McCollor, DP
1994
Transformation of Trace Metals in Coal Gasification
Zygarlicke, C.J.; McCollor, D.P. and Benson, S.A.
Proceedings of the Pacific Rim International Conference on Environmental Control of Combustion Processes, Maui, HI, August 1994. Funded by US Environmental Protection Agency, US Department of Energy/Morgantown Energy Technology Center and Brigham Young University.
Trace metals pose a potential problem to emerging coal gasification electric power-generating systems. Some of the trace metals in coal are considered air toxics when released into the atmosphere and can also cause the degradation of fuel cell efficiency due to contamination. The fate of trace metals during coal conversion in integrated gasification combined cycle and integrated gasification fuel cell systems is closely tied to how the trace metals are associated in the coal and gasification conditions. Bench-scale gasification experiments were performed using Illinois No. 6 coal to determine the partitioning of Hg, Se, As, Ni, Cd, Pb, and Cr into gas, liquid, and solid phases as a function of gasification conditions and coal composition. Entrained ash was generated in a pressurized drop-tube furnace and collected using a multicyclone and impinger sampling train. Coal analysis revealed arsenic, Hg, Ni, Pb, and Se to be primarily associated with pyrite. Cr was associated primarily with clay minerals, and Cd appeared to have either a sulfide or an organic association. Cr, Pb, and Ni are enriched in the ash particulate fraction (collected in multicyclones), while Cd, As, Se, and Hg are depleted in the particulate and are more enriched in the very fine particulate or vapor-phase fraction (collected in the final filter and impingers). Oxygen contents were varied to represent both combustion and gasification systems. Most of the work was conducted at lower oxygen/carbon (O/C) ratios. Lower O/C ratios resulted in more Hg being driven to the vapor phase. Under the constant O/C ratios, Hg, Se, and Cd showed increasing volatility with increasing temperature in the reaction zone.
A Laboratory-Scale Method to Assess Ash Deposit Removability
McCollor, D.P.; Zygarlicke, C.J.; Toman, D.L. and Evenstad, D.N.
The Impact of Ash Deposition on Coal/Fired Plants, Taylor & Francis, Inc., 1994. Funded by Brigham Young University and US Department of Energy.
A bench-scale method has been developed to measure in situ the force required to remove coal ash deposits grown under simulated fouling conditions. A suite of eight coals, representing a range of rank and known fouling behavior, were examined using this method. Statistical analysis of the data resulted in a good correlation of adhesion strength with an independently derived index of high-temperature fouling propensity and with 1(coal feed time), number of soot blowings, and number of noneffective soot blowings. Using this method, a coal or coal blend can be rapidly screened for fouling behavior under conditions simulating those attained in a particular utility boiler.
1993
Ash Deposit Initiation in a Simulated Fouling Regime
McCollor, D.P.; Zygarlicke, C.J.; Allan, S.E. and Benson, S.A.
Energy & Fuels, 7 (6):761-767, 1993. (Also presented at the Seventh Annual Technical conference of the Advanced Combustion Engineering Center, Park City, UT, March 1993. Funded by US Department of Energy and ACERC.
Bench-scale pulverized coal combustion studies were performed to examine selected major factors that influence deposit initiation. Five coals of varying ranked and composition, including a Beulah-Zap lignite, a Dietz subbituminous coal, a Utah Blind Canyon western bituminous coal, and Illinois No. 6 and Pittsburgh No. 8 eastern bituminous coals, were fired in a laminar flow drop-tube furnace under simulated fouling conditions. Initially deposited particles as well as bulk fly ash were examined using scanning electron microscopy techniques. Deposited particle diameters ranged from 10 to 40 µm. Initial adhering particles were primarily iron-, iron-calcium-and iron-silica-aluminum-rich particles for the Pittsburgh No. 8, Illinois No. 6, Utah Blind Canyon, and Beulah coals. Utah Blind Canyon and Beulah deposits also included some calcium-silica-alumina-rich particles. Dietz deposits contained iron-and iron-calcium-rich particles, along with substantial barium- and barium-sulfate-rich species. These enriched particle species appeared common to all of the initial deposits, with their abundance being determined by the concentration in the original coals. The great majority of the initially deposited particles clustered in similar groupings above a certain "critical" mass and below a "critical" viscosity regardless of individual compositions. This indicates that the initial deposit particles are those with sufficient kinetic energy to impact the substrate inertially and with sufficiently low viscosity to adhere upon impaction. The propensity for initial ash deposition can be roughly related to the fraction of particles in the bulk fly ash possessing these mass and viscosity requirements.
