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US 5,846,500 AGranted
Process for purifying highly impure calcium hydroxide and for producing high-value precipitated calcium carbonate and other calcium products
AssigneeJames W. Bunger and Associates, Inc.
InventorsJames W. Bunger, Don Cogswell, Jerald W. Wiser
Life of this patent
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Abstract
A solution process for the purification of calcium hydroxide, particularly from hydrated carbide lime, which is subsequently used as a feed stock for a high-value calcium product, preferably calcium carbonate. Precipitated calcium carbonate is formed by reaction of the purified calcium hydroxide solution with carbon dioxide in a plug-flow reaction system.
Claims18
A method for the manufacture of essentially pure calcium carbonate from impure calcium hydroxide, the method comprising;
- (a) diluting the impure hydrated calcium hydroxide with water to dissolve essentially all solid calcium hydroxide to form a solution of the calcium hydroxide with a concentration at or below the saturation concentration of calcium hydroxide,
- (b) separating remaining solid materials by gravity separation by introduction of the solution from (a) into a quiescent environment sufficient to allow gravity separation of floatable solids that rise to the top surface of the solution and settling solids that sink to form a sludge and withdrawing the floatable solids and the sludge containing the sinking solids,
- (c) filtering the resultant solution of calcium hydroxide of step (b) to remove solids remaining in suspension after the separation in step (b),
- (d) contacting the filtered solution from step (c) with carbon dioxide gas under cocurrent plug-flow conditions to form a slurry of calcium carbonate crystals,
- (e) introducing flocculation aids into the resultant slurry of calcium carbonate crystals of step (d) to promote weak association of the calcium carbonate crystals,
- (f) dewatering the associated calcium carbonate crystals by gravity separation in which the resultant slurry of step (e) is introduced into a quiescent environment sufficient to allow settling of the associated calcium carbonate crystals to form an essentially clear solution and to form a thickened slurry of the associated calcium carbonate crystals.
3 more elements
A method for purifying impure calcium hydroxide to form purified calcium product, the method comprising;
- (a) diluting the impure calcium hydroxide with water to dissolve essentially all solid calcium hydroxide to form a solution of calcium hydroxide with a concentration at or below the saturation concentration of calcium hydroxide,
- (b) separating solid materials by gravity separation by introduction of the solution from (a) into a quiescent environment sufficient to allow gravity separation of floatable solids that rise to the top surface of the solution and rapidly settling solids that sink to form a sludge and withdrawal of the floatable solids and the sludge containing the sinking solids,
- (c) filtering the resultant solution of calcium hydroxide of (b) to remove solids remaining after the separation in (b) to form a purified calcium hydroxide solution,
- (d) reacting the purified calcium hydroxide solution with a reagent to form a purified precipitated calcium product with a solubility less than calcium hydroxide.
1 more element
Dependencies are inferred from the claim text.