Milne, CR
1990
High-Temperature, Short Time Sulfation of Calcium-Based Sorbents: I. Theoretical Sulfaction Model
Milne, C.R.; Silcox, G.D. and Pershing, D.W.
I & EC Research, 29, 2192, 1990. Funded by Environmental Protection Agency and ACERC.
A mathematical model for the sulfation of CaO is developed around the overlapping grain concept employed in the calcination and sintering models of Milne et al. (1988). The potential influence of high mass-transfer rates from simultaneous calcination of CaCO3 or Ca(OH)2 is incorporated in the mass-transfer coefficient for SO2 diffusion to the particle. A solution scheme for the nonlinear differential equation governing pore diffusion with changing particle structure is developed. The influence of grain overlap on product-layer diffusion is quantified. The model predictions show good agreement with the differential reactor data of Borgwardt and Bruce (1986) that include the influences of surface area, temperature, and SO2 partial pressure.
High-Temperature, Short Time Sulfation of Calcium-Based Sorbents: II. Experimental Data and Theoretical Model Predictions
Milne, C.R.; Silcox, G.D. and Pershing, D.W.
I & EC Research, 29, 2202, 1990. Funded by Environmental Protection Agency and ACERC.
The fundamental processes for injection of CaCO3 and Ca(OH)2 for the removal of SO2 from combustion gases of coal-fired boilers are analyzed on the basis of experimental data and a comprehensive theoretical model. Sulfation data were obtained in a 30-KW isothermal dispersed-phase reactor at conditions simulating those of upper-furnace injection. The theoretical model accounts for particle structure, calcination, sintering, sulfation, and heat and mass transfer. Pore diffusion, product-layer diffusion, and sintering appear to be the principle processes that govern the rate of SO2 capture for the hydrate particles of interest for commercial dry sorbent injection.
Calcination and Sintering Models for Application to High-Temperature, Short Time Sulfation of Calcium-Based Sorbents
Milne, C.R.; Silcox, G.D. and Pershing, D.W.
I & EC Research, 29, 139, 1990. Funded by Environmental Protection Agency and ACERC.
To simulate the staged availability of transient high surface area CaO observed in high-temperature flow-reactor data, the rate of calcination of CaCO3 of Ca(OH)2 is described by an empirical modification of the shrinking-core model. The physical model depicts particle decomposition by the shrinking-core mechanism. The subsequent time dependent decrease in CaO reactivity (surface area and porosity) due to sintering is simulated by reducing the grain-center spacing for the matrix of overlapping CaO grains. Information from SEM micrographs and from other physical property measurements of the porous particles is incorporated. This submodel simulates the time dependent availability and reactivity of CaO for a comprehensive model used to study sulfation of CaCO3 and Ca(OH)2 particles at upper-furnace injection conditions.
1989
Calcination and Sintering Models for Application to High-Temperature, Short-Time Sulfation of Calcium-Based Sorbents
Milne, C.R.; Silcox, G.D.; Pershing, D.W. and Kirchgessner, D.A.
Accepted for publication in I & EC Res., 1989. Funded by the US Environmental Protection Agency, ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, and US Department of Energy.
To simulate the staged availability of transient high surface area CaO observed in high-temperature flow-reactor data, the rate of calcination of CaCO3 or Ca(OH)2 is described by an empirical modification of the shrinking-core model. The physical model depicts particle decomposition by the shrinking-core mechanism. The subsequent time dependent decrease in CaO reactivity (surface area and porosity) due to sintering is simulated by reducing the grain-center spacing for the matrix of overlapping CaO grains. Information from SEM micrographs and from other physical property measurements of the porous particles is incorporated. This submodel simulates the time dependent availability and reactivity of CaO for a comprehensive model used to study sulfation of CaCO3 or Ca(OH)2 particles at upper-furnace injection conditions.
1988-1987
Off-Line Process Monitoring of Coal-Derived Liquid Fuels by Computer Assisted Low Mass Spectrometry
Taghizadeh, K.; Davis, B.H.; Windig, W. and Meuzelaar, H.L.C.
Fossil Fuel Analysis by Mass Spectrometry, 1988, T.A. Milne, (ed.), in press. Funded by Commonwealth of Kentucky, Kentucky Energy Cabinet, US Department of Energy and Consortium For Fossil Fuel Liquefaction Science.
