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EP0131355B1 - Stable ammonium nitrate-emulsion explosives and emulsion for use therein - Google Patents

Stable ammonium nitrate-emulsion explosives and emulsion for use therein Download PDF

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Publication number
EP0131355B1
EP0131355B1 EP84303208A EP84303208A EP0131355B1 EP 0131355 B1 EP0131355 B1 EP 0131355B1 EP 84303208 A EP84303208 A EP 84303208A EP 84303208 A EP84303208 A EP 84303208A EP 0131355 B1 EP0131355 B1 EP 0131355B1
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EP
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Prior art keywords
emulsion
fatty acid
oil
salt
blend
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German (de)
English (en)
French (fr)
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EP0131355A2 (en
EP0131355A3 (en
Inventor
Lawrence Anthony Cescon
Nolan Joseph Millet, Jr.
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ETI Explosives Technologies International Inc
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ETI Explosives Technologies International Inc
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    • 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
    • C06B31/00—Compositions containing an inorganic nitrogen-oxygen salt

Definitions

  • the present invention relates to explosive compositions comprising a sensitized blend of a water-in-oil emulsion and solid particulate ammonium nitrate (AN), e.g., AN prills or granules which may be coated with fuel oil (ANFO), and more particularly to such compositions in the form of storage-stable packaged products and bulk products adapted to be pumped into boreholes.
  • AN water-in-oil emulsion and solid particulate ammonium nitrate
  • ANFO fuel oil
  • the invention also relates to a low-viscosity emulsion particularly adapted to be blended with fuel-free or -deficient AN to form such a blend.
  • Explosives which comprise a blend of a water-in-oil emulsion and solid particulate AN have captured the interest of blasters in recent years owing to the fact that they are able to offer the advantages of high bulk density, blasting energy, and water resistance characteristic of emulsion explosives, while at the same time resulting in cost reductions owing to the lower cost of the AN.
  • ANFO solid particulate AN
  • problems that may be encountered in connection with the use of these blends are those of blend pumpability and blend stability, more particularly of the stability of the blend's explosive properties.
  • Some blends are not pumpable, or only difficultly pumpable. Some must be pumped immediately after they have been formed because they do not retain their pumpability even for a day or two.
  • Emulsion/AN blends are described in U.S. Patents 3,161,551 (Egly et al.); 4,111,727 (Clay); 4,181,546 (Clay); and 4,357,184 (Binet et al.), and British Patent 1,306,546 (Butterworth).
  • Egly et al. describe an emulsion/AN blend wherein the emulsion, said to be in a sensitized form, is employed as a sensitizer for the solid ammonium nitrate.
  • the patentees describe forming the blend in the borehole itself, i.e., by dropping the AN into the hole and pouring the sensitized emulsion over it.
  • Clay whose 10/90 to 40/60 emulsion/AN blends in U.S. Patent 4,111,727 are sensitized only by the air entrapped in the AN, states that the emulsion and AN particles are combined by very simple procedures, preferably just prior to insertion into the borehole. Clay also states that sorbitan monooleate, sorbitan monostearate, and sorbitan monopalmitate are quite suitable emulsifiers for making his emulsion, and that the emulsifiers preferably are blended into the oil before the aqueous component is added.
  • Clay's AN may be oxygen-balanced ANFO (to be blended with an oxygen-balanced emulsion), or fuel-deficient or fuel-free solid AN (to be blended with an emulsion that contains most or all of the oil required to oxygen-balance the blend).
  • Clay describes 40/60 to 60/40 emulsion/AN blends having completely filled interstices in and between the AN particles. This product is said to contain too high a proportion of dry ingredient to be pumpable in conventional slurry pumps, but is said to de deliverable to a borehole by an auger in the same manner as dry ANFO. This patent advises minimizing the amount of emulsifier, and using high shear mixing, to insure a stable emulsion. Clay describes sorbitan fatty acid esters as being particularly suitable emulsifiers, and "Glycomul O" (sorbitan monooleate) as superior to most for his invention.
  • the emulsion portion of Binet et al.'s explosive composition is termed a "microemulsion", and it contains an amphiphatic synthetic polymer emulsifier, along with a conventional water-in-oil emulsifier.
  • a phosphatide emulsion stabilizer is included.
  • Binet et al.'s microemulsion per se described as a "liqui-liquid foam" of very small cell size ranging from less than 1 micron to about 15 microns, is said to display exceptional long-term storage stability and to be tolerant to doping with further fuel and energy-enhancing ingredients.
  • Binet et al.'s consideration of storage stability is directed for the most part at the explosive emulsion itself.
  • the patentees mention that all known prior art water-in-oil emulsions suffer from lack of stability owing to the seeding effect.
  • Binet et al. also imply that the seeding effect is a problem in AN-doped emulsions, although they do not explain how this can be so in microemulsions containing relatively large AN particles.
