Mathematical modelling of sulfur retention in fluidized bed combustors

Altındağ, Hakan
A considerable number of modeling studies for the investigation of sulfur retention in atmospheric bubbling fluidized bed combustors have been carried out and well documented in the literature. Despite 30 years of intensive study of sulfation process in fluidized bed combustors and numerous laboratory studies, there are still many uncertainties and disagreements on the subject. In addition, modeling sulfur retention performance of Turkish lignites with high sulfur, volatile matter and ash contents has not drawn much attention to date. Recent trend in utilization of indigenous lignites in fluidized bed boilers necessitated investigation of pollutant emissions and adaptation of fluidized bed combustion technology to these lignites. In an attempt to achieve this objective, a system model, previously developed and tested for the prediction of the combustion behavior of fluidized bed combustors was extended to incorporate sulfur retention. The predictive accuracy of the model was assessed by applying it to the prediction of the behavior of METU 0.3 MWt ABFBC test rig burning indigenous lignites in their own ashes, and comparing its predictions with measurements taken on the same rig. Sulfur dioxide concentration predictions throughout the combustor were found to be in good agreement with the experimental data except for the small discrepancy between predictions and measurements in the bed section. Measurements and model predictions revealed that recyling enhances calcium utilization significantly by increasing the sorbent residence time leading to higher sulfur retention efficiencies. The system model proposed in this study proves to be a useful tool in qualitatively and quantitatively simulating the processes taking place in an atmospheric fluidized bed combustor.


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Citation Formats
H. Altındağ, “Mathematical modelling of sulfur retention in fluidized bed combustors,” M.S. - Master of Science, Middle East Technical University, 2003.