用超临界流体反溶剂过程改性包覆硝酸铵

Modifing Coated Ammonium Nitrate by Using Supercritical Fluid Anti-solvent Process

为了降低硝酸铵（AN）的吸湿性并提高其流散性,采用超临界流体反溶剂过程对其表面进行改性包覆,以硝化棉为包覆材料、丙酮为共溶剂、超临界CO2为反溶剂,研究了体系温度、压力和萃取速率对包覆效果的影响。对包覆后样品的吸湿性进行了测定和SEM分析。结果表明,体系温度是影响包覆效果的最关键因素,其次为压力和萃取速率,当体系温度为31℃、操作压力为10M Pa、萃取速率为10-15 kg/h、硝化棉的质量分数1%时,包覆后AN的吸湿性明显改善,吸湿率降低约50%（12 h）无结块现象,流散性显著提高。

In order to decrease the hygroscopicity of AN and enhance the fluid and disperse properties of AN, supercritical fluid anti-solvent process is used in ammonium nitrate coating in which nitrocellulose is chosen as covering material, acetone as cosolvent and CO2 as anti-solvent, respectively. The influence of temperature, pressure and speed of extraction for the system on the coating effect is investigated. The hygroscopicity of coated samples is measured. The coated samples is analyzed by SEM. The results show that the temperature in the process is the key factor affecting the coating quality. The pressure and speed of CO2 also have some effect. The optimum conditions of the process are： temperature, 31℃, pressure, 10MPa, CO2 release rate, 10-15 kg/h,and the mass fraction of nitrocellulose, 1%. The hygroscopicity and fluid and disperse properties of coated ammonium nitrate are improved obviously.