DuBow, J
1994
High Speed, Two-Wavelength Radiation Thermometry of Single Micro Particles During CO2 Laser Heating
Maswadeh, W.; Tripathi, A.; Arnold, N.S.; DuBow, J. and Meuzelaar, H.L.C.
Journal of Analytical and Appl. Pyrolysis, 28:55-70, 1994. Funded by ACERC.
A high speed, two-wavelength radiation thermometer that is capable of monitoring the surface temperature of 50-150 µm diameter particles in the 600-2000 K range at heating rates of up to 106 K/s, characteristic of pulverized coal combustion, was designed and constructed. To meet the above characteristics, special attention was paid to detector wavelength range and speed, detection electronics and optical system alignment. The thermometer was calibrated using an in-house constructed, black cavity radiation source. Spherocarb model particles, which have a more uniform size; physical properties and emissivity than coal particles, were used to demonstrate the level of short-term reproducibility attainable. Consistent, reproducible temperature-time profiles obtained for particles from different coals indicate that non-grey effects do not dominate these measurements.
1993
Development of a Laser Devolatilization Gas Chromatography/Mass Spectrometry Technique for Single Coal Particles
Maswadeh, W.; Arnold, N.S.; McClennen, W.H.; Tripathi, A.; DuBow, J. and Meuzelaar, H.L.C.
Energy & Fuels, 7 (6):1006-1012, 1993. Funded by ACERC.
A CO2 laser Py-GC/MS system capable of identifying substantial numbers of pyrolysis products from single coal particles in the 50-15-µm range is reported. Also, a specially designed two-wavelength radiation thermometer module with integral video microscope produces reliable temperature/time profiles of single coal particles during rapid laser heating. A novel microbeam footprint technique using thin quartz wafers in combination with videomicroscopy greatly facilitates laser beam focusing and alignment operations. Comparison of an EDB type particle levitator with an EM grid type particle support system reveals considerable advantages of the EM grid approach with regard to tar collection efficiency, particle position stability, particle visualization, and recoverability of residual char particles. However, possible cooling effects of the grid on highly thermoplastic particles require further study. The feasibility of simulating PCC conditions with regard to heating rates and final particle temperatures is demonstrated with complete devolatilization of 100 µm diameter particle being observed within 10 ms. The nature and relative abundance of major pyrolysis products observed at typical laser heating rates (>=105 K/s) are found to be closely similar to those observed with Curie-point pyrolysis techniques at heating rates in the 10²-10³ K/s range. Spherocarb particles of approximately 102-µm diameter, e.g., impregnated with suitable coal tar compounds are shown to provide useful model samples for system optimization and calibration purposes.
High Speed, Two-Wavelength Radiation Thermometry of Single Micro Particles During CO2 Laser Heating
Maswadeh, W.; Tripathi, A.; Arnold, N.S.; DuBow, J. and Meuzelaar, H.L.C.
Journal of Analytical and Appl. Pyrolysis, 1993 (in press). Funded by ACERC.
A high speed, two-wavelength radiation thermometer that is capable of monitoring the surface temperature of 50-150 µm diameter particles in the 600-2000 K range at heating rates of up to 106 K/s, characteristic of pulverized coal combustion, was designed and constructed. To meet the above characteristics, special attention was paid to detector wavelength range and speed, detection electronics and optical system alignment. The thermometer was calibrated using an in-house constructed, black cavity radiation source. Spherocarb model particles, which have a more uniform size; physical properties and emissivity than coal particles, were used to demonstrate the level of short-term reproducibility attainable. Consistent, reproducible temperature-time profiles obtained for particles from different coals indicate that non-grey effects do not dominate these measurements.
1992
Structure/Reactivity Studies of Single Coal Particles at Very High Heating Rates by Laser Pyrolysis GC/MS
Maswadeh, W.; Fu, Y.; Dubow, J. and Meuzelaar, H.L.C.
ACS Division of Fuel Chemistry Preprints, 37(1):699-706, 1992 (203rd ACS National Meeting, San Francisco, CA, April 1992). Funded by ACERC.
