Experimental Apparatus, Materials and Instrumentation

The hydrodynamics of fast fluidization depends greatly on the boundaries of the retaining vessel, e.g., the wall, the inlet and the outlet. Inasmuch as different geometric structures were employed by different investogators in their experimental apparatus, inconsistencies in the resulting data are unavoidable. This will be the main topic for the present section. 

In measurement and visualization of gas-solid flow in fast fluidization, various techniques have been developed and used, such as pressure gradient, pressure fluctuation, capacitance probe, optical fiber probe, momentum probe, laser Doppler velocimeter, night-television, and video camera. The resulting data on local gas and solid velocity, solids concentration and its 

The main features of this type of apparatus, shown in Fig. 5a (Li et al, 1978), are  

As a result, gas velocity and solids circulation rate can be adjusted separately and independently. For any given gas velocity and solids circulation rate, there is only a unique equilibrium solids inventory in the fast fluidized column, which determines the height of the dense-phase region at the bottom. 

As Fig. 5b (Li et ai, 1984) shows, there is no intermediate solids hopper as for type A, and the solids rate device is used only for measurement rather than for control. In operation, solids circulation rate is determined essentially by gas velocity. Therefore, gas velocity and solids circulation rate could not be adjusted independently. Solids circulation rate follows what an operating velocity produces at whatever solids inventory the system was initially filled with. Owing to the absence of an intermediate hopper, the initial solids inventory could influence directly axial voidage profile, that is, the position of the inflection point changes with the initial solids inventory in the system. 

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