湿法磷酸中的杂质对二水硫酸钙结晶影响的研究

Effect of Impurities in Wet-process Phosphoric Acid on the Crystallization of Gypsum

用模拟湿法磷酸进行了Ｆｅ２Ｏ３离子、Ａｌ２Ｏ３、Ｈ２ＳｉＦ６和Ｈ２ＳＯ４五种杂质及ＮＨ离子对二硫酸钙结晶影响的实验研究。并以过滤时间表征结晶质量进行了杂质对石膏结晶过程影响的分析。对于ＮＨ离子的影响进行了单因素实验。实验得出，当磷酸杂质含量在平均水平附近时，随湿法磷酸中Ｆｅ、Ａｌ、Ｍｇ杂质含量的增高，都会使二水硫酸钙的过滤性能变坏，其中尤以Ａｌ２Ｏ３的影响最大。但ＮＨ能促使二水硫酸钙生成聚晶，对石膏的过滤性能有改良作用，通过实验可确定出一个最佳ＮＨ浓度。对不同杂质含量的磷酸，其最佳ＮＨ浓度值并不相同。

The effect of NH4 ions and five impurities- Fe2O3,Al2O3,Mgo,H2SO4 and H2SiF6in simulated wet-process phosphoric acid on the crystallization of gypsum was studied experimen-tally in detail,and a mathematical model was obtained by means of variant analyses.From this mod-el,it is peible to estimate the influence of the above impurities in phcophoric acid on filterability ofthe gypsum slurry.The effect of NH4 ions on the gypsum crystallization was studied by way of sin-gle-factor experiment.The experimental result shows that the filterability of gypeum slurry decreases with the concen-trations of Fe3,Al3+and Mg2+increasing in the phosphoric acid,among them,the Al3+plays themost significant role,he presence of NH4 ions in phosphoric acid has a positive influence on the gypsum crytal habit.The optimum concentration of NH4 ions or variant phosphoric acids which contain different amount of impurities is not the same.