  • Binet et al. require an expensive polymeric emulsifier, and an optional emulsion stabilizer, to achieve improved stability in their microemulsion.
  • AN/emulsion blends having good storage stability, and a method of making such blends which does not require the use of expensive additives, of perhaps limited utility, are greatly needed to expand the spectrum of AN/emulsion products that can be made available to the public.
  • blends are needed which are pumpable into a borehole even a few days after having been formed, as well as detonable after having been delivered into a borehole in packaged form after a period of about three months or more from the time the blends were made.
  • the present invention provides an improvement in a method of preparing an explosive composition by combining ammonium nitrate (AN) particles, e.g., AN or ANFO prills, with a water-in-oil emulsion comprising (a) a liquid carbonaceous fuel having components which form a continuous emulsion phase, (b) an aqueous solution of an inorganic oxidizing salt forming a discontinuous emulsion phase dispersed as discrete droplets within the continuous phase, and (c) an emulsifying agent to form a blend of the AN particles and the emulsion containing a sensitizing amount of dispersed gas bubbles or voids.
  • AN ammonium nitrate
  • the improvement of the invention comprises forming the AN particles and the components of the emulsion into a structure that minimizes the loss of water from the aqueous solution droplets and the transportation of the water across the continuous phase to the AN particles mixed with the emulsion.
  • this structure includes an emulsion which, when subjected to the following Water Diffusion Test, loses an amount of water that is no more than 4 percent of the original emulsion weight:
  • a cylindrical pan of 7.5 mm radius and 2.6 mm height is filled with 0.325 cc of freshly prepared emulsion, which is the same emulsion as that which has been used to prepare the blend.
  • the emulsion's flat exposed surface of 1.25 cm 2 area is contacted with a cylindrical pellet of ammonium nitrate having the same cross-sectional area as the emulsion sample and a height of at least 1 cm.
  • the ammonium nitrate is the same as that which has been used to prepare the blend.
  • the emulsion/AN sample is stored for 48 hours in dry air at 25°C, after which time the emulsion is analyzed for water loss.
  • the described structure that hinders water loss and transport is formed by combining the AN particles with an emulsion which contains, in its emulsifying system, (a) a salt, prefrably an alkali metal, ammonium, and/or alkylammonium salt, of a fatty acid (preferably selected from the group consisting of saturated and mono-, di-, and tri-unsaturated monocarboxylic acids containing about from 12 to 22 carbon atoms), as well as (b) the free fatty acid, the latter being in solution in an oil, the oil solution constituting the continuous emulsion phase, and the fatty acid and fatty acid salt, together with said oil, forming said liquid carbonaceous fuel.
  • a salt prefrably an alkali metal, ammonium, and/or alkylammonium salt, of a fatty acid (preferably selected from the group consisting of saturated and mono-, di-, and tri-unsaturated monocarboxylic acids containing about from 12 to 22 carbon atoms)
  • the fatty acid salt emulsifying system is one which has been produced in situ from a fatty acid and a base when the oil and the aqueous solution of the inorganic oxidizing salt have been combined to form the emulsion.
  • a base e.g., hydroxide, is present in the emulsion's aqueous phase.
  • An alternative, or preferably supplemental way of forming the structure that controls water transport between the aqueous solution droplets and the AN particles is to provide a droplet cell size of at least about 1, and preferably no greater than about 4, microns. Still alternatively, or additionally, the structure will be formed by coating the AN particles with a substance in which water has a diffusion coefficient at 25°C of less than about 10- 5 cm 2 /sec.
  • a storage-stable packaged product made by one embodiment of the method of the invention and comprising an aged blend of preferably at least about 30 percent by weight of particles of AN, e.g., ANFO prills, and preferably at least about 30 percent by weight of an emulsion comprising (a) a liquid carbonaceous fuel including an oil solution of a fatty acid, said solution forming a continuous emulsion phase, (b) an aqueous solution of an inorganic oxidizing salt forming a discontinuous emulsion phase dispersed as discrete droplets within the continuous phase, and (c) an emulsifying system including an emulsifying agent comprising a salt, preferably an alkali metal, ammonium, or alkylammonium salt, of a fatty acid (preferably selected from the group consisting of saturated and mono-, di-, and tri-unsaturated monocarboxylic acids containing about from 12 to 22 carbon atoms), as well as the free fatty
  • aged is used herein to distinguish the packaged product of the invention from products which are made at the site of use and delivered into a borehole in bulk form.
  • An “aged” product denotes herein a product which is packaged and transported to the field site at some later date, usually at least several days, and often weeks, after the time of manufacture.
  • ammonium nitrate particles as used herein to describe the solid material that is present in the product of the invention in a blend with an emulsion denotes ammonium nitrate in the form of granules or prills, e.g., fuel-free or fuel-deficient prills, or prills lightly coated with fuel oil, i.e., the well-known "ANFO", in which the usual AN/FO weight ratio is about 94/6, and/or coated according to the method of the invention, as will be described hereinafter.
