ADDITIVES FOR MERCURY OXIDATION IN COAL-FIRED POWER PLANTS

• US 20110030592A1
• Filed: 05/21/2010
• Published: 02/10/2011
• Est. Priority Date: 06/26/2000
• Status: Active Grant

• Current Assignee: ADA-ES, Inc. (Advanced Emissions Solutions, Inc.)
• Original Assignee: ADA Environmental Solutions, LLC (Advanced Emissions Solutions, Inc.)
• Inventors: Sjostrom, Sharon, French, Nina Bergan, Durham, Michael D., Baldrey, Kenneth E., Corner, John Philip, Johnson, Stephen Allen, Wurster, John
• Granted Patent: US 8,439,989 B2
• Time in Patent Office: Days
• US Class Current: 110/342
• CPC Class Codes: C10L 5/00 Solid fuels produced by solidifying fluid fuels C10L7/00
• CPC Class Codes: C10L 9/10 by using additives
• CPC Class Codes: F23G 2202/20 to temperatures melting waste
• CPC Class Codes: F23G 2203/30 Cyclonic combustion furnace
• CPC Class Codes: F23J 7/00 Arrangement of devices for supplying chemicals to fire
• CPC Class Codes: F23J 9/00 Preventing premature solidification of molten combustion residues
• CPC Class Codes: F23K 2201/505 with additives

Abstract

The present invention is directed to an additive, primarily for low sulfur and high alkali coals, that includes a transition metal and optionally a halogen to effect mercury oxidation.

Claims

1. A composition, comprising:

(a) a low sulfur and high alkali coal, the coal feed comprises less than about 1.5 wt. % sulfur (dry basis of the coal) and at least about 20 wt. % (dry basis of ash from the coal) alkali; and

(b) an additive comprising;

i) ferrous iron,

ii) ferric iron, wherein a ratio of ferric and higher valence iron to ferrous and lower valence iron in the additive is less than about 2;

1; and

iii) a halogen-containing compound other than a chlorine compound, the additive comprising at least about 0.005 wt. % (dry basis of the additive) of the halogen-containing compound.

2. The composition of claim 1, wherein the coal feed has a Loss on Ignition (“

LOI”

) of at least about 10% and comprises mercury and iron, wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of ash from the coal).

3. The composition of claim 1, wherein the coal comprises iron and wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of ash from the coal).

4. The composition of claim 1, wherein the additive comprises no more than about 0.5 wt. % (dry basis of the additive) sulfur, wherein the composition comprises at least about 0.5 wt. % (dry basis of the composition) iron, wherein the composition comprises at least about 0.005 wt. % (dry basis of the composition) halogen-containing compound, and wherein the additive comprises at least about 50 wt. % (dry basis of the additive) iron.

5. The composition of claim 1, wherein the ratio ranges from about 0.1:

1 to about 1.9;

1 and wherein the additive comprises at least about 50 wt. % (dry basis of the additive) iron.

6. The composition of claim 1, wherein the additive comprises no more than about 66.5% iron in the form of ferric and higher valence iron and wherein the additive comprises no more than about 0.1 wt. % (dry basis of the additive) sulfur.

7. The composition of claim 1, wherein at least about 10% of the iron is in the form of wustite.

8. The composition of claim 1, wherein the additive comprises at least about 1 wt. % of the halogen-containing compound and wherein at least about 33.5 wt. % (dry basis of the additive) of the iron in the additive is in the form of ferrous and lower valence iron.

9. The composition of claim 7, wherein from about 15 to about 50% of the iron is in the form of wustite and wherein the additive comprises from about 0.5 to about 15 wt. % of the halogen-containing compound.

10. The composition of claim 9, wherein the halogen-containing compound comprises fluorine.

16. The composition of claim 1, wherein the additive comprises no more than about 66.5% iron in the form of ferric and higher valence iron and wherein the additive comprises no more than about 0.1 wt. % (dry basis of the additive) sulfur.

