Boardman, RD
1996
A Computational Method for Determining Global Fuel-NO Rate Expressions.
Part 1
Chen, W.; Smoot, L.D.; Fletcher, T.H. and Boardman, R.D.
Energy & Fuels, 10(5):1036-1045, 1996. Funded by ACERC.
Global chemical reaction rates used in the modeling of NOx formation in comprehensive combustion codes have traditionally been obtained trough correlation of experimental data. In this paper, a computational approach for obtaining global rates is presented. Several premixed flames were simulated, and sensitivity analysis of species concentration profiles was used to suggest global pathways in fuel-nitrogen conversion to NO. Based on these analyses, the global reaction rates were formulated. The predicted species concentration profiles and their derivatives were then used in the determination of the global rate constants. The correlation of rate constants for the two fuel-NO global rates (HCN + NO N2 + . . . and HCN + O2 NO + . . .) are discussed. Comparisons of the computed global rate constants with those rate constants with those deduced from experimental data show good agreement. The global rates provide practical kinetics for simulating nitrogen pollutant chemistry in complex flames.
1993
Pollutant Formation and Control
Boardman, R.D. and Smoot, L.D.
Chapter 6, Fundamentals of Coal Combustion: For Clean and Efficient Use, (L.D. Smoot, ed.), Elsevier Science Publishers, The Netherlands, 1993. Funded by ACERC.
By far the most striking problem associated with human consumption of fossil fuels is the control of air pollutants. The inexorable trend for increasing power demand, both by industrially established countries and developing nations, will inevitably lead to increased production and utilization of fossil fuels. The combustion of fossil fuels produces both primary and secondary pollutants. Primary pollutants include all species in the combustor exhaust gases that are considered contaminants to the environment. The major primary pollutants include CO, hydrocarbons, sulfur-containing compounds, nitrogen oxides, particulate materials, various trace metals, and even CO2 that reached pollutant status with increasing concern for global atmospheric warming or the "greenhouse" effect. Secondary pollutants are defined as environmentally detrimental species that are formed in the atmosphere as a consequence of precursor combustion emissions. The list of secondary pollutants includes particulate matter and aerosols that accumulate in the size range of 0.1-10 µm diameter, NO2, O3, and other photochemical oxidants, and acid vapors. The connection between combustion-generated pollutants and airborne toxins, acid rain, visibility degradation, the greenhouse effect, and stratospheric ozone depletion is well established. The detrimental impact of these contaminants on ecosystems in the biosphere and stratosphere has been the impetus of stricter standards around the world. This chapter emphasizes the formation and control of nitrogen oxides (referred to as NOx pollutants) and sulfur-containing pollutants (referred to as SO pollutants) in which temperature stationary combustors. The focus is on the formation of nitrogen oxides since they can be effectively controlled in the combustion chamber. An understanding of nitrogen chemistry and furnace fluid dynamics is imperative to optimizing in-situ nitrogen oxide control schemes. A brief review on the development of mathematical tools used to predict nitrogen and sulfur oxide formation during combustion of fossil fuels will also be presented, In addition, an overview and comparison of NOx and sulfur pollutant abatement strategies is given.
Development and Application of an Acid Rain Precursor Model for Practical Furnaces
Smoot, L.D.; Boardman, R.D.; Brewster, B.S.; Hill, S.C. and Foli, A.K.
Energy & Fuels, 7 (6):786-795, 1993. Funded by ACERC.
