Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
  • C06B45/18—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B47/00—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase
  • C06B47/14—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase comprising a solid component and an aqueous phase
  • C06B47/145—Water in oil emulsion type explosives in which a carbonaceous fuel forms the continuous phase
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B47/00—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase

Definitions

• the present invention relates to explosive compositions comprising a sensitized blend of a water-in-oil emulsion and solid particulate inorganic oxidizing salt, preferably ammonium nitrate (AN).
• a sensitized blend of a water-in-oil emulsion and solid particulate inorganic oxidizing salt preferably ammonium nitrate (AN).
• Explosives which comprise a blend of a water-in-oil emulsion and solid particulate AN, e.g., ANFO (AN prills coated with fuel oil), are becoming increasingly popular with blasters owing to the fact that they are able to offer the advantages of high bulk density and blasting energy characteristic of emulsion explosives, while at the same time resulting in cost reductions owing to the lower cost of the AN.
• ANFO AN prills coated with fuel oil
• Short shelf life means that an explosive product lacks stability, undergoing deleterious change(s) in structure and/or composition to the degree that it cannot be depended upon to detonate at the required velocity at the required time. If the product's shelf life is very short, it almost certainly is unsuitable for use in packaged form, and can be unsuitable for use in bulk form, especially if it needs to be transported to the place of use or allowed to stand in a borehole for some time after loading.
• ANFO One of the materials which is commonly employed as the particulate solid component of emulsion blend explosives is ANFO. While ANFO is a popular blasting product in its own right because of economy and convenience, its lack of water resistance and low product density are well-recognized as product deficiencies. The blending of ANFO with a water-in-oil emulsion results in a product of higher density, and a certain degree of water resistance may be achieved in the blend product, especially if the emulsion/solids weight ratio is high. Thus, some unpackaged emulsion blend products can be used in wet boreholes. Nevertheless, even those emulsion blend explosives which are storage-stable could be utilized in a more economic manner, i.e., in bulk form with formulations of high solids content, if their water resistance could be improved.
• the present invention provides an improvement in an emulsion blend explosive which comprises 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 emulsion phase dispersed as discrete droplets within the continuous phase, and an emulsifying agent.
• the improvement provided by this invention applies to a storage-stable blend of the type described above and comprises, in said blend, inorganic oxidizing salt particles containing at least about 15, and preferably at least about 20, percent by weight of a component comprised of particles which are smaller than 297 micrometers, i.e., pass a No. 50 sieve (U.S. series), 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.
• U.S. series No. 50 sieve
• the particulate oxidizing salt component which consists of particles smaller than 297 micrometers is referred to herein as "fines” or a “fines component".
• This fines component may constitute the entire particular oxidizing salt portion of the emulsion blend explosive, i.e., 100 percent by weight of the oxidizing salt particles is composed of fines.
• the fines component is present together with coarser particles, preferably with a coarse component containing particles which are larger than 420 micrometers, i.e., are retained on a No. 40 sieve (U.S. series), which has a 0.420 mm sieve opening.
• the coarse component contains AN or ANFO prills.
• One of the beneficial effects of a fines component in the particulate oxidizing salt portion of emulsion blend explosives is increased water resistance (i.e., the explosive's resistance to attack by outside water), thereby making the explosive suitable for use in unpackaged form in wet boreholes.
• This increased water resistance results with those blend explosives which characteristically have a sufficiently long shelf life as to be storable, e.g., products described in the aforementioned co-pending U.S. Patent Application Serial No. 696,200.
• the solid oxidizing salt is less vulnerable to attack by internal or external water by virtue of a water-transport-resistive medium or barrier which may be the emulsion's continuous phase per se .
• fines may be substituted for some or all of the solid inorganic oxidizing salt in the blend with essentially no decrease in the blend's shelf life.
• the higher-surface-area fines would be expected to have greater attraction for the water in the emulsion's discontinuous phase, causing the blend to become destabilized.
• the finding that fines can be added to shelf-stable emulsion blends without deleteriously affecting their shelf life is important in several respects, including the aforementioned increase in the blends' water resistance.
