Kramer, SK
1993
Ignition, Explosion, and Flame Propagation Characteristics of a Low-Rank Coal
Kramer, S.K.
Ignition, Explosion, and Flame Propagation Characteristics of a Low-Rank Coal, Ph.D./BYU, April 1993. Advisor: Smoot
1991
Coherent Anti-Stokes Raman Spectroscopy (CARS) Measurements in Coal-Seeded Flames
Hancock, R.D.; Hedman, P.O. and Kramer, S.K.
Combustion and Flame, 87:77-88, 1991. Funded by ACERC.
Coherent anti-Stokes Raman spectroscopy (CARS) is a laser diagnostic technique that can be used to determine temperature and major species concentrations in harsh combustion environments. CARS has been successfully applied to clean gas flames, but much less attention has been given to particle-laden flames like those encountered in industrial coal burners. Typically, experimental CARS spectra are obtained from a flame and then compared with theoretical CARS spectra to determine temperature and species concentration information. This information is more difficult to acquire in coal flames due to background and nonresonant interferences. These interferences alter the shape and intensity of the CARS signal, thus making analysis with unmodified version of standard CARS fitting codes impractical. Nitrogen temperature measurements were obtained in heavily coal-seeded natural gas/air flames. Two different coals and several coal feed rates and stoichiometries were investigated in order to determine possible limits associated with making CARS measurements in coal flames. Carbon monoxide signals were observed in some of the fuel-rich coal-seed flames but the signals were weak and of poor quality, therefore, quantitative results are not reported. Temperature measurements were obtained with nonresonant background levels caused by particle-induced breakdown as high as 100% of the peak N2 resonant signal. CARS N2 temperatures generally agreed with equilibrium code calculations.
1989
Coherent Anti-Stokes Raman Spectroscopy (CARS) Temperature and Species Concentration Measurements in Coal-Seeded Flames
Hancock, R.D.; Hedman, P.O. and Kramer, S.K.
AIChE Annual Meeting, San Francisco, California, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates).
Coherent anti-Stokes Raman Spectroscopy (CARS) is a laser diagnostic technique that can be used to determine temperature and major species concentrations in harsh combustion environments. CARS has been applied to clean gas flames with great success, but very little research has been conducted in particle-laden flames like those encountered in industrial coal burners. Typically, experimental CARS spectra are obtained from a flame and then compared to theoretical CARS spectra to determine temperature and species concentration information. This information is more difficult to acquire in coal flames due to the increased luminosity and enhanced background caused by particle and gas breakdown. The increased luminosity and breakdown alter the shape and intensity of the CARS signal, thus making analysis with unmodified versions of standard CARS fitting codes more complex.
CARS temperature and CO concentration measurements were obtained in heavily coal-seeded natural gas/air flames. Two different coals and several coal feed rates and stoichiometries were investigated in order to determine possible limits associated with making CARS measurements in coal flames. Temperature measurements were obtained with nonresonant background levels caused by particle-induced breakdown as high as 100% of the peak N2 resonant signal. CO concentration measurements deduced from the CO CARS spectra were less precise due to the difficulties of interpreting the CO CARS spectra in the presence of the enhanced background. Results generally agreed with thermochemical equilibrium combustion code calculations.
Measurement and Interpretation of Explosion Bomb Tests for Low Rank Coal
Cannon, J.N.; Kramer, S.K.; Smoot, L.D. and Dahn, C.J.
Western States Section, The Combustion Institute, Pullman, Washington, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates) and US Department of Energy.
Twenty-liter bomb tests have become a common method to evaluate safety implications involving pulverized coal (p.c.) in coalmines, coal power plant pulverizers and other equipment. However, only limited data are available for low rank coals. Further, some published bomb test results show more variation than is acceptable to many researchers which clouds credibility of the data. Often, significant variables are not controlled or reported adequately. The objective of this paper is to provide new data for low rank coals and illuminate the variables and effects that are significant.
Subbituminous coal from the Decker, Montana open pit mine was obtained from the mine face and immediately sealed in double-wall, plastic bags under nitrogen. Fifteen sets of 20-liter bomb tests with this coal were conducted to determine the effects of particle size, moisture, oxidation age and dust concentration on explosion characteristics. Mean particle size ranged from 3 to 50 mm; moisture ranged from 3 to 21%; low temperature oxidation age varied from mine-face fresh to 10 days. Dust concentrations ranged from 0.025 to 0.875 gm/liter. The test samples were obtained, stored, ground, classified and analyzed at this laboratory. The bomb tests were conducted by Safety Consulting Engineers Inc., of Chicago and included 20-liter bomb pressure-time traces. Maximum pressure varied between 95 and 135 psi and maximum pressure rise rate ranged from 2000 to 7000 psi/sec. The influence of coal sample storage length was examined through duplicate tests. Multivariate statistical regressions are used to extract information from the noted tests, clarifying the estimates of error for the data. Concentration and particle size have greater influence than moisture while oxidation age has very little influence.
