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ISMR Technology Transfer Seminar. ANFO & Emulsion Characteristics Heavy Blends as a Tool for Blasters!. What is needed for an explosion?. ANFO. Ammonium Nitrate / Fuel Oil Ammonium Nitrate Production Reaction of anhydrous ammonia gas and concentrated nitric acid.
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ISMRTechnology Transfer Seminar ANFO & Emulsion Characteristics Heavy Blends as a Tool for Blasters!
ANFO • Ammonium Nitrate / Fuel Oil • Ammonium Nitrate Production • Reaction of anhydrous ammonia gas and concentrated nitric acid. • After the reaction the AN solution is about 83% concentration. • Excess water is evaporated off to leave an AN concentration of 95 to 99.9%.
AN Production cont’d • AN Solution is turned into prill. • A small percentage of water is left in the solution when the prill is formed. • When the prill is dried the water is removed and it leaves voids in the prill. • This is where the diesel fuel goes when added to the prill.
ANFO Characteristics • ANFO Density ranges from .82 - .90 g/cc • Oxygen Balanced @ 94.4% AN / 5.6% Fuel • Under fueling leads to: • Greater sensitivity. • Drastic loss of ENERGY! • Orange smoke, inefficient reaction during detonation. • Over fueling leads to: • Loss of Energy.
Effects of Fueling on Fume Production http://www.cdc.gov/niosh/mining/pubs/pdfs/faafp.pdf
Effects of Fueling on Fume Production http://www.cdc.gov/niosh/mining/pubs/pdfs/faafp.pdf
ANFO and VOD • ANFO VOD increases as the borehole diameter increases.
ANFO Characteristics • The critical diameter of poured ANFO is about 2.0 – 2.5 inches. • Under this it will not detonate. • If it is loaded pneumatically the critical diameter can be increased to 1.0 inch. • ANFO is considered a ‘Blasting Agent” • This means it cannot be detonated with a #8 strength detonator when unconfined. • It requires a primer assembly to be initiated.
ANFO Characteristics • When ANFO detonates it does so inefficiently. • This produces excess gases from the reaction. • This is a benefit to blasting due to the rapid expansion of the gases out into the formation creating a “heave” effect. • This heave effect allows for easier digging.
ANFO Characteristics • ANFO is not waterproof or even resistant. • ANFO can deflagrate if a significant amount of water has damaged the ANFO. • ANFO can fail to detonate if water has damaged enough ANFO in the hole. • If the ANFO shoots “low order”, it shoots inefficiently and produces excess gases. • Orange fumes!
Water solutions of oxidizers in an oil medium. (ISEE Blasters Handbook: Chapter 7, page 77.) Emulsion • A mixture of two or more liquids in which one is present as droplets, of microscopic size, distributed throughout the other.
Explosive Emulsion Anatomy • Oil continuous, “external” phase (green) – 5 to 9% • Mineral oils • Diesel fuels • Recycled oils • Vegetable oils • Aqueous salt discontinuous, “internal” phase (blue) – 91 to 95% • Ammonium Nitrate • Calcium Nitrate • Sodium Nitrate • Perchlorates
Bulk Emulsion Characteristics • Typical density of a sensitized emulsion runs about 1.25 g/cc. • Loaded in diameters between 1and 12 inches. • VOD increases with Borehole Diameter. • Sensitivity/density can vary with the addition of microballoons or chemical gassification. • Can be dead pressed when sensitized with microballoons. (Crushing of balloons) • Can be classified as Oxidizer of Blasting Agent.
What are Heavy Blends? • Blends of ANFO and Emulsion
Heavy ANFO Blends • Why utilize blends? • Increase the density of ANFO; hence, increase energy in the borehole • Provide water resistance to ANFO • Reduce mining costs (ISEE Blasters’ Handbook; Chapter 9, page 93.)
Blend Benefits • Longer sleep times with heavy blends. • Water resistance for ANFO in wet formations. • Pattern expansions. • Maximize energy in hole. • Drill cost savings potential. • More production yards per hole. • Less shots per cut.