17. The composition of claim 1, wherein at least about 10% of the iron is in the form of wustite.

18. The composition of claim 1, wherein the additive comprises at least about 1 wt. % of the halogen-containing compound and wherein at least about 33.5 wt. % (dry basis of the additive) of the iron in the additive is in the form of ferrous and lower valence iron.

19. The composition of claim 7, wherein from about 15 to about 50% of the iron is in the form of wustite and wherein the additive comprises from about 0.5 to about 15 wt. % of the halogen-containing compound.

20. The composition of claim 9, wherein the halogen-containing compound comprises fluorine and is substantially free of chlorine.

11. A composition, comprising:

(a) a low sulfur and high alkali coal, the coal feed comprises less than about 1.5 wt. % sulfur (dry basis of the coal) and at least about 20 wt. % (dry basis of ash from the coal) alkali; and

(b) an additive comprising;

i) at least about 50 wt. % (dry basis of the additive) ferric and ferrous iron,

ii) no more than about 0.5 wt. % (dry basis sulfur of the additive); and

iii) at least about 0.1 wt. % (dry basis of the additive) halogen-containing compound other than a chlorine compound.

12. The composition of claim 11, wherein the coal feed has a Loss on Ignition (“

LOI”

) of at least about 10%, wherein the coal feed comprises mercury and iron, wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of ash from the coal), wherein the composition comprises at least about 0.5 wt. % (dry basis of the composition) iron, and wherein the composition comprises at least about 0.005 wt. % (dry basis of the composition) halogen-containing compound.

13. The composition of claim 11, wherein the coal comprises iron, wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of ash from the coal), and wherein a ratio of ferric and higher valence iron to ferrous and lower valence iron in the additive is less than about 2:

1.

14. The composition of claim 11, wherein the additive comprises no more than about 0.1 wt. % (dry basis of the additive) sulfur and wherein the additive comprises at least about 50 wt. % (dry basis) iron.

15. The composition of claim 13, wherein the ratio ranges from about 0.1:

1 to about 1.9;

1.

21. A method, comprising:

(a) providing a coal feed, the coal feed comprising sulfur, alkali, and iron, wherein the sulfur content of the coal feed is no more than about 1.5 wt. % (dry basis of the coal) and the alkali content of the coal feed is at least about 20 wt. % (dry basis of ash from the coal);

(b) combusting the coal feed, in the presence of an added halogen-containing compound, to form a slag;

(c) contacting the coal feed, prior to combustion, with a free-flowing additive, the free-flowing additive comprising at least about 50 wt. % (dry basis additive) iron; and

(d) collecting the slag, wherein the slag comprises from about 20 to about 35 wt. % (dry basis slag) silica oxides, from about 13 to about 20 wt. % (dry basis slag) aluminum oxides, and from about 18 to about 35 wt. % (dry basis slag) calcium oxides.

22. The method of claim 21, wherein the iron content of the coal feed is about 10 wt. % (dry basis of ash from the coal) or less, wherein the coal feed has a Loss on Ignition (“

LOI”

) of at least about 10%, wherein the coal feed comprises mercury, wherein, when the additive is contacted with the flue gas, the flue gas has a temperature of more than about 150°

C., wherein the halogen promotes oxidation of the elemental mercury, wherein the coal feed comprises no more than about 500 ppm halogens.

23. The method of claim 22, wherein the coal feed comprises no more than about 100 ppm chlorine and no more than about 10 ppm bromine and wherein the additive further comprises at least about 0.1 wt. % (dry basis additive) of a halogen-containing compound.

24. The method of claim 21, wherein the coal feed is combusted in a cyclone boiler, wherein the additive comprises ferric and ferrous iron, wherein a ratio of ferric iron to ferrous iron is less than about 2:

1, and wherein the coal feed is a low sulfur coal.

25. The method of claim 21, wherein the additive is contacted with the coal feed prior to combustion and wherein the additive comprises ferric and ferrous iron, wherein a ratio of ferric iron to ferrous iron ranges from about 0.1:

1 to about 1.9;

1.

