Lemieux, PM
1989
Experimental and Theoretical Studies on the Combustion of Waste Zirconium Sponge in a Rotary Kiln Simulator
Lemieux, P.M.; Silcox, G.D. and Pershing, D.W.
Waste Management, 9:125-137, 1989. Funded by Westinghouse Corp.
Previous experimental studies have indicated that rotary kilns may be suitable combustion systems to incinerate small quantities of off grade zirconium sponge produced during the manufacturing of zirconium for the nuclear industry. This paper describes a mathematical model of zirconium sponge combustion in a rotary kiln environment and specifically examines the use of the bed submodel to analyze detailed zirconium combustion data obtained previously in a rotary kiln simulator. The results of this analysis indicated that the experimentally observed burning rates could be predicted within 25% based on available transport correlations and current understanding of zirconium combustion. Without any adjustment of the physical parameters in the model, both the experimental results and the model predictions indicated that the primary combustion parameters are the bulk oxygen concentration within the kin and the local kiln bed temperature. Charge size was found to be less significant. A detailed analysis of the theoretical predictions indicates that the zirconium sponge oxidation rate is controlled by three sequential processes (the convection of oxygen from the bulk gas to the top of the bed, the diffusion of oxygen through the bed to the particle surface, and the diffusion of oxygen through previously formed zirconium dioxide product to the unreacted zirconium metal). Under conditions typical of commercial rotary kiln operation all three of these resistances appear to be significant. Both the experimental data and the model suggest that intrinsic chemical kinetics are fast and not controlling except during the first few minutes after the zirconium is charges. The model assumes that the zirconium oxide product layer increases until it reaches a maximum value after which it remains constant due to continuous formation and abrasion.
1987
The Design and Construction of a Rotary Kiln Simulator for Use in Studying the Incineration of Hazardous Waste
Lemieux, P.M. and Pershing, D.W.
Submitted to Review of Scientific Instrument, 1987. Funded by Westinghouse and National Science Foundation/Presidential Young Investigators.
Rotary kiln systems are widely used in industrial applications to transfer energy from high temperature flames to irregular solids. Recently these systems have been shown to be suitable for the incineration of hazardous solid waste materials and the thermal treatment of contaminated soils. Destruction and removal efficiencies in excess of 99.99% have been reported for hazardous species, but the rate controlling steps of the incineration process are not well understood.
This paper describes the design, construction and operation of a laboratory scale simulator that was developed to investigate the fundamentals of hazardous incineration in a rotary kiln environment. This 2 ft. x 2 ft. refractory-lined kiln allows time resolved characterization of contaminant evolution and destruction. Continuous thermal and exhaust concentration measurements are used to characterize the fate of the solid charge as a function of residence time within the kiln. Overall destruction efficiency can be measured by subsequent analysis of the solid phase.
The initial performance of this facility has been demonstrated by studying the combustion of waste zirconium metal and by characterizing the thermal clean up of solid sorbent contaminated with toluene. The rotary kiln simulator has been shown suitable for investigation of parameters such as amount of charge, contaminant loading, rotation speed, temperature, excess oxygen, and particle size.
The Combustion of Waste Zirconium Sponge in a Rotary Kiln Simulator
Lemieux, P.M. and Pershing, D.W.
Submitted to Metals, 1987. Funded by Westinghouse and National Science Foundation/Presidential Young Investigators.
The combustion of off-grade zirconium sponge in a rotary kiln environment is described. The purpose of these experiments was to determine the suitability of rotary kiln incineration for the disposal of zirconium wastes, and to determine the design parameters and optimum operating conditions for a zirconium burning rotary kiln. In the rotary kiln simulator, the experiments are done in a batch mode, simulating a control volume of solids moving down the length of a full-scale rotary kiln, and exchanging time for distance as the independent variable. Parametric studies investigating the effect of oxygen concentration, charge size, rotational velocity, particle size and temperature on the burning rate have been completed. The burning rate appears to be controlled by intra- and interparticle diffusion, thus the rate at which the product layer is abraded off and the availability of O2 at the particle surface appear to strongly affect the burning rate. The burning rate is independent of charge size, weakly dependent on oxygen concentration, rotational velocity and particle size, and strongly dependent on temperature.
