Cundy, VA
1992
The Desorption of Toluene from a Montmorillonite Clay Adsorbent in a Rotary Kiln Environment
Owens, W.D.; Silcox, G.D.; Lighty, J.S.; Deng, X.-X.; Pershing, D.W.; Cundy, V.A.; Leger, C.B. and Jakway, A.J.
Journal of Air Waste Management Assoc., 42:681-690, 1992. Funded by US Environmental Protection Agency, Gas Research Institute and ACERC.
The vaporization of toluene from pre-dried, 6mm montmorillonite clay particles was studied in a 130 kW pilot-scale rotary kiln with inside dimensions of 0.61 by 0.61 meters. Vaporization rates were obtained with a toluene weight fraction of 0.25 percent as a function of kiln fill fractions from 3 to 8 percent, rotation rates from 0.1 to 0.9 rpm, and kiln wall temperatures from 189 to 793ºC. Toluene desorption rates were obtained from gas-phase measurements and interpreted using a desorption model that incorporates the slumping frequency of the solids. Fill fraction of the kiln, binary gas diffusion in the bed, and particle desorption using an Arrhenius-type expression that is a function of bed temperature and average bed concentration. The model included three adjustable desorption parameters which were obtained by fitting the experimental data with a least squares technique. Solid and kiln-wall temperatures were continuously recorded and used by the model to perform toluene desorption predictions. The model was successful at predicting the effects of fill fraction and rotation rate over a range of temperatures. It was shown that an increase in kiln temperature and rotation rate increased toluene desorption rates. A decrease in kiln fill fraction showed an increase n desorption rate. Desorption predictions were performed using both predicted and measured temperature profiles. In addition, the model was used to perform sensitivity tests examine the relative importance of bed diffusion and particle desorption resistances. A methodology for predicting full-scale performance was developed. A full-scale, rotary-kiln heat-transfer model was used to estimate the bed thermal profile. This profile was then utilized by the model tp predict toluene desorption at full-scale.
1991
Rotary Kiln Incineration: Comparison and Scaling of Field-Scale Contaminant Evolution Rates from Sorbent Beds
Lester, T.W.; Cundy, V.A.; Sterling, A.M.; Montestruc, A.N.; Jakway, A.J.; Lu, C.; Leger, C.B.; Pershing D.W.; Lighty, J.S.; Silcox, G.D. and Owens, W.D.
Environmental Science Technology, 25:1142-1152, 1991. Funded by Environmental Protection Agency, Louisiana State University/Hazardous Waste Research Center and ACERC.
A comparison is made, for the first time, between the evolution of hydrocarbons from clay sorbent beds in a field-scale rotary kiln incinerator and in a pilot-scale rotary kiln simulator. To relate the data from the different sized units, due allowance is made for bed dynamical similitude, bed geometrical factors, and bed heat-up. To minimize the effects of disturbances caused by foreign matter in the field scale bed and differences in loading techniques, the rate of evolution is characterized by an "evolution interval" defined as the time required for the middle 80% of the ultimate containment evolution to occur. A comparison of evolution intervals with reciprocal bed temperature reveals that the data are consistent with an analysis that assumes a uniform bed temperature (at any instant of time) and desorption controlled evolution rate. Furthermore, the evolution intervals scale inversely with a modified Froude Number, which characterizes bed dynamics. The success in comparing field and simulator results indicates that pilot scale rotary kilns may be used to simulate certain features of industrial-scale units if dynamical, geometrical and thermal parameters are matched appropriately.
Thermal Analysis of Rotary Kiln Incineration: Comparison of Theory and Experiment
Owens, W.D.; Silcox, G.D.; Lighty, J.S.; Deng, X.-X.; Pershing D.W.; Cundy, V.A.; Leger, C.B. and Jakway, A.J.
Combustion and Flame, 86:101-114, 1991. Funded by Gas Research Institute, ACERC and Louisiana State University/Hazardous Waste Research Center.
A comprehensive heat-transfer model and associated simplified scaling laws are developed and verified using a pilot-scale, directly fired rotary kiln with a slumping bed of dry or wet, 6-mm clay sorbent particles. The kiln operating conditions examined include: rotation rate (0.1 to 0.9 rpm), percent fill fraction (3-8), feed moisture content (0-20 wt.%), and inner-wall temperature (190º to 790ºC). The model is used to determine the relative importance of several heat-transfer mechanisms including radiation, gas-to-solid convection, and wall-to-solid convection. Simple scaling laws are also developed for water vaporization. Generally good agreement is obtained between theory and experiment without adjusting any model parameters. Further, the simplified scaling laws provide a reasonable estimate of the pilot scale performance. The key conclusions of this study for kilns at the conditions examined are (1) water exerts a profound effect on the solids thermal profile, (2) simple geometrical scaling is not sufficient, (3) the assumption of a well mixed (radially isothermal) solids bed for the heat transfer analysis is appropriate, (4) a dimensionless group, which is a function of temperature, can be defined giving the relative importance of radiative and convective modes of heat transfer, and (5) moisture vaporization rates can be roughly approximated by assuming that the water vaporizes at the boiling point at a rate controlled by the rate of heat transfer to the bed. The implications of the scaling laws for scale-up and kiln design are also examined.
1990
Fundamentals for the Thermal Remediation of Contaminated Soils - Particle and Bed Desorption Models
Lighty, J.S.; Silcox, G.D.; Pershing, D.W.; Cundy, V.A. and Linz, D.G.
Environmental Science & Technology, 24 (5), 750-757, 1990. Funded by the Gas Research Institute, Dave Linz, Project Manager, NSF - Presidential Young Investigator Program, ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, and US Department of Energy.
A major research effort has been initiated to characterize the rate-controlling processes associated with the evolution of hazardous materials from soils. A threefold experimental approach is being used in conjunction with computer modeling to analyze thermal desorption of contaminants. Phenomena occurring both inside particles (intraparticle) and with a bed of particles (interparticle) were studied.
The results obtained suggest that the most important process variable are local thermal environment and gas-phase contaminant concentration because the adsorption equilibrium characteristics of the contaminant/soil pair control the desorption of contaminant from a particle at a given temperature. A mass-transfer/desorption model, which assumes gas/solid equilibrium at all points and time, is proposed and the model was found to predict the measured temperature dependence.
Rotary Kiln Incineration: Comparison of Field and Pilot Scale Measurements of Contaminant Evolution Rates from Sorbent Beds
Lester, T.W.; Cundy, V.A.; Sterling, A.M.; Montestruc, A.N.; Jakway, A.J.; Leger, C.B.; Pershing D.W.; Lighty, J.S.; Silcox, G.D. and Owens, W.D.
