Sowa, WA
1992
The Sensitivity of Entrained-Flow Coal Gasification Diffusion Burners to Changes in Geometry
Sowa, W.A.; Hedman, P.O.; Smoot, L.D. and Richards, D.O.
Fuel, 71(5):593-604, 1992. Funded by US Department of Energy, Morgantown Energy Technology Center.
Three axisymmetric diffusion flame burners were designed and installed on a laboratory-scale, downfired, entrained-flow, coal gasifier operated at pressures up to 560 kPa. Each burner was studied by varying reactor pressure, oxygen/coal ratio and steam/coal ratio. The gasifier performance was assessed by collecting space-resolved gas and char samples in the reaction chamber and analyzing them for carbon conversion, gas composition (CO, CO2, H2, H20 and CH4) and cold gas efficiency. Burner geometry affected carbon conversion, gas composition and cold gas efficiency. Each burner had unique flame structural characteristics that resulted in burner-unique trends with reactor pressure, oxygen/coal ratio and steam/coal ratio. At 560 kPa, diffusion flame burner performance approached premixed flame performance. The results from this study suggest that it might be possible to design a diffusion burner that outperforms a fuel-oxidant premixing burner for some operating conditions due to its flame structure and its characteristic energy transfer to the chamber. Performance characteristics of diffusion burners correlated with system pressure, oxygen/coal ratio or steam/coal ratio cannot be generalized into trends representative of all diffusion flame burners.
1990
Furnace Design Using Comprehensive Combustion Models
Smith, P.J.; Sowa, W.A. and Hedman, P.O.
Combustion and Flame, 79 (2), 111-121, 1990. Funded by Brigham Young Unviersity.
A new design methodology is presented that allows for the use of comprehensive coal combustion codes in design applications and provides a priori information on the cost of the optimization. A statistical response surface methodology is used to determine appropriate sample points from the design space at which the computation for the comprehensive code is performed. Statistical regression analysis is used to provide interpolation functions for the optimization process. The optimum design point is then checked with a final comprehensive code calculation. The technique is demonstrated with simple examples for the design of two injectors for an entrained coal gasifier and a burner for a pulverized coal combustor. The three designs demonstrate the method as well as showing significantly different optima for different configurations. The importance of specifying operating conditions independently for different injectors or burners is demonstrated.
1989-1986
Furnace Design Using Comprehensive Combustion Models
Smith, P.J.; Sowa, W.A. and Hedman, P.O.
Accepted for publication in Combustion and Flame, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates) and Brigham Young University.
A new design methodology is presented which allows for the use of comprehensive coal combustion codes in design applications and provides a priori information on the cost of the optimization. A statistical response surface methodology is used to determine appropriate sample points from the design space at which the computation for the comprehensive code are performed. Statistical regression analysis is used to provide interpolating functions for the optimization process. The optimum design point is then checked with a final comprehensive code calculation. The technique is demonstrated with simple examples for design of two injectors for an entrained coal gasifier and of a burner for a pulverized coal combustor. The three designs demonstrate the method as well as showing significantly different optima for different configurations. The importance of specifying operating conditions independently for different injectors or burners is demonstrated.
The Sensitivity of Entrained-Flow Coal Gasification Burners to Changers in Inlet Boundary Conditions
Sowa, W.A.; Hedman, P.O. and Smoot, L.D.
Submitted to Fuel, 1988. 25 pgs. Funded by Morgantown Energy Technology Center.
The impact of diffusion flame burner geometry on entrained flow coal gasification was studied. Three diffusion flame burners were designed and installed on a laboratory-scale, downfired, entrained-flow, coal gasifier operated at pressures up to 560 kPa. Each burner was studied by varying reactor pressure, oxygen/coal ratio, and steam/coal ratio. Gasifier performance was assessed by collecting space-resolved gas and char samples in the reaction chamber and analyzing them for carbon conversion, gas composition (CO, CO2, H2, H2O, and CH4), and cold gas efficiency. Burner geometry affected carbon conversion, gas composition, and cold gas efficiency. Each burner had unique flame structural characteristics that resulted in burner-unique trends with reactor pressure, oxygen/coal ratio, and steam/coal ratio.