  • the present invention provides a water-in-oil emulsion adapted to be blended with AN prills by one embodiment of the method of the invention to form a stable explosive, said emulsion comprising
  • a base is also present, as a result of the addition of base and fatty acid in an equivalents ratio of about from 0.5/1 to 3/1, preferably about from 1.5/1 to 2/1.
  • the fatty acid weight should be understood to be the weight of fatty acid added to form the emulsion. Some of this becomes converted to the fatty acid salt emulsifier.
  • This emulsion has a viscosity generally in the range of about from 500 to 10,000 poise, and about from 500 to 3,000 poise for bulk products. The emulsion structure is stable for a period of about 3 months or more.
  • the "fatty acid" weight in the above-specified oil to fatty acid ratio should be understood to be the weight of fatty acid added plus the weight of fatty acid salt added when the emulsion is being made.
  • the ratio of the weight of fatty acid salt (added) to the weight of fatty acid (added) is at least about 0.5/1.
  • the amount of inorganic oxidizing salt (the oxidizer) present in the emulsion of the invention is insufficient for the complete combustion of the fuel therein, as is evidenced by the emulsion's negative oxygen balance.
  • This oxidizer-deficient emulsion is converted into a product having a more positive oxygen balance and satisfactory explosive properties by blending with fuel-deficient or, preferably, substantially fuel-free AN prills.
  • the oxidizer-deficient emulsion can be blended with these AN prills with low shear so as to produce a preferred explosive emulsion/AN blend of the invention containing about from 20 to 70 percent by weight of AN prills and a sensitizing amount of dispersed gas bubbles or voids (e.g., an amount which is at least about 5 percent based on blend volume), the blend being essentially oxygen-balanced, i.e., having an oxygen balance more positive than about -25 percent, and preferably in the range of about from -10 to +5 percent.
  • Blends made from the preferred in situ emulsion and about from 20 to 50 percent prills have a viscosity in the range of about from 2500 to 20,000 poise, a viscosity in this range being maintainable for a period of several days.
  • the present invention is based on the discovery that the transport of water from the dispersed aqueous phase of the emulsion to the AN particles that are intermixed with the emulsion in AN/emulsion blends plays a major role in the instability of these blends, leading to a deterioration of product performance.
  • This transfer of water results in an increase in the water content of the particulate AN, perhaps to a level of about 5 to 10 percent, and an increase in the salt concentration in the dispersed aqueous phase, approaching the saturation limit and the possibility that the salt may crystallize out.
  • the AN particles and the components of the emulsion by virtue of their chemical composition and physical properties (e.g., size and spatial relationships), are formed into a structure in the emulsion/AN blend that minimizes the loss of water from the droplets of aqueous salt solution, and transportation of the water across the emulsion's continuous phase to the AN particles.
  • This structure provides a medium or barrier resistive to water-transport formed preferably by a substantially hydrophobic continuous emulsion phase, most preferably obtained when the emulsifying system contains a salt, preferably an alkali metal, ammonium, and/or alkylammonium salt, of a fatty acid (e.g., a saturated or mono-, di-, or tri-unsaturated monocarboxylic acid containing about from 12 to 22 carbon atoms), as well as the free fatty acid in solution in an oil, the oil solution of the acid forming the emulsion's continuous phase, and the oil, fatty acid, and fatty acid salt together forming the liquid carbonaceous fuel.
  • a salt preferably an alkali metal, ammonium, and/or alkylammonium salt
  • this emulsifying system is formed in situ by combining the oil and the aqueous solution in the presence of a fatty acid and a base, according to the method described in U.S. Patent 4,287,010 (Owen). It has been suggested that the Owen in situ method may allow the fatty acid salt (soap) emulsifying agent to form at the oil/water interface, where it is present together with free fatty acid, whereby a stabilizing equilibrium is believed to be established between the acid/soap at the interface, fatty acid in the oil phase, and base in the aqueous phase.
  • the fatty acid salt (soap) emulsifying agent may form at the oil/water interface, where it is present together with free fatty acid, whereby a stabilizing equilibrium is believed to be established between the acid/soap at the interface, fatty acid in the oil phase, and base in the aqueous phase.
  • the emulsifying system is one which has been produced by the in situ formation of a salt, preferably an alkali metal, ammonium, or alkylammonium salt, of a fatty acid (preferably a saturated or mono-, di-, or tri-unsaturated monocarboxylic acid containing about from 12 to 22 carbon atoms), most preferably sodium, potassium, and/or ammonium oleate, according to techniques described in the aforementioned Owen patent.
  • a salt preferably an alkali metal, ammonium, or alkylammonium salt
  • a fatty acid preferably a saturated or mono-, di-, or tri-unsaturated monocarboxylic acid containing about from 12 to 22 carbon atoms
  • sodium, potassium, and/or ammonium oleate most preferably sodium, potassium, and/or ammonium oleate
  • the above-described control of the emulsifying system is the preferred way of providing a structure wherein a hydrophobic medium is present between the aqueous droplets in the emulsion and the AN particles.