The transient combustion processes during bomb tests are identified and the effects of the test variables are interpreted in light of these processes. Burning velocities are also estimated from various available theories and compared. Analytical methods show that the maximum pressure in the bomb is related to fuel concentration, fuel heating value and molecular weight of the product gases. Experimental results indicate that convective and radiant heat losses to the container wall and incomplete combustion significantly lower maximum pressure compared to predictions. In addition, initial turbulence in the bomb prior to ignition has a significant influence on observations. Requirements for controlling these variables in order to obtain consistent and repeatable test data from standard bomb tests are noted. The implication of the laboratory test results to full-scale explosions is also noted.
1988
Explosion Limits and Flame Speed For a Low-Rank Coal
Kramer, S.K.; Cannon, J.N. and Smoot, L.D.
Western States Section, 1988, The Combustion Institute, Salt lake City, UT. 16 pgs. Funded by US Department of Energy, Morgantown Energy Technology Center and Brigham Young University.
Explosion limits and flame propagation rates for a low-rank coal have been determined in an explosion bomb and are being studied in a steady flame device. The Decker, Montana subbituminous coal was obtained at the mine and stored in a nitrogen atmosphere. Minimum ignition energy and minimum dust cloud auto-ignition temperature were significantly influenced by sample moisture and particle size. However, the minimum explosive concentration, which was less than half that of the reference Pittsburgh bituminous coal dust, was not strongly affected by size or moisture content. Maximum pressure rise rate increased over three times with decreasing particle size and moisture content while the maximum pressure rise varied by only 20%. Ageing of the coal through low temperature surface oxidation of the sample had little effect on any of the ignition or explosion parameters. When compared to the reference Pittsburgh bituminous coal dust through the use of standard explosion indices, the dry coal is much more explosive while the wet coal is roughly equivalent. A well-insulated, one-dimensional, steady flow facility has been designed and constructed to measure the premixed, laminar flame speed of the sample coal. Preliminary tests have been made with a methane-supported coal dust flame to demonstrate in-situ measurement of species, species concentration and temperature with the coherent anti-Stokes Raman spectroscopy (CARS) system.
Kramer, SK
1993
Ignition, Explosion, and Flame Propagation Characteristics of a Low-Rank Coal
Kramer, S.K.
Ignition, Explosion, and Flame Propagation Characteristics of a Low-Rank Coal, Ph.D./BYU, April 1993. Advisor: Smoot
1991
Coherent Anti-Stokes Raman Spectroscopy (CARS) Measurements in Coal-Seeded Flames
Hancock, R.D.; Hedman, P.O. and Kramer, S.K.
Combustion and Flame, 87:77-88, 1991. Funded by ACERC.
Coherent anti-Stokes Raman spectroscopy (CARS) is a laser diagnostic technique that can be used to determine temperature and major species concentrations in harsh combustion environments. CARS has been successfully applied to clean gas flames, but much less attention has been given to particle-laden flames like those encountered in industrial coal burners. Typically, experimental CARS spectra are obtained from a flame and then compared with theoretical CARS spectra to determine temperature and species concentration information. This information is more difficult to acquire in coal flames due to background and nonresonant interferences. These interferences alter the shape and intensity of the CARS signal, thus making analysis with unmodified version of standard CARS fitting codes impractical. Nitrogen temperature measurements were obtained in heavily coal-seeded natural gas/air flames. Two different coals and several coal feed rates and stoichiometries were investigated in order to determine possible limits associated with making CARS measurements in coal flames. Carbon monoxide signals were observed in some of the fuel-rich coal-seed flames but the signals were weak and of poor quality, therefore, quantitative results are not reported. Temperature measurements were obtained with nonresonant background levels caused by particle-induced breakdown as high as 100% of the peak N2 resonant signal. CARS N2 temperatures generally agreed with equilibrium code calculations.
1989
Coherent Anti-Stokes Raman Spectroscopy (CARS) Temperature and Species Concentration Measurements in Coal-Seeded Flames
Hancock, R.D.; Hedman, P.O. and Kramer, S.K.
AIChE Annual Meeting, San Francisco, California, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates).
Coherent anti-Stokes Raman Spectroscopy (CARS) is a laser diagnostic technique that can be used to determine temperature and major species concentrations in harsh combustion environments. CARS has been applied to clean gas flames with great success, but very little research has been conducted in particle-laden flames like those encountered in industrial coal burners. Typically, experimental CARS spectra are obtained from a flame and then compared to theoretical CARS spectra to determine temperature and species concentration information. This information is more difficult to acquire in coal flames due to the increased luminosity and enhanced background caused by particle and gas breakdown. The increased luminosity and breakdown alter the shape and intensity of the CARS signal, thus making analysis with unmodified versions of standard CARS fitting codes more complex.
