Calcium carbonate sorbent and methods of making and using same

• US 5,779,464 A
• Filed: 01/10/1996
• Issued: 07/14/1998
• Est. Priority Date: 01/10/1996
• Status: Expired due to Term

• Current Assignee: The Ohio State University Research Foundation
• Original Assignee: The Ohio State University Research Foundation
• Inventors: Ghosh-Dastidar, Abhijit, Fan, Liang-Shih, Mahuli, Suhas
• Primary Examiner(s): Caldarola, Glenn
• Assistant Examiner(s): BULLOCK, IN SUK C
• Application Number:
  US08/584,089
• Time in Patent Office: 916 Days
• Field of Search: 502/400, 502/340, 502/183, 502/514, 423/244.08, 423/165, 423/430, 423/432, 210/688
• US Class Current: 423/244.08
• CPC Class Codes: B01D 2251/404 of calcium
• CPC Class Codes: B01D 2251/606 Carbonates
• CPC Class Codes: B01D 53/508 by treating the gases with solids
• CPC Class Codes: B01J 20/043 Carbonates or bicarbonates, e.g. limestone, dolomite, aragonite
• CPC Class Codes: B01J 20/223 containing metals, e.g. organo-metallic compounds, coordination complexes
• CPC Class Codes: B01J 20/28059 being less than 100 m2/g
• CPC Class Codes: B01J 20/28071 being less than 0.5 ml/g
• CPC Class Codes: B01J 20/3085 Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
• CPC Class Codes: B01J 2220/46 Materials comprising a mixture of inorganic and organic materials materials coated or impregnated on a carrier B01J20/32
• CPC Class Codes: C01F 11/181 Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by control of the carbonation conditions
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: C22B 3/24 by adsorption on solid substances, e.g. by extraction with solid resins
• CPC Class Codes: Y02P 10/20 Recycling
• CPC Class Codes: Y10S 502/514 Process applicable either to preparing or to regenerating or to rehabilitating catalyst or sorbent

Abstract

A novel CaCO₃ sorbent with its physical properties tailored for high SO₂ removal is produced in accordance with the present invention. The surface area, porosity and the distribution of pore sizes of the sorbent have been designed and controlled to give rise to the optimum internal structure necessary for high SO₂ removal. The CaCO₃ sorbent possesses 60 m² /g surface area and 0.18 cc/g pore volume and exhibits extraordinary reactivity towards SO₂ (70% utilization in 530 milliseconds at 1080° C. and 3900 ppm SO₂ concentration) when compared with other carbonate and hydrate sorbents in our laboratory reactor system. The sorbent may be produced by precipitation in a slurry bubble column reactor system and preferably contains about 2% by weight of a surfactant which is added during its preparation and improves the properties of CaCO₃ in the course of precipitation. The high utilization of this tailored CaCO₃ sorbent makes it a very strong potential sorbent for dry sorbent injection technology.

Claims

1. A sorbent comprising:

a calcium carbonate powder comprising powder particles having an average surface area above about 30 m² /gram;

said powder particles having pores of an average pore volume, and the ratio of said average surface area to said average pore volume is in the range of at least about 200 m² /cubic centimeter.

2. A sorbent comprising:

a calcium carbonate powder comprising powder particles having an average surface area above about 40 m² /gram;

said powder particles having pores of an average pore volume, and the ratio of said average surface area to said average pore volume is in the range of from about 200 to about 350 m² /cubic centimeter.

3. A sorbent according to claim 2 wherein said average surface area is in the range above about 60 m² /gram.

4. A sorbent according to claim 2 wherein said average pore volume is in the range of above about 0.18 cubic centimeters per gram of said powder.

5. A sorbent according to claim 2 wherein said sorbent additionally comprises at least one surfactant.

6. A sorbent according to claim 5 wherein said sorbent comprises at least about 2% by weight of said at least one surfactant.

7. A sorbent according to claim 5 wherein said at least one surfactant is selected from the group consisting of a sodium salt of a polycarboxylic acid.

8. A sorbent according to claim 2 wherein said sorbent is produced by precipitation from a solution of calcium hydroxide.

9. A process for making a calcium carbonate sorbent, said process comprising the, steps of:

(a) preparing a liquid suspension of calcium (II) ion; and

(b) subjecting said liquid suspension to a flow of carbon dioxide gas for sufficient time and at sufficient temperature so as to form calcium carbonate, wherein the concentration of said liquid suspension of calcium (II) ion in the suspension of step (a) is at least about 4_sat ; and

wherein the flow rate of said flow of carbon dioxide gas is at least about 0.48 liters/minute, so as to form a calcium carbonate powder comprising powder particles having an average surface area above 30 m² /gram;

said powder particles having pores of an average pore volume, and the ratio of said average surface area to said average pore volume is in the range of at least about 200 m² /cubic centimeter.

10. A process according to claim 9 wherein said concentration of said liquid suspension of calcium (II) ion in the suspension of step (a) is at least about 16_sat.

11. A process according to claim 9 wherein the flow rate of said flow of carbon dioxide gas is at least about 2.4 liters/minute.

12. A process according to claim 9 wherein said process additionally comprises the addition of at least one surfactant during step (b).

13. A process of removing sulfur dioxide from a gaseous flow, said process comprising:

exposing said gaseous flow to a sorbent, said sorbent comprising calcium carbonate powder comprising powder particles having an average surface area above about 40 m² /gram;

said powder particles having pores of an average pore volume, and the ratio of said average surface area to said average pore volume is in the range of from about 200 to about 350 m² /cubic centimeter, for sufficient time and at sufficient temperature so as to bind said sulfur dioxide to said sorbent.

14. A process according to claim 13 wherein said average surface area is in the range above about 60 m² /gram.

15. A process according to claim 13 wherein said average pore volume is in the range of about 0.18 cubic centimeters per gram of said powder.

16. A process according to claim 13 wherein said sorbent additionally comprises at least one surfactant.

17. A process according to claim 13 wherein said sorbent comprises at least 2% by weight of said at least one surfactant.

18. A process according to claim 13 wherein said at least one surfactant is selected from the group consisting of sodium salts of a polycarboxylic acid and anionic surfactants.

19. A process according to claim 13 wherein said sorbent is produced by precipitation from a solution of calcium hydroxide.

20. A process of removing at least one heavy metal from a sample, said process comprising:

exposing said sample to a sorbent, said sorbent comprising calcium carbonate powder comprising powder particles having an average surface area above about 40 m² /gram;

said powder particles having pores of an average pore volume, and the ratio of said average surface area to said average pore volume is in the range of from about 200 to about 350 m² /cubic centimeter, for sufficient time and at sufficient temperature so as to bind said at least one heavy metal to said sorbent.

21. A process according to claim 20 wherein said average surface area is in the range above about 60 m² /gram.

22. A process according to claim 20 wherein said average pore volume is in the range of about 0.18 cubic centimeters per gram of said powder.

23. A process according to claim 20 wherein said sorbent additionally comprises at least one surfactant.

24. A process according to claim 23 wherein said sorbent comprises at least 2% by weight of said at least one surfactant.

25. A process according to claim 23 wherein said at least one surfactant is selected from the group consisting of sodium salts of a polycarboxylic acid and anionic surfactants.