微观混和问题的研究——(Ⅴ)混和对沉淀反应过程的影响

STUDIES ON MICROMIXING(Ⅴ)Effect of Mixing on Precipitation

以硫酸钡沉淀反应为工作体系,研究了在搅拌釜中搅拌强度、粘度、加料时间、反应物初始浓度及反应物初始体积比等各种操作参数对产物晶体粒度分布的影响。发现:搅拌强度、粘度以及加料时间对粒度分布的影响不是单调的,均各自存在极小值点,在极小值临界点处平均粒径或方差(或变异系数)取值最小;平均粒径取值最小处的临界点与方差(或变异系数)取值最小处的临界点并不相重而稍有偏离,但在两个临界点所围的操作区内,粒子细而且分布均匀,所以此区为最佳操作区,这一结果对液相法超细粒子的制备而言显得极为重要。

The effects of stirrer speed,viscosity,feed-time,initial concentration and volume ratio of reactants on crystal size distribution(CSD)during precipitation conducted in a semi-batch stirred tank were investigated and analysed.It was found that there exist critical points of stirrer speed, viscosity and feed-time,at which(i.e.u_(crit),μ_(crit) and t_(f,crit)),the mean size and the variance of CSD are minimal.This critical phenomenon is contributed to the interaction of micromixing and macromixing and is vital to industries such as the manufacturing of ultro fine particles and catalysts.