Classifications

• • 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
  • C06B31/28—Compositions containing an inorganic nitrogen-oxygen salt the salt being ammonium nitrate
  • C06B31/32—Compositions containing an inorganic nitrogen-oxygen salt the salt being ammonium nitrate with a nitrated organic compound
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B25/00—Compositions containing a nitrated organic compound
  • C06B25/36—Compositions containing a nitrated organic compound the compound being a nitroparaffin
• • 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
  • C06B31/02—Compositions containing an inorganic nitrogen-oxygen salt the salt being an alkali metal or an alkaline earth metal nitrate
  • C06B31/12—Compositions containing an inorganic nitrogen-oxygen salt the salt being an alkali metal or an alkaline earth metal nitrate with a nitrated organic compound
• • 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

• ANE ammonium nitrate emulsions suspensions or gels
• a second problem is the problem of getting the explosive underground in the first place. Since this must be done by transporting it in containers using the same lifting equipment or access ways used for men, equipment and ore, this can seriously hamper production. Since they are non-explosive until they are pumped into the shot hole it is at least theoretically possible to pump them through a long pipeline to the point where they are needed underground.
• the viscosity is a problem as there is a finite limit on how far a viscous fluid can be pumped bearing in mind the energetic nature of the material being pumped and therefore the limitation on maximum pumping pressure to which it can be exposed.
• the physical nature of the ANE's is another limitation as to the distance that it can be transported in a pipeline.
• the product In the case of a watergel or a slurry type ANE the product is in the form of a saturated solution of oxidizer salts and soluble fuels thickened with a thickener of some sort (normally guar gum) into which is mixed further quantities of oxidizer salts and (possibly) insoluble fuels.
• a thickener of some sort normally guar gum
• When pumping such a suspension through a very long line one runs the risk of the solids blocking the line entirely and stopping the pumping process entirely. If one were considering dropping or pumping such a suspension through a long vertical (or inclined) pipe in order to get it underground the risk of the pipeline blocking would be so great as to make this a foolhardy exercise indeed.
• emulsion type ANE these are made by preparing a solution of oxidizer salts in water at an elevated temperature and then emulsifying this solution into a fuel phase consisting of oil and emulsifier and then allowing the emulsion to cool down to ambient temperature. Due to the very small size of the emulsion micelles the salts are incapable of recrystallizing. It must be remembered that the fuel phase of the emulsion only makes up about 6% or 7% of the product and that this is the continuous phase. The oxidizer salt solution makes up in excess of 90% of the emulsion and this is the disperse phase.
• Theft is also a major problem both of packaged explosive and of bulk explosives used in the mining industry. Stolen explosives can find their way into the hands of criminals or terrorists and are a major threat to the public.
• an aqueous oxidizer solution containing a mixture of dissolved oxidizing salts, for use in the preparation of explosives formulations which has a crystallization point of below 30°C, preferably below 25°C, as low as 15°C or less, as low as 10°C or less, as low as 5°C or less, even as low 0°C or less, said solution containing:
• the molar concentration of ammonium nitrate to calcium nitrate or mixture of calcium nitrate and magnesium nitrate is between 0.25: 1 and 2:1 , preferably between 0.5: 1 and 1.5: 1 , more preferably between 0.75: 1 and 1.25:1 and most preferably approximately 1.
• crystalstallization point is meant the temperature at which one or more of the dissolved oxidizing salt/s begin to precipitate from the oxidizer solution.
• the ratio of the molar concentrations of the calcium nitrate to the magnesium nitrate should not be less than about 4:1 and preferably not less than about 4.5:1.
• the oxidizer solution has a water content of between 10% and 25%, between 12% and 24%, preferably between 17% and 22%, by mass.
• the solution preferably further contains alkylamine nitrate.
• the alkylamine nitrate may be present in an amount of 1 % to 20% by mass, typically in an amount of 10% to 18% by mass, or from 12% to 17% by mass.
