Ma, J
2000
Transformations of Coal-Derived Soot at Elevated Temperature
Rigby, J.R.; Ma, J.; Webb, B.W. and Fletcher, T.H.
Accepted for publication in Energy & Fuels (2000).
Contact: Webb
1997
Soot in Coal Combustion Systems
Fletcher, T.H.; Ma, J.; Rigby, J.R.; Brown, A.L. and Webb, B.W.
Prog. Energy Combust. Sci., 23:283-301(1997). Funded by ACERC.
Soot is generated from coal when volatile matter, tar in particular, undergoes secondary reactions at high temperatures. A description of soot in coal flames allows better calculations of radiative transfer and temperatures in near-burner regions, which in turn allows more accurate predictions of NOx formation in coal-fired furnaces. Experiments are reviewed that examine the formation, agglomeration and properties of coal-derived soot, including pyrolysis experiments and combustion experiments. This review includes the types of experiments performed, the soot yields obtained, the size of the soot particles and agglomerates, the optical properties of soot, the relationship between coal-derived soot and soot form simple hydrocarbons, and attempts to model soot in coal flames.
1996
Soot Formation During Coal Pyrolysis
Ma, J.
Soot Formation During Coal Pyrolysis, Ph.D./BYU, August 1996. Advisor: Fletcher
Conversion of Coal Tar to Soot During Coal Pyrolysis in a Post-Flame Environment
Ma, J.; Fletcher, T.H. and Webb, B.W.
Twenty-Sixth Symposium (International) on Combustion, (in press) 1996. (Also presented at the Twenty-Sixth Symposium (International) on Combustion, Naples, Italy, July, 1996.) Funded by ACERC.
Coal pyrolysis experiments were performed in the post-flame region of CH4/H2/air flat flame burner running in fuel-rich conditions, where the temperature and gas compositions were similar to those in the near burner region of a large-scale coal-fired furnace. Volatiles released form the coal particles formed a cloud of soot particles at high temperatures in the absence of oxygen. The soot particles in the cloud were collected at different residence times using a water-cooled, nitrogen-quenched suction probe. The test variables included the reaction temperature and coal type. Soot yields in terms of weight percentage of dry ash-free coal were measured based on the bulk soot collection experiments. The measured soot yields were related to coal rank, reaction temperature, and residence time. Size changes of soot particles due to soot agglomeration were also observed. The information obtained bout coal-derived soot is useful in predictions of radiative heat transfer and pollutant formations in the near-burner region of pulverized coal-furnaces.
The Absorption-Line Blackbody Distribution
Denison, M.K. and Webb, B.W.
Proceedings of the First International Symposium of Radiative Heat Transfer, 1:228-238, 1996. (Presented at the First International Symposium of Radiative Heat Transfer, Kusadasi, Turkey, August, 1995.) Funded in part by ACERC.
The previously published mathematical correlations of the absorption-line blackbody distribution function, central to the spectral-line based weighted-sum-of-gray-gases model (SLW), have been extended to elevate pressures by introducing a dependence on an effective broadening pressure. Comparison between experimentally determined total emissivities and those calculated with the model show good agreement. Agreement at elevated pressure between line-by-line benchmarks and model predictions is also demonstrated.
1993
Chemical Structural Features of Coal Chars, Tars, and Char Extracts During Rapid Pyrolysis Using C-13 and H-1 NMR Spectroscopy
Fletcher, T.H.; Solum, M.S.; Pugmire, R.J.; Grant, D.M.; Bai, S.; Ma, J. and Woods, S.
7th International Conference on Coal Science, Banff, Alberta, Canada, September 1993 (in press). Funded by ACERC.
