| 摘要 |
<p>1296668 Purification of phosphoric acid CENTRAL GLASS CO Ltd 23 March 1970 [24 March 1969 9 June 1969] 14029/70 Heading C1A "Wet acid" obtained by H 2 SO 4 acidulation of phosphate rock is purified by (a) contacting at 0-20‹ C. with a trialkylphosphate in which each alkyl group has C 4 to C 8 to extract more than 85% of the P 2 O 5 values therein, (b) separating extract from aqueous raffinate, (c) stripping the extract with water at 70-100‹ C. to form phosphoric acid and (d) separating the acid from the extractant, the H 2 SO 4 content of the wet acid being 2À0-7À5% wt. w.r.t. SO 3 . In the illustrated embodiment wet acid is charged to reactor 1 where its fluorine content is precipitated as Na 2 SiF 6 by addition of, e.g., Na 2 SO 4 . The liquor is mixed in tank 2 with the desired amount of H 2 SO 4 and also with phosphoric acid from wash column 4, this mixed acid is then cooled &c. and passed in countercurrent flow to extractant (tributyl phosphate) in column 3. The extract leaving 3 is heated in exchanger 10 and washed in column 4 with aq. phosphoric acid at 40-70‹ C. The washed extract then passes to stripping column 5, after heating to 70-100‹ C., where it is countercurrently contacted with water to remove P 2 O 5 values therefrom. The phosphoric acid solution is optionally passed through a charcoal bed 6 to decolorize, and is finally concentrated in evaporator 7.</p> |
