~ of a 0.45-kg cast primer known as an HDP-l*primer.

3s * denotes trade mark -Example Control Coar6e AN hge~V~D Age/V0~
No. Expt. No. AN ~ Fine~ % daYs/m/~ec m~nth~/m/~ec 13* 32.B 17.2 5/3463 1.75/32Z8 o* ~o 0 5/3000 1.5/2959 14** 32. a 17.2 5/35S2 2.5/341g 5p** 50 0 5/3300 2.~/301g * 6.8-kg cartridge lG.16 cm in diameter ~* 13.6-kg cartridge 12.7 cm in diameter Examples 15-18 50/50 Blends of Emulsion (a) and ~N product6 I, II, III, and IV were made by the lab method. No whole AN p~ills were added. The products had the following properties:
Min. InitiatorA~ to Salt P~oduce Lead Block Example AN Fines* Extracted Compression 23.8 No. _ Product ~ % cm after_7 days 15 I 85 0.1 1/2 UA
16 II 14.5 0.9 ~A
17 III 33.8 2.1 1/2 UA
18 IV 37.5 1.0 1/2 UA
* Based on total weight of particulate AN
** See Table I
The above result6 indicate the effectiveness of AN fine6 in improving the water re6i6tance of emul6ion blend~ over a wide range of fines content (compare with Control ~xpt. A in Table I). The re6ult~ also 6how that, with es~entially the same fines content (Examples 17 and 18), better water resi6tanee may be achie~ed with a solid ammonium nit ate product having a more 6cattered di6tribution of particle ~ize6 (Product IV vs. Product III).
Example 19 A 50/50 emul~ion blend wa6 prepared by the cement mixer method, u6ing Emulsion (a), AN Product I, and whole AN bla6ting prill~. Emulsion (a) was ~ e devoid of a 6en6itizing amount of di6per6ed ga6 ~9~

bubbles or voids, and con~ained ~ufficient oil to oxygen balance the AN dissolved therein as well as the solid AN in the blend. Based on the total weight of the blend, the coar6e AN content was 32.~ percent, and the AN fines content 17.2 peecent.
When packaged in polyethylene chub cartridges and initiated uncon~ined by means of a 0.45-kg cast primer, the blend detonated at velocities of 3713, 3432, and 2B22 m~sec in diameter6 of 12.7, 10.2, and 7.6 cm, respectively.
In contrast, a blend made in the same manner fcom the same emulsion, but containing no ~ines, gave detonation velocities of 3810, 3350, and 2108 m/6ec in diameters of 12.7, 10.2, and 7.6 cm, respectively, only when 5.7 pe~cent by weight of fly ash was included in the formulation. Thu~ in a given blend, the use of an inorganic oxidizing salt in the form of fine~ may avoid the need for relatively expensiYe physical sensitizers in the product.
ExamPles 20-22 A ~erie6 of experiment6 wa6 performed with 50/50 emul6ion/~M blends containing AN fines according to the pre~ent invention to 6how ~hat AN agricultural prills can be 6ubstitu~ed for bla~ting prills therein. Emulsion (b~ wa6 blended (lab method) wi~h an ~N product made by grinding AN agricultural prill5 to a 6ize distribution 6imilar to that of AN Produc~
I. ~here necessary, the ground product was used together with whole AN agricultural prills, which had a particle density of 1.59 g/cc. The following table 6hows the results o~ lead compression test~ performed on the 7-day-old blend~.

~s~

Control Lead Compression Test Example Expt. Coar6e AN AN Fine6 Comp~es6ion No. No. ~ ~ (cm) Initiator Zo 7.0 43.0 5.56 40-g Flex*~
Q 50 0* 0 0 40-g Flex 21 24.2*~ 25.8 4.60 60-g Flex 22 32.8** 17.2 4.14 80-g Flex * All ageicultural prill6 ~ Prill6 plus coarse portion of ground product *~* See Table I
ExamPle ?~3 A 50/50 blend was made in the cement mixer from emul6ion (a) and the solid AN component used in Example 22. The blend wa6 eackaged in a 12.7 cm diameter polyethylene chub cartridge weighing 13.6 kg, and it6 detonation velocity ~easured in a steel pipe after 7 and 29 day6. An HDP-l initiator was u6ed.
The packaged blend detonated at 3504 and 419~ m/sec after 7 and 29 days, re~pectively. The ~ame blend containing only whole agricultural prill6 ~no fines) detonated at 2102 and 3~9~ m/6ec after 7 and 29 days, respectively.

Claims (27)

24

1. In a storage-stable emulsion blend explosive comprising a sensitized blend of inorganic oxidizing salt particles and a water-in-oil emulsion comprising a carbonaceous fuel having components which form a continuous emulsion phase, an aqueous solution of an inorganic oxidizing salt forming a discontinuous phase dispersed as discrete droplets within said continuous phase, and an emulsifying agent, the improvement comprising inorganic oxidizing salt particles containing at least about 15 percent by weight of a fines component comprised of inorganic oxidizing salt particles which are smaller than 297 micrometers, the weight ratio of said emulsion to the total inorganic oxidizing salt particles being in the range of about from 20/80 to 70/30.

