胶磷矿中杂质赋存形式及酸解过程变化

Occurrence of the Impurities in Phosphorus Rock and the Research of Acidolysis Process

我国中低品位胶磷矿量大、分布广,磷矿中杂质种类及含量对于磷石膏结晶及磷酸品质均有较大影响。以湖北某地区的典型低品位胶磷矿为原料,采用X射线光电子能谱仪、扫描电镜、能谱等方法,分析了磷矿及反应后磷石膏中的主要杂质种类及含量变化,并以此推测湿法磷酸过程中杂质的主要变化。结果表明磷矿中的主要成分是氟磷灰石和石英,杂质组分占比最高的分别是硅、铝、氟、镁,其中硅主要以石英和硅酸钙存在,氟主要存在于氟磷酸钙中,铝是以不同形式的铝硅酸盐存在的,而镁则是以MgF_2和部分硅酸盐存在。通过酸解反应,钙与硫酸根生成磷石膏,硅元素主要存在于固相石膏中,而铝、氟、镁则大部分进入到液相磷酸中,其中存在于固相中的硅则基本以石英形式存在,硅酸钙溶解于酸液中,铝主要以铝硅磷的化合物存在,氟则以氟硅化物形式存在,大部分的MgF_2溶解进入液相,磷石膏中镁主要以镁硅酸盐形式存在。通过磷矿中杂质存在形式及反应过程的变化研究,可以更好的明晰酸解过程中的体系变化,从而为磷石膏结晶过程的考察和控制提供理论基础。

In the process of wet-process phosphoric acid, the impurities in the mineral have great effects on the crystallization of calcium sulfate and restrict the utilization of phosphogypsum. Choosing the typical low-grade phosphorus rock in Hubei province of China as the material, the types and contents of main impurities in phosphorus rock and phosphogypsum have been analyzed through X-ray photoelectron spectroscopy, scanning electron microscopy, and EDS. The main changes of the impurities have been evolved in wet-process phosphoric acid. The results show that fluorapatite and quartz are the main phases in phosphorus rock. The highest impurity components are silicon, aluminum, fluorine, and magnesium. Silicon exists in silica and calcium silicate, and fluorine is all in fluorapatite, and aluminum exists in different kinds of aluminosilicate, and most of magnesium exists as MgF2. Calcium reacts with sulfuric acid to form gypsum through acidolysis reaction. Silicon mainly remains in solid phase. Most of aluminum, fluorine, and magnesium decompose into liquid phosphoric acid. Silica still remains in phosphogypsum, and calcium silicate dissolves in acid solution. The compound comprised of aluminum, silicon and phosphorus forms in acidolysis process. Fluorine is mainly in silicofluoride. Most of MgF2 dissolve into solution, and remaining part of Mg in phosphogypsum mainly exists as magnesium silicate. Through the research of occurrence of impurities, the system change may be better acknowledged in the process, and it can provide a basis for the investigation and control of phosphogypsum crystallization.