Low sulfur coal additive for improved furnace operation

• US 20020184817A1
• Filed: 07/30/2002
• Published: 12/12/2002
• 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: Johnson, Stephen Allen, Wurster, John, Comer, John Philip
• Granted Patent: US 7,332,002 B2
• Time in Patent Office: Days
• US Class Current: 44/620
• CPC Class Codes: C10L 10/04 for minimising corrosion or incrustation
• 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
• CPC Class Codes: Y02E 20/12 Heat utilisation in combustion or incineration of waste

Abstract

The present invention is directed to additives for coal-fired furnaces, particularly furnaces using a layer of slag to capture coal particles for combustion. The additive(s) include iron, mineralizer(s), handling aid(s), flow aid(s), and/or abrasive material(s). The iron and mineralizers can lower the melting temperature of ash in low-iron, high alkali coals, leading to improved furnace performance.

Claims

1. A method for combusting coal, comprising:

providing a coal-containing feed material to a coal combustion chamber;

contacting the feed material with an iron-containing additive, wherein the iron-containing additive is in the form of a free-flowing particulate having a P₉₀ size of no more than about 300 microns; and

melting at least a portion of the coal-containing feed material and iron-containing additive to form a slag layer on at least a portion of a surface of the combustion chamber, whereby coal in the coal-containing feed material is captured by the slag layer and combusted.

2. The method of claim 1, wherein the coal-containing feed material comprises ash and less than about 1 wt. % (dry basis of the coal-containing feed material) sulfur, with the ash containing less than about 10 wt. % (dry basis of the ash) iron, and at least about 20 wt. % (dry basis of the ash) alkali.

3. The method of claim 1, wherein the additive further comprises wustite.

4. The method of claim 1, wherein the coal combustion chamber is part of a cyclone furnace and wherein the coal-containing feed material includes coal particles entrained in an oxygen-containing gas and the coal particles have a P₉₀ size of no more than about 0.25 inches.

5. The method of claim 1, wherein the iron-containing additive comprises at least about 50 wt. % (dry basis of the additive) iron and at least about 1 wt. % (dry basis of the additive) mineralizer.

6. The method of claim 5, wherein the mineralizer is zinc and the iron-containing additive further comprises at least one of a flow aid and abrasive material.

7. The method of claim 1, wherein an injection rate of the iron-containing additive into the combustion chamber ranges from about 10 to about 50 lb/ton coal.

8. A method for combusting coal, comprising:

inputting a coal-containing feed material to a coal combustion chamber;

contacting the feed material with an iron-containing additive, wherein the iron-containing additive comprises at least about 50 wt. % (dry basis of the additive) iron and at least about 1 wt. % (dry basis of the additive) mineralizer; and

melting at least a portion of the coal-containing feed material and iron-containing additive to form a slag layer on at least a portion of a surface of the combustion chamber, whereby coal in the coal-containing feed material is captured by the slag layer and combusted.

9. The method of claim 8, wherein the coal-containing feed material comprises ash and less than about 1.5 wt. % (dry basis of the coal-containing feed material) sulfur, with the ash containing less than about 10 wt. % (dry basis of the ash) iron, and at least about 15 wt. % (dry basis of the ash) calcium.

10. The method of claim 8, wherein the mineralizer is a zinc compound and the coal-containing feed material includes coal particles entrained in an oxygen-containing gas and the coal particles have a P₉₀ size of no more than about 0.25 inch.

11. The method of claim 8, wherein the coal combustion chamber is part of a cyclone furnace.

12. The method of claim 8, wherein the iron-containing additive is in the form of a free-flowing particulate having a P₉₀ size of no more than about 300 microns.

13. The method of claim 8, wherein the iron-containing additive is a byproduct of steel or iron manufacturer and comprises wustite.

14. The method of claim 8, wherein an injection rate of the iron-containing additive into the combustion chamber ranges from about 10 to about 50 lb/ton coal and the iron-containing additive further comprises at least one of a flow aid and an abrasive material.

16. The method of claim 15, wherein the additive comprises at least about 1 wt. % (dry basis of the additive) mineralizer.

17. The method of claim 15, wherein the mineralizer is a zinc compound, wherein the coal-containing feed material includes coal particles entrained in an oxygen-containing gas, wherein the coal particles have a P₉₀ size of no more than about 0.25 inch, and wherein the coal-containing feed material comprises ash and less than about 1.5 wt. % (dry basis of the coal-containing feed material) sulfur, with the ash containing less than about 10 wt. % (dry basis of the ash) iron, and at least about 15 wt. % (dry basis of the ash) calcium.

