Mathematical modeling of nox emissions in bubbling fluidized bed combustors

Afacan, M. Onur
A comprehensive model, previously developed and tested for prediction of behavior of continuous fluidized bed combustors is extended to incorporate NOx formation and reduction reactions and applied to the simulation of METU 0.3 MWt Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) burning lignites with high volatile matter in their own ashes. The predictive accuracy of the model was assessed by comparing its predictions with measurements taken previously on the same rig. Favorable comparisons are obtained between the predicted and measured temperatures and concentrations of gaseous species along the combustor. Results show that determination of partitioning of coal nitrogen into char nitrogen and volatile nitrogen, and release of volatile nitrogen along the combustor are found to be the most important parameters that affect NOx formation and reduction in bubbling fluidized bed combustors. 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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Alagöz, Düriye Ece; Selçuk, Nevin; Department of Chemical Engineering (2006)
Simultaneous solution of the conservation equations for energy and chemical species in conjunction with radiative transfer equation was carried out by coupling a previously developed and tested system model of fluidized bed combustion (FBC) to an existing radiation model. The predictive accuracy of the coupled code was assessed by applying it to 0.3 MWt METU Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) Test Rig burning lignite in its own ash and comparing its predictions with the measured temperatur...
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Guruz, GA; Uctepe, U; Durusoy, T (Elsevier BV, 2004-06-01)
Pyrolysis, as a first step in all thermochemical coal conversion processes, has been investigated in detail over the years in order to evaluate the kinetic data and to establish reliable models for the complex reaction scheme. Since coal pyrolysis is not a single reaction but rather a multiplicity in different time intervals for isothermal pyrolysis, or in different time and temperature intervals for the case of heat-up, any set of parameters cannot be expected to represent data accurately over a wide range...
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Effects of particle size, particle density, gas inlet diameter and static bed height on the stability of operation in conical spouted beds were investigated through analyses of information entropy of pressure fluctuations. In this respect, the maximum information entropy of pressure fluctuations was used as a stability criterion. The results showed that stability of the bed increases with an increase in the maximum entropy. The maximum information entropy of pressure fluctuations increases with increasing p...
Numerical simulation of radiating flows
Karaismail, Ertan; Selçuk, Nevin; Department of Chemical Engineering (2005)
Predictive accuracy of the previously developed coupled code for the solution of the time-dependent Navier-Stokes equations in conjunction with the radiative transfer equation was first assessed by applying it to the prediction of thermally radiating, hydrodynamically developed laminar pipe flow for which the numerical solution had been reported in the literature. The effect of radiation on flow and temperature fields was demonstrated for different values of conduction to radiation ratio. It was found that ...
Experimental investagation of drag reduction effects of polymer additives on turbulent pipe flow
Zeybek, Şerife; Uludağ, Yusuf; Department of Chemical Engineering (2005)
Since the discovery of the drag reduction effects of even small amount of macromolecules in solutions in turbulent pipe flows, there have been many experimental and theoretical studies in order to understand mechanisms behind this phenomenon. Theories have been proposed based on the observations on the change in the characteristics of the turbulent flow near the pipe wall where friction of the momentum transfer between the flow and the conduit takes place. In this study drag reduction in fully developed tur...
Citation Formats
M. O. Afacan, “Mathematical modeling of nox emissions in bubbling fluidized bed combustors,” M.S. - Master of Science, Middle East Technical University, 2005.