Explosive and thermic compositions or charges – Containing inorganic nitrogen-oxygen salt – Ammonium nitrate
Patent
1994-01-21
1996-04-09
Mai, Ngoclan
Explosive and thermic compositions or charges
Containing inorganic nitrogen-oxygen salt
Ammonium nitrate
1491096, C06B 3128
Patent
active
055058000
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to explosives in general, and in particular to modified forms of high shock explosives used in rock blasting situations. The modified explosives are so called low shock energy explosives (LSEE). More particularly, the present invention relates to low shock energy explosives for use in rock or mineral blasting situations and to methods of mining using such explosives. Even more particularly, though not exclusively, the present invention relates to the manufacture and use of chemically modified forms of Ammonium Nitrate Fuel Oil (ANFO) explosives which have been modified, preferably by the incorporation of a slower reacting solid fuel material, for delaying the time taken for the development of the maximum amount of energy of the explosive.
Although the present invention will be described with particular reference to the use of modified ANFO explosives in rock blasting, it is to be noted that the present invention is not limited to the production and use of this type of explosive, but rather the scope of the present invention is more extensive so as to also include materials, modifications and uses other than those specifically described. For example, the present invention is equally applicable to the so called heavy or high-density ANFO/EMULSION high shock energy explosive. The modification of heavy ANFO/EMULSION explosive by the incorporation of a solid fuel material can produce a similar shift in the energy balance to create a LSEE.
BACKGROUND TO THE INVENTION
Explosives currently being used in rock blasting situations are generally high shock energy explosives in which all of the explosive energy and the attendant high-pressure gases are generated more or less instantaneously. A typical example of such an explosive which is currently used is ANFO which is a mixture of ammonium nitrate (AN) and vegetable and mineral oils with flash point greater than 140.degree. F., typically diesel oil No.2 (FO). The use of ANFO explosives in many blasting situations results in a number of disadvantages which include the following: energy. At detonation there is a sudden increase of pressure that displaces the blasthole wall, generating a strain, or shock, wave that produces cracks in the rock. The energy in this wave is the shock energy. After the shock wave has propagated through the rock, the hot pressurised gas which is left in the blasthole is able to extend the cracks as well as to heave the burden. The gas has an energy content called the heave energy. Before blasting, rock generally contains sufficient fractures that can be propagated by the heave energy alone. Thus the shock energy serves little or no useful purpose in fractured rock. For ANFO 94/6 (94% Ammonium Nitrate/6% Fuel Oil), the total energy theoretically available is 3727 J/g, which comprises 1241 J/g shock energy, 2255 J/g heave energy and 231 J/g of residual energy, where the residual energy is the internal energy of the gas itself and cannot be utilised. proportion of fine rock particles (fines) are produced by the shock wave crushing the rock located in close proximity to the borehole more than is desirable or is required, such as for example, for use in further processing steps. diamonds which are to be extracted from the rock are sometimes damaged by the crushing of diamond bearing rock caused by the shock wave, particularly in locations close to the blasthole.
It is thought that the development of a low shock energy explosive in which more of the energy of the explosive is generated as heave energy and less as shock energy, and where the energy is more gradually released, may alleviate at least some of the problems associated with the use of conventional high shock energy explosives. Therefore, it is an aim of the present invention to provide a modified explosive, particularly a modified high shock energy explosive which is useful in blasting, in which the production of shock energy is reduced somewhat when compared to conventional blasting explosives.
Previous attempts to produce a LSEE i
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Gribble David P.
Harries Gwyn
Lye Gary N.
Chi Anthony R.
Mai Ngoclan
Technological Resources Pty Ltd.
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