Claims
- 1. A process for reducing the sulfur content and ash content of a feed coal containing sulfur and mineral matter, the process comprising the steps of:
- (a) treating the feed coal in a reaction zone with fused alkali metal caustic at an elevated temperature to remove mineral matter and sulfur from the feed coal yielding (i) a caustic-treated coal and (ii) water-soluble compounds comprising alkali metal, mineral matter, and sulfur;
- (b) combining the caustic-treated coal and water-soluble compounds in a water wash zone with sufficient wash water to reduce the temperature of the caustic-treated coal and dissolve the bulk of the water-soluble compounds before the water-soluble compounds convert to water-insoluble compounds that precipitate on the caustic treated coal, the residence time of the caustic-treated coal in the water wash zone being less than about 90 minutes;
- (c) maintaining the temperature in the water wash zone at less than about 200.degree. F.; and
- (d) separating the caustic-treated coal from spent wash water containing dissolved water-soluble compounds, the separated coal having a sulfur content lower than the sulfur content of the feed coal and an ash content lower than the ash content of the feed coal.
- 2. The process of claim 1 wherein the temperature in the water wash zone is maintained from about 140 to less than about 200.degree. F.
- 3. The process of claim 1 in which the temperature in the water wash zone is maintained at less than about 180.degree. F.
- 4. The process of claim 1 wherein the step of combining comprises combining from about 1 to about 20 parts by weight of wash water per part by weight of caustic-treated coal.
- 5. The process of claim 4 wherein the step of combining comprises combining from about 2 to about 10 parts by weight of wash water per part by weight of caustic-treated coal.
- 6. The process of claim 5 wherein the step of combining comprises combining from about 3 to about 6 parts by weight of wash water per part by weight of caustic-treated coal.
- 7. The process of claim 1 comprising the additional step of treating the separated coal with acid to remove additional mineral matter from the separated coal.
- 8. The process of claim 1 in which the water wash zone comprises at least two separate countercurrent stages in series, wherein the caustic-treated coal and the water-soluble compounds are introduced into the first stage and the wash water is introduced into the last stage, and the coal and wash water pass through the stages countercurrently.
- 9. The process of claim 8 wherein each stage comprises a mixing zone for mixing incoming coal and water and a separation zone for separating the mixture into washed coal and water.
- 10. The process of claim 8 comprising at least 5 stages.
- 11. The process of claim 1 comprising the additional steps of recovering caustic from the spent wash water, and recycling the recovered caustic to the reaction zone.
- 12. The process of claim 11 in which the spent wash water contains carbonates and in which the step of recovering caustic comprises recovering substantially anhydrous alkaline metal caustic by the steps of:
- (i) treating the spent wash water with a calcium-containing material to give an aqueous caustic and a calcium carbonate precipitate;
- (ii) separating the aqueous caustic from the precipitate; and
- (iii) removing substantially all the water from the aqueous caustic to yield substantially anhydrous alkaline metal caustic.
- 13. The process of claim 12 in which the step of combining the caustic-treated coal with wash water comprises washing with water removed from the aqueous caustic.
- 14. The process of claim 1 wherein 70% of the water-soluble compounds are dissolved in the wash water.
- 15. The process of claim 1 in which the mineral matter in the feed coal comprises compounds of aluminum, silicon, and sulfur, and the residence time of the caustic-treated coal in the water wash zone is sufficiently short that at least 70% by weight of the aluminum in the feed coal and at least about 70% by weight of the silicon in the feed coal are present in the spent wash water separated from the caustic-treated coal.
- 16. The process of claim 15 wherein the temperature in the water wash zone is maintained sufficiently low and the residence time of the caustic-treated coal in the water wash zone is sufficiently short that substantially all of the aluminum and silicon in the feed coal are in the spent wash water separated from the caustic-treated coal.
- 17. The process of claim 15 wherein at least about 70% by weight of the sulfur is removed from the feed coal by the process is present in the spent wash water separated from the caustic-treated coal.
- 18. A process for reducing the sulfur content and ash content of a feed coal containing sulfur and mineral matter, the mineral matter comprising compounds of aluminum, silicon, and sulfur, the process comprising the steps of:
- (a) combining the feed coal in a reaction zone with fused alkali metal caustic for extracting mineral matter and sulfur from the feed coal, thereby yielding a caustic-treated coal and extracted mineral matter;
- (b) combining the caustic-treated coal in a water wash zone with wash water for washing extracted mineral matter from the caustic-treated coal, thereby yielding spent wash water containing extracted mineral matter, the residence time of the caustic-treated coal in the water wash zone being less than about 90 minutes;
- (c) maintaining the temperature of the water wash zone at a sufficiently low temperature, less than about 200.degree. F., and separating the caustic-treated coal from the spent wash water in a sufficiently short time that at least about 70% by weight of the aluminum in the feed coal and at least about 70% by weight of the silicon in the feed coal are in the spent wash water, and wherein the separated coal has a sulfur content lower than the sulfur of the feed coal and an ash content lower than the ash content of the feed coal.
- 19. The process of claim 22 wherein at least about 80% by weight of the aluminum in the feed coal and at least about 80% by weight of the silicon in the feed coal are in the removed spent wash water.
- 20. The process of claim 19 wherein at least about 90% by weight of the aluminum in the feed coal and at least about 90% by weight of the silicon in the feed coal are in the removed spent wash water.
- 21. The process of claim 20 wherein substantially all of the aluminum and silicon in the feed coal are in the removed spent wash water.
- 22. The process of claim 18 in which the temperature in the water wash zone is maintained at less than about 180.degree. F.
