Soloman, PR
1994
The Impace of Pyrolysis in Combustion
Solomon, P.R. and Fletcher, T.H.
25th Symposium International on Combustion, 1994 (in press). (Also presented at the 25th Symposium (International) on Combustion, Irvine, CA, Jul-Aug, 1994.) Funded by ACERC.
The pyrolysis process has impacts throughout coal combustion. The roles of pyrolysis in various aspects of 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.
Fossil-Fuel Conversion - Measurement and Modeling
Solomon, P.R.; Serio, M.A.; Hamblen, D.G.; Smoot, L.D.; Brewster, B.S. and Radulovic, P.T.
Proceedings of the Coal-Fired Power Systems 94 - Advances in IGCC and PFBC Review Meeting, Morgantown, West Virginia, June 1994. Funded by US Department of Energy/Morgantown Energy Technology Center.
The main objective of this program is to understand the chemical and physical mechanisms in coal conversion processes and incorporate this technology for the purposes of development, evaluation in advanced coal conversion devices. To accomplish this objective, this program will: 1) provide critical data on the physical and chemical processes in fossil fuel gasifiers and combustors; 2) further develop a set of comprehensive codes; and 3) apply these codes to model various types of combustors and gasifiers (fixed-bed transport reactor, and fluidized-bed for coal and gas turbines for natural gas).
To expand the utilization of coal, it is necessary to reduce the technical and economic risks inherent in operating a feedstock which is highly variable and which sometimes exhibits unexpected and unwanted behavior. Reducing the risks can be achieved by establishing the technology to predict a coal's behavior in a process. This program is creating this predictive capability by merging technology developed at Advanced Fuel Research, Inc. (AFR) in predicting coal devolatilization behavior with technology developed at Brigham Young University (BYU) in comprehensive computer codes for modeling of entrained-bed and fixed-bed reactors and technology developed at the U.S. DOE-METC in comprehensive computer codes for fluidized-bed reactors. These advanced technologies will be further developed to provide: 1) a fixed-bed model capable of predicting combustion and gasification of large coal particles, 2) a transport reactor model, 3) a model for lean premixed combustion of natural gas, and 4) an improved fluidized-bed code with an advanced coal devolatilization chemistry submodel.
1993
Progress in Coal Pyrolysis
Solomon, P.R.; Fletcher, T.H. and Pugmire, R.J.
Fuel, 72:587-597, 1993. Funded, in part, by ACERC.
The heterogeneous nature of coal and the complexity of the pyrolysis process has 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 that shed new light on the subject. This paper considers the recent progress on kinetics, the formation of volatile products, network models, crosslinking, rank effects, and the 'two-component model of coal structure.' Recent experiments that measured coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. These rates also agree with those derived from experiments at low heating rates. In tar formation and transport, a consensus is being reached on the central role of the volatility of tar molecules in explaining the variation with operating conditions (pressure, heating rate, particle size, etc.) of the amounts and molecular weight distribution of tars. Progress in the quantitative prediction of tar and char yields is being made through recently developed models for the fragmentation of the macromolecular coal network. These models, which provide quantitative descriptions of the relations between the chemical structure of the coal and the physical and chemical properties of the pyrolysis products (gas, tar, soot, and char), are an exciting advance in the understanding of the pyrolysis process. Such models are linking the occurrence of the plastic phrase with the 'liquid' fragments formed during pyrolysis. On the subject of retrogressive cross-linking reactions, both solvent swelling and NMR measurements confirm important rank-dependent differences in reaction rates: these appear to be related to the oxygen functionalities. Reasonable agreement is also seen for variations with coal rank of kinetics rates derived from measurements at low heating rates. Experiments suggest that the recently revived 'two-component' hypothesis of coal structure has application to low-rank coals which are mixtures of two distinct components: polymethylenes and a more aromatic network. Bituminous coals, however, appear far more homogeneous. Although experiments can distinguish loosely and tightly bound fractions these fractions appear to consist of similar materials and are differentiated primarily in their molecular weight and degree of connection to the network. These coals appear to behave in a manner that is described by the network decomposition models.
User's Manual for 93-PCGC-2:Pulverized Coal Gasification and Combustion Model (2-Dimensional) with Generalized Coal Reactions Submodel FG-DVC
Brewster, B.S.; Boardman, R.D.; Huque, Z.; Berrondo, S.K.; Eaton, A.M.; Smoot, L.D.; Zhao, Y.; Solomon, P.R.; Hamblen, D.G.; Serio, M.A.; Charpenay, S.; Best, P.E. and Yu, Z.-Z.
US Department of Energy/Morgantown Energy Technology Center/Advanced Fuel Research/Brigham Young University Final Contract Report, Vol. II, 1993. Funded by US Department of Energy and Morgantown Energy Technology Center.