  • An alternative method, useful with any emulsifying system but preferably in conjunction with the preferred emulsifying system described above, is to coat the AN particles with a substance in which water diffusivity is low, e.g., in which water has a diffusion coefficient at 25°C of less than about 10- 5 , and preferably less than about 10- 8 , cm 2 /sec.
  • Preferred coating materials are those which, when used in an amount constituting 6-10 percent of the amount of solid AN used, can act as a fuel to oxygen-balance the solid AN. Such materials could replace the fuel oil (FO) normally used in ANFO for example. Examples of such materials are solid or semi-solid hydrocarbons including paraffin wax and petrolatum-rosin-paraffin.
  • the required structure formed by the AN particles and the components of the emulsion is provided by controlling the cell size of the emulsion's internal phase (the aqueous salt solution droplets) so as to decrease the chemical driving force, i.e., the difference between the chemical potential of the water in the dispersed aqueous salt solution of the emulsion and the AN particles.
  • a reduced chemical driving force minimizes the rate of water transport from the aqueous emulsion phase to the AN particles.
  • the chemical potential of the components in the dispersed aqueous phase increases in inverse proportion to the radius of curvature of the cell (droplet).
  • a preferred product of the invention is a "high oil" emulsion that contains a portion, and preferably substantially all, of the oil required to oxygen-balance the solid ammonium nitrate to be blended therewith. This is beneficial for several reasons. First, the added oil imparts a lower viscosity to the emulsion.
  • Low viscosity is of great benefit in that it permits the formation of emulsion/AN blends with lower shear mixing, which has an advantageous effect on the stability of the blend.
  • Lower shear mixing is especially important in making blends having a high content of solid AN or ANFO because the movement of the particles past each other during mixing performs work on the emulsion between them which may break the oil film that separates the particles from the aqueous solution droplets, thereby giving water transport a "head start".
  • the "high oil" emulsion of the invention and particularly the preferred emulsion in which the emulsifying system is formed in situ a more stable blend results because the components can be mixed with less shear than that used in blending a more viscous emulsion, and a less viscous, more easily pumpable blend results.
  • the lower viscosity of the blend is sufficiently stable, at least for several days, so that the advantage of ease of pumping is retained even if a few days elapse between the time when the blend is made and the time when it is pumped.
  • a "high oil” emulsion having an emulsion structure that is stable i.e., a structure in which there is no "creaming" of the oil phase
  • concentration of the emulsifying agent is higher than that used in standard "low oil” emulsions, i.e., essentially oxygen-balanced emulsions which are to be blended with ANFO.
  • the emulsifying agent is a salt of a fatty acid used in conjunction with the free fatty acid, which is in solution in the oil, and especially if the salt of a fatty acid has been formed in situ as described in U.S.
  • the stable, low-viscosity emulsion i.e., the "high oil” emulsion which contains proportionately more emulsifying agent
  • AN having a stable viscosity which remains low enough to facilitate pumping even if the blend "ages" a day or so before pumping.
  • Non-ionic emulsifying agents such as those of the sorbitan fatty acid ester type, have been stated in the prior art, i.e., in U.S. Patent 4,181,546 (Clay), as having been found to be among the most satisfactory emulsifiers for emulsions, with respect to stability.
  • a new finding, however, is that emulsion/AN blends made from "high oil" emulsions containing an emulsifying agent in a concentration that is sufficiently high to preserve the emulsion structure are unstable with respect to viscosity levels when the emulsifying agent is sorbitan monooleate.
  • viscosity stability is not a characteristic of "high oil” emulsion/AN blends in general, but is dependent upon the nature of the emulsifying system present in the "high oil” emulsion.
  • blends of the "high oil" emulsion of the invention and oil-free or oil-deficient AN prills are that the void volume in the AN prills could be useful as sensitizing sites in the blend.
  • inclusion of all of the required oil in the emulsion to begin with permits the oil to fatty acid ratio to remain essentially undisturbed in the transition from the unblended to the blended emulsion, hence preserving the required emulsifier level.
  • the amount of liquid carbonaceous fuel (oil plus fatty acid plus fatty acid salt) present in this emulsion generally will be in the range of about from 7 to 21 percent, based on the total emulsion weight.
  • the amount of liquid carbonaceous fuel in this emulsion is higher as the AN prill content of the blend in which it is to be used is higher.
  • the emulsion's liquid fuel content ranges about from 9 to 15 percent by weight, and is no more than about 13 percent in emulsions to be used in bulk products, in which it is beneficial to use no more than about 50 percent prills to facilitate pumping.
  • inorganic oxidizing salt(s) and water present in the aqueous phase of the "high oil" emulsion are within the broad ranges specified for these components in U.S. Patent 4,287,010, i.e., about from 50 to 95 percent oxidizing salt(s) and about from 5 to 25 percent water, by weight. However, within these ranges, higher water concentrations, i.e., about from 12 to 20 percent, are preferred in this emulsion.