Compositional changes of Coal-Derived Liquids (CDL's) during hydrotreatment on fixed bed catalysts can be investigated by Low Voltage (12 eV) MS in combination with multivariate analysis without chromatographic preseparation. Low voltage (12 eV) MS data were obtained and compared under two inlet conditions; MS inlet (1) at ambient temperatures and (2) preheated to about 200ºC. The major trend found in both data sets by Factor analysis was the hydrotreatment effect, namely hydroaromatic (hydrotreater product) vs. aromatic (hydrotreater feed) compounds. A second "time + temperature" trend which reflected the aging of the catalyst as well as the temperature of the hydrotreater reactor was only obtained under ambient inlet temperature conditions. Numerically extracted spectra along the second trend show that more low molecular weight components were found early in the process and also at lower temperatures, whereas more of the higher molecular weight components, primarily alkyl substituted polynuclear aromatics, were obtained later in the process at higher temperatures of the hydrotreater.
A supercritical fluid chromatographic system was constructed to provide separations and fraction collection on a semipreparative scale. Columns packed with silica materials of intermediate particle sizes (30-70 mm) were used to allow dynamic pressure programming with minimum pressure drop of the CO2 mobile phase along the length of the column. A variety of complex coal- and petroleum-derived polycyclic aromatic compound mixtures were fractionated according to the number of aromatic rings using columns packed with an NH2- modified stationary phase bonded on silica particles. The CO2 mobile phase was programmed with an alternating series of linear pressure ramps and isobaric intervals to effect even peak spacing and near base line resolution of compounds of differing ring number in a coal tar. A solvent refined coal heavy distillate and a crude oil were similarly fractionated. Effluents were monitored with an ultraviolet spectrophotometer at 254 nm and a flame ionization detector while fractions were collected in pressurized vessels for subsequent analysis by capillary gas chromatography. Sample capacities of up to 20 mg were possible with this system.
Time Resolved Sulfation Rate Measurement for Sized Sorbents
Milne, C.R. and Pershing, D.W.
Proc. 4th Annual Pittsburgh Coal Conf., 1987. 14 pgs. Funded by ACERC (National Science Foundation and Associates and Affiliates).
The sulfation of raw and sized calcium-based sorbents under high-temperature, short time conditions typical of injection in pulverized coal fired boilers was studied. A 100,000 Btu/hr refractory walled flow reactor was used to obtain isothermal SO2 capture which occurs in the first 30 ms after injection and results from inherent particle size difference between the two sorbent types. In this instance, the hydrate particle size is one-tenth that of the carbonate, and the hydrate capture at Ca/S = 2 is 30% versus 5% for the carbonate.
Beyond approximately 200 ms the sulfation rate was insensitive to particle size, but the rate of SO2 capture increase with the hydrated sorbent was larger than that measured with the carbonate sorbent. This suggests that the ultimate extent of sulfation is also influenced by structural parameters. Ultimate calcium utilization does not appear to be significantly influenced by the calcination rate differences between hydrates and carbonates for particles smaller than 5 um. For large carbonate particles, the calcination delay slightly retards the initial sulfur capture and reduces the ultimate calcium utilization.
Time Resolved Sulfation Rate Measurements for Sized Sorbents
Milne, C.R. and Pershing, D.W.
Proc. 4th Annual Pittsburgh Coal Conf., 1987. 6 pgs. Funding source ACERC (National Science Foundation and Associates and Affiliates).
The sulfation of raw and sized calcium-based sorbents under high-temperature, short time conditions typical of injection in pulverized coal fired boilers was studied. A 100,000 Btu/hr refractory walled flow reactor was used to obtain isothermal SO2 capture data for a carbonate and a hydrate derived from the carbonate as a function of reactor residence time and particle size.
Experimental results confirmed the importance of sorbent type and particle size. The hydrated sorbent was clearly superior to the carbonate. This difference is primarily attributable to a dramatic difference in prompt SO2 capture which occurs in the first 30 ms after injection and results from inherent particle size difference between the two sorbent types. In this instance, the hydrate particle size is one-tenth that of the carbonate, and the hydrate capture at Ca/S = 2 is 30% versus 5% for the carbonate.
Beyond approximately 200 ms the sulfation rate was insensitive to particle size, but the rate of SO2 capture increase with the hydrated sorbent was larger than that measured with the carbonate sorbent. This suggests that the ultimate extent of sulfation is also influenced by structural parameters. Ultimate calcium utilization does not appear to be significantly influenced by the calcination rate differences between hydrates and carbonates for particles smaller than 5 µm. For large carbonate particles, the calcination delay slightly retards the initial sulfur capture and reduces the ultimate calcium utilization.