A two-dimensional, steady-state model for describing a variety of reactive and non-reactive flows, including pulverized coal combustion and gasification, is presented. Recent code revisions and additions are described. The model, referred to as 93-PCGC-2, is applicable to cylindrical, axi-symmetric systems. Turbulence is accounted for in both the fluid mechanics equations and the combustion scheme. Radiation from gases, walls, and particles is taken into account using a discrete ordinates method. The particle phase is modeled in a Lagrangian framework, such that mean paths of particle groups are followed. A new coal-general devolatilization submodel (FG-DVC) with coal swelling and char reactivity submodels has been added. The heterogeneous reaction scheme allows for both diffusion and chemical reaction. Major gas-phase reactions are modeled assuming local instantaneous equilibrium, and thus the reaction rates are limited by the turbulent rate of mixing. A thermal and fuel NOx finite rate chemistry submodel is included which integrates chemical kinetics and the statistics of the turbulence. A sorbent injection submodel with sulfur capture is included. The gas phase is described by elliptic partial differential equations that are solved by an iterative line-by-line technique. Under-relaxation is used to achieve numerical stability. Both combustion and gasification environments are permissible. User information and theory are presented, along with sample problems.
Measurement and Modeling of Advanced Coal Conversion Processes
Solomon, P.R.; Hamblen, D.G.; Serio, M.A.; Smoot, L.D. and Brewster, B.S.
US Department of Energy/Morgantown Energy Technology Center/Advanced Fuel Research/Brigham Young University Final Contract Report, Vol. I, 1993. (Also presented at the Coal-fired power systems 93 Conference, Morgantown, WV, June 1993.) Funded by US Department of Energy and Morgantown Energy Technology Center. (This report is available from Advanced Fuel Research, Inc.)
This project included research in the following areas: (1) fundamental high-pressure reaction rate data; (2) large particle oxidation at high pressures; (3) SOx-NOx submodel development; (3) integration of advanced submodels into entrained-flow code, with evaluation and documentation; (4) comprehensive fixed-bed modeling, review, development, evaluation and implementation; (5) generalized fuels feedstock submodel; (6) application of generalized pulverized coal comprehensive code and (7) application of fixed-bed code.
1992
Progress in Coal Pyrolysis
Solomon, P.R.; Fletcher, T.H. and Pugmire, R.J.
Fuel, 1992 (in press). Funded by US Department of Energy and ACERC.
The heterogeneous nature of coal and the complexity of the pyrolysis process has made it very difficult to perform unambiguous experiments to determine the rates and mechanism in coal pyrolysis. The last several years have, however, provided a number of new experimental and theoretical approaches that shed new light on the subject. This paper will consider the recent progress on the topics of: kinetics, the formation of volatile products, network models, crosslinking, rank effects, and the "two-component model of coal structure." In kinetics, recent experiments that measure coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. The rates also agree with those derived from low heating rate experiments. In tar formation and transport, a consensus is being reached on the central role of the tar molecule's volatility in explaining the variation with operating parameters (pressure, heating rate, particle size, etc.) in the tar's amount and molecular weight distribution. Progress in the quantitative prediction of tar and char is being made by recently developed models for the fragmentation of the macromolecular network. These models, which provide quantitative description of the relationship between the chemical structure of the coal and the physical and chemical properties of the resultant pyrolysis products (gas, tar, soot, and char), are an exciting advancement in the understanding of the pyrolysis process. Such models are linking the occurrence of the coal's plastic phase with the "liquid" fragments formed during pyrolysis. On the subject of retrogressive crosslinking reactions, both solvent swelling and NMR measurements confirm important rank dependent differences in reaction rates. These appear related to the oxygen functionalities. Reasonable agreement is also seen for rank variations of kinetics rates derived from low heating rate experiments. Experiments suggest that the recently revived "two-component hypothesis" of coal structure has application to low rank coals that are a mix of polymethylenes and a more aromatic network. Bituminous coals, however, appear far more homogeneous. These coals appear to behave in a manner that is described by the network decomposition models. The presentation will provide a brief report on these topics.
Comprehensive Fixed-Bed Modeling, Review, Development, Evaluation, and Implementation
Solomon, P.R.; Hamblen, D.G.; Serio, M.A.; Smoot, L.D. and Brewster, B.S.
21st, 22nd, and 23rd Quarterly Reports for the US Department of Energy, 1992. Funded by US Department of Energy and Morgantown Energy Technology Center.
The overall objective of this program is the development of predictive capability for the design, scale up, simulation, control and feedstock evaluation in advanced coal conversion devices. This technology is important to reduce the technical and economic risks inherent in utilizing coal, a feedstock whose variable and often unexpected behavior presents a significant challenge. This program is merging significant advances made at Advanced Fuel Research, Inc. (AFR) in measuring and quantitatively describing the mechanisms in coal conversion behavior, with technology being developed at Brigham Young University (BYU) in comprehensive computer codes for mechanistic modeling of entrained-bed gasification. Additional capabilities in predicting pollutant formation is being implemented and the technology was expanded to fixed-bed reactors. The foundation to describe coal-specific conversion behavior is AFR's Functional Group (FG) and Devolatilization, Vaporization, and Crosslinking (DVC) models, developed under previous and on-going METC sponsored programs. These models have demonstrated the capability to describe the time dependent evolution of individual gas species, and the amount and characteristics of tar and char. The combined FG-DVC model has been integrated with BYU's comprehensive two-dimensional reactor mode, PCGC-2, which is a widely used reactor simulation for combustion or gasification. The program includes: 1) validation of the submodels by comparison with laboratory data obtained in this program, 2) extensive validation of the modified comprehensive code by comparison of predicted results with data from bench-scale and process scale investigations of gasification, mild gasification and combustion of coal or coal-derived products in heat engines, and 3) development of well documented user friendly software applicable to a "workstation" environment.