Structural characteristics have been determined for parent coals and for chars collected at different stages of pyrolysis. Recent work has focused on trying to understand the relationship between chemical structural features of the unreacted coal and the devolatilization and char oxidation phenomena. Models of coal devolatilization have recently related devolatilization behavior to the structure of the parent coal and the initial amount of pyridine extracts. Fong et al. used pyridine extraction methods to quantify the amount of metaplast formed during pyrolysis of a Pittsburgh #8 coal. These experiments demonstrated that under moderate heating conditions (~500 K/s to 873 K), as much as 80% of the initial coal was transformed into a combination of extractable material and volatiles. The work presented here is an examination of the pyridine extraction procedure of the Argonne Premium coal samples and the detailed study of the carbon skeletal structure of the extracts and the extraction residues from these coals. This is the first stage of an experimental program to examine the yield and chemical features of extracts of coal chars collected as a function of time during pyrolysis.
Properties of Soot from Coal Tar
Ma, J.; Dean, M.; Rossman, J.; Sastrawinata, T.; Webb, B.W. and Fletcher, T.H.
Meeting of the Western States Section of the Combustion Institute, October 1993, Menlo Park, CA. Funded by ACERC.
Soot properties and formation mechanisms have been extensively studied in gas flames such as acetylene and propane. However, relatively little information is known concerning soot properties in coal combustion. Coal tar is the precursor to soot in coal combustion, so that the aromatic ring structures are already present. Experiments are presented to show the size of soot particles generated from coal tar at high temperature. A flat flame burner is used to provide the high temperature environment. Coal particles are entrained along the centerline of the reactor, and release pyrolysis products into the hot surrounding gas. The tar/soot cloud diffuses radially away from the centerline as it is convected axially in the flow reactor. The soot sampling system inserts a carbon-coated microscope grid radially into the soot cloud at different residence times, and the soot particle deposit thermophoretically. Soot particles are then analyzed using transmission electron microscopy (TEM) at magnifications as high as 150,000. Distinct soot particles with approximate diameters of 25 nm were observed along with particle agglomerates consisting of multiple primary particles. The observed agglomerate size increases with residence time in the reactor. Liquid-like unstable deposits (believed to be condensed tar) were also observed. These qualitative observations are important for descriptions of soot radiation from coal flames.
Ma, J
2000
Transformations of Coal-Derived Soot at Elevated Temperature
Rigby, J.R.; Ma, J.; Webb, B.W. and Fletcher, T.H.
Accepted for publication in Energy & Fuels (2000).
Contact: Webb
1997
Soot in Coal Combustion Systems
Fletcher, T.H.; Ma, J.; Rigby, J.R.; Brown, A.L. and Webb, B.W.
Prog. Energy Combust. Sci., 23:283-301(1997). Funded by ACERC.
Soot is generated from coal when volatile matter, tar in particular, undergoes secondary reactions at high temperatures. A description of soot in coal flames allows better calculations of radiative transfer and temperatures in near-burner regions, which in turn allows more accurate predictions of NOx formation in coal-fired furnaces. Experiments are reviewed that examine the formation, agglomeration and properties of coal-derived soot, including pyrolysis experiments and combustion experiments. This review includes the types of experiments performed, the soot yields obtained, the size of the soot particles and agglomerates, the optical properties of soot, the relationship between coal-derived soot and soot form simple hydrocarbons, and attempts to model soot in coal flames.
1996
Soot Formation During Coal Pyrolysis
Ma, J.
Soot Formation During Coal Pyrolysis, Ph.D./BYU, August 1996. Advisor: Fletcher
Conversion of Coal Tar to Soot During Coal Pyrolysis in a Post-Flame Environment
Ma, J.; Fletcher, T.H. and Webb, B.W.
Twenty-Sixth Symposium (International) on Combustion, (in press) 1996. (Also presented at the Twenty-Sixth Symposium (International) on Combustion, Naples, Italy, July, 1996.) Funded by ACERC.
