| 摘要 |
<p>1,052,986. Phosphoric acid; alkali metal and ammonium phosphates. PRODUITS CHIMIQUES PECHINEY-SAINT GOBAIN, and U.C.B. (UNION CHIMIQUE-CHEMISCHE BEDRIJVEN). June 28, 1963 [June 29, 1962 (3)], No. 25861/63. Heading C1A. [Also in Division B1] A process for the continuous manufacture of phosphoric acid comprises treating natural phosphates with H 2 SO 4 and filtering the resulting mixture, part of the filtrate containing phosphoric acid being returned to the reaction mixture to maintain the fluidity thereof, the filtration being carried out by means of a continuous filter and a primary fraction of the filtrate containing phosphoric acid being collected separately from the remainder of the filtrate for return to the reaction mixture. The primary fraction may be collected near the point where the reaction mixture is poured on to the filter. The residue on the filter may be washed and the washings may be mixed with the primary fraction for return to the reaction mixture. Impurities in the phosphoric-acidcontaining filtrate may be removed by allowing the filtrate to cool and stand, with or without stirring. Alternatively, chemical precipitation of the impurities may be effected by addition of one or more precipitants, e.g. alkali metal (such as Na or K) and/or ammonium salts, e.g. carbonates and/or sulphates, calcium salts, e.g. phosphates or carbonates, barium salts or additional sulphate ions. When it is desired that the phosphoric acid shall contain alkali metal and/or ammonium phosphates, an excess of alkali metal and/or ammonium salt relative to the quantity necessary for defluorination and/or desulphation can be added, optionally with a salt of any other metal whose phosphate is required to be present. Flocculating agents and adsorbent substances, e.g. activated carbon, may be added to clarify the filtrate.</p> |