  • the content of inorganic oxidizing salt(s), liquid carbonaceous fuel, and water of "low oil” emulsions used in the present method and in the packaged product of the invention will be as described in U.S. Patent 4,287,010.
  • a fatty acid e.g., oleic acid
  • a base is brought together at the same time as an aqueous solution of an inorganic oxidizing salt and an oil, whereby a fatty acid salt emulsifying agent forms in situ as a water-in-oil .emulsion forms.
  • a fatty acid salt e.g., oleic acid
  • Base is also present, in the aqueous phase.
  • the fatty acid salt emulsifying agent used in the preferred embodiment of the present method may be a salt of a saturated or mono-, di-, or tri-unsaturated monocarboxylic acid containing at least about 12, and usually no more than about 22, carbon atoms.
  • examples of such acids are oleic, linoleic, linolenic, stearic, isostearic, palmitic, myristic, lauric, and brassidic acids.
  • the free fatty acid present may be selected from this same class of monocarboxylic acids. Oleic and stearic acids are preferred on the basis of availability.
  • a fatty acid e.g., oleic acid
  • oleic acid which is liquid at the temperature at which the blend is expected to be used should be selected.
  • this will be an unsaturated monocarboxylic acid.
  • the cation portion of the fatty acid salt preferably is an alkali metal (e.g., sodium, potassium, or lithium), ammonium, or mono-, di-, or trialkylammonium ion in which the alkyl group(s) preferably contain 1-3 carbon atoms.
  • alkali metal e.g., sodium, potassium, or lithium
  • ammonium or mono-, di-, or trialkylammonium ion in which the alkyl group(s) preferably contain 1-3 carbon atoms.
  • Sodium, potassium, and ammonium oleates are preferred.
  • the emulsion structure of the "high oil” emulsion of the invention is many times more stable than a comparable emulsion containing a lower emulsifier concentration.
  • the weight ratio of oil to fatty acid added to form the emulsion should be in the range of about from 1/1 to 3/1.
  • the weight of "fatty acid” in this ratio should be understood to be the weight of fatty acid added plus the weight of fatty acid salt added, and the ratio of fatty acid salt (added) to fatty acid (added), by weight, should be at least about 0.5/1.
  • the base/acid equivalents ratio used to form the "high oil” emulsion by the in situ method should be in the range of about from 0.5/1 to 3/1, preferably about from 1.5/1 to 2/1.
  • oils and aqueous inorganic oxidizing salt solutions known to the explosive emulsion art may be employed, preferably those disclosed in the aforementioned U.S. Patent 4,287,010.
  • 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 50 percent sodium nitrate (based on the total weight of inorganic oxidizing salts in the aqueous phase).
  • Salts having monovalent cations are preferred, as explained in U.S. Patent 4,287,010.
  • Suitable oils for use in the liquid carbonaceous fuel include fuel oils and lube oils of heavy aromatic, naphthenic, or paraffinic stock, mineral oil, dewaxed oil, etc.
  • the "high oil" emulsion of the invention is formed by agitating the aqueous oxidizing salt solution and the oil solution of the fatty acid in the presence of the fatty acid salt under conditions which result in a stable emulsion of a selected viscosity.
  • the base preferably is dissolved in the aqueous solution, which is agitated with the oil solution of the fatty acid.
  • This emulsion may be blended with AN prills (or granules) by pumping it into a mixer or into an auger conveying the AN.
  • AN prills
  • the latter mode is convenient for making a packaged product.
  • the turning of the screw in the auger blends the emulsion and prills as well as transfers the blend into the package.
  • the low viscosity of the emulsion allows the mixing to be done in a shorter auger length with less shear, resulting in improved shelf life over blends made with high shear.
  • the blend of "high oil" emulsion and AN prills is to be used in bulk form, e.g., by pumping it from a mixer and into a borehole, perhaps after standing in the mixer for a day or so, the blend remains in a form suitable for pumping after such time owing to its viscosity stability, as is shown in Example 7.
  • the viscosity of a freshly made blend of an emulsion made by the in situ method and containing about from 20 to 50 percent AN prills generally is in the range of about from 2500 to 20,000 poise, and the blend maintains a viscosity in this range for a period of several days, sufficient to enable pumping to be undertaken during such time.
  • the AN with which the "high oil" emulsion is blended is an oil-deficient product, preferably substantially oil-free AN prills.
  • an oil-deficient product preferably substantially oil-free AN prills.
  • sufficient prills are used to produce a blend having a prill content of about from 20 to 50 percent by weight. Up to 70 percent prills may be used for a packaged product.
  • the emulsion/prill blend of the invention is in a sensitized form so that it is detonable by means customarily used to initiate explosives. For this reason the blend contains a sensitizing amount, e.g., at least about 5 percent by volume, of dispersed gas bubbles or voids (based on blend volume).
