Larsen, FS
1993
Thermal Treatment of Hazardous Wastes: A Comparison of Fluidized Bed and Rotary Kiln Incineration
Rink, K.K.; Larsen, F.S.; Kozinski, J.A.; Lighty, J.S.; Silcox, G.D. and Pershing, D.W.
Energy & Fuels, 7 (6):803-814, 1993. Funded by ACERC.
Large volumes of sludge are produced by a wide variety of industrial processes and by municipal wastewater treatment. Interest in incinerating these sludges, either alone, or co-fired with other fuels, is increasing. The issues surrounding sludge incineration in rotary kilns and fluidized beds were identified through a series of pilot-scale tests using two slightly different paper mill sludges. The specific issues examined include hydrocarbon emissions, NOx emissions, and bottom and fly ash properties. A 61-cm i.d. X 61-cm long, 130-kW pilot-scale rotary kiln simulator (RKS) and a 23-cm i.d., 300-kW circulating fluidized bed combustor (CFB) were maintained at a nominal temperature of 1100 K and a stoichiometric ratio of 1.5. The rotary kiln was fed in a batch mode in order to simulate the passage of solids through a kiln. The fluidized bed was fed in both batch and continuous modes. Samples were removed from the kiln (bottom ash) and transition section (fly ash). Samples of the fluidized bed materials were removed from the bed (bottom ash) and after the cyclone (fly ash). The exhaust gases were analyzed continuous for hydrocarbons, CO, O2, NO, and CO2. This paper presents data on these analyses as well as NO conversion and ash properties. The production of NO in the RKS was dependent on the supply of nitrogen (in the sludge) and oxygen (in the gas phase), in the reactor. The availability of oxygen to the sludge was affected by the particle diameter of the sludge, the charge size, and whether a solids bed was present at the time of the incineration. In the CFB, the nitrogen-containing compounds were oxidized primarily downstream of the feedboard region, resulting in elevated levels of NO in the transition and cyclone regions. Carbon monoxide concentrations were high immediately above the bed, which led to the reduction of NO inside the freeboard zone. In both the CFB and RKS tests little unburned hydrocarbons were present in the exhaust gas streams. Formation of fly ash particles was dependent on types of incinerated material (sludge; mixture of sludge and silica sand). Bottom ash material resembled randomly organized skeletons (or cenospheric skeletons), the structure of which was independent of the type of sludge or reactor. Smaller fly ash and bottom ash particles were formed during CFB incineration experiments.
On-Line Monitoring of Formaldehyde in Combustion Gases Using Gas Chromatography/Mass Spectrometry
McClennen, W.H.; Sheya, S.A.N.; Arnold, N.S.; Meuzelaar, H.L.C.; Larsen, F.S. and Silcox, G.D.
Incineration of Hazardous Wastes-2; Toxic Combustion By-Products:545-555, (in press). Funded by Consortium for Fossil Fuel Liquefaction and ACERC.
This paper describes a method for on-line gas chromatography/mass spectrometry (GC/MS) of formaldehyde in combustion gases. The method uses a recently developed vapor-sampling inlet to monitor the concentration of formaldehyde and other products of incomplete combustion (PICs) from the burning of plain and phenol-formaldehyde resin treated wood chips. Other PICs that were simultaneously monitored included ketene, propylene, propyne and acetaldehyde. The direct analysis method has detection limits of less than 1 ppm for the reactive formaldehyde and excellent selectivity for determinations in the complex mixtures of combustion products. The rapid sampling technique allows monitoring of transient events of only a few minutes or less duration. Examples of the technique include the detection of sample line problems and the comparison of PIC concentrations from different points in the combustion exhaust stream.
1992
Hydrocarbon and Formaldehyde Emissions from the Combustion of Pulverized Wood Waste
Larsen, F.S.; McClennen, W.H.; Deng, X.-X.; Silcox, G.D.and Allison, K.