- 23. The process of claim 18 in which the water wash zone comprises at least two separate countercurrent stages in series, wherein the caustic-treated coal and the extracted mineral matter are introduced into the first stage and the wash water is introduced into the last stage, and the coal and wash water pass through the stages countercurrently.
- 24. The process of claim 23 wherein each stage comprises a mixing zone for mixing incoming coal and water and a separation zone for separating the mixture into washed coal and water.
- 25. The process of claim 18 wherein the residence time of the caustic-treated coal in the water wash zone is less than about 1 hour.
- 26. The process of claim 18 wherein the amount of wash water combined in the water wash zone is from about 1 to about 20 parts by weight per part by weight of feed coal.
- 27. The process of claim 26 wherein the amount of wash water combined in the water wash zone is from about 2 to about 10 parts by weight per part by weight of feed coal.
- 28. The process of claim 27 wherein the amount of wash water combined in the water wash zone is from about 3 to about 6 parts by weight per part by weight of feed coal.
- 29. The process of claim 18 wherein at least about 70% by weight of the sulfur removed from the feed coal by the process is present in the spent wash water.
- 30. The process of claim 29 wherein at least about 80% by weight of the sulfur removed from the feed coal by the process is present in the spent wash water.
- 31. The process of claim 30 wherein at least about 90% by weight of the sulfur removed from the feed coal by the process is present in the spent wash water.
- 32. A process for reducing the sulfur content and ash content of a feed coal containing sulfur and mineral matter, the mineral matter comprising compounds of aluminum, silicon, and sulfur, the process comprising the steps of:
- (a) combining the feed coal in a reaction zone with fused alkali metal caustic for extracting mineral matter and sulfur from the feed coal, thereby yielding a caustic-treated coal and extracted mineral matter;
- (b) combining the caustic-treated coal and extracted mineral matter in wa water wash zone with wash water for washing extracted mineral matter from the caustic-treated coal, the amount of wash water being from about 1 to about 20 parts by weight per part by weight of feed coal, thereby yielding spent wash water containing extracted mineral matter including compounds comprising alkali metal, the residence time of the caustic-treated coal in the water wash zone being less than about 90 minutes;
- (c) maintaining the temperature of the water wash zone at a sufficiently low temperature, less than about 200.degree. F., and separating the caustic-treated coal from the spent wash water in a sufficiently short time of less than about 90 minutes so that substantially all the aluminum in the feed coal and substantially all the silicon in the feed coal are in the spent wash water, and at least about 70% by weight of the sulfur removed from the feed coal by the process is present in the spent wash water;
- (d) treating the separated coal with an acid for removing iron compounds from the separated coal, thereby producing an acid-washed coal having a sulfur content lower than the sulfur content of the feed coal and an ash content lower than the ash content of the feed coal;
- (e) recovering substantially anhydrous alkali metal caustic from the spent wash water by:
- (i) treating the spent wash water with a calcium containing material that is insoluble in the spent wash water to give an aqueous caustic and a calcium carbonate precipitate;
- (ii) separating the aqueous caustic from the precipitate; and
- (iii) removing substantially all of the water from the aqueous caustic to yield substantially anhydrous alkali metal caustic; and
- (f) recycling the recovered caustic to the reaction zone.
- 33. The process of claim 1 wherein the residence time of the caustic-treated coal in the water wash zone is less than about 1 hour.
- 34. The process of claim 33 wherein the residence time of the caustic-treated coal in the water wash zone is about 1/2 hour.
- 35. The process of claim 33 wherein the residence time of the caustic-treated coal in the water wash zone is less than about 1/2 hour.
- 36. The process of claim 25 wherein the residence time of the caustic-treated coal in the water wash zone is about 1/2 hour.
- 37. The process of claim 25 wherein the residence time of the caustic-treated coal in the water wash zone is less than about 1/2 hour.
RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Patent application Ser. No. 419,659 filed Oct. 11, 1989, which is a file wrapper continuation of Application Ser. No. 770,324 filed on Aug. 27, 1985; which is a continuation-in-part of U.S. Patent application Ser. No. 486,276 filed on Mar. 10, 1983 by Robert Meyers and Walter D. Hart, Now U.S. Pat. No. 4,545,891; which is based on an International Application filed under the Patent Cooperation Treaty, application No. PCT/US82/00394 filed on Mar. 30, 1982, published on Oct. 14, 1982, Publication No. WO82/03404; which is based, as a continuation-in-part, on U.S. application Ser. No. 349,514 filed on Mar. 31, 1981. These applications are incorporated herein by this reference.
US Referenced Citations (69)
Foreign Referenced Citations (1)
Number |
Date |
Country |
WO8203404 |
Oct 1982 |
WOX |
Non-Patent Literature Citations (5)
Entry |
Coal Desulfurization, R. A. Meyers, 1977, "Pyritic Sulfur Removal Process Caustic Leaching," pp. 201-209, 230-233. |
Coal Desulfurization, R. A. Meyers, 1977, pp. 25-54, 230-234. |
"Conversion of Coal To Simple Compounds", Parker et al. |
Industrial & Engr. Chem., vol. 47, No. 6, Aug., 1955, pp. 1586-1592. |
"The Effect of Molten Caustic on Pyritic Sulfur in Bituminous Coal", Masciantonio, pp. 269-275. |
Continuations (1)
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Number |
Date |
Country |
Parent |
770324 |
Aug 1985 |
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Continuation in Parts (2)
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Number |
Date |
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Parent |
419659 |
Oct 1989 |
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Parent |
486276 |
Mar 1983 |
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