A. Nikolopoulos

Optimization of Computational Performance and Accuracy in 3‐D Transient CFD Model for CFB Hydrodynamics Predictions

This work aims to present a pure 3‐D CFD model, accurate and efficient, for the simulation of a pilot scale CFB hydrodynamics. The accuracy of the model was investigated as a function of the numerical parameters, in order to derive an optimum model setup with respect to computational cost. The necessity of the in depth examination of hydrodynamics emerges by the trend to scale up CFBCs. This scale up brings forward numerous design problems and uncertainties, which can be successfully elucidated by CFD techniques. Deriving guidelines for setting a computational efficient model is important as the scale of the CFBs grows fast, while computational power is limited. However, the optimum efficiency matter has not been investigated thoroughly in the literature as authors were more concerned for their models accuracy and validity. The objective of this work is to investigate the parameters that influence the efficiency and accuracy of CFB computational fluid dynamics models, find the optimum set of these paramet...

Fluidized Bed Combustion of Solid Biomass for Electricity and/or Heat Generation

Fluidised bed combustion (FBC) technology was developed in the 1970s in order to exploit the energy potential of high-sulphur coals in an environmentally acceptable way. The FBC technology was soon expanded for biomass and other low-grade fuels, which have typically large variations in fuel properties. The benefit of the FBC is the large amount of bed material compared with the mass of the fuel (98 vs 2%) and, thus, the large heat capacity of the bed material that stabilises the energy output caused by variations in fuel properties. Moreover, by selecting reagents as bed material and controlling the bed temperature, the emissions of pollutants can be controlled. In the last two decades, rapid progress has been achieved in the application of FBC technology to power plants up to intermediate capacities, caused by the increasing demands for fuel flexibility, stringent emission control requirements, stable plant operation and availability. Especially concerning the fuel range; there is a definite trend to widen the range of biomass fuels and waste fractions. The aim of this chapter is to review critically the technical requirements of biomass and/or waste combustion in FBCs, the operational problems, the needs for emissions control and the ash handling issues.