A model of a bubbling fluidized bed combustor oriented to char mass estimation

Fluidized bed techniques are employed in coal combustion power plants, because they allow for the use of low-quality fuel and result in low pollutant emissions. The most important dynamical difference between fluidized beds and normal combustion chambers, is that the former are characterized by a significant loading of carbon, usually absent in conventional plants. Fluidized beds are remarkably difficult to model, since the process is characterized by a series of complex thermal and mechanical interactions. In this paper, a nonlinear lumped parameter model of a bubbling fluidized bed is presented, which captures the leading dynamics of the process. Furthermore, it is shown that this model can be successfully used to estimate the total carbon load based on an easily accessible plant variable, namely the bed temperature. Estimating the carbon load is of interest for the control of the plant.