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Abstract

Explosive grade ammonium nitrate (EGAN) prills are made by a process comprising the steps of: a. continuously spraying a 95 to 98% by weight solution/melt of ammonium nitrate (or a mixture of ammonium nitrate and minor proportions of one or more other EGAN--acceptable nitrates) in/with water under spray-head conditions causing the emergent jets to break into cascades of substantially mono-sized droplets; b. allowing the formed droplets to fall within a vertical duct; c. continuously feeding a stream of cooling gas upwards through the duct to effect cooling and solidification of the falling droplets and some removal of moisture so as to form substantially mono-sized EGAN prills of up to about 4 mm diameter, and d. continuously withdrawing the EGAN prills collecting at the base of the duct (such EGAN prills then optionally being further cooled and/or dried in a forced draught regime), the process also involving intensification of the upward gas flow regime in the duct such that: (i) the temperature difference of the gas flow between its inlet to the duct and its outlet from the duct is at least about 60.degree. C.; and (ii) the falling velocity of the prills in the duct is at most about 3 meters/second relative to ground (i.e. a stationary observer external to the duct) the upward gas flow velocity being e.g. 6 m/s relative to ground for 2 mm prill and 9 m/s for 3 mm prill and, optionally, (iii) recycling the gas stream after washing and cooling and addition of any required make-up gas.

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