Hydrodynamics, FBMRs

Hydrodynamics in FBMRs with Permeable Membrane Walls... 

Hydrodynamics in FBMRs with Submerged Membranes Mass Transfer in FBMRs... 

This chapter deals with the recent research efforts on the benefits and pitfalls of FBMRs. Recent studies on the topic, using an experimental or numerical approach, wiU be covered. In Section 2, we cover several techniques to investigate the hydrodynamics of membrane FBRs, including several experimental techniques and numerical models, followed by a number of recent results that have been obtained with these techniques. 

The hydrodynamics in FBMRs consist of the behavior of the emulsion phase, i.e., the mixture of the sohd particles and the interstitial gas, along with the behavior of the gas bubbles. A complete overview of the characteristics and related models for fluidized beds is reported in the excellent book of Kunii and Levenspiel (1991). It is quite accepted that the most difficult FBR to be simulated is a bubbling fluidized bed, where the description of bubble behavior should be taken into account along with the description of soHd movement and reactions occurring on the solid surface. 

A major issue in the modeling of hydrodynamics in FBRs and FBMRs is the large separation of scales that prevails in FBRs (the largest flow structures can be of the order of meters while the particle—gas interactions take place on the scale of millimeters, or even micrometers). To bridge this gap, smaller scale models that take into account the various interactions (gas—particle, particle—particle) in detail are used to develop closure laws which can... 

Especially, the DPM and TFM models have shown a significant contribution to the understanding of the hydrodynamics in FBMRs. However, these models need to be extended with suitable expressions that account for the addition or extraction of gas via membranes, which can be either submerged into the fluidized bed or incorporated in the walls of the bed. The inner workings of these models and their extension with additive/extractive fluxes will be detailed in the following Sections 2.2.1, 2.2.2 and 2.2.3. 

Investigations have been performed into the effect of permeable membrane walls on the hydrodynamics in FBMRs. First of all, an experimental... 

A thorough insight in the heat and mass transfer phenomena in FBMRs is essential to optimize their operation. In the previous section, it has been found that the extractive/additive fluxes through the membranes provide a significant influence on the hydrodynamics, including the formation of stagnant zones where mass transfer hmitations can be anticipated. In order to confirm whether these stagnant zones are really detrimental to the process, noninvasive measurement and simulation techniques have to be devised that allow detection of concentration in the gas and emulsion phase. 

The research efforts discussed in this chapter allow one to design FBMRs taking into account all hydrodynamic imphcations of the membranes, so that processes that incorporate an FBMR can optimally benefit from the integrated separation step. 

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