摘要
采用模拟湿法磷酸生产方式,通过控制萃取反应工艺条件来控制磷石膏晶形.采用扫描电子显微镜观察晶体形貌,采用激光粒度分析仪测定粒度分布和平均粒径.结果表明:液相中游离的H2SO4含量和P2O5含量对磷石膏的晶体形貌和大小都有影响,前者提高,二水石膏析晶过饱和度降低,磷石膏晶体由薄片状变为粗大的柱状和斜方六面晶体,然后再向聚晶转变,平均粒径变大;后者提高,二水石膏析晶过饱和度升高,晶体由粗大的板状变为柱状,然后再向细针状转变,平均粒径变小.反应温度升高,二水石膏析晶过饱和度降低,晶体尺寸变大,但晶体形状基本不变,均为柱状.从兼顾湿法磷酸生产和磷石膏建材资源化的角度出发,提出优化的萃取反应工艺条件为:液相游离H2SO4质量分数为5%,液相P2O5质量分数为15%～20%,反应温度为80℃,料浆液固比为2.5∶1(质量比).
Crystal shape of phosphogypsum was controlled under simulated extraction reaction conditions of wet-process phosphoric acid production. The crystal shape of phosphogypsum was observed using scanning electron microscopy, the crystal size distribution and average particle size were determined by laser particle size analyzer. The results show that the contents of free H2 SO4 and P2O5 in liquid phase affect both crystal shape and crystal size. When the former increases, the crystallization supersaturation of dihydrate gypsum decreases; the crystal shape changes from thin sheet into thick cylinder and rhombic, then changes to poly- crystal; the average crystal size becomes larger. When the latter increases, the crystallization supersatura- tion of dihydrate gypsum increases; the crystal shape changes from thick plate into thick columnar, then changes to thin needle; the average crystal size becomes smaller; when the reaction temperature increases, the crystallization supersaturation of dihydrate gypsum decreases; the average crystal size becomes larger, hut the crystal shape is the same, which is cylinder. From the points of wet phosphoric acid production and utilization of phosphogypsum in building materials, the optimal extraction reaction conditions are proposed as follows.the content of free H2 SO4 in liquid phase at 5 % （by mass）, the content of P2O5 in liquid phase at 15% to 20%（by mass）, reaction temperature at about 80 ℃ and the liquid to solid ratio of slurry is 2.5 ： 1.
出处
《建筑材料学报》
EI
CAS
CSCD
北大核心
2013年第1期147-152,共6页
Journal of Building Materials
基金
国家自然科学基金资助项目(50872160)
关键词
湿法磷酸
萃取工艺
晶形
过饱和度
wet-process phosphoric acid
extraction process
crystal shape
degree of supersaturation