Recently, Maswadeh et al. reported on the design, construction and testing of a single particle levitation/laser devolatilization apparatus featuring an on-line gas chromatograph/mass spectrometer (GC/MS) system, enabling coal devolatilization experiments of heating rates in the 10-5-106 K/s range. Analysis of bituminous coal particles revealed a high degree of qualitative correspondence with pyrolysis patterns obtained at much slower (10-2-100 K/s range) TG/MS heating rates, thus providing mechanistic justification for extrapolating kinetic parameters obtained by slow pyrolysis techniques (e.g., TG/MS and TG/IR) to the high heating rates characteristic of full scale, suspension fired coal combustors.
A second observation made with the aid of laser pyrolysis GC/MS was that the distribution of devolatilization products observed at very high heating rates was not measurably influenced by the presence or absence of air. A subsequent redesign of the system permitted the use of electron microscopy (EM) grids to support individual coal particles, thereby simplifying the experimental set up, improving collection efficiency of volatile products and facilitating optical alignment of the particles (microscopy, optical micropyrometry) as well as retrieval of residual char particles.
1990
Effect of Mineral Matter on Coal Devolatilization Kinetics
Bae, I.; Maswadeh, W.; Yun, Y.; Meuzelaar, H.L.C. and DuBow, J.
Accepted for publication in the ACS National Meeting Preprints, Boston, Massechusetts,Spring, 1990. Funded by ACERC (National Science Foundation and Associates and Affiliates).
Coal pyrolysis is a fundamental first step in combustion processes. Yet coals exhibit a wide variation in pyrolysis behaviors. The origins of these wide variations are, for a given set of experimental conditions, both structural and compositional in nature. Because of its thermochemical and catalytic properties, mineral matter plays an important role in both the thermodynamics (product mixes, activation energies) and kinetics of coal pyrolysis. The issue is further complicated by the manner in which mineral matter is distributed in various coals. While many classifications are possible, grouping into three classics is most common. These classes are: (1) discrete minerals such as clays, oxides (basic and acidic) and sulfides; (2) organometallic matter such as ion-exchangeable cations; and (3) dispersed trace elements and compounds. A considerable body of research exists for studying equilibrium and non-equilibrium effects of the various forms of coal minerals on coal combustion.
In the present paper the mineral matter effects on coal pyrolysis are being analyzed using an approach whereby observable spectroscopic (TG/MS) differences in the pyrolytic decomposition between fresh coal and demineralized coal are reconstructed from the sum of mineral matter effects on pyrolysis arising from adding back, singly and in pairs, individual minerals in various forms.
Mineral Matter Effects in Coal Pyrolysis
Bae, I.; Anani, M.; Maswadeh, W.; Yun, Y.; Meuzelaar, H.L.C. and DuBow, J.
199th ACS National Meeting, 35 (2), 489-493, Boston, Massachusetts, 1990. Funded by ACERC.
Coal pyrolysis is a fundamental first step in combustion processes. Yet coals exhibit a wide variation in pyrolysis behaviors. The origins of these wide variations are for a given set of experimental conditions, both structural and compositional in nature. Because of its thermochemical and catalytic properties, mineral matter plays an important role in both the thermodynamics (product mixes, activation energies) and kinetics of coal pyrolysis. The issue is further complicated by the manner in which mineral matter is distributed in various coals. While many classifications are possible, grouping into three classes is most common. These classes are: (1) discrete minerals such as clays, oxides (basic and acidic) and sulfides; (2) organometallic matter such as ion-exchangeable cations; and (3) dispersed trace elements and compounds. A considerable body of research exists for studying equilibrium and non-equilibrium effects of the various forms of coal minerals on coal combustion.
In the present paper the mineral matter effects on coal pyrolysis are being analyzed using an approach whereby observable spectroscopic (TG/MS) differences in the pyrolytic decomposition between fresh coal and demineralized coal are reconstructed from the sum of mineral matter effects on pyrolysis arising from adding back, singly, and in pairs, individual minerals in various forms.
