Transport phenomena in packed bed

E.U. Schlunder, Transport phenomena in packed bed reactors, in Chemical Reactor Engineering Reviews—Houston, ACS Symposium 72, American Chemical Society, Washington, DC, 1978. 

General Models Describing Transport Phenomena in Packed-Bed Catalytic Membrane Tubular Reactors... 

Schlunder EU. Transport phenomena in packed bed reactors. In Luss D, Weekman Jr VW, editors. Chemical Reaction Engineering Reviews— Houston. Washington, DG American Chemical Society 1978. 

Bavarian and Fan [3, 4] reported a similar phenomenon occurring in a three-phase fluidized bed. In their case, the hydraulic transport of a packed bed occurred at the start-up of a gas-liquid-solid fluidized bed. Although the cause was different from the case reported in the present study, similar phenomena were observed in both cases. 

The direct experimental verification of the computed flow field requires noninvasive measurements of velocity components inside the packed tube. One very promising technique for this is magnetic resonance (MR) as described in a recent review by Gladden (2003). She showed pictures of 3D MR visualization of axial velocity for flow of water in packings of spheres, and her group has used MR to connect the 3D structure of a packed bed to the transport phenomena in... 

This review contains a great deal of information about the thermochemical conversion chemistry. The reader is referred to the original paper (Appendix B) for details. Here follows some of the most important findings on the heat and mass transport phenomena in a packed bed during thermochemical conversion. 

Figure 2. Transport phenomena in a catalytic packed bed reactor on different levels.

Packed columns have been used in chemical industry for more than a century. The packing in a packed column provides a large surface area over which the gas contacts the liquid and the gas-to-liquid (and vice versa) mass transfer occurs (Fig. 3). As a result, the gas-liquid mass transfer process in a packed column is very efficient. Research and development on packed column has received much attention. One of the earlier and original literatures reported by Leva covers the principles of gas-liquid mass transfer in a packed bed, as well as packed column design and column internals. Recent reported literatures on gas absorption in a packed column from Fair et al., Strigle, and Billet are excellent references on transport phenomena in a packed column and packed column design. 

Numerical simulation results of batch and continuous drying models for slices of peppers in packed beds were presented in this work. The reported models were based on differential mass and energy balances in the dryer along with kinetic equations describing transport phenomena in individual particles and product quality deterioration. The shrinkage problem was... 

The present chapter provides an overview of several numerical techniques that can be used to solve model equations of ordinary and partial differential type, both of which are frequently encountered in multiphase catalytic reactor analysis and design. Brief theories of the ordinary differential equation solution methods are provided. The techniques and software involved in the numerical solution of partial differential equation sets, which allow accurate prediction of nonreactive and reactive transport phenomena in conventional and nonconventional geometries, are explained briefly. The chapter is concluded with two case studies that demonstrate the application of numerical solution techniques in modeling and simulation of hydrocar-bon-to-hydrogen conversions in catalytic packed-bed and heat-exchange integrated microchannel reactors. 

The performance of packed bed reactors may be influenced and sometimes even controlled by transport phenomena in the voids between the particles as well as inside the particles. This paper is restricted to transport phenomena mainly between the particles. 

The models proposed by Wu et al. [36] and by Lin and Leu [45] refer to continuous conversion processes by immobilized bacteria the first to a fixed mixed culture entrapped into PVA beads operated in a fluidized bed, and the second to BAC of P. luteola operated in a packed bed. Results of these models highlight the role of mass transport phenomena and biophase granule size on reactor performance. 

First of all, the physical structure of the packed bed in the conversion system is defined. The fuel bed structure can be divided into three phases, namely the interstitial gas phase, the intraparticle solid phase, and the intraparticle gas phase. By means of this terminology it is easier to address certain mass and heat transport phenomena taking place on macro and micro scale inside the packed bed during the thermochemical conversion, see Figure 8. 

Appendix B includes a review and a classification of conversion concepts. It also investigates the potentials to develop an all-round bed model or CFSD code simulating the conversion system. This review also contains a great deal of information on the heat and mass transport phenomena taking place inside a packed bed in the context of PBC of biomass. The phenomena include conversion regimes, pyrolysis chemistry, char combustion chemistry, and wood fuel chemistry. The main conclusions from this review are ... 

Edward G. Jefferson, Future Opportunities in Chemical Engineering Eli Ruckenstein, Analysis of Transport Phenomena Using Scaling and Physical Models Rohit Khanna and John H. Seinfeld, Mathematical Modeling of Packed Bed Reactors Numerical Solutions and Control Model Development... 

The rate-based models usually use the two-film theory and comprise the material and energy balances of a differential element of the two-phase volume in the packing (148). The classical two-film model shown in Figure 13 is extended here to consider the catalyst phase (Figure 33). A pseudo-homogeneous approach is chosen for the catalyzed reaction (see also Section 2.1), and the corresponding overall reaction kinetics is determined by fixed-bed experiments (34). This macroscopic kinetics includes the influence of the liquid distribution and mass transfer resistances at the liquid-solid interface as well as dififusional transport phenomena inside the porous catalyst. 

In terms of organization, the text has two main parts. The first six chapters constitute generic background material applicable to a wide range of separation methods. This part includes the theoretical foundations of separations, which are rooted in transport, flow, and equilibrium phenomena. It incorporates concepts that are broadly relevant to separations diffusion, capillary and packed bed flow, viscous phenomena, Gaussian zone formation, random walk processes, criteria of band broadening and resolution, steady-state zones, the statistics of overlapping peaks, two-dimensional separations, and so on. 

Supercritical viscosity lies in between the viscosity of liquids and gases. For this reason, supercritical fluids exhibit more favourable hydrodynamic properties than do liquids. Also, the low surface tension of SFs allows them to readily penetrate porous solids and packed beds. The viscosity of SFs, like that of conventional fluids, is temperature-dependent however, while pressure has little effect on the viscosity of fluids, it exerts a strong influence on that of SFs. As a result, increased pressures lead to increased supercritical viscosity and hence to diminished solute diffusivity and hindered transport phenomena, but also, most often, to increased solubility through decreased density. 

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