  • This void or gas volume can be that of the AN prills perse (see Example 5), or gas can be incorporated by adding other air-carrying solid materials, for example, phenol-formaldehyde microballoons, glass microballoons, fly ash, etc.
  • materials of the latter type are to be present in the blend, they may constitute a component of the emulsion or they may be added at the time of blending. Generally, with blends containing less than about 50 percent AN prills, provision should be made for the express addition of gas bubbles or voids into the emulsion for the sensitization thereof.
  • the fatty acid salt emulsifying system is the preferred means of providing the structure that minimizes water loss and transport in the method of the invention. This means is used to best advantage when the fatty acid salt emulsifying system is used in conjunction with high oil content, cell size control, and/or AN coating, etc. However, in the present method the latter techniques can be used with other emulsifying systems.
  • the present method is used to advantage in the preparation of blends which contain about from 20 to 70 percent AN particles by weight.
  • the need for a water transport barrier and/or decreased chemical driving force generally is not great with blends containing less than about 20 percent AN.
  • the AN content usually will be in the range of about from 30 to 70 percent by weight for a packaged blend, and about from 20 to 50 percent by weight for a pumped blend.
  • Explosives which are blends of a water-in-oil emulsion and AN or ANFO prills having a physical and chemical structure that minimizes water loss and transport from the emulsion's aqueous phase according to the method of the invention, and especially blends of the "high oil” emulsion of the invention and AN prills, are useful in bulk as well as packaged form.
  • the emulsion/AN blend of the invention made with the low-viscosity "high oil” emulsion, and particularly the preferred "in situ" emulsion, is especially suited for pumping operations.
  • a preferred technique for pumping the blend into a borehole is to pump it through an annular stream of aqueous lubricating liquid, e.g., naturally occurring water, flowing through the conduit used to transfer the blend to the hole.
  • aqueous lubricating liquid e.g., naturally occurring water
  • Such a technique is described in European Patent Application No. 83 302 563.8 by D. L. Coursen, for pumping a Bingham solid, e.g., a water-in-oil emulsion explosive.
  • the resistance of the emulsion/AN blend to movement through a conduit is reduced by provision of an annular layer of liquid of low viscosity, e.g., water, around a central column of the blend in the conduit.
  • An annulus of aqueous lubricating liquid, injected into the conduit through which the emulsion/AN blend is to be delivered to the borehole, provides lubrication sufficient to permit a column of the blend to slide through the conduit without undergoing appreciable deformation in shear, i.e., movement in "plug flow", a distinct benefit for maintaining the emulsion structure of the blend.
  • An additional benefit of using this apparatus is that it is more effective when used with small amounts of lubricant, which assures better control of the strength and sensitivity of the explosive blend owing to the decreased risk of dilution.
  • a lubricating liquid flow rate which is no greater than about 5%, and usually no greater than about 0.5-2%, of the emulsion/N blend flow rate is used.
  • water is the preferred lubricating liquid, on the basis of low cost, low viscosity, and immiscibility with the emulsion/AN blend being pumped.
  • Additives such as ethylene glycol may be added to the water to reduce its freezing point during cold weather.
  • the water need not be of high purity or even potable. Therefore, any naturally occurring water available at the field site of use can generally be used even though such waters, whether from streams, wells, or the sea, invariably contain some dissolved salts.
  • annular lubricant method can be carried out with intermittent pumping, if desired, even in the case in which water is the lubricating liquid.
  • plugging of the delivery conduit does not occur on stoppage of the pumping operation when a water annulus is used. It is believed that the avoidance of the swelling/plugging problem in the annular lubricant pumping method is related to the nature of the continuous phase in the explosive emulsion used in the present blend, and more particularly to the hydrophobicity thereof resulting from the emulsifying agent or system therein.
  • the fatty acid salt, and especially the equilibrium structure of the emulsifying system produced when the emulsifying agent is formed in situ provide a uniquely hydrophobic environment between the lubricating liquid on the outer surface of the emulsion/AN blend and the aqueous phase droplets within the blend, thereby preventing the absorption of the lubricating liquid into the blend despite the presence of a concentration gradient between the lubricating liquid and the aqueous phase droplets.
  • a matching of such concentrations is unnecessary with the present blends, and any available water supply can be used to provide the lubricating liquid.
  • Samples B, C and D which are samples of "low oil" emulsions that would be used, for example, in packaged ANFO blends of this invention, were prepared by the method described in Example 1 of U.S. Patent 4,287,010, with variations in mixer speeds as will be described.
  • the percentages given for oleic acid and ammonium hydroxide represent the proportions used to prepare ammonium oleate in situ.
  • Sample A is a sample of an emulsion of the type described in U.S. Patent 3,447,978, in which a non-ionic emulsifying agent is present.
