结晶助剂在铝酸钠溶液种分过程中的作用机理

Mechanism of crystal growth modifier in bayer seeded precipitation process of sodium aluminate solution

为了了解结晶助剂(CGM)在铝酸钠溶液种分过程中的作用机理,研究CGM对二次成核和附聚过程的影响。通过对粒度分布及扫描电镜(SEM)照片的对比,探讨CGM对分解过程的影响。研究结果表明:在二次成核过程中,添加微量CGM的溶液中一开始会形成大量的二次成核,但是,这些二次成核细粒子会被立即吸附到晶种表面或者快速附聚而形成大孔隙的聚合体,从而使得二次成核的细粒子数量减少;在附聚过程中,添加微量CGM有助于提高附聚阶段的黏结过程,形成结实的块状六角几何形状的附聚体;添加CGM可以有效地减少磨损时颗粒的破裂,从而形成完全黏结的附聚物。

In order to understand the mechanism of crystal growth modifier（CGM） in Bayer seeded precipitation process of sodium aluminate solution better,the effects of CGM on the secondary nucleation and agglomeration process were studied.The effects of CGM on seeded precipitation process were researched by the analysis of particle size distribution and scanning electron microscope（SEM）.The results show that in the process of secondary nucleation,a large number of secondary nuclei form initially when the CGM is added into sodium aluminate solution,and these nuclei immediately are either adsorbed back on the seed surface or rapidly agglomerated with each other to form aggregates with a high porosity,so the number of secondary nuclei decreases.In the process of agglomeration,the action of the CGM additive aids the cementation process during agglomeration,and in terms of attrition the additive appears to successfully reduce the breakdown of particles,and form a fully cemented agglomerate.