Low sulfur coal additive for improved furnace operation
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.
1. A method of preparing a solid fuel for combustion, comprising:
contacting an iron-containing particulate additive comprising a plurality of particles with water to water-wet surfaces of the particles;
drying the water-wetted surfaces of the particles to cohesively bond the water-wetted surfaces of the particles and form a plurality of cohesively bonded iron-containing particulates; and
contacting coal with the plurality of cohesively bonded iron-containing particulates by one or more of mixing the plurality of cohesively bonded iron-containing particulates with the coal and adding the plurality of cohesively bonded iron-containing particulates to the coal.
2. The method of claim 1 , wherein the iron-containing particulate additive is hydrophilic and wherein the contacting of the iron-containing particulate additive with water forms a slurry of the iron-containing particulates in water.
3. The method of claim 1 , wherein step of contacting the iron-containing particulate additive with water further includes contacting the iron-containing particulate additive with an adhesive and wherein the adhesive comprises one or more organic adhesives, one or more inorganic adhesives, or a mixture of organic and inorganic adhesives.
4. The method of claim 1 , further comprising:
contacting a flow aid with the plurality of cohesively bonded iron-containing particulates, wherein the flow aid substantially reduces one or more of particle-to-particle attraction and stickiness of the plurality of cohesively bonded iron-containing particulates.
5. The method of claim 1 , wherein the iron-containing particulate additive comprises both ferrous and ferric iron.
6. The method of claim 5 , wherein the iron-containing particulate additive has a ratio of ferric to ferrous iron from about 0.1:1 to about 1.95:1.
7. The method of claim 5 , wherein at least 10% of the iron in the iron-containing particulate additive is in a form of wustite.
8. The method of claim 1 , wherein the plurality of cohesively bonded iron-containing particulates have a P 90 size of no more than about 300 microns.
9. The method of claim 1 , wherein the iron-containing particulate additive further comprises a mineralizer and wherein the mineralizer reduces a temperature at which the iron-containing particulate additive sinters.
10. The method of claim 9 , wherein the mineralizer is zinc oxide.
11. The method of claim 1 , wherein the iron-containing particulate additive has no more than about 0.5 wt % (dry basis) sulfur.
12. The method of claim 1 , wherein the iron-containing particulate additive comprises at least about 50 wt % (dry basis) iron.
13. The method of claim 1 , wherein a cohesive layer is formed on the water-wetted surfaces of the particles and wherein the cohesive layer substantially eliminates fugitive dust emissions from the iron-containing particulate additive.
14. The method of claim 1 , wherein the iron-containing particulate additive comprises at least one of mill scale fines from steel production and dust from blast furnace gas cleaning equipment.
15. The method of claim 9 , wherein the mineralizer comprises at least one of calcium, magnesium, manganese fluorides, and sulfites.
16. The method of claim 9 , wherein the mineralizer is present in an amount from about 0.5 to about 15 wt. % (dry basis).
17. A method of preparing a solid fuel for combustion, comprising:
contacting an iron-containing additive comprising a plurality of particles with water to water-wet surfaces of the particles;
drying the water-wetted surfaces of the particles to cohesively bond the water-wetted surfaces of the particles and form a plurality of cohesively bonded iron-containing particulates; and
mixing coal with the plurality of cohesively bonded iron-containing particulates,
wherein the iron-containing additive comprises (i) at least about 50 wt % (dry basis) ferrous and ferric iron, wherein a ratio of ferric iron to ferrous iron in the iron-containing additive is less than about 2:1, and (ii) from about 0.5 to about 15 wt. % (dry basis) of a mineralizer.
18. The method of claim 17 , wherein the mineralizer is zinc oxide.
19. A method of preparing a solid fuel for combustion, comprising:
contacting an iron-containing additive comprising a plurality of particles with water to water-wet surfaces of the particles;
drying the water-wetted surfaces of the particles to cohesively bond the water-wetted surfaces of the particles and form a plurality of cohesively bonded iron-containing particulates, wherein a cohesive layer is formed on the water-wetted surfaces of the particles; and
adding the plurality of cohesively bonded iron-containing particulates to coal,
wherein the iron-containing additive comprises (i) at least about 50 wt % (dry basis) ferrous and ferric iron, wherein a ratio of ferric iron to ferrous iron in the iron-containing additive is less than about 2:1, and (ii) a mineralizer, wherein the mineralizer reduces a temperature at which the iron-containing additive sinters.
20. The method of claim 19 , wherein the mineralizer comprises zinc oxide.
21. A method of preparing a solid fuel for combustion, comprising:
contacting an iron-containing additive comprising a plurality of particles with water to water-wet surfaces of the particles;
drying the water-wetted surfaces of the particles to cohesively bond the water-wetted surfaces of the particles to one another and form a plurality of cohesively bonded iron-containing particulates; and
contacting coal with the plurality of cohesively bonded iron-containing particulates,
wherein the plurality of cohesively bonded iron-containing particulates comprises at least one of mill scale fines from steel production and dust from blast furnace gas cleaning equipment.
22. The method of claim 21 , wherein the plurality of cohesively bonded iron-containing particulates have a P 90 size of no more than about 300 microns.
23. The method of claim 21 , wherein the iron-containing additive further comprises a mineralizer and wherein the mineralizer reduces a temperature at which the iron-containing additive sinters.
24. The method of claim 23 , wherein the mineralizer is zinc oxide.
25. The method of claim 21 , wherein the iron-containing additive comprises at least about 50 wt % (dry basis) iron.
26. A method of preparing a solid fuel for combustion, comprising:
contacting an iron-containing additive comprising a plurality of particles with water to water-wet surfaces of the particles;
drying the water-wetted surfaces of the particles to cohesively bond the water-wetted surfaces of the particles to each other and form a plurality of cohesively bonded iron-containing particulates; and
contacting coal with the plurality of cohesively bonded iron-containing particulates,
wherein the iron-containing additive further comprises a mineralizer comprising at least one of calcium, magnesium, manganese fluorides, and sulfites and wherein the mineralizer reduces a temperature at which the iron-containing additive sinters.
27. The method of claim 26 , wherein the iron-containing additive has a ratio of ferric to ferrous iron from about 0.1:1 to about 1.95:1.
28. The method of claim 26 , wherein at least 10% of the iron in the iron-containing additive is in a form of wustite.
29. The method of claim 26 , wherein the plurality of cohesively bonded iron-containing particulates have a P 90 size of no more than about 300 microns.
30. The method of claim 26 , wherein the iron-containing additive comprises at least about 50 wt % (dry basis) iron.
31. The method of claim 26 , wherein the mineralizer is present in an amount from about 0.5 to about 15 wt. % (dry basis).