Control of emissions of sulfur (SO2, SO3, H2S) and nitrogen (NO, NO2, N2O, HCN, NH3) pollutants from fossil-fuel-fired furnaces and gasifiers remains a vital worldwide requirement as the utilization of fossil fuels continues to increase. Development and refinement of a predictive model for these acid rain precursors (MARP) has reached the point where this technology can contribute to acid rain control. In this paper, model foundations and recent developments are summarized, including formation of thermal and fuel NOx and sorbent capture of sulfur oxides. The method includes global formation, capture, and destruction processes in turbulent, reacting, particle-laden flows. This submodel has been combined with comprehensive, generalized combustion models (PCGC-2, PCGC-3) that provide the required local properties for the combustion or gasification processes. The submodel has been applied to NOx formation in a full-scale (85 MWe), corner-fired utility boiler, where recent in situ NOx measurements were made, with variations in coal feedstock quality (including fuel N percentage) load-level and percentage excess air. Predictions are also made for in situ sorbent capture of sulfur pollutants in both combustion (fuel-lean, SO2), and gasification (fuel-rich, H2S) laboratory-scale reactors. Limitations of MARP are identified and work to improve the submodel is outlined.
Comparison of Measurements and Predictions of Flame Structure and Thermal NOx, in a Swirling, Natural Gas Diffusion Flame
Boardman, R.D.; Eatough, C.N.; Germane, G.J. and Smoot, L.D.
Combustion Science and Technology, 20: 1-18, 1993. (Previously presented at the First International Conference on Combustion Technologies For a Clean Environment, Vilamoura, Portugal, September 1991). Funded by Morgantown Energy Technology Center.
A combined thermal and fuel nitric oxide submodel has recently been added to a generalized, 2-dimensional pulverized coal gasification and combustion model (PCGC-2). This model is applicable to reacting and non-reacting gaseous and particle-laden flows. The thermal NO model is based on the extended Zel'dovich mechanism. To perform an evaluation of the NOx submodel, combustion measurements of gas velocities, temperatures, and species concentrations were made in a laboratory-scale, experimental reactor with a 150 kW natural gas flame at an equivalence ratio of 1.05 and a secondary-air swirl number of 1.5. Combustion measurements of velocities and major species concentrations show generally good agreement with predicted values. Gas temperature measurements closely match predictions in the recovery region but fail to show predicted high temperature in the annular region. This study provides an evaluation of a comprehensive combustion model and the NOx submodel that can be useful as a design tool to provide pollutant formation trends in applied systems as combustion parameters are varied.
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.
1992
Comparison of Measurements and Predictions of Flame Structure and Thermal NOx, in a Swirling, Natural Gas Diffusion Flame
Boardman, R.D.; Eatough, C.N.; Germane, G.J. and Smoot, L.D.
Combustion Science and Technology, 1992 (in press). (Previously presented at the First International Conference on Combustion Technologies For a Clean Environment, Vilamoura, Portugal, September 1991.) Funded by Morgantown Energy Technology Center through subcontract from Advanced Fuel Research and ACERC.
A combined thermal and fuel nitric oxide submodel has recently been added to a generalized, 2-dimensional pulverized coal gasification and combustion model (PCGC-2). This model is applicable to reacting and non-reacting gaseous and particle-laden flows. The thermal NO model is based on the extended Zel'dovich mechanism. To perform an evaluation of the NOx submodel, combustion measurements of gas velocities, temperatures, and species concentrations were made in a laboratory-scale, experimental reactor with a 150 kW natural gas flame at an equivalence ratio of 1.05 and a secondary-air swirl number of 1.5. Combustion measurements of velocities and major species concentrations show generally good agreement with predicted values. Gas temperature measurements closely match predictions in the recovery region but fail to show predicted high temperature in the annular region. This study provides an evaluation of a comprehensive combustion model and the NOx submodel that can be useful as a design tool to provide pollutant formation trends in applied systems as combustion parameters are varied.
Modeling Sorbent Injection and Sulfur Capture in Pulverized Coal Combustion
Boardman, R.D.; Brewster, B.S.; Huque, Z.; Smoot, L.D. and Silcox, G.D.
Air Toxic Reduction and Combustion Modeling, 15:1-9, 1992. (Also presented at the ASME International Joint Power Generation Conference, Atlanta, GA, October 1992). Funded by Advanced Fuel Research and ACERC.
