Precipitation of fine single crystal of sparingly soluble salt

在308K的间歇搅拌釜中，对硝酸铅溶液与硫酸反应得到的硫酸铅进行了沉淀试验，研究了铅离子浓度的下降速率与硫酸铅结晶大小分布的关系。在过饱和溶液中获得了相对均匀大小的晶体，其浓度以与过饱和成正比的速率下降。在这些试验中，分别制备的溶液被一次混合，并且在饲料初始阶段的混合条件影响了粒度分布的均匀性。在一些测试中，尺寸分布变得广泛。其他试验也在两升体积的CDJ（受控双射流）结晶器中进行，该结晶器设计用于使两种溶液混合良好。在这些试验中，硝酸铅或硫酸钠的水溶液分别通过单独的管道进入结晶器中的混合明胶溶液中，并发生反应。为了获得所需尺寸的均匀晶体，这些试验在操作中分批进行，其条件选择使成核在初始阶段发生并在短时间内完成。在接下来的步骤中，出生的核被期望生长到理想尺寸的晶体而不成核。主要操作条件为：硝酸铅料液浓度为0.10mol/l，硫酸钠料液浓度为0.10mol/l。溶液进料速度为10ml/min，结晶器内醋酸和明胶混合溶液浓度为1.74 × 10^<-1>mol/l，初始浓度为2wt%。在pPb或PS04上，工作溶液的过量浓度为2或3，在pPb过量条件下，可以得到平均尺寸和价系数为4.5um，约为15%的菱形晶体。

Precipitaion tests of lead sulfate in a solution obtained by reaction between lead nitrate solution and sulfuric acid, were carried out in a batch agitated vessel at 308K, and a correlation between a decreasing rate of a concentration of lead ion and a size distribution of lead sulfate crystals grown, was studied. A relatively uniform size crystal was obtained in the supersaturated solution whose concentration decreased on the rate proportional to a supersaturation. On these tests, the solutions prepared separately, were mixed at one time and a uniformity of size distribution was affected by a mixing condition on initial stage of feed. On some tests, a size distribution became broad.Other tests were also done in the CDJ (Controlled Double-Jet) crystallizer of two liters on volume which was devised to make two solutions mixed well. On these tests, an aqueous solution of lead nitrate or sodium sulfate was separately fed into an mixed gelatin solution in the crystallizer through an individual pipe, and reacted. In order to obtain homogeneous desired size crystals, these tests was batchwisely carried out in the operation whose conditions were selected to make nucleation occurred on an initial stage and finished in a short period. On the following step, born nuclei were expected to grow to a desired size crystals without nucleation. The main operational conditions were as following : Concentration of feed solution of lead nitrate or sodium sulfate was 0.10mol/l, respectively. Feed rates of solutions were 10ml/min, the concentration of acetic acid and gelatin in a mixed solution in the crystallizer were 1.74x10^<-1>mol/l, and 2wt%, on initial stage. An excess concentration of operating solution was 2 or 3, on pPb or PS04, and lozenge- shape crystals whose average size and coefficient of valience were 4.5um and about 15 percent, were obtained on the operational condition of 2 on the excess of pPb.