Method of removing sulfur trioxide from a flue gas stream

• US 20070081936A1
• Filed: 09/15/2005
• Published: 04/12/2007
• Est. Priority Date: 09/15/2005
• Status: Active Grant

• Current Assignee: Solvay Chemicals Incorporated (Solvac SA)
• Original Assignee: Solvay Chemicals Incorporated (Solvac SA)
• Inventors: Maziuk, John
• Granted Patent: US 7,481,987 B2
• Time in Patent Office: Days
• US Class Current: 423/244.80
• CPC Class Codes: B01D 2257/302 Sulfur oxides
• CPC Class Codes: B01D 2257/404 Nitrogen oxides other than dinitrogen oxide
• CPC Class Codes: B01D 53/505 in a spray drying process
• CPC Class Codes: B01D 53/508 by treating the gases with solids
• CPC Class Codes: Y10S 423/05 Automatic, including computer, control
• CPC Class Codes: Y10S 423/08 Corrosion or deposition inhibiting

Abstract

A method of removing SO₃ from a flue gas stream includes providing a reaction compound selected from the group consisting of sodium carbonate, sodium bicarbonate, sodium sesquicarbonate, and mixtures thereof. The reaction compound is injected into the flue gas stream. The temperature of the flue gas is between about 500° F. and about 850° F. The reaction compound is maintained in contact with the flue gas for a time sufficient to react a portion of the reaction compound with a portion of the SO₃ to reduce the concentration of the SO₃ in the flue gas stream.

Claims

1. A method of removing SO₃ from a flue gas stream comprising SO₃, comprising:

providing a reaction compound selected from the group consisting of sodium carbonate, sodium bicarbonate, sodium sesquicarbonate, and mixtures thereof;

injecting the reaction compound into the flue gas stream, wherein the temperature of the flue gas is between about 500°

F. and about 850°

F.; and

maintaining the reaction compound in contact with the flue gas for a time sufficient to react a portion of the reaction compound with a portion of the SO₃ to reduce the concentration of the SO₃ in the flue gas stream.

2. The method of claim 1 further comprising providing an NO_x removal system upstream of the location where the reaction compound is injected.

3. The method of claim 1 wherein the flue gas stream comprises at least about 3 ppm SO₃ upstream of the location where the reaction compound is injected.

4. The method of claim 3 wherein the flue gas stream comprises between about 10 ppm and about 200 ppm SO₃ upstream of the location where the reaction compound is injected.

5. The method of claim 1 wherein the reaction compound is sodium sesquicarbonate.

6. The method of claim 1 wherein the reaction compound is provided in the form of particles with a mean particle size of less than about 40 micron.

7. The method of claim 6 wherein the mean particle size of the reaction compound is between about 10 micron and about 40 micron.

8. The method of claim 6 wherein the mean particle size of the reaction compound is between about 24 micron and about 28 micron.

9. The method of claim 1 wherein the temperature of the flue gas is greater than about 550°

F.

10. The method of claim 1 wherein the temperature of the flue gas is less than about 750°

F.

11. The method of claim 1 wherein the temperature of the flue gas is between about 500°

F. and about 750°

F.

12. The method of claim 1 wherein the reaction compound is injected at a rate with respect to the flow rate of the SO₃ to provide a normalized stoichiometric ratio of sodium to sulfur of between about 1.0 and 1.5.

13. The method of claim 1 wherein the reaction compound is injected as a dry material.

14. The method of claim 1 further comprising milling the reaction compound to a desired mean particle size at a location proximate the flue gas stream.

15. The method of claim 1 wherein the reaction product of the reaction compound and the SO₃ is selected from the group consisting of Na₂SO₄, Na₂S₂O₇, and mixtures thereof.

16. The method of claim 1 wherein the flue gas stream further comprises SO₂, the method further comprising maintaining the reaction compound in contact with the flue gas for a time sufficient to react a portion of the reaction compound with a portion of the SO₂ to reduce the concentration of the SO₂ in the flue gas stream.

17. A method of removing SO₃ from a flue gas stream, comprising:

providing a source of trona;

injecting the trona as a dry granular material into the flue gas stream, wherein the temperature of the flue gas is between about 500°

F. and about 850°

F. and wherein the flue gas stream comprises at least about 3 ppm SO₃; and

maintaining the trona in contact with the flue gas for a time sufficient to react a portion of the trona with a portion of the SO₃ to reduce the concentration of the SO₃ in the flue gas stream.

18. The method of claim 17 wherein the flue gas stream comprises between about 10 ppm and about 200 ppm SO₃ upstream of the location where the trona is injected.

19. The method of claim 17 wherein the trona is provided in the form of particles with a mean particle size of between about 10 micron and about 40 micron.

20. The method of claim 17 wherein the temperature of the flue gas is between about 500°

F. and about 750°

F.

21. The method of claim 17 wherein the reaction product of the reaction compound and the SO₃ is selected from the group consisting of Na₂SO₄, Na₂S₂O₇, and mixtures thereof.

22. The method of claim 17 further comprising adjusting the flue gas temperature upstream of the trona to obtain the desired flue gas temperature where the trona is injected.

23. The method of claim 22 wherein the adjusting further comprises introducing ambient air into the flue gas stream and monitoring the flue gas temperature where the trona is injected.

24. The method of claim 22 wherein the adjusting further comprises controlling the flow of a material through a heat exchanger in communication with the flue gas.

25. A method of removing SO₃ from a flue gas stream comprising at least about 3 ppm SO₃, comprising:

providing a source of trona having a mean particle size between about 10 micron and about 40 micron;

introducing ambient air in the flue gas stream to reduce the temperature of the flue gas to less than about 365°

F.;

injecting the trona as a dry granular material into the flue gas stream, wherein the temperature of the flue gas is between about 275°

F. and about 365°

F.; and

maintaining the trona in contact with the flue gas for a time sufficient to react a portion of the sodium sorbent with a portion of the SO₃ to reduce the concentration of the SO₃ in the flue gas stream, wherein the reaction product is selected from solid phase Na₂SO₄, solid phase NaHSO₄, and mixtures thereof.

26. The method of claim 25 wherein the flue gas stream comprises between about 10 ppm and about 200 ppm SO₃ upstream of the location where the trona is injected.