Eatough, CN
1999
Components, Formulations, Solutions, Evaluation, and Application of Comprehensive Combustion Mode
Eaton, A.M.; Smoot, L.D.; Hill, S.C. and Eatough, C.N.
Progress in Energy and Combustion Science, 25:387-436 (1999).
Development and application of comprehensive, multidimensional, computational combustion models are increasing at a significant pace across the world. While once confined to specialized research computer codes, these combustion models are becoming more readily accessible as features in commercially available computational fluid dynamics (CFD) computer codes. Simulations made with such computer codes offer great potential for use in analyzing, designing, retrofitting, and optimizing the performance of fossil-fuel combustion and conversion systems.
The purpose of this paper is to provide an overview of comprehensive combustion modeling technology as applied to fossil-fuel combustion processes. This overview is divided into three main parts. First, a brief review of the state-of-the-art of the various components or submodels that are required in a comprehensive combustion model is presented. These submodels embody mathematical and numerical representations of the fundamental principles that characterize the physico-chemical phenomena of interest. The submodel review is limited to those required for characterizing non-premixed, gaseous and pulverized coal gasification and combustion processes. A summary of the submodels that are available in representative computer codes is also presented.
Second, the kinds of data required to evaluate and validate the predictions of comprehensive combustion codes are considered. To be viewed with confidence, code simulations must have been rigorously evaluated and validated by comparison with appropriate experimental data, preferably from a variety of combustor geometries at various geometric scales. Three sets of validation data are discussed in detail. Two sets are from the highly instrumented, pilot-scale combustor called the controlled profile reactor (CPR) (one natural gas-fired and one coal-fired), and the other set is for a full-scale, corner-fired 85 MWe utility boiler.
Third, representative applications of comprehensive combustion models are summarized, and three sets of model simulations are compared with experimental data. The model simulations for the three test cases were made using two commonly used, CFD-based computer codes with comprehensive combustion model features, PCGC-3 and FLUENT 4.4. In addition to the standard version of FLUENT, predictions were also made with a version of FLUENT incorporating advanced submodels for coal reactions and NO pollutant formation.
1996
Devolatilization of Large Coal Particles at High Pressure
Eatough, C.N. and Smoot, L.D.
Fuel, 75(3):1601-1606, 1996. Funded by ACERC.
Devolatilization times of large (0.1 and 0.2g) Utah hvBb and North Dakota lignite coal particles, in the range 15-30 s, were measured in the air at 101 and 507 kPa, at air temperatures of 900 and 1200 K in a connective flow reactor. Visual observations indicated infrequent heterogeneous ignition of the lignite prior to devolatilization and occasional explosion of bituminous coal particles during devolatilization. Devolatilization times were correlated with the temperature, pressure and particle size. Power-law exponents for tests at 101 kPa and 900 K were determined to be 2.5 for Utah hvBb coal and 2.2 for North Dakota lignite. At 507 kPa and 900 K, exponents decreased to 1.6 for both Utah and North Dakota lignite.
1994
Effect of Pressure on Oxidation Rates of MM-Sized Char
Bateman, K.J.; Smoot, L.D.; Germane, G.J.; Blackham, A.U. and Eatough, C.N.
Fuel, 1994 (in press). Funded by US Department of Energy/Morgantown Energy Technology Center and ACERC.
