Dispersed plug flow model moments

Dynamic analysis of a trickle bed reactor is carried out with a soluble tracer. The impulse response of the tracer is given at the inlet of the column to the gas phase and the tracer concentration distributions are obtained at the effluent both from the gas phase and the liquid phase simultaneously. The overall rate process consists the rates of mass transfer between the phases, the rate of diffusion through the catalyst pores and the rate of adsorption on the solid surface. The theoretical expressions of the zero reduced and first absolute moments which are obtained for plug flow model are compared with the expressions obtained for two different liquid phase hydrodynamic models such as cross flow model and axially dispersed plug flow model. The effect of liquid phase hydrodynamic model parameters on the estimation of intraparticle and interphase transport rates by moment analysis technique are discussed. 

First Moments. For both of the dispersed plug-flow cases Mi = 0. This means that the center of gravity of the solute moves with the mean speed of the flowing fluid. For the uniform and the general dispersion models, however, this is not always true. If the solute concentration is initially uniform over a cross-sectional plane, it can be shown (A6) that... 

When axial dispersion in the liquid phase is neglected, that pe L L approaching to infinity the moment equations derived by Eroglu 4 are in accordance with the expressions derived by Ramachandran and Smith 5 who have assumed plug flow model for the liquid phase. 

A further generalization of the Glueckauf approximation is suggested by comparison of the moments for the simple linear rate plug flow model (model la) and the general diffusion model with axial dispersion (model 46). One may define an overall effective rate coefficient (k ) which includes both the effects of axial dispersion and mass transfer resistance ... 

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