Dynamic behavior of circulating fluidized bed boiler furnace.

摘要

A dynamic mathematical model has been developed for the prediction of the transient temperature response of circulating fluidized bed (CFB) combustors. The model also predicts the corresponding transient response of carbon and oxygen concentrations in the bed.; The furnace and the rest of the CFB is divided into a number of cells. Gas-solid mixing and flow in the fast bed section is described by a core-annulus structure. The model includes mass balances of oxygen and carbon and energy balances as well as submodels for the gas-solid flow structure, combustion and heat transfer from the bed to both the refractory walls and to a waterwall located in the fast bed section. The heat transfer submodel also incorporates the thermal inertia of the refractory walls which showed a significant effect on the transient temperature response of a CFB.; The model is structured in modules such that new submodels for emissions, particle size distribution, attrition, etc., may be added and existing submodels may be replaced as the various processes become better understood.; The model was successfully validated against data from tests performed on a 0.3 MWt CFB pilot plant. The model predictions agreed very well with the experimental data for temperature distribution, transient temperature response, transient oxygen response and voidage profile. Due to the nature of solids sampling only a few data points for carbon concentration were found. This does not give a transient profile but it does allow for validation of the quasi-steady state carbon concentration predicted by the model.