Method of dewatering a wet process phosphoric acid slurry
AssigneeNalco Chemical Company
InventorsKrishnan J. Pillai, Lawrence J. Connelly, William K. Gustafson
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Abstract
A digested slurry from a wet process phosphoric acid production process is dewatered by gravity-assisted vacuum filtration using as a filtration aid an aqueous solution of a polymeric filtraton aid that has been subjected to high shear mixing to enhance the performance of the filtration aid and enhance the filtration.
Claims17
A process for the dewatering of a digested slurry from a wet process phosphoric acid production digestion process comprising, in sequence:
- subjecting an aqueous solution of polymeric filtration aid to sufficient high shear mixing to enhance the performance of said polymeric filtration aid,
- wherein said polymeric filtration aid is comprised of at least one polymer having a Reduced Specific Viscosity value within the range of from about 1 to 50 prior to said high shear mixing and being comprised of from about 50 to about 100 mole percent of nonionic polar mer units and from about 0 to about 50 mole percent of ionic mer units, and
- wherein said aqueous solution has a concentration of said polymer filtration aid of from about 0.05 to about 5.0 weight percent;
- then adding said aqueous solution of polymeric filtration aid of said digested slurry in an amount sufficient to enhance a subsequent vacuum filtration of said digested slurry;
- and
- then subjecting said digested slurry disposed with said polymeric filtration aid to said gravity-assisted vacuum filtration,
- wherein the temperature of said digested slurry at all times from the time said aqueous solution of polymeric filtration aid is added to said digested slurry through the time of said gravity-assisted vacuum filtration is within the range of from about 63.degree. C. to about 135.degree. C., and
- wherein said gravity-assisted vacuum filtration enhancement is an increase of the ratio of filtrate volume per gravity-assisted vacuum filtration time.
A wet process phosphoric acid production process, wherein phosphate rock is digested with sulfuric acid at a temperature within the range of from about 60.degree. to about 135.degree. C. to form a digested slurry containing calcium sulfate crystals and a liquid phase, said liquid phase containing from about 28 to about 42 weight percent soluble P.sub.2 O.sub.5, and wherein said digested slurry is dewatered by gravity-assisted vacuum filtration prior to any substantial drop in the temperature of said digested slurry from said digestion temperature, characterized in that:
- said digested slurry is dosed with an aqueous solution of polymeric filtration aid at a point ahead of said dewatering,
- wherein said digested slurry is comprised of from about 55 to about 70 weight percent of said liquid phase and from about 30 to about 45 weight percent of solids at the time said digested slurry is dosed with said aqueous solution of polymeric filtration aid,
- wherein said aqueous solution of polymeric filtration aid is prepared by forming an aqueous solution of a filtration aid polymer at a concentration of at least about 0.15 weight percent, said filtration aid polymer having a Reduced Specific Viscosity value of from about 1 to about 50 and being comprised of from about 50 to about 100 mole percent of nonionic polar mer units and from about 0 to about 50 mole percent of ionic mer units, and then subjecting said aqueous solution of polymeric filtration aid to high shear mixing in sufficient degree to reduce said Reduced Specific Viscosity value of said filtration aid polymer at least five percent, and
- whereby said gravity-assisted vacuum filtration is enhanced by an increase of the ratio of filtrate volume per gravity-assisted vacuum filtration time.
Dependencies are inferred from the claim text.