Environmental Science Technology, 1990. Funded by Environmental Protection Agency and Louisiana State University Hazardous Waste Research Center.
A comparison is made, for the first time, between the evolution of hydrocarbons from sorbent beds in an industrial rotary kiln incinerator and in a laboratory scale rotary kiln simulator. To relate the data from the different sized units, due allowance is made for bed dynamical similitude, bed geometrical factors, and bed heat-up. To minimize the effects of disturbances caused by foreign matter in the full scale bed and differences in loading techniques, the rate of evolution is characterized by an "evolution interval," that is defined as the time required for total hydrocarbon evolution at the maximum evolution rate. A comparison of evolution intervals with reciprocal bed temperature reveals that the data are consistent with an analysis that assumes a uniform bed temperature (at any instant of time) and desorption control of the evolution rate. Furthermore, the evolution intervals scale inversely with modified Froude Number, which characterizes bed dynamics. The success in comparing field and simulator results indicates that pilot scale rotary kilns may be used to simulate certain features of industrial scale units if appropriate care is taken in matching dynamical, geometrical and thermal parameters.
Thermal Analysis of Rotary Kiln Incineration: Comparison of Theory and Experiment
Owens, W.D.; Silcox, G.D.; Lighty, J.S.; Deng, X.-X.; Pershing D.W.; Cundy, V.A.; Leger, C.B. and Jakway, A.J.
Combustion and Flame, 1990. Funded by Gas Research Institute, ACERC and Louisiana State University Hazardous Waste Research Center.
A comprehensive heat-transfer model and associated simplified scaling laws are developed and verified using a pilot-scale, directly-fired rotary kiln with a slumping bed of dry or wet, 2 mm clay sorbent particles. The kiln operating conditions examined include: rotation rate (0.1 to 0.9 rpm), percent fill fraction (3 to 8), feed moisture content (0 to 20 wt. percent), and inner-wall temperature (190 to 790º). The model is used to determine the relative importance of several heat-transfer mechanisms including radiation, gas-to-solid convection, and wall-to-solid convection. Simple scaling laws are also developed for water vaporization. Generally good agreement is obtained between theory and experiment without adjusting any model parameters. Further, the simplified scaling laws provide a reasonable estimate of the pilot scale performance.
The key conclusions of this study for kilns at the conditions examined are: (1) water exerts a profound effect on the solids thermal profile, (2) simple geometrical scaling is not sufficient, (3) the assumption of a well mixed (radially isothermal) solids bed for the heat transfer analysis is appropriate, (4) a dimensionless group, which is a function of temperature, can be defined giving the relative importance of radiative and convective modes of heat transfer, and (5) moisture vaporization rates can be roughly approximated by assuming that the water vaporized at the boiling point at a rate controlled by the rate of heat transfer to the bed. The implications of the scaling laws for scale-up and kiln design are also examined.
1989
Fundamental Experiments on Thermal Desorption of Contaminants from Soils
Lighty, J.S.; Silcox, G.D.; Pershing, D.W.; Cundy, V.A. and Linz, D.G.
Environmental Progress, 8 (1), 1989. Funded by the Gas Research Institute, Dave Linz, Project Manager, National Science Foundation - Presidential Young Investigator Program, ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, and US Department of Energy.
The goals of this research are to develop an understanding of the transport phenomena that occur during the desorption of contaminants from soil and to obtain rate information. This information can then be used to develop a model to predict the performance of full-scale thermal treatment systems for optimization and cost reduction.
Rotary Kiln Incineration--Combustion Chamber Dynamics
Cundy, V.A.; Lester, T.W.; Leger, C.B.; Miller, G.; Montestruc, A.N.; Acharya, S.; Sterling, A.M.; Pershing, D.W.; Lighty, J.S.; Silcox, G.D. and Owens, W.D.
Journal of Hazardous Materials, 22, 195-219,1989. Funded by US Environmental Proctection Agency and ACERC (National Science Foundation and Associates and Affiliates).
A multifaceted experimental and theoretical program aimed at understanding rotary kiln performance is underway. The overall program involves university, industry, and government participation and is broken into distinct sub-programs. This paper discusses in some detail the research effort performed to date in two of the sub-programs: Full-scale in situ sampling and kiln-simulator experimentation. Full-scale in situ measurements are obtained from the Louisiana Division rotary kiln facility of Dow Chemical USA, located in Plaquemine, Louisiana. Summary results obtained from controlled experiments that were performed during continuous processing of carbon tetrachloride and preliminary results obtained during batch mode processing of toluene-laden sorbent packs are presented. Kiln-simulator data are obtained by using the facilities of the Chemical Engineering Department at the University of Utah. Recent kiln-simulator work, conducted in support of the full-scale measurements sub-program, has aided in providing an understanding of the results that have been obtained at the full-scale. Modeling efforts, conducted at Louisiana State University and the University of Utah, have concentrated on the development of realistic, fluid-flow and heat-transfer models, near-term chlorinated kinetic models and bed mass-transfer models to be incorporated into a global three-dimensional kiln-simulator model. The paper concludes with an overview of these modeling efforts.
An In-Depth Study of Incineration - Rotary Kiln Performance Characterization
Cundy, V.A.; Lester, T.W.; Conway, L.R.; Jakway, A.J.; Leger, C.B.; Montestruc, A.N.; Acharya, S.; Sterling, A.M.; Owens, W.D.; Lighty, J.S.; Pershing, D.W. and Silcox, G.D.
Louisiana State University/Hazardous Waste Research Center SAC Review Meeting, Baton Rouge, Louisiana, 1989. Funded by Louisiana State University/Hazardous Waste Research Center (Supported by US Environmental Protection Agency).
A comprehensive study aimed at understanding rotary kiln performance is underway. The program is led by personnel from Louisiana State University. Bench and pilot-scale facilities at the University of Utah are available for use in solids desorption studies. Full-scale in situ measurements are obtained from the Louisiana Division rotary kiln facility of Dow Chemical USA, located in Plaquemine, Louisiana. This paper presents a summary of the project providing some detail of the work that has been accomplished from 1 January through 31 August 1989.
The Effect of Fuel Nitrogen on NOx Emissions From a Rotary-Kiln Incinerator
Lighty, J.S.; Gordon, D.L.; Pershing, D.W.; Owens, W.D.; Cundy, V.A. and Leger, C.B.
Stationary NOx Symposium, San Francisco, California, 1989. Funded by Louisiana State University/Hazardous Waste Research Center, and ACERC (National Science Foundation and Associates and Affiliates).