• storage-stable emulsion blend explosive as used herein in reference to a product containing all-coarse (i.e., larger than 420 micrometers) particulate inorganic oxidizing salt which is able to maintain its stability when some or all of the coarse particles are replaced by fines, denotes a blend made from such all-coarse particulate salt and a “storage-stable emulsion”.
• a “storage-­ stable emulsion”, as the term is used herein, is one which, when blended at 3000-3500 poise viscosity with AN blasting prills in a 50/50 weight ratio, results in a lead compression of the blend of at least 3.8 centimeters on initiation with a 40-g initiator after blend storage for a period of 7 days, as determined by the lead compression test described herein.
• Any emulsion which gives this result in the described 50/50 blend is "storage-stable” and gives a blend 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 is to make a 50/50 blend of the emulsion at 3000-3500 poise viscosity with AN blasting prills and to subject the blend to the Salt Extraction Test described herein. This test measures the amount of inorganic oxidizing salt extracted from a blend by water, this amount being expressed as a percentage of the total solid and dissolved salt in the blend.
• the percent salt extraction can be expected to increase as the emulsion content of emulsion blends decreases
• the expression "storage-stable" 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 to those containing more (up to about 70 percent), and to blends made with any coarse particulate inorganic oxidizing salt, provided that a salt extraction test performed on a 50/50 blend of the same emulsion and AN prills results in a salt extraction not in excess of about 7 percent.
• the emulsion blend product of the invention is sensitized, i.e., it contains sufficient sensitizer, e.g., dispersed gas bubbles or voids, as to render it detonable by means customarily used to initiate explosives.
• This sensitization can be accomplished in any convenient manner.
• the pre-blended emulsion can per se be fully sensitized, i.e., it can be an explosive emulsion, for example by incorporating dispersed air therein, if desired in the form of air-carrying solid materials such as phenol-formaldehyde microballoons, glass microballoons, fly ash, etc.
• chemical sensitizers e.g., amine nitrates such as monomethylamine nitrate, trinitrotoluene, perchlorates, etc.
• air-carrying solid materials may be added to the emulsion at the time of blending, and, in fact, porous inorganic nitrite prills may themselves serve as air carriers capable by themselves of sensitizing the blend if present in sufficient amount, generally about 30 percent or more of the blend by weight.
• the fines themselves may act as a sensitizing constituent of the blend, either in combination with one or more additional sensitizers, or even as essentially the sole sensitizer (see Examples 20-22).
• Oils and aqueous inorganic oxidizing salt solutions known to the explosive emulsion art may be employed in the emulsion portion of the blend products, e.g., oils and salt solutions disclosed in U.S. Patent 4,287,010, the disclosure of which patent is incorporated herein by reference.
• the inorganic oxidizing salt present in the emulsion's aqueous phase will be an ammonium, alkali metal, or alkaline-earth metal nitrate or perchlorate, preferably ammonium nitrate, alone or in combination with, for example, up to about 50 percent sodium nitrate (based on the total weight of inorganic oxidizing salts in the aqueous phase).
• emulsifying agent used is a cmbination of a fatty acid salt and a fatty acid, as is explained in the aforementioned U.S. Patent 4,287,010.
• Suitable oils for use in the carbonaceous fuel include fuel oils and lube oils of heavy aromatic naphthenic, or paraffinic stock, mineral oil, dewaxed oil, etc.
• the oil content of the emulsion may be sufficient to provide a substantially oxygen-balanced emulsion, or it may contain excess oil (and be oxidizer-deficient), if it is to be blended with fuel-deficient or fuel-free solid particulate inorganic oxidizing salt.
• the benefits which may be derived from using such a "high oil" emulsion are described in the aforementioned U.S. Patent Application Serial No. 696,200, the disclosure of which is incorporated herein by reference.
• one or more detonation catalysts such as ammonium dichromate, cupric chloride, etc. also may be present, either in the emulsion or in the particulate solid portion of the blend.
