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David M Grant - One of the best experts on this subject based on the ideXlab platform.
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Chemical structure of char in the transition from devolatilization to combustion
Energy & Fuels, 1992Co-Authors: Thomas H. Fletcher, Mark S. Solum, David M Grant, Ronald J. PugmireAbstract:Coal devolatilization experiments are generally conducted separately from char oxidation experiments, and the relationship between the chars general 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
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chemical percolation model for devolatilization 3 direct use of carbon 13 nmr data to predict effects of Coal type
Energy & Fuels, 1992Co-Authors: Thomas H. Fletcher, Ronald J. Pugmire, Mark S. Solum, Alan R. Kerstein, David M GrantAbstract:~~ ~~ ~ ~ ~~ The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated Coal based on the chemical structure of the Parent Coal. Percolation lattice statistics are employed to describe the generation of tar precursors of finite size based on the number of cleaved labile bonds in the infinite Coal lattice. The chemical percolation devolatization model described here includes treatment of vapopliquid equilibrium and a cross-linking mechanism. The cross-linking mechanism permits reattachment of metaplast to the infinite char matrix. A generalized vapor preasure correlation for high molecular weight hydrocarbons, such as Coal tar, is proposed based on data from Coal liquids. Coal-independent kinetic parameters are employed. Coal-dependent chemical structure coefficients for the CPD model are taken directly from 13C NMR measurements, with the exception of one empirical parameter representing the population of char bridges in the Parent Coal. This is in contrast to the previous and common practice of adjusting input coefficients to precisely match measured tar and total volatiles yields. The CPD model successfully predicts the effects of pressure on tar and total volatiles yields observed in heated grid experiments for both bituminous Coal and for lignite. Predictions of the amount and characteristics of gas and tar from many different Coals compare well with available data, which is unique because the majority of model input coefficients are taken directly from NMR data and are not used as empirical fitting coefficients. Predicted tar molecular weights are consistent with size-exclusion chromatography (SEC) data and field ionization mass spectrometry (FIMS) data. Predictions of average molecular weights of aromatic clusters as a function of Coal type agree with corresponding data from NMR analyses of Parent Coals. The direct use of chemical structure data as a function of Coal type helps justify the model on a mechanistic rather than an empirical basis.
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Chemical percolation model for devolatilization. 3. Direct use of carbon-13 NMR data to predict effects of Coal type
Energy & Fuels, 1992Co-Authors: Thomas H. Fletcher, Ronald J. Pugmire, Mark S. Solum, Alan R. Kerstein, David M GrantAbstract:~~ ~~ ~ ~ ~~ The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated Coal based on the chemical structure of the Parent Coal. Percolation lattice statistics are employed to describe the generation of tar precursors of finite size based on the number of cleaved labile bonds in the infinite Coal lattice. The chemical percolation devolatization model described here includes treatment of vapopliquid equilibrium and a cross-linking mechanism. The cross-linking mechanism permits reattachment of metaplast to the infinite char matrix. A generalized vapor preasure correlation for high molecular weight hydrocarbons, such as Coal tar, is proposed based on data from Coal liquids. Coal-independent kinetic parameters are employed. Coal-dependent chemical structure coefficients for the CPD model are taken directly from 13C NMR measurements, with the exception of one empirical parameter representing the population of char bridges in the Parent Coal. This is in contrast to the previous and common practice of adjusting input coefficients to precisely match measured tar and total volatiles yields. The CPD model successfully predicts the effects of pressure on tar and total volatiles yields observed in heated grid experiments for both bituminous Coal and for lignite. Predictions of the amount and characteristics of gas and tar from many different Coals compare well with available data, which is unique because the majority of model input coefficients are taken directly from NMR data and are not used as empirical fitting coefficients. Predicted tar molecular weights are consistent with size-exclusion chromatography (SEC) data and field ionization mass spectrometry (FIMS) data. Predictions of average molecular weights of aromatic clusters as a function of Coal type agree with corresponding data from NMR analyses of Parent Coals. The direct use of chemical structure data as a function of Coal type helps justify the model on a mechanistic rather than an empirical basis.
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chemical percolation model for devolatilization 2 temperature and heating rate effects on product yields
Energy & Fuels, 1990Co-Authors: Thomas H. Fletcher, Ronald J. Pugmire, Alan R. Kerstein, David M GrantAbstract:The chemical percolation devolatilization (CPD) model previously developed to describe the devolatilization behavior of rapidly heated Coal was based on the chemical structure of the Parent Coal. Percolation lattice statistics are employed to describe generation of finite tar clusters as labile bonds are cleaved in the infinite Coal lattice. The model is used here to describe effects of heating rate and temperature on tar and gas release from Coal. Results indicate that the CPD models predictions yied good agreement with published data for a wide range of Coals and particle heating rates
Kouichi Miura - One of the best experts on this subject based on the ideXlab platform.