While fuel NOx formation has been extensively studied for coal combustion, little information is available on NOx formation for nitrogenous waste constituents. These wastes, usually destroyed in hazardous-waste incinerators, are prevalent and exist as solids (plastics, nylongs) or liquids (dyes, process waste).
Results are presented from studies conducted in a scaled, batch rotary-kiln simulator. Constituent parameters, i.e. constituent type and percent fuel nitrogen, were studied at 730ºC. Sorbent was contaminated with a variety of constituents ranging in concentrations from 0.5% to 3.0% nitrogen by weight (for 681 g charge).
NOx exhaust-gas concentrations ranged from 60-80 ppm for a base run (no fuel nitrogen) to 200-1750 ppm for a nitrogenous waste. Results inducated that, at higher concentrations, more NOx was formed, accompanied by an increase in temperature. Higher concentrations also resulted in reduced percent conversions of fuel nitrogen to NOx. Evolution for different constituents, given the same concentration, varied; aniline formed more NOx than pyridine, followed by ethylenediamine.
Fundamentals for the Thermal Remediation of Contaminated Soils - Particle and Bed Desorption Models
Lighty, J.S.; Silcox, G.D.; Pershing, D.W.; Cundy, V.A. and Linz, D.G.
Accepted for publication in Environ. Science Tech., 1989. Funded by the Gas Research Institute, Dave Linz, Project Manager, National Science Foundation/Presidential Young Investigators, ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, and US Department of Energy.
A major research effort has been initiated to characterize the rate-controlling processes associated with the evolution of hazardous materials from soils. A threefold experimental approach is being used in conjunction with computer modeling to analyze thermal desorption of contaminants. Phenomena occurring both inside particles (intraparticle) and with a bed of particles (interparticle) were studied.
The results obtained suggest that the most important process variables are local thermal environment and gas-phase contaminant concentration because the adsorption equilibrium characteristics of the contaminant/soil pair control the desorption of contaminant from a particle at a given temperature. A mass-transfer/desorption model, which assumes gas/solid equilibrium at all points and time, is proposed and the model was found to predict the measured temperature dependence.
1988-1987
Characterization of Thermal Desorption Phenomena for the Clean-Up of Contaminated Soil
Lighty, J.S.; Pershing, D.W.; Cundy, V.A. and Linz, D.G.
Accepted for Nuclear & Chemical Waste Management, 1987. 32 pgs. Funded by ACERC (National Science Foundation and Associates and Affiliates).
The overall goal of this research is to develop an understanding of the fundamental transport phenomena associated with the evolution of hazardous materials from solids, in particular contaminated soils. At the present time, incineration is a relatively costly alternative for the clean up of contaminated soils. An understanding of the mass transfer and heat transfer limitations might lead to a more economical option, where the contaminants are desorbed from the soil at lower temperatures in a primary combustor and then a secondary, high temperature combustor (afterburner) decomposes the hazardous off-gases. This work is aimed at providing fundamental rate information which will be used to model thermal desorption of contaminants from soils under a variety of thermal conditions, soil properties and contaminants.
The experimental approach is threefold. First, a bench scale particle characterization reactor (PCR) has been developed and is being used to characterize intraparticle transport under conditions where the bulk concentration and temperature at the particle surface are known. Following these studies, a packed-bed reactor will be used to examine interparticle transport within a well-characterized bed of particles. In the third portion of the work, a 73 kW pilot-scale rotary kiln will be used to obtain time resolved measurements of trace species evolution. This paper reports recent PCR results that indicate that soil properties, type of contaminant, and temperature are important in desorption of contaminants from soil particles.
The overall goal of this research is to develop an understanding of the fundamental transport phenomena associated with the evolution of hazardous materials from solids, in particular contaminated soils. At the present time, incineration is a relatively costly alternative for the clean up of contaminated soils and it may render the soil inert. A more economical option is to desorb the contaminants from the soil at lower temperatures and then use high temperature incineration to decompose the hazardous off-gases. This work is aimed at providing fundamental rate information which may be used to model the thermal desorption of contaminants from soils under a wide variety of thermal conditions.
The experimental approach is three-fold. First, a bench-scale particle characterization reactor (PCR) has been developed and is being used to characterize intraparticle transport under conditions where the bulk concentration and temperature at the particle surface are known. Following these studies, a packed bed reactor will be used to examine interparticle transport within a well-characterized bed of particles. In the third portion of the work, a 73,000 Watt pilot-scale rotary kiln will be used to reports recent PCR and kiln results; it does not address the packed bed reactor studies since they are just being initiated. The PCR results indicate that soil pore structure is important in desorption of contaminants from soil particles and that the desorption/diffusion step is probably a controlling mechanism.
Rotary Kiln Incineration I: An In-Depth Study - Liquid Injection
Cundy, V.A.; Lester, T.W.; Morse, J.S.; Montestruc, A.N.; Leger, C.B.; Acharya, S.; Sterling, A.M. and Pershing, D.W.
Submitted to Journal of the Air Pollution Control Association, 1988. 39 pgs. Funded by Environmental Protection Agency.
A multifaceted experimental and theoretical program directed toward the understanding of rotary kiln performance is underway. Following a general overview of the program, we describe in more detail the program components including: In-situ measurements from an industrial-scale rotary kiln located at the Louisiana Division of Dow Chemical USA in Plaquemine, Louisiana; laboratory-scale desorption characterization and kiln-simulator studies; and incinerator modeling efforts. Using water-cooled probes, hot-zone samples have been obtained from both the full-scale rotary kiln and the afterburner and have been analyzed subsequently using GC and/or GC/MS techniques. We report on these preliminary measurements in some detail.
Rotary Kiln Incineration II: Laboratory Scale Desorption and Kiln Simulator Studies - Solids
Cundy, V.A.; Lester, T.W.; Morse, J.S.; Montestruc, A.N.; Leger, C.B.; Acharya, S.; Sterling, A.M. and Pershing, D.W.
Submitted to Journal of the Air Pollution Control Association, 1988. 28 pgs. Funded by Gas Research Institute, ACERC (National Science Foundation and Associates and Affiliates), and National Science Foundation/Presidential Young Investigators.