A computer model has been developed for predicting mixing and reactions of injected sorbent particles in pulverized coal combustors and gasifiers. A shrinking-core, grain model was used for sulfation. The model accounts for the effects of surface area, pore diffusion, diffusion through the product layer, chemical reaction, and reduction of the pore volume due to grain swelling. The submodel was evaluated for a fuel-lean case and for a fuel-rich case. Predictions were compared with limited experimental data (for the fuel-rich case). The results illustrate the model's capability for predicting the effectiveness of sulfur capture. The importance of sorbent particle properties was also investigated parametrically, and model limitations were identified
1991
Comparison of Measurements and Predictions of Flame Structure and Thermal NOx, in a Swirling, Natural Gas Diffusion Flame
Boardman, R.D.; Eatough, C.N.; Germane, G.J. and Smoot, L.D.
First International Conference on Combustion Technologies For a Clean Environment, Vilamoura, Portugal, September 1991. Funded by Morgantown Energy Technology Center through subcontract from Advanced Fuel Research Co.
A combined thermal and fuel nitric oxide submodel has recently been added to a generalized, 2-dimensional pulverized coal gasification and combustion model (PCGC-2). This model is applicable to reacting and non-reacting gaseous and particle-laden flows. The thermal NO model is based on the extended Zel'dovich mechanism. To perform an evaluation of the NOx submodel, combustion measurements of gas velocities, temperatures, and species concentrations were made in a laboratory-scale, experimental reactor with a 150 kW natural gas flame at an equivalence ratio of 1.05 and a secondary-air swirl number of 1.5. Combustion measurements of velocities and major species concentrations show generally good agreement with predicted values. Gas temperature measurements closely match predictions in the recovery region but fail to show predicted high temperature in the annular region. This study provides an evaluation of a comprehensive combustion model and the NOx submodel that can be useful as a design tool to provide pollutant formation trends in applied systems as combustion parameters are varied.
1989
Measurement and Prediction of Thermal and Fuel NOx
Boardman, R.D.; Smoot, L.D. and Brewster, B.S.
Western States Section, The Combustion Institute, Livermore, California, 1989. Funded by US Department of Energy through subcontract from Advanced Fuel Research Co., and ACERC (National Science Foundation and Associates and Affiliates).
A generalized NOx model is being developed to predict nitric oxide formation in practical combustors. The NOx model incorporates an extended global fuel-NO mechanism and the modified Zeldovich mechanism to predict thermal NO formation. The importance of coupling turbulence with the chemical kinetics for practical combustors is addressed. Thermal NO data for a turbulent gaseous diffusion flame (in a laboratory-scale furnace) are presented. The model is being validated using these previously unpublished data and other pulverized-coal combustion and gasification data from the literature.
1987
Prediction of Nitric Oxide in Advanced Combustion Systems
Boardman, R.D. and Smoot, L.D.
AlChE J., 1987. 14 pgs. Funded by ACERC Consortium: Babcock & Wilcox, Combustion Engineering, Consol, Electric Power Research Institute, Empire State Electrical Energy Research Corp., Foster Wheeler, Pittsburgh Energy Technology Center, Tennessee Valley Authority, and Utah Power & Light.
A computer model to predict nitric oxide (NO) concentrations has been applied to advanced-concept, pulverized-coal systems and evaluated by comparing model predictions with experimental data. Specifically, the effects of pressure, stoichiometric ratio, coal moisture content, particle size, and swirling and non-swirling diffusion flames (Hill et al., 1984; Smith et al., 1986).
