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

• This invention relates to the manufacture of blasting explosive compositions, particularly but not exclusively slurry explosive compositions.
• Slurry explosive compositions are extensively used in many blasting operations.
• Known slurry explosives include thickened compositions normally comprising at least one inorganic oxidising salt, generally ammonium nitrate, at least one sensitizer, for example monomethylamine nitrate, water, a thickening agent, and if required a fuel, for example sulfur or a carbonaceous fuel, and/or a cross-linking agent, for example potassium pyroantimonate.
• Slurry explosive compositions can be formulated so as to be suitable as a general purpose blasting slurry explosive or as a permitted explosive of any of the classified groups P1 to P5.
• Permitted explosives are explosives designed for use in gassy or dusty coal mines and which have met stringent official safety tests for safety against the risk of igniting methane and coal dust.
• Formic acid has a boiling point of 100.9°C., but forms an azeotrope with water. Hence even prolonged distillation leaves a certain amount of formic acid in the reaction mixture.
• the residual formic acid can be neutralised with either gaseous or liquid ammonia or with caustic soda, the resulting quantity of formate formed by such neutralisation of the residual formic acid acts as a diluent in the final explosive composition, which owing to the high calorific value of the formate, reduces the strength of the explosive.
• the presence of any such formate appears to have a deleterious effect on the storage life of the explosive, resulting in exudation of amine nitrates when it is stored under warm conditions over an extended period of time.
• methyl alcohol is used, most of the formic acid is converted into methyl formate which distils over at about 35°C., while if ethyl alcohol is used, the formic acid can be recovered as ethyl formate which distils over at a temperature of 55-60°C.
• methyl formate or ethyl formate produced in this manner can be of commercial use, it will be appreciated that the foregoing procedure is a relatively expensive method of removing formic acid.
• the aqueous distillate contains about 12% by weight of formic acid and the recovery of an 85% or above concentrated formic acid from such a weak solution is not commercially viable. Neutralisation with either lime or caustic soda and the disposal of the resultant crude calcium formate or sodium formate respectively also poses problems. Thus the necessary removal of the formic acid presents both environmental and commercial problems.
• an oxidizer/sensitizer blend suitable for use in the formulation of blasting explosive compositions, particularly slurry explosive compositions, and comprising ammonium nitrate and a mixture of monomethylamine nitrate, dimethylamine nitrate and trimethylamine nitrate can be produced by reacting ammonium nitrate and formaldehyde in the liquid phase in the presence of urea, whereby the amount of formic acid present in the resulting reaction mixture can be reduced to the desired minimum. If required, the water content of the reaction mixture can be reduced by a subsequent evaporation step.
• urea reacts with some of the formaldehyde present in the reaction mixture to form monomethylol urea and/or dimethylol urea, which in the presence of the ammonium nitrate and the formic acid produced in the primary reaction form monomethylamine nitrate and/or dimethylamine nitrate with the evolution of carbon dioxide.
• the oxidizer/sensitizer blend produced in accordance with the invention can be employed in the production of various types of blasting explosive compositions.
• the blend can have incorporated therein in a known manner additional constituents selected from one or more additional oxidising salts, for example sodium perchlorate, sodium nitrate or solid ammonium nitrate, a thickening agent, for example guar gum, an auxiliary fuel, for example wood meal, graphite or sulfur, a cross-linking agent, for example potassium pyroantimonate, a stabilizer, for example sodium nitrite; or sodium chloride.
• the blend can have incorporated therein, for example,solid ammonium nitrate and guar gum.
• methylamine nitrate mixture can be evaporated in any suitable evaporation system to a water content that is desired in the final explosive.
• the distillate thus obtained contains only a minor quantity of formic acid, which can easily be neutralised and disposed of without causing environmental problems.
• reaction mixture was distilled in vacuo- until 250 ml. of water had been collected in the receiver. 95 M1. of a 55% solution of sodium perchlorate were added to the distilland and then a further quantity of 40 ml. of water was distilled off. Alternatively, 62 g. of solid sodium perchlorate (NaClO 4 .H 2 O) can be added.
• the resulting reaction mixture had the following composition:
• Ammonia gas was then bubbled into this reaction mixture until the pH rose to 6 - 6.5. 580 G. of ammonium nitrate (solid), 58 g. of sodium nitrate and 19 g. of guar gum were mixed and then added to the reaction mixture which was then stirred rapidly at a speed of at least 300 rpm to hydrate the gum. 10 M1. of a saturated solution of potassium pyroantimonate in water (4%) were added together with 58 g. of sulfur. 0.3 G. of sodium nitrite were also added as stabilizer. On vigorously mixing the resulting mixture in a double ribbon blender the density of the mixture fell to 1.05 - 1.10 g./cc.
• the resulting slurry explosive composition at this stage was sufficiently flowable to be packed in polythene tubes of 25 mm. diameter. After a period of 24 to 36 hours the slurry explosive composition set to a firm uniform gel. This gel could be initiated with a No. 6 commercial detonator giving a velocity of detonation of-over 4000m. /sec. and a Trauzl lead block value of 275-300 ml.
• the monomethylamine nitrate content of this slurry explosive composition was 16.5%, whilst the dimethylamine nitrate and trimethylamine nitrate content were respectively 4% and 2%.
• the water content was 10-12% and this explosive composition is a general purpose water gel explosive having a strength of 90% on the Blasting Gelatine scale. It can have a shelf-life of over 2 years even under warm storage conditions. It is sensitive to a No. 6 Detonator at temperatures as low as 5°C, and as high as 45°C.
• Example 2 The explosive composition of Example 2 can be packed in cartridges of 75 mm.and used as an effective column charge in open cast blasting.
• Examples 3 to 7 respectively pass the incendivity tests prescribed for explosives for use in group 1, 2 and 3 gassy coal mines and when fired in a gallery containing 8.3% methane with or without coal dust will conform to the standards prescribed for the respective explosives, thus qualifying for use as permitted explosives in the prescribed category of gassy coal mines.
• a powder explosive was produced by mixing the oxidizer/sensitizer blend produced in the manner described in Example 1 with additional constituents to give a mixture comprising 25% of the above blend, 65% of solid ammonium nitrate, 10% of wood meal, and 0.5% of guar gum.
• the resulting mixture was a powder explosive which in a 25 mm. cartridge had a velocity of detonation of 2400 m./sec.and a Trauzl lead block value of 342 ml., thus constituting a powder explosive of use for general purpose blasting.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Perforating, Stamping-Out Or Severing By Means Other Than Cutting (AREA)

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Citations (5)

• 1980
  • 1980-03-28 AT AT80300973T patent/ATE3630T1/de not_active IP Right Cessation
  • 1980-03-28 EP EP80300973A patent/EP0037862B1/de not_active Expired
  • 1980-03-28 DE DE8080300973T patent/DE3063578D1/de not_active Expired

Patent Citations (5)

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