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
  • 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
  • C06B23/00—Compositions characterised by non-explosive or non-thermic constituents

Definitions

• the present invention relates to an improved explosive composition. More particularly, the invention relates to a water-in-oil emulsion explosive that has increased thermal compatibility with sulfide/pyrite containing ores that typically are reactive with nitrate salts, especially ammonium nitrate.
• the water-in-oil emulsion explosives of this invention contain a water-immiscible organic fuel as a continuous phase, an emulsified inorganic oxidizer salt solution as a discontinuous phase, an emulsifier, gas bubbles or an air entraining agent for sensitization, and from about 1% to about 30% by weight of the composition urea for stabilization against thermal degradation with reactive sulfide/pyrite ores.
• the invention also relates to a method of using such explosives.
• water-in-oil will refer to a discontinuous phase of polar or water-miscible droplets emulsified throughout a nonpolar or water-immiscible continuous phase. Such emulsions may or may not actually contain water, and those not containing water sometimes are referred to as “melt-in-oil” emulsions.
• the invention comprises the addition of urea to a water-in-oil emulsion explosive having an organic fuel as a continuous phase, an inorganic nitrate based oxidizer salt solution as a discontinuous phase, an emulsifier and chemically formed gas bubbles or air void containing solid additives.
• the urea is preferably dissolved in the oxidizer phase but may be added as a powdered or prilled solid phase.
• the explosive may either be packaged before loading into the borehole or may be bulk delivered.
• the explosive is compatible with reactive ores containing sulfides or pyrites.
• urea As indicated above the addition of urea to an emulsion explosive as a dry powder, dry prill or preferably dissolved in the oxidizer phase greatly reduces the reactivity of the nitrate salts in the emulsion with sulfide/pyrite ores. As low as about 1% dissolved or dispersed urea can have a dramatic effect on explosive/ore compatibility. In practice, larger amounts are advantageous and urea levels up to about 30% are feasible. The degree of effectiveness generally is proportional to the amount of urea employed. However, for reasons of optimizing oxygen balance, energy and effectiveness, the preferred range is from about 5 to about 20% urea.
• a urea-treated emulsion has several advantages over a urea-treated ANFO. Firstly, emulsions have well-known advantages in general, i.e., water resistance, higher density and better detonation performance. Secondly, the external fuel phase of an emulsion provides an additional barrier for protection against reaction of internal phase oxidizer salts with the ore. Finally, the intimate mixture of urea dissolved in the nitrate oxidizer solution provides greater and more reliable protection from reaction than the physical mixture of urea with nitrate salts, even with powdered urea.
• urea Another advantage of urea is its eutectic behavior in combination with AN and other nitrate salts.
• a relatively lower amount of water is needed to obtain a desired temperature of crystallization of the-internal oxidizer phase of the emulsion.
• the need for less water is particularly advantageous in hot, reactive ore deposits, which may be encountered in sulfide/pyrite ores. In that circumstance, a lower amount of water means less potential volatilization and hence less destabilization.
• the immiscible organic fuel forming the continuous phase of the composition is present in an amount of from about 3% to about 12%, and preferably in an amount of from about 4% to about 8% by weight of the composition.
• the actual amount used can be varied depending upon the particular immiscible fuel(s) used and upon the presence of other fuels, if any.
• the immiscible organic fuels can be aliphatic, alicyclic, and/or aromatic and can be saturated and/or unsaturated, so long as they are liquid at the formulation temperature.
• Preferred fuels include tall oil, mineral oil, waxes, paraffin oils, benzene, toluene, xylenes, mixtures of liquid hydrocarbons generally referred to as petroleum distillates such as gasoline, kerosene and diesel fuels, and vegetable oils such as corn oil, cotton seed oil, peanut oil, and soybean oil.
• Particularly preferred liquid fuels are mineral oil, No. 2 fuel oil, paraffin waxes, microcrystalline waxes, and mixtures thereof.
• Aliphatic and aromatic nitro-compounds and chlorinated hydrocarbons also can be used. Mixtures of any of the above can be used.
• the emulsifiers for use in the present invention can be selected from those conventionally employed, and are used generally in an amount of from about 0.2% to about 5%.
• Typical emulsifiers include sorbitan fatty esters, glycol esters, substituted oxazolines, alkylamines or their salts, derivatives thereof and the like. More recently, certain polymeric emulsifiers, such as a bis-alkanolamine or bis-polyol derivative of a bis-carboxylated or anhydride derivatized olefinic or vinyl addition polymer, have been found to impart better stability to emulsions under certain conditions.
• solid or other liquid fuels or both can be employed in selected amounts.
• solid fuels which can be used are finely divided aluminum particles; finely divided carbonaceous materials such as gilsonite or coal; finely divided vegetable grain such as wheat; and sulfur.
• Miscible liquid fuels also functioning as liquid extenders, are listed below. These additional solid and/or liquid fuels can be added generally in amounts ranging up to about 25% by weight.
• the inorganic oxidizer salt solution forming the discontinuous phase of the explosive generally comprises inorganic oxidizer salt, in an amount from about 45% to about 95% by weight of the total composition, and water and/or water-miscible organic liquids, in an amount of from about 0% to about 30%.
• the oxidizer salt preferably is primarily ammonium nitrate, but other salts may be used in amounts up to about 50%.