The Impact of Diffusion Flame Injectors on Entrained Coal Gasification
Sowa, W.A.; Hedman, P.O. and Smoot, L.D.
Western States Section, 1988, The Combustion Institute, Salt Lake City, UT. Funded by Morgantown Energy Technology Center.
The impact of diffusion flame burner geometry on entrained flow coal gasification was studied. Three diffusion flame burners were designed and installed on a laboratory-scale, downfired, entrained-flow, coal gasifier operated at pressures up to 560 kPa. Each burner was studied by varying reactor pressure, oxygen/coal ratio and steam/coal ratio. Gasifier performance was assessed by collecting space resolved gas and char samples in the reaction chamber and analyzing them for carbon conversion, gas compositions (CO, CO2, H2, H2O, and CH4), and cold gas efficiency. Burner geometry was found to significantly affect carbon conversion, gas compositions, and cold gas efficiency. Each burner had unique flame structure characteristics that resulted in burner-unique trends with reactor pressure, oxygen/coal ratio and steam/coal ratio.
The Sensitivity of Entrained-Flow Coal Gasification Diffusion Burners to Changes in Geometry
Sowa, W.A.; Hedman, P.O. and Smoot, L.D.
Western States Conference, 1987. 25 pgs. Funded by Morgantown Energy Technology Center.
The impact of diffusion flame burner geometry on entrained flow coal gasification was studied. Three diffusion flame burners were designed and installed on a laboratory-scale, downfield, entrained-flow, coal gasifier operated at pressures up to 560 kPa. Each burner was studied by varying reactor pressure, oxygen/coal ratio and steam/coal ratio. Gasifier performance was assessed by collecting space resolved gas and char samples in the reaction chamber and analyzing them for carbon conversion, gas compositions (CO, CO2, H2, H2O, and CH4), and cold gas efficiency. Burner geometry was found to significantly affect carbon conversion, gas compositions, and cold gas efficiency. Each burner had unique flame structure characteristics which resulted in burner-unique trends with reactor pressure, oxygen/coal ratio and steam/coal ratio.
Statistical Distributions of Coal Particle Sizes in Pulverized-Coal Combustion and Gasification
McDonald, J.B.; Richards, D.O.; Smith, P.J. and Sowa, W.A.
Annual Meeting of the American Statistical Assoc., 1986. 18 pgs. Not externally funded.
Coal particle size distributions for a Utah bituminous coal and a Wyoming subbituminous coal were modeled using four different probability density functions (GB1, GB2, lognormal, and lognormal by method of moments) and two engineering approximations. The pdf models of the particle size distributions were discretized and compared to the engineering approximations by simulating a coal combustion case and a coal gasification case using the comprehensive combustion model, PCGC-2. The gasification case used the Utah coal and the combustion case used the Wyoming coal. Significant differences were noticed between predictions using engineering approximations of the particle size distribution and predictions using discretized pdf approximations of the particle size distribution. The different methods of describing the particle size distribution affected most notably the simulators prediction of NOx.
The Behavior of Chlorine in Kentucky and Illinois Coals During Combustion and Its Effects on Ash Deposits
Sowa, W.A.; Hedman, P.O.; Smoot, L.D. and Blackham, A.U.
Western States Section, 1986, The Combustion Institute, Tucson, AZ. Also accepted for publication in Fuel, 1988. 34 pgs. Funded by Tennessee Valley Authority.
