Claims
- 1. A process for producing calcium fluoride, comprising:(a) mixing aqueous H3PO4 with aqueous H2SiF6 to form a mixture such that the concentration of H3PO4 is at least about 3 moles/liter; (b) adding phosphate rock to the mixture at a rate such that the pH of the mixture is maintained at less than about 1.0 and at a temperature sufficient to form a second mixture containing calcium fluoride and; (c) separating calcium fluoride from the second mixture.
- 2. The process of claim 1 wherein the concentration of aqueous phosphoric acid used in step (a) is 85 wt. %.
- 3. The process of claim 1 wherein the calcium fluoride separated from the second mixture has a particle size less than about 1μ.
- 4. The process of claim 1 wherein the calcium fluoride has a F:Si weight ratio of greater than about 50:1.
- 5. The process of claim 1 wherein the calcium fluoride has a F:Si weight ratio of greater than about 99:1.
- 6. The process of claim 1 wherein silica and undigested phosphate rock are removed from the second mixture to produce a suspension of the calcium fluoride in phosphoric acid.
- 7. The process of claim 6 wherein the suspension of the calcium fluoride in aqueous phosphoric acid is treated with excess sulfuric acid and heated to about 120° C. to produce nearly anhydrous hydrogen fluoride.
- 8. The process of claim 6 wherein additional phosphate rock is added to the suspension in an amount such that the ratio of Ca:F is at least about 1.3:1.
- 9. The process of claim 6 wherein the suspension is mixed with an organic solvent that is miscible with phosphoric acid.
- 10. The process of claim 9 wherein the organic solvent is selected from the group consisting of methanol, ethanol and isopropanol.
Parent Case Info
This application claims benefit of Provisional application Ser. No. 60/101,198, filed Sep. 21, 1998.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
4132765 |
Yates |
Jan 1979 |
|
5531975 |
Erickson et al. |
Jul 1996 |
|
Provisional Applications (1)
|
Number |
Date |
Country |
|
60/101198 |
Sep 1998 |
US |