Fertilizer material from apatite
AssigneeNational Research Development Corporation
InventorsFredrik P. Glasser, Richard P. Gunawardane
Life of this patent
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Abstract
Apatite is conventionally made into a fertilizer material by treatment with a strong acid, requiring capital-intensive industry. Hydroxyapatite is treated above 1100 C. with alkali but world reserves are problematic. The invention treats apatite at 900 C. with sodium aluminosilicate/carbonate and siliceous material in quantities to keep the composition in terms of CaO, SiO.sub.2, Na.sub.2 O and P.sub.2 O.sub.5 in or near the ternary system Ca.sub.2 SiO.sub.4 --Ca.sub.3 (PO.sub.4).sub.2 --CaNaPO.sub.4.
Claims7
A method of making a fertilizer material from hard mineral apatite rich in chlorine and/or fluorine, by roasting apatite at from about 880.degree. C. to about 900.degree. C. as a final temperature with a carbonate and/or aluminosilicate of an alkali metal in an amount such that the molar ratio apatite (as P.sub.2 O.sub.5):alkali metal is 1:
- at least 3 and in the presence of sufficient siliceous material to keep the free-lime content of the fertilizer material below 2 weight % and to inhibit formation of tetracalcium phosphate.
Dependencies are inferred from the claim text.