| 摘要 |
<p>Minerals and concentrates containing apatitic phosphates are treated to recover the P2O5 they contain by the following process: (a) the mineral or concentrate is leached with aqueous NH4H2O4. (b) Optionally excess hydrogen sulphate is neutralised. (c) The product from (a) and (b) is filtered to give a first filtrate and a filter cake of gypsum, CaCO3, and insoluble impurities. (d) Sulphate is recovered from the filter cake of (c). (e) The product from (d) is filtered to give a second filtrate, comprising ammonium sulphate and calcium carbonate part of which may be used in step (b) or to generate CO2 used in step (d), the rest being rejected. (f) The first filtrate from step (c) is treated with ammonia and (g) it is filtered to give a third filtrate, comprising ammonium hydroxide which is used in step (d), and a filter cake of triammonium phosphate. (h) The filter cake from (g) is dried to give NH3 which is used in steps (d) and (f). (i) The dried product from (h) is granulated, to give the desired mono- and di-ammonium phosphates. (j) The second filtrate from step (e) is submitted to a crystallisation, and the product dried to give dry ammonium sulphate which is (k) heated to effect thermal decomposition with formation of ammonium hydrogen sulphate and liberation of ammonia that isused in step (d) and (f), together with the ammonia from step (h). (l) The ammonium hydrogen sulphate from step (k) is used in step (a). The process gives good recovery of soluble phosphates without loss of the sulphates necessary to bring about solubilisation. There is no costly thermal treatment and no evaporation of large quantities of water.</p> |
