Gas Flow Division and Bed Expansion

The distribution of gas flow in the fluidized bed is important for the analysis of the fundamental characteristics of transport properties in the bed. One common method to estimate the gas flow division is based on the two-phase theory of fluidization, which divides the superficial gas flow in the bed into two subflows, i.e., bubble phase flow and emulsion phase flow, as shown in Fig. 9.14. According to the theory, the flow velocity can be generally expressed as 

In dense-phase fluidization, the expansion of the bed is caused by two factors emulsion phase expansion and presence of bubbles. Thus, the bed expansion height Hf can be expressed as a linear addition of the contributions of these factors 

For the emulsion phase expansion of Group A particles, //em can be correlated by [Abrahamsen and Geldart, 1980b] 

Equation (9.45) assumes that there is no velocity effect on Hem. 

When operated under high-temperature (up to 1,258 K) conditions, the bed expansion can be estimated by [Cai et al., 1993] 

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