Deep Processing Cycle Process Of Phosphogypsum

With the rapid development of phosphorus chemical industry,the output of industrial by-product phosphogypsum has been increasing year by year.However,phosphogypsum has been lacking effective comprehensive utilization for a long time.Most of the phosphogypsum is simply piled in the tailings pond,which not only caused phosphogypsum is a waste of resources,and it takes a huge amount of money to maintain the operation of the phosphogypsum tailings reservoir.Large amounts of phosphogypsum will also pose a great threat to the environment.Over the past decade,with the increasingly prominent issue of phosphogypsum,scholars at home and abroad have proposed a variety of phosphogypsum-based comprehensive utilization technology projects,in which phosphogypsum is converted into Ammonium sulfate and other fertilizers and joint production of cement technology are relatively mature,but are limited by economic costs and environmental impact and have not been applied on a large scale.With the country’s increasing emphasis on the environment,the problems caused by phosphogypsum are increasingly severe,and even the continuous development of the phosphorus chemical industry has been restricted.The comprehensive utilization of phosphogypsum is in urgent need of solution.In this paper,the phosphogypsum deep processing cycle process is analyzed by analyzing the composition and the state of occurrence of impurities in phosphogypsum.First,the thermodynamic analysis of the influence of impurities in the decomposition of phosphogypsum by NaOH is performed by querying the relevant thermodynamic data,and verified by thermodynamic calculation.The theoretical feasibility of the process;followed by a single factor test method to determine the phosphogypsum deep processing cycle.The best process conditions parameters;the final use of bipolar membrane electrodialysis electrolytic filtrate recycling and utilization of sodium hydroxide and sulfuric acid,the formation of a comprehensive utilization ofphosphogypsum in a comprehensive process cycle.The specific study is as follows:1.Through XRD and chemical analysis,the results showed that the main component of phosphogypsum was CaSO4.2H2 O,and the main impurities were P,Si,F and some metal ions.Through thermodynamic theoretical calculations and investigations of the departure and migration laws of various substances in the conversion process of phosphogypsum,it was found that most of the impurities exist in the form of acid-insoluble substances in the phosphogypsum conversion process,and only a small amount of Al,Si,and other ions follow the sulfuric acid.Sodium is dissolved in the filtrate together.2.The optimum process conditions for determining the phosphogypsum deep-processing cycle process through the single-factor test method are as follows: for each 10 g of phosphogypsum during conversion of sodium hydroxide to phosphogypsum,the consumption concentration is 12.5.% of sodium hydroxide 40 ml,solid-liquid ratio 4:1,reaction temperature 20°C,reaction time 10 min,stirring speed 15 r/s,and adding two times at intervals of 5 min,using calcium slag to obtain high purity In the phosphogypsum process,10.0 mol/kg hydrochloric acid and 5.0 mol/kg sulfuric acid gave gypsum with a purity of 99.72% under optimal conditions.3.The sodium sulfate in the filtrate is recovered by a bipolar membrane electrodialysis method,and the acid and alkali obtained after electrolysis of the filtrate are recycled to decompose the phosphogypsum.The optimum conditions for electrolysis were determined as current density 47.6 mA/cm2 and salt concentration 1.143 mol/L.The energy consumption is the lowest and the efficiency is the highest.The electrolysis rate reaches 99.04%,the energy consumption is 1.529kWh/kg,and the current efficiency It is62.23%.After detection,the concentration of sulfuric acid obtained after electrolysis was0.9249 mol/L,and the concentration of sodium hydroxide(potassium hydroxide)was2.1257 mol/L,which could be recycled and used to decompose phosphogypsum.4.The scale-up test of this process shows that consumption of 360 g of sodium hydroxide per 600 g of phosphogypsum can produce 363 g of high-purity calcium sulfate,216 g of sodium hydroxide,231 g of sulfuric acid,and 56.5 g of acid-insoluble matter.Product analysis results show that gypsum products and acids and bases can be used for the cyclic decomposition of phosphogypsum,and acid insolubles can also be used for industrial production of cement.This process has no secondary pollutants and the product can be returned to the process.Industrial application value better.The results of the study showed that the phosphogypsum deep processing cycle process.Compliance with the conservation of the quality of the product,through the analysis of the product,the product can be recycled again,there is no secondary pollutants generated throughout the process,the product can also be recycled,with high environmental and economic value.