1991
Progress in Coal Pyrolysis
Solomon, P.R.; Fletcher, T.H. and Pugmire, R.J.
Fuel, 1991 (in press). Funded by US Department of Energy and ACERC.
The heterogeneous nature of coal and the complexity of the pyrolysis process has made it very difficult to perform unambiguous experiments to determine the rates and mechanism in coal pyrolysis. The last several years have, however, provided a number of new experimental and theoretical approaches that shed new light on the subject. This paper will consider the recent progress on the topics of: kinetics, the formation of volatile products, network models, crosslinking, rank effects, and the "two-component model of coal structure." In kinetics, recent experiments that measure coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. The rates also agree with those derived from low heating rate experiments. In tar formation and transport, a consensus is being reached on the central role of the tar molecule's volatility in explaining the variation with operating parameters (pressure, heating rate, particle size, etc.) in the tar's amount and molecular weight distribution. Progress in the quantitative prediction of tar and char is being made by recently developed models for the fragmentation of the macromolecular network. These models, which provide quantitative description of the relationship between the chemical structure of the coal and the physical and chemical properties of the resultant pyrolysis products (gas, tar, soot, and char), are an exciting advancement in the understanding of the pyrolysis process. Such models are linking the occurrence of the coal's plastic phase with the "liquid" fragments formed during pyrolysis. On the subject of retrogressive crosslinking reactions, both solvent swelling and NMR measurements confirm important rank dependent differences in reaction rates. These appear related to the oxygen functionalities. Reasonable agreement is also seen for rank variations of kinetics rates derived from low heating rate experiments. Experiments suggest that the recently revived "two-component hypothesis" of coal structure has application to low rank coals that are a mix of polymethylenes and a more aromatic network. Bituminous coals, however, appear far more homogeneous. These coals appear to behave in a manner that is described by the network decomposition models. The presentation will provide a brief report on these topics.
Network Changes During Coal Pyrolysis: Experiment and Theory
Solomon, P.R.; Charpenay, S.; Yu, Z.-Z.; Serio, M.A.; Kroo, E.; Solum, M.S. and Pugmire, R.J.
8th Annual International Pittsburgh Coal Conference, Pittsburgh, PA, October 1991. Funded by US Department of Energy and ACERC.
Coal pyrolysis is a complicated combination of chemical and physical processes in which coal is transformed at elevated temperatures to produce gases, tar, and char. These processes are described in the Functional Group - Depolymerization, Vaporization, and Crosslinking (FG-DVC) model of coal pyrolysis. An important aspect of this model is that crosslinking is rank dependent. This is based on solvent swelling experiments on chars made from coals of different rank. Low rank coals start to loose their solvent swelling ability prior to significant depolymerization at temperatures as low as 200ºC. Including such crosslinking in the FG-DVC model leads to predictions for low rank coals of a highly crosslinked network (exhibited by low solubility and low fluidity in chars) and low tar amounts.
While the model is in good agreement with a variety of data, it is difficult to find experiments to validate the predicted behavior of the network. In this paper we have used CP-MAS, NMR with dipolar dephasing and other techniques to examine the chars changing functional group and network characteristics. The changes in the char composition have been modeled using the FG-DVC model and the results compared with the data for Pittsburgh Seam bituminous coal and Zap lignite.
Progress in Coal Pyrolysis
Solomon, P.R.; Fletcher, T.H. and Pugmire, R.J.
8th Annual International Pittsburgh Coal Conference, Pittsburgh, PA, October 1991. Funded by US Department of Energy and ACERC.
The heterogeneous nature of coal and the complexity of the pyrolysis process has made it very difficult to perform unambiguous experiments to determine the rates and mechanism in coal pyrolysis. The last several years have, however, provided a number of new experimental and theoretical approaches that shed new light on the subject. This paper will consider the recent progress on the topics of: kinetics, the formation of volatile products, network models, crosslinking, rank effects, and the "two-component model of coal structure." In kinetics, recent experiments that measure coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. The rates also agree with those derived from low heating rate experiments. In tar formation and transport, a consensus is being reached on the central role of the tar molecule's volatility in explaining the variation with operating parameters (pressure, heating rate, particle size, etc.) in the tar's amount and molecular weight distribution. Progress in the quantitative prediction of tar and char is being made by recently developed models for the fragmentation of the macromolecular network. These models, which provide quantitative description of the relationship between the chemical structure of the coal and the physical and chemical properties of the resultant pyrolysis products (gas, tar, soot, and char), are an exciting advancement in the understanding of the pyrolysis process. Such models are linking the occurrence of the coal's plastic phase with the "liquid" fragments formed during pyrolysis. On the subject of retrogressive crosslinking reactions, both solvent swelling and NMR measurements confirm important rank dependent differences in reaction rates. These appear related to the oxygen functionalities. Reasonable agreement is also seen for rank variations of kinetics rates derived from low heating rate experiments. Experiments suggest that the recently revived "two-component hypothesis" of coal structure has application to low rank coals that are a mix of polymethylenes and a more aromatic network. Bituminous coals, however, appear far more homogeneous. These coals appear to behave in a manner that is described by the network decomposition models. The presentation will provide a brief report on these topics.