• emulsifying agents are known for emulsions to be used as explosives or in emulsion blend explosives. Whether or not a given emulsifying agent is suitable for use in the emulsion to be incorporated in the blend product of the invention depends on the storage stability of the resulting blends. This can be determined by the previously mentioned lead compression test performed on an all-coarse 50/50 blend (i.e., a blend of 50 percent emulsion and 50 percent AN blasting prills). The previously mentioned Salt Extraction Test also can be used.
• a preferred emulsifying system is the combination of a fatty acid salt and a fatty acid, which affords good storage stability, as is explained in the aforementioned U.S.
• Patent Application Serial No. 696,200 With such a system, the free fatty acid is in solution in an oil, and the oil solution constitutes the continuous emulsion phase.
• the chosen fatty acid is added to the oil, and the fatty acid salt may be introduced in a preformed state, or it can be produced in situ . e.g., as described in U.S. Patent 4,287,010, from the fatty acid and a base when the oil and an aqueous salt solution are combined to form the emulsion.
• the fatty acid preferably is a saturated or mono-, di- or tri-unsaturated monocarboxylic acid containing about from 12 to 22 carbon atoms
• the salt preferably is an alkali metal, ammonium, and/or alkylammonium salt of the fatty acid.
• the emulsion is present in mixture with a particulate inorganic oxidizing salt in a weight ratio of about from 20/80 to 70/30 emulsion to particulate oxidizing salt; and at least about 15, and preferably at least about 20, percent by weight of the particulate oxidizing salt is comprised of particles which are smaller than 297 micrometers, i.e., at least about 15, and preferably at least about 20, percent "fines".
• the emulsion can be blended with a particulate oxidizing salt that is composed substantially of all fines, i.e., so as to produce a blend containing about from 30 to 80 percent fines, based on total blend weight, it is often preferred to use fines in combination with coarser particles, i.e., particles larger than 297 micrometers. Most preferably, a coarse component is present in which some 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 AN or ANFO prills.
• the particulate salt In blends of from about 20/80 up to 40/60 percent emulsion to oxidizing salt particles, by weight, it is preferred that the particulate salt contain about from 20 to 70 percent fines by weight (giving a fines content of about from 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 from 18 to 48 percent, based on total blend weight).
• a major benefit of the fines/coarse combination in blends containing larger amounts of emulsion, i.e., 40 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 desired properties, e.g., sensitivity of initiation, detonation velocity, etc, although some additional improvement in water resistance also is achieved.
• the particulate inorganic oxidizing salt in emulsion blend explosives usually consists of porous AN prills. It has been found that when fines are substituted for some of these prills in the previously described storage-­stable emulsion blend explosives, a significant improvement in the blends' water resistance begins to become apparent when the fines content of the particulate salt portion of the blend attains a level of about 15 percent, provided that the emulsion content of the blend is about 20 percent.
• the blends appear to behave as if they are "emulsion-deficient", i.e., as if they contain insufficient emulsion to cover the particulate inorganic oxidizing salt.
• an "all-fines" particulate solid is more desirable than one in which no fines are present, but the improvement in water resistance, in the case of emulsion-deficient blends, goes 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 such as blend density and flowability follow the same trend.
• the blends When larger amounts of emulsion are present in the blends, e.g., 40 percent or more, the blends appear to behave as if they are "emulsion-sufficient", i.e., as if they contain sufficient emulsion to cover the particulate inorganic oxidizing salt. In this case, the water resistance continues to increase with increasing fines content, but the increase moderates significantly when the fines/coarse percent weight ratio exceeds about 34/66. Blend density appears to level off also. However, a fines content of about from 34 to 100 percent, based on particulate solid weight, in the emulsion-sufficient blends may be very useful in affording a product which has not only improved water resistance but also a higher degree of sensitivity. The addition of large amounts of fines in these products permits the attainment of increased sensitivity and detonation velocity without the concomitant undesirable decrease in density which occurs with the use of the common physical sensitizers such as microballoons.
