湿法磷酸真空过滤系统管线结垢的机理研究

Study on the Mechanism of Scale Deposition in Pipelines of the Vacuum Filtering Apparatus during the Production of Wet-Process Phosphoric Acid The interfacial energy of sodium fluosilicate, potassium fluosilicate and gypsum with phosphoric acid solution are calculated by interfacial energy principle. The nucleation and limited supersaturation of the scale components are investigated in the presence of additives or no by crystallization method. By simulating the cooling process of the vacuum filtration in phosphoric acid production, the scale formation process, the effects of pipe material and additive on the scale formation are studied. Several efficient additives are found. The scale formation mechanism is made clear. The researches show that in the filtration of gypsum, high supersaturation level is reached since the phosphoric acid solution temperature is sharply decreased. The supersaturation level exceeds the limited supersaturation level of sodium fluosilicate and large amounts of sodium fluosilicate segregate out. Some of them are attached on the pipe wall. Because of the similarity of crystal lattice between sodium fluosilicate and potassium fluosilicate, potassium fluosilicate is induced to growth on sodium fluosilicate crystal. The mutual induction between potassium fluosilicate and sodium fluosilicate expedites the scale formation.

本项目将界面能理论与结晶理论相结合用于研究湿法磷酸真空过滤系统管线结垢的形成机理，并找出能阻止结垢的有效方法，由此提出一套研究化学工业中普遍存在的结垢现象的通用方法。本项目的研究将不仅有助于丰富和发展溶液结晶理论，而且还为界面科学增添新内容，同时也使得湖北磷矿的推广和应用成为可能，从而促进我国磷复肥工业的发展。