  • DSC Differential Scanning Calorimeter
  • Blend A the blend with ANFO
  • Blend B the blend with ANWAX
  • Emulsion/ANFO blends of various component ratios were prepared by mixing ANFO with an emulsion of the following formulation, prepared as described in Example 1 of U.S. Patent 4,287,010:
  • the following "high oil" emulsions (22.5 kg mixes) were prepared in a 19-liter mixer by adding a 50% aqueous solution of sodium hydroxide to an aqueous solution of ammonium nitrate at 77°C, and adding the base-containing aqueous nitrate solution slowly with agitation to a 30°C solution of oleic acid in a 3/1, by weight, mixture of No. 2 fuel oil and Gulf Endurance No. 9 oil.
  • the agitator tip speed was 133 cm/sec during ingredient addition, and 400 cm/sec during a subsequent 5-minute shear cycle.
  • the emulsions were then sheared further to reduce the cell size sufficiently to produce a viscosity comparable to that achievable by mixing at 600 cm/sec for an additional 2 minutes.
  • Emulsions A through E (at ambient temperature) were mixed with AN prills to form blends A through E respectively.
  • the mixing was carried out in a cement mixer at medium speed for 4 minutes.
  • a typical emulsion which would be blended in the same manner as emulsions A through E above is formulated from the following ingredients:
  • emulsions were "high oil” control emulsions (i.e., they contained sufficient oil to oxygen-balance the blend with AN prills) that contained a non-ionic emulsifier in three different concentrations, only two of which (in emulsions O and P) were sufficient to prevent "creaming" of the oil phase.
  • the aqueous phase was a solution which consisted of 69.6% ammonium nitrate, 15.5% sodium nitrate (SN), and 14.9% water by weight.
  • Emulsions K, L, and M were prepared according to the procedure described in Example 6 (with the exception that SN was included in the aqueous phase).
  • Emulsions N, 0, and P were prepared by adding sorbitan monooleate to the oil, and the AN/SN solution to the oil solution.
  • the extendospheres (fly ash) were added during the addition of the AN/SN solution to the oil.
  • Emulsion viscosities were measured with a Brookfield viscometer at 29°C using a 2 rpm Type E spindle.
  • the blends were made by mixing the emulsion and AN prills with low shear, by hand with a spatula.
  • Viscosities were measured (as described for the emulsion except at 25°C) on the freshly made blends as well as on two- and six-day-old blends. Plots of viscosity vs. time for blends K through P are shown in Fig. 3. All blends had initial viscosities in the 2000-4000 poise range. However, while blends of the invention, i.e., blends K, L, and M, showed only a modest viscosity rise over a six-day period, reaching viscosities of only about 4500-5000 poise after six days, the control blends O and P showed a rapid rise within only two days.
  • Control blend N made from emulsion N, which contained an SMO concentration which was so low as to be insufficient to maintain emulsion stability, exhibited a low rate of viscosity rise over a two-day period, but rose rapidly in viscosity over the next four days.
  • the extremely high viscosities of control blends 0 and P after two days rendered the blends essentially unpumpable (spefically, unable to flow by gravity from a tank to the suction of a pump), and indicated a deleterious change in the emulsion structure (crystallization in the aqueous phase) which characteristically compromises the blend's ability to detonate.
  • blends K, L, and M showed no visual evidence of crystallization and were suitable for pumping.
  • Blends R and S were 50/50 emulsion/AN prills.
  • Emulsion Q was blended in the same ratio with ANFO prills, i.e., AN prills lightly coated with fuel oil in a 94/6 AN/oil weight ratio. Blending was carried out in a cement mixer as described in Example 5. The results were as follows:
  • blend Q is comparable to blends R and S at age 39 days in terms of confined detonation velocity, blends R and S do not require confinement at this age (nor does blend S require it at age 60 days) to detonate at acceptable velocities.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Liquid Carbonaceous Fuels (AREA)
  • Colloid Chemistry (AREA)
  • Silicon Compounds (AREA)
EP84303208A 1983-05-12 1984-05-11 Stable ammonium nitrate-emulsion explosives and emulsion for use therein Expired - Lifetime EP0131355B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT84303208T ATE51393T1 (de) 1983-05-12 1984-05-11 Stabile ammoniumnitratemulsionssprengstoffe und verwendung einer solchen emulsion.