Milne, CR
1990
High-Temperature, Short Time Sulfation of Calcium-Based Sorbents: I. Theoretical Sulfaction Model
Milne, C.R.; Silcox, G.D. and Pershing, D.W.
I & EC Research, 29, 2192, 1990. Funded by Environmental Protection Agency and ACERC.
A mathematical model for the sulfation of CaO is developed around the overlapping grain concept employed in the calcination and sintering models of Milne et al. (1988). The potential influence of high mass-transfer rates from simultaneous calcination of CaCO3 or Ca(OH)2 is incorporated in the mass-transfer coefficient for SO2 diffusion to the particle. A solution scheme for the nonlinear differential equation governing pore diffusion with changing particle structure is developed. The influence of grain overlap on product-layer diffusion is quantified. The model predictions show good agreement with the differential reactor data of Borgwardt and Bruce (1986) that include the influences of surface area, temperature, and SO2 partial pressure.
High-Temperature, Short Time Sulfation of Calcium-Based Sorbents: II. Experimental Data and Theoretical Model Predictions
Milne, C.R.; Silcox, G.D. and Pershing, D.W.
I & EC Research, 29, 2202, 1990. Funded by Environmental Protection Agency and ACERC.
The fundamental processes for injection of CaCO3 and Ca(OH)2 for the removal of SO2 from combustion gases of coal-fired boilers are analyzed on the basis of experimental data and a comprehensive theoretical model. Sulfation data were obtained in a 30-KW isothermal dispersed-phase reactor at conditions simulating those of upper-furnace injection. The theoretical model accounts for particle structure, calcination, sintering, sulfation, and heat and mass transfer. Pore diffusion, product-layer diffusion, and sintering appear to be the principle processes that govern the rate of SO2 capture for the hydrate particles of interest for commercial dry sorbent injection.
Calcination and Sintering Models for Application to High-Temperature, Short Time Sulfation of Calcium-Based Sorbents
Milne, C.R.; Silcox, G.D. and Pershing, D.W.
I & EC Research, 29, 139, 1990. Funded by Environmental Protection Agency and ACERC.
To simulate the staged availability of transient high surface area CaO observed in high-temperature flow-reactor data, the rate of calcination of CaCO3 of Ca(OH)2 is described by an empirical modification of the shrinking-core model. The physical model depicts particle decomposition by the shrinking-core mechanism. The subsequent time dependent decrease in CaO reactivity (surface area and porosity) due to sintering is simulated by reducing the grain-center spacing for the matrix of overlapping CaO grains. Information from SEM micrographs and from other physical property measurements of the porous particles is incorporated. This submodel simulates the time dependent availability and reactivity of CaO for a comprehensive model used to study sulfation of CaCO3 and Ca(OH)2 particles at upper-furnace injection conditions.
1989
Calcination and Sintering Models for Application to High-Temperature, Short-Time Sulfation of Calcium-Based Sorbents
Milne, C.R.; Silcox, G.D.; Pershing, D.W. and Kirchgessner, D.A.
Accepted for publication in I & EC Res., 1989. Funded by the US Environmental Protection Agency, ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, and US Department of Energy.
To simulate the staged availability of transient high surface area CaO observed in high-temperature flow-reactor data, the rate of calcination of CaCO3 or Ca(OH)2 is described by an empirical modification of the shrinking-core model. The physical model depicts particle decomposition by the shrinking-core mechanism. The subsequent time dependent decrease in CaO reactivity (surface area and porosity) due to sintering is simulated by reducing the grain-center spacing for the matrix of overlapping CaO grains. Information from SEM micrographs and from other physical property measurements of the porous particles is incorporated. This submodel simulates the time dependent availability and reactivity of CaO for a comprehensive model used to study sulfation of CaCO3 or Ca(OH)2 particles at upper-furnace injection conditions.
1988-1987
Off-Line Process Monitoring of Coal-Derived Liquid Fuels by Computer Assisted Low Mass Spectrometry
Taghizadeh, K.; Davis, B.H.; Windig, W. and Meuzelaar, H.L.C.
Fossil Fuel Analysis by Mass Spectrometry, 1988, T.A. Milne, (ed.), in press. Funded by Commonwealth of Kentucky, Kentucky Energy Cabinet, US Department of Energy and Consortium For Fossil Fuel Liquefaction Science.
