Production of phosphates from phosphate rock by solvent extraction

Claim 1

A PROCESS FOR PRODUCING FROM PHOSPHATE ROCK DICALCIUM PHOSPHATE OF ANIMAL FEED GRADE COMPRISING (1) DECOMPOSING SAID PHOSPHATE ROCK WITH AN AQUEOUS SOLUTION OF NITRIC ACID TO FORM AN AQUEOUS SOLUTION CONTAINING CALCIUM NITRATE, PHOSPHORIC ACID AND NITRIC ACID AND CONTAINING 135-200 GRAMS OF P2O5 PER LITER OF SOLUTION, (2) SEPARATING THE ACID VALUES OF SAID AQUEOUS SOLUTION FROM SAID CALCIUM NITRATE BY EXTRACTING SAID ACID VALUES WITH A POLAR ORGANIC SOLVENT HAVING LIMITED MISCIBILITY WITH WATER THE VOLUME RATIO OF POLAR ORGANIC SOLVENT TO AQUEOUS SOLUTION BEING BY VOLUME AT LEAST 1:1 THEREBY LEAVING THE MAJOR PORTION OF CALCIUM NITRATE IN SAID AQUEOUS PHASE, (3) WASHING THE POLAR ORGANIC SOLVENT WITH A WASHING MEDIUM SELECTED FROM THE GROUP CONSISTING OF WATER AND AN AQUEOUS SOLUTION OF PHOSPHATES AND NITRATES TO REGENERATE SAID POLAR ORGANIC SOLVENT, THEREBY PRODUCING A SUBSTANTIALLY ACID-FREE POLAR ORGANIC SOLVENT PHASE AND AN ACID-CONTAINING AQUEOUS PHASE, (4) RECYCLING SAID SUBSTANTIALLY ACID-FREE POLAR ORGANIC SOLVENT PHASE TO SAID EXTRACTION IN STEP 2, (5) NEUTRALIZING SAID ACID-CONTAINING AQUEOUS PHASE WITH A LIME-CONTAINING MATERIAL TO CORRECT THE MOLAR CAO/P2O5 RATIO TO 2:1 THEREBY REMOVING IMPURITIES THEREFROM AS A PRECIPITATE, (6) ADDING AMMONIA TO SAID NEUTRALIZED AQUEOUS PHASE THEREBY PRECIPITATING DICALCIUM PHOSPHATE AND (7) SEPARATING SAID DICALCIUM PHOSPHATE FROM SAID AMMONIA-TREATED AQUEOUS PHASE.