PROCESS OF PREPARING EXTRACTIVE PHOSPHORIC ACID AND APPARATUS FOR PREPARATION THE SAME Russian patent published in 1994 - IPC

FIELD: inorganic chemistry. SUBSTANCE: starting phosphorus-containing raw material is mixed together with sulfuric acid, recycle phosphoric acid, phosphogypsum seed and washings. The suspended phosphate product formed in extractor is subjected to the primary settling to remove phosphoric acid formed during reaction, and the concentrated phosphate suspension is mixed together with washing water. Thereafter, the resulting solution is subjected to the secondary settling followed by countercurrent washing of phosphogypsum with fresh portion of water to obtain aqueous suspension of phosphogypsum. The aqueous phosphogypsum suspension is filtered to give washing water. The rate of ascending flow of water at the stage of countercurrent washing is lower than that of the up-current under the secondary settling. The content of solid phase in recycle phosphoric acid formed at the stage of the secondary settling is controlled by changing the rate of ascending flow due to partial return of recycle phosphoric acid. Apparatus for realization of the process described above is reciprocating-plate pulse extraction column with built-up contact members. The intermediate settling chamber is disposed between the upper settling chamber and casing of the apparatus to mix the concentrated phosphate suspension with washing water and for its secondary sedimentation, with such intermediate settler is provided with overflow tube shell and choke manifold for inlet of washing water and a part of recycled phosphoric acid and outlet of the total flux of recycle phosphoric acid. EFFECT: increased efficiency. 2 cl, 1 dwg