Measurements and Modeling of Advanced Coal Conversion Processes: Fixed-Bed Coal Gasification Modeling
Solomon, P.R.; Hamblen, D.G.; Serio, M.A.; Smoot, L.D. and Brewster, B.S.
Contractors Review Meeting, Morgantown, WV, August 1991. Funded by Morgantown Energy Technology Center.
The overall objective of this program is to understand the chemical and physical mechanisms in coal conversion processes and incorporate this knowledge in computer-aided reactor engineering technology for the purposes of development, evaluation, design, scale up, simulation, control and feedstock evaluation in advanced coal conversion devices. To accomplish this objective, the study will: establish the mechanisms and rates of basic steps in coal conversion processes, incorporate this information into comprehensive computer models for coal conversion processes, evaluate these models, and apply them to gasification, mild gasification and combustion in heat engines.
Measurement and Modeling of Advanced Coal Conversion Processes
Solomon, P.R.; Hamblen, D.G.; Serio, M.A.; Smoot, L.D. and Brewster, B.S.
5th Annual Report for the US Department of Energy, 1991. Funded by Morgantown Energy Technology Center.
The overall objective of this program is the development of predictive capability for the design, scale up, simulation, control and feedstock evaluation in advanced coal conversion devices. This technology is important to reduce the technical and economic risks inherent in utilizing coal a feedstock whose variable and often unexpected behavior presents a significant challenge. This program will merge significant advances made at Advanced Fuel Research, Inc. (AFR) in measuring and quantitatively describing the mechanisms in coal conversion behavior, with technology being developed at Brigham Young University (BYU) in comprehensive computer codes for mechanistic modeling of entrained-bed gasification. Additional capabilities in predicting pollutant formation will be implemented and the technology will be expanded to fixed-bed reactors.
The foundation to describe coal-specific conversion behavior is AFR's Functional Group (FG) and Devolatilization, Vaporization, and Crosslinking (DVC) models, developed under previous and on-going METC sponsored programs. These models have demonstrated the capability to describe the time dependent evolution of individual gas species, and the amount and characteristics of tar and char. The combined FG-DVC model will be integrated with BYU's comprehensive two-dimensional reactor model, PCGC-2, which is currently the most widely used reactor simulation for combustion or gasification. The program includes: i) validation of the submodels by comparison with laboratory data obtained in this program, ii) extensive validation of the modified comprehensive code by comparison of predicted results with data from bench-scale and process scale investigations of gasification, mild gasification and combustion of coal or coal-derived products in heat engines, and iii) development of well documented user friendly software applicable to a "workstation" environment. Success in this program will be a major step in improving the predictive capabilities for coal conversion processes including: demonstrated accuracy and reliability and a generalized "first principles" treatment of coals based on readily obtained composition data. The progress during the fifth year of the program is summarized in the document.
1990
Structure of a Near-Laminar Coal Jet Flame
Brewster, B.S.; Smoot, L.D.; Solomon, P.R. and Markham, J.R.
Tenth Annual Gasification and Gas Stream Cleanup Systems Contractors Review Meeting, Morgantown, WV, 1990. (Also Presented at the Western States Section/The Combustion Institute, San Diego, CA, 1990). Funded by Morgantown Energy Technology Center and Advanced Fuel Research Co.
An advanced 2-D model for pulverized-coal combustion has been modified and applied to a laminar coal flame in a transparent wall reactor. Modifications were made to allow for the up-fired flow configuration, laminarization, and gas buoyancy. A laminarization extension to the k- turbulence model was incorporated. Particle dispersion is sensitive to laminarization and to the value of turbulent particle Schmidt number. Predicted particle velocity and residence time are sensitive to the inclusion of gas buoyancy, which increases the velocity in the center of the reactor and induces a radial, inward flow. Model predictions have been compared with flame measurements to evaluate the comprehensive model that incorporates an advanced devolatilization submodel. Predicted velocities of burning particles agree well with values determined from particle streaks on video recording. Good agreement was also obtained between measured and predicted particle burnout. Discrepancies between measured and predicted particle and gas temperature may be due to neglecting heterogeneous formation of CO2 and the variation of char reactivity with extent of burnout. Discrepancies between predicted bulk gas temperature and measured CO2 gas temperature in the ignition zone can also be explained by the fact that the combustion energy first heats the CO2 that subsequently heats the other gases. Soot decays more slowly than predicted from equilibrium concentrations of condensed carbon.
1989
Solid-State C-13 NMR Studies of Coal Char Structure Evolution
Solum, M.S.; Pugmire, R.J.; Grant, D.M.; Fletcher, T.H. and Solomon, P.R.
Fuel Fiv. Preprints, 34 (4), 1337-1346, 198th ACS National Meeting, Miami, 1989. (Also presented at the Western States Section, The Combustion Institute Spring Meeting, Pullman, Washington, 1989.) Funded by ACERC (National Science Foundation and Associates and Affiliates).
Solid state C-13 NMR techniques have been used to study the evolution of char structure during pyrolysis processes. The effects of residence time, heating rate, and final char temperature are observed. The NMR data demonstrates that extensive loss of aromatic ring bridge material precedes significant change in aromatic cluster size.
