Process for manufacture of purified alkaline earth metal carbonate

Abstract

Process for manufacture of purified alkaline earth metal carbonate The invention concerns a process for the manufacture of a purified alkaline earth metal carbonate, the purified alkaline earth metal carbonate obtainable by said process, and its use in the manufacture of products and devices in the field of electronics and glass. The process comprises the steps of calcinating the alkaline earth metal carbonate with an aqueous phase comprising a salt. The alkaline earth metal carbonate might be barium carbonate or strontium carbonate.

Claims

1. A process for the manufacture of a purified alkaline earth carbonate, comprising the steps of a) calcining an alkaline earth metal carbonate, wherein the alkaline earth metal carbonate is BaCO.sub.3 and/or SrCO.sub.3, b) washing the calcinated alkaline earth metal carbonate with an aqueous phase comprising a metal salt.

2. The process according to claim 1, wherein the alkaline earth metal carbonate of step a) has a particle size D90 value of from 700 to 1100 m and a particle size D50 value of from 350 to 750 m after calcination.

3. The process according to claim 1, wherein the calcination procedure of step a) is performed at a temperature of from 150 to 1000 C.

4. The process according to claim 1, wherein the metal salt comprised in the aqueous phase of step b) is a carbonate, chloride, bromide, phosphate or citrate.

5. The process according to claim 4, wherein the metal salt is an alkali metal carbonate.

6. The process according to claim 5, wherein the metal salt is sodium carbonate.

7. The process according to claim 4, wherein the metal salt comprised in the aqueous phase of step b) is a carbonate.

8. The process according to claim 1, wherein the content of metal salt in the aqueous phase of step b) corresponds to from 1 to 200 equivalents, wherein 1 equivalent is one mole metal salt cation, if the metal salt cation is divalent, or is two moles metal salt cation, if the metal salt cation is monovalent, per mole of MSO.sub.4, wherein M is an alkaline earth metal, formed by oxidation of all sulfur impurities in the calcination product of step a).

9. The process according to claim 8, wherein the content of metal salt in the aqueous phase of step b) corresponds to from 10-20 equivalents.

10. The process according to claim 1, wherein step b) is repeated.

11. The process according to claim 1, wherein the alkaline earth metal carbonate provided to the calcination procedure of step a) has a total sulfur content of from 200 to 1700 ppm.

12. The process according to claim 1, wherein the alkaline earth metal carbonate after step b) has a total sulfur content of from 0.1 to 200 ppm.

13. The process according to claim 1, wherein the alkaline earth metal carbonate provided to the calcination procedure of step a) has a particle size D90 value of from 12 to 30 m and a has a particle size D50 value of from 2,5 to 9 m.

Description

EXAMPLE

(1) Calcination of Alkaline Earth Metal Carbonate:

(2) CO2 was passed through a solution of MS, obtained by reduction of the corresponding sulfate. The resulting MCO3 was filtered, washed with water and the washing water was separated from MCO3. The recovered MCO3 was heated in a rotary kiln in an atmosphere containing oxygen to about 800 C. The calcination product was cooled to ambient temperature.

(3) Washing of the Calcinated Alkaline Earth Metal Carbonate:

(4) A 100 g sample of product was inserted into 500 mL of a solution of soda containing 10-20 stoichiometric equivalents calculated on the sulfur content of the calcinated MCO3 in a beaker glass. The suspension was stirred at 25 C. and 250 rpm for 15 minutes and then filtrated by suction filter. The residue was washed three times with the threefold volume (compared to the MCO3 volume) of hot pure water and dried at 130 C. in a drying cabinet.

(5) TABLE-US-00001 Initial MSO4 Final MSO4 Final Sulfur Raw Material content Content content BaCO3 Granules 0.26% 0.03% 40 ppm BaCO3 Granules 0.35% 0.04% 55 ppm BaCO3 Powder 0.49% 0.33% 450 ppm (not calcinated, comparative example) SrCO3 Granules 0.36% 0.01% 15 ppm
Washing of the Calcinated Alkaline Earth Metal Carbonate at different Temperatures: A 100 g sample of product was inserted into 500 mL of a solution of soda containing 10-20 stoichiometric equivalents calculated on the sulfur content of the calcinated MCO3 in a beaker glass. The suspension was stirred at indicated temperature and 250 rpm for 15 minutes and then filtered by suction filter. The residue was washed three times with the threefold volume (compared to the MCO3 volume) of hot pure water and dried at 160 C. in a drying cabinet.

(6) Initial Sulfur content calcinated BaCO3: 275 ppm

(7) Final Sulfur content calcinated BaCO3, after washing at 20 and drying: 140 ppm

(8) Final Sulfur content calcinated BaCO3, after washing at 90 and drying: 74 ppm