Manufacture of phosphoric acid

Claim 1

IN A METHOD FOR PRODUCTION OF PHOSPHORIC ACID ACCORDING TO THE WET PROCESS, COMPRISING THE STEPS OF REACTING IN A REACTION ZONE SOLID PHOSPHATIC MATERIAL WITH SULFURAIC ACID AND DILUTE RECYCLE PHOSPHORIC ACID, MAINTAINING WITH AGITATION THE RESULTING REACTION MIXTURE IN SAID REACTION ZONE, PASSING ALL OF SAID REACTION MIXTURE TO A SEPARATION ZONE AND THERE SEPARATING BY FILTRATION A LIQUID COMPONENT COMPRISING PHOSPHORIC ACID CONTAINING A RELATIVELY DILUTE FINES SUSPENSION OF A SMALL AMOUNT OF CALCIUM SULFATE, AND A COARSE-SOLIDS SLURRY OF A MAJOR AMOUNT OF CALCIUM SULFATE, AND RECYCLING A PORTION OF SAID PHOSPHORIC ACID TO SAID REACTION ZONE, THE IMPROVEMENT COMPRISING PASSINGSAID LIQUID COMPONENT CONTAINING SAID SUSPENSION OF CALCIUM SULFATE FIENS TO A CLARIFICATION ZONE AND IMPARTING TO SAID LIQUID COMPONENT A ROTARY FLOW ALONG A SPIRAL PATH THEREBY SEPARATING SAID FINES SUSPEHSION OF CALCIUM SULFATE FROM SAID PHOSPHORIC ACID PRIOR TO CONCENTRATING THE LATTER, AND RECYCLING SAID FINES SUSPENSION OF CALCIUM SULFATE TO SAID REACTION ZONE.