Membrane design considerations

A foulinghke problem may occur when condensable vapors are left in the residiie. Condensation may result which in the best case results in blinding of the membrane, and in the usual case, destruction of the membrane module. Dew-point considerations must be part of any gas-membrane design exercise. 

Design Considerations for RO Reverse osmosis plants are typically assembled onto carbon steel or stainless steel frames using permutations of components from the hundreds of individual standard stock items commonly available, including a wide range of membranes, each with their own range of design features and applications. 

Considerable activity has been generated on composite reverse osmosis membranes by Japanese researchers. Patent applications were recently published, for example, covering research at Teijin Ltd. on interfacially formed membranes prepared from polydiallylamines (17) and from amine adducts of trls-(glycidyl) isocyanurate (18). Both types of membranes were formed on micro-porous polysulfone supports. Kurihara and coworkers have developed a composite membrane, designated PEC-1000, which is formed by an... 

In this paper an overview of the developments in liquid membrane extraction of cephalosporin antibiotics has been presented. The principle of reactive extraction via the so-called liquid-liquid ion exchange extraction mechanism can be exploited to develop liquid membrane processes for extraction of cephalosporin antibiotics. The mathematical models that have been used to simulate experimental data have been discussed. Emulsion liquid membrane and supported liquid membrane could provide high extraction flux for cephalosporins, but stability problems need to be fully resolved for process application. Non-dispersive extraction in hollow fib er membrane is likely to offer an attractive alternative in this respect. The applicability of the liquid membrane process has been discussed from process engineering and design considerations. 

The fundamentals of these technologies are described, including membrane polymers and device configurations, as well as complete system design considerations. 

To counteract the typical misoneism of the world food industry, it is necessary to resort to appropriate scaling-up exercises in pilot- or industrial-plant scale to assess precisely the membrane process performance and reliability, as well as its economical feasibility. There are, however, a number of problems that have undoubtedly limited growth in ED membrane sales, like membrane-fouling problems, design considerations, cleanability, investment and membrane replacement costs, and competing technologies, such as NF and IER. 

The achievable fluxes through membranes, J, were designated in [35] as area time yields (ATY, in molm-2s). Figure 12.4 provides an estimation of the current state regarding the possibility of matching the two processes. For a wide range of membranes under consideration, the required ratios of membrane area to reactor volume (Am/Vr) are between 10 and 100 nr1. These values allow to estimate that the diameter of applicable cylindrical tubular reactors should be between 0.04 and 0.4 m. These appear to be reasonable values for industrial applications, and indicate that matching of the two processes under consideration is achievable with currently available membranes. 

Redondo, J. A. and E. Lanari (1997). Membrane selection and design considerations for meeting European potable water requirements based on different feedwater conditions. Desalination, Proc. 1997 Workshop on Membranes in Drinking Water Production, June 1-A, L Aquila, Italy, 113, 2-3, 309-323. Elsevier Science B.V., Amsterdam, Netherlands. 

Membrane and Membrane Design Most membranes are polymers in nature, but some inorganic membranes have become available. The most common membranes are based on polysulfone, cellulose acetate, polyamide, fluoropolymers, and other compounds. Formation of a symmetric membrane structure is an important element in the success of UF/NF membrane separation (16). The other considerations for membrane separation are as follows (1) separation capabilities (retention or selectivity), (2) separation rate (flux), (3) chemical and mechanical stabilities, and (4) membrane material cost. 

A typical NF or RO unit includes raw water pumps, pretreatment, membrane modules, disinfection units, storage, and distribution elements (3). The principal design considerations for NF and RO units are ... 

Huge amounts of liquid byproduct and waste effluents in the fertilizer industry contain various heavy metals, some of which are highly toxic. Cd, Cu, and Zn are commonly encountered in these effluents and are selected for selective removal studies using liquid membrane systems [1-7, 14-17]. Below, experimental and calculated data, obtained for Cd, Cu, and Zn separation, are used for the BAHLM process design considerations. 

Essentially, the same design considerations as discussed for gas diffusion hold true for dialysis with the notable exception that the membranes are different. Whereas gas diffusion uses hydrophobic microporous membranes, dialysis uses hydrophilic membranes such as cellulose-based membranes. A variety of different-molecular-weight-cut-off membranes are also available. 

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