Soloman, PR
1994
The Impace of Pyrolysis in Combustion
Solomon, P.R. and Fletcher, T.H.
25th Symposium International on Combustion, 1994 (in press). (Also presented at the 25th Symposium (International) on Combustion, Irvine, CA, Jul-Aug, 1994.) Funded by ACERC.
The pyrolysis process has impacts throughout coal combustion. The roles of pyrolysis in various aspects of 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.
Fossil-Fuel Conversion - Measurement and Modeling
Solomon, P.R.; Serio, M.A.; Hamblen, D.G.; Smoot, L.D.; Brewster, B.S. and Radulovic, P.T.
Proceedings of the Coal-Fired Power Systems 94 - Advances in IGCC and PFBC Review Meeting, Morgantown, West Virginia, June 1994. Funded by US Department of Energy/Morgantown Energy Technology Center.
The main objective of this program is to understand the chemical and physical mechanisms in coal conversion processes and incorporate this technology for the purposes of development, evaluation in advanced coal conversion devices. To accomplish this objective, this program will: 1) provide critical data on the physical and chemical processes in fossil fuel gasifiers and combustors; 2) further develop a set of comprehensive codes; and 3) apply these codes to model various types of combustors and gasifiers (fixed-bed transport reactor, and fluidized-bed for coal and gas turbines for natural gas).
To expand the utilization of coal, it is necessary to reduce the technical and economic risks inherent in operating a feedstock which is highly variable and which sometimes exhibits unexpected and unwanted behavior. Reducing the risks can be achieved by establishing the technology to predict a coal's behavior in a process. This program is creating this predictive capability by merging technology developed at Advanced Fuel Research, Inc. (AFR) in predicting coal devolatilization behavior with technology developed at Brigham Young University (BYU) in comprehensive computer codes for modeling of entrained-bed and fixed-bed reactors and technology developed at the U.S. DOE-METC in comprehensive computer codes for fluidized-bed reactors. These advanced technologies will be further developed to provide: 1) a fixed-bed model capable of predicting combustion and gasification of large coal particles, 2) a transport reactor model, 3) a model for lean premixed combustion of natural gas, and 4) an improved fluidized-bed code with an advanced coal devolatilization chemistry submodel.
1993
Progress in Coal Pyrolysis
Solomon, P.R.; Fletcher, T.H. and Pugmire, R.J.
Fuel, 72:587-597, 1993. Funded, in part, by ACERC.
The heterogeneous nature of coal and the complexity of the pyrolysis process has 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 that shed new light on the subject. This paper considers the recent progress on kinetics, the formation of volatile products, network models, crosslinking, rank effects, and the 'two-component model of coal structure.' Recent experiments that measured coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. These rates also agree with those derived from experiments at low heating rates. In tar formation and transport, a consensus is being reached on the central role of the volatility of tar molecules in explaining the variation with operating conditions (pressure, heating rate, particle size, etc.) of the amounts and molecular weight distribution of tars. Progress in the quantitative prediction of tar and char yields is being made through recently developed models for the fragmentation of the macromolecular coal network. These models, which provide quantitative descriptions of the relations between the chemical structure of the coal and the physical and chemical properties of the pyrolysis products (gas, tar, soot, and char), are an exciting advance in the understanding of the pyrolysis process. Such models are linking the occurrence of the plastic phrase with the 'liquid' fragments formed during pyrolysis. On the subject of retrogressive cross-linking reactions, both solvent swelling and NMR measurements confirm important rank-dependent differences in reaction rates: these appear to be related to the oxygen functionalities. Reasonable agreement is also seen for variations with coal rank of kinetics rates derived from measurements at low heating rates. Experiments suggest that the recently revived 'two-component' hypothesis of coal structure has application to low-rank coals which are mixtures of two distinct components: polymethylenes and a more aromatic network. Bituminous coals, however, appear far more homogeneous. Although experiments can distinguish loosely and tightly bound fractions these fractions appear to consist of similar materials and are differentiated primarily in their molecular weight and degree of connection to the network. These coals appear to behave in a manner that is described by the network decomposition models.
User's Manual for 93-PCGC-2:Pulverized Coal Gasification and Combustion Model (2-Dimensional) with Generalized Coal Reactions Submodel FG-DVC
Brewster, B.S.; Boardman, R.D.; Huque, Z.; Berrondo, S.K.; Eaton, A.M.; Smoot, L.D.; Zhao, Y.; Solomon, P.R.; Hamblen, D.G.; Serio, M.A.; Charpenay, S.; Best, P.E. and Yu, Z.-Z.
US Department of Energy/Morgantown Energy Technology Center/Advanced Fuel Research/Brigham Young University Final Contract Report, Vol. II, 1993. Funded by US Department of Energy and Morgantown Energy Technology Center.
