m = moexp(E/RT) (6)The magnitude of the activation energy, E, depends on the activation energy for flow and the dependence of the numbers of flowing molecules on temperature, resulting in moving through a material transition temperature. The activation energy may therefore change with temperature and different gradients may be shown in an Arrenius plot.Gluckman [8] performed deluidization experiments using a plethora of materials, including copper shot, poly-ethylene beads, poly-propylene particles, poly-ethylene terephthalate particles, and glass spheres. It was found that for a given material a certain gas temperature existed which, when underneath, the bed could always be fluidized at the minimum fluidization velocity, Umf,. This temperature was called the minimum sintering temperature, Ts. Above this temperature, a higher fluidizing velocity, Umfs, was needed to fluidize the bed. The data that was collected correlated to a linear function between velocity and temperature: Umfs = B + AT (7)where A and B are constants. Also, it was concluded that there is most likely an influence of bed height.Siegell [2] conducted defluidization tests on several types of particles and based his results in terms of the excess air velocity (Umfs - Umf) needed to keep the bed fluidized and the excess temperature, (T - Ts). It was found that there was a linear relationship between these two parameters and Siegell also reported that increasing the bed height led to the tendency to defluidize.The conclusion in the study of sintering in fluidized beds is that the effect of temperature is the dominant factor that can result in defluidization of the system. This correlation is quite different in respect to effect of temperature on dynamic liquid bridge forces, where higher temperatures and reduced viscosity lead to weaker forces.References:1.M.J. Gluckman, J. Yerushalmi, A.M. Squires, in: ...
