Membrane process design

Depth filters are usually preferred for the most common type of microfiltration system, illustrated schematically in Figure 28. In this process design, called "dead-end" or "in-line" filtration, the entire fluid flow is forced through the membrane under pressure. As particulates accumulate on the membrane surface or in its interior, the pressure required to maintain the required flow increases until, at some point, the membrane must be replaced. The useful life of the membrane is proportional to the particulate loading of the feed solution. In-line microfiltration of solutions as a final polishing step prior to use is a typical apphcation (66,67). 

FT conditions for their HSOD membrane. A conceptual process design indicated that application of SOD membranes in the FT reaction could be economically viable [54]. 

Evaluation of design options. Costs are required to evaluate process design options for example, should a membrane or an adsorption process be used for purification ... 

Thomas, D.G., and Mixon, W.R., "Effect of Axial Velocity and Initial Flux on Flux Decline of Cellulose Acetate Membrane in Hyperfiltration of Primary Sewage Effluents," I EC