Dynamics of Promoted Gas-Solid Fluidized Bed using Secondary
Fluidizing Medium

Abstract

Many thermal power generating units are, of late, increasingly following the concept of circulating fluidized bed, and using secondary air in the fluidizer for the improvement of quality of fluidization and combustion, of course without understanding the real hydro-dynamics involved. Owing to the scarcity of good quality of coal and an ever-increasing demand for electricity for the complete combustion of low grade coal, the introduction of secondary air is one of the best solutions. Several sponge iron production units have been entangled with the problem of converting carbon into carbon dioxide.Extensive experimental work and industrial applications provide unambiguous evidence that it is precisely these fluctuations that are responsible for extremely high values of effective coefficients of heat and mass transport to determine the dynamic properties of disperse mixtures. In general, large scale fluctuations strongly depend on various external conditions such as geometric properties of the disperse flow and quality of the gas distribution in fluidized beds. Whereas the small scale fluctuations depend merely on the local hydrodynamic situations and more inherent to macroscopically uniform states with no inner circulation and bubbles.