Ash deposition tests were performed in a modified pulverized coal combustor with four different coals: low chlorine Kentucky No. 9, and Kentucky No. 11, and high chlorine Illinois No. 5 and Illinois No. 6. The amount of coal available for testing differed markedly between coal types ranging from 100-1000 kg. per coal type. Several repeated one-hour combustion tests were performed for all four coals. Each firing consumed 15-25 kg. of coal. Ash deposition tests provided samples from simulated waterwall and superheater probes, and from an exhaust cyclone and a water-quenched char sample probe. Measured physical properties included, ash chemical analyses, proximate and elemental analyses of both raw coal and ash deposits, ash fusion temperature tests, ash sintering temperature tests, ash shear and compressive strength analyses, and ash thermal conductivity and emittance. Chlorine was found to release quickly from the coal to the gas phase. Gas phase chlorine was found to release quickly from the coal to the gas phase. Gas phase chlorine condensed and concentrated on the waterwall collection surfaces. The amount of chlorine that condensed onto the ash collection surfaces was dependent on the temperature of the collection surface. The colder surfaces had the highest chlorine concentrations. Corrosion of the stainless steel test surfaces was observed during the combustion tests with the Illinois coals. The carbon and chlorine conversion rate from the char appeared to be equal for carbon conversion levels above 65%. Ash fusion temperature, ash sintering temperature, emittance, thermal conductivity, shear strength and compressive strength measurements which were performed on samples from the waterwall and superheater probes showed no observable differences between the four coal types tested. The one-hour firings were probably too short for the ash deposits to reflect the influence of metal corrosion on the measured physical properties. Emittance, ash sintering temperature, compressive strength and shear strength were dependent on sample location.
Furnace Design and Comprehensive Coal Combustion Models
Smith, P.J.; Sowa, W.A. and Hedman, P.O.
ASME Annual Meeting, 1986. 14 pgs. Funded by Morgantown Energy Technology Center and Brigham Young University.
Comprehensive coal combustion (including gasification) models have received little to no use in furnace design applications due, in part, to their large computational burden when used in conjunction with some design optimization strategy. This paper presents a new design methodology that allows for the use of comprehensive coal combustion codes in design applications and provides a priori information on the cost of the optimization. A statistical response surface methodology is used to determine appropriate sample points from the design space at which the computations for the comprehensive code are performed. Statistical regression analysis is used to provide interpolating functions for the optimization package. The final design point is then checked with a final comprehensive code calculation.
The technique is demonstrated with simple examples for design of two injectors for an entrained coal gasifier and of a burner for a pulverized coal combustor. The three designs show the utility of the method as well as showing significantly different optima for different configurations. The importance of specifying operating conditions independently for different injectors or burners is demonstrated. The utility of comprehensive coal combustion codes as another design tool is demonstrated.
Effects of Flame Type and Pressure on Entrained Coal Gasification
Azuhata, S.; Hedman, P.O.; Smoot, L.D. and Sowa, W.A.
Fuel, 65, 1511-1515, 1986. 5 pgs. Funded by Morgantown Energy Technology Center.
An experimental study of pulverized coal gasification was performed to evaluate the effects of flame type and gasifier pressure. O2/coal ratio (0.53-1.09 kg/kg), coal feed rate (22.9-34.5 kg/h), and pressure (100, 500 and 1050 K Pa) were varied for premixed and diffusion flames in the gasifier. Premixing of coal and oxygen markedly increased carbon conversion, compared with that for diffusion flames at constant pressure. Above an O2/coal ratio of 0.8, carbon conversion increased with increasing pressure for diffusion flames, but no such increase was observed for premixed flames. At higher pressures in premixed flames, all reactions were completed near the burner with little change in gas concentrations elsewhere in the gasifier.
Statistical Optimization of Feed Streams for an Entrained-Flow Coal Gasifier Using the PCGC-2 Simulator
Sowa, W.A.; Free, J.C.; Smith, P.J. and Hurst, T.N.
ASME Annual Meeting, 1986. 5 pages. Funded by US Department of Energy.
Concepts from statistical response surface methodology (RSM) and nonlinear optimization theory have been combined in a method for efficiently searching a "design space" when using large-scale analysis. The method is applied to a theoretical study of entrained-flow coal gasification, using PCGC-2, a two-dimensional, axisymmetric model developed at Brigham Young University, that predicts local properties in a reaction chamber. RSM was used to sample the design space and to construct a regression model, which was then linked to OPTDES, BYU, a program containing several nonlinear programming algorithms.
Two test plans were used to verify the performance of the RSM optimization algorithm in solving a gasification example problem. The method is shown to provide accurate results, while de-coupling the search and analysis phases of optimization. The importance of a proper test plan for conducting an un-biased exploration of design space is also demonstrated by comparing the results of the two test plans.
