Rock Products

MAR 2017

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Page 59 of 107

58 • ROCK products • March 2017 B lends of ammonium nitrate and emulsion explosives are gaining widespread popularity in today's blasting indus- try because of the water resistance, energy, ease of loading and economical price; however, these explosives do have major set-backs including increased fumes and the large increase in critical diameter of the product. These set-backs can be accommodated with a proper under- standing of the explosive and allow the mine to maintain control over there drilling and blasting program. It should be noted, that from strictly an economic standpoint blends, where no water is present, will cost more per ton of ore pro- duced than an ANFO and should not be substituted unless a detailed economic study has been completed considering both the direct and indirect cost of blends. This article will discuss both the blends (greater percentage of emulsion) and Heavy ANFO (greater percentage of ANFO). Heavy Emulsion Blends A blend is a mixture of emulsion and ammonium nitrate that is cheaper than emulsion yet is still water resistant. A typ- ical blend will have over 50 percent of its total mixture be emulsion by weight with the remainder composing of ammo- nium nitrate or ANFO. These blends can be pumped into blastholes forcing the water upward out of the blastholes. The water resistance increases with the increasing emulsion content, however the explosive power per pound will generally decrease as the emulsion content is increased. This is because emulsion contains water that does not con- tribute energy to the detonation, whereas the ammonium nitrate is directly contributing energy to the detonation. Blends that have a high percentage of emulsion are generally very difficult to distinguish from a normal emulsion (Figures 2 & 3 on page 60). These blends are also notorious for producing high levels of fumes, specifically visible nitrous oxides (NO x ). Currently, from studies conducted by NIOSH it is known that any form of blend or heavy ANFO will produce greater amounts of fumes than straight emulsion or straight ANFO, it is believed this may stem from detonation parameters. However, a major problem with emulsion blends is that typically ammonium FIELD TESTING Field Testing for AN Blend Explosives Blends Of Ammonium Nitrate and Emulsion Explosives are Gaining Widespread Popularity in Today's Blasting Industry. By Anthony Konya and Dr. Calvin J. Konya Figure 1 - Emulsion, 70/30 Blend, 50/50 Blend, 30/70 Heavy ANFO, ANFO (from left to right).

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