18. The method of claim 15, wherein the coal combustion chamber is part of a cyclone furnace and at least some of the iron is in the form of wustite.

19. The method of claim 15, wherein the iron-containing additive is in the form of a free-flowing particulate having a P₉₀ size of no more than about 300 microns.

20. The method of claim 15, wherein the iron-containing additive is a byproduct of steel or iron manufacturer and comprises wustite.

15. A method for combusting coal, comprising:

introducing a coal-containing feed material to a coal combustion chamber;

contacting the feed material with an iron-containing additive, wherein the iron-containing additive comprises at least about 50 wt. % (dry basis of the additive) iron and the iron is in the form of a mixture of ferrous and ferric oxides; and

melting at least a portion of the coal-containing feed material and iron-containing additive to form a slag layer on at least a portion of a surface of the combustion chamber, whereby coal in the coal-containing feed material is captured by the slag layer and combusted.

21. An additive for a coal feed to a cyclone furnace, comprising:

iron in an amount of at least about 50 wt. % (dry basis of the additive), wherein the iron comprises at least about 33.5% of the iron is in the form of iron having a valence of +2 or lower and wherein the additive is in the form of a free-flowing particulate having a P₉₀ size of no more than about 300 microns.

22. The additive of claim 21, wherein the iron content ranges from about 50 to about 99 wt. % (dry basis of the additive) and further comprising a mineralizer in an amount of at least about 1 wt. % (dry basis of the additive).

23. The additive of claim 22, wherein the mineralizer is zinc and the zinc content ranges from about 1 to about 8 wt. % (dry basis of the additive).

24. The additive of claim 21, further comprising at least one of:

(a) a flow aid in an amount of at least about 0.1 wt. % (dry basis of the additive) and (b) an abrasive material in an amount of at least about 1 wt. % (dry basis of the additive).

26. The material of claim 25, wherein the additive is in the form of a free-flowing particulate having a P₉₀ size of no more than about 300 microns.

27. The material of claim 25, wherein the iron content of the additive ranges from about 50 to about 99 wt. % (dry basis of the additive), wherein the coal and additive are entrained in an airstream, and wherein the additive includes wustite.

28. The material of claim 25, wherein the mineralizer content of the additive ranges from about 1 to about 8 wt. % (dry basis of the additive).

29. The material of claim 25, wherein the material comprises at least about 15 wt. % (dry basis of the coal) alkali and no more than about 1.5 wt. % (dry basis of the coal) sulfur.

30. The material of claim 25, wherein the coal includes from about 3 to about 20 wt. % ash (dry basis of the coal).

31. The material of claim 25, further comprising at least one of a flow aid and an abrasive material.

25. A coal-containing feed material for a furnace, comprising:

coal; and

an additive, wherein the additive includes;

iron in an amount of at least about 50 wt. % (dry basis of the additive) and

a mineralizer in an amount of at least about 1 wt. % (dry basis of the additive).

32. A slag layer in a coal-burning furnace, comprising:

at least about 5 wt. % (dry basis of the slag layer) coal;

iron in an amount of at least about 15 wt. % (dry basis of the slag layer); and

a mineralizer in an amount of at least about 1 wt. % (dry basis of the slag layer).

33. The slag layer of claim 32, wherein the slag layer is in the form of a free-flowing liquid having a viscosity of no more than about 250 Poise.

34. The slag layer of claim 32, wherein the iron content ranges from about 15 to about 30 wt. % (dry basis of the slag layer).

35. The slag layer of claim 32, wherein the mineralizer is zinc and the zinc content ranges from about 1 to about 8 wt. % (dry basis of the slag layer).

36. The slag layer of claim 32, wherein the slag layer comprises at least about 15 wt. % calcium and no more than about 1 wt. % sulfur (dry basis of the slag layer).

37. The slag layer of claim 32, further comprising at least about 20 wt. % silica oxides (dry basis of the slag layer).

38. The slag layer of claim 37, wherein and further comprising from about 13 to about 20 wt. % aluminum oxides (dry basis of the slag layer);

from about 18 to about 35 wt. % calcium oxides (dry basis of the slag layer).

40. The solid byproduct of claim 39, wherein the iron content ranges from about 15 to about 30 wt. % (dry basis of the byproduct).

39. A solid byproduct of coal combustion, comprising:

iron in an amount of at least about 15 wt. % (dry basis of the byproduct);

zinc in an amount of at least about 1 wt. % (dry basis of the byproduct);

silica compounds in an amount of at least about 2 wt. % (dry basis of the byproduct);

aluminum compounds in an amount of at least about 20 wt. % (dry basis of the byproduct); and

calcium compounds in an amount of at least about 15 wt. % (dry basis of the byproduct).