26. The method of claim 21, wherein the additive comprises ferric and ferrous iron, wherein the additive comprises at least about 33.5.% ferrous iron, wherein at least about 10% of the iron is in the form of wustite, and wherein the additive comprises no more than about 0.1 wt. % (dry basis additive) sulfur.

27. The method of claim 21, wherein the coal feed comprises no more than about 100 ppm chlorine and no more than about 10 ppm bromine, wherein the coal feed has a Loss on Ignition (“

LOI”

) of at least about 10% and comprises mercury, alkali, and iron, wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of ash from the coal) as Fe₂O₃, the alkali content of the coal feed is at least about 20 wt. % (dry basis of ash from the coal) alkali, wherein the coal feed comprises no more than about 500 ppm halogens, and wherein the additive comprises a transition metal other than iron and a halogen.

28. A method, comprising:

(a) providing a coal feed, the coal feed comprising sulfur, alkali, and iron; and

(b) combusting the coal feed, in a furnace, in the presence of an added halogen-containing compound, and at a combustion temperature ranging from about 2,600 to about 3,000°

F., to form a flue gas containing ash, wherein the sulfur content of the coal feed is no more than about 1.5 wt. % (dry basis of the coal) and the alkali content of the ash is at least about 20 wt. % (dry basis of the ash).

29. The method of claim 28, wherein the coal feed is contacted with the added halogen-containing compound before introduction of the coal feed to the furnace and wherein the coal ash comprises at least about 15 wt. % (dry basis of the ash) CaO.

30. The method of claim 28, wherein the added halogen-containing compound is a part of an additive and wherein the additive comprises at least about 50 wt. % (dry basis additive) iron.

31. The method of claim 28, wherein the combustion step (b) produces a slag and further comprising:

(c) collecting the slag, wherein the slag comprises from about 20 to about 35 wt. % (dry basis slag) silica oxides, from about 13 to about 20 wt. % (dry basis slag) aluminum oxides, and from about 18 to about 35 wt. % (dry basis slag) calcium oxides.

32. The method of claim 30, wherein the iron content of the coal feed is about 10 wt. % (dry basis of the ash) or less, wherein the coal feed has a Loss on Ignition (“

LOI”

) of at least about 10%, wherein the coal feed comprises mercury, wherein, when the additive is contacted with the flue gas, the flue gas has a temperature of more than about 150°

C., wherein the halogen promotes oxidation of the elemental mercury, wherein the coal feed comprises no more than about 500 ppm halogens.

33. The method of claim 32, wherein the coal feed comprises no more than about 100 ppm chlorine and no more than about 10 ppm bromine and wherein the additive further comprises at least about 0.1 wt. % (dry basis additive) of a halogen-containing compound.

34. The method of claim 30, wherein the coal feed is combusted in a cyclone boiler, wherein the additive comprises ferric and ferrous iron, wherein a ratio of ferric iron to ferrous iron is less than about 2:

1, and wherein the coal feed is a low sulfur coal.

35. The method of claim 30, wherein the additive is contacted with the coal feed prior to combustion and wherein the additive comprises ferric and ferrous iron, wherein a ratio of ferric iron to ferrous iron ranges from about 0.1:

1 to about 1.9;

1.

36. The method of claim 30, wherein the additive comprises ferric and ferrous iron, wherein the additive comprises at least about 33.5.% ferrous iron, wherein at least about 10% of the iron is in the form of wustite, and wherein the additive comprises no more than about 0.1 wt. % (dry basis additive) sulfur.

37. The method of claim 30, wherein the coal feed comprises no more than about 100 ppm chlorine and no more than about 10 ppm bromine, wherein the coal feed has a Loss on Ignition (“

LOI”

) of at least about 10% and comprises mercury, alkali, and iron, wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of the ash) as Fe₂O₃, the alkali content of the coal feed is at least about 20 wt. % (dry basis of the ash) alkali, wherein the coal feed comprises no more than about 500 ppm halogens, and wherein the additive comprises a transition metal other than iron and a halogen.