2. An explosive of Claim 1 wherein said fines component is comprised of at least one member selected from the group consisting of nitrates and perchlorates.

3. An explosive of Claim 1 wherein said emulsion contains, in its emulsifying system, a salt of a fatty acid, as well as the free fatty acid in solution in an oil, said oil solution forming said continuous emulsion phase, and said fatty acid, said fatty acid salt, and said oil together forming said carbonaceous fuel.

4. An explosive of Claim 1 wherein said fines component constitutes substantially the entire amount of inorganic oxidizing salt particles therein.

5. An explosive of Claim 4 wherein the percent emulsion in said blend is at least 40.

6. An explosive of Claim 5 wherein said fines component is comprised of at least one member selected from the group consisting of nitrates and perchlorates.

7. An explosive of Claim 1 wherein said inorganic oxidizing salt particles contain a coarse component comprised of particles which are larger than 297 micrometers.

8. An explosive of Claim 7 wherein said fines component is comprised of at least one member selected from the group consisting of nitrates and perchlorates.

9. An explosive of Claim 8 wherein said fines component contains sodium nitrate.

10. An explosive of Claim 8 wherein said coarse and fines components comprise a combination of whole and crushed ammonium nitrate prills, ammonium nitrate-fuel oil prills, or a combination of ammonium nitrate and ammonium nitrate-fuel oil prills.

11. An explosive of Claim 10 wherein the percent emulsion in said blend ranges from about 20 up to 40, and the fines content of the whole and crushed prills is about from 30 to 60 percent.

12. An explosive of Claim 10 wherein the percent emulsion in said blend is at least 40, and the fines content of the whole and crushed prills is at least about 34 percent.

13. An explosive of Claim 7 wherein said coarse component contains particles which are larger than 420 micrometers.

14. An explosive of Claim 13 wherein said particles larger than 420 micrometers constitute at least about 15 percent of said inorganic oxidizing salt particles by weight.

15. An explosive of Claim 14 wherein said coarse component contains whole ammonium nitrate prills, ammonium nitrate-fuel oil prills, or a combination thereof.

16. An explosive of Claim 7 wherein the percent emulsion in said blend ranges from about 20 up to 40 percent.

17. An explosive of Claim 16 wherein the inorganic oxidizing salt particles contain about from 20 to 70 percent of said fines component.

18. An explosive of Claim 7 wherein the percent emulsion in said blend is at least 40.

19. An explosive of Claim 18 wherein the inorganic oxidizing salt particles contain at least 20 percent of said fines component.

20. An explosive of Claim 10 wherein said blend is formed from an emulsion that contains a sensitizing amount of dispersed gas bubbles or voids.

21. An explosive of Claim 10 wherein said blend is formed from an emulsion that is devoid of a sensitizing amount of dispersed gas bubbles or voids, and said blend is sensitized by air carried into it by prills.

22. An explosive of Claim 10 wherein said blend is formed from an emulsion that is devoid of a sensitizing amount of dispersed gas bubbles or voids, and said blend is sensitized by said fines component.

23. An explosive of Claim 1 wherein said blend is formed from an emulsion that contains oil in an amount sufficient to oxygen-balance all of said particulate inorganic oxidizing salt.

24. An explosive of Claim 1 wherein said blend is formed from (a) an emulsion that contains oil in an amount sufficient to oxygen-balance the inorganic oxidizing salt in said discontinuous emulsion phase and (b) added oil as required to oxygen-balance all, or a portion, of said particulate inorganic oxidizing salt.

25. An explosive of Claim 24 wherein said blend is formed from said emulsion and a mixture of whole and crushed AN prills that has been treated with oil.

26. A method of making an emulsion blend explosive of improved water resistance from a storage-stable emulsion blend of about from 30 to 80 percent by weight of inorganic oxidizing salt particles larger than 420 micrometers and about from 70 to 20 percent by weight of a water-in-oil emulsion comprising a carbonaceous fuel having components which form a continuous emulsion phase, an aqueous solution of an inorganic oxidizing salt forming a discontinuous emulsion phase dispersed as discrete droplets within the continu-ous phase, and an emulsifying agent, said method compris-ing replacing at least about 15 percent by weight of said particles by inorganic oxidizing salt particles which are smaller than 297 micrometers, said storage-stable emulsion blend from which said explosive of improved water resistance is made being one which, when formed with AN blasting prills to a 3000-3500 poise viscosity in a 50/50 weight ratio, gives a lead compression of at least 3.8 centimeters when initiated with a 40-g initiator after storage for a period of 10 days.

27. A method of Claim 26 wherein said emulsion contains, in its emulsifying system, a salt of a fatty acid, as well as the fatty acid in solution in an oil.