A Mathematical Model of Zirconium Combustion in a Rotary Kiln
Lemieux, P.M. and Pershing, D.W.
Submitted to Combustion Science & Technology, 1987. Funded by Westinghouse and National Science Foundation/Presidential Young Investigators.
Previous experimental studies have indicated that rotary kilns may be suitable combustion systems to incinerate small quantities of off grade zirconium sponge produced during the manufacturing of zirconium for the nuclear industry. This paper describes a mathematical model of zirconium sponge combustion in a rotary kiln environment and specifically examines the use of the bed submodel to analyze detailed zirconium combustion data obtained previously in a rotary kiln simulator.
The results of this analysis indicated that the experimentally observed burning rates could be predicted within 25% based on available transport correlations and current understanding of zirconium combustion, without any adjustment of the physical parameters in the model both the experimental results and the model predictions indicated that the primary combustion parameters are the bulk oxygen concentration within the kiln and the local kiln bed temperature. Charge size was found to be less significant.
A detailed analysis of the theoretical predictions indicates that the zirconium sponge oxidation rate is controlled by three sequential processes (the convection of oxygen from the bulk gas to the top of the bed, the diffusion of oxygen through the bed to the particle surface, and the diffusion of oxygen through previously formed zirconium dioxide product to the unreacted zirconium metal). Under conditions typical of commercial rotary kiln operation all three of these resistances appear to be significant. Both the experimental data and the model suggest that the intrinsic chemical kinetics are fast and not controlling except during the first few minutes after the zirconium is charged. The model assumes that the zirconium oxide product layer increases until it reaches a maximum value after which it remains constant due to continuous formation and abrasion.
Lemieux, PM
1989
Experimental and Theoretical Studies on the Combustion of Waste Zirconium Sponge in a Rotary Kiln Simulator
Lemieux, P.M.; Silcox, G.D. and Pershing, D.W.
Waste Management, 9:125-137, 1989. Funded by Westinghouse Corp.
Previous experimental studies have indicated that rotary kilns may be suitable combustion systems to incinerate small quantities of off grade zirconium sponge produced during the manufacturing of zirconium for the nuclear industry. This paper describes a mathematical model of zirconium sponge combustion in a rotary kiln environment and specifically examines the use of the bed submodel to analyze detailed zirconium combustion data obtained previously in a rotary kiln simulator. The results of this analysis indicated that the experimentally observed burning rates could be predicted within 25% based on available transport correlations and current understanding of zirconium combustion. Without any adjustment of the physical parameters in the model, both the experimental results and the model predictions indicated that the primary combustion parameters are the bulk oxygen concentration within the kin and the local kiln bed temperature. Charge size was found to be less significant. A detailed analysis of the theoretical predictions indicates that the zirconium sponge oxidation rate is controlled by three sequential processes (the convection of oxygen from the bulk gas to the top of the bed, the diffusion of oxygen through the bed to the particle surface, and the diffusion of oxygen through previously formed zirconium dioxide product to the unreacted zirconium metal). Under conditions typical of commercial rotary kiln operation all three of these resistances appear to be significant. Both the experimental data and the model suggest that intrinsic chemical kinetics are fast and not controlling except during the first few minutes after the zirconium is charges. The model assumes that the zirconium oxide product layer increases until it reaches a maximum value after which it remains constant due to continuous formation and abrasion.
1987
The Design and Construction of a Rotary Kiln Simulator for Use in Studying the Incineration of Hazardous Waste
Lemieux, P.M. and Pershing, D.W.
Submitted to Review of Scientific Instrument, 1987. Funded by Westinghouse and National Science Foundation/Presidential Young Investigators.