Coal pyrolysis experiments were performed in the post-flame region of CH4/H2/air flat flame burner running in fuel-rich conditions, where the temperature and gas compositions were similar to those in the near burner region of a large-scale coal-fired furnace. Volatiles released form the coal particles formed a cloud of soot particles at high temperatures in the absence of oxygen. The soot particles in the cloud were collected at different residence times using a water-cooled, nitrogen-quenched suction probe. The test variables included the reaction temperature and coal type. Soot yields in terms of weight percentage of dry ash-free coal were measured based on the bulk soot collection experiments. The measured soot yields were related to coal rank, reaction temperature, and residence time. Size changes of soot particles due to soot agglomeration were also observed. The information obtained bout coal-derived soot is useful in predictions of radiative heat transfer and pollutant formations in the near-burner region of pulverized coal-furnaces.
The Absorption-Line Blackbody Distribution
Denison, M.K. and Webb, B.W.
Proceedings of the First International Symposium of Radiative Heat Transfer, 1:228-238, 1996. (Presented at the First International Symposium of Radiative Heat Transfer, Kusadasi, Turkey, August, 1995.) Funded in part by ACERC.
The previously published mathematical correlations of the absorption-line blackbody distribution function, central to the spectral-line based weighted-sum-of-gray-gases model (SLW), have been extended to elevate pressures by introducing a dependence on an effective broadening pressure. Comparison between experimentally determined total emissivities and those calculated with the model show good agreement. Agreement at elevated pressure between line-by-line benchmarks and model predictions is also demonstrated.
1993
Chemical Structural Features of Coal Chars, Tars, and Char Extracts During Rapid Pyrolysis Using C-13 and H-1 NMR Spectroscopy
Fletcher, T.H.; Solum, M.S.; Pugmire, R.J.; Grant, D.M.; Bai, S.; Ma, J. and Woods, S.
7th International Conference on Coal Science, Banff, Alberta, Canada, September 1993 (in press). Funded by ACERC.
Structural characteristics have been determined for parent coals and for chars collected at different stages of pyrolysis. Recent work has focused on trying to understand the relationship between chemical structural features of the unreacted coal and the devolatilization and char oxidation phenomena. Models of coal devolatilization have recently related devolatilization behavior to the structure of the parent coal and the initial amount of pyridine extracts. Fong et al. used pyridine extraction methods to quantify the amount of metaplast formed during pyrolysis of a Pittsburgh #8 coal. These experiments demonstrated that under moderate heating conditions (~500 K/s to 873 K), as much as 80% of the initial coal was transformed into a combination of extractable material and volatiles. The work presented here is an examination of the pyridine extraction procedure of the Argonne Premium coal samples and the detailed study of the carbon skeletal structure of the extracts and the extraction residues from these coals. This is the first stage of an experimental program to examine the yield and chemical features of extracts of coal chars collected as a function of time during pyrolysis.
Properties of Soot from Coal Tar
Ma, J.; Dean, M.; Rossman, J.; Sastrawinata, T.; Webb, B.W. and Fletcher, T.H.
Meeting of the Western States Section of the Combustion Institute, October 1993, Menlo Park, CA. Funded by ACERC.
Soot properties and formation mechanisms have been extensively studied in gas flames such as acetylene and propane. However, relatively little information is known concerning soot properties in coal combustion. Coal tar is the precursor to soot in coal combustion, so that the aromatic ring structures are already present. Experiments are presented to show the size of soot particles generated from coal tar at high temperature. A flat flame burner is used to provide the high temperature environment. Coal particles are entrained along the centerline of the reactor, and release pyrolysis products into the hot surrounding gas. The tar/soot cloud diffuses radially away from the centerline as it is convected axially in the flow reactor. The soot sampling system inserts a carbon-coated microscope grid radially into the soot cloud at different residence times, and the soot particle deposit thermophoretically. Soot particles are then analyzed using transmission electron microscopy (TEM) at magnifications as high as 150,000. Distinct soot particles with approximate diameters of 25 nm were observed along with particle agglomerates consisting of multiple primary particles. The observed agglomerate size increases with residence time in the reactor. Liquid-like unstable deposits (believed to be condensed tar) were also observed. These qualitative observations are important for descriptions of soot radiation from coal flames.