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US 7,048,900 B2Granted
Method and apparatus for production of precipitated calcium carbonate and silicate compounds in common process equipment
AssigneeG.R. International, Inc.
InventorsVijay K. Mathur, Varun K. Mathur
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Abstract
A method and apparatus for the production of calcium carbonate and calcium silicate in common superatmospheric reactors. Multiple reactors can be provided for switching production between reactors, and advantageously utilizing process waste heat. On site production of both PCC and Calcium Silicate Hydrates is thus achieved in a paper mill.
Claims68
A method for the hydrothermal production of calcium silicate hydrate and calcium carbonate in a set of common reactors, said method comprising:
- (a) providing an aqueous lime slurry, said aqueous lime slurry comprising (i) Ca(OH)2 solids and (ii) dissolved Ca(OH)2 in the form of Ca++ ions;
- (b) screening grit from said aqueous lime slurry;
- (c) conditioning said aqueous lime slurry to a predetermined temperature;
- (d) feeding a first portion of said aqueous lime slurry into a first reactor of said set of common reactors;
- (e) agitating the contents of said first reactor at super-atmospheric pressure;
- (f) introducing a stream of CO2 into said aqueous lime slurry in said first reactor, to form CO3−2;
- (g) reacting said CO3−2;
- and said Ca++ in a carbonation reaction to produce insoluble precipitated calcium carbonate (CaCO3) in said first reactor;
- (h) removing said insoluble precipitated calcium carbonate and associated water from said first reactor;
- (i) charging a second reactor of said set of common reactors with a first aqueous silica slurry comprising silica at a concentration of from about 1 to about 1.5 pounds of silica per gallon of said first aqueous silica slurry;
- (j) charging said second reactor of said set of common reactors with a second portion of said aqueous lime slurry;
- (k) heating the contents of said second reactor under hydrothermal conditions to produce a calcium silicate;
- (l) removing said calcium silicate from said second reactor;
- (m) switching feed of said first portion of said aqueous lime slurry and said CO2 to said second reactor from said frist reactor, and switching feed of said first aqueous silica slurry and said second portion of aqueous lime slurry to said first reactor, so that precipitated calcium carbonate is produced in said second reactor, and calcium silicate is produced in said first reactor.
11 more elements
An improved process to produce calcium silicate hydrates, said process comprising:
- (a) providing an aqueous lime slurry comprising lime at near boiling temperature;
- (b) providing a first aqueous silica slurry comprising silica at a concentration of between about 1.0 and about 1.5 lbs/gallon;
- (c) heating said first aqueous silica slurry;
- (d) providing a pressure reactor capable of operating at a pressure of up to 1000 pounds per square inch gauge, and filling up the pressure reactor with said first aqueous silica slurry and said aqueous lime slurry in a preselected calcium to silica mole ratio, expressed as moles of CaO divided by moles of SiO2, to provide a reactant charge in said pressure reactor;
- (e) heating said reactant charge to carry out a hydrothermal reaction between lime particles and silica to form a calcium silicate hydrate;
- (f) slowly agitating the reactant charge in the pressure vessel during the formation of said calcium silicate hydrate.
3 more elements
Dependencies are inferred from the claim text.