Chemistry of inorganic compounds – Phosphorus or compound thereof – Oxygen containing
Reexamination Certificate
2008-03-14
2011-10-11
Le, Emily (Department: 1734)
Chemistry of inorganic compounds
Phosphorus or compound thereof
Oxygen containing
C423S317000, C023S29500G
Reexamination Certificate
active
08034312
ABSTRACT:
The invention relates to a method for the purification or recovery of orthophosphoric acid rich streams by suspension-based melt crystallization. The orthophosphoric acid is crystallized as the hemi-hydrate form and subsequent separation of such crystals in a wash-column produce a high purity acid/water solution that has been depleted of most of the metals and impurities other than water, thereby separating an orthophosphoric acid rich feed liquor into an ultra-pure orthophosphoric acid hemi-hydrate and a mother liquor containing almost all impurities originally present in the feed. The orthophosphoric acid rich feed liquor typically contains no more than 15 wt % water and 1 wt % other impurities. Individual metal ion composition in the purified orthophosphoric acid product is in the range of 100 to 1000 ppb (parts per billion= 1/1000 ppm) of each metal ion. The metal ion composition of the resulting purified product is thus typically below the detection limit of typical analysis equipment.
REFERENCES:
patent: 3620668 (1971-11-01), Cutter
patent: 3713802 (1973-01-01), Gittenait
patent: 2007/0072402 (2007-03-01), Lee et al.
Ruemekorf Ray Sirey
Scholz Reinhard Uwe
Le Emily
Niro Process Technology B.V.
Slifka Sarah A
Young & Thompson
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