Stabilizing ammonium nitrate against crystalline change

Abstract

Ammonium nitrate undergoes volume expansion and contraction as it passes through its crystal transition temperatures, causing prills and granules to break down into fine particles or dust. The effect of various chemical additives on the physical breakdown at the transition temperatures has been studied. A mixture of boric acid, diammonium phosphate, and ammonium sulfate was found to be the most effective for stabilizing ammonium nitrate against physical breakdown as ammonium nitrate cycles through its transition temperatures. A commercially proved process has been developed for producing greatly improved granular and prilled ammonium nitrate, and mixed fertilizers containing ammonium nitrate.

Reducing the Explosion Sensitivity of Ammonium Nitrate Fertilizer

“…It has been demonstrated that Mg(NOs)2 (which is extremely hygroscopic) and A^ISO^a re inhomogeneously dispersed in AN and are effective as phase stabilizers only until the water content of the AN prill exceeds the capacity of those desiccants (Sjolin, 1971). It has also been demonstrated (Hansen and Berthold, 1972;Hansen, 1974) that AN prills, phase-stabilized with Mg(NOs)2 or borate/phosphate/sulfate (Brown et al, 1968a(Brown et al, ,b, 1967 (which presumably is similarly inhomogeneously dispersed) are susceptible to destabilization by a little water, as revealed by the detonability investigation mentioned above. Explosion sensitivity of ammonium nitrate is increased by the increased porosity produced by cycling through the 32 °C phase change.…”

Minol IV, A New Explosive Composition Containing Ammonium Nitrate-Potassium Nitrate Solid Solution. Part 1

“…Methods reported in the literature for the stabilization of AN include the addition of potassium nitrate (8,9,10), magnesium nitrate (11), nucleating agents (12), and a mixture of boric acid, diammonium phosphate, and ammonium sulfate (13). Potassium nitrate (KN) is said to lower the 320C transition about 6 0 C for each percent added (8), while magnesium nitrate raises the transition to 55*C and stabilizes it there.…”

“…Potassium nitrate (KN) is said to lower the 320C transition about 6 0 C for each percent added (8), while magnesium nitrate raises the transition to 55*C and stabilizes it there. By the use of small quantities of a mixture of three ingredients, Brown, et al, (13) claim to have changed the 320C transition temperature to 43 to 450C.…”