Rotary kiln systems are widely used in industrial applications to transfer energy from high temperature flames to irregular solids. Recently these systems have been shown to be suitable for the incineration of hazardous solid waste materials and the thermal treatment of contaminated soils. Destruction and removal efficiencies in excess of 99.99% have been reported for hazardous species, but the rate controlling steps of the incineration process are not well understood.
This paper describes the design, construction and operation of a laboratory scale simulator that was developed to investigate the fundamentals of hazardous incineration in a rotary kiln environment. This 2 ft. x 2 ft. refractory-lined kiln allows time resolved characterization of contaminant evolution and destruction. Continuous thermal and exhaust concentration measurements are used to characterize the fate of the solid charge as a function of residence time within the kiln. Overall destruction efficiency can be measured by subsequent analysis of the solid phase.
The initial performance of this facility has been demonstrated by studying the combustion of waste zirconium metal and by characterizing the thermal clean up of solid sorbent contaminated with toluene. The rotary kiln simulator has been shown suitable for investigation of parameters such as amount of charge, contaminant loading, rotation speed, temperature, excess oxygen, and particle size.
The Combustion of Waste Zirconium Sponge in a Rotary Kiln Simulator
Lemieux, P.M. and Pershing, D.W.
Submitted to Metals, 1987. Funded by Westinghouse and National Science Foundation/Presidential Young Investigators.
The combustion of off-grade zirconium sponge in a rotary kiln environment is described. The purpose of these experiments was to determine the suitability of rotary kiln incineration for the disposal of zirconium wastes, and to determine the design parameters and optimum operating conditions for a zirconium burning rotary kiln. In the rotary kiln simulator, the experiments are done in a batch mode, simulating a control volume of solids moving down the length of a full-scale rotary kiln, and exchanging time for distance as the independent variable. Parametric studies investigating the effect of oxygen concentration, charge size, rotational velocity, particle size and temperature on the burning rate have been completed. The burning rate appears to be controlled by intra- and interparticle diffusion, thus the rate at which the product layer is abraded off and the availability of O2 at the particle surface appear to strongly affect the burning rate. The burning rate is independent of charge size, weakly dependent on oxygen concentration, rotational velocity and particle size, and strongly dependent on temperature.
A Mathematical Model of Zirconium Combustion in a Rotary Kiln
Lemieux, P.M. and Pershing, D.W.
Submitted to Combustion Science & Technology, 1987. Funded by Westinghouse and National Science Foundation/Presidential Young Investigators.
Previous experimental studies have indicated that rotary kilns may be suitable combustion systems to incinerate small quantities of off grade zirconium sponge produced during the manufacturing of zirconium for the nuclear industry. This paper describes a mathematical model of zirconium sponge combustion in a rotary kiln environment and specifically examines the use of the bed submodel to analyze detailed zirconium combustion data obtained previously in a rotary kiln simulator.
The results of this analysis indicated that the experimentally observed burning rates could be predicted within 25% based on available transport correlations and current understanding of zirconium combustion, without any adjustment of the physical parameters in the model both the experimental results and the model predictions indicated that the primary combustion parameters are the bulk oxygen concentration within the kiln and the local kiln bed temperature. Charge size was found to be less significant.
A detailed analysis of the theoretical predictions indicates that the zirconium sponge oxidation rate is controlled by three sequential processes (the convection of oxygen from the bulk gas to the top of the bed, the diffusion of oxygen through the bed to the particle surface, and the diffusion of oxygen through previously formed zirconium dioxide product to the unreacted zirconium metal). Under conditions typical of commercial rotary kiln operation all three of these resistances appear to be significant. Both the experimental data and the model suggest that the intrinsic chemical kinetics are fast and not controlling except during the first few minutes after the zirconium is charged. The model assumes that the zirconium oxide product layer increases until it reaches a maximum value after which it remains constant due to continuous formation and abrasion.