Study On Process Of Magnesium Removal Of Low And Medium-grade Phosphate Ores By Acid Drainage And Wet-process Phosphoric Acid Production

With the large domestic reserves of phosphate ores, however, more of them are low and medium-grade phosphate ores which have high contents of impurities. The wet-process phosphoric acid production (WPA) is deteriorated severely by medium/low-grade phosphate ores and the phosphorus industry is also restricted by those both on technical and economic aspects. For coping with above problems, the new process of magnesium removal of phosphate ores with acid drainage and wet-process phosphoric acid were studied with the medium-grade Sichuan Mianzhu phosphate ores and acid drainage from titanium dioxide production. The new process of chemical mineral processing, which could replace the traditional physical one, is an integration of phosphorus and titanium industry.The results of studies on mineralography of Mianzhu phosphate ores indicated that the content of P2O5was28.16%, which is the medium grade magnesium siliceous mineral. The principal phases of the phosphate ore are fluorapatite, dolomite, quartz, clay mineral and iron mineral, etc. The content of each mineral constituent was calculated by the amended calculation method. Under reaction temperature45℃±1℃, residence time2h, solid content of ore pulp65%, the optimum particle size is86%-100mesh,65%-200mesh and optimum reaction pH is2.0, under which90.40%of the rate of magnesium removal and0.0054%of the rate of P2O5loss could be obtained. For the further researches, the chemical model of magnesium removal with acid drainage was established, and the apparent grade and actual grade were contrasted with each other and studied. The improvement mechanism of reflux for WPA was studied by non-reflux and reflux WPA process experiments with the phosphate ores which had been largely preprocessed. The optimum process parameters of WPA with reflux: reaction temperature85℃, liquid concentration of SO330～40g/L, reflux ratio4:1, liquid-solid ratio3.0. Under this condition,97.81%of the recovery rate of P2O5and the good phosphogypsum which is in favor of the filtering operation could be obtained. The crystallization habit and contents of phosphogypsum were also investigated.The achievements of project, which have been applied to manufacturing partly, have provided theoretical basis, production improvement proposal and guide to the production of chemical mineral processing and WPA.