Modeling of Reactive Flows in Fluidized Beds

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 

---

Step algorithm was employed for the solution of an unsteady two-fluid granular flow model [136], The latter semi-implicit procedure has also been extended in order to simulate reactive flows in fluidized beds [138],... 

Xie, N., Battaglia, F., Fox, R.O. Simulations of multiphase reactive flows in fluidized beds using in situ adaptive tabulation. Combust. Theory Model. 8, 195-209 (2004)... 

Chao Z, Wang Y, Jakobsen JP, Femandino M, Jakobsen HA (2011) Derivation and validation of a binary multi-fluid Eulerian model for fluidized beds. Chem Eng Sci 66 3605-3616 Chao Z (2012) Modeling and simulation of reactive three-phase flows in fluidized bed reactors appUcation to the SE-SMR process. Doctoral thesis. The Norwegian Univerity of Science and Technology, Trondheim... 

Chao Z (2012) Modeling and simulation of reactive three-phase flows in fluidized bed reactors application to the SE-SMR process. Doctoral thesis, the Norwegian Univerity of Science and... 

Lindborg H (2(X)8) Modeling and simulation of reactive two phase flows in fluidized beds. Doctering thesis, the Norwegitm University of Science and Technology, Trondheim, Norway Lun CKK, Savage SB (1986) The effect of an impact velocity dependent coefficient of restitution on stresses developed by sheared granular materials. Acta Mechanica 63 15-44... 

Lathouwers D, Bellan J (2001) Modelling of dense gas-solid reactive mixtures applied to biomass pyrolysis in a fluidized bed. Int Journal of Multiphase Flow 27 2155-2187... 

In this section the application of multiphase flow theory to model the performance of fluidized bed reactors is outlined. A number of models for fluidized bed reactor flows have been established based on solving the average fundamental continuity, momentum and turbulent kinetic energy equations. The conventional granular flow theory for dense beds has been reviewed in chap 4. However, the majority of the papers published on this topic still focus on pure gas-particle flows, intending to develop closures that are able to predict the important flow phenomena observed analyzing experimental data. Very few attempts have been made to predict the performance of chemical reactive processes using this type of model. 

In the literature numerous two-fluid models of different complexity have been proposed to predict the fluidized bed reactor cold flow and reactive flow behaviors. Four decades ago emphasis was placed on the modeling of the velocity fluctuation co-variance terms in the dispersed particle fluid phase momentum equations. The early one-dimensional models were normally closed by an elasticity modulus parameterization for the particle phase collisional pressure and a constant viscosity parameter for the corresponding shear stresses. Later, with the improved computer memory and speed capacities, multi-dimensional flow models and more advanced model closures were developed based on the kinetic theory of granular flow (KTGF). Moreover, the... 

---