Mass loss and burnout ties of large (five and eight millimeter diameter) char particles at pressures between 101 to 760 kPa have been measured in a newly designed and constructed high-pressure reactor. A cantilever balance attachment was fitted to the reactor to measure instantaneous particle mass while an optical pyrometer measured particle temperature continuously. The process was also videotaped at 1/30 s frame speed. Sixty-two combustion experiments produced burning and oxidation times for two sizes of Utah bituminous (HVBB) coal and North Dakota Lignite (L) at 101, 507, 760 kPa total pressure. The reactor air temperatures were about 900 or 1200 K while the airflow Reynolds Number was varied by a factor of two. Coal particles were placed in a platinum-wire basket inside the reactor at the end of the balance beam. The oxidation process was recorded by computer and on videotape, while continuous char oxidation rates were measured to burnout. An ash layer accumulated around the particles, and receded as the char was consumed. In all of the tests, including the elevated pressure tests, a linear decrease in the cube root of char mass with time was observed during char oxidation until near the end of burnout. Changes in air velocity had little effect on oxidation times while either increasing gas temperature or increasing pressure from 101 kPa to 507 kPa reduced oxidation times by about one-quarter. Further increase in pressure caused no further reduction in burn time. Pairs of nearly equally sized particles of coal had oxidation times similar to single particles that had a mass equal to the sum of the pairs.
A Facility for High-Pressure Measurement of Reaction Rates of MM-Sized Coal
Bateman, K.J.; Germane, G.J.; Smoot, L.D. and Eatough, C.N.
Energy & Fuels, 1994 (in press). Funded by US Department of Energy/Morgantown Energy Technology Center and ACERC.
A study was undertaken to design, construct, characterize, and demonstrate a new facility for determination of reaction rates of large coal particles at elevated pressures. A cantilever balance attachment (CBA) was designed, fabricated, and utilized in conjunction with the existing High Pressure Controlled Profile (HPCP) reactor. Large particle (8mm diameter) combustion experiments of Utah HVBB coal at both atmospheric and elevated pressures were performed to demonstrate the facility's capabilities. Measurements were obtained of particle mass loss rate and surface temperature coupled with a video record for visual observation.
1993
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.
Process Data and Strategies
Germane, G.J.; Eatough, C.N. and Cannon, J.N.
Chapter 2, Fundamentals of Coal Combustion: For Clean and Efficient Use, (L.D. Smoot, ed.), Elsevier Science Publishers, The Netherlands, 1993. Funded by ACERC.
This chapter documents the measurement methods and multidimensional data for evaluation of combustion models. Data are reported for several scales from laboratory to full-scale furnaces. The design of advanced combustion systems and processes for gas, liquid and solid fossil fuels can be greatly enhanced by the utilization of verified predictive and interpretive combustion models. Development of an accurate three-dimensional model applicable to non-reacting and reacting flow systems, and specifically coal combustion and entrained flow gasification, is a primary research initiative of ACERC, and is also being pursued in several other countries. Once the code, with appropriate submodels, has been completed, it is necessary to make comparisons of code predictions to data from turbulent flames in reactors that embody various aspects of turbulent combustion of coal, oil, gas or slurry fuels. Consequently, data from a range of different-sized facilities are necessary in order to adequately demonstrate the adequacy of the code predictions, and to establish the degree of precision that the code can give in making predictions for industrial furnaces. Such detailed data gives new insights into combustion processes and strategies. The detailed measurements possible in the laboratory-scale facilities complement the coarser or sparser measurements of three-dimensional flow patterns and flame heat transfer characteristics obtained in industrial and utility furnaces.
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.
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.
1988-1986
Lignite Slurry Spray Characterization and Combustion Studies
Eatough, C.N.; Rawlins, D.C.; Germane, G.J. and Smoot, L.D.
Western States Section, The Combustion Institute, Dana Point, California, 1988. Funded by US Department of Energy (Morgantown Energy Technology Center) and ACERC (National Science Foundation Associates and Affiliates).
Lignite slurry atomization and combustion characteristics were studied using two atomizers, one developed at Brigham Young University (laboratory nozzle) and the other a Parker-Hannifin Model 6840610 M3 atomizer (commercial nozzle). These nozzles were used because of the significantly different spray patterns produced by each. In these cold-flow studies, it was found that the laboratory nozzle produced a solid cone type spray pattern with the highest mass flux near the spray center line. The commercial nozzle has a hollow cone spray pattern with a larger spray angle. Atomization studies were performed with these nozzles to determine the effect of atomizing air to slurry mass flow ratio (A/S) on particle/droplet size and velocity, and slurry spray mass distribution. These measurements were then used to study the effect of particle/droplet size and velocity, and spray mass distribution on carbon burnout in a laboratory scale reactor using hot-water dried lignite slurry as a fuel. Both the laboratory and commercial nozzles follow the same trends for mean droplet size and droplet velocity with variation in A/S. As expected, mean droplet size decreased with A/S and velocity increased with A/S. Spray angle decreased for the laboratory nozzle but increased for the commercial nozzle with increase in A/S.