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low rank Coal upgrading in a flow of hot water
Energy & Fuels, 2009Co-Authors: Masato Morimoto, Hiroyuki Nakagawa, Kouichi MiuraAbstract:Simultaneous hydrothermal degradation and extraction at around 350{sup o}C using flowing solvent as a reaction/extraction medium were proposed for upgrading brown Coal, more specifically, for converting brown Coal into several fractions having different molecular weight and chemical structure under mild conditions. When an Australian brown Coal, Loy Yang Coal, was treated by water at 350{sup o}C under 18 MPa, the Coal was separated into four fractions: gaseous product by 8% yield, water-soluble extract at room temperature (soluble) by 23% yield, extract precipitates as solid at room temperature (deposit) by 23% yield, and residual Coal (upgraded Coal) by 46% yield on daf basis. The separation was found to be realized by in situ extraction of low-molecular-weight substances released from Coal macromolecular structure and/or those generated by hydrothermal decomposition reactions at 350{sup o}C. The solid products obtained, deposit and upgraded Coal, were characterized in detail to examine the possibility of their effective utilization as solid fuel and chemical feed stock. The upgraded Coal showed higher heating value and higher gasification reactivity than the Parent Coal, indicating that the upgraded Coal can be a better solid fuel than the Parent Coal. The solid extract, deposit, was found to show thermoplasticity at less thanmore » 200{sup o}C, suggesting the possibility of utilizing the deposit as a raw material of high performance carbon materials. Several variables affecting the performance of the proposed method are also examined in detail in this paper. 12 refs., 8 figs., 3 tabs.« less
Shaohua Wu - One of the best experts on this subject based on the ideXlab platform.
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fast pyrolysis comparison of Coal water slurry with its Parent Coal in curie point pyrolyser
Energy Conversion and Management, 2009Co-Authors: Hui Wang, Xiumin Jiang, Shaohua WuAbstract:Abstract Curie-point pyrolyser is an instrument that can be used to analyze powder or slurry samples at medium heating rates. It can keep a constant heating rate to heat up the samples until the wire temperature reaches Curie-point temperature and remains the same temperature. In this paper, Coal–water slurry (CWS) and its Parent Coal were studied by using a Curie-point pyrolyser. Kinetic parameters of pyrolysis were calculated and apParent activation energy of CWS obtained is 16.362 kJ/mol, which is a little higher than that of its Parent Coal, 12.691 kJ/mol. The experimental curves show lean S shape and the heating rate are obtained, which are 617 K/s and 834 K/s, respectively.
Thomas H. Fletcher - One of the best experts on this subject based on the ideXlab platform.
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Chemical structure of char in the transition from devolatilization to combustion
Energy & Fuels, 1992Co-Authors: Thomas H. Fletcher, Mark S. Solum, David M Grant, Ronald J. PugmireAbstract:Coal devolatilization experiments are generally conducted separately from char oxidation experiments, and the relationship between the chars general 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
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chemical percolation model for devolatilization 3 direct use of carbon 13 nmr data to predict effects of Coal type
Energy & Fuels, 1992Co-Authors: Thomas H. Fletcher, Ronald J. Pugmire, Mark S. Solum, Alan R. Kerstein, David M GrantAbstract:~~ ~~ ~ ~ ~~ The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated Coal based on the chemical structure of the Parent Coal. Percolation lattice statistics are employed to describe the generation of tar precursors of finite size based on the number of cleaved labile bonds in the infinite Coal lattice. The chemical percolation devolatization model described here includes treatment of vapopliquid equilibrium and a cross-linking mechanism. The cross-linking mechanism permits reattachment of metaplast to the infinite char matrix. A generalized vapor preasure correlation for high molecular weight hydrocarbons, such as Coal tar, is proposed based on data from Coal liquids. Coal-independent kinetic parameters are employed. Coal-dependent chemical structure coefficients for the CPD model are taken directly from 13C NMR measurements, with the exception of one empirical parameter representing the population of char bridges in the Parent Coal. This is in contrast to the previous and common practice of adjusting input coefficients to precisely match measured tar and total volatiles yields. The CPD model successfully predicts the effects of pressure on tar and total volatiles yields observed in heated grid experiments for both bituminous Coal and for lignite. Predictions of the amount and characteristics of gas and tar from many different Coals compare well with available data, which is unique because the majority of model input coefficients are taken directly from NMR data and are not used as empirical fitting coefficients. Predicted tar molecular weights are consistent with size-exclusion chromatography (SEC) data and field ionization mass spectrometry (FIMS) data. Predictions of average molecular weights of aromatic clusters as a function of Coal type agree with corresponding data from NMR analyses of Parent Coals. The direct use of chemical structure data as a function of Coal type helps justify the model on a mechanistic rather than an empirical basis.
