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Pyrolysis

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Articles 91 - 98 of 98

Full-Text Articles in Chemical Engineering

Decreases In The Swelling And Porosity Of Bituminous Coals During Devolatilization At High Heating Rates, Thomas K. Gale, Thomas H. Fletcher, Calvin H. Bartholomew Jan 1995

Decreases In The Swelling And Porosity Of Bituminous Coals During Devolatilization At High Heating Rates, Thomas K. Gale, Thomas H. Fletcher, Calvin H. Bartholomew

Faculty Publications

Concern about comparability and validity of different methods for producing coal chars for reactivity experiments has led to research on the effect of devolatilization conditions on the char physical and chemical structure. Particle diameter and porosity changes during devolatilization significantly affect char oxidation rates. In particular, physical properties of chars prepared in drop tube reactors differ greatly from chars prepared in flat flame burner experiments. Recent data indicate that the presence of oxygen in the gas atmosphere has no effect on swelling until char oxidation has begun. The present research concentrates on the effects of heating rate, particle temperature and …

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Thermophoretic Sampling Of Coal-Derived Soot Particles During Devolatilization, Jinliang Ma, Thomas H. Fletcher, Brent W. Webb Jan 1995

Thermophoretic Sampling Of Coal-Derived Soot Particles During Devolatilization, Jinliang Ma, Thomas H. Fletcher, Brent W. Webb

Faculty Publications

Thermophoretic sampling of soot particles formed during high-temperature coal devolatilization is performed in order to examine soot particle sizes and shapes. Coal particles are injected along the centerline of a laminar flow flat flame burner, where a fuel-rich methane-air flame is used as a heat source. Volatiles released from the coal particles form a cloud of soot particles at high temperatures in the absence of oxygen. A carbon-coated microscope grid is briefly inserted into the soot cloud, where the temperature gradient between the soot particles and the cold grid surface causes the migration of soot particles and results in deposition. …

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Effects Of Pyrolysis Conditions On Internal Surface Areas And Densities Of Coal Chars Prepared At High Heating Rates In Reactive And Non-Reactive Atmospheres, Thomas K. Gale, Thomas H. Fletcher, Calvin H. Bartholomew Jan 1995

Effects Of Pyrolysis Conditions On Internal Surface Areas And Densities Of Coal Chars Prepared At High Heating Rates In Reactive And Non-Reactive Atmospheres, Thomas K. Gale, Thomas H. Fletcher, Calvin H. Bartholomew

Faculty Publications

Concern about comparability and validity of different methods for producing coal chars for reactivity experiments has led to research on the effect of devolatilization conditions on the char physical and chemical structure. Particle diameter and porosity changes during devolatilization significantly affect char oxidation rates. In particular, physical properties of chars prepared in drop tube reactors differ greatly from chars prepared in fiat flame burner experiments. Recent data indicate that the presence of oxygen in the gas atmosphere has no effect on swelling until char oxidation has begun. The present research concentrates on the effects of heating rate, particle temperature and …

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The Impact Of Coal Pyrolysis On Combustion, Peter R. Solomon, Thomas H. Fletcher Jan 1994

The Impact Of Coal Pyrolysis On Combustion, Peter R. Solomon, Thomas H. Fletcher

Faculty Publications

The pyrolysis process has impacts throughout coal combustion. The roles of pyrolysis in various aspectsof the coal combustion process are described, including the devolatilization yield, nitrogen release, softening and swelling, soot formation, and char reactivity. These processes can be understood and quantitatively predicted using recently developed network pyrolysis models that describe the transformation of the coal's chemical structure. The models are described and examples of their predictive ability for important coal combustion phenomena are presented.

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Swelling Properties Of Coal Chars During Rapid Coal Pyrolysis And Combustion,, Thomas H. Fletcher Jan 1993

Swelling Properties Of Coal Chars During Rapid Coal Pyrolysis And Combustion,, Thomas H. Fletcher

Faculty Publications

Coal devolatilization experiments are commonly conducted at moderate temperatures (800 to 1300 K) and heating rates (103 to 104 Ks−1) in inert environments in order to measure evolved species before secondary reaction in the gas phase. However, chars from these experiments exhibit different physical characteristics than chars obtained under typical combustion conditions (1500 to 2000 K, 105 Ks−1, and 3 to 10 mol% oxygen). Experiments were conducted in two laminar, entrained-flow reactors to determine characteristics of coal chars in inert and oxygen-rich environments. One flow reactor was heated electrically, with gas temperatures of …

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Progress In Coal Pyrolysis, Peter R. Solomon, Thomas H. Fletcher, Ronald J. Pugmire Jan 1993

Progress In Coal Pyrolysis, Peter R. Solomon, Thomas H. Fletcher, Ronald J. Pugmire

Faculty Publications

The heterogeneous nature of coal and the complexity of the pyrolysis process have made it very difficult to perform unambiguous experiments to determine the rates and mechanisms in coal pyrolysis. However, recent years have seen a number of new experimental and theoretical approaches which shed new light on the subject. This paper considers the recent progress on kinetics, the formation of volatile products, network models, cross-linking, rank effects, and the ‘two-component’ model of coal structure. Recent experiments which measured coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. These rates also agree with those derived …

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Chemical Structure Of Char In The Transition From Devolatilization To Combustion, Thomas H. Fletcher, Mark S. Solum, David M. Grant, Ronald J. Pugmire Jan 1992

Chemical Structure Of Char In The Transition From Devolatilization To Combustion, Thomas H. Fletcher, Mark S. Solum, David M. Grant, Ronald J. Pugmire

Faculty Publications

Coal devolatilization experiments are generally conducted separately from char oxidation experiments, and the relationship between the chars generated in the two types of research is often ignored. However, char is one of the most important products of coal devolatilization and must be characterized as a function of temperature and heating rate in a manner similar to that for gaseous devolatilization products. The chemical structure of the parent coal directly affects devolatilization behavior. In this work, the chemical structure of chars from five coals of different rank are examined, and implications on char reactivity are discussed. Chars were obtained as a …

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Formation Of Light Hydrocarbons And Soot In The Pyrolysis Reactions Of Chloro, Dichlorobenzene, Acetylene And Benzene In An Atmosphere Of Hydrogen, Larry Jiyuan Zhu Sep 1988

Formation Of Light Hydrocarbons And Soot In The Pyrolysis Reactions Of Chloro, Dichlorobenzene, Acetylene And Benzene In An Atmosphere Of Hydrogen, Larry Jiyuan Zhu

Theses

The kinetics of thermal decomposition of chlorobenzene and dichlorobenzene in a hydrogen and helium atmosphere were further studied to investigate formation of soot and light hydrocarbons. The experiments were performed at atmosphere pressure with residence times rangeing from 0.2 to 1.2 seconds, and the temperature ranges of 850°C to 925°C for chlorobenzene and 870°C to 910°C for dichlorobenzene. Flame ionization detectors, which were connected to GC columns, were utilized for the qualitative and quantitative analysis of the reaction products. A methyl silicone capillary column was used analyzing of heavy aromatics and a Carbosive G was used to analyze light hydrocarbons. …

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