Additives for mercury oxidation in coal-fired power plants
View Patent ↗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.
1. A composition, comprising:
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
an additive comprising:
ferrous iron,
ferric iron, wherein a ratio of ferric iron to ferrous iron in the additive is less than about 2:1; and
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, and 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 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 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.
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. % sulfur (dry basis 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 iron to ferrous 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.
16. The composition of claim 11 , wherein the additive comprises no more than about 66.5% iron in the form of ferric iron and wherein the additive comprises no more than about 0.1 wt. % sulfur (dry basis of the additive).
17. The composition of claim 11 , wherein at least about 10% of the iron is in the form of wustite.
18. The composition of claim 11 , 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 iron.
19. The composition of claim 11 , 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 19 , wherein the halogen-containing compound comprises fluorine and is substantially free of chlorine.
21. A composition, comprising:
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
an additive comprising:
ferrous iron,
ferric iron, and
a halogen other than chlorine.
22. The composition of claim 21 , wherein the halogen is in the form of a compound, wherein a ratio of ferric iron to ferrous iron in the additive is less than about 2:1, and wherein the additive comprises at least about 0.005 wt. % (dry basis of the additive) of the halogen-containing compound.
23. The composition of claim 21 , wherein the coal feed has a Loss on Ignition (“LOI”) of at least about 10% and comprises mercury and iron, and wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of ash from the coal).
24. The composition of claim 21 , 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).
25. The composition of claim 21 , wherein the halogen is in the form of a compound, 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.
26. The composition of claim 22 , 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.
27. The composition of claim 22 , wherein the additive comprises no more than about 66.5% iron in the form of ferric iron and wherein the additive comprises no more than about 0.1 wt. % (dry basis of the additive) sulfur.
28. The composition of claim 21 , wherein at least about 10% of the iron is in the form of wustite.
29. The composition of claim 21 , wherein the halogen is in the form of a compound, 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 iron.
30. The composition of claim 21 , wherein the halogen is in the form of a compound, 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.
31. The composition of claim 21 , wherein the halogen comprises fluorine.
32. 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) ferric and ferrous iron,
ii) no more than about 0.5 wt. % sulfur (dry basis of the additive); and
iii) at least about 0.1 wt. % (dry basis of the additive) halogen-containing compound other than a chlorine compound.
33. The composition of claim 32 , wherein the additive comprises at least about 50 wt. % (dry basis of the additive) ferric and ferrous iron, 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.
34. The composition of claim 32 , 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 iron to ferrous iron in the additive is less than about 2:1.
35. The composition of claim 32 , 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.
36. The composition of claim 34 , wherein the ratio ranges from about 0.1:1 to about 1.9:1.
37. The composition of claim 32 , wherein the additive comprises no more than about 66.5% iron in the form of ferric iron and wherein the additive comprises no more than about 0.1 wt. % sulfur (dry basis of the additive).
38. The composition of claim 32 , wherein at least about 10% of the iron is in the form of wustite.
39. The composition of claim 32 , 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 iron.
40. The composition of claim 38 , 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.
41. The composition of claim 40 , wherein the halogen-containing compound comprises fluorine and is substantially free of chlorine.