A two-dimensional, steady-state model for describing a variety of reactive and non-reactive flows, including pulverized coal combustion and gasification, is presented. Recent code revisions and additions are described. The model, referred to as 93-PCGC-2, is applicable to cylindrical, axi-symmetric systems. Turbulence is accounted for in both the fluid mechanics equations and the combustion scheme. Radiation from gases, walls, and particles is taken into account using a discrete ordinates method. The particle phase is modeled in a Lagrangian framework, such that mean paths of particle groups are followed. A new coal-general devolatilization submodel (FG-DVC) with coal swelling and char reactivity submodels has been added. The heterogeneous reaction scheme allows for both diffusion and chemical reaction. Major gas-phase reactions are modeled assuming local instantaneous equilibrium, and thus the reaction rates are limited by the turbulent rate of mixing. A thermal and fuel NOx finite rate chemistry submodel is included which integrates chemical kinetics and the statistics of the turbulence. A sorbent injection submodel with sulfur capture is included. The gas phase is described by elliptic partial differential equations that are solved by an iterative line-by-line technique. Under-relaxation is used to achieve numerical stability. Both combustion and gasification environments are permissible. User information and theory are presented, along with sample problems.
Measurement and Modeling of Advanced Coal Conversion Processes
Solomon, P.R.; Hamblen, D.G.; Serio, M.A.; Smoot, L.D. and Brewster, B.S.
US Department of Energy/Morgantown Energy Technology Center/Advanced Fuel Research/Brigham Young University Final Contract Report, Vol. I, 1993. (Also presented at the Coal-fired power systems 93 Conference, Morgantown, WV, June 1993.) Funded by US Department of Energy and Morgantown Energy Technology Center. (This report is available from Advanced Fuel Research, Inc.)
This project included research in the following areas: (1) fundamental high-pressure reaction rate data; (2) large particle oxidation at high pressures; (3) SOx-NOx submodel development; (3) integration of advanced submodels into entrained-flow code, with evaluation and documentation; (4) comprehensive fixed-bed modeling, review, development, evaluation and implementation; (5) generalized fuels feedstock submodel; (6) application of generalized pulverized coal comprehensive code and (7) application of fixed-bed code.
1992
Progress in Coal Pyrolysis
Solomon, P.R.; Fletcher, T.H. and Pugmire, R.J.
Fuel, 1992 (in press). Funded by US Department of Energy and ACERC.
The heterogeneous nature of coal and the complexity of the pyrolysis process has made it very difficult to perform unambiguous experiments to determine the rates and mechanism in coal pyrolysis. The last several years have, however, provided a number of new experimental and theoretical approaches that shed new light on the subject. This paper will consider the recent progress on the topics of: kinetics, the formation of volatile products, network models, crosslinking, rank effects, and the "two-component model of coal structure." In kinetics, recent experiments that measure coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. The rates also agree with those derived from low heating rate experiments. In tar formation and transport, a consensus is being reached on the central role of the tar molecule's volatility in explaining the variation with operating parameters (pressure, heating rate, particle size, etc.) in the tar's amount and molecular weight distribution. Progress in the quantitative prediction of tar and char is being made by recently developed models for the fragmentation of the macromolecular network. These models, which provide quantitative description of the relationship between the chemical structure of the coal and the physical and chemical properties of the resultant pyrolysis products (gas, tar, soot, and char), are an exciting advancement in the understanding of the pyrolysis process. Such models are linking the occurrence of the coal's plastic phase with the "liquid" fragments formed during pyrolysis. On the subject of retrogressive crosslinking reactions, both solvent swelling and NMR measurements confirm important rank dependent differences in reaction rates. These appear related to the oxygen functionalities. Reasonable agreement is also seen for rank variations of kinetics rates derived from low heating rate experiments. Experiments suggest that the recently revived "two-component hypothesis" of coal structure has application to low rank coals that are a mix of polymethylenes and a more aromatic network. Bituminous coals, however, appear far more homogeneous. These coals appear to behave in a manner that is described by the network decomposition models. The presentation will provide a brief report on these topics.
Comprehensive Fixed-Bed Modeling, Review, Development, Evaluation, and Implementation
Solomon, P.R.; Hamblen, D.G.; Serio, M.A.; Smoot, L.D. and Brewster, B.S.
21st, 22nd, and 23rd Quarterly Reports for the US Department of Energy, 1992. Funded by US Department of Energy and Morgantown Energy Technology Center.
The overall objective of this program is the development of predictive capability for the design, scale up, simulation, control and feedstock evaluation in advanced coal conversion devices. This technology is important to reduce the technical and economic risks inherent in utilizing coal, a feedstock whose variable and often unexpected behavior presents a significant challenge. This program is merging significant advances made at Advanced Fuel Research, Inc. (AFR) in measuring and quantitatively describing the mechanisms in coal conversion behavior, with technology being developed at Brigham Young University (BYU) in comprehensive computer codes for mechanistic modeling of entrained-bed gasification. Additional capabilities in predicting pollutant formation is being implemented and the technology was expanded to fixed-bed reactors. The foundation to describe coal-specific conversion behavior is AFR's Functional Group (FG) and Devolatilization, Vaporization, and Crosslinking (DVC) models, developed under previous and on-going METC sponsored programs. These models have demonstrated the capability to describe the time dependent evolution of individual gas species, and the amount and characteristics of tar and char. The combined FG-DVC model has been integrated with BYU's comprehensive two-dimensional reactor mode, PCGC-2, which is a widely used reactor simulation for combustion or gasification. The program includes: 1) validation of the submodels by comparison with laboratory data obtained in this program, 2) extensive validation of the modified comprehensive code by comparison of predicted results with data from bench-scale and process scale investigations of gasification, mild gasification and combustion of coal or coal-derived products in heat engines, and 3) development of well documented user friendly software applicable to a "workstation" environment.