Sowa, WA
1992
The Sensitivity of Entrained-Flow Coal Gasification Diffusion Burners to Changes in Geometry
Sowa, W.A.; Hedman, P.O.; Smoot, L.D. and Richards, D.O.
Fuel, 71(5):593-604, 1992. Funded by US Department of Energy, Morgantown Energy Technology Center.
Three axisymmetric diffusion flame burners were designed and installed on a laboratory-scale, downfired, entrained-flow, coal gasifier operated at pressures up to 560 kPa. Each burner was studied by varying reactor pressure, oxygen/coal ratio and steam/coal ratio. The gasifier performance was assessed by collecting space-resolved gas and char samples in the reaction chamber and analyzing them for carbon conversion, gas composition (CO, CO2, H2, H20 and CH4) and cold gas efficiency. Burner geometry affected carbon conversion, gas composition and cold gas efficiency. Each burner had unique flame structural characteristics that resulted in burner-unique trends with reactor pressure, oxygen/coal ratio and steam/coal ratio. At 560 kPa, diffusion flame burner performance approached premixed flame performance. The results from this study suggest that it might be possible to design a diffusion burner that outperforms a fuel-oxidant premixing burner for some operating conditions due to its flame structure and its characteristic energy transfer to the chamber. Performance characteristics of diffusion burners correlated with system pressure, oxygen/coal ratio or steam/coal ratio cannot be generalized into trends representative of all diffusion flame burners.
1990
Furnace Design Using Comprehensive Combustion Models
Smith, P.J.; Sowa, W.A. and Hedman, P.O.
Combustion and Flame, 79 (2), 111-121, 1990. Funded by Brigham Young Unviersity.
A new design methodology is presented that allows for the use of comprehensive coal combustion codes in design applications and provides a priori information on the cost of the optimization. A statistical response surface methodology is used to determine appropriate sample points from the design space at which the computation for the comprehensive code is performed. Statistical regression analysis is used to provide interpolation functions for the optimization process. The optimum design point is then checked with a final comprehensive code calculation. The technique is demonstrated with simple examples for the design of two injectors for an entrained coal gasifier and a burner for a pulverized coal combustor. The three designs demonstrate the method as well as showing significantly different optima for different configurations. The importance of specifying operating conditions independently for different injectors or burners is demonstrated.
1989-1986
Furnace Design Using Comprehensive Combustion Models
Smith, P.J.; Sowa, W.A. and Hedman, P.O.
Accepted for publication in Combustion and Flame, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates) and Brigham Young University.
A new design methodology is presented which allows for the use of comprehensive coal combustion codes in design applications and provides a priori information on the cost of the optimization. A statistical response surface methodology is used to determine appropriate sample points from the design space at which the computation for the comprehensive code are performed. Statistical regression analysis is used to provide interpolating functions for the optimization process. The optimum design point is then checked with a final comprehensive code calculation. The technique is demonstrated with simple examples for design of two injectors for an entrained coal gasifier and of a burner for a pulverized coal combustor. The three designs demonstrate the method as well as showing significantly different optima for different configurations. The importance of specifying operating conditions independently for different injectors or burners is demonstrated.
The Sensitivity of Entrained-Flow Coal Gasification Burners to Changers in Inlet Boundary Conditions
Sowa, W.A.; Hedman, P.O. and Smoot, L.D.
Submitted to Fuel, 1988. 25 pgs. Funded by Morgantown Energy Technology Center.
The impact of diffusion flame burner geometry on entrained flow coal gasification was studied. Three diffusion flame burners were designed and installed on a laboratory-scale, downfired, entrained-flow, coal gasifier operated at pressures up to 560 kPa. Each burner was studied by varying reactor pressure, oxygen/coal ratio, and steam/coal ratio. Gasifier performance was assessed by collecting space-resolved gas and char samples in the reaction chamber and analyzing them for carbon conversion, gas composition (CO, CO2, H2, H2O, and CH4), and cold gas efficiency. Burner geometry affected carbon conversion, gas composition, and cold gas efficiency. Each burner had unique flame structural characteristics that resulted in burner-unique trends with reactor pressure, oxygen/coal ratio, and steam/coal ratio.
