Study On Extraction Process And Technology Of Phosphoric Acid In Wet-Process Phosphoric Acid System

In this paper,the phosphate hydrolysis system was studied. The chemical composition, crystal structure and micro-surface morphology were studied by atomic absorption spectrometry, SEM and electron probe. The results show that the surface morphology, crystallinity and impurity composition of Yindong, Liushugou and Dingjiaba are different.Based on the production parameters of a wet-process phosphoric acid plant,the reaction process of sulfuric acid leaching phosphate rock was studied. Experimental conditions including reaction temperature（80℃）,stirring speed （300r min-1）and reaction time （180 min）. And slurry was filtrated, the methods including SEM, XRD,EDS, BET and laser particle size were used for characterizing the resultant crystals.Atomic absorption spectrophotometer（AAS） was employed for determining the concentration of relevant ions. The results showed that phosphate ore was basically decomposed and transformed into CaSO₄ 2H₂O grain at the moment of 120 min. The growth of CaSO₄ 2H₂O was occurred on the surface of phosphate ore conformed to step growth models at the beginning. As the reaction progressed,the crystal dropped from the surface of phosphate ore and the frame structure of ore gradually collapsed.So the average particle size first increased and then decreased. The hysteresis loop of nitrogen adsorption isotherms changed from H3 into H4.Based on the study of Yindong phosphate rock process,the technological parameters of Dingjiaba and Liushugou phosphate were optimized, and the effects of stirring rate and reaction temperature on the extraction rate of phosphoric acid were analyzed. The optimum reaction parameters were optimized by the orthogonal experiment of Yindong phosphate rock, the reaction temperature was 80℃, the rotation speed was 300r / min, the amount of sulfuric acid added was 33gH2SO4 and the reaction time was 8 hours.In addition, the effects of sulfuric acid with different H + concentrations on the acid hydrolysis of phosphate rock were studied. The morphology, crystal phase, specific surface and composition of CaS04 crystal were studied by SEM, XRD, specific surface area and chemical analysis. The results showed that with the increase of H +concentration,CaSO₄·2H₂O had a tendency to convert to anhydrous calcium sulfate at medium and high concentration. At the same time, the reaction process of hydrochloric acid and nitric acid was studied.