Ness, T
1996
Modeling High Temperature Char Oxidation
Reade, W.C.; Morris, K.; Ness, T. and Hecker, W.C.
Proceedings of the Tenth Annual Technical Review Meeting of the Advanced Combustion Engineering Research Center, Salt Lake City, Utah, March 6, 1996. Funded by ACERC.
A char oxidation model that predicts char burnout behavior over a broad range of temperature and oxygen concentration has been developed. The model accounts for variations in intrinsic reactivity and pore structure with char burnout. Intrinsic rates are obtained as a continuous function of char conversion from low-temperature isothermal TGA measurements. A port structure model based on three sizes of pores is included to calculate the effective diffusivity of oxidizer through the particle, which in turn is used to calculate the oxygen concentration profile as a function of particle burnout levels. Since the TGA data are base on reactivity per residual mass of the char sample, the effects of char heterogeneities and surface area evolution are implicit in the intrinsic kinetic, thus eliminating the need to predict surface area evolution which has been a problem in previous models.
Model predictions of high-temperature global rates and mass loss as a function of residence time, oxygen partial pressure, and parent coal rank have been compared with experimental data, both reported in the literature and obtained in our high temperature reactor. Chars tested to date include those from Pittsburgh #8, Pocahontas #3, Illinois #6, Deitz and North Dakota coals. To validate the model's ability to predict the effects of oxygen concentration, Pittsburgh #8 char was oxidized at two different temperatures and five different oxygen concentrations (ranging from 0-15%) in the high temperature reactor. The model predictions fit the experimental data very well for all 10 data pints, with variations ranging between 1 and 7%. Model predictions were also compared to the extensive high-temperature data of Sandi (Hurt and Mitchell, 1992) in order to test the model's ability to predict combustion behavior as a function of parent coal rank. The comparison was made for chars from 5 different coals and the agreement in burning rate and burning time for all five chars was again excellent.
Ness, T
1996
Modeling High Temperature Char Oxidation
Reade, W.C.; Morris, K.; Ness, T. and Hecker, W.C.
Proceedings of the Tenth Annual Technical Review Meeting of the Advanced Combustion Engineering Research Center, Salt Lake City, Utah, March 6, 1996. Funded by ACERC.
A char oxidation model that predicts char burnout behavior over a broad range of temperature and oxygen concentration has been developed. The model accounts for variations in intrinsic reactivity and pore structure with char burnout. Intrinsic rates are obtained as a continuous function of char conversion from low-temperature isothermal TGA measurements. A port structure model based on three sizes of pores is included to calculate the effective diffusivity of oxidizer through the particle, which in turn is used to calculate the oxygen concentration profile as a function of particle burnout levels. Since the TGA data are base on reactivity per residual mass of the char sample, the effects of char heterogeneities and surface area evolution are implicit in the intrinsic kinetic, thus eliminating the need to predict surface area evolution which has been a problem in previous models.
Model predictions of high-temperature global rates and mass loss as a function of residence time, oxygen partial pressure, and parent coal rank have been compared with experimental data, both reported in the literature and obtained in our high temperature reactor. Chars tested to date include those from Pittsburgh #8, Pocahontas #3, Illinois #6, Deitz and North Dakota coals. To validate the model's ability to predict the effects of oxygen concentration, Pittsburgh #8 char was oxidized at two different temperatures and five different oxygen concentrations (ranging from 0-15%) in the high temperature reactor. The model predictions fit the experimental data very well for all 10 data pints, with variations ranging between 1 and 7%. Model predictions were also compared to the extensive high-temperature data of Sandi (Hurt and Mitchell, 1992) in order to test the model's ability to predict combustion behavior as a function of parent coal rank. The comparison was made for chars from 5 different coals and the agreement in burning rate and burning time for all five chars was again excellent.