With landfill costs increasing and regulations on landfilling becoming more stringent, alternatives to conventional hazardous waste treatment strategies are becoming more desirable. Incineration is presently a permanent, proven solution for the disposal of most organic contaminants, but also a costly one, especially in the case of solids that require some auxiliary fuel. The goal of this research is to develop an understanding of the phenomena associated with the evolution of contaminants from solids in the primary combustor of an incineration system. A four-fold approach is being used. First, a bench scale Particle Characterization Reactor was developed to study the transport phenomena on a particle basis, where the controlling processes are mainly intraparticle. Second, a Bed Characterization Reactor was built to examine the controlling transport phenomena within a bed of particles, where the processes are primarily interparticle. The results of these studies can be applied to any primary combustor. A pilot-scale rotary kiln was developed to study the evolution of contaminants from solids within a realistic temperature and rotation environment. Finally, in-situ measurements are being obtained from a full-scale rotary-kiln.
This paper describes results obtained in a study using a commercial sorbent contaminated with toluene. The data are from the Particle Characterization Reactor and the Rotary-Kiln Simulator. The results show that the method of contamination and charge size does not have a large effect on desorption, while temperature and contaminant concentration are important parameters in the evolution of contaminants in a rotary kiln.
Rotary Kiln Incineration III: An In-depth Study - Full-Scale Incineration of Carbon Tetrachloride
Cundy, V.A.; Lester, T.W.; Morse, J.S.; Montestruc, A.N.; Leger, C.B.; Acharya, S.; Sterling, A.M. and Pershing, D.W.
Submitted to Journal of the Air Pollution Control Association, 1988. 31 pgs. Funded by Environmental Protection Agency.
Temperature and stable species concentration data are presented from various locations within a full-scale rotary kiln firing natural gas/carbon tetrachloride/air. The data are being collected as part of a cooperative program involving university, industrial and government participation. The overall goal of the program is to develop a rudimentary understanding of and a predictive capability for rotary kiln and afterburner performance as influenced by basic design and operation parameters. The data clearly demonstrates that severe non-uniformities exist at the kiln exit under certain operating conditions. Even so, the data further indicate that high destruction efficiencies were achieved through adequate secondary combustion processing. The data further show that flow perturbations from within the kiln can persist well into the afterburner section and even into the stack.
Transport Fundamentals for the Thermal Remediation of Contaminated Soils
Lighty, J.S.; Silcox, G.D.; Pershing, D.W.; Cundy, V.A. and Linz, D.G.
Submitted for Review to AIChE Journal, 1988. 23 pgs. Funded by Gas Research Institute, ACERC (National Science Foundation and Associates and Affiliates), and National Science Foundation/Presidential Young Investigators.
A major research effort has been initiated to characterize the transport phenomena associated with the evolution of hazardous materials from contaminated soils. A threefold experimental approach is being used in conjunction with computer modeling to analyze thermal desorption of contaminants from soils under a variety of experimental conditions. First, a particle-characterization reactor (PCR) is being employed to characterize intraparticle transport under conditions where the bulk concentration and temperature at the particle surface are known. Secondly, a packed-bed reactor is being used to examine interparticle transport within a bed of particles. In the third portion of the work, a 73 kW pilot-scale rotary kiln is providing time-resolved measurements of the species evolution. The results from the PCR experiments and modeling are reported in this manuscript.
The PCR experimental results obtained suggest that the most important process variable is local thermal environment and that the absorption characteristics of the contaminant/soil pair are important in the desorption process. The adsorption characteristics are a function of local temperature, thus accounting for the steep dependence of the cleanup efficiency of a soil on temperature. In addition, the adsorption characteristics are influenced by soil type and moisture; it has been found that these parameters also effect desorption of contaminants. A mass-transfer model, which assumes gas/solid equilibrium at all points and times, is proposed and the model predictions were found to exhibit temperature dependence similar to the data.
The Clean Up of Contaminated Soil By Thermal Desorption
Lighty, J.S.; Pershing, D.W.; Cundy, V.A.; Groves, F.R. Jr. and Linz, D.G.
Proc. 2nd Int. Conf. on New Frontiers in Hazardous Waste Management, 1987, NUS, Pittsburgh, PA. 10 pgs. Funded by Gas Research Institute, National Science Foundation, and ACERC (National Science Foundation and Associates and Affiliates).
The overall goal of this research is to develop an understanding of the fundamental transport phenomena associated with the evolution of hazardous materials from solids, in particular, contaminated soils. At the present time, incineration is a relatively costly alternative for the clean up of contaminated soils and it may render the soil inert. A more economical option is to desorb the contaminants from the soil at lower temperatures and then use high temperature incineration to decompose the hazardous off-gases. This work is aimed at providing fundamental rate information which may be used to model the thermal desorption of contaminants from soils under a wide variety of thermal conditions.
The experimental approach is threefold First, a bench-scale particle characterization reactor (PCR) has been developed and is being used to characterize intraparticle transport under conditions where the bulk concentration and temperature at the particle surface are known. Following these studies, a packed bed reactor will be used to examine interparticle transport within a well-characterized bed of particles. In the third portion of the work, a 73,000 Watt pilot-scale rotary kiln will be used to obtain time resolved measurements of trace species evolution. This paper reports recent PCR and kiln results; it does not address the packed bed reactor studies since they are just being initiated. The PCR results indicate that soil pore structure is important in desorption of contaminants from soil particles and that the desorption/diffusion step is probably a controlling mechanism.
Fundamentals of Hazardous Solid Waste Incineration in a Rotary Kiln Environment
Lighty, J.S.; Silcox, G.D.; Britt, R.; Owens, W.D.; Pershing, D.W. and Cundy, V.A.
Proc. AFRC Int'l. Symposium on Waste Incineration, 1987, Palm Springs. Funded by Environmental Protection Agency.
With landfill costs increasing and regulations on landfilling becoming more stringent, alternatives to conventional hazardous waste treatment strategies are becoming more desirable. Incineration is presently a permanent, proven solution for the disposal of most organic contaminants, but also a costly one, especially in the case of solids that require some auxiliary fuel. The goal of this research is to develop an understanding of the phenomena associated with the evolution of contaminants from solids in the primary combustor of an incineration system. A threefold approach has been used. First, a bench-scale Particle Characterization Reactor was developed to study the transport phenomena on a particle basis, where the controlling processes are mainly intraparticle. Second, a Bed Characterization Reactor was built to examine the controlling transport phenomena within a bed of particles, where the processes are primarily interparticle. The results of these studies can be applied to any primary combustor. Finally a pilot-scale rotary kiln was developed to study the evolution of contaminants from solids within a realistic temperature and rotation environment.
This paper describes results obtained in a study using a commercial sorbent contaminated with toluene. The data are from the Particle Characterization Reactor and the Rotary-Kiln Simulator. The results show that the method of contamination and charge size does not have a large effect on desorption, while temperature and contaminant concentration are important parameters in the evolution of contaminants in a rotary kiln. Preliminary modeling efforts for the kiln are also discussed.