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Chemical percolation model for devolatilization. 3. Direct use of carbon-13 NMR data to predict effects of Coal type
Energy & Fuels, 1992Co-Authors: Thomas H. Fletcher, Ronald J. Pugmire, Mark S. Solum, Alan R. Kerstein, David M GrantAbstract:~~ ~~ ~ ~ ~~ The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated Coal based on the chemical structure of the Parent Coal. Percolation lattice statistics are employed to describe the generation of tar precursors of finite size based on the number of cleaved labile bonds in the infinite Coal lattice. The chemical percolation devolatization model described here includes treatment of vapopliquid equilibrium and a cross-linking mechanism. The cross-linking mechanism permits reattachment of metaplast to the infinite char matrix. A generalized vapor preasure correlation for high molecular weight hydrocarbons, such as Coal tar, is proposed based on data from Coal liquids. Coal-independent kinetic parameters are employed. Coal-dependent chemical structure coefficients for the CPD model are taken directly from 13C NMR measurements, with the exception of one empirical parameter representing the population of char bridges in the Parent Coal. This is in contrast to the previous and common practice of adjusting input coefficients to precisely match measured tar and total volatiles yields. The CPD model successfully predicts the effects of pressure on tar and total volatiles yields observed in heated grid experiments for both bituminous Coal and for lignite. Predictions of the amount and characteristics of gas and tar from many different Coals compare well with available data, which is unique because the majority of model input coefficients are taken directly from NMR data and are not used as empirical fitting coefficients. Predicted tar molecular weights are consistent with size-exclusion chromatography (SEC) data and field ionization mass spectrometry (FIMS) data. Predictions of average molecular weights of aromatic clusters as a function of Coal type agree with corresponding data from NMR analyses of Parent Coals. The direct use of chemical structure data as a function of Coal type helps justify the model on a mechanistic rather than an empirical basis.
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chemical percolation model for devolatilization 2 temperature and heating rate effects on product yields
Energy & Fuels, 1990Co-Authors: Thomas H. Fletcher, Ronald J. Pugmire, Alan R. Kerstein, David M GrantAbstract:The chemical percolation devolatilization (CPD) model previously developed to describe the devolatilization behavior of rapidly heated Coal was based on the chemical structure of the Parent Coal. Percolation lattice statistics are employed to describe generation of finite tar clusters as labile bonds are cleaved in the infinite Coal lattice. The model is used here to describe effects of heating rate and temperature on tar and gas release from Coal. Results indicate that the CPD models predictions yied good agreement with published data for a wide range of Coals and particle heating rates
Raymond C Everson - One of the best experts on this subject based on the ideXlab platform.
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improved reactivity of large Coal particles by k2co3 addition during steam gasification
Fuel Processing Technology, 2013Co-Authors: Sansha Coetzee, Hein W J P Neomagus, John R Bunt, Raymond C EversonAbstract:Abstract In this study, the excess solution impregnation method was used to impregnate large Coal particles (5 and 10 mm) with K2CO3, and the effect of the additive on steam gasification reactivity was investigated. A washed bituminous, medium rank-C Highveld Coal, with an ash content of 12.6 wt.% (air-dried basis), was used for experimentation. The excess solution method was used to impregnate Coal particles with the selected additive, K2CO3, and results from XRF analysis indicated that the potassium loading increased from 0.05 wt.% (raw Coal) up to 0.83 wt.% (impregnated Coal), on a Coal basis. The potassium-impregnated large Coal particles were used for low temperature (800–875 °C) steam gasification experiments. Results obtained for the reactivity of the Parent Coal were compared to that of the impregnated Coal, which indicated that the addition of K2CO3 increased the reaction rate of large Coal particles by up to 40%. It was also found that the addition of K2CO3 decreased the activation energy, from 191 kJ/mol (raw Coal) to 179 kJ/mol (impregnated Coal).
