Slater, PN
1994
A Mathematical Model for the Build-Up of Furnace Wall Deposits
Harb, J.N.; Slater, P.N. and Richards, G.H.
The Impact of Ash Deposition on Coal Fired Plants, Taylor & Francis, Washington, DC, 1994. Funded by ACERC.
A theoretical study was performed to investigate the effect of ash chemistry and non-constant thermal properties on the calculated heat flux through a coal ash deposit. A mathematical model, previously developed to describe the build-up of furnace wall deposits, was used to predict the rate of deposit growth, thermal conductivity, and porosity of the deposit, as well as the heat transfer through the deposit. In this study, a method to predict deposit emittance and absorbance as a function of composition and particle size was added to the deposition model. Simulations showed that the ash chemistry had a significant effect on the thermal and physical properties of the deposit and, consequently, the heat flux through the deposit. Significant differences in the predicted heat flux through the deposit were observed when constant values (not varying with time and/or position) for the deposit emittance and thermal conductivity were assumed. The observed differences are largely due to the inability of the constant properties to adequately predict the resistance of the inner layer of the deposit that significantly affects the heat transfer through the deposit.
1993
Simulation of Ash Deposit Growth in a Pulverized Coal-Fired Pilot Scale Reactor
Richards, G.H.; Slater, P.N. and Harb, J.N.
Energy & Fuels, 7, (6):774-781, 1993. (Also presented at the Annual Advanced Combustions Engineering Research Center Conference, Park City, UT, March 1993. Funded by ACERC.
A model has been developed to relate the deposition behavior of ash under slagging conditions to boiler operating conditions and coal composition data. This model has been incorporated into a comprehensive combustion code and used to investigate the effects of ash deposition rate, thermal conditions, and ash chemistry on slag growth in a pilot-scale combustor. Results for simulated deposits from a coal blend fired at 3.7 MBtu/h showed a relatively high liquid fraction corresponding to denser and presumably stronger deposits. The same coal blend fired at a lower rate produced deposits that were less dense because of the lower temperatures and heat flux levels in the combustor, as well as the lower ash deposition rates. Deposition from a cleaned version of the same blend was also simulated at 3.7 MBtu/h and showed less potential for liquid-phase formation than the uncleaned blend. These results are in qualitative agreement with experimental results and illustrate the importance of operating conditions on deposit formation.
Slater, PN
1994
A Mathematical Model for the Build-Up of Furnace Wall Deposits
Harb, J.N.; Slater, P.N. and Richards, G.H.
The Impact of Ash Deposition on Coal Fired Plants, Taylor & Francis, Washington, DC, 1994. Funded by ACERC.
A theoretical study was performed to investigate the effect of ash chemistry and non-constant thermal properties on the calculated heat flux through a coal ash deposit. A mathematical model, previously developed to describe the build-up of furnace wall deposits, was used to predict the rate of deposit growth, thermal conductivity, and porosity of the deposit, as well as the heat transfer through the deposit. In this study, a method to predict deposit emittance and absorbance as a function of composition and particle size was added to the deposition model. Simulations showed that the ash chemistry had a significant effect on the thermal and physical properties of the deposit and, consequently, the heat flux through the deposit. Significant differences in the predicted heat flux through the deposit were observed when constant values (not varying with time and/or position) for the deposit emittance and thermal conductivity were assumed. The observed differences are largely due to the inability of the constant properties to adequately predict the resistance of the inner layer of the deposit that significantly affects the heat transfer through the deposit.
1993
Simulation of Ash Deposit Growth in a Pulverized Coal-Fired Pilot Scale Reactor
Richards, G.H.; Slater, P.N. and Harb, J.N.
Energy & Fuels, 7, (6):774-781, 1993. (Also presented at the Annual Advanced Combustions Engineering Research Center Conference, Park City, UT, March 1993. Funded by ACERC.
A model has been developed to relate the deposition behavior of ash under slagging conditions to boiler operating conditions and coal composition data. This model has been incorporated into a comprehensive combustion code and used to investigate the effects of ash deposition rate, thermal conditions, and ash chemistry on slag growth in a pilot-scale combustor. Results for simulated deposits from a coal blend fired at 3.7 MBtu/h showed a relatively high liquid fraction corresponding to denser and presumably stronger deposits. The same coal blend fired at a lower rate produced deposits that were less dense because of the lower temperatures and heat flux levels in the combustor, as well as the lower ash deposition rates. Deposition from a cleaned version of the same blend was also simulated at 3.7 MBtu/h and showed less potential for liquid-phase formation than the uncleaned blend. These results are in qualitative agreement with experimental results and illustrate the importance of operating conditions on deposit formation.