Two-step method to produce monocalcium phosphates from lime softening water plant residuals
OwnerAlexander P Mathewsinventor
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Abstract
This disclosure provides a two-step process to produce monocalcium phosphates from lime water treatment plant lime softening residuals and from other sources containing calcium salts. This patent focuses on the reuse of lime softening residuals to produce monocalcium phosphates and dicalcium phosphates for use in a variety of applications including as quick release and slow release fertilizers, for animal feed and other applications. The two-step process is conducted close to ambient temperatures and under controlled pH conditions to produce substantially pure calcium phosphate products while at the same time capturing the carbon dioxide generated in the process.
Claims17
A two-step method to produce substantially pure monocalcium phosphates (MCPs) from lime softening water plant sludge with a first step comprising:
- (a) Providing lime softening water plant sludge with or without coagulant sludge;
- (b) Reacting the lime softening water plant sludge containing 1% to 100% solids by dry weight with a sufficient quantity of an aqueous solution of phosphoric acid under controlled reaction conditions including pH, mixing, duration of reaction, water to dry sludge ratio, phosphoric acid to dry sludge ratio, and method and order of reactants addition, to obtain a solid precipitate of dicalcium phosphate (DCP) in its anhydrous or hydrated form along with provisions to capture the carbon dioxide generated in the aforementioned reaction;
- (c) Recovering the precipitated DCP by solid-liquid separation and reacting the said DCP with phosphoric acid in a second step under controlled reaction conditions including pH, water amount, mixing, duration of reaction, water to dry DCP ratio, acid to dry DCP ratio, and method and order of reactants addition to obtain monocalcium phosphate as a solution or as a dry solid product by employing concentration and drying processes.
Dependencies are inferred from the claim text.