The Impact of Diffusion Flame Injectors on Entrained Coal Gasification
Sowa, W.A.; Hedman, P.O. and Smoot, L.D.
Western States Section, 1988, The Combustion Institute, Salt Lake City, UT. Funded by Morgantown Energy Technology Center.
The impact of diffusion flame burner geometry on entrained flow coal gasification was studied. Three diffusion flame burners were designed and installed on a laboratory-scale, downfired, entrained-flow, coal gasifier operated at pressures up to 560 kPa. Each burner was studied by varying reactor pressure, oxygen/coal ratio and steam/coal ratio. Gasifier performance was assessed by collecting space resolved gas and char samples in the reaction chamber and analyzing them for carbon conversion, gas compositions (CO, CO2, H2, H2O, and CH4), and cold gas efficiency. Burner geometry was found to significantly affect carbon conversion, gas compositions, and cold gas efficiency. Each burner had unique flame structure characteristics that resulted in burner-unique trends with reactor pressure, oxygen/coal ratio and steam/coal ratio.
The Sensitivity of Entrained-Flow Coal Gasification Diffusion Burners to Changes in Geometry
Sowa, W.A.; Hedman, P.O. and Smoot, L.D.
Western States Conference, 1987. 25 pgs. Funded by Morgantown Energy Technology Center.
The impact of diffusion flame burner geometry on entrained flow coal gasification was studied. Three diffusion flame burners were designed and installed on a laboratory-scale, downfield, entrained-flow, coal gasifier operated at pressures up to 560 kPa. Each burner was studied by varying reactor pressure, oxygen/coal ratio and steam/coal ratio. Gasifier performance was assessed by collecting space resolved gas and char samples in the reaction chamber and analyzing them for carbon conversion, gas compositions (CO, CO2, H2, H2O, and CH4), and cold gas efficiency. Burner geometry was found to significantly affect carbon conversion, gas compositions, and cold gas efficiency. Each burner had unique flame structure characteristics which resulted in burner-unique trends with reactor pressure, oxygen/coal ratio and steam/coal ratio.
Statistical Distributions of Coal Particle Sizes in Pulverized-Coal Combustion and Gasification
McDonald, J.B.; Richards, D.O.; Smith, P.J. and Sowa, W.A.
Annual Meeting of the American Statistical Assoc., 1986. 18 pgs. Not externally funded.
Coal particle size distributions for a Utah bituminous coal and a Wyoming subbituminous coal were modeled using four different probability density functions (GB1, GB2, lognormal, and lognormal by method of moments) and two engineering approximations. The pdf models of the particle size distributions were discretized and compared to the engineering approximations by simulating a coal combustion case and a coal gasification case using the comprehensive combustion model, PCGC-2. The gasification case used the Utah coal and the combustion case used the Wyoming coal. Significant differences were noticed between predictions using engineering approximations of the particle size distribution and predictions using discretized pdf approximations of the particle size distribution. The different methods of describing the particle size distribution affected most notably the simulators prediction of NOx.
The Behavior of Chlorine in Kentucky and Illinois Coals During Combustion and Its Effects on Ash Deposits
Sowa, W.A.; Hedman, P.O.; Smoot, L.D. and Blackham, A.U.
Western States Section, 1986, The Combustion Institute, Tucson, AZ. Also accepted for publication in Fuel, 1988. 34 pgs. Funded by Tennessee Valley Authority.
