Study On The New Stratified Filtration Process Of Phosphoric Acid Slurry Via Wet Method

Based on the mixed filtration of phosphoric acid slurry in the conventional manufacturing of wet-process phosphoric acid, a new stratified filtration process was advanced in this article. This would greatly improve the filterability of wet-process phosphoric acid slurry, and in turn play a significant role in promoting the production of phosphoric acid.The stratified filtration experiment on phosphoric acid slurry was introduced in the first section of this article. According to the fundamental principles of solid-liquid separation, the phosphoric acid slurry was separated by hydro-cyclone to form thin and thick slurries, which were stratified-filtered by stepwise feeding of slurries. A vacuum pump was employed for filtration.The slurries used for filtration were formulated in different concentrations of phosphoric acid. Using orthogonal tests, the primary factors, such as degree of vacuum applied, filtration temperature, concentration of phosphoric acid slurry, the delayed time of stepwise feeding, and average solid particle size in thin slurry, influencing the stratified filterability of phosphoric acid slurry were investigated. The experimental results show that: as compared with the conventional mixed filtration, this technology can remarkably enhance the filtration intensity of phosphoric acid slurry. During the stratified filtration, the vacuum degree of filtration, filtration temperature and slurry concentration are among the most important factors influencing the stratified filterability of phosphoric acid slurry, followed by the average solid particle size, and finally the stepwise delayed feeding time has a weak effect on the filtration strength. The optimal operation conditions for stratified filtration are indicated as follows: The degree of vacuum filtration should be controlled at about 65Kpa, the filtration temperature should lie between 68 and 80 oC, and the stepwise delayed feeding time should approximately be 6 seconds. The experimental data are regression-fitted using Least Square method to establish an empirical mathematical model for filtration rate of phosphoric acid slurry.These results can be functioned as the theoretical fundamentals for design and operation of slurry filtration in the manufacturing of wet-process phosphoric acid, and also can be applied in the amplification and optimization of industrial production of phosphoric acid.