• the inorganic oxidizing salt which forms the particulate solid portion of the blend product of the invention can be ammmonium nitrate (AN), ammonium perchlorate, an alkali metal nitrate, e.g., sodium nitrate (SN), an alkali metal perchlorate, an alkaline-earth metal nitrate, e.g., calcium nitrate (CN), or an alkaline-earth metal perchlorate, or any combination of two or more such nitrates, in the form of granules or prills, or prills lightly coated with fuel oil, e.g., the well-known "ANFO", in which the usual AN/FO ratio is about 94/6, and/or coated according to the method described in the aforementioned U.S.
• ANFO ammmonium nitrate
• ANFO ammonium perchlorate
• an alkali metal nitrate e.g., sodium nitrate (
• AN prills and ANFO are preferred.
• the AN prills can be the blasting prills commonly used in explosives, or agricultural or fertilizer prills. Blasting prills are usually less dense and more porous than fertilizer prills.
• blends containing at least about 25 percent 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 AN prills, or an inorganic perchlorate, such as ammonium or an alkali metal perchlorate, or a combination of AN and a perchlorate. Regardless of the particular salts(s) used, sufficient fuel, preferably oil, should be mixed therewith, or incorporated into the emulsion, as described previously, to produce an essentially oxygen-balanced blend.
• porous fines such as SN fines
• 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 porous AN fines), and (b) the larger amount of oil needed to oxygen-balance an SN-containing blend.
• the fines useful in this invention can be produced in any one of a variety of standard grinding mills. For example, it may be advantageous to utilize existing hammermill facilities found in ANFO plants and used ordinarily to grind ammonium nitrate prills to ANFO-HD dimensions. In grinding the prills, precautions should be taken to avoid contamination for reasons of both safety and performance. When ammonium nitrate prills are ground, sufficient precautions should 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 the intended final use, i.e., the level of fines desired in the final product.
• the particulate inorganic oxidizing salt can be ground directly on a hammermill so that about 15% of it has dimensions smaller than 297 micrometers.
• the prills can be ground so that essentially all is smaller than 297 micrometers.
• the essentially all-fines material can be mixed with ammonium nitrate prills to give the desired fines concentration level in a mixture of coarse and fines particles.
• the specifics of the grinding conditions are known to those skilled in the art.
• the fines per se and their mixtures with coarser particles can easily be characterized by standard sieving techniques and a particle size distribution determined.
• 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:
• the percentages given for oleic acid and the sodium hydroxide solution represent the proportions used to make an oleate salt emulsifier in situ .
• Blends of emulsions (a) and (b) with solid particulate AN were made by two methods.
• the emulsion was added to the bowl of a Hobart Model C-100 mixer (9.6-liter capacity), chosen amounts of crushed and, where needed, whole AN prills were added, and the emulsion and solids were mixed for 4 minutes at about 60 rpm.
• the oil was added before the AN, and the emulsion and oil were mixed for two minutes.
• the prills crushed and, where required, whole
• the solids and emulsion were mixed at the lowest speed setting for good tumbling action. Oil, if needed, was added to, and mixed with, the AN before the emulsion was added.
• AN Product I was obtained by grinding AN blasting prills
• AN Products II-IV were blends of crushed and whole AN prills (obtained from two different suppliers) typical of those attained in ANFO-HD production, no oil having been added to these products per se .
• the screen analyses of the four products were as follows:
• Blends were prepared by the lab method described above, using the Product I ground AN prills, alone or together with whole AN blasting prills (larger than 420 micrometers) in varying proportions. The blends were evaluated for water resistance and shelf life. Water resistance was estimated by the following salt extraction test:
• the difference in the weight of 50 milliliters of water before and after the described rotation is the weight of one-half of the total amount of salt extracted because only one-half to the water used was weighed.
• the percent salt extracted was calculated as follows: The total weight of salt in 100 grams of the blend is the weight of the ammonium nitrate in the emulsion's dispersed aqueous phase plus the weight of the particulate AN in the blend.
• the Salt Extraction Test was designed to provide a meaningful estimate of an emulsion blend's resistance to deterioration by water under conditions commonly encountered in field practice.
• blends may be pumped or augured into water-containing holes. In some instances, 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.