Analysis of combustion data indicates an expected strong dependence of burnout on particle/droplet size. Burnout increased markedly as particle/droplet size decreased. Burnout was also affected by the mass distribution of the slurry spray. Large spray angles directed slurry to the relatively cool reactor walls resulting in lower burnout values. Burnout values from both nozzles followed the same trends with regard to droplet size. Burnout increased with decreasing mean droplet size to about 50 mm, which corresponded closely with the coal particle size in the slurry which has a mean diameter of about 40 mm. A mean droplet diameter larger than about 80 mm with a 300 mm top size could not sustain combustion in the laboratory reactor.
A combustion map of burnout values was made using the laboratory nozzle at an A/S of 0.7, swirl number of 1.5 and SR of 1.1.
Lignite Slurry Atomizer Spray Distribution and Characterization Studies
Eatough, C.N.; Germane, G.J. and Smoot, L.D.
8th International Symposium on Coal Slurry Fuels Preparation and Utilization, 1986, Orlando, FL. 12 pgs. Funded by Morgantown Energy Technology Center.
The Brigham Young University (BYU) Combustion Laboratory has been investigating the combustion characteristics of dried, low-rank coal-water slurries under contract to the US Department of Energy's Grand Forks Project Office. This paper contains results of atomization studies of low-rank, coal-water slurry provided by the Grand Forks Project Office for a laboratory nozzle and a commercial atomizer.
Photographic techniques were used to characterize 58 wt% coal-water slurry sprays produced by a laboratory air-blast nozzle, used for coal slurry combustion tests in the Combustion Laboratory, and a Parker-Hannifin Model 6480610 M3 atomizer. Studies in non-reacting slurry sprays to determine spray droplet size and droplet velocities, and separate slurry spray mass distribution tests were conducted. The variables for all spray tests were the mass ratio of atomizing air to slurry fuel flow, and nozzle type. Swirl number was varied only for spray mass distribution tests.
Results of the spray droplet measurements show that the mean droplet diameter of the slurry spray is strongly dependent on the air to CWM mass ratio and essentially independent of the mass flow rate of slurry for the range in flow rates tested. The laboratory nozzle produced mean spray droplet diameters about 20% smaller than the commercial atomizer for the same atomizing air to slurry mass flow ratio and slurry mass flow. This indicates that better mixing can occur in a combustor with the laboratory nozzle, though the commercial nozzle was operated well below its design capacity. The laboratory nozzle also produced higher axial velocities than the commercial atomizer, which may result in a shorter particle residence time in the combustor for the laboratory nozzle.
Radial spray mass distribution was measured using a patternator located in two orthogonal positions in a plane perpendicular to the nozzle centerline a short distance form the nozzle tip. The spray mass distribution was characterized by the radius of gyration of the mass of collected slurry on any side of the nozzle centerline. This calculated distance defined a characteristic spray angle. The laboratory nozzle spray pattern is that of a solid cone with higher spray flux near the spray centerline. The commercial atomizer produces a heavy spray flux in an annular cone around the spray centerline. Results show that the both nozzles, spray mass distribution was influenced by atomizing air to slurry mass flow ratio but not by combustion air swirl. The spray flux produced by the laboratory atomizer becomes less evenly distributed and more concentrated along the centerline of the nozzle as the atomizing air to slurry mass flow ratio is increased, while the opposite effect is evident with the commercial nozzle. The effects of the observed difference in spray characteristics for both nozzles on carbon burnout during combustion tests are also reported in the paper.
