Effects of moisture content on liquefaction of victorian brown coal.

Okuma, Osamu; Masuda, Kaoru; Murakoshi, Koji; Yanai, Shunichi; Matsumura, Toshiro

doi:10.3775/jie.69.259

Cited by 6 publications

(8 citation statements)

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“…Newer instrumental techniques, such as solid-state NMR, have made it possible to systematically study the role of water on coal structure and reactivity, and such studies are beginning to appear. [8][9][10][11] The problem that needs to be solved is that of drying coal without adversely affecting its liquefaction reactivity. This is particularly true for subbituminous coals and lignites for which the U.S. reserves are huge.…”

Section: Introductionmentioning

confidence: 99%

Effect of Different Drying Methods on Coal Structure and Reactivity Toward Liquefaction

et al. 1996

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Different methods of drying coal were investigated to determine if drying can be accomplished without altering the coal structure and reactivity toward liquefaction. Coal-drying methods included thermal and microwave drying at elevated temperatures and chemical drying at low temperature. Six coals from lignite to high volatile bituminous rank were studied. Laboratoryscale liquefaction experiments were carried out on premoisturized and dried coals to determine the effects of different drying methods on liquefaction yields. Solid-state nuclear magnetic resonance (NMR) and swelling measurements were made to assess any changes in coal structure brought about by the different methods of drying. The NMR measurements showed that, in general, there were no major structural changes in coals dried thermally or with microwaves other than partial decarboxylation. Chemically dried coals exhibited increased resolution in the aliphatic carbon region that was attributed to adsorbed methanol, which was a reaction product as well as solvent for the chemical drying method. The swelling ratios of thermally dried and microwave-dried coals were lower than those of premoisturized coals, indicating a greater degree of cross linking in coals dried using these methods. The swelling ratios of the chemically dried coals were greater than those of the premoisturized coals. Coals that were dried or partially dried thermally and with microwaves had lower liquefaction conversions than coals containing equilibrium moisture contents. However, chemically dried coals had conversions ranging from 11 to 60% greater than the premoisturized coals. The conversion behavior is consistent with changes in the physical structure and cross-linking reactions because of drying. Thermal and microwave drying appeared to cause a collapse in the pore structure, thus preventing donor solvents from contacting reactive sites inside the coals. Chemical dehydration did not appear to collapse the pore structure.

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Section: Introductionmentioning

confidence: 99%

Effect of Different Drying Methods on Coal Structure and Reactivity Toward Liquefaction

et al. 1996

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“…Therefore, there is also a need to develop more accurate methods to determine the moisture content of coal in addition to understanding the role of water in coal liquefaction. Only recently have there been any systematic studies of the methods of coal drying on coal structure and the role water plays in enhancing or lessening coal reactivity toward liquefaction (Song et al 1994; Okuma et al 1990). In part, this may be the result of the techniques that have recently become available, such as solid-state NMR.…”

Section: Introductionmentioning

confidence: 99%

An investigation of the role of water on retrograde/condensation reactions and enhanced liquefaction yields. Final report

Miknis¹,

Netzel²,

Wallace³

et al. 1995

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“…[1][2][3][4] The content of sorbed water is therefore one of the key factors in liquefaction that is influenced by the initial physical properties of the coals. [5][6][7][8][9] Pyrolysis can also be affected by sorbed water at sufficiently high heating rates. Gale et al 10 showed that water sorbed in a lignite greatly contributes to the development of mesopores in char during rapid pyrolysis under nitrogen atmosphere.…”

Section: Introductionmentioning

confidence: 99%

“…Low-rank coals contain a number of oxygen functional groups that give the coals their hydrophilic properties and produce gellike structures that shrink and swell in response to water loss and uptake, respectively. − The content of sorbed water is therefore one of the key factors in liquefaction that is influenced by the initial physical properties of the coals. − Pyrolysis can also be affected by sorbed water at sufficiently high heating rates. Gale et al showed that water sorbed in a lignite greatly contributes to the development of mesopores in char during rapid pyrolysis under nitrogen atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Effect of Sorbed Water on Conversion of Coal by Rapid Pyrolysis

et al. 1999

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The effects of water sorbed in coal on its rapid pyrolysis characteristics were examined for three different low-rank coals (Beulah-Zap (BZ), Yallourn (YL), and South Banko (SB)). The pyrolysis was performed in a Curie-point pyrolyzer at temperatures ranging from 631 to 1193 K, employing raw and completely dried samples of the individual coals and also partially dried samples of BZ. The yield of water formed by pyrolysis, Y pw, was defined as the difference between the total mass of evolved water and that of the initially sorbed water, f w, per unit mass of completely dried coal. Y pw for the raw BZ (f w = 47.5%) was 4.4−5.5% at 863−1193 K and appreciably lower than that of the completely dried sample (f w = 0%), 10.8−10.9%. It was also found that a higher f w results in a lower Y pw. Similar effects of sorbed water were confirmed for YL and SB. Analyses of the product distributions revealed that the decrease in Y pw is counterbalanced by increased conversions of oxygen and hydrogen into char as solid residue, CO, H2, and, in particular, liquids. In pyrolysis at 758−1037 K, greater amounts of hydrogen and oxygen were converted into liquids in the raw BZ than in the completely dried sample by 5−8 mol of H and 2−4 mol of O per 100 mol of C. Considering that 11−23 mol of carbon was converted into liquids per 100 mol of C, the differences mean a significant increase in the O and H contents of liquids induced by sorbed water. The enrichment of hydrogen and oxygen was confirmed by the detection of much higher concentrations of hydroxyls and aliphatic hydrogen in liquids from the raw BZ than from the completely dried sample. These effects of sorbed water cannot be simply explained by a decrease in the heating rate of the coal due to the large heat of vaporization of water, since a decrease generally leads to a higher yield of water and fewer oxygen functional groups in liquid products and char, as reported in the literature. Therefore, it was concluded that a portion of the sorbed water remains in the pyrolyzing coal/char matrix under the rapid heating conditions and participates in thermochemical reactions taking place therein.

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Effects of moisture content on liquefaction of victorian brown coal.

Cited by 6 publications

References 0 publications

Effect of Different Drying Methods on Coal Structure and Reactivity Toward Liquefaction

Effect of Different Drying Methods on Coal Structure and Reactivity Toward Liquefaction

An investigation of the role of water on retrograde/condensation reactions and enhanced liquefaction yields. Final report

Effect of Sorbed Water on Conversion of Coal by Rapid Pyrolysis

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