Study On The Recycling And Particle Size Controlling Of AP From Retired Composite Propellant

As a kind of special energetic materials, the retired composite solid propellants can still combustion or explosion, and it must be treated safely and properly. In the work, the way to recycle ammonium perchlorate (AP) in the retired propellants was studied. AP was extracted from the propellant and purified by using water as solvent. The particle size of AP was optimized by methods of recrystallization and freeze dehydration.Firstly, with water as the solvent, the technology of extraction and purification of AP from the propellant was studied. The results showed that the recovery rate of AP can reach up to86%with the optimized extraction conditions, and the purity can attains the military standard requirements after recrystallization3times. Where, the optimum extraction parameters are:extraction temperature80℃, ratio of liquid and propellant5:1, extraction time6h. The optimum extraction parameters are:recrystallization up to3times.Secondly, the effects of recrystallization on the particle size of AP were investigated. The results showed that:the crystallization time, cooling rate, agitation rate and blade shape can affect the particle size of AP. The average particle size of AP can be limited from35.2μm to136.1μm by controlling the process conditions. The most significant factor accounting for the particle size of AP is cooling rate, increase the cooling rate can reduce the particle size. When up to10min, the crystallization time has no apparently on the particle size. To increase the stirring rate and take Y-shaped blade of agitator can reduce the particle size.Finally, superfine particle of AP was prepared by method of freeze dehydration. Direct freeze-drying and spray freeze-drying was take d in the work. The results showed that:the optimized process conditions of direct freeze-drying are:temperature50℃, concentration of AP0.1mol·L-1, and the smallest average particle size of AP is3.3μm. The optimized process conditions of spray freeze-drying is concentration of AP0.1mol·L-1,pressure0.6Mpa and nozzle distance15cm, and the smallest average particle size of AP is4.9μm.