Classifications

• • 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

Definitions

• explosive blasting slurries containing aqueous solutions of ammonium nitrate and other powerful inorganic oxidizers plus thickeners, fuels and sensitizers, have come into extensive use, particularly in the hard rock mining and construction industries.
• These slurry compositions are commonly made up of an aqueous solution of ammonium nitrate, to which sodium nitrate may be added.
• the solution is thickened with guar gum and/or starch to a viscous heavy liquid or gel, and sensitized usually with high energy fuels such as powdered aluminum and/or self-explosives such as TNT.
• the liquid component has included non-aqueous but water-compatible liquids, such as alcohols, glycols, amides such as forrnamide, and analogous nitrogen-containing liquids having fuel value as well as having the solvation or extender properties of liquids.
• non-aqueous but water-compatible liquids such as alcohols, glycols, amides such as forrnamide, and analogous nitrogen-containing liquids having fuel value as well as having the solvation or extender properties of liquids.
• Typical of such slurries are those described in U.S. Pat. No. 2,930,685 and U.S. Reissue Pat. No. 25,695 to Cook and Farnam, also in U.S. Pats. Nos.
• any combination of calcium nitrate as an oxidizer, with its known insensitivity, and of relatively high water content in a blasting slurry would be expected to be so dead or insensitive as to be impractical.
• calcium nitrate usually contains considerable water of crystallization and this would appear to be a deterrent to its use.
• the content of such water of crystallization in calcium nitrate varies somewhat from place to place, depending on storage conditions and on the various processes of manufacture. It usually runs about 14%, more or less, by weight in commercial calcium nitrate.
• Calcium nitrate slurries can be made having relatively high density or specific gravity, as compared with slurries made up primarily of ammonium nitrate and other conventional ingredients.
• the slurries of the present invention require considerably less water to render them fluid, due to release of the water of crystallization normally present in calcium nitrate, when made by the process of this invention; the water requirements can be reduced further and advantageously by substitution of ethylene glycol or analogous organic liquid for part or most of the water.
• Calcium nitrate per se can easily be produced in situ and in the field and, using cheap starting materials.
• the congelation temperature or fudge point of slurries containing calcium nitrate can be lower, other things being equal or, alternatively, larger total salt proportions can be used without raising the fudge point.
• a further advantage of the use of calcium nitrate, according to the present invention is the possibility of using products of higher density.
• Conventional slurries often are sensitized in part by inclusion of fine bubbles of air or other gases provided their densities are not too high. They do not appear to respond very well to sensitization by such gas bubbles when made with densities exceeding about 1.4 grams per cubic centimeter. This limitation appears not to apply in the same degree to the slurries of the present invention.
• a significant aspect of the present invention pertains to the fudge" point or congelation temperature of the composition.
• a solution of the oxidizer salt which is usually ammonium nitrate or a combination of sodium nitrate and ammonium nitrate, is dissolved in hot water. Thereafter, fuels and/or sensitizers, etc., in solid particulate form and usually insoluble in the liquid are added to the solution. As the resulting slurry cools, it reaches a point at which the salts in solution begin to precipitate, causing a rapid thickening or solidification. The temperature at which this occurs is the so-called fudge" point and it varies with the composition. Obviously, it is desirable to have a fudge point low enough that necessary mixing and pumping of the slurry can be accomplished before the material starts to solidify, that is, before the fudge point is reached.
• a series of samples of explosive slurry were made up, simply using calcium nitrate to replace part of the normal ammonium nitrate and/or sodium nitrate, as follows. Parts shown-are percentage by weight.
• Smokeless powder 28 Density 1.40 at 1.34 at Composition A was prepared by dissolving the sodium nitrate first in warm water, 70 C, then adding the ammonium nitrate and calcium nitrate together. In these tests a Norwegian calcium nitrate was used. This composition was not tested for detonation but would be expected to be detonable and it had a good consistency. In Compositions B and C test charges were made up in 2 inches, 2 16 inches, and 3 inches diameters, in lengths six times the diameter. The 2 inches charges failed to detonate completely but the larger charges were all fired successfully with a standard booster. For Composition D the proportions starred made up 100% of the solution. For sensitizer, 28 parts of I-ISSP double base smokeless powder was used. This product had a solution density (before addition of smokeless powder) of 1.61. Density after addition of the SP was not determined. This product fired in a 2-inch column with a standard 2A booster.
• Ammonium nitrate (AN) 32.5 or 35.9% Calcium nitrate (CN) 37.0 or 40.8% Sodium nitrate (SN) 5.5 or 6.06% Water 5.5 or 6.06% Ethylene glycol 10.0 or 11.03% Guar gumcommercial 0.2 or 0.22%
• the sodium nitrate was dissolved first in the water and then the 'calcium nitrate and ammonium nitrate were added together to the solution. Temperature of this mixture was about 70 C. Water of crystallization released from the calcium nitrate helped maintain liquidity. This total mixture had a pH of about 4.5 and an oxygen balance ofabout +1 1%.
• the guar gum was dispersed in the ethylene glycol and the resulting dispersion added to the oxidizer mixture.
• the resulting composition was a solution having somewhat higher viscosity than an ordinary aqueous solution of the same salts. It was cooled down to about 50 C before adding particulate fuel or sensitizer ingredients in the form of various pre-mixes mentioned below. This solution had a fudge point (congelation temperature) of about 35 C.
• a cross-linking agent In order to cross-link the gum to get higher viscosity and thus prevent segregation of suspended fuel particles, etc., a cross-linking agent or in some cases a combination of oxidizerreducer agents was used.
• Gallic acid or potassium antimony tartrate was used as reducing agent in a number of examples.
• gassing agents such as nitrous acid or ammonium, sodium or potassium nitrite were added in very small proportions, sometimes with melamine or thiourea to accelerate aeration.
