Experimental Studies On Preparation Of Gypsum Powder From Yuan'an County Phosphogypsum

Phosphogypsum is a by-product from wet producing process of Phosphoric Acid. With the growth in demand for phosphoric acid, ammonium phosphate and triple superphosphate(TSP) in industry and agriculture, China has become the largest phosphogypsum country. Yuan'an County is rich in phosphorit resources and it also has many phosphorus chemical industry enterprises which let out one more million phosphogypsum annually. When those enterprise in biulding are put into production, the amount of phosphogypsum being let out will increase to 2 million annually. Massive phosphogypsum emissions occupied vast areas of land and a large sum of capital will be needed to construct tailings dam. Moreover, some water-soluble phosphate pollute environment because of its entering into waterbodies with rain. Therefore, the treatment of phosphogypsum is of economical significance, social significance and practical value.The main findings of this dissertation are as follows:1.The content of gypsum dihydrate in various partical size fractions and the size distribution of impurities of phosphogypsum was ascertain by carrying on a series of mineral composition test analysis. According to size distribution, the fine particle size fraction were rich in gypsum dihydrate, approximate 94%, while it is low in coarse particle size fraction which is enrich with quartz.2.According to DSC(differential scanning calorimetric curve)of phosphogypsum, the calcine test condition was determined. The results of calcinations temperature test, heating rate test and heat preservation time test show that flexural strength is highest when calcination temperature is 180℃ ,the heating rate is 4.7℃ per minute and the preservation time is 2 hours.3.According to the grinding condition, the properties of gypsum is best when rotational speed is 629r/min, and the corresponding particle size of D₉₀ is 17μm.4.The aging experiment indicated that aging time has a strong influence on the gypsum properties and it has adverse effect on the properties when the aging time is too long or too short, the result shows 5 days is the best.5.According to the lime adding test, When lime added in front of the calcine, it can not only neutralize acids in phosphogypsum but also work as the powerful...