CARS temperature and CO concentration measurements were obtained in heavily coal-seeded natural gas/air flames. Two different coals and several coal feed rates and stoichiometries were investigated in order to determine possible limits associated with making CARS measurements in coal flames. Temperature measurements were obtained with nonresonant background levels caused by particle-induced breakdown as high as 100% of the peak N2 resonant signal. CO concentration measurements deduced from the CO CARS spectra were less precise due to the difficulties of interpreting the CO CARS spectra in the presence of the enhanced background. Results generally agreed with thermochemical equilibrium combustion code calculations.
Measurement and Interpretation of Explosion Bomb Tests for Low Rank Coal
Cannon, J.N.; Kramer, S.K.; Smoot, L.D. and Dahn, C.J.
Western States Section, The Combustion Institute, Pullman, Washington, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates) and US Department of Energy.
Twenty-liter bomb tests have become a common method to evaluate safety implications involving pulverized coal (p.c.) in coalmines, coal power plant pulverizers and other equipment. However, only limited data are available for low rank coals. Further, some published bomb test results show more variation than is acceptable to many researchers which clouds credibility of the data. Often, significant variables are not controlled or reported adequately. The objective of this paper is to provide new data for low rank coals and illuminate the variables and effects that are significant.
Subbituminous coal from the Decker, Montana open pit mine was obtained from the mine face and immediately sealed in double-wall, plastic bags under nitrogen. Fifteen sets of 20-liter bomb tests with this coal were conducted to determine the effects of particle size, moisture, oxidation age and dust concentration on explosion characteristics. Mean particle size ranged from 3 to 50 mm; moisture ranged from 3 to 21%; low temperature oxidation age varied from mine-face fresh to 10 days. Dust concentrations ranged from 0.025 to 0.875 gm/liter. The test samples were obtained, stored, ground, classified and analyzed at this laboratory. The bomb tests were conducted by Safety Consulting Engineers Inc., of Chicago and included 20-liter bomb pressure-time traces. Maximum pressure varied between 95 and 135 psi and maximum pressure rise rate ranged from 2000 to 7000 psi/sec. The influence of coal sample storage length was examined through duplicate tests. Multivariate statistical regressions are used to extract information from the noted tests, clarifying the estimates of error for the data. Concentration and particle size have greater influence than moisture while oxidation age has very little influence.
The transient combustion processes during bomb tests are identified and the effects of the test variables are interpreted in light of these processes. Burning velocities are also estimated from various available theories and compared. Analytical methods show that the maximum pressure in the bomb is related to fuel concentration, fuel heating value and molecular weight of the product gases. Experimental results indicate that convective and radiant heat losses to the container wall and incomplete combustion significantly lower maximum pressure compared to predictions. In addition, initial turbulence in the bomb prior to ignition has a significant influence on observations. Requirements for controlling these variables in order to obtain consistent and repeatable test data from standard bomb tests are noted. The implication of the laboratory test results to full-scale explosions is also noted.
1988
Explosion Limits and Flame Speed For a Low-Rank Coal
Kramer, S.K.; Cannon, J.N. and Smoot, L.D.
Western States Section, 1988, The Combustion Institute, Salt lake City, UT. 16 pgs. Funded by US Department of Energy, Morgantown Energy Technology Center and Brigham Young University.
Explosion limits and flame propagation rates for a low-rank coal have been determined in an explosion bomb and are being studied in a steady flame device. The Decker, Montana subbituminous coal was obtained at the mine and stored in a nitrogen atmosphere. Minimum ignition energy and minimum dust cloud auto-ignition temperature were significantly influenced by sample moisture and particle size. However, the minimum explosive concentration, which was less than half that of the reference Pittsburgh bituminous coal dust, was not strongly affected by size or moisture content. Maximum pressure rise rate increased over three times with decreasing particle size and moisture content while the maximum pressure rise varied by only 20%. Ageing of the coal through low temperature surface oxidation of the sample had little effect on any of the ignition or explosion parameters. When compared to the reference Pittsburgh bituminous coal dust through the use of standard explosion indices, the dry coal is much more explosive while the wet coal is roughly equivalent. A well-insulated, one-dimensional, steady flow facility has been designed and constructed to measure the premixed, laminar flame speed of the sample coal. Preliminary tests have been made with a methane-supported coal dust flame to demonstrate in-situ measurement of species, species concentration and temperature with the coherent anti-Stokes Raman spectroscopy (CARS) system.