| 摘要 |
The disclosure relates to a process for purifying crude, concentrated wet-processed phosphoric acid. To this end, the disclosure provides: (a) for the organic solvent to be mixed with the starting product in a ratio by volume of more than 4:1 to effect in a single process step the extraction-from the crude wet-processed phosphoric acid-of a quantity of phosphoric acid necessary for 40 to 70 weight % of the P2O5 used to go into the organic phase, and for the resulting aqueous phosphoric acid raffinate to contain at most 28-32 weight % P2O5, and for the organic phosphoric acid solution to be separated from the phosphoric acid raffinate; (b) for the separated organic phosphoric acid solution to be scrubbed with a quantity of scrubbing solution corresponding at most to 5% of the volume of the phosphoric acid solution; for the scrubbing solution to be recycled into stage (a), and for purified phosphoric acid and phosphate salt solution, respectively, to be recovered in known manner from the scrubbed phosphoric acid solution; (c) for the aqueous phosphoric acid raffinate produced in stage (a) to be neutralized, if desired, after prior removal of residual solvent, for it to be subjected to treatment with an alkaline agent with the resultant formation of a purified phosphate salt solution and precipitation of a so-called neutralization sludge, and (d) for said neutralization sludge and simultaneously obtained alkali metal phosphate solution to be separated from each other, for the sludge to be mixed with finely ground phosphate ore, and for the mixture to be made into phosphate pellets for use in electrothermal phosphorus production.
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