• the other oxidizer salts are selected from the group consisting of ammonium, alkali and alkaline earth metal nitrates, chlorates and perchlorates. Of these, sodium nitrate (SN) and calcium nitrate (CN) are preferred.
• solid oxidizer When higher levels of urea, 10-15% by weight or more, are dissolved in the oxidizer solution phase, solid oxidizer preferably should be added to the formed emulsion to obtain optimal oxygen balance and hence energy.
• the solid oxidizers can be selected from the group above listed. Of the nitrate salts, sodium nitrate is preferred because of its lower reactivity with the problem ores and because of its high oxygen content. An oxygen balanced product would be particularly necessary in underground applications where noxious fumes would be a problem.
• Water preferably is employed in amounts of from about 1% to about 30% by weight based on the total composition. It is commonly employed in emulsions in an amount of from about 9% to about 20%, although emulsions can be formulated that are essentially devoid of water. With higher levels of urea, such as 15% or more, the compositions easily can be made anhydrous.
• Water-miscible organic liquids can at least partially replace water as a solvent for the salts, and such liquids also function as a fuel for the composition. Moreover, certain organic compounds also reduce the crystallization temperature of the oxidizer salts in solution.
• Miscible solid or liquid fuels in addition to urea, already described can include alcohols such as sugars and methyl alcohol, glycols such as ethylene glycols, amides such as formamide, amines, amine nitrates, and analogous nitrogen-containing fuels.
• the amount and type of water-miscible liquid(s) or solid(s) used can vary according to desired physical properties. As already explained it is a particular advantage of this invention that substantial urea lowers the crystallization point of the oxidizer solution.
• Chemical gassing agents preferably comprise sodium nitrite, that reacts chemically in the composition to produce gas bubbles, and a gassing accelerator such as thiourea, to accelerate the decomposition process.
• a sodium nitrite/thiourea combination produces gas bubbles immediately upon addition of the nitrite to the oxidizer solution containing the thiourea, which solution preferably has a pH of about 4.5.
• the nitrite is added as a diluted aqueous solution in an amount of from less than 0.1% to about 0.4% by weight, and the thiourea or other accelerator is added in a similar amount to the oxidizer solution.
• hollow spheres or particles made from glass, plastic or perlite may be added to provide density reduction.
• the emulsion of the present invention may be formulated in a conventional manner.
• the oxidizer salt(s), urea and other aqueous soluble constituents first are dissolved in the water (or aqueous solution of water and miscible liquid fuel) at an elevated temperature or from about 25.C to about 90.C or higher, depending upon the crystallization temperature of the salt solution.
• the aqueous solution which may contain a gassing accelerator, then is added to a solution of the emulsifier and the immiscible liquid organic fuel, which solutions preferably are at the same elevated temperature, and the resulting mixture is stirred with sufficient vigor to produce an emulsion of the aqueous solution in a continuous liquid hydrocarbon fuel phase.
• compositions also can be prepared by adding the liquid organic to the aqueous solution). Stirring should be continued until the formulation is uniform.
• gassing which could be immediately after the emulsion is formed or up to several months thereafter when it has cooled to ambient or lower temperatures
• the gassing agent and other advantageous trace additives are added and mixed homogeneously throughout the emulsion to produce uniform gassing at the desired rate.
• the solid ingredients, if any, can be added along with the gassing agent and/or trace additives and stirred throughout the formulation by conventional-means. Packaging and/or further handling should quickly follow the addition of the gassing agent, depending upon the gassing rate, to prevent loss or coalescence of gas bubbles.
• the formulation process also can be accomplished in a continuous manner as is known in the art.
• Table I shows examples of the present invention. Each emulsion composition was mixed with 40% of a nitrate reactive ore, and a differential thermal analysis was run on the mixture. Relative results of these runs also are included in the table.
• Example 1 contained no urea and showed a strong exotherm commencing at ⁇ 57°C.
• Example 2 contained only 1% urea, but showed a dramatic reduction in exotherm intensity, even though a small exotherm was evident. The exotherm intensity further was reduced by doubling the urea content as shown in Example 3. This low temperature exotherm becomes essentially unobservable as the urea content is increased incrementally in Examples 4 to 8 to near 30%.
• Comparison Examples 9 and 10 illustrate the invention in compositions containing calcium nitrate.
• compositions of the present invention can be delivered in bulk form to a borehole containing reactive sulfide or pyrite ores, using methods well known in the art, or can be used in packaged form.
• a packaged product is preferred over a bulk product in boreholes having reactive ores, particularly where longer sleeptimes of the product in the borehole is anticipated, since the packaging provides some inherent protection.
• Borehole liners also can provide extra protection in situations where bulk-loaded products are used.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)
• Liquid Carbonaceous Fuels (AREA)
• Manufacture And Refinement Of Metals (AREA)

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Cited By (11)

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• 1991
  • 1991-05-23 AU AU77278/91A patent/AU639562B2/en not_active Revoked
  • 1991-05-28 CA CA002043369A patent/CA2043369C/fr not_active Expired - Lifetime
  • 1991-05-29 ZA ZA914103A patent/ZA914103B/xx unknown
  • 1991-06-06 EP EP19910305117 patent/EP0460952A3/en not_active Ceased

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