Study On The Factors Influencing The Cyclic Decomposition Of Medium And Low Grade Collophane By Phosphoric Acid

The characteristics of phosphate rock in China are abundant but not rich.With the depletion of phosphorus rich mineral resources.Phosphogypsum,a by-product of the traditional wet phosphoric acid process,which relies on the integration of high-grade phosphate ores,has not been used effectively for a long time.Impurity-rich phosphogypsum deposits require land resources and cause environmental pressure,Which has gradually become the economic and technical burden of phosphorus chemical enterprises.In view of this,This paper is to improve the process technology of wet-process phosphoric acid in dihydrate process,and to improve the quality and utilization value of the by-product phosphogypsum in the acid hydrolysis process.The factors influencing the process of phosphoric acid leaching of medium and low grade collophane ore were studied.For this reason,the influence test of industrial phosphoric acid leaching of medium and low grade phosphate ore was conducted.To explore the influence of impurity components on phosphate ore leaching by phosphoric acid,and to deeply analyze the mechanism of acid hydrolysis reaction and the leaching kinetics of phosphorus.The main conclusions of this experiment are as follows:Suitable conditions for industrial phosphoric acid decomposition of medium and low grade phosphate ore:Acid ratio is 6.8?Grinding fineness less than 0.074mm grain size accounts for 60%?Reaction temperature is 50??Stirring rate is 300r/min?leaching time is 2.5h.The phosphorus leaching rate can reach 87.69%under suitable decomposition conditions.Among the solid by-products produced after the preparation of phosphoric acid,the mass fraction of high-purity gypsum is 35.32%,and the mass fraction of acid-insoluble slag is 64.68%.The chemical analysis of Ca SO₄·2H₂O in high-purity gypsum is 95.80%,and the industrial utilization value is high,which is beneficial to improve the utilization rate of wet-process phosphoric acid by-products.The influence of industrial phosphoric acid composition on phosphorus leaching rate were studied.It was found that at the same PO₄^3-mass concentration,the decomposition effect of phosphate ore with pure phosphoric acid was significantly better than that of industrial phosphoric acid.The results show that PO₄^3-concentration has little effect on phosphorus leaching rate;When H₂SO₄ was added to pure phosphoric acid,it was found that adding sulfuric acid in the condition of low phosphoric acid ratio could significantly improve the phosphorus leaching effect,while adding sulfuric acid in the condition of high phosphoric acid ratio could slightly reduce the phosphorus leaching rate,It shows that H⁺is the main factor affecting the phosphorus leaching effect,while SO₄^2-slightly reduces the phosphorus leaching effect;while the addition of Mg SO₄,Al₂?SO₄?₃ and Fe₂?SO₄?₃ has no obvious influence on the phosphorus leaching effect.Adding equal concentrations of Al?OH?₃,Mg?OH?₂ and Fe?OH?₃ respectively has a certain weakening effect on phosphorus leaching rate.It indicates that SO₄^2-,Al³⁺,Mg²⁺and Fe³⁺in the liquid phase have little effect on the leaching effect,H⁺concentration can affect phosphorus leaching rate.During the decomposition process,the foaming performance of industrial phosphoric acid is obviously lower than that of pure phosphoric acid.The response was mild.By studying two factors affecting the kinetics of phosphate ore decomposition,namely reaction temperature and acid ratio,It is found that the Drozdorff equation can better describe the kinetic model of industrial phosphoric acid decomposing phosphate rock,and the correlation coefficient of the fitting curve is above 0.99.The activation energy Ea=31.915 KJ/mol and the frequency factor A=e^7.00407=1101.106min^-1 were calculated,indicating that the industrial phosphoric acid decomposed phosphate ore belongs to the mixed control.The kinetic equation was obtained as follows:???In summary,Industrial phosphoric acid decomposing phosphate rock process can improve the quality and industrial utilization value of phosphogypsum.Compared with the traditional phosphogypsum,the high-purity gypsum produces a relatively small amount of impurities,expands the utilization route,and has a good development prospect.