Studies On De-fluorination Technology Of Wet Phosphoric Acid Reaction Process

The phosphoric acid is mainly used by wet process phosphoric acid in our country,namely,it will be extracted in acid reaction through combining phosphate rock and H2SO4,H3NO4 and HCl,but most of the fluorine in phosphate rock will go into the phosphoric acid,which not only seriously affects the subsequent use of the phosphoric acid,but also adverses to the comprehensive utilization of fluorine resources.At present,the study of the purification of the hydrochloric acid in both domestic and foreign countries is based on the large phosphoric acid,and the studies of the fluorine in the process of the acid are rarely reported in the process.This topic mainly studies the defluorination in the process of wet-process phosphoric acid,namely in the process of reaction of sulfuric acid and phosphate rock.Firstly,the process characteristics of the phosphate rock were analyzed comprehensively,which provided theoretical basis for the later experiments.The effects of changing the process conditions,sodium salt and gas extraction on the fluorine content in gypsum and phosphoric are studied.The main research contents and conclusions are as follows:(1)Analysising the phase and chemical components,it is concluded that calcium fluoride is the main component of phosphate,including P2O5 of 29.1%,the MgO of 1.86%,CaO of 41.63%,SiO2 of 8.32% and F of 3.31%.By analyzing the inhibition and reaction activity of phosphate rock,we can know the activity is 99.43% and the resistance to retardation is 3.25,the higher the activity of phosphorite,the easier the decomposition is,the stronger the resistance is.Analysising the foamability of phosphorite,we can find the stability of foam is high-2197 mL·min,it belongs to the low-grade phosphate rock with severe foaming.(2)In the process of concentrated sulfuric acid dephosphorization ore,by changing the reaction temperature,reaction time,liquid-solid ratio,speed to test fluorine content in the phosphoric acid and gypsum,then finally we can optimize the experimental conditions by RSD.According to the single factor and response surface design(RSD),the following conclusions are drawn: the reaction temperature has the most influence on the change of fluorine content in phosphoric acid,and the interaction effect is the reaction temperature and liquid-solid ratio.The most important effect on gypsum is the liquid solid ratio.The interaction effect is the reaction temperature and reaction time.From that we know in the condition of the reaction time of 53.33 min,reaction temperature of 64.44?,the liquid-solid ratio of 3.04,the fluorine content in the phosphoric acid is 0.18%;While in the condition of the response time of 60.36 min,reaction temperature of 65.68?,liquid-solid ratio of 3.5,the fluorine content of gypsum is the lowest 0.27% at this time.(3)In the process of producing wet-process phosphoric acid,defluorination is added to achieve the defoluorination effect.By studying the different deflorination agent dosage,reaction temperature,reaction time to test the fluorine content in the phosphoric acid and gypsum,The experimental condition is optimized by response surface experiments.According to the single factor and response surface experiment,the following conclusions are drawn: the most significant effect on the change of fluorine content in phosphoric acid is the reaction temperature,and the interaction effect is the reaction temperature and th e dosage of sodium carbonate.The maximum effect of the reaction temperatureon gypsum is the amount of sodium carbonate and the reaction time.We conclude that the reaction time is 117.6 min,reaction temperature is 74.25?,the dosage of sodium carbonate is 104.5%,the fluorine content in the phosphoric acid is 0.068%.There is no suitable prediction result for the lowest fluoridentent in gypsum.(4)The aim injecting into the gas in the acid decomposition reaction phosphate rock is to achieve the gas stripping,the influence of aeration rate,reaction time,reaction temperature and acid rate on the fluorine content in gyp sum and phosphoric acid is studied,and the experimental conditions were optimized by orthogonal experiment design.Combing the single factor and orthog-onal experiments,we draw the following conclusions: for the fluorine contente in gypsum,reaction temperature is the biggest factor influence on the experiment,as for fluorine content in the phosphoric acid,the reaction temperature has the biggest factor influence on the experiment.For gypsum,the best factor is the reaction temperature of 50?,reaction time of 120 min,the ventilation rate of 500 ml/min,and sour time of 90 s,under this condition the gypsum in the fluorine content is 0.45%,the fluorine content in the phosphoric acid is 0.18%;Best as for phosphoric acid,the reaction temperature 60?,reaction time,120 min,the ventilation rate of 700 ml/min,add acid to 60 s,the fluorine content of gypsum in the condition is 0.51%,the fluorine content in the phosphoric acid is 0.15%.