Combustion Science and Technology, 1992 (in press). (Also presented at The Second International Congress on Toxic By-Products: Formation and Control, Salt Lake City, UT, March 1992). Funded by Weyerhaeuser Corp. and ACERC.
Hydrocarbon and formaldehyde emissions from the combustion of pulverized wood waste were measured in 100 kW, cylindrical combustion chamber measuring 0.61 by 0.61 m. The wood was pneumatically conveyed to the burner and natural gas was used as an auxiliary fuel. The wood was screened prior to feeding so that its size distribution was representative of the suspension phase of a stoker boiler. Chamber wall and gas temperatures ranged from 920 to 1200 K and oxygen concentrations ranged from 2 to 9 percent, dry. Two types of waste were studied, plain wood and wood that was impregnated with a phenol-formaldehyde resin. The latter was a by-product of particleboard production. In general, the emissions of products of incomplete combustion (PICs) from the resinated waste were higher than those produced by plain wood. This may have been due to three factors: 1) the resinated wood was slightly wetter than the plain wood (6-9 percent by weight vs. 3 percent), 2) there was a difference in particle size distribution between the two materials as received, the resinated wood being larger, and 3) the resin may have had an effect on the emissions. Ultimate analyses of the two wastes showed no significant differences, other than moisture, in composition. At temperatures above 1200 K, total hydrocarbon emissions were roughly 10 to 29 ppm and formaldehyde emissions were less than the detection limit of 1 ppm. Typical waste wood boiler temperatures are roughly 1600 K. Hence, unless there are cool, poorly mixed regions in the full-scale facility, hydrocarbon and formaldehyde emissions should not be significant. However, the emissions from burning the two different types of wood would probably be different if all operating parameters in the wood-fired boiler are held constant.
1991
Hydrocarbon and Formaldehyde Emissions from the Combustion of Pulverized Wood Waste
Larsen, F.S.; McClennen, W.H.; Deng, X.-X.; Silcox, G.D. and Allison, K.
Combustion Science and Technology, 1991 (in press). Funded by Weyerhaeuser Corp. and ACERC.
Hydrocarbon and formaldehyde emissions from the combustion of pulverized wood waste were measured in 100 kW, cylindrical combustion chamber measuring 0.61 by 0.61 m. The wood was pneumatically conveyed to the burner and natural gas was used as an auxiliary fuel. The wood was screened prior to feeding so that its size distribution was representative of the suspension phase of a stoker boiler. Chamber wall and gas temperatures ranged from 920 to 1200 K and oxygen concentrations ranged from 2 to 9 percent, dry. Two types of waste were studied, plain wood and wood that was impregnated with a phenol-formaldehyde resin. The latter was a by-product of particleboard production. In general, the emissions of products of incomplete combustion (PICs) from the resinated waste were higher than those produced by plain wood. This may have been due to three factors: 1) the resinated wood was slightly wetter than the plain wood (6-9 percent by weight vs. 3 percent), 2) there was a difference in particle size distribution between the two materials as received, the resinated wood being larger, and 3) the resin may have had an effect on the emissions. Ultimate analyses of the two wastes showed no significant differences, other than moisture, in composition. At temperatures above 1200 K, total hydrocarbon emissions were roughly 10 to 29 ppm and formaldehyde emissions were less than the detection limit of 1 ppm. Typical waste wood boiler temperatures are roughly 1600 K. Hence, unless there are cool, poorly mixed regions in the full-scale facility, hydrocarbon and formaldehyde emissions should not be significant. However, the emissions from burning the two different types of wood would probably be different if all operating parameters in the wood-fired boiler are held constant.
On-Line Monitoring of Formaldehyde in Comubustion Gases Using Gas Chromatography/Mass Spectrometry
McClennen, W.H.; Sheya, S.A.N.; Arnold, N.S.; Meuzelaar, H.L.C.; Deng, X.-X.; Larsen, F.S. and Silcox, G.D.
