The Solvent Extraction Purification Wet-process Phosphoric Acid Technology Research

The WPA contains some impurities as Iron, Aluminum, Magnesium, Fluorin, Silicon, Sulfur, Organic matter and so on, and it is not directly used to produce the industrial and the food phosphoric acid and fine phosphate. Aiming at the problem, the technology for purification of WPA by solvent extraction process is studied in this paper. Firstly, the typical industrial process for purification of WPA by solvent extraction process and the advantage and disadvantage of the extraction agent are analyzed and compared according to the existing technology. The appropriate extraction agent is opted. And then studying on experimentation for purification of WPA by solvent extraction process is finished. By a series of studying on experimentation, the technical routes and parameters are optimized. They contains: ①The defluorination additive A is joined in a reactor by the dry-powder, and the dosage is 102%—105% of the academic dosage. The dosage of the desulfatization additive B is 100% of the academic dosage. The dosage of the dechromation is 0.5% of the weight of the WPA, and the temperature of the reaction is 55℃, the time of the reaction is 3 hours. ②The fitting dosage of the thinner is 10% of the total weight of the organic extraction solvent (Tri-Butyl-Phosphate and coal oil). The fitting dosage of the Tri-Butyl-Phosphate and coal oil is double of the weight of the WPA. The temperature of the extraction is 20~25℃. The fitting dosage of the SA is 0.5% of the WPA. ③The fitting dosage of the scrubbing matter is 0.75% of the total weight of the organic phases. The temperature of the scrubbing is 20~25℃. The concentration of the scrubbing matter is 15%. ④The fitting dosage of the pure water for the stripping is 30% of the total weight of the organic phases. The temperature of the stripping is 20—25℃.Compared with the existing technology all over the world, the advantage and the innovation contain: ⑤The process of the defluorination, the desulfatization and the dechromation are finished in the same reactor and the heat of the reaction is used to keep the temperature of the dechromation in the phase of the pretreatment of WPA. It is not only to decrease the time of the reaction, to increase capabilities of the equipment and decrease the invest cost of the equipment, but also to economize the energy and to decrease theoperating costs. ②In the phase of the scrubbing, the water-phase of the scrubbing is directly used to produce concentrated superphosphate . The quality of the PA is enhanced and the subsequent treatment is easier.Using the process to purify WPA, the quality of the PA can reach to the national standard of the thermal-process food phosphoric acid. The received ratio of the manufacture PA is higher than 65%. The total used ratio of the phosphorus is higher than 98% by reusing .The quality of the byproduct concentrated superphosphate and industria TSSP is eligible. Organic solvent can be recycled by reusing and rebirth.