MODELING OF LIGNITE COMBUSTION IN ATMOSPHERIC FLUIDIZED-BED COMBUSTORS .1. SELECTION OF SUBMODELS AND SENSITIVITY ANALYSIS

The application of a specific model to lignite combustion in small and medium-sized combustors presents the initial difficulty of having to choose from the different submodels proposed in the literature, where some important discrepancies still exist. Therefore, in this work a sensitivity analysis of the combustion efficiency predictions of the different hypotheses, equations, and parameters defining the different submodels has been carried out. Thus, it has been found that the hypotheses related to the gas hydrodynamics exercise an important effect on the predictions. The same occurs when modifying parameters or equations referring to the reactivity of the char, or to the fines elutriation to the freeboard. However, those corresponding to the devolatilization type equations for the heat and mass transfer around particles, or the parameters which include these equations, have no significant effect on the efficiency predictions.