Combustion Science and Technology, 1991 (in press). Funded by ACERC.
This paper describes a method for on-line gas chromatography/mass spectrometry (GC/MS) of formaldehyde in combustion gases. The method uses a recently developed vapor-sampling inlet to monitor the concentration of formaldehyde and other products of incomplete combustion (PICs) from the burning of plain and phenol-formaldehyde resin treated wood chips. Other PICs that were simultaneously monitored included ketene, propylene, propyne and acetaldehyde. The direct analysis method has detection limits of less than 1 ppm for the reactive formaldehyde and excellent selectivity for determinations in the complex mixtures of combustion products. The rapid sampling technique allows monitoring of transient events of only a few minutes or less duration. Examples of the technique include the detection of sample line problems and the comparison of PIC concentrations from different points in the combustion exhaust stream.
1990
Mathematical and Physical Modeling of Rotary Kilns with Applications to Scaling and Design
Silcox, G.D.; Larsen, F.S. and Pershing, D.W.
Combustion Science and Technology, 1990 (In press). Funded by ACERC and Gas Research Institute.
The heat and mass transfer in an indirectly fired rotary kiln are examined using a combination of physical and mathematical modeling. The physical modeling is used to determine characteristic mixing times in a slumping kiln bed. These times are compared with characteristic times for diffusion of heat and mass through the bed in order to justify a lumped capacitance analysis of heat and mass transfer.
Mathematical models of heat and mass transfer are used to examine the effects of design and operating parameters on bed temperature and desorption rates. Limited comparisons with temperature measurements are presented. The design and operating parameters studied include kiln length, solid residence time, solid feed rate, and feed moisture content. The effects of moisture are particularly important to both heat and mass transfer. Scaling considerations are examined and it is shown that maintaining equivalent wall temperature profiles, fill fractions, moisture levels, and burden residence times does not necessarily result in equivalent bed thermal profiles.
Larsen, FS
1993
Thermal Treatment of Hazardous Wastes: A Comparison of Fluidized Bed and Rotary Kiln Incineration
Rink, K.K.; Larsen, F.S.; Kozinski, J.A.; Lighty, J.S.; Silcox, G.D. and Pershing, D.W.
Energy & Fuels, 7 (6):803-814, 1993. Funded by ACERC.
Large volumes of sludge are produced by a wide variety of industrial processes and by municipal wastewater treatment. Interest in incinerating these sludges, either alone, or co-fired with other fuels, is increasing. The issues surrounding sludge incineration in rotary kilns and fluidized beds were identified through a series of pilot-scale tests using two slightly different paper mill sludges. The specific issues examined include hydrocarbon emissions, NOx emissions, and bottom and fly ash properties. A 61-cm i.d. X 61-cm long, 130-kW pilot-scale rotary kiln simulator (RKS) and a 23-cm i.d., 300-kW circulating fluidized bed combustor (CFB) were maintained at a nominal temperature of 1100 K and a stoichiometric ratio of 1.5. The rotary kiln was fed in a batch mode in order to simulate the passage of solids through a kiln. The fluidized bed was fed in both batch and continuous modes. Samples were removed from the kiln (bottom ash) and transition section (fly ash). Samples of the fluidized bed materials were removed from the bed (bottom ash) and after the cyclone (fly ash). The exhaust gases were analyzed continuous for hydrocarbons, CO, O2, NO, and CO2. This paper presents data on these analyses as well as NO conversion and ash properties. The production of NO in the RKS was dependent on the supply of nitrogen (in the sludge) and oxygen (in the gas phase), in the reactor. The availability of oxygen to the sludge was affected by the particle diameter of the sludge, the charge size, and whether a solids bed was present at the time of the incineration. In the CFB, the nitrogen-containing compounds were oxidized primarily downstream of the feedboard region, resulting in elevated levels of NO in the transition and cyclone regions. Carbon monoxide concentrations were high immediately above the bed, which led to the reduction of NO inside the freeboard zone. In both the CFB and RKS tests little unburned hydrocarbons were present in the exhaust gas streams. Formation of fly ash particles was dependent on types of incinerated material (sludge; mixture of sludge and silica sand). Bottom ash material resembled randomly organized skeletons (or cenospheric skeletons), the structure of which was independent of the type of sludge or reactor. Smaller fly ash and bottom ash particles were formed during CFB incineration experiments.
