【摘要】 为从热力学和流体力学角度对SAS法制备硝酸铝纳米球形微粒的过程进行综合分析,通过实验方法研究了温度为32~52℃、压力为8~24 MPa以及CO2流率为30.0~45.0 g·min-1范围内形成硝酸铝纳米微粒的粒径和形貌规律。结果表明,温度升高纳米微粒的球形度有所下降,粒径先减小后增大,温度达到48℃后,制得的颗粒黏结团聚现象加剧;随着压力的升高,粒径先减小后增大,16 MPa时粒径最小;随着CO2流量的升高,粒径不断增大。针对实验结果,采用CFD方法开展了SAS釜内流场特性的模拟研究。通过模拟得到的有效扩散因子Deff随温度、压力和CO2流率的变化规律解释了实验结果,Deff综合反映了釜内热力学和流体力学变化。CFD模型中,湍动模型选择Realizable k-ε方程。研究结果对实现SAS法制备颗粒的形貌和粒径可控化具有重要的理论意义和实用价值,对其他物系的SAS过程同样具有借鉴意义。更多还原

【Abstract】 This paper investigated the preparation of Al( NO3)3spherical nano-particles with the supercritical antisolvent( SAS). At first experiments were carried out at temperature from 32 ℃ to 52 ℃,pressure from 8 MPa to 24 MPa,and CO2 flow rate from 30. 0 g·min- 1to 45. 0 g·min- 1in order to investigate their effect on the morphology and particle size( PS). The results showed that morphology of the nano-particles changed from spherical to non-spherical,and particle size decreased first and then increased with the increasing of temperature. Particles agglomeration became severe at 48 ℃. When pressure increased,particle size decreased at first and then increased. Particle size reached the minimum at16 MPa. The particle size exhibited a positive correlation with the CO2 mass flow rate. The effecting mechanism of above factors was explored with CFD and was explained by the effective coefficient distribution in the precipitator. The CFD model for the injection in the precipitator is developed with the Realizable k-ε turbulent model. Deffreflects both the changes of the thermodynamics and hydrodynamics of the system. The result is significant to precipitate particles with controllable particle size and morphology.Some of the above results can also be applied to other systems and can help to optimize the parameters.更多还原