Cundy, VA
1992
The Desorption of Toluene from a Montmorillonite Clay Adsorbent in a Rotary Kiln Environment
Owens, W.D.; Silcox, G.D.; Lighty, J.S.; Deng, X.-X.; Pershing, D.W.; Cundy, V.A.; Leger, C.B. and Jakway, A.J.
Journal of Air Waste Management Assoc., 42:681-690, 1992. Funded by US Environmental Protection Agency, Gas Research Institute and ACERC.
The vaporization of toluene from pre-dried, 6mm montmorillonite clay particles was studied in a 130 kW pilot-scale rotary kiln with inside dimensions of 0.61 by 0.61 meters. Vaporization rates were obtained with a toluene weight fraction of 0.25 percent as a function of kiln fill fractions from 3 to 8 percent, rotation rates from 0.1 to 0.9 rpm, and kiln wall temperatures from 189 to 793ºC. Toluene desorption rates were obtained from gas-phase measurements and interpreted using a desorption model that incorporates the slumping frequency of the solids. Fill fraction of the kiln, binary gas diffusion in the bed, and particle desorption using an Arrhenius-type expression that is a function of bed temperature and average bed concentration. The model included three adjustable desorption parameters which were obtained by fitting the experimental data with a least squares technique. Solid and kiln-wall temperatures were continuously recorded and used by the model to perform toluene desorption predictions. The model was successful at predicting the effects of fill fraction and rotation rate over a range of temperatures. It was shown that an increase in kiln temperature and rotation rate increased toluene desorption rates. A decrease in kiln fill fraction showed an increase n desorption rate. Desorption predictions were performed using both predicted and measured temperature profiles. In addition, the model was used to perform sensitivity tests examine the relative importance of bed diffusion and particle desorption resistances. A methodology for predicting full-scale performance was developed. A full-scale, rotary-kiln heat-transfer model was used to estimate the bed thermal profile. This profile was then utilized by the model tp predict toluene desorption at full-scale.
1991
Rotary Kiln Incineration: Comparison and Scaling of Field-Scale Contaminant Evolution Rates from Sorbent Beds
Lester, T.W.; Cundy, V.A.; Sterling, A.M.; Montestruc, A.N.; Jakway, A.J.; Lu, C.; Leger, C.B.; Pershing D.W.; Lighty, J.S.; Silcox, G.D. and Owens, W.D.
Environmental Science Technology, 25:1142-1152, 1991. Funded by Environmental Protection Agency, Louisiana State University/Hazardous Waste Research Center and ACERC.
A comparison is made, for the first time, between the evolution of hydrocarbons from clay sorbent beds in a field-scale rotary kiln incinerator and in a pilot-scale rotary kiln simulator. To relate the data from the different sized units, due allowance is made for bed dynamical similitude, bed geometrical factors, and bed heat-up. To minimize the effects of disturbances caused by foreign matter in the field scale bed and differences in loading techniques, the rate of evolution is characterized by an "evolution interval" defined as the time required for the middle 80% of the ultimate containment evolution to occur. A comparison of evolution intervals with reciprocal bed temperature reveals that the data are consistent with an analysis that assumes a uniform bed temperature (at any instant of time) and desorption controlled evolution rate. Furthermore, the evolution intervals scale inversely with a modified Froude Number, which characterizes bed dynamics. The success in comparing field and simulator results indicates that pilot scale rotary kilns may be used to simulate certain features of industrial-scale units if dynamical, geometrical and thermal parameters are matched appropriately.
Thermal Analysis of Rotary Kiln Incineration: Comparison of Theory and Experiment
Owens, W.D.; Silcox, G.D.; Lighty, J.S.; Deng, X.-X.; Pershing D.W.; Cundy, V.A.; Leger, C.B. and Jakway, A.J.
Combustion and Flame, 86:101-114, 1991. Funded by Gas Research Institute, ACERC and Louisiana State University/Hazardous Waste Research Center.
A comprehensive heat-transfer model and associated simplified scaling laws are developed and verified using a pilot-scale, directly fired rotary kiln with a slumping bed of dry or wet, 6-mm clay sorbent particles. The kiln operating conditions examined include: rotation rate (0.1 to 0.9 rpm), percent fill fraction (3-8), feed moisture content (0-20 wt.%), and inner-wall temperature (190º to 790ºC). The model is used to determine the relative importance of several heat-transfer mechanisms including radiation, gas-to-solid convection, and wall-to-solid convection. Simple scaling laws are also developed for water vaporization. Generally good agreement is obtained between theory and experiment without adjusting any model parameters. Further, the simplified scaling laws provide a reasonable estimate of the pilot scale performance. The key conclusions of this study for kilns at the conditions examined are (1) water exerts a profound effect on the solids thermal profile, (2) simple geometrical scaling is not sufficient, (3) the assumption of a well mixed (radially isothermal) solids bed for the heat transfer analysis is appropriate, (4) a dimensionless group, which is a function of temperature, can be defined giving the relative importance of radiative and convective modes of heat transfer, and (5) moisture vaporization rates can be roughly approximated by assuming that the water vaporizes at the boiling point at a rate controlled by the rate of heat transfer to the bed. The implications of the scaling laws for scale-up and kiln design are also examined.
1990
Fundamentals for the Thermal Remediation of Contaminated Soils - Particle and Bed Desorption Models
Lighty, J.S.; Silcox, G.D.; Pershing, D.W.; Cundy, V.A. and Linz, D.G.
Environmental Science & Technology, 24 (5), 750-757, 1990. Funded by the Gas Research Institute, Dave Linz, Project Manager, NSF - Presidential Young Investigator Program, ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, and US Department of Energy.
A major research effort has been initiated to characterize the rate-controlling processes associated with the evolution of hazardous materials from soils. A threefold experimental approach is being used in conjunction with computer modeling to analyze thermal desorption of contaminants. Phenomena occurring both inside particles (intraparticle) and with a bed of particles (interparticle) were studied.
The results obtained suggest that the most important process variable are local thermal environment and gas-phase contaminant concentration because the adsorption equilibrium characteristics of the contaminant/soil pair control the desorption of contaminant from a particle at a given temperature. A mass-transfer/desorption model, which assumes gas/solid equilibrium at all points and time, is proposed and the model was found to predict the measured temperature dependence.
Rotary Kiln Incineration: Comparison of Field and Pilot Scale Measurements of Contaminant Evolution Rates from Sorbent Beds
Lester, T.W.; Cundy, V.A.; Sterling, A.M.; Montestruc, A.N.; Jakway, A.J.; Leger, C.B.; Pershing D.W.; Lighty, J.S.; Silcox, G.D. and Owens, W.D.
