Membrane design

UF Membranes Design of UF membranes prizes high retention, hydrolytic stabihty, and good process flux. Since fouling is the principal impediment to flux, and membranes which are hydrophilic gener ly foul less rapidly, there is competition between the truly stable hydrophobic membranes and the less-fouhng-prone hydrophilic ones. 

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. 

Membranes will also remove some of the water vapor. Depending upon the stream properties, a membrane designed to treat CO2 to pipeline specifications may also reduce water vapor to less than 7 Ib/MMscf. Often, however, it is necessary to dehydrate the gas downstream of the membrane to attain final pipeline water vapor requirements. 

In addition, the use of water-wall design lowered gas exit temperatures, which increased boiler efficiency and reduced the potential for rapid degradation of refractory surfaces caused by the buildup of slag (molten ash). All larger WT boilers today employ water-wall membrane designs in their construction. 

The opportunities for biomedical membrane design and synthesis in the pol3q>hosphazene system are wide ranging. So far, only preliminary explorations have been undertaken, and only a brief outline will be given here. 

Like evaporators, RO works on most plating baths and rinse tanks. Most RO systems consist of a housing that contains a membrane and feed pump. There are four basic membrane designs plate-and-frame, spiral-wound, tubular, and hollow-fiber. The most common types of membrane materials are cellulose acetate, polyether/amide, and polysulfones.29... 

Figure 10.13 Trade-offs in membrane design for gas separation...

DuPont research into high current density and the associated effect on membrane and electrolyser performance has been underway for a decade. It has been the area of greatest concentration for the company during the last 5 years. Studies at the DuPont Experimental Station and Fayetteville Nafion Customer Service Laboratories resulted in polymer innovation and new membrane designs. This work has also identified interactions between membranes and electrolysers... 

Zhang, L., Ma, C. and Mukerjee, S. 2003. Oxygen permeation studies on alternative proton exchange membranes designed for elevated temperature operation. Electrochimica Acta 48 1845-1859. 

Guizard, C., F. Legault, N. Idrissi, L. Cot and C. Gavach. 1989. Electronically conductive mineral membranes designed for electroultrafiltration. J. Membrane Science 41 127-42. 

The SDI- - of a water is the accepted criterion of its quality for RO conversion and some SDI s of water around the world are given on Table II. The manufacturers usually require values of waters reaching permeators to have an SDI below 3 if they are to warranty their membrane design life. This requirement of seawater for RO conversion is accomplished through pretreatment. The quality of the raw seawater determines the need for, and the specific type of pretreatment required to produce the water quality requisite to satisfy a specific permeator manufacturer s requirements. 

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... 

Membrane design and fabrication requires more optimization than the synthesis of the right type of polymer. For example, those phosphazene polymers that contained the highest ratios of methylamino groups were too brittle to be used as membranes (because of the high glass-transition temperatures) and too soluble in aqueous media. However, the polymers could be made insoluble in water by radiation cross-linking as shown in reaction (54). 

Another type of membrane designed as an artificial skin coating for bums also exploits the high permeability of siloxane polymers.18,203 The inner layer of the membrane consists primarily of protein and serves as a template for the regenerative growth of new tissue. The outer layer is a sheet of silicone polymer, which not only provides mechanical support, but also permits outward escape of excess moisture while preventing ingress of harmful bacteria. 

In the process shown in Figure 8.21, a two-step membrane design is used to reduce the cost of recompressing the hydrogen permeate stream to the very high... 

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