Eatough, CN
1999
Components, Formulations, Solutions, Evaluation, and Application of Comprehensive Combustion Mode
Eaton, A.M.; Smoot, L.D.; Hill, S.C. and Eatough, C.N.
Progress in Energy and Combustion Science, 25:387-436 (1999).
Development and application of comprehensive, multidimensional, computational combustion models are increasing at a significant pace across the world. While once confined to specialized research computer codes, these combustion models are becoming more readily accessible as features in commercially available computational fluid dynamics (CFD) computer codes. Simulations made with such computer codes offer great potential for use in analyzing, designing, retrofitting, and optimizing the performance of fossil-fuel combustion and conversion systems.
The purpose of this paper is to provide an overview of comprehensive combustion modeling technology as applied to fossil-fuel combustion processes. This overview is divided into three main parts. First, a brief review of the state-of-the-art of the various components or submodels that are required in a comprehensive combustion model is presented. These submodels embody mathematical and numerical representations of the fundamental principles that characterize the physico-chemical phenomena of interest. The submodel review is limited to those required for characterizing non-premixed, gaseous and pulverized coal gasification and combustion processes. A summary of the submodels that are available in representative computer codes is also presented.
Second, the kinds of data required to evaluate and validate the predictions of comprehensive combustion codes are considered. To be viewed with confidence, code simulations must have been rigorously evaluated and validated by comparison with appropriate experimental data, preferably from a variety of combustor geometries at various geometric scales. Three sets of validation data are discussed in detail. Two sets are from the highly instrumented, pilot-scale combustor called the controlled profile reactor (CPR) (one natural gas-fired and one coal-fired), and the other set is for a full-scale, corner-fired 85 MWe utility boiler.
Third, representative applications of comprehensive combustion models are summarized, and three sets of model simulations are compared with experimental data. The model simulations for the three test cases were made using two commonly used, CFD-based computer codes with comprehensive combustion model features, PCGC-3 and FLUENT 4.4. In addition to the standard version of FLUENT, predictions were also made with a version of FLUENT incorporating advanced submodels for coal reactions and NO pollutant formation.
1996
Devolatilization of Large Coal Particles at High Pressure
Eatough, C.N. and Smoot, L.D.
Fuel, 75(3):1601-1606, 1996. Funded by ACERC.
Devolatilization times of large (0.1 and 0.2g) Utah hvBb and North Dakota lignite coal particles, in the range 15-30 s, were measured in the air at 101 and 507 kPa, at air temperatures of 900 and 1200 K in a connective flow reactor. Visual observations indicated infrequent heterogeneous ignition of the lignite prior to devolatilization and occasional explosion of bituminous coal particles during devolatilization. Devolatilization times were correlated with the temperature, pressure and particle size. Power-law exponents for tests at 101 kPa and 900 K were determined to be 2.5 for Utah hvBb coal and 2.2 for North Dakota lignite. At 507 kPa and 900 K, exponents decreased to 1.6 for both Utah and North Dakota lignite.
1994
Effect of Pressure on Oxidation Rates of MM-Sized Char
Bateman, K.J.; Smoot, L.D.; Germane, G.J.; Blackham, A.U. and Eatough, C.N.
Fuel, 1994 (in press). Funded by US Department of Energy/Morgantown Energy Technology Center and ACERC.