On-Line Monitoring of Formaldehyde in Combustion Gases Using Gas Chromatography/Mass Spectrometry
McClennen, W.H.; Sheya, S.A.N.; Arnold, N.S.; Meuzelaar, H.L.C.; Larsen, F.S. and Silcox, G.D.
Incineration of Hazardous Wastes-2; Toxic Combustion By-Products:545-555, (in press). Funded by Consortium for Fossil Fuel Liquefaction and ACERC.
This paper describes a method for on-line gas chromatography/mass spectrometry (GC/MS) of formaldehyde in combustion gases. The method uses a recently developed vapor-sampling inlet to monitor the concentration of formaldehyde and other products of incomplete combustion (PICs) from the burning of plain and phenol-formaldehyde resin treated wood chips. Other PICs that were simultaneously monitored included ketene, propylene, propyne and acetaldehyde. The direct analysis method has detection limits of less than 1 ppm for the reactive formaldehyde and excellent selectivity for determinations in the complex mixtures of combustion products. The rapid sampling technique allows monitoring of transient events of only a few minutes or less duration. Examples of the technique include the detection of sample line problems and the comparison of PIC concentrations from different points in the combustion exhaust stream.
1992
Hydrocarbon and Formaldehyde Emissions from the Combustion of Pulverized Wood Waste
Larsen, F.S.; McClennen, W.H.; Deng, X.-X.; Silcox, G.D.and Allison, K.
Combustion Science and Technology, 1992 (in press). (Also presented at The Second International Congress on Toxic By-Products: Formation and Control, Salt Lake City, UT, March 1992). Funded by Weyerhaeuser Corp. and ACERC.
Hydrocarbon and formaldehyde emissions from the combustion of pulverized wood waste were measured in 100 kW, cylindrical combustion chamber measuring 0.61 by 0.61 m. The wood was pneumatically conveyed to the burner and natural gas was used as an auxiliary fuel. The wood was screened prior to feeding so that its size distribution was representative of the suspension phase of a stoker boiler. Chamber wall and gas temperatures ranged from 920 to 1200 K and oxygen concentrations ranged from 2 to 9 percent, dry. Two types of waste were studied, plain wood and wood that was impregnated with a phenol-formaldehyde resin. The latter was a by-product of particleboard production. In general, the emissions of products of incomplete combustion (PICs) from the resinated waste were higher than those produced by plain wood. This may have been due to three factors: 1) the resinated wood was slightly wetter than the plain wood (6-9 percent by weight vs. 3 percent), 2) there was a difference in particle size distribution between the two materials as received, the resinated wood being larger, and 3) the resin may have had an effect on the emissions. Ultimate analyses of the two wastes showed no significant differences, other than moisture, in composition. At temperatures above 1200 K, total hydrocarbon emissions were roughly 10 to 29 ppm and formaldehyde emissions were less than the detection limit of 1 ppm. Typical waste wood boiler temperatures are roughly 1600 K. Hence, unless there are cool, poorly mixed regions in the full-scale facility, hydrocarbon and formaldehyde emissions should not be significant. However, the emissions from burning the two different types of wood would probably be different if all operating parameters in the wood-fired boiler are held constant.
1991
Hydrocarbon and Formaldehyde Emissions from the Combustion of Pulverized Wood Waste
Larsen, F.S.; McClennen, W.H.; Deng, X.-X.; Silcox, G.D. and Allison, K.