The NO model is a subcomponent of a general combustion code that provides theoretical predictions for the temperature, velocity, major species, and other properties at local points throughout turbulent, combusting flow fields (Smoot and Smith, 1985). In the NO model, fuel nitrogen release from the coal is assumed to occur at a rate proportional to total coal weight loss. The volatile nitrogen is assumed to be instantaneously converted to HCN. NO is formed by oxidation of the HCN and is competitively reduced to N2 by reaction with HCN. Global rate expressions for these reactions were measured by the Soete (1985). The model also accounts for the destruction of NO by heterogeneous interaction with char using a rate expression from Levy et al., (1981). All rate parameters are used as reported except for the information of HO. For this rate equation, the pre-exponential factor was increased by a factor of ten. This value is still in within the range of experimental error and was used because it yielded better results. Effects of turbulence on the gaseous reactions are accounted for through use of a joint probability calculation of fluctuating gaseous and coal off-gas mixture fractions. These two progress variables are sufficient to track turbulent temperature and gas concentration variations (Smith et al., 1982). Experimental data sources for model comparisons were selected for axi-symmetric combustion exponents that investigated the variation of key test variables (e.g., pressure or stoichiometric ratio).
Further Evaluation of a Nitric Oxide Model
Boardman, R.D. and Smoot, L.D.
Western States Section, 1987, The Combustion Institute, Provo, UT. 25 pgs. Funded by Morgantown Energy Technology Center through subcontract from Advanced Fuel Research Co.
Further verification of a predictive model for nitric oxide formation during turbulent combustion of coal containing fuels has been conducted. Computations for pulverized coal combustion in CO2-02 mixtures of various percents have been completed. The predicted NO concentrations compare favorably with experimental measurements. Simulations were also completed for entrained-flow gasification in a laboratory-scale combustor. Again, reasonable agreement is demonstrated by comparing laboratory NO maps to predicted NO concentrations. The effects of pressure on NO concentrations were reliably predicted. Calculations were also completed for air-staged combustion in a one-dimensional, laboratory-scale reactor. In general, the trend of decreasing primary zone stoichiometric ratio and variation in staging air location were correctly predicted. The simplified global mechanism expressions of the NO model appear to sufficiently account for the formation and competing destruction of NO in both fuel-lean and fuel-rich environments for different reactor systems and conditions.
Boardman, RD
1996
A Computational Method for Determining Global Fuel-NO Rate Expressions.
Part 1
Chen, W.; Smoot, L.D.; Fletcher, T.H. and Boardman, R.D.
Energy & Fuels, 10(5):1036-1045, 1996. Funded by ACERC.
Global chemical reaction rates used in the modeling of NOx formation in comprehensive combustion codes have traditionally been obtained trough correlation of experimental data. In this paper, a computational approach for obtaining global rates is presented. Several premixed flames were simulated, and sensitivity analysis of species concentration profiles was used to suggest global pathways in fuel-nitrogen conversion to NO. Based on these analyses, the global reaction rates were formulated. The predicted species concentration profiles and their derivatives were then used in the determination of the global rate constants. The correlation of rate constants for the two fuel-NO global rates (HCN + NO N2 + . . . and HCN + O2 NO + . . .) are discussed. Comparisons of the computed global rate constants with those rate constants with those deduced from experimental data show good agreement. The global rates provide practical kinetics for simulating nitrogen pollutant chemistry in complex flames.
1993
Pollutant Formation and Control
Boardman, R.D. and Smoot, L.D.
Chapter 6, Fundamentals of Coal Combustion: For Clean and Efficient Use, (L.D. Smoot, ed.), Elsevier Science Publishers, The Netherlands, 1993. Funded by ACERC.