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US49391683A 1983-05-12 1983-05-12
US493916 1983-05-12
US57660284A 1984-02-03 1984-02-03
US576602 1984-02-03

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EP0131355A2 EP0131355A2 (en) 1985-01-16
EP0131355A3 EP0131355A3 (en) 1985-05-29
EP0131355B1 true EP0131355B1 (en) 1990-03-28

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KR (1) KR910003094B1 (no)
AU (1) AU573217B2 (no)
BR (1) BR8402200A (no)
CA (1) CA1217342A (no)
CS (1) CS345884A3 (no)
DE (1) DE3481767D1 (no)
ES (1) ES8703394A1 (no)
GB (1) GB2140404B (no)
HK (1) HK17988A (no)
IE (1) IE57411B1 (no)
IN (1) IN162344B (no)
MA (1) MA20117A1 (no)
MX (1) MX162156A (no)
MY (1) MY100182A (no)
NO (1) NO841906L (no)
NZ (1) NZ208130A (no)
OA (1) OA07771A (no)
PT (1) PT78579B (no)
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MW2884A1 (en) * 1984-02-08 1986-08-13 Aeci Ltd An explosive which includes an explosive emulsion
NO168886C (no) * 1985-10-15 1992-04-15 Explosives Technologies Intern Lagringsstabilt emulsjonsblandingssprengstoff med forbedret vannbestandighet.
ZA888819B (en) * 1987-12-02 1990-07-25 Ici Australia Operations Process for preparing explosive
ZA891501B (en) * 1988-03-02 1989-11-29 Ici Australia Operations Explosive composition
GB9003613D0 (en) * 1990-02-16 1990-04-11 Explosives Tech Eti Method of reducing the overloading of a borehole and explosive composition used therefor
DE19649763A1 (de) * 1996-11-30 1998-06-04 Appenzeller Albert Sprengstoff für zivile, insbesondere bergmännische Zwecke
ES2123468B1 (es) 1997-06-26 2000-02-01 Espanola Explosivos Procedimiento e instalacion para la sensibilizacion in situ de explosivos de base acuosa.
AUPQ105299A0 (en) * 1999-06-18 1999-07-08 Orica Australia Pty Ltd Emulsion explosive
AUPR024400A0 (en) * 2000-09-20 2000-10-12 Orica Explosives Technology Pty Ltd Sensitisation of emulsion explosives
RU2252926C2 (ru) * 2003-08-25 2005-05-27 ОАО "Знамя" Состав эмульсионного взрывчатого вещества
RU2446134C1 (ru) * 2010-07-23 2012-03-27 Федеральное Казенное Предприятие "Бийский Олеумный Завод" Состав эмульсионного взрывчатого вещества
CN105272783A (zh) * 2015-11-10 2016-01-27 天津宏泰华凯科技有限公司 一种乳化炸药的乳化制药系统

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US3161551A (en) * 1961-04-07 1964-12-15 Commercial Solvents Corp Ammonium nitrate-containing emulsion sensitizers for blasting agents
US3447978A (en) * 1967-08-03 1969-06-03 Atlas Chem Ind Ammonium nitrate emulsion blasting agent and method of preparing same
GB1306546A (en) * 1970-06-09 1973-02-14 Explosives & Chem Prod Blasting explosive composition
US4181546A (en) * 1977-09-19 1980-01-01 Clay Robert B Water resistant blasting agent and method of use
US4111727A (en) * 1977-09-19 1978-09-05 Clay Robert B Water-in-oil blasting composition
NZ192888A (en) * 1979-04-02 1982-03-30 Canadian Ind Water-in-oil microemulsion explosive compositions
US4259977A (en) * 1979-04-16 1981-04-07 Atlas Powder Company Transportation and placement of water-in-oil emulsion explosives and blasting agents
US4287010A (en) * 1979-08-06 1981-09-01 E. I. Du Pont De Nemours & Company Emulsion-type explosive composition and method for the preparation thereof
EP0099695B1 (en) * 1982-07-21 1988-01-27 Imperial Chemical Industries Plc Emulsion explosive composition
US4404050A (en) * 1982-09-29 1983-09-13 C-I-L Inc. Water-in-oil emulsion blasting agents containing unrefined or partly refined petroleum product as fuel component

Also Published As

Publication number Publication date
PT78579A (en) 1984-06-01
IN162344B (no) 1988-05-07
MY100182A (en) 1990-03-29
CS345884A3 (en) 1992-11-18
TR22230A (tr) 1986-10-09
ES532316A0 (es) 1987-02-16
BR8402200A (pt) 1984-12-18
ZW7684A1 (en) 1984-07-25
NZ208130A (en) 1990-04-26
HK17988A (en) 1988-03-11
GB8412026D0 (en) 1984-06-20
MA20117A1 (fr) 1984-12-31
IE57411B1 (en) 1992-08-26
DE3481767D1 (de) 1990-05-03
IE841170L (en) 1984-11-12
PT78579B (en) 1986-06-26
AU2789484A (en) 1984-11-15
GB2140404B (en) 1987-09-03
CA1217342A (en) 1987-02-03
EP0131355A2 (en) 1985-01-16
KR910003094B1 (ko) 1991-05-18
GB2140404A (en) 1984-11-28
KR850002250A (ko) 1985-05-10
MX162156A (es) 1991-04-03
ES8703394A1 (es) 1987-02-16
NO841906L (no) 1984-11-13
OA07771A (fr) 1985-08-30
AU573217B2 (en) 1988-06-02
EP0131355A3 (en) 1985-05-29

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