• Hydrogen peroxide was used in some cases, along with traces of potassium iodide or manganese dioxide to catalyze decomposition.
• Composition E had a density of 1.14 g/cc. and was fired successfully in 3-inch, 2 -inch and 2-inch diameter columns at 0 C, using a standard booster. A similar composition having higher density 1.22, failed in a 2-inch column at the same temperature.
• Example F with a density of 1.19 fired successfully under similar conditions as did Example G with a density of 1.06.
• Critical density for a 2 %inch column appears to be about 1.20.
• a column of slurry explosive is tall, and where its own hydrostatic head, plus stemming, compresses it supplemental aeration or gassing may be needed.
• the sensitivity at 0 C is considered quite remarkable for a slurry explosive containing no self-explosive and no paint grade aluminum powder.
• compositions of Examples E, F and G were treated with 0.2, 0.1 and 0.3 cc, respectively (per 100 grams) of concentrated (58%) nitric acid to reduce the pH to where thickening could be accomplished successfully with potato starch. Additional experiments were made to obtain a thickening system that would be effective without reducing the pH by use of acid.
• Penetration of the slurry as an indication of its viscosity was measured by use of a specially designed cone-shaped penetrometer. These readings were taken after 5 minutes and after 10 minutes, shown in this order; likewise, densities are given after 5 minutes, 30 minutes and 24 hrs. to show effectiveness of gassing.
• Blasting slurries must be at least reasonably stable in composition, consistency and density, particularly when they are packaged or are to be used in boreholes where they may stand 24 hours or more before use. If the gel breaks down (or viscosity decreases) so as to permit segregation of the suspended fuel and sensitizer particles (called pre-mix) the composition may become worthless. If it loses its aeration or entrapped gas it may become so insensitive that it will not detonate. Likewise, if placed in deep boreholes, the lower part of the explosive column may be under sufficient hydrostatic or superimposed pressure that the charge will not detonate, or at least will not detonate all the way.
• a particular object, realized in this invention, was to obtain stable gassed slurries that can be detonated in 2 -inch columns or larger, at temperatures as low as 5 C and under pressures of up to 50 psi.
• the products described in Table III above meet these requirements. Many, perhaps most, of the blasting slurries of the prior art fall far short of the latter requirement.
• ethylene glycol with its fuel value and its lowtemperature solvent properties, as a significant ingredient is one important feature.
• a mixture of oxidizers containing ammonium nitrate and sodium nitrate also is usually preferred.
• a fudge point as low as 35 C is quite remarkable and some of these products have such.
• an effective cross-linking system such as dichromategallic acid or other oxidation-reduction combinations, which are reasonably independent of pH is important. While acid can be added to slurries to reduce their pH and improve the thickening or gelling effect of starches and gums, this is often quite undesirable.
• compositions of this invention have all these desirable properties, including density control when the slurry is under the pressure of a tall column in a borehole. They may include various combinations of inorganic oxidizer salts such as nitrates, chlorates and perchlorates.
• the slurries of this invention include at least 5% by weight of ethylene glycol as a fuel and liquid extender, at least 10% of calcium nitrate, a stable thickening system, and enough gassing agent to keep the slurry at density not exceeding 1.20 g/cc under 50 psi pressure.
• ethylene glycol as a fuel and liquid extender
• calcium nitrate a stable thickening system
• gassing agent to keep the slurry at density not exceeding 1.20 g/cc under 50 psi pressure.
• Particularly preferred are slurries containing at least 8% of ethylene glycol, at least 20% of calcium nitrate, and less than 8% added water.
• propylene glycol can be used in lieu of part or all of the ethylene glycol;
• a pumpable and pourable aqueous slurry blasting composition of low water content and high sensitivity comprising a liquid phase which includes a solution of powerful oxidizer salts selected from the group which consists of inorganic nitrates, chlorates and perchlorates and including at least 10% by weight, based on the total composition, of calcium nitrate, said liquid comprising water and ethylene glycol and including a viscosity-increasing agent in the liquid phase per se to impart thereto a viscosity sufficient to entrap and hold tiny bubbles of gas dispersed in said phase, a sufficient quantity of gas in the form of tiny bubbles being dispersed throughout said liquid phase to substantially enhance the sensitivity of the whole composition to detonation, and a storage stable, strongly cross-linked thickener or gel former selected from the group which consists of polysaccharide gums and starches in proportions sufficient to permanently hold said gas bubbles dispersed in situ and also to inhibit segregation of solid particles suspended in the liquid phase and
• composition according to claim 1 which contains at least 8% of ethylene glycol and wherein the thickener is crosslinked by a combination oxidation-reduction cross-linking system.
• composition according to claim 1 wherein the slurry contains sufficient gassing agent to hold its density below 1.2 grams per cubic centimeter under a pressure of 50 psi.
• Composition according to claim 1 in which there is at least 20% by weight, based on total composition, of calcium nitrate.
• composition according to claim 1 which includes at least 8% of ethylene glycol.
• Composition according to claim 1 which includes at least l0% of calcium nitrate, at least 8% of ethylene glycol, and not more than 8% of water, not including water of crystallization associated with said calcium nitrate.
• Composition according to claim 1 which includes at least 5% of ethylene glycol, at least 10% of calcium nitrate, an oxidation-reduction cross-linked gel former, and sufficient gassing agent to keep the slurry density below 1.2 g/cc. under a pressure of 50 psi.
• composition according to claim 7 which includes finely divided aluminum as a fuel.
• Composition according to claim 7 which includes at least 8% of ethylene glycol, at least 20% of calcium nitrate, and which is sensitive to detonation in a 2-inch column at 10 C by a standard booster.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)
• Air Bags (AREA)
• Liquid Carbonaceous Fuels (AREA)
• Soil Conditioners And Soil-Stabilizing Materials (AREA)
• Fertilizers (AREA)
• Treatment Of Sludge (AREA)