By far the most striking problem associated with human consumption of fossil fuels is the control of air pollutants. The inexorable trend for increasing power demand, both by industrially established countries and developing nations, will inevitably lead to increased production and utilization of fossil fuels. The combustion of fossil fuels produces both primary and secondary pollutants. Primary pollutants include all species in the combustor exhaust gases that are considered contaminants to the environment. The major primary pollutants include CO, hydrocarbons, sulfur-containing compounds, nitrogen oxides, particulate materials, various trace metals, and even CO2 that reached pollutant status with increasing concern for global atmospheric warming or the "greenhouse" effect. Secondary pollutants are defined as environmentally detrimental species that are formed in the atmosphere as a consequence of precursor combustion emissions. The list of secondary pollutants includes particulate matter and aerosols that accumulate in the size range of 0.1-10 µm diameter, NO2, O3, and other photochemical oxidants, and acid vapors. The connection between combustion-generated pollutants and airborne toxins, acid rain, visibility degradation, the greenhouse effect, and stratospheric ozone depletion is well established. The detrimental impact of these contaminants on ecosystems in the biosphere and stratosphere has been the impetus of stricter standards around the world. This chapter emphasizes the formation and control of nitrogen oxides (referred to as NOx pollutants) and sulfur-containing pollutants (referred to as SO pollutants) in which temperature stationary combustors. The focus is on the formation of nitrogen oxides since they can be effectively controlled in the combustion chamber. An understanding of nitrogen chemistry and furnace fluid dynamics is imperative to optimizing in-situ nitrogen oxide control schemes. A brief review on the development of mathematical tools used to predict nitrogen and sulfur oxide formation during combustion of fossil fuels will also be presented, In addition, an overview and comparison of NOx and sulfur pollutant abatement strategies is given.
Development and Application of an Acid Rain Precursor Model for Practical Furnaces
Smoot, L.D.; Boardman, R.D.; Brewster, B.S.; Hill, S.C. and Foli, A.K.
Energy & Fuels, 7 (6):786-795, 1993. Funded by ACERC.
Control of emissions of sulfur (SO2, SO3, H2S) and nitrogen (NO, NO2, N2O, HCN, NH3) pollutants from fossil-fuel-fired furnaces and gasifiers remains a vital worldwide requirement as the utilization of fossil fuels continues to increase. Development and refinement of a predictive model for these acid rain precursors (MARP) has reached the point where this technology can contribute to acid rain control. In this paper, model foundations and recent developments are summarized, including formation of thermal and fuel NOx and sorbent capture of sulfur oxides. The method includes global formation, capture, and destruction processes in turbulent, reacting, particle-laden flows. This submodel has been combined with comprehensive, generalized combustion models (PCGC-2, PCGC-3) that provide the required local properties for the combustion or gasification processes. The submodel has been applied to NOx formation in a full-scale (85 MWe), corner-fired utility boiler, where recent in situ NOx measurements were made, with variations in coal feedstock quality (including fuel N percentage) load-level and percentage excess air. Predictions are also made for in situ sorbent capture of sulfur pollutants in both combustion (fuel-lean, SO2), and gasification (fuel-rich, H2S) laboratory-scale reactors. Limitations of MARP are identified and work to improve the submodel is outlined.
Comparison of Measurements and Predictions of Flame Structure and Thermal NOx, in a Swirling, Natural Gas Diffusion Flame
Boardman, R.D.; Eatough, C.N.; Germane, G.J. and Smoot, L.D.
Combustion Science and Technology, 20: 1-18, 1993. (Previously presented at the First International Conference on Combustion Technologies For a Clean Environment, Vilamoura, Portugal, September 1991). Funded by Morgantown Energy Technology Center.
A combined thermal and fuel nitric oxide submodel has recently been added to a generalized, 2-dimensional pulverized coal gasification and combustion model (PCGC-2). This model is applicable to reacting and non-reacting gaseous and particle-laden flows. The thermal NO model is based on the extended Zel'dovich mechanism. To perform an evaluation of the NOx submodel, combustion measurements of gas velocities, temperatures, and species concentrations were made in a laboratory-scale, experimental reactor with a 150 kW natural gas flame at an equivalence ratio of 1.05 and a secondary-air swirl number of 1.5. Combustion measurements of velocities and major species concentrations show generally good agreement with predicted values. Gas temperature measurements closely match predictions in the recovery region but fail to show predicted high temperature in the annular region. This study provides an evaluation of a comprehensive combustion model and the NOx submodel that can be useful as a design tool to provide pollutant formation trends in applied systems as combustion parameters are varied.
