JPS57200212A - Filtration of phosphoric acid in the manufacture of phosphoric acid by the wet process - Google Patents

Abstract

PURPOSE: When phosphoric is filtered, only the filtrate from the cake filtration among the three zones, i.e., the filter filtration, filter washing and cake filtration, is made the product of phosphoric acid, whereby high-concentration phosphoric acid with less solid content included in produced.

CONSTITUTION: The gypsum slurry 62 is filtered with filter 61 and the gypsum cake is washed with water at the later stage of filtration and the gypsum cake on the filter is treated at the next stage. At the filtration stage, a small amount of solid components come through the filter together with the filtrate at the begining stage, because there is no solid on the filter 61. It is given as the filter filtration zone 64. At the middle stage, the cake layer is formed on the filter and the solid component is substantially stopped on the filter. It is given as the cake filtration zone 65. Further, at the later stage, the cake is washed with the solution 66 and a small amount of the solid component passes through the filter. It is given as the filter-washing zone 67. Each filtrate 68, 71, 74 from the zones 64, 65 and 67 comes into each sealed tank 69, 72 and 75 and the filtrate in the tank 72 is used as the product and the others are used for circulation.

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