A Laboratory-Scale Method to Assess Ash Deposit Removability
McCollor, D.P.; Zygarlicke, C.J.; Toman, D.L. and Evenstad, D.N.
Proceedings from the Impact of Ash Deposition on Coal Fired Plant Engineering Foundation Conference, Solihull, UK, June 1993. Funded by US Department of Energy and Electric Power Research Institute.
A bench-scale method has been developed to measure in situ the force required to remove coal ash deposits grown under simulated fouling conditions. A suite of eight coals, representing a range of rank and known fouling behavior, were examined using this method. Statistical analysis of the data resulted in a good correlation of adhesion strength with an independently derived index of high-temperature fouling propensity and with 1(coal feed time), number of soot blowings, and number of noneffective soot blowings. Using this method, a coal or coal blend can be rapidly screened for fouling behavior under conditions simulating those attained in a particular utility boiler.
1992
Inorganic Transformation During Combustion
Benson, S.A.; Zygarlicke, C.J. and McCollor, D.P.
Eighth Annual Coal Preparation, Utilization, and Environmental Control Contractors Conference, Pittsburgh, PA, July 1992. Funded by US Department of Energy and Morgantown Energy Technology Center.
The overall objective of this project is to develop a unified picture of the physical and chemical changes that occur in coal inorganic matter during combustion. Information obtained from studying the mechanisms of inorganic transformations will be used to predict the size and composition of ash particles based on coal composition and combustion conditions.
Ash Particle Size and Composition Evolution During Combustion of Synthetic Coal and Inorganic Mixtures
Zygarlicke, C.J.; McCollor, D.P.; Benson, S.A. and Holm, P.L.
Twenty-Fourth Symposium (International) on Combustion, The Combustion Institute, Sydney, Australia, July 1992. Funded by US Department of Energy, Energy & Environmental Research Center and ACERC.
Synthetic coal model mixtures were used to determine the chemical and physical transformation mechanisms involved in the evolution of fly ash during combustion. Two calcium, silica, and sulfur synthetic coal systems were prepared: on system containing calcium as 10-µm calcite (Ca[min.]-Si-S), and the other containing calcium as ionically dispersed calcium acetate (Ca[org.]-Si-S). A third system consisted of sodium, silica, and sulfur with the sodium associated as sodium benzoate (Na[org.]-Si-S). Silica, in all three systems, consisted of a furfuyl alsohol/p-toluensulfonic polymer. The synthetic coal mixtures, each sized to 38-106 µm, were combusted in a bench-scale drop-tube furnace at gas temperatures of 900º, 1100º, 1300º, and 1500ºC and residence times of approximately two seconds. Fly ash produced from the Ca(min.)-Si-S mixture revealed significant interaction between the calcite and quartz at higher temperature, as evidenced by increases in particle size and in the levels of amorphous calcium silicate with increasing temperature. Temperatures were high enough to decompose calcite to calcium hydroxide and calcium oxide, which in turn reacted with sulfur o quartz. During the combustion of the Ca(org.)-Si-S mixture, the organically associated calcium reacted primarily with the surface of quartz grains at all temperatures. For both Ca-Si-S systems, calcium reacted with sulfur to form anhydrite at temperatures at or lower than 1300ºC. The Na(org.)-Si-S system revealed extensive melting, mineral particle coalescence, and formation of sodium sulfate at 900ºC; however, at 1500ºC, the fly ash contained only minuscule amounts of sodium or sodium-bearing phases and showed evidence for either char fragmentation or noncoalescence due to the absence of sodium sulfates and silicates.
