Process for the manufacture of complex fertilizers

Claim 1

IN A PROCESS FOR THE PRODUCTION OF COMPLEX FERTILIZERS CONSISTING IN DISINTEGRATING RAW PHOSPHATES WITH NITRIC ACID (50-60%) TOGETHER WITH SULPHURIC ACID (7098%), WHEREIN FOR EACH 1 MOLECULE OF P2O5 PRESENT IN THE RAW PHOSPHATE, 2 TO 5 MOLECULES HNO3 AND 2.5 TO 1 MOLECULES H2SO4 ARE USED, SUBSEQUENTLY AMMONIATING THE REACTION MIXTURE AT TEMPERATURE BETWEEN 95 AND 110*C. IN A PLURALITY OF STIRRING VESSELS CONNECTED UP IN SERIES, ADDING AMMONIA INTO THE MIXTURES IN SAID STIRRING VESSELS IN SUCH AMOUNTS THAT A PH-VALUE IN THE RANGE OF 3.5 TO 4 IS MAINTAINED IN THE NEXT TO THE LAST VESSEL, AND A PHVALUE OF 6.0 TO 7.0 IS MAINTAINED IN THE LAST VESSEL, AND DISCHARGING THE MIXTURE FROM THE NEXT TO THE LAST VESSEL DIRECTLY INTO THE LAST VESSEL WHILE MAINTAINING THE PHVALUE IN THE LAST VESSEL BETWEEN 6.0 AND 7.0 AND THUS ABRUPTLY RAISING THE ADDED MIXTURE TO THE SAME PH.