Combustion Science and Technology, 1991 (in press). Funded by Weyerhaeuser Corp. and ACERC.
Hydrocarbon and formaldehyde emissions from the combustion of pulverized wood waste were measured in 100 kW, cylindrical combustion chamber measuring 0.61 by 0.61 m. The wood was pneumatically conveyed to the burner and natural gas was used as an auxiliary fuel. The wood was screened prior to feeding so that its size distribution was representative of the suspension phase of a stoker boiler. Chamber wall and gas temperatures ranged from 920 to 1200 K and oxygen concentrations ranged from 2 to 9 percent, dry. Two types of waste were studied, plain wood and wood that was impregnated with a phenol-formaldehyde resin. The latter was a by-product of particleboard production. In general, the emissions of products of incomplete combustion (PICs) from the resinated waste were higher than those produced by plain wood. This may have been due to three factors: 1) the resinated wood was slightly wetter than the plain wood (6-9 percent by weight vs. 3 percent), 2) there was a difference in particle size distribution between the two materials as received, the resinated wood being larger, and 3) the resin may have had an effect on the emissions. Ultimate analyses of the two wastes showed no significant differences, other than moisture, in composition. At temperatures above 1200 K, total hydrocarbon emissions were roughly 10 to 29 ppm and formaldehyde emissions were less than the detection limit of 1 ppm. Typical waste wood boiler temperatures are roughly 1600 K. Hence, unless there are cool, poorly mixed regions in the full-scale facility, hydrocarbon and formaldehyde emissions should not be significant. However, the emissions from burning the two different types of wood would probably be different if all operating parameters in the wood-fired boiler are held constant.
On-Line Monitoring of Formaldehyde in Comubustion Gases Using Gas Chromatography/Mass Spectrometry
McClennen, W.H.; Sheya, S.A.N.; Arnold, N.S.; Meuzelaar, H.L.C.; Deng, X.-X.; Larsen, F.S. and Silcox, G.D.
Combustion Science and Technology, 1991 (in press). Funded by ACERC.
This paper describes a method for on-line gas chromatography/mass spectrometry (GC/MS) of formaldehyde in combustion gases. The method uses a recently developed vapor-sampling inlet to monitor the concentration of formaldehyde and other products of incomplete combustion (PICs) from the burning of plain and phenol-formaldehyde resin treated wood chips. Other PICs that were simultaneously monitored included ketene, propylene, propyne and acetaldehyde. The direct analysis method has detection limits of less than 1 ppm for the reactive formaldehyde and excellent selectivity for determinations in the complex mixtures of combustion products. The rapid sampling technique allows monitoring of transient events of only a few minutes or less duration. Examples of the technique include the detection of sample line problems and the comparison of PIC concentrations from different points in the combustion exhaust stream.
1990
Mathematical and Physical Modeling of Rotary Kilns with Applications to Scaling and Design
Silcox, G.D.; Larsen, F.S. and Pershing, D.W.
Combustion Science and Technology, 1990 (In press). Funded by ACERC and Gas Research Institute.
The heat and mass transfer in an indirectly fired rotary kiln are examined using a combination of physical and mathematical modeling. The physical modeling is used to determine characteristic mixing times in a slumping kiln bed. These times are compared with characteristic times for diffusion of heat and mass through the bed in order to justify a lumped capacitance analysis of heat and mass transfer.
Mathematical models of heat and mass transfer are used to examine the effects of design and operating parameters on bed temperature and desorption rates. Limited comparisons with temperature measurements are presented. The design and operating parameters studied include kiln length, solid residence time, solid feed rate, and feed moisture content. The effects of moisture are particularly important to both heat and mass transfer. Scaling considerations are examined and it is shown that maintaining equivalent wall temperature profiles, fill fractions, moisture levels, and burden residence times does not necessarily result in equivalent bed thermal profiles.