1991
Progress in Coal Pyrolysis
Solomon, P.R.; Fletcher, T.H. and Pugmire, R.J.
Fuel, 1991 (in press). Funded by US Department of Energy and ACERC.
The heterogeneous nature of coal and the complexity of the pyrolysis process has made it very difficult to perform unambiguous experiments to determine the rates and mechanism in coal pyrolysis. The last several years have, however, provided a number of new experimental and theoretical approaches that shed new light on the subject. This paper will consider the recent progress on the topics of: kinetics, the formation of volatile products, network models, crosslinking, rank effects, and the "two-component model of coal structure." In kinetics, recent experiments that measure coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. The rates also agree with those derived from low heating rate experiments. In tar formation and transport, a consensus is being reached on the central role of the tar molecule's volatility in explaining the variation with operating parameters (pressure, heating rate, particle size, etc.) in the tar's amount and molecular weight distribution. Progress in the quantitative prediction of tar and char is being made by recently developed models for the fragmentation of the macromolecular network. These models, which provide quantitative description of the relationship between the chemical structure of the coal and the physical and chemical properties of the resultant pyrolysis products (gas, tar, soot, and char), are an exciting advancement in the understanding of the pyrolysis process. Such models are linking the occurrence of the coal's plastic phase with the "liquid" fragments formed during pyrolysis. On the subject of retrogressive crosslinking reactions, both solvent swelling and NMR measurements confirm important rank dependent differences in reaction rates. These appear related to the oxygen functionalities. Reasonable agreement is also seen for rank variations of kinetics rates derived from low heating rate experiments. Experiments suggest that the recently revived "two-component hypothesis" of coal structure has application to low rank coals that are a mix of polymethylenes and a more aromatic network. Bituminous coals, however, appear far more homogeneous. These coals appear to behave in a manner that is described by the network decomposition models. The presentation will provide a brief report on these topics.
Network Changes During Coal Pyrolysis: Experiment and Theory
Solomon, P.R.; Charpenay, S.; Yu, Z.-Z.; Serio, M.A.; Kroo, E.; Solum, M.S. and Pugmire, R.J.
8th Annual International Pittsburgh Coal Conference, Pittsburgh, PA, October 1991. Funded by US Department of Energy and ACERC.
Coal pyrolysis is a complicated combination of chemical and physical processes in which coal is transformed at elevated temperatures to produce gases, tar, and char. These processes are described in the Functional Group - Depolymerization, Vaporization, and Crosslinking (FG-DVC) model of coal pyrolysis. An important aspect of this model is that crosslinking is rank dependent. This is based on solvent swelling experiments on chars made from coals of different rank. Low rank coals start to loose their solvent swelling ability prior to significant depolymerization at temperatures as low as 200ºC. Including such crosslinking in the FG-DVC model leads to predictions for low rank coals of a highly crosslinked network (exhibited by low solubility and low fluidity in chars) and low tar amounts.
While the model is in good agreement with a variety of data, it is difficult to find experiments to validate the predicted behavior of the network. In this paper we have used CP-MAS, NMR with dipolar dephasing and other techniques to examine the chars changing functional group and network characteristics. The changes in the char composition have been modeled using the FG-DVC model and the results compared with the data for Pittsburgh Seam bituminous coal and Zap lignite.
Progress in Coal Pyrolysis
Solomon, P.R.; Fletcher, T.H. and Pugmire, R.J.
8th Annual International Pittsburgh Coal Conference, Pittsburgh, PA, October 1991. Funded by US Department of Energy and ACERC.
The heterogeneous nature of coal and the complexity of the pyrolysis process has made it very difficult to perform unambiguous experiments to determine the rates and mechanism in coal pyrolysis. The last several years have, however, provided a number of new experimental and theoretical approaches that shed new light on the subject. This paper will consider the recent progress on the topics of: kinetics, the formation of volatile products, network models, crosslinking, rank effects, and the "two-component model of coal structure." In kinetics, recent experiments that measure coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. The rates also agree with those derived from low heating rate experiments. In tar formation and transport, a consensus is being reached on the central role of the tar molecule's volatility in explaining the variation with operating parameters (pressure, heating rate, particle size, etc.) in the tar's amount and molecular weight distribution. Progress in the quantitative prediction of tar and char is being made by recently developed models for the fragmentation of the macromolecular network. These models, which provide quantitative description of the relationship between the chemical structure of the coal and the physical and chemical properties of the resultant pyrolysis products (gas, tar, soot, and char), are an exciting advancement in the understanding of the pyrolysis process. Such models are linking the occurrence of the coal's plastic phase with the "liquid" fragments formed during pyrolysis. On the subject of retrogressive crosslinking reactions, both solvent swelling and NMR measurements confirm important rank dependent differences in reaction rates. These appear related to the oxygen functionalities. Reasonable agreement is also seen for rank variations of kinetics rates derived from low heating rate experiments. Experiments suggest that the recently revived "two-component hypothesis" of coal structure has application to low rank coals that are a mix of polymethylenes and a more aromatic network. Bituminous coals, however, appear far more homogeneous. These coals appear to behave in a manner that is described by the network decomposition models. The presentation will provide a brief report on these topics.