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Citations (4)

• 1969
  • 1969-05-01 US US821095A patent/US3660181A/en not_active Expired - Lifetime
• 1970
  • 1970-04-21 IE IE509/70A patent/IE34109B1/xx unknown
  • 1970-04-21 GB GB08908/70A patent/GB1301185A/en not_active Expired
  • 1970-04-27 DE DE2020490A patent/DE2020490C3/de not_active Expired
  • 1970-04-28 JP JP45036003A patent/JPS5034606B1/ja active Pending
  • 1970-04-28 BE BE749690D patent/BE749690A/xx not_active IP Right Cessation
  • 1970-04-29 ES ES379151A patent/ES379151A1/es not_active Expired
  • 1970-04-29 IL IL34412A patent/IL34412A/en unknown
  • 1970-04-29 NL NL7006308A patent/NL7006308A/xx unknown
  • 1970-04-30 FI FI1228/70A patent/FI56167C/fi not_active IP Right Cessation
  • 1970-04-30 PH PH11390A patent/PH9787A/en unknown
  • 1970-04-30 CA CA081604A patent/CA925302A/en not_active Expired
  • 1970-04-30 CH CH649970A patent/CH553733A/de not_active IP Right Cessation
  • 1970-04-30 FR FR7015969A patent/FR2047172A5/fr not_active Expired
  • 1970-04-30 AT AT396870A patent/AT299041B/de not_active IP Right Cessation
  • 1970-04-30 NO NO1663/70A patent/NO125443B/no unknown
  • 1970-06-29 OA OA53967A patent/OA03307A/xx unknown

Patent Citations (4)

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