Ash deposition tests were performed in a modified pulverized coal combustor with four different coals: low chlorine Kentucky No. 9, and Kentucky No. 11, and high chlorine Illinois No. 5 and Illinois No. 6. The amount of coal available for testing differed markedly between coal types ranging from 100-1000 kg. per coal type. Several repeated one-hour combustion tests were performed for all four coals. Each firing consumed 15-25 kg. of coal. Ash deposition tests provided samples from simulated waterwall and superheater probes, and from an exhaust cyclone and a water-quenched char sample probe. Measured physical properties included, ash chemical analyses, proximate and elemental analyses of both raw coal and ash deposits, ash fusion temperature tests, ash sintering temperature tests, ash shear and compressive strength analyses, and ash thermal conductivity and emittance. Chlorine was found to release quickly from the coal to the gas phase. Gas phase chlorine was found to release quickly from the coal to the gas phase. Gas phase chlorine condensed and concentrated on the waterwall collection surfaces. The amount of chlorine that condensed onto the ash collection surfaces was dependent on the temperature of the collection surface. The colder surfaces had the highest chlorine concentrations. Corrosion of the stainless steel test surfaces was observed during the combustion tests with the Illinois coals. The carbon and chlorine conversion rate from the char appeared to be equal for carbon conversion levels above 65%. Ash fusion temperature, ash sintering temperature, emittance, thermal conductivity, shear strength and compressive strength measurements which were performed on samples from the waterwall and superheater probes showed no observable differences between the four coal types tested. The one-hour firings were probably too short for the ash deposits to reflect the influence of metal corrosion on the measured physical properties. Emittance, ash sintering temperature, compressive strength and shear strength were dependent on sample location.
Furnace Design and Comprehensive Coal Combustion Models
Smith, P.J.; Sowa, W.A. and Hedman, P.O.
ASME Annual Meeting, 1986. 14 pgs. Funded by Morgantown Energy Technology Center and Brigham Young University.
Comprehensive coal combustion (including gasification) models have received little to no use in furnace design applications due, in part, to their large computational burden when used in conjunction with some design optimization strategy. This paper presents a new design methodology that allows for the use of comprehensive coal combustion codes in design applications and provides a priori information on the cost of the optimization. A statistical response surface methodology is used to determine appropriate sample points from the design space at which the computations for the comprehensive code are performed. Statistical regression analysis is used to provide interpolating functions for the optimization package. The final design point is then checked with a final comprehensive code calculation.
The technique is demonstrated with simple examples for design of two injectors for an entrained coal gasifier and of a burner for a pulverized coal combustor. The three designs show the utility of the method as well as showing significantly different optima for different configurations. The importance of specifying operating conditions independently for different injectors or burners is demonstrated. The utility of comprehensive coal combustion codes as another design tool is demonstrated.
Effects of Flame Type and Pressure on Entrained Coal Gasification
Azuhata, S.; Hedman, P.O.; Smoot, L.D. and Sowa, W.A.
Fuel, 65, 1511-1515, 1986. 5 pgs. Funded by Morgantown Energy Technology Center.
An experimental study of pulverized coal gasification was performed to evaluate the effects of flame type and gasifier pressure. O2/coal ratio (0.53-1.09 kg/kg), coal feed rate (22.9-34.5 kg/h), and pressure (100, 500 and 1050 K Pa) were varied for premixed and diffusion flames in the gasifier. Premixing of coal and oxygen markedly increased carbon conversion, compared with that for diffusion flames at constant pressure. Above an O2/coal ratio of 0.8, carbon conversion increased with increasing pressure for diffusion flames, but no such increase was observed for premixed flames. At higher pressures in premixed flames, all reactions were completed near the burner with little change in gas concentrations elsewhere in the gasifier.
Statistical Optimization of Feed Streams for an Entrained-Flow Coal Gasifier Using the PCGC-2 Simulator
Sowa, W.A.; Free, J.C.; Smith, P.J. and Hurst, T.N.
ASME Annual Meeting, 1986. 5 pages. Funded by US Department of Energy.
Concepts from statistical response surface methodology (RSM) and nonlinear optimization theory have been combined in a method for efficiently searching a "design space" when using large-scale analysis. The method is applied to a theoretical study of entrained-flow coal gasification, using PCGC-2, a two-dimensional, axisymmetric model developed at Brigham Young University, that predicts local properties in a reaction chamber. RSM was used to sample the design space and to construct a regression model, which was then linked to OPTDES, BYU, a program containing several nonlinear programming algorithms.
Two test plans were used to verify the performance of the RSM optimization algorithm in solving a gasification example problem. The method is shown to provide accurate results, while de-coupling the search and analysis phases of optimization. The importance of a proper test plan for conducting an un-biased exploration of design space is also demonstrated by comparing the results of the two test plans.