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.
1992
Comparison of Measurements and Predictions of Flame Structure and Thermal NOx, in a Swirling, Natural Gas Diffusion Flame
Boardman, R.D.; Eatough, C.N.; Germane, G.J. and Smoot, L.D.
Combustion Science and Technology, 1992 (in press). (Previously presented at the First International Conference on Combustion Technologies For a Clean Environment, Vilamoura, Portugal, September 1991.) Funded by Morgantown Energy Technology Center through subcontract from Advanced Fuel Research and ACERC.
A combined thermal and fuel nitric oxide submodel has recently been added to a generalized, 2-dimensional pulverized coal gasification and combustion model (PCGC-2). This model is applicable to reacting and non-reacting gaseous and particle-laden flows. The thermal NO model is based on the extended Zel'dovich mechanism. To perform an evaluation of the NOx submodel, combustion measurements of gas velocities, temperatures, and species concentrations were made in a laboratory-scale, experimental reactor with a 150 kW natural gas flame at an equivalence ratio of 1.05 and a secondary-air swirl number of 1.5. Combustion measurements of velocities and major species concentrations show generally good agreement with predicted values. Gas temperature measurements closely match predictions in the recovery region but fail to show predicted high temperature in the annular region. This study provides an evaluation of a comprehensive combustion model and the NOx submodel that can be useful as a design tool to provide pollutant formation trends in applied systems as combustion parameters are varied.
Modeling Sorbent Injection and Sulfur Capture in Pulverized Coal Combustion
Boardman, R.D.; Brewster, B.S.; Huque, Z.; Smoot, L.D. and Silcox, G.D.
Air Toxic Reduction and Combustion Modeling, 15:1-9, 1992. (Also presented at the ASME International Joint Power Generation Conference, Atlanta, GA, October 1992). Funded by Advanced Fuel Research and ACERC.
A computer model has been developed for predicting mixing and reactions of injected sorbent particles in pulverized coal combustors and gasifiers. A shrinking-core, grain model was used for sulfation. The model accounts for the effects of surface area, pore diffusion, diffusion through the product layer, chemical reaction, and reduction of the pore volume due to grain swelling. The submodel was evaluated for a fuel-lean case and for a fuel-rich case. Predictions were compared with limited experimental data (for the fuel-rich case). The results illustrate the model's capability for predicting the effectiveness of sulfur capture. The importance of sorbent particle properties was also investigated parametrically, and model limitations were identified
1991
Comparison of Measurements and Predictions of Flame Structure and Thermal NOx, in a Swirling, Natural Gas Diffusion Flame
Boardman, R.D.; Eatough, C.N.; Germane, G.J. and Smoot, L.D.
First International Conference on Combustion Technologies For a Clean Environment, Vilamoura, Portugal, September 1991. Funded by Morgantown Energy Technology Center through subcontract from Advanced Fuel Research Co.
A combined thermal and fuel nitric oxide submodel has recently been added to a generalized, 2-dimensional pulverized coal gasification and combustion model (PCGC-2). This model is applicable to reacting and non-reacting gaseous and particle-laden flows. The thermal NO model is based on the extended Zel'dovich mechanism. To perform an evaluation of the NOx submodel, combustion measurements of gas velocities, temperatures, and species concentrations were made in a laboratory-scale, experimental reactor with a 150 kW natural gas flame at an equivalence ratio of 1.05 and a secondary-air swirl number of 1.5. Combustion measurements of velocities and major species concentrations show generally good agreement with predicted values. Gas temperature measurements closely match predictions in the recovery region but fail to show predicted high temperature in the annular region. This study provides an evaluation of a comprehensive combustion model and the NOx submodel that can be useful as a design tool to provide pollutant formation trends in applied systems as combustion parameters are varied.