Measurements and Modeling of Advanced Coal Conversion Processes: Fixed-Bed Coal Gasification Modeling
Solomon, P.R.; Hamblen, D.G.; Serio, M.A.; Smoot, L.D. and Brewster, B.S.
Contractors Review Meeting, Morgantown, WV, August 1991. Funded by Morgantown Energy Technology Center.
The overall objective of this program is to understand the chemical and physical mechanisms in coal conversion processes and incorporate this knowledge in computer-aided reactor engineering technology for the purposes of development, evaluation, design, scale up, simulation, control and feedstock evaluation in advanced coal conversion devices. To accomplish this objective, the study will: establish the mechanisms and rates of basic steps in coal conversion processes, incorporate this information into comprehensive computer models for coal conversion processes, evaluate these models, and apply them to gasification, mild gasification and combustion in heat engines.
Measurement and Modeling of Advanced Coal Conversion Processes
Solomon, P.R.; Hamblen, D.G.; Serio, M.A.; Smoot, L.D. and Brewster, B.S.
5th Annual Report for the US Department of Energy, 1991. Funded by Morgantown Energy Technology Center.
The overall objective of this program is the development of predictive capability for the design, scale up, simulation, control and feedstock evaluation in advanced coal conversion devices. This technology is important to reduce the technical and economic risks inherent in utilizing coal a feedstock whose variable and often unexpected behavior presents a significant challenge. This program will merge significant advances made at Advanced Fuel Research, Inc. (AFR) in measuring and quantitatively describing the mechanisms in coal conversion behavior, with technology being developed at Brigham Young University (BYU) in comprehensive computer codes for mechanistic modeling of entrained-bed gasification. Additional capabilities in predicting pollutant formation will be implemented and the technology will be expanded to fixed-bed reactors.
The foundation to describe coal-specific conversion behavior is AFR's Functional Group (FG) and Devolatilization, Vaporization, and Crosslinking (DVC) models, developed under previous and on-going METC sponsored programs. These models have demonstrated the capability to describe the time dependent evolution of individual gas species, and the amount and characteristics of tar and char. The combined FG-DVC model will be integrated with BYU's comprehensive two-dimensional reactor model, PCGC-2, which is currently the most widely used reactor simulation for combustion or gasification. The program includes: i) validation of the submodels by comparison with laboratory data obtained in this program, ii) extensive validation of the modified comprehensive code by comparison of predicted results with data from bench-scale and process scale investigations of gasification, mild gasification and combustion of coal or coal-derived products in heat engines, and iii) development of well documented user friendly software applicable to a "workstation" environment. Success in this program will be a major step in improving the predictive capabilities for coal conversion processes including: demonstrated accuracy and reliability and a generalized "first principles" treatment of coals based on readily obtained composition data. The progress during the fifth year of the program is summarized in the document.
1990
Structure of a Near-Laminar Coal Jet Flame
Brewster, B.S.; Smoot, L.D.; Solomon, P.R. and Markham, J.R.
Tenth Annual Gasification and Gas Stream Cleanup Systems Contractors Review Meeting, Morgantown, WV, 1990. (Also Presented at the Western States Section/The Combustion Institute, San Diego, CA, 1990). Funded by Morgantown Energy Technology Center and Advanced Fuel Research Co.
An advanced 2-D model for pulverized-coal combustion has been modified and applied to a laminar coal flame in a transparent wall reactor. Modifications were made to allow for the up-fired flow configuration, laminarization, and gas buoyancy. A laminarization extension to the k- turbulence model was incorporated. Particle dispersion is sensitive to laminarization and to the value of turbulent particle Schmidt number. Predicted particle velocity and residence time are sensitive to the inclusion of gas buoyancy, which increases the velocity in the center of the reactor and induces a radial, inward flow. Model predictions have been compared with flame measurements to evaluate the comprehensive model that incorporates an advanced devolatilization submodel. Predicted velocities of burning particles agree well with values determined from particle streaks on video recording. Good agreement was also obtained between measured and predicted particle burnout. Discrepancies between measured and predicted particle and gas temperature may be due to neglecting heterogeneous formation of CO2 and the variation of char reactivity with extent of burnout. Discrepancies between predicted bulk gas temperature and measured CO2 gas temperature in the ignition zone can also be explained by the fact that the combustion energy first heats the CO2 that subsequently heats the other gases. Soot decays more slowly than predicted from equilibrium concentrations of condensed carbon.
1989
Solid-State C-13 NMR Studies of Coal Char Structure Evolution
Solum, M.S.; Pugmire, R.J.; Grant, D.M.; Fletcher, T.H. and Solomon, P.R.
Fuel Fiv. Preprints, 34 (4), 1337-1346, 198th ACS National Meeting, Miami, 1989. (Also presented at the Western States Section, The Combustion Institute Spring Meeting, Pullman, Washington, 1989.) Funded by ACERC (National Science Foundation and Associates and Affiliates).
Solid state C-13 NMR techniques have been used to study the evolution of char structure during pyrolysis processes. The effects of residence time, heating rate, and final char temperature are observed. The NMR data demonstrates that extensive loss of aromatic ring bridge material precedes significant change in aromatic cluster size.