Momentum equations bubble column reactors

Models considering detailed flow patterns in multi-phase reactors are similar to those presented in Section 13.7 for fluidized bed reactors. The models are based on the Navier-Stokes equations for each of the moving phases. The different phases are assumed to be fully penetrating each other. Interphase mass, momentum, and energy transfer is accounted for. The methods accounting for the fluctuations in the flow field discussed in Chapter 12 for single phase flow can be extended to multi-phase flow. Application to the simulation of a bubble column reactor is illustrated in Example 14.3.6.A. 

The selection and design of a reactor for bench-scale kinetic experiments should be considered case by case. It is important to stress, however, that one should not try to build a bench-scale replica of what is believed to be or is the industrial reactor. Industrial reactors are designed to operate a process in a profitable way, which is not the case for experimental reactors. In industrial reactors heat, mass and momentum transport has to occur in an economically justifiable way, leading in general to temperature, concentration and/or pressure gradients inside the reactor. Also, the hydrodynamics can be rather complicated. Fluidized beds, bubble columns and trickle-flow reactors require model equations that involve several physical parameters, besides the intrinsic kinetic parameters. Empirical... 

Instead of assigning different shear rates, he employed different breakage rate expressions for the two zones. The problem of coupling population balance models with fluid flow models has received some attention recently and coupled PB-CFD models have been developed for a wide variety of processes such as fluidization [70], gas-liquid reactions in bubble columns [71] and nanoparticle synthesis in flame aerosol reactors [72]. Complete description of aggregation in turbulent environments requires simultaneous solution of basic balance equations for mass, momentum, energy and concentration of species present along with population balances for particles/aggregates of different size classes. 

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