• the solution preferably contains at least an additional 1.67% alkylamine nitrate in order to retain a low crystallization point for the solution.
• the alkylamine nitrate may be methylamine nitrate (also called monomethylammonium nitrate), monoethanolamine nitrate, dimethylamine nitrate or trimethylamine nitrate, preferably methylamine nitrate.
• This solution can be used for the manufacture of either a watergel or an emulsion explosives or an ANE.
• Other nitrates such as magnesium nitrate, sodium nitrate and potassium nitrate can be introduced but these must be at molar concentrations significantly lower than the calcium nitrate.
• the invention also covers a method of manufacturing an explosives formulation by mixing the oxidizer solution described above with a fuel.
• the invention further covers an explosives formulation comprising a mixture of the oxidizer solution described above with a fuel.
• the fuel may be a hydrocarbon fuel such as diesel fuel, paraffin, oil etc, a water soluble alcohol or polyol (e.g. monoethylene glycol, glycerol, ethanol, methanol, propanol) a water soluble carbohydrate such as sugar.
• a watergel type ANE one might well choose a water soluble fuel, however immiscible fuels can also be used with great success to make a watergel. If one were making an emulsion type ANE then the choice would be for one of the hydrocarbon fuels mentioned above or even recovered lubricating or other oil such as vegetable oil.
• aqueous oxidizer solution containing a mixture of dissolved oxidizing salts with less than 25% water that does not crystallize below 30°C, at low temperatures below 25°C, below 10°C, and even as low as 0°C or less (as low as -7°C), and that can be used to make a watergel or an emulsion explosive or an ANE (ammonium nitrate emulsion suspension or gel) provided that it meets the following criteria:
• the solution contains 25% water or less
• the solution contains ammonium nitrate (NH 4 N0 3 ) and calcium nitrate (Ca(N0 3 ) 2 ) in a molar ratio of ammonium nitrate to calcium nitrate of between 0.25:1 and 2: 1 , preferably between 0.5: 1 and 1.5: 1 and preferably between 0.75: 1 and 1.25: 1 and most preferably as close to 1 : 1 as possible; and
• condition 2 can be restated as (for example):
• the solution contains ammonium nitrate and calcium nitrate in a percentage ratio of calcium nitrate to ammonium nitrate of between 8.2:1 and 1 : 1 and preferably between 4.1 : 1 and 1.37:1 and preferably between 2.73: 1 and 1.64: 1 and ideally as close to 2.05:1 as possible.
• the ratio of the molar concentration of ammonium nitrate to the sum of the molar concentrations of the calcium nitrate and the magnesium nitrate should be between 0.25:1 and 2: 1 , preferably between 0.5: 1 and 1 .5:1 and preferably between 0.75: 1 and 1.25: 1 and most preferably as close to 1 :1 as possible. Furthermore the ratio of the molar concentrations of the calcium nitrate to the magnesium nitrate should not be less than about 4:1 and preferably not less than about 4.5:1.
• the controlling factor is the ratio of molar concentrations of the ammonium nitrate and the calcium nitrate as well as the relative water and monomethylammonium nitrate percentages and the quantity of sodium or potassium nitrate that can be introduced is determined mainly by their solubility in the available water.
• This solution can then be used for manufacturing (among other things) watergel or emulsion explosives or ANE's. It can be most advantageously easily transported underground in deep level mines through relatively small diameter pipelines, using existing access ways and shafts, to the working places at which point it can then be converted into a watergel or emulsion explosive or an ANE.
• oxidizer solutions according to the present invention for making emulsion explosives
• This new system can provide a major step forward in the fight against criminal activity and terrorism, since it makes the theft of the explosives unattractive due to the extremely short shelf life of the final explosive.
• the solution could be thickened with a suitable thickener, such as guar gum and in this case one could use any one of the previously mentioned water soluble fuels or one of the hydrocarbon fuels.