Environmental Science Technology, 1990. Funded by Environmental Protection Agency and Louisiana State University Hazardous Waste Research Center.
A comparison is made, for the first time, between the evolution of hydrocarbons from sorbent beds in an industrial rotary kiln incinerator and in a laboratory scale rotary kiln simulator. To relate the data from the different sized units, due allowance is made for bed dynamical similitude, bed geometrical factors, and bed heat-up. To minimize the effects of disturbances caused by foreign matter in the full scale bed and differences in loading techniques, the rate of evolution is characterized by an "evolution interval," that is defined as the time required for total hydrocarbon evolution at the maximum evolution rate. A comparison of evolution intervals with reciprocal bed temperature reveals that the data are consistent with an analysis that assumes a uniform bed temperature (at any instant of time) and desorption control of the evolution rate. Furthermore, the evolution intervals scale inversely with modified Froude Number, which characterizes bed dynamics. The success in comparing field and simulator results indicates that pilot scale rotary kilns may be used to simulate certain features of industrial scale units if appropriate care is taken in matching dynamical, geometrical and thermal parameters.
Thermal Analysis of Rotary Kiln Incineration: Comparison of Theory and Experiment
Owens, W.D.; Silcox, G.D.; Lighty, J.S.; Deng, X.-X.; Pershing D.W.; Cundy, V.A.; Leger, C.B. and Jakway, A.J.
Combustion and Flame, 1990. Funded by Gas Research Institute, ACERC and Louisiana State University Hazardous Waste Research Center.
A comprehensive heat-transfer model and associated simplified scaling laws are developed and verified using a pilot-scale, directly-fired rotary kiln with a slumping bed of dry or wet, 2 mm clay sorbent particles. The kiln operating conditions examined include: rotation rate (0.1 to 0.9 rpm), percent fill fraction (3 to 8), feed moisture content (0 to 20 wt. percent), and inner-wall temperature (190 to 790º). The model is used to determine the relative importance of several heat-transfer mechanisms including radiation, gas-to-solid convection, and wall-to-solid convection. Simple scaling laws are also developed for water vaporization. Generally good agreement is obtained between theory and experiment without adjusting any model parameters. Further, the simplified scaling laws provide a reasonable estimate of the pilot scale performance.
The key conclusions of this study for kilns at the conditions examined are: (1) water exerts a profound effect on the solids thermal profile, (2) simple geometrical scaling is not sufficient, (3) the assumption of a well mixed (radially isothermal) solids bed for the heat transfer analysis is appropriate, (4) a dimensionless group, which is a function of temperature, can be defined giving the relative importance of radiative and convective modes of heat transfer, and (5) moisture vaporization rates can be roughly approximated by assuming that the water vaporized at the boiling point at a rate controlled by the rate of heat transfer to the bed. The implications of the scaling laws for scale-up and kiln design are also examined.
1989
Fundamental Experiments on Thermal Desorption of Contaminants from Soils
Lighty, J.S.; Silcox, G.D.; Pershing, D.W.; Cundy, V.A. and Linz, D.G.
Environmental Progress, 8 (1), 1989. Funded by the Gas Research Institute, Dave Linz, Project Manager, National Science Foundation - Presidential Young Investigator Program, ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, and US Department of Energy.
The goals of this research are to develop an understanding of the transport phenomena that occur during the desorption of contaminants from soil and to obtain rate information. This information can then be used to develop a model to predict the performance of full-scale thermal treatment systems for optimization and cost reduction.
Rotary Kiln Incineration--Combustion Chamber Dynamics
Cundy, V.A.; Lester, T.W.; Leger, C.B.; Miller, G.; Montestruc, A.N.; Acharya, S.; Sterling, A.M.; Pershing, D.W.; Lighty, J.S.; Silcox, G.D. and Owens, W.D.
Journal of Hazardous Materials, 22, 195-219,1989. Funded by US Environmental Proctection Agency and ACERC (National Science Foundation and Associates and Affiliates).
A multifaceted experimental and theoretical program aimed at understanding rotary kiln performance is underway. The overall program involves university, industry, and government participation and is broken into distinct sub-programs. This paper discusses in some detail the research effort performed to date in two of the sub-programs: Full-scale in situ sampling and kiln-simulator experimentation. Full-scale in situ measurements are obtained from the Louisiana Division rotary kiln facility of Dow Chemical USA, located in Plaquemine, Louisiana. Summary results obtained from controlled experiments that were performed during continuous processing of carbon tetrachloride and preliminary results obtained during batch mode processing of toluene-laden sorbent packs are presented. Kiln-simulator data are obtained by using the facilities of the Chemical Engineering Department at the University of Utah. Recent kiln-simulator work, conducted in support of the full-scale measurements sub-program, has aided in providing an understanding of the results that have been obtained at the full-scale. Modeling efforts, conducted at Louisiana State University and the University of Utah, have concentrated on the development of realistic, fluid-flow and heat-transfer models, near-term chlorinated kinetic models and bed mass-transfer models to be incorporated into a global three-dimensional kiln-simulator model. The paper concludes with an overview of these modeling efforts.
An In-Depth Study of Incineration - Rotary Kiln Performance Characterization
Cundy, V.A.; Lester, T.W.; Conway, L.R.; Jakway, A.J.; Leger, C.B.; Montestruc, A.N.; Acharya, S.; Sterling, A.M.; Owens, W.D.; Lighty, J.S.; Pershing, D.W. and Silcox, G.D.
Louisiana State University/Hazardous Waste Research Center SAC Review Meeting, Baton Rouge, Louisiana, 1989. Funded by Louisiana State University/Hazardous Waste Research Center (Supported by US Environmental Protection Agency).
A comprehensive study aimed at understanding rotary kiln performance is underway. The program is led by personnel from Louisiana State University. Bench and pilot-scale facilities at the University of Utah are available for use in solids desorption studies. Full-scale in situ measurements are obtained from the Louisiana Division rotary kiln facility of Dow Chemical USA, located in Plaquemine, Louisiana. This paper presents a summary of the project providing some detail of the work that has been accomplished from 1 January through 31 August 1989.
The Effect of Fuel Nitrogen on NOx Emissions From a Rotary-Kiln Incinerator
Lighty, J.S.; Gordon, D.L.; Pershing, D.W.; Owens, W.D.; Cundy, V.A. and Leger, C.B.
Stationary NOx Symposium, San Francisco, California, 1989. Funded by Louisiana State University/Hazardous Waste Research Center, and ACERC (National Science Foundation and Associates and Affiliates).
