铝酸钠溶液晶种分解过程中游离碱对晶体附聚的影响

Effect of free caustic alkali on agglomeration in seeded precipitation of sodium aluminate solution

利用铝酸钠溶液晶种分解过程研究游离碱对晶体附聚的影响,利用NaOH溶液模拟游离碱环境研究AlOOH和Al(OH)3在NaOH溶液中的溶解-结晶性能。结果表明:游离碱对晶体附聚起抑制作用,并且抑制作用随其浓度增加而增强。由于可作为附聚粘结剂的新生细晶粒活性高,而游离碱对高活性晶粒有强烈侵蚀作用,因此晶体附聚受到抑制。晶粒溶解速率随温度、游离碱浓度、转速、晶粒活性的增大而增大。基于溶解-结晶模型并拟合实验数据发现,AlOOH和Al(OH)3在NaOH溶液中的溶解速率正比于游离碱浓度的1次方及晶体表面积的1.5次方。比较AlOOH和Al(OH)3在NaOH溶液和铝酸钠溶液中的溶解-结晶性能可知,铝酸根的存在抑制了游离碱对晶体的侵蚀作用。

The effect of free caustic alkali （FC） on agglomeration of crystal was discussed through seeded precipitation of sodium aluminate solution. By simulating ambience of FC, the dissolution-crystallization performances of AIOOH and AI（OH）3 in NaOH solution were investigated. The results show that the agglomeration is inhibited by FC, and the inhibitory effect becomes stronger with increasing concentration of FC （ρFc）. The crystals that freshly form in sodium aluminate solution can make small particles agglomerate as binder, and is eroded by FC, so the agglomeration of crystal is inhibited. The erosion rate of crystals increases with increasing temperature,ρvc, rotating speed and crystal particle activity. Based on dissolution-crystallization model and experimental data, it is found that the orders of erosion rate with respect to cfc and crystal surface are estimated to be 1 and 1.5, respectively. The erosion of FC is inhibited by aluminate ions, which is obtained by comparing the dissolution-crystallization performances of A1OOH and AI（OH）3 in NaOH solution with those in sodium aluminate solution.