• a suitable thickener such as guar gum
• a surfactant of some kind to assist in keeping the hydrocarbon in suspension.
• the fact that the watergel has no suspended solid means that it would be perfectly safe to drop it down a vertical pipe of virtually any length in order to get it from surface to underground.
• the solutions were made from 80% monomethylammonium nitrate solution and either solid ammonium nitrate or 88% ammonium nitrate solution as well as agricultural calcium nitrate manufactured by South African company OMNIA Fertilizer Ltd and sold under the trade name OMNICALTM which contains about 80% calcium nitrate and about 15% water with the balance being ammonium nitrate.
• the reason for using this and not chemically pure material is that the standard chemically pure calcium nitrate contains 30.5% water in the form of water of crystallization and by using the agricultural material I was able to prepare solutions containing high levels of calcium nitrate while still maintaining relatively low levels of water. The mixture was then heated to prepare a clear solution which was then cooled while stirring and the crystallization point was measured and reported as being the point at which the first crystals appeared.
• Ammonium nitrate (AN) (%) 7.0 12.5 17.1 21.0 24.2 27.0 29.5 31.6
• Monomethylammonium nitrate (%) 11.0 11.0 11.0 1 1.0 1 1.0 1 1 .0 11.0 1 1.0 11.0
• Monomethylammonium nitrate (%) 1 1.1 1 1.0 1 1.0 1 1.0 1 1.0 1 1.0 1 1.0 1 1.0 Crystallization point (°C) 53 48 25 17 9 17 27 32
• Table 5 looks at a series of results for solutions where the molar ratio of ammonium nitrate (AN) to calcium nitrate (CN) was held at 1 : 1 while the water content was reduced in 1 % steps from 24% to 14% while the monomethylammonium nitrate (MMAN) content was increased from 0 to 16.67% in steps of 1.67%. In every single case the crystallization point remained below 0°C.
• Table 6 looks at a series of results for solutions where the molar ratio of ammonium nitrate (AN) to calcium nitrate (CN) was once more held at 1 :1 while the water content was again reduced in 1 % steps from 24% to 14% while the monomethylammonium nitrate (MMAN) content was increased from 0 to 20% in steps of 2%. In every single case the crystallization point remained below 0°C. Table 6:
• Emulsion products were then prepared from solutions B4 and K3 in order to investigate their effectiveness as an explosive. These two solutions were chosen since they both crystallized at -4°C and both contained the same quantity of water but differing quantities of monomethylammonium nitrate in order to check the effect of the monomethylammonium nitrate on the explosive properties of the resulting emulsion explosive.
• the final products had the following analyses.
• Emulsions were each made into 50mm diameter cartridges, 600mm long, by loading into plastic lay-flat tubing (100 micron thick) and initiated with a 15g pentolite booster.
• Emulsion B4 initiated and detonated over its entire length at constant velocity as demonstrated by a witness pipe placed in contact with the cartridge which was flattened completely over the full length of the cartridge.
• Emulsion K3 failed to maintain detonation and most of the product was recovered. This trial indicates that the monomethylammonium nitrate not only improves the solubility of the salts at progressively lower water levels it also assists in the sensitivity of the final emulsion.
• This invention opens the way to transporting the aqueous oxidizer solution, the oil and emulsifier mixture and the gassing reagent separately to the mine. And then transporting them from surface to the underground workings through relatively small diameter pipelines, over any desired length, directly to the face to be blasted and then only mixing the three liquids (oxidiser solution, oil/emulsifier solution and gassing reagent) to form an explosive emulsion as they are pumped into the hole. It might also be feasible to emulsify the gassing reagent into the oil/emulsifier mixture and in this way only transport two liquids underground for mixing at the blast face. The point is that throughout there would be no need to keep the solution heated in heated storage vessels or heated and jacketed pipelines as would be needed with oxidizer solutions of the prior art.

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