Study On The Preparation Process Of Ultrafine Phase Stable Ammonium Nitrate

The phase-stable ammonium nitrate has the characteristics of high crystallizing temperature,high gas production rate,low price,and no hydrogen chloride in the combustion products.So,it meets the requirements as an oxidant in the gas generating agent.Phase-stabilized ammonium nitrate with different particle size gradations can increase the loading density and energy density of gas generating agents.It has been found that ultrafine oxidant particles can improve the combustion performance of gas generating agents.However,ultrafine-phase stable ammonium nitrate has a large specific surface area,high surface energy,and easy hygroscopic agglomeration.Therefore,through the analysis and comparison of experimental methods for preparing ultrafine particles at home and abroad,the experimental scheme of toluene-ethanol-water emulsion system was designed,and the preparation and surface modification experiments of ultrafine-phase stable ammonium nitrate were carried outFirstly,the influence of the cooling mode and the amount of phase stabilizer were discussed.At the same time,a experiment was conducted to study the effects of emulsification temperature,crystallization temperature,stirring rate,ratio of water to ethanol,and ammonium nitrate concentration on particle size,particle size distribution,and yield of phase-stable ammonium nitrate.The experimental results show that when the instantaneous cooling method was selected and the amount of phase stabilizer was 2.8%,the ?(?)? phase transition of ammonium nitrate disappears,the phase transition of ?(?)? phase delays,and the crystal phase transition of ammonium nitrate was suppressed.In addition,the single-factor experimental results show that the average particle size of phase-stabilized ammonium nitrate first decreases and then increases with the increase of the emulsification temperature,while the yield increases;the average particle size of the phase-stable ammonium nitrate increases with the crystallization temperature and the yield decreases with the increase of the crystallization temperature;the average particle size of the phase-stable ammonium nitrate decreases with the increase of the rotation speed,and the yield is not affected by the rotation speed.The average particle size of phase-stable ammonium nitrate decreases with the decrease of the ratio of water to ethanol,and the yield is not affected by the ratio of water to ethanol;the average particle size of phase-stable ammonium nitrate increases with the concentration of ammonium nitrate.While the yield increases.When the emulsification temperature is 60?,the devitrification temperature is 15?,the stirring rate is 220 r/min,the ratio of water to ethanol is 1:8,and the ammonium nitrate concentration is 0.042 mmol/L,the phase-stable ammonium nitrate product has the smallest particle size.Then,the five-factor four-level orthogonal test and the three-factor two-level orthogonal experiment were used to optimize the preparation conditions of the ultrafine phase-stabilized ammonium nitrate.The experimental results show that with the increase of the emulsification temperature,the decrease of the crystallization temperature and the increase of the ammonium nitrate concentration,the yield of the ultrafine phase-stabilized ammonium nitrate increases.The stirring rate and the ratio of water to ethanol have little effect on the sample yield.The order of the factors affecting the yield of ultrafine-phase stabilized ammonium nitrate is:ammonium nitrate concentration>emulsification temperature>crystallisation temperature>ratio of water to ethanol>stirring rate.In addition,the experimental results also show that the ratio of water to ethanol has the greatest impact on the particle size distribution,followed by ammonium nitrate concentration and emulsification temperature,and the precipitation temperature and agitation rate have the weakest influence on the index particle size.The influence of each factor on the particle size of phase-stable ammonium nitrate was the ratio of water to ethanol>ammonium nitrate concentration>emulsification temperature>crystallization temperature>stirring rate.In addition,experiments have found that for the yield index,the emulsification temperature and the ammonium nitrate concentration correlate.For the particle size distribution index,the effects of water-ethanol ratio and emulsification temperature on the particle size distribution of phase-stable ammonium nitrate are related.Based on the above orthogonal experimental results,the optimal process conditions for preparing ultrafine-phase stable ammonium nitrate were summarized as follows:emulsification temperature of 60?,crystallization temperature of 2°C.,stirring rate of 200 r/min,and water.The ethanol ratio was 1:6 and the ammonium nitrate concentration was 0.040 mmol/L.Finally,surfactants are used to reduce the hygroscopicity of the ultra-fine phase stabilized ammonium nitrate.The use of toluene-ethanol-water-microemulsion system to modify the ultrafine phase stable ammonium nitrate.The influence of different surfactants and the additive amount of surfactant on the anti-caking of phase stabilized ammonium nitrate are studied.The results show that hexadecyl trimethyl ammonium bromide as surfactant is suitable to prepare anti-caking phase stabilized ammonium nitrate.When the additive of hexadecyl trimethyl ammonium bromide is 1%,the final moisture absorption rate is 7.78%,the maximum compression load is reduced by 37.01%,surface tension is 42.9°,the oil absorption rate is 6.09%,the repose angle is 33.09°,the loose density is 0.75g/mL,the compaction density is 0.86g/mL,and the purity is 96.56%.The results of electron microscope test also show that the surface of the modified sample is more smooth.Through the above studies,the optimized process conditions for preparing ultra-fine phase stable ammonium nitrate and the optimal additive amount of modified ultrafine phase stabilized ammonium nitrate were obtained.This provides a new approach for the refinement of ultrafine-phase stable ammonium nitrate and also provides the necessary theoretical basis and technical support for the development of gas generating agents.In addition,it also contributes to the preparation and modification of other industrial ultrafine-phase stable ammonium nitrate.