Explosives emulsions

Water-in-od emulsion explosives have been made as typified by a formulation containing 20% water, 12% oil, 2% microspheres, 1% emulsifier, and 65% ammonium nitrate. The micro droplets of an emulsion explosive offer the advantage of intimate contact between fuel and oxidizer, and tend to equal or outperform conventional water-based slurries. 

Inorganic oxidizers are widely used as blasting agents in mining and construction explosives and also in improvised explosive devices utilized by terrorists. Ammonium-nitrate-based explosives (e.g., ammonium nitrate and fuel oil — ANFO) have almost completely replaced the majority of dynamites. In addition, slurry and emulsion explosives, which contain mosdy ammonium nitrate and a small amount of other oxidizers, have become widely used. 

Being partly aqueous, slurry explosives are not inactivated by water or humidity, and they are essentially insensitive to mechanical shock or heat. The strength of detonation is approximately equal to that of NG-NC-based explosives. Since slurry explosives are composed of a mixture of aqueous AN and an oil, they exist as emulsions and hence are also termed emulsion explosives. 

A mixture of AN and water forms a low-strength explosive referred to as a slurry or emulsion explosive. Since a mixture of AN and water cannot be detonated by initiation with a moderate detonation strength, to formulate practical slurry explosives nitrate esters such as monomethylamine nitrate, ethylene glycol mononitrate, or ethylamine mononitrate in conjunction with aluminum powder are added as sensitizers that facilitate the initiation of detonation. 

The major chemical components of emulsion explosives are fundamentally the same as those of slurry explosives, as shown in Table 9.4.[i l Instead of the sensitizers used for slurry explosives, a large number of hollow microspheres made of glass or plastics are incorporated to formulate emulsion explosives in order to obtain successive detonation propagation after the initiation of detonation. During detonation propagation into the interior of the explosives, an adiabatic compression results... 

Table 9.4 Typical chemical ingredients of slurry and emulsion explosives (mass %).

Kato, Y, Takahashi, K., Torii, A., Kurokawa, K., and Hattori, K., Underwater Explosion of Aluminized Emulsion Explosives, Energetic Materials, 30th International Annual Conference of ICT, 1999. 

EDDN EDT EGDN Emulsion explosive Ethylenediamine dinitrate N,N -di-2-Ethanolethylenediamine tetranitrate Nitroglycol, Ethylene glycol dinitrate... 

Secondary high explosive. Used in commercial Emulsion explosive... 

Civil explosives are further sub-divided into permitted or permissible explosives and non-permitted explosives. Two types of civil explosives namely ammonium nitrate-fuel oil (ANFO) and emulsion explosives dominate the rock blasting scene in the USA. 

Emulsion explosives Water in oil with oxidizers like nitrates ... 

An important group within the ammonium nitrate explosives are emulsion explosives, which consist essentially of a water-in-oil emulsion of an aqueous solution, supersaturated at room temperature, in an oil matrix which is a fuel. The oil phase is the continuous phase and includes small droplets of the supersaturated solution of the oxidizing agent. 

The intimate mixing of oxidizer and fuel in emulsions give these explosives much higher detonation velocities when compared to ANFO. For example, in 150 mm diameter PVC ANFO has a velocity of about 4000 m/sec, and a sensitized emulsion would have a velocity closer to 6000 m/sec at a density of 1.20-1.25 g/cc. Also, the layer of oil surrounding each oxidizer solution droplet protects the emulsion from extraneous water intrusion and subsequent deterioration of the explosive. Many studies have shown that when mining operations use emulsion explosives rather than ANFO, which has basically no water resistance, the amount of nitrate salts in mine ground water is reduced considerably. This can be a very important factor in today s environmentally conscious mining and explosives industry. 

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