Compositional changes of Coal-Derived Liquids (CDL's) during hydrotreatment on fixed bed catalysts can be investigated by Low Voltage (12 eV) MS in combination with multivariate analysis without chromatographic preseparation. Low voltage (12 eV) MS data were obtained and compared under two inlet conditions; MS inlet (1) at ambient temperatures and (2) preheated to about 200ºC. The major trend found in both data sets by Factor analysis was the hydrotreatment effect, namely hydroaromatic (hydrotreater product) vs. aromatic (hydrotreater feed) compounds. A second "time + temperature" trend which reflected the aging of the catalyst as well as the temperature of the hydrotreater reactor was only obtained under ambient inlet temperature conditions. Numerically extracted spectra along the second trend show that more low molecular weight components were found early in the process and also at lower temperatures, whereas more of the higher molecular weight components, primarily alkyl substituted polynuclear aromatics, were obtained later in the process at higher temperatures of the hydrotreater.
A supercritical fluid chromatographic system was constructed to provide separations and fraction collection on a semipreparative scale. Columns packed with silica materials of intermediate particle sizes (30-70 mm) were used to allow dynamic pressure programming with minimum pressure drop of the CO2 mobile phase along the length of the column. A variety of complex coal- and petroleum-derived polycyclic aromatic compound mixtures were fractionated according to the number of aromatic rings using columns packed with an NH2- modified stationary phase bonded on silica particles. The CO2 mobile phase was programmed with an alternating series of linear pressure ramps and isobaric intervals to effect even peak spacing and near base line resolution of compounds of differing ring number in a coal tar. A solvent refined coal heavy distillate and a crude oil were similarly fractionated. Effluents were monitored with an ultraviolet spectrophotometer at 254 nm and a flame ionization detector while fractions were collected in pressurized vessels for subsequent analysis by capillary gas chromatography. Sample capacities of up to 20 mg were possible with this system.
Time Resolved Sulfation Rate Measurement for Sized Sorbents
Milne, C.R. and Pershing, D.W.
Proc. 4th Annual Pittsburgh Coal Conf., 1987. 14 pgs. Funded by ACERC (National Science Foundation and Associates and Affiliates).
The sulfation of raw and sized calcium-based sorbents under high-temperature, short time conditions typical of injection in pulverized coal fired boilers was studied. A 100,000 Btu/hr refractory walled flow reactor was used to obtain isothermal SO2 capture which occurs in the first 30 ms after injection and results from inherent particle size difference between the two sorbent types. In this instance, the hydrate particle size is one-tenth that of the carbonate, and the hydrate capture at Ca/S = 2 is 30% versus 5% for the carbonate.
Beyond approximately 200 ms the sulfation rate was insensitive to particle size, but the rate of SO2 capture increase with the hydrated sorbent was larger than that measured with the carbonate sorbent. This suggests that the ultimate extent of sulfation is also influenced by structural parameters. Ultimate calcium utilization does not appear to be significantly influenced by the calcination rate differences between hydrates and carbonates for particles smaller than 5 um. For large carbonate particles, the calcination delay slightly retards the initial sulfur capture and reduces the ultimate calcium utilization.
Time Resolved Sulfation Rate Measurements for Sized Sorbents
Milne, C.R. and Pershing, D.W.
Proc. 4th Annual Pittsburgh Coal Conf., 1987. 6 pgs. Funding source ACERC (National Science Foundation and Associates and Affiliates).
The sulfation of raw and sized calcium-based sorbents under high-temperature, short time conditions typical of injection in pulverized coal fired boilers was studied. A 100,000 Btu/hr refractory walled flow reactor was used to obtain isothermal SO2 capture data for a carbonate and a hydrate derived from the carbonate as a function of reactor residence time and particle size.
Experimental results confirmed the importance of sorbent type and particle size. The hydrated sorbent was clearly superior to the carbonate. This difference is primarily attributable to a dramatic difference in prompt SO2 capture which occurs in the first 30 ms after injection and results from inherent particle size difference between the two sorbent types. In this instance, the hydrate particle size is one-tenth that of the carbonate, and the hydrate capture at Ca/S = 2 is 30% versus 5% for the carbonate.
Beyond approximately 200 ms the sulfation rate was insensitive to particle size, but the rate of SO2 capture increase with the hydrated sorbent was larger than that measured with the carbonate sorbent. This suggests that the ultimate extent of sulfation is also influenced by structural parameters. Ultimate calcium utilization does not appear to be significantly influenced by the calcination rate differences between hydrates and carbonates for particles smaller than 5 µm. For large carbonate particles, the calcination delay slightly retards the initial sulfur capture and reduces the ultimate calcium utilization.