磷矿酸解过程杂质原位萃取分离及三相体系硫酸钙结晶调控

中低品位磷矿湿法磷酸过程产生大量的二水磷石膏，晶型稳定、杂质和夹带磷酸含量较高导致难以有效利用，大量堆存造成长江中上游地区生态环境的严重污染。目前湿法磷酸过程研究着重于半水-二水等新工艺的开发，但均存在杂质含量高影响硫酸钙晶型调控和工艺稳定性问题。基于此，本项目提出在磷矿酸解过程，进行镁、铁、铝等关键杂质的萃取分离，实现杂质从酸解体系中的定向快速脱除，降低杂质对晶体生长抑制作用，避免被晶体包裹进入磷石膏；结合除杂后酸性体系下硫酸钙晶体的可控生长，减少因过滤洗涤困难造成的磷夹带问题，实现磷石膏的品质提升和资源化利用。通过磷矿酸解过程杂质释放转化、酸解-萃取过程的界面化学、固液液三相体系下的硫酸钙物相形貌及应用构效调控、分离结晶一体化装备的结构优化等方面的重点研究，形成强酸性三相体系下杂质萃取分离耦合结晶调控新工艺原型，为中低品位磷矿的大规模利用和磷石膏的高品质资源化提供了理论和技术支撑。

Large amounts of dihydrate phosgypsum are generated in the process of wet phosphoric acid with medium or low grade phosphate ore. They are difficult to be effectively used because of the stable phase, high amounts of impurities and phosphoric acid entrainment. The accumulation of phosphogypsum causes serious damage to the environment in the middle and upper regions of the Yangtze river. Current researches mainly focus on the development of dehydrate-hemihydrate new process, but the process is usually affected by the impurities to control the phase of calcium sulfate and the stability of the process. In view of the above problems, this application proposes to separate the impurities such as silicon, iron, and aluminum from the solid-liquid system by extraction in the acidolysis process of phosphate ore. This method could reduce the influence of impurities on the crystallization of calcium sulfate. Meanwhile, the entrainment of phosphorus can be diminished through the controllable growth of the crystal, which is beneficial for the separation of phosphoric acid, so as to realize the quality improvement and utilization of phosphogypsum. The emphasis is on the controllable transformation of impurities from phosphate ore, the functional structure screening and design of extraction agent binding with the impurities, the phase and morphology change of calcium sulfate with the existence of mixed acid and multiple impurities, the relationship between structure and application performance of phosphogypsum, and the optimization of reaction and separation equipment. Then the whole process of acidolysis coupling impurity extraction separation may be built. These researches may be the basis to establish the system of controlled decomposition of phosphate rock in the three-phase system, crystallization control of calcium sulfate, functional structure design of extraction agent, and in situ separation of impurities. The results may provide a key technical support for the coupling for the large-scale application of low and medium grade phosphate rocks and controllable preparation of high quality phosphogypsum products.