Coal Plasticity Mechanism: Inferences from Liquefaction Studies

Neavel, Richard C.

doi:10.1016/b978-0-12-150701-5.50006-1

Cited by 41 publications

(20 citation statements)

References 24 publications

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“…Until then, these coals from the Wasatch Plateau field (Uinta Inspection of the pyrolysis mass spectra in Figure 6 shows the structural effects of weathering to be dominated by a decreased yield of phenolic and naphthaleneic moieties and a relative increase in the yield of aliphatic carboxylic and carbonylic moieties, as further illustrated by the scatter plots of selected peak intensities in Figure 7. These findings are in excellent agreement with current vicw5 on chemical effects of coal weathering according to which the process is characterized by the formation of ether bridges between aromatic nuclei, with concurrent reduction in free phenolic hydroxyl groups [3], and by the oxidation of aliphatic moieties to carbonylic and carboxylic functional groups [4].…”

Section: Weathering Experimentssupporting

confidence: 88%

Role of preasphaltenes in coal conversion reactions. First quarterly report, year two

Hill¹,

Meuzelaar²,

Harper³

1984

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Price: Printed Copy A02 Microfiche AOI Codes are used for pricing all publications. The code is determined by the number of pages in the publication. Information pertaining to the P. ricing codes can be found in the current issues of the following publications, which are generally available in most libraries: Energy Research Abstracts (ERA); Government Reports Announcements and Index (GRA and I); Scientific and Technical

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Section: Weathering Experimentssupporting

confidence: 88%

Role of preasphaltenes in coal conversion reactions. First quarterly report, year two

Hill¹,

Meuzelaar²,

Harper³

1984

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“…It is difficult to mathematically formulate the coupled effects of transport and chemistry under softening conditions. Furthermore, there is a severe lack of experimental data on the physicochemical phenomena contributing to the structural modifications, including the rheological behavior of softened coal, volatiles secondary reactions, and the effects of reaction conditions on the intraparticle inventory of coal plasticizing agent, metaplast (Van Krevelen, 1961;Neavel, 1982). Considerable progress has been made in modeling intraparticle volatiles transport in the pyrolysis of nonsoftening coals (Russel et al, 1979;Chen and Wen, 1979;Gavalas and Wilkes, 1980).…”

Section: Introductionmentioning

confidence: 99%

An experimental and modeling study of softening coal pyrolysis

1989

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A quantitative model of softening coal pryolysis is developed and tested against observed behavior. The model treats intraparticle transport of gases and metaplast throughout the softening stage of pyrolysis via growth of bubbles uniformly dispersed in the molten coal. The model quantitatively describes the transient softening behavior including the initiation, duration, and magnitude of plasticity and swelling of the particle. The model kinetic parameters are derived from experiments, in which a highly softening Pittsburgh No. 8 bituminous coal was pyrolyzed, and total weight loss, and yields and molecular weight distributions of tars and pyridine extractables of cooled chars were measured. Model predictions of effects of pressure, particle diameter and temperature on tar yields and weight losses, of effects of pressure on swelling ratio, and of effects of heating rate on plasticity are presented. The model provides good fits to the laboratory data and predicts trends in pyrolysis behavior in good qualitative accord with expectations based on published data.

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“…8, with a1 being an empirical proportionality constant. The concept of the enriching effect of H2 on metaplast formation is borrowed from a mechanistic view of coal liquefaction (Neavel, 1982) where the presence of hydrogen is considered crucial for stabilization of coal depolymerization products.…”

Section: Chemical Reactlon Schemementioning

confidence: 99%

Rapid hydropyrolysis of softening coal particles—A modeling study. Part I: Model formulation and parameter values

1985

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A mathematical model is developed for rapid hydropyrolysis of softening coal particles. It is aimed to represent previously measured effects of pressure and particle size on product yields. The model includes a global chemical reaction scheme combined with diffusional transport of hydrogen dependent on the transient physical properties of the coal. Model predictions are compared with experimental data in a companion paper. The objective of this study was to define and formulate a mathematical model for rapid hydropyrolysis of softening coal particles consistent with the drastic changes in physical properties associated with softening and resolidification. Rapid hydropyrolysis, where coal particles are heated at rates of 100 to 10,000 K/s under high Hz pressure, is of interest not only as a process for converting coal into CHcrich gas and liquids but also in coal gasification with steam where significant partial pressures of Hz occur. Previous experimental studies (Anthony et al., 1976;Suuberg et al., 1980) indicate that the coal's transient fluidity plays an important role with respect to transport mechanisms involved. For example, a particle size effect on integral product yields had been found with Pittsburgh Seam bituminous coal, a strongly caking-i.e., softening-coal, but not with a lignite which retains a porous structure throughout the experiment. Previous modeling work has either concentrated on hydropyrolysis of coals which retain their porosity (Russel et al., 1979), or-in the case of softening coals-on pyrolysis, i.e., thermal decomposition in the absence of Hz. The resulting models therefore could not adequate represent the experimental results with softening coals. GEORG SCHAUBThis modeling study takes advantage of kinetic information from previous investigations of coal hydrogasification and pyrolysis. The study addresses the questions of intra-and extraparticle transport limitations for hydrogen and develops a tentative description of the coal's transient fluidity and its implication for hydrogen transport. The model leads to predictions of particle size and pressure effects which are compared with trends previously measured in a screen heater apparatus. CONCLUSIONS AND SIGNIFICANCEA mechanistic concept has been formulated for the chemical reactions and mass transport processes involved in rapid hydropyrolysis of softening coal particles. A global chemical reaction scheme borrowed from previous coal pyrolysis and hydrogasification studies is combined with a concept of intraparticle hydrogen transport, seen as diffusion of either hydrogen dissolved in the coal melt during the plastic period or of gas phase hydrogen in a reconstituted pore matrix after resolidification. The transient coal fluidity is expressed in terms of appearance and disappearance of a plasticizing material called metaplast, which is generated during the coal's pyrolysis reactions. Transport of metaplast away from the coal particle to Ceorg Schauh is currently with Lurgi GmhH, 6ooo Frankfurt 11, West Germany yield tar is modeled as...

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Coal Plasticity Mechanism: Inferences from Liquefaction Studies

Cited by 41 publications

References 24 publications

Role of preasphaltenes in coal conversion reactions. First quarterly report, year two

Role of preasphaltenes in coal conversion reactions. First quarterly report, year two

An experimental and modeling study of softening coal pyrolysis

Rapid hydropyrolysis of softening coal particles—A modeling study. Part I: Model formulation and parameter values

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