Fluidization continuum description

Gidaspow, D., Multiphase Flow and Fluidization Continuum and Kinetic Theory Descriptions . 

The computer model is based upon a continuum description of fluidization in coal gasification reactors. In general, fluidized flows are dominated by specific physicochemical processes and, hence, require particular theoretical representations. For example, in the heavily loaded gas-particle regime appropriate to fluidization, the solid particles dominate the transport of momentum and energy. This aspect of fluidization is reflected in the mathematical descriptions which have been used in the fluidized bed model. 

Gascon J, Tellez C, Herguido J, Jakobsen HA, Menendez M (2006) Modehng of Fluidized Bed Reactors With Two Reaction Zones. AIChE J 52(ll) 3911-3923 Geldart D (1973) Types of gas fluidization. Powder Technology 7 285-292 Gidaspow D (1994) Multiphase Plow and Fluidization-Continuum and Kinetic Theory Descriptions. Academic Press, Harcourt Brace Company, Publishers, Boston... 

Gidaspow D Multiphase flow and fluidization continuum and kinetic theory descriptions with applications, Boston, 1994, Academic Press. 

The Eulerian continuum approach, based on a continuum assumption of phases, provides a field description of the dynamics of each phase. The Lagrangian trajectory approach, from the study of motions of individual particles, is able to yield historical trajectories of the particles. The kinetic theory modeling for interparticle collisions, extended from the kinetic theory of gases, can be applied to dense suspension systems where the transport in the particle phase is dominated by interparticle collisions. The Ergun equation provides important flow relationships, which are useful not only for packed bed systems, but also for some situations in fluidized bed systems. 

Chapter 4 contains a summary of the basic theory of granular flow. These concepts have been adopted describing particulate flows in fluidized bed reactors. The theory was primarily used for dense bed reactors, but modified closures of this type have been employed for more dilute flows as well. Compared to the continuum theory presented in the third chapter, the granular theory is considered more complex. The main purpose of introducing this theory, in the context of reactor modeling, is to improve the description of the particle (e.g., catalyst) transport and distribution in the reactor system. 

The multi-fluid models discussed in Chap. 3 have been employed extensively describing the behavior of cold flow and reactive flow systems in multiphase reactors. However, for gas-solid fluidized bed systems, and in particular for dense systems, it has been found that the dispersed phase behavior cannot be captured without an extended description of the pressure tensor closure. The first extensions of the dilute continuum mechanical two-fluid model concept included a very rough approximation of the solid phase collisional pressure in terms of a semi-empirical correlation for the modulus of elasticity and a constant representative particle fluid viscosity. This type... 

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