Fluidized bed modeling

The rise velocity of bubbles is another important parameter in fluidized-bed models, but it can be related to bubble size (and bed diameter, D). For a single bubble, the rise... 

In this section, some analytical solutions of fluidized-bed models are presented. Specifically, model solutions will be given for the case of a gas-phase reactant and a single solid-catalyzed reaction of the form A —> products and bubbling fluidized bed (Type B fluidization). The same analysis holds for a reaction of the form A + B —> products, if the reaction depends only on the concentration of A. Some solutions for the cases of a single reversible reaction, for two reactions in parallel, and two reactions in series will be given as well. 

Fitzgerald, T. J. and Crane S. D. (1980). Cold Fluidized Bed Modeling. Proceedings of the Sixth International Conference on Fluidized Bed Combustion, Atlanta, Georgia. 3, 815. U.S. DOE. 

Most fluidized-bed models include concentration profiles only for the vertical direction. This one-dimensional modeling is acceptable when the reactants are admitted uniformly over the bed cross-section. If, however, reactants are metered into the bed at individual feed points, three-dimensional modeling may become necessary [104-106]. 

Fett. F. N., Burkle, K. J., Dersch, J., Scholer, J., Edelmann, H., and Heimbockel, I. Progress in fluidized bed modelling, Proceedings of 2nd International Symposium on Coal Combustion Science and Technology, China Machine Press, Beijing, pp. 555-566 (1991). 

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. 

We find that the numerical fluidized bed model predicts bubble size and velocity, at ambient pressure and temperature, which agrees with the data. Further in that figure we show the results of three calculations at high pressure (40 atm) and room temperature (293 K) which, when correlated in the same fashion, yield predictions of bubble size and velocity which also agree with the ambient pressure data. This agreement between high... 

Clift, R., An Occamist review of fluidized bed modelling. AIChE. Symp. Ser. 296 89,1 (1993). 

Example 10-5 Catalyst Decay in a Fluidized Bed Modeled as a CSTR... 

Chapter 10 contains a literature survey of the basic fluidized bed reactor designs, principles of operation and modeling. The classical two- and three phase fluidized bed models for bubbling beds are defined based on heat and species mass balances. The fluid dynamic models are based on kinetic theory of granular flow. A reactive flow simulation of a particular sorption enhanced steam reforming process is assessed. 

Extimple 10-6 Cuiatys Oec y iit a Fluidized Bed Modeled as a CSTR v(VHip/c lO-R Dectiv in a Simislu-Thmuslt Transport Reactor Professional Reference Shelf R10.1. Hydrftsen Adsorption... 

Appendix B Constitutive Equations used in Fluidized Bed Modeling... 

Various core-annular models have been developed to describe the gas-solid flow (Horio et al., 1988 Bai et al., 1995 Bolton and Davidson, 1998). The main difference among these models lie in the degree of complexity and in the assumptions associated with simplifications. Core-annular flow structures become dominant in the upper dilute region. Thus, when the dilute flow is predominantly present in the riser, models based on core-annular structures can be applied to reactor models. Kunii and Levenspiel (1990) extended the conventional fluidized bed model (a dense lower region coupled with a freeboard upper region) to cir-... 

Fitzgerald TJ, Crane SD. Cold fluidized bed modeling. Proceedings of 6th International Conference on Fluidized Bed Combustion, III, 1980, p 815. 

Bruinzeel C, Reman GH, van der Laan ETR. Eddy diffusion in particulately fluidized beds model experiments for the design of a large-scale unit. In Proc S5mip on Interaction Between Fluids and Particles. London Instn Chem Engrs, 1962, pp 120-126. 

Some Features of the Fluidization and Transport of Solids Heat Transfer in Fluidized Beds Modeling of Fluidized Bed Reactors... 

FIGURE S.35 Comparison of different fluidized bed models for a first-order reaction A P according to Ref. [18]. 

In a general case of nonlinear kinetics, the fluidized bed model is solved numerically with an algorithm suitable for differential algebraic systems. The calculation procedure for fluidized beds with the Kunii-Levenspiel model involves numerous steps, as evidenced by the treatment. As a summary, the path from the minimum fluidization quantities (emf, Wfn() to the reactor model is presented in Table 5.6. The superficial velocity (wo) and the physical parameters are assumed to be constant. 

Several parameters are included in the packed and fluidized bed models. The values of the parameters have to be determined experimentally or estimated theoretically to enable the use of balance equations in the design of real reactors. 

TABLE 5.6 Calculation Procedure for Simulation of a Fluidized Bed Model... 

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