DuBow, J
1994
High Speed, Two-Wavelength Radiation Thermometry of Single Micro Particles During CO2 Laser Heating
Maswadeh, W.; Tripathi, A.; Arnold, N.S.; DuBow, J. and Meuzelaar, H.L.C.
Journal of Analytical and Appl. Pyrolysis, 28:55-70, 1994. Funded by ACERC.
A high speed, two-wavelength radiation thermometer that is capable of monitoring the surface temperature of 50-150 µm diameter particles in the 600-2000 K range at heating rates of up to 106 K/s, characteristic of pulverized coal combustion, was designed and constructed. To meet the above characteristics, special attention was paid to detector wavelength range and speed, detection electronics and optical system alignment. The thermometer was calibrated using an in-house constructed, black cavity radiation source. Spherocarb model particles, which have a more uniform size; physical properties and emissivity than coal particles, were used to demonstrate the level of short-term reproducibility attainable. Consistent, reproducible temperature-time profiles obtained for particles from different coals indicate that non-grey effects do not dominate these measurements.
1993
Development of a Laser Devolatilization Gas Chromatography/Mass Spectrometry Technique for Single Coal Particles
Maswadeh, W.; Arnold, N.S.; McClennen, W.H.; Tripathi, A.; DuBow, J. and Meuzelaar, H.L.C.
Energy & Fuels, 7 (6):1006-1012, 1993. Funded by ACERC.
A CO2 laser Py-GC/MS system capable of identifying substantial numbers of pyrolysis products from single coal particles in the 50-15-µm range is reported. Also, a specially designed two-wavelength radiation thermometer module with integral video microscope produces reliable temperature/time profiles of single coal particles during rapid laser heating. A novel microbeam footprint technique using thin quartz wafers in combination with videomicroscopy greatly facilitates laser beam focusing and alignment operations. Comparison of an EDB type particle levitator with an EM grid type particle support system reveals considerable advantages of the EM grid approach with regard to tar collection efficiency, particle position stability, particle visualization, and recoverability of residual char particles. However, possible cooling effects of the grid on highly thermoplastic particles require further study. The feasibility of simulating PCC conditions with regard to heating rates and final particle temperatures is demonstrated with complete devolatilization of 100 µm diameter particle being observed within 10 ms. The nature and relative abundance of major pyrolysis products observed at typical laser heating rates (>=105 K/s) are found to be closely similar to those observed with Curie-point pyrolysis techniques at heating rates in the 10²-10³ K/s range. Spherocarb particles of approximately 102-µm diameter, e.g., impregnated with suitable coal tar compounds are shown to provide useful model samples for system optimization and calibration purposes.
High Speed, Two-Wavelength Radiation Thermometry of Single Micro Particles During CO2 Laser Heating
Maswadeh, W.; Tripathi, A.; Arnold, N.S.; DuBow, J. and Meuzelaar, H.L.C.
Journal of Analytical and Appl. Pyrolysis, 1993 (in press). Funded by ACERC.
A high speed, two-wavelength radiation thermometer that is capable of monitoring the surface temperature of 50-150 µm diameter particles in the 600-2000 K range at heating rates of up to 106 K/s, characteristic of pulverized coal combustion, was designed and constructed. To meet the above characteristics, special attention was paid to detector wavelength range and speed, detection electronics and optical system alignment. The thermometer was calibrated using an in-house constructed, black cavity radiation source. Spherocarb model particles, which have a more uniform size; physical properties and emissivity than coal particles, were used to demonstrate the level of short-term reproducibility attainable. Consistent, reproducible temperature-time profiles obtained for particles from different coals indicate that non-grey effects do not dominate these measurements.
1992
Structure/Reactivity Studies of Single Coal Particles at Very High Heating Rates by Laser Pyrolysis GC/MS
Maswadeh, W.; Fu, Y.; Dubow, J. and Meuzelaar, H.L.C.
ACS Division of Fuel Chemistry Preprints, 37(1):699-706, 1992 (203rd ACS National Meeting, San Francisco, CA, April 1992). Funded by ACERC.
