Claims
- 1. In a process of preparing calcium carbonate, which comprises the following steps:
- (a) slaking quicklime in an aqueous medium;
- (b) carbonating the suspension of slaked lime formed in step (a) by passing therethrough sufficient of a gas comprising carbon dioxide to cause the pH of the suspension to fall to substantially neutral; and
- (c) separating the precipitated calcium carbonate formed in step (b) from the aqueous medium in which it is suspended; wherein the improvement comprises adding a reagent comprising a polyhydric alcohol or a polyhydric phenol to the aqueous medium in which the quicklime is slaked in step (a).
- 2. A process according to claim 1, wherein the amount of said reagent is 0.01 to 15%, based on the dry weight of said quicklime.
- 3. A process according to claim 1, wherein the suspension obtained in step (a) has a calcium hydroxide concentration of from 0.7 to 4M.
- 4. A process according to claim 1, wherein the aqueous medium in step (c) is maintained at a temperature in the range from 30.degree. to 50.degree. C. and subjected to substantially continuous agitation during step (a).
- 5. A process according to claim 1, wherein the suspension obtained in step (a), is passed through a sieve of aperture size in the range from 40 to 70 microns.
- 6. A process according to claim 1, wherein the suspension is diluted to a concentration of not more than 15% weight/volume and maintained at a temperature in the range from 40.degree. to 65.degree. C.
- 7. A process according to claim 1, wherein said gas contains from 5 to 50% by volume of carbon dioxide, the remainder being air or nitrogen.
- 8. A process according to claim 1, wherein said gas is bubbled into the suspension of slaked lime in the form of fine bubbles at a rate of 0.02 to 0.10 moles of carbon dioxide per mole of calcium hydroxide.
- 9. A process according to claim 1, wherein the suspension is agitated substantially continuously throughout the carbonation step, by means of an impeller rotating at a peripheral speed of at least 200 cm per second.
- 10. A process according to claim 1, wherein the pH of the suspension is monitored throughout step (b).
- 11. A process according to claim 1, wherein the precipitated calcium carbonate is separated from the aqueous medium in which it is suspended by filtration.
- 12. A process according to claim 1, wherein said reagent comprises a polyhydric alcohol.
- 13. A process according to claim 1, wherein said polyhydric alcohol is selected from the group consisting of triethanolamine, mannitol, diethanolamine, bicine, diethylene glycol, triiso-propanolamine, N-ethylethanolamine and sodium boroheptanoate.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9016552 |
Jul 1990 |
GBX |
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CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of Ser. No. 07/996,677 filed Dec. 24, 1992, abandoned, which in turn was a continuation-in-part of Ser. No. 07/736,488 filed Jul. 26, 1991, U.S. Pat. No. 5,232,678.
US Referenced Citations (11)
Foreign Referenced Citations (1)
Number |
Date |
Country |
59-97530 |
Jun 1984 |
JPX |
Continuation in Parts (2)
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Number |
Date |
Country |
Parent |
996677 |
Dec 1992 |
|
Parent |
736488 |
Jul 1991 |
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