While fuel NOx formation has been extensively studied for coal combustion, little information is available on NOx formation for nitrogenous waste constituents. These wastes, usually destroyed in hazardous-waste incinerators, are prevalent and exist as solids (plastics, nylongs) or liquids (dyes, process waste).
Results are presented from studies conducted in a scaled, batch rotary-kiln simulator. Constituent parameters, i.e. constituent type and percent fuel nitrogen, were studied at 730ºC. Sorbent was contaminated with a variety of constituents ranging in concentrations from 0.5% to 3.0% nitrogen by weight (for 681 g charge).
NOx exhaust-gas concentrations ranged from 60-80 ppm for a base run (no fuel nitrogen) to 200-1750 ppm for a nitrogenous waste. Results inducated that, at higher concentrations, more NOx was formed, accompanied by an increase in temperature. Higher concentrations also resulted in reduced percent conversions of fuel nitrogen to NOx. Evolution for different constituents, given the same concentration, varied; aniline formed more NOx than pyridine, followed by ethylenediamine.
Fundamentals for the Thermal Remediation of Contaminated Soils - Particle and Bed Desorption Models
Lighty, J.S.; Silcox, G.D.; Pershing, D.W.; Cundy, V.A. and Linz, D.G.
Accepted for publication in Environ. Science Tech., 1989. Funded by the Gas Research Institute, Dave Linz, Project Manager, National Science Foundation/Presidential Young Investigators, ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, and US Department of Energy.
A major research effort has been initiated to characterize the rate-controlling processes associated with the evolution of hazardous materials from soils. A threefold experimental approach is being used in conjunction with computer modeling to analyze thermal desorption of contaminants. Phenomena occurring both inside particles (intraparticle) and with a bed of particles (interparticle) were studied.
The results obtained suggest that the most important process variables are local thermal environment and gas-phase contaminant concentration because the adsorption equilibrium characteristics of the contaminant/soil pair control the desorption of contaminant from a particle at a given temperature. A mass-transfer/desorption model, which assumes gas/solid equilibrium at all points and time, is proposed and the model was found to predict the measured temperature dependence.
1988-1987
Characterization of Thermal Desorption Phenomena for the Clean-Up of Contaminated Soil
Lighty, J.S.; Pershing, D.W.; Cundy, V.A. and Linz, D.G.
Accepted for Nuclear & Chemical Waste Management, 1987. 32 pgs. Funded by ACERC (National Science Foundation and Associates and Affiliates).
The overall goal of this research is to develop an understanding of the fundamental transport phenomena associated with the evolution of hazardous materials from solids, in particular contaminated soils. At the present time, incineration is a relatively costly alternative for the clean up of contaminated soils. An understanding of the mass transfer and heat transfer limitations might lead to a more economical option, where the contaminants are desorbed from the soil at lower temperatures in a primary combustor and then a secondary, high temperature combustor (afterburner) decomposes the hazardous off-gases. This work is aimed at providing fundamental rate information which will be used to model thermal desorption of contaminants from soils under a variety of thermal conditions, soil properties and contaminants.
The experimental approach is threefold. First, a bench scale particle characterization reactor (PCR) has been developed and is being used to characterize intraparticle transport under conditions where the bulk concentration and temperature at the particle surface are known. Following these studies, a packed-bed reactor will be used to examine interparticle transport within a well-characterized bed of particles. In the third portion of the work, a 73 kW pilot-scale rotary kiln will be used to obtain time resolved measurements of trace species evolution. This paper reports recent PCR results that indicate that soil properties, type of contaminant, and temperature are important in desorption of contaminants from soil particles.
The overall goal of this research is to develop an understanding of the fundamental transport phenomena associated with the evolution of hazardous materials from solids, in particular contaminated soils. At the present time, incineration is a relatively costly alternative for the clean up of contaminated soils and it may render the soil inert. A more economical option is to desorb the contaminants from the soil at lower temperatures and then use high temperature incineration to decompose the hazardous off-gases. This work is aimed at providing fundamental rate information which may be used to model the thermal desorption of contaminants from soils under a wide variety of thermal conditions.
The experimental approach is three-fold. First, a bench-scale particle characterization reactor (PCR) has been developed and is being used to characterize intraparticle transport under conditions where the bulk concentration and temperature at the particle surface are known. Following these studies, a packed bed reactor will be used to examine interparticle transport within a well-characterized bed of particles. In the third portion of the work, a 73,000 Watt pilot-scale rotary kiln will be used to reports recent PCR and kiln results; it does not address the packed bed reactor studies since they are just being initiated. The PCR results indicate that soil pore structure is important in desorption of contaminants from soil particles and that the desorption/diffusion step is probably a controlling mechanism.
Rotary Kiln Incineration I: An In-Depth Study - Liquid Injection
Cundy, V.A.; Lester, T.W.; Morse, J.S.; Montestruc, A.N.; Leger, C.B.; Acharya, S.; Sterling, A.M. and Pershing, D.W.
Submitted to Journal of the Air Pollution Control Association, 1988. 39 pgs. Funded by Environmental Protection Agency.
A multifaceted experimental and theoretical program directed toward the understanding of rotary kiln performance is underway. Following a general overview of the program, we describe in more detail the program components including: In-situ measurements from an industrial-scale rotary kiln located at the Louisiana Division of Dow Chemical USA in Plaquemine, Louisiana; laboratory-scale desorption characterization and kiln-simulator studies; and incinerator modeling efforts. Using water-cooled probes, hot-zone samples have been obtained from both the full-scale rotary kiln and the afterburner and have been analyzed subsequently using GC and/or GC/MS techniques. We report on these preliminary measurements in some detail.
Rotary Kiln Incineration II: Laboratory Scale Desorption and Kiln Simulator Studies - Solids
Cundy, V.A.; Lester, T.W.; Morse, J.S.; Montestruc, A.N.; Leger, C.B.; Acharya, S.; Sterling, A.M. and Pershing, D.W.
Submitted to Journal of the Air Pollution Control Association, 1988. 28 pgs. Funded by Gas Research Institute, ACERC (National Science Foundation and Associates and Affiliates), and National Science Foundation/Presidential Young Investigators.
