尿素对硫酸钙结晶过程影响的研究

Effects of Urea on the Crystallization of Calcium Sulfate

以试剂磷酸二氢钙、硫酸和尿素为原料,模拟磷矿-硫酸脲(尿素硫酸加合物)反应中的硫酸钙结晶过程, 在MSMPR结晶器中研究了尿素对硫酸钙结晶的影响。结果表明,与无尿素的结晶过程相比,尿素使出现结晶的时间延长了150%,但悬浮液密度增加50%,结晶在长度和宽度上均有所增加,特别是宽度上的增长超过50%。粒度分布的定量分析显示,尿素硫酸摩尔比为 3.6:1、过程温度80℃时, 硫酸钙的成核速率减少了25%,但结晶成长速率增加了1.2倍,结晶粒度分布中心由72.8mm 增大到 142.8mm,平均粒径由70.98mm 增加为 105.45mm 。两者叠加的结果体现为硫酸钙结晶过程总速率的增加。

The influence of urea on the crystallization of calcium sulfate was studied in a MSMPR crystallizer. Mono-calcium phosphate, sulfuric acid(SA) and urea were used for simulating the crystallization of calcium sulfate in the reaction of phosphate rock and urea-sulfuric acid. The results indicate that, comparing with the crystallization without urea, the time of crystal occurrence is 1.5 times longer, the density of suspensoid is raised by 50%, both of crystal length and crystal width are increased, especially, the increment in crystal width is more than 50%. Based on quantitative analysis and calculation for the granularity distribution, in the crystallization with 3.6:1 of urea-SA ratio at 80℃, the nucleation rate is reduced by 25%, the crystal growth rate increases by 120%, the distribution center of crystal size moves from 72.8mm to 142.8mm, the crystal mean size changes from 70.98mm to 105.45mm. The total rate of the crystallization is increased due to the combining effect of the changes in above two rates.