Recently, Maswadeh et al. reported on the design, construction and testing of a single particle levitation/laser devolatilization apparatus featuring an on-line gas chromatograph/mass spectrometer (GC/MS) system, enabling coal devolatilization experiments of heating rates in the 10-5-106 K/s range. Analysis of bituminous coal particles revealed a high degree of qualitative correspondence with pyrolysis patterns obtained at much slower (10-2-100 K/s range) TG/MS heating rates, thus providing mechanistic justification for extrapolating kinetic parameters obtained by slow pyrolysis techniques (e.g., TG/MS and TG/IR) to the high heating rates characteristic of full scale, suspension fired coal combustors.
A second observation made with the aid of laser pyrolysis GC/MS was that the distribution of devolatilization products observed at very high heating rates was not measurably influenced by the presence or absence of air. A subsequent redesign of the system permitted the use of electron microscopy (EM) grids to support individual coal particles, thereby simplifying the experimental set up, improving collection efficiency of volatile products and facilitating optical alignment of the particles (microscopy, optical micropyrometry) as well as retrieval of residual char particles.
1990
Effect of Mineral Matter on Coal Devolatilization Kinetics
Bae, I.; Maswadeh, W.; Yun, Y.; Meuzelaar, H.L.C. and DuBow, J.
Accepted for publication in the ACS National Meeting Preprints, Boston, Massechusetts,Spring, 1990. Funded by ACERC (National Science Foundation and Associates and Affiliates).
Coal pyrolysis is a fundamental first step in combustion processes. Yet coals exhibit a wide variation in pyrolysis behaviors. The origins of these wide variations are, for a given set of experimental conditions, both structural and compositional in nature. Because of its thermochemical and catalytic properties, mineral matter plays an important role in both the thermodynamics (product mixes, activation energies) and kinetics of coal pyrolysis. The issue is further complicated by the manner in which mineral matter is distributed in various coals. While many classifications are possible, grouping into three classics is most common. These classes are: (1) discrete minerals such as clays, oxides (basic and acidic) and sulfides; (2) organometallic matter such as ion-exchangeable cations; and (3) dispersed trace elements and compounds. A considerable body of research exists for studying equilibrium and non-equilibrium effects of the various forms of coal minerals on coal combustion.
In the present paper the mineral matter effects on coal pyrolysis are being analyzed using an approach whereby observable spectroscopic (TG/MS) differences in the pyrolytic decomposition between fresh coal and demineralized coal are reconstructed from the sum of mineral matter effects on pyrolysis arising from adding back, singly and in pairs, individual minerals in various forms.
Mineral Matter Effects in Coal Pyrolysis
Bae, I.; Anani, M.; Maswadeh, W.; Yun, Y.; Meuzelaar, H.L.C. and DuBow, J.
199th ACS National Meeting, 35 (2), 489-493, Boston, Massachusetts, 1990. Funded by ACERC.
Coal pyrolysis is a fundamental first step in combustion processes. Yet coals exhibit a wide variation in pyrolysis behaviors. The origins of these wide variations are for a given set of experimental conditions, both structural and compositional in nature. Because of its thermochemical and catalytic properties, mineral matter plays an important role in both the thermodynamics (product mixes, activation energies) and kinetics of coal pyrolysis. The issue is further complicated by the manner in which mineral matter is distributed in various coals. While many classifications are possible, grouping into three classes is most common. These classes are: (1) discrete minerals such as clays, oxides (basic and acidic) and sulfides; (2) organometallic matter such as ion-exchangeable cations; and (3) dispersed trace elements and compounds. A considerable body of research exists for studying equilibrium and non-equilibrium effects of the various forms of coal minerals on coal combustion.
In the present paper the mineral matter effects on coal pyrolysis are being analyzed using an approach whereby observable spectroscopic (TG/MS) differences in the pyrolytic decomposition between fresh coal and demineralized coal are reconstructed from the sum of mineral matter effects on pyrolysis arising from adding back, singly, and in pairs, individual minerals in various forms.