• the explosive product was placed in a cylindrical 0.95-liter paper cup (16.5 cm high ⁇ 8.73 cm internal diameter), and packed to its maximum bulk density by tapping the cup on a supporting surface. The cup was then placed on a 1.9-cm-thick ⁇ 10.8-cm square steel plate, which in turn was positioned on a lead cylinder 10.2 cm high ⁇ 6.2 cm in diameter. The lead cylinder was then placed on a steel plate similar to the one above it. The product was initiated from the cup's open top, the size of the initiator used varying with the sensitivity of the blend. The resulting reduction in the height of the lead cylinder was measured.
• Table I shows that emulsion blends with all-coarse AN containing 25-50 percent emulsion and which are storage-stable as defined herein (blends made in Control Expts. A, D, G, and J) have their water resistance improved by the addition of AN fines to the blends with no deleterious 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 Examples 10, 11, and 12 vs. Control Expt. J).
• Blends of Emulsion (a) with solid particulate AN were made by the cement mixer method, packaged in polyethylene chub cartridges, and tested periodically for shelf life by attempting to detonate them unconfined.
• the solid particulate AN consisted of AN product I and whole AN blasting prills in amounts to provide a coarse AN (larger than 297 ⁇ ) content in the blend of 32.8 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).
• the cartridges were initiated unconfined by means of a 0.45-kg cast primer known as an HDP-1 primer.
• Blends of Emulsion (a) and AN products I, II, III, and IV were made by the lab method. No whole AN prills were added. The products had the following properties:
• a 50/50 emulsion blend was prepared by the cement mixer method, using Emulsion (a), AN Product I, and whole AN blasting prills.
• Emulsion (a) was per se devoid of a sensitizing amount of dispersed gas bubbles or voids, and contained sufficient 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 coarse AN content was 32.8 percent, and the AN fines content 17.2 percent.
• Emulsion (b) was blended (lab method) with an AN product made by grinding AN agricultural prills to a size distribution similar to that of AN Product I. Where 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 shows the results of lead compression tests performed on the 7-day-old blends.
• a 50/50 blend was made in the cement mixer from emulsion (a) and the solid AN component used in Example 22.
• the blend was packaged in a 12.7 cm diameter polyethylene chub cartridge weighing 13.6 kg, and its detonation velocity measured in a steel pipe after 7 and 29 days.
• An HDP-1 initiator was used.
• the packaged blend detonated at 3504 and 4198 m/sec after 7 and 29 days, respectively.

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Citations (4)

• 1986
  • 1986-10-14 NO NO864090A patent/NO168886C/no unknown
  • 1986-10-14 IE IE862703A patent/IE862703L/xx unknown
  • 1986-10-14 CA CA000520449A patent/CA1259492A/en not_active Expired
  • 1986-10-14 MY MYPI86000018A patent/MY100181A/en unknown
  • 1986-10-14 EP EP86307930A patent/EP0221701A1/en not_active Ceased
  • 1986-10-14 ZW ZW208/86A patent/ZW20886A1/xx unknown
  • 1986-10-14 IN IN744/CAL/86A patent/IN166325B/en unknown
  • 1986-10-15 ZA ZA867821A patent/ZA867821B/xx unknown
  • 1986-10-15 OA OA58979A patent/OA08755A/xx unknown
  • 1986-10-15 AU AU63943/86A patent/AU581154B2/en not_active Expired
  • 1986-10-15 CS CS867450A patent/CS269987B2/cs unknown
  • 1986-10-15 MA MA21025A patent/MA20795A1/fr unknown
  • 1986-10-15 JP JP61243305A patent/JPS62171983A/ja active Pending
  • 1986-10-15 BR BR8605044A patent/BR8605044A/pt unknown
  • 1986-10-15 MX MX4040A patent/MX164721B/es unknown
  • 1986-10-15 NZ NZ217947A patent/NZ217947A/xx unknown
  • 1986-10-15 KR KR1019860008656A patent/KR890003676B1/ko not_active IP Right Cessation
  • 1986-10-15 PT PT83550A patent/PT83550B/pt unknown
  • 1986-11-04 ZM ZM96/86A patent/ZM9686A1/xx unknown

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