1989
Measurement and Prediction of Thermal and Fuel NOx
Boardman, R.D.; Smoot, L.D. and Brewster, B.S.
Western States Section, The Combustion Institute, Livermore, California, 1989. Funded by US Department of Energy through subcontract from Advanced Fuel Research Co., and ACERC (National Science Foundation and Associates and Affiliates).
A generalized NOx model is being developed to predict nitric oxide formation in practical combustors. The NOx model incorporates an extended global fuel-NO mechanism and the modified Zeldovich mechanism to predict thermal NO formation. The importance of coupling turbulence with the chemical kinetics for practical combustors is addressed. Thermal NO data for a turbulent gaseous diffusion flame (in a laboratory-scale furnace) are presented. The model is being validated using these previously unpublished data and other pulverized-coal combustion and gasification data from the literature.
1987
Prediction of Nitric Oxide in Advanced Combustion Systems
Boardman, R.D. and Smoot, L.D.
AlChE J., 1987. 14 pgs. Funded by ACERC Consortium: Babcock & Wilcox, Combustion Engineering, Consol, Electric Power Research Institute, Empire State Electrical Energy Research Corp., Foster Wheeler, Pittsburgh Energy Technology Center, Tennessee Valley Authority, and Utah Power & Light.
A computer model to predict nitric oxide (NO) concentrations has been applied to advanced-concept, pulverized-coal systems and evaluated by comparing model predictions with experimental data. Specifically, the effects of pressure, stoichiometric ratio, coal moisture content, particle size, and swirling and non-swirling diffusion flames (Hill et al., 1984; Smith et al., 1986).
The NO model is a subcomponent of a general combustion code that provides theoretical predictions for the temperature, velocity, major species, and other properties at local points throughout turbulent, combusting flow fields (Smoot and Smith, 1985). In the NO model, fuel nitrogen release from the coal is assumed to occur at a rate proportional to total coal weight loss. The volatile nitrogen is assumed to be instantaneously converted to HCN. NO is formed by oxidation of the HCN and is competitively reduced to N2 by reaction with HCN. Global rate expressions for these reactions were measured by the Soete (1985). The model also accounts for the destruction of NO by heterogeneous interaction with char using a rate expression from Levy et al., (1981). All rate parameters are used as reported except for the information of HO. For this rate equation, the pre-exponential factor was increased by a factor of ten. This value is still in within the range of experimental error and was used because it yielded better results. Effects of turbulence on the gaseous reactions are accounted for through use of a joint probability calculation of fluctuating gaseous and coal off-gas mixture fractions. These two progress variables are sufficient to track turbulent temperature and gas concentration variations (Smith et al., 1982). Experimental data sources for model comparisons were selected for axi-symmetric combustion exponents that investigated the variation of key test variables (e.g., pressure or stoichiometric ratio).
Further Evaluation of a Nitric Oxide Model
Boardman, R.D. and Smoot, L.D.
Western States Section, 1987, The Combustion Institute, Provo, UT. 25 pgs. Funded by Morgantown Energy Technology Center through subcontract from Advanced Fuel Research Co.
Further verification of a predictive model for nitric oxide formation during turbulent combustion of coal containing fuels has been conducted. Computations for pulverized coal combustion in CO2-02 mixtures of various percents have been completed. The predicted NO concentrations compare favorably with experimental measurements. Simulations were also completed for entrained-flow gasification in a laboratory-scale combustor. Again, reasonable agreement is demonstrated by comparing laboratory NO maps to predicted NO concentrations. The effects of pressure on NO concentrations were reliably predicted. Calculations were also completed for air-staged combustion in a one-dimensional, laboratory-scale reactor. In general, the trend of decreasing primary zone stoichiometric ratio and variation in staging air location were correctly predicted. The simplified global mechanism expressions of the NO model appear to sufficiently account for the formation and competing destruction of NO in both fuel-lean and fuel-rich environments for different reactor systems and conditions.