1988
Temperature Measurements of Beulah Lignite Char in a Novel Laminar-Flow Reactor
Young, B.C.; McCollor, D.P.; Weber, B.J. and Jones, M.L.
Fuel, 67, 1988, 5 pgs. Funded by US Department of Energy and Pittsburgh Energy Technology Center.
A novel laminar-flow flameless reactor has been designed and constructed for investigating the combustion behavior of individual coal particles, incorporating a three-color optical pyrometer for measuring single-particle temperatures. Results for the combustion of Beulah (North Dakota) lignite char at sizes below 200 mm and at gas temperatures between 760K and 1270K are presented. It was found that the particle temperature in all cases studied exceeded the local gas temperature by several hundred degrees. The burning rates were controlled by the mass diffusion of oxygen, and the mean particle temperature was linearly dependent on oxygen mole fraction in the gas phase over the range 0.05 to 0.16. The particle temperature also showed an inverse relationship with particle size.
Promotion of Char Oxidation by Inorganic Constituents
McCollor, D.P.; Young, B.C.; Jones, M.L. and Benson, S.A.
Accept for publication in the Twenty-Second International Symposium on Combustion, 1988. Funded by US Department of Energy and Pittsburgh Energy Technology Center.
A North Dakota lignite has been demineralized and selectively reloaded with calcium, potassium, and sodium cations by an ion-exchange process. Chars produced from the treated samples were burned in a laminar-flow reactor and single-particle temperatures were determined by optical pyrometry. Results show that sodium and potassium cations present in the chars have little effect on the char particle temperatures at low concentration (<5000 ppm). The results are consistent with carbon dioxide being produced at the char surface by catalytic action of the char mineral matter.
McCollor, DP
1994
Transformation of Trace Metals in Coal Gasification
Zygarlicke, C.J.; McCollor, D.P. and Benson, S.A.
Proceedings of the Pacific Rim International Conference on Environmental Control of Combustion Processes, Maui, HI, August 1994. Funded by US Environmental Protection Agency, US Department of Energy/Morgantown Energy Technology Center and Brigham Young University.
Trace metals pose a potential problem to emerging coal gasification electric power-generating systems. Some of the trace metals in coal are considered air toxics when released into the atmosphere and can also cause the degradation of fuel cell efficiency due to contamination. The fate of trace metals during coal conversion in integrated gasification combined cycle and integrated gasification fuel cell systems is closely tied to how the trace metals are associated in the coal and gasification conditions. Bench-scale gasification experiments were performed using Illinois No. 6 coal to determine the partitioning of Hg, Se, As, Ni, Cd, Pb, and Cr into gas, liquid, and solid phases as a function of gasification conditions and coal composition. Entrained ash was generated in a pressurized drop-tube furnace and collected using a multicyclone and impinger sampling train. Coal analysis revealed arsenic, Hg, Ni, Pb, and Se to be primarily associated with pyrite. Cr was associated primarily with clay minerals, and Cd appeared to have either a sulfide or an organic association. Cr, Pb, and Ni are enriched in the ash particulate fraction (collected in multicyclones), while Cd, As, Se, and Hg are depleted in the particulate and are more enriched in the very fine particulate or vapor-phase fraction (collected in the final filter and impingers). Oxygen contents were varied to represent both combustion and gasification systems. Most of the work was conducted at lower oxygen/carbon (O/C) ratios. Lower O/C ratios resulted in more Hg being driven to the vapor phase. Under the constant O/C ratios, Hg, Se, and Cd showed increasing volatility with increasing temperature in the reaction zone.
A Laboratory-Scale Method to Assess Ash Deposit Removability
McCollor, D.P.; Zygarlicke, C.J.; Toman, D.L. and Evenstad, D.N.
