Spray Drying of Energetic Materials by the Example of Ammonium Nitrate and Ammonium Dinitramide

Spray drying technology is a method of producing high-quality particles from solutions, emulsions or suspensions on an industrial scale. The gentle process is preferably used in the processing of sensitive substances from the food, pharmaceutical and chemical industries. Advantages are in particular the moderate process temperatures and the low mechanical load on the products. Due to the continuous processing, only small quantities of products are in the direct processing zone. These advantages in terms of quality and safety were transferred to the processing of energetic materials through the conception and procurement of a combined spray drying and spray congealing process at Fraunhofer ICT. By varying spray formation, process temperatures, solvents and solids concentrations, product properties such as particle size and morphology can be influenced. The continuous process control offers the possibility of sample production on a 100 g scale up to production on a technical scale of several kilograms per day. For the safe processing of propellants and explosives, the following additional features have been implemented: explosion protection in accordance with ATEX, closed inert gas operation with nitrogen, solvent resistance, solvent recovery, remote control and installation of the process unit in a safety working area. The spray drying plant was applied for two oxidizers used in solid propellants. By the example of phase stabilized ammonium nitrate (PSAN) the feasibility of the process was proofed. The processing of ammonium dinitramide (ADN) showed some well-known challenges. The transferability of this manufacturing technology for particulate products to numerous other oxidizers and explosives is realistic from the technical point of view.