With landfill costs increasing and regulations on landfilling becoming more stringent, alternatives to conventional hazardous waste treatment strategies are becoming more desirable. Incineration is presently a permanent, proven solution for the disposal of most organic contaminants, but also a costly one, especially in the case of solids that require some auxiliary fuel. The goal of this research is to develop an understanding of the phenomena associated with the evolution of contaminants from solids in the primary combustor of an incineration system. A four-fold approach is being used. First, a bench scale Particle Characterization Reactor was developed to study the transport phenomena on a particle basis, where the controlling processes are mainly intraparticle. Second, a Bed Characterization Reactor was built to examine the controlling transport phenomena within a bed of particles, where the processes are primarily interparticle. The results of these studies can be applied to any primary combustor. A pilot-scale rotary kiln was developed to study the evolution of contaminants from solids within a realistic temperature and rotation environment. Finally, in-situ measurements are being obtained from a full-scale rotary-kiln.
This paper describes results obtained in a study using a commercial sorbent contaminated with toluene. The data are from the Particle Characterization Reactor and the Rotary-Kiln Simulator. The results show that the method of contamination and charge size does not have a large effect on desorption, while temperature and contaminant concentration are important parameters in the evolution of contaminants in a rotary kiln.
Rotary Kiln Incineration III: An In-depth Study - Full-Scale Incineration of Carbon Tetrachloride
Cundy, V.A.; Lester, T.W.; Morse, J.S.; Montestruc, A.N.; Leger, C.B.; Acharya, S.; Sterling, A.M. and Pershing, D.W.
Submitted to Journal of the Air Pollution Control Association, 1988. 31 pgs. Funded by Environmental Protection Agency.
Temperature and stable species concentration data are presented from various locations within a full-scale rotary kiln firing natural gas/carbon tetrachloride/air. The data are being collected as part of a cooperative program involving university, industrial and government participation. The overall goal of the program is to develop a rudimentary understanding of and a predictive capability for rotary kiln and afterburner performance as influenced by basic design and operation parameters. The data clearly demonstrates that severe non-uniformities exist at the kiln exit under certain operating conditions. Even so, the data further indicate that high destruction efficiencies were achieved through adequate secondary combustion processing. The data further show that flow perturbations from within the kiln can persist well into the afterburner section and even into the stack.
Transport Fundamentals for the Thermal Remediation of Contaminated Soils
Lighty, J.S.; Silcox, G.D.; Pershing, D.W.; Cundy, V.A. and Linz, D.G.
Submitted for Review to AIChE Journal, 1988. 23 pgs. Funded by Gas Research Institute, ACERC (National Science Foundation and Associates and Affiliates), and National Science Foundation/Presidential Young Investigators.
A major research effort has been initiated to characterize the transport phenomena associated with the evolution of hazardous materials from contaminated soils. A threefold experimental approach is being used in conjunction with computer modeling to analyze thermal desorption of contaminants from soils under a variety of experimental conditions. First, a particle-characterization reactor (PCR) is being employed to characterize intraparticle transport under conditions where the bulk concentration and temperature at the particle surface are known. Secondly, a packed-bed reactor is being used to examine interparticle transport within a bed of particles. In the third portion of the work, a 73 kW pilot-scale rotary kiln is providing time-resolved measurements of the species evolution. The results from the PCR experiments and modeling are reported in this manuscript.
The PCR experimental results obtained suggest that the most important process variable is local thermal environment and that the absorption characteristics of the contaminant/soil pair are important in the desorption process. The adsorption characteristics are a function of local temperature, thus accounting for the steep dependence of the cleanup efficiency of a soil on temperature. In addition, the adsorption characteristics are influenced by soil type and moisture; it has been found that these parameters also effect desorption of contaminants. A mass-transfer model, which assumes gas/solid equilibrium at all points and times, is proposed and the model predictions were found to exhibit temperature dependence similar to the data.
The Clean Up of Contaminated Soil By Thermal Desorption
Lighty, J.S.; Pershing, D.W.; Cundy, V.A.; Groves, F.R. Jr. and Linz, D.G.
Proc. 2nd Int. Conf. on New Frontiers in Hazardous Waste Management, 1987, NUS, Pittsburgh, PA. 10 pgs. Funded by Gas Research Institute, National Science Foundation, and ACERC (National Science Foundation and Associates and Affiliates).
The overall goal of this research is to develop an understanding of the fundamental transport phenomena associated with the evolution of hazardous materials from solids, in particular, contaminated soils. At the present time, incineration is a relatively costly alternative for the clean up of contaminated soils and it may render the soil inert. A more economical option is to desorb the contaminants from the soil at lower temperatures and then use high temperature incineration to decompose the hazardous off-gases. This work is aimed at providing fundamental rate information which may be used to model the thermal desorption of contaminants from soils under a wide variety of thermal conditions.
The experimental approach is threefold First, a bench-scale particle characterization reactor (PCR) has been developed and is being used to characterize intraparticle transport under conditions where the bulk concentration and temperature at the particle surface are known. Following these studies, a packed bed reactor will be used to examine interparticle transport within a well-characterized bed of particles. In the third portion of the work, a 73,000 Watt pilot-scale rotary kiln will be used to obtain time resolved measurements of trace species evolution. This paper reports recent PCR and kiln results; it does not address the packed bed reactor studies since they are just being initiated. The PCR results indicate that soil pore structure is important in desorption of contaminants from soil particles and that the desorption/diffusion step is probably a controlling mechanism.
Fundamentals of Hazardous Solid Waste Incineration in a Rotary Kiln Environment
Lighty, J.S.; Silcox, G.D.; Britt, R.; Owens, W.D.; Pershing, D.W. and Cundy, V.A.
Proc. AFRC Int'l. Symposium on Waste Incineration, 1987, Palm Springs. Funded by Environmental Protection Agency.
With landfill costs increasing and regulations on landfilling becoming more stringent, alternatives to conventional hazardous waste treatment strategies are becoming more desirable. Incineration is presently a permanent, proven solution for the disposal of most organic contaminants, but also a costly one, especially in the case of solids that require some auxiliary fuel. The goal of this research is to develop an understanding of the phenomena associated with the evolution of contaminants from solids in the primary combustor of an incineration system. A threefold approach has been used. First, a bench-scale Particle Characterization Reactor was developed to study the transport phenomena on a particle basis, where the controlling processes are mainly intraparticle. Second, a Bed Characterization Reactor was built to examine the controlling transport phenomena within a bed of particles, where the processes are primarily interparticle. The results of these studies can be applied to any primary combustor. Finally a pilot-scale rotary kiln was developed to study the evolution of contaminants from solids within a realistic temperature and rotation environment.
This paper describes results obtained in a study using a commercial sorbent contaminated with toluene. The data are from the Particle Characterization Reactor and the Rotary-Kiln Simulator. The results show that the method of contamination and charge size does not have a large effect on desorption, while temperature and contaminant concentration are important parameters in the evolution of contaminants in a rotary kiln. Preliminary modeling efforts for the kiln are also discussed.