The Impact of Ash Deposition on Coal/Fired Plants, Taylor & Francis, Inc., 1994. Funded by Brigham Young University and US Department of Energy.
A bench-scale method has been developed to measure in situ the force required to remove coal ash deposits grown under simulated fouling conditions. A suite of eight coals, representing a range of rank and known fouling behavior, were examined using this method. Statistical analysis of the data resulted in a good correlation of adhesion strength with an independently derived index of high-temperature fouling propensity and with 1(coal feed time), number of soot blowings, and number of noneffective soot blowings. Using this method, a coal or coal blend can be rapidly screened for fouling behavior under conditions simulating those attained in a particular utility boiler.
1993
Ash Deposit Initiation in a Simulated Fouling Regime
McCollor, D.P.; Zygarlicke, C.J.; Allan, S.E. and Benson, S.A.
Energy & Fuels, 7 (6):761-767, 1993. (Also presented at the Seventh Annual Technical conference of the Advanced Combustion Engineering Center, Park City, UT, March 1993. Funded by US Department of Energy and ACERC.
Bench-scale pulverized coal combustion studies were performed to examine selected major factors that influence deposit initiation. Five coals of varying ranked and composition, including a Beulah-Zap lignite, a Dietz subbituminous coal, a Utah Blind Canyon western bituminous coal, and Illinois No. 6 and Pittsburgh No. 8 eastern bituminous coals, were fired in a laminar flow drop-tube furnace under simulated fouling conditions. Initially deposited particles as well as bulk fly ash were examined using scanning electron microscopy techniques. Deposited particle diameters ranged from 10 to 40 µm. Initial adhering particles were primarily iron-, iron-calcium-and iron-silica-aluminum-rich particles for the Pittsburgh No. 8, Illinois No. 6, Utah Blind Canyon, and Beulah coals. Utah Blind Canyon and Beulah deposits also included some calcium-silica-alumina-rich particles. Dietz deposits contained iron-and iron-calcium-rich particles, along with substantial barium- and barium-sulfate-rich species. These enriched particle species appeared common to all of the initial deposits, with their abundance being determined by the concentration in the original coals. The great majority of the initially deposited particles clustered in similar groupings above a certain "critical" mass and below a "critical" viscosity regardless of individual compositions. This indicates that the initial deposit particles are those with sufficient kinetic energy to impact the substrate inertially and with sufficiently low viscosity to adhere upon impaction. The propensity for initial ash deposition can be roughly related to the fraction of particles in the bulk fly ash possessing these mass and viscosity requirements.
A Laboratory-Scale Method to Assess Ash Deposit Removability
McCollor, D.P.; Zygarlicke, C.J.; Toman, D.L. and Evenstad, D.N.
Proceedings from the Impact of Ash Deposition on Coal Fired Plant Engineering Foundation Conference, Solihull, UK, June 1993. Funded by US Department of Energy and Electric Power Research Institute.
A bench-scale method has been developed to measure in situ the force required to remove coal ash deposits grown under simulated fouling conditions. A suite of eight coals, representing a range of rank and known fouling behavior, were examined using this method. Statistical analysis of the data resulted in a good correlation of adhesion strength with an independently derived index of high-temperature fouling propensity and with 1(coal feed time), number of soot blowings, and number of noneffective soot blowings. Using this method, a coal or coal blend can be rapidly screened for fouling behavior under conditions simulating those attained in a particular utility boiler.
1992
Inorganic Transformation During Combustion
Benson, S.A.; Zygarlicke, C.J. and McCollor, D.P.
Eighth Annual Coal Preparation, Utilization, and Environmental Control Contractors Conference, Pittsburgh, PA, July 1992. Funded by US Department of Energy and Morgantown Energy Technology Center.
