Elution of Ti during solvent extraction of coal and the transformation of eluted Ti upon combustion
Solvent extraction of coal is an effective method for removing coal ash, thereby generating the ultraclean fuel that can be directly combusted in gas turbine. Due to their organic affinity, a few inorganic elements can be extracted as well. Ti in coal extract, its elution from raw coal as well as th...
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Published in | AIChE journal Vol. 54; no. 6; pp. 1646 - 1655 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Hoboken
Wiley Subscription Services, Inc., A Wiley Company
01.06.2008
Wiley Subscription Services American Institute of Chemical Engineers |
Subjects | |
Online Access | Get full text |
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Summary: | Solvent extraction of coal is an effective method for removing coal ash, thereby generating the ultraclean fuel that can be directly combusted in gas turbine. Due to their organic affinity, a few inorganic elements can be extracted as well. Ti in coal extract, its elution from raw coal as well as the transformation of eluted Ti during coal extract combustion, have been investigated. Two coals of the U.S. and their acid-washed samples were extracted under 1 MPa N₂ (cold) at 360°C. The solvents used include nonpolar 1-methynaphthalene and its mixtures with polar indole. The results indicate that, Ti in coal extracts is mainly composed of nanoparticles including TiO₂ (anatase) and Ti associated with quartz. These particles are insoluble in any acids, having a fine dispersion into coal matrix. Upon coal fragmentation at 360°C, they could be librated, and, hence, traversed the filter for isolating coal extracts. The organo-Ti was preferentially extracted as well, which is most likely in a form of Ti porphyrin or Ti chelated with phenol-oxygen. These findings also have implications for revealing the modes of occurrence of Ti in the raw coals. Combustion of coal extract at 1,000°C resulted in the formation of nanometric TiO₂ polymorphs and much complex compound like FeZnTiO₄. The former species could be mainly formed by the phase change of TiO₂ (anatase) at high-temperatures, while formation of the latter one could involve the capture of metallic vapors like Zn on TiO₂ polymorphs. The resultant nanoparticles may escape the conventional pollution control devices, causing environmental concern. © 2008 American Institute of Chemical Engineers AIChE J, 2008 |
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Bibliography: | http://dx.doi.org/10.1002/aic.11474 istex:F019B986D37B2351554416D580F384127F254694 ArticleID:AIC11474 NEDO of Japan ark:/67375/WNG-38FDGG95-F ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0001-1541 1547-5905 |
DOI: | 10.1002/aic.11474 |