Mass loss and burnout ties of large (five and eight millimeter diameter) char particles at pressures between 101 to 760 kPa have been measured in a newly designed and constructed high-pressure reactor. A cantilever balance attachment was fitted to the reactor to measure instantaneous particle mass while an optical pyrometer measured particle temperature continuously. The process was also videotaped at 1/30 s frame speed. Sixty-two combustion experiments produced burning and oxidation times for two sizes of Utah bituminous (HVBB) coal and North Dakota Lignite (L) at 101, 507, 760 kPa total pressure. The reactor air temperatures were about 900 or 1200 K while the airflow Reynolds Number was varied by a factor of two. Coal particles were placed in a platinum-wire basket inside the reactor at the end of the balance beam. The oxidation process was recorded by computer and on videotape, while continuous char oxidation rates were measured to burnout. An ash layer accumulated around the particles, and receded as the char was consumed. In all of the tests, including the elevated pressure tests, a linear decrease in the cube root of char mass with time was observed during char oxidation until near the end of burnout. Changes in air velocity had little effect on oxidation times while either increasing gas temperature or increasing pressure from 101 kPa to 507 kPa reduced oxidation times by about one-quarter. Further increase in pressure caused no further reduction in burn time. Pairs of nearly equally sized particles of coal had oxidation times similar to single particles that had a mass equal to the sum of the pairs.
A Facility for High-Pressure Measurement of Reaction Rates of MM-Sized Coal
Bateman, K.J.; Germane, G.J.; Smoot, L.D. and Eatough, C.N.
Energy & Fuels, 1994 (in press). Funded by US Department of Energy/Morgantown Energy Technology Center and ACERC.
A study was undertaken to design, construct, characterize, and demonstrate a new facility for determination of reaction rates of large coal particles at elevated pressures. A cantilever balance attachment (CBA) was designed, fabricated, and utilized in conjunction with the existing High Pressure Controlled Profile (HPCP) reactor. Large particle (8mm diameter) combustion experiments of Utah HVBB coal at both atmospheric and elevated pressures were performed to demonstrate the facility's capabilities. Measurements were obtained of particle mass loss rate and surface temperature coupled with a video record for visual observation.
1993
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.
Process Data and Strategies
Germane, G.J.; Eatough, C.N. and Cannon, J.N.
Chapter 2, Fundamentals of Coal Combustion: For Clean and Efficient Use, (L.D. Smoot, ed.), Elsevier Science Publishers, The Netherlands, 1993. Funded by ACERC.
This chapter documents the measurement methods and multidimensional data for evaluation of combustion models. Data are reported for several scales from laboratory to full-scale furnaces. The design of advanced combustion systems and processes for gas, liquid and solid fossil fuels can be greatly enhanced by the utilization of verified predictive and interpretive combustion models. Development of an accurate three-dimensional model applicable to non-reacting and reacting flow systems, and specifically coal combustion and entrained flow gasification, is a primary research initiative of ACERC, and is also being pursued in several other countries. Once the code, with appropriate submodels, has been completed, it is necessary to make comparisons of code predictions to data from turbulent flames in reactors that embody various aspects of turbulent combustion of coal, oil, gas or slurry fuels. Consequently, data from a range of different-sized facilities are necessary in order to adequately demonstrate the adequacy of the code predictions, and to establish the degree of precision that the code can give in making predictions for industrial furnaces. Such detailed data gives new insights into combustion processes and strategies. The detailed measurements possible in the laboratory-scale facilities complement the coarser or sparser measurements of three-dimensional flow patterns and flame heat transfer characteristics obtained in industrial and utility furnaces.
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.
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.
1988-1986
Lignite Slurry Spray Characterization and Combustion Studies
Eatough, C.N.; Rawlins, D.C.; Germane, G.J. and Smoot, L.D.
Western States Section, The Combustion Institute, Dana Point, California, 1988. Funded by US Department of Energy (Morgantown Energy Technology Center) and ACERC (National Science Foundation Associates and Affiliates).
Lignite slurry atomization and combustion characteristics were studied using two atomizers, one developed at Brigham Young University (laboratory nozzle) and the other a Parker-Hannifin Model 6840610 M3 atomizer (commercial nozzle). These nozzles were used because of the significantly different spray patterns produced by each. In these cold-flow studies, it was found that the laboratory nozzle produced a solid cone type spray pattern with the highest mass flux near the spray center line. The commercial nozzle has a hollow cone spray pattern with a larger spray angle. Atomization studies were performed with these nozzles to determine the effect of atomizing air to slurry mass flow ratio (A/S) on particle/droplet size and velocity, and slurry spray mass distribution. These measurements were then used to study the effect of particle/droplet size and velocity, and spray mass distribution on carbon burnout in a laboratory scale reactor using hot-water dried lignite slurry as a fuel. Both the laboratory and commercial nozzles follow the same trends for mean droplet size and droplet velocity with variation in A/S. As expected, mean droplet size decreased with A/S and velocity increased with A/S. Spray angle decreased for the laboratory nozzle but increased for the commercial nozzle with increase in A/S.