The overall objective of this project is to develop a unified picture of the physical and chemical changes that occur in coal inorganic matter during combustion. Information obtained from studying the mechanisms of inorganic transformations will be used to predict the size and composition of ash particles based on coal composition and combustion conditions.
Ash Particle Size and Composition Evolution During Combustion of Synthetic Coal and Inorganic Mixtures
Zygarlicke, C.J.; McCollor, D.P.; Benson, S.A. and Holm, P.L.
Twenty-Fourth Symposium (International) on Combustion, The Combustion Institute, Sydney, Australia, July 1992. Funded by US Department of Energy, Energy & Environmental Research Center and ACERC.
Synthetic coal model mixtures were used to determine the chemical and physical transformation mechanisms involved in the evolution of fly ash during combustion. Two calcium, silica, and sulfur synthetic coal systems were prepared: on system containing calcium as 10-µm calcite (Ca[min.]-Si-S), and the other containing calcium as ionically dispersed calcium acetate (Ca[org.]-Si-S). A third system consisted of sodium, silica, and sulfur with the sodium associated as sodium benzoate (Na[org.]-Si-S). Silica, in all three systems, consisted of a furfuyl alsohol/p-toluensulfonic polymer. The synthetic coal mixtures, each sized to 38-106 µm, were combusted in a bench-scale drop-tube furnace at gas temperatures of 900º, 1100º, 1300º, and 1500ºC and residence times of approximately two seconds. Fly ash produced from the Ca(min.)-Si-S mixture revealed significant interaction between the calcite and quartz at higher temperature, as evidenced by increases in particle size and in the levels of amorphous calcium silicate with increasing temperature. Temperatures were high enough to decompose calcite to calcium hydroxide and calcium oxide, which in turn reacted with sulfur o quartz. During the combustion of the Ca(org.)-Si-S mixture, the organically associated calcium reacted primarily with the surface of quartz grains at all temperatures. For both Ca-Si-S systems, calcium reacted with sulfur to form anhydrite at temperatures at or lower than 1300ºC. The Na(org.)-Si-S system revealed extensive melting, mineral particle coalescence, and formation of sodium sulfate at 900ºC; however, at 1500ºC, the fly ash contained only minuscule amounts of sodium or sodium-bearing phases and showed evidence for either char fragmentation or noncoalescence due to the absence of sodium sulfates and silicates.
1988
Temperature Measurements of Beulah Lignite Char in a Novel Laminar-Flow Reactor
Young, B.C.; McCollor, D.P.; Weber, B.J. and Jones, M.L.
Fuel, 67, 1988, 5 pgs. Funded by US Department of Energy and Pittsburgh Energy Technology Center.
A novel laminar-flow flameless reactor has been designed and constructed for investigating the combustion behavior of individual coal particles, incorporating a three-color optical pyrometer for measuring single-particle temperatures. Results for the combustion of Beulah (North Dakota) lignite char at sizes below 200 mm and at gas temperatures between 760K and 1270K are presented. It was found that the particle temperature in all cases studied exceeded the local gas temperature by several hundred degrees. The burning rates were controlled by the mass diffusion of oxygen, and the mean particle temperature was linearly dependent on oxygen mole fraction in the gas phase over the range 0.05 to 0.16. The particle temperature also showed an inverse relationship with particle size.
Promotion of Char Oxidation by Inorganic Constituents
McCollor, D.P.; Young, B.C.; Jones, M.L. and Benson, S.A.
Accept for publication in the Twenty-Second International Symposium on Combustion, 1988. Funded by US Department of Energy and Pittsburgh Energy Technology Center.
A North Dakota lignite has been demineralized and selectively reloaded with calcium, potassium, and sodium cations by an ion-exchange process. Chars produced from the treated samples were burned in a laminar-flow reactor and single-particle temperatures were determined by optical pyrometry. Results show that sodium and potassium cations present in the chars have little effect on the char particle temperatures at low concentration (<5000 ppm). The results are consistent with carbon dioxide being produced at the char surface by catalytic action of the char mineral matter.