The importance of fluctuation ratio in the context of uniform gas-solid fluidization has been presented. Correlations in terms of system parameters have been developed for the prediction of fluctuation ratio and its experimental and calculated values have been compared. It has been observed that the fluctuation ratio for the same air mass velocity, decreases (i.e., quality of fluidization improves) with an increase in the bed height by keeping all distributor parameters unchanged. Similarly, an increase in the particle size leads to better fluidization quality. An increase in the free flow area for air through the distributor causes more and more non-uniformity in fluidization.

When a packed bed of particles is subjected to high upward flow of gas such that the weight of the particles just balances the upward thrust by the gas, the particles get freely suspended and these suspended particles start behaving like fluids. This phenomenon is called fluidization and the bed of particles is called fluidized bed. These are commonly used for gas-solid reactions like coal combustion and catalytic cracking of petroleum, etc. A gas-solid fluidized bed is characterized by bubble formation. Bed fluctuation is caused by the collapsing of these bubbles, deteriorating the performance of the bed with an increasing height of the fluidizer and hence, making the operation inefficient. Researchers have always stressed upon the use of promoters in gas-solid fluidization in order to improve its quality by delaying bubble formation and breaking up bubbles to smaller sizes thereby, The IUP Journal of Chemical Engineering, Vol. III, No. 2, 54 2011 reducing the fluctuation (Krishnamurthy et al., 1981; Dutta and Suciu, 1992; Duursma et al., 1994; Kar and Roy, 2000; Kumar and Roy 2002a, 2002b and 2002c; and Kumar, 2003). Balakrishnan and Raja Rao (1975) considered the effect of horizontal disk baffle on fluidized bed pressure drop and minimum fluidizing velocity. Kumar and Roy (2004 and 2007) studied the effect of different baffles on bubbles formed during fluidization. Kumar and Roy (2002c) also studied the effect of different promoters on bed fluctuation while varying distribution open area. Cardoso et al. (2008) carried out experiments on minimum fluidization velocity of fine particles, whereas Xu and Zhu (2006) experimented on effects of different gas types on fluidization of fine particles.

Gas-solid fluidization; Fluctuation ratio; Longitudinal promoters; Disk type promoters, Chemical Engineering Journal, Cross Linked Pva Membranes, Pervaporation Catalytic Membrane Reactor, Membrane Separation Process, Esterification Reactions, Plant Scale Production, Catalytic Membranes, Kinetic Model Equations, Regression Analysis, Pervaporation Reactors.