Analysis of combustion data indicates an expected strong dependence of burnout on particle/droplet size. Burnout increased markedly as particle/droplet size decreased. Burnout was also affected by the mass distribution of the slurry spray. Large spray angles directed slurry to the relatively cool reactor walls resulting in lower burnout values. Burnout values from both nozzles followed the same trends with regard to droplet size. Burnout increased with decreasing mean droplet size to about 50 mm, which corresponded closely with the coal particle size in the slurry which has a mean diameter of about 40 mm. A mean droplet diameter larger than about 80 mm with a 300 mm top size could not sustain combustion in the laboratory reactor.
A combustion map of burnout values was made using the laboratory nozzle at an A/S of 0.7, swirl number of 1.5 and SR of 1.1.
Lignite Slurry Atomizer Spray Distribution and Characterization Studies
Eatough, C.N.; Germane, G.J. and Smoot, L.D.
8th International Symposium on Coal Slurry Fuels Preparation and Utilization, 1986, Orlando, FL. 12 pgs. Funded by Morgantown Energy Technology Center.
The Brigham Young University (BYU) Combustion Laboratory has been investigating the combustion characteristics of dried, low-rank coal-water slurries under contract to the US Department of Energy's Grand Forks Project Office. This paper contains results of atomization studies of low-rank, coal-water slurry provided by the Grand Forks Project Office for a laboratory nozzle and a commercial atomizer.
Photographic techniques were used to characterize 58 wt% coal-water slurry sprays produced by a laboratory air-blast nozzle, used for coal slurry combustion tests in the Combustion Laboratory, and a Parker-Hannifin Model 6480610 M3 atomizer. Studies in non-reacting slurry sprays to determine spray droplet size and droplet velocities, and separate slurry spray mass distribution tests were conducted. The variables for all spray tests were the mass ratio of atomizing air to slurry fuel flow, and nozzle type. Swirl number was varied only for spray mass distribution tests.
Results of the spray droplet measurements show that the mean droplet diameter of the slurry spray is strongly dependent on the air to CWM mass ratio and essentially independent of the mass flow rate of slurry for the range in flow rates tested. The laboratory nozzle produced mean spray droplet diameters about 20% smaller than the commercial atomizer for the same atomizing air to slurry mass flow ratio and slurry mass flow. This indicates that better mixing can occur in a combustor with the laboratory nozzle, though the commercial nozzle was operated well below its design capacity. The laboratory nozzle also produced higher axial velocities than the commercial atomizer, which may result in a shorter particle residence time in the combustor for the laboratory nozzle.
Radial spray mass distribution was measured using a patternator located in two orthogonal positions in a plane perpendicular to the nozzle centerline a short distance form the nozzle tip. The spray mass distribution was characterized by the radius of gyration of the mass of collected slurry on any side of the nozzle centerline. This calculated distance defined a characteristic spray angle. The laboratory nozzle spray pattern is that of a solid cone with higher spray flux near the spray centerline. The commercial atomizer produces a heavy spray flux in an annular cone around the spray centerline. Results show that the both nozzles, spray mass distribution was influenced by atomizing air to slurry mass flow ratio but not by combustion air swirl. The spray flux produced by the laboratory atomizer becomes less evenly distributed and more concentrated along the centerline of the nozzle as the atomizing air to slurry mass flow ratio is increased, while the opposite effect is evident with the commercial nozzle. The effects of the observed difference in spray characteristics for both nozzles on carbon burnout during combustion tests are also reported in the paper.