Patent ID: 7396474

Claim:
A polymeric filtration aid method for gypsum removal from phosphoric acid/gypsum slurry, the method comprising: a dual injection process where two different polymers are separately injected into a phosphoric acid/gypsum slurry at a different time, followed by filtration of gypsum solids from a liquid phosphoric acid, wherein said phosphoric acid/gypsum slurry is produced from western phosphate ore obtained from mines in Idaho, and wherein the two different polymers are respectively comprised of different polymer chemistries of filtration aid A and B respectively, the polymer chemistry of filtration aid A being selected from the group consisting of non-ionic and anionic polymers produced from acrylamide and acrylic acid monomers, and the polymer chemistry of filtration aid B being selected from the group consisting of sulfonated polymers, wherein the sulfonated polymers comprise acrylamide tertialy-butyl (ATBS) and acrylamide or acrylic acid copolymers.