| Circulating fluidized bed combustion of fossil fuels has many advantages over the conventional combustion systems, such as effective NO;Although the benefits of staging are well appreciated, due to complexity of the fluidization process, optimization of staging is yet to be completed. For example, Basu (1991) notes that the amount of staged air varies between 30-70% of the total combustion air from one manufacturer to the other. This example shows the requirement for detailed studies for better utilization of secondary air in CFB systems.;In this work the most effective parameters of staging are considered as the mode, the height and the amount of secondary air, and the individual effects of these parameters on the overall hydrodynamics of a CFB riser is sought. Experimentally, the particle velocity profiles in the lower sections, and pressure profiles throughout a cold type CFB riser are measured under varying secondary air parameters. Computationally, jet emerging patterns and the effect of mode and intensity of SA jets on the gas flow patterns in the riser are studied using 3-D computational fluid dynamics (CFD) approach. The knowledge obtained from experimental and computational work is used in constructing a two dimensional core-annular hydrodynamic model for CFB risers. The hydrodynamic model accounts for the effects of individual parameters of secondary air injection. |
