FILTERING METHOD OF SLURRY IN PHOSPHORIC ACID MANUFACTURING PLANT

PURPOSE:To efficiently and easily separate into a gypsum and a phosphoric acid solution by providing an eddy stream of slurry consisting of the phosphoric acid and the gypsum just in front of a filter, coagulating the gypsum by adding a coagulant, and subsequently bursting to the filter. CONSTITUTION:A cylindrical slurry feeding box 41 which has a coagulant feeding inlet 43 over its upper part, a funnel-shaped taking-out outlet 44 under the bottom part, and a downward diagonal nozzle 42 on the sidewall, is installed just in front of the filter 10 which filters the slurry of the phosphoric acid and gypsum. The slurry is made into an eddy stream by bursting the slurry of phosphoric acid and gypsum into the box 41 from the nozzle 42, the coagulant 46 (e.g., an anionic high polymer coagulant) is continuously fed and mixed in this stream, and the mixture is bursted to the filter 10 from the taking-out outlet 44 while the gypsum is being coagulated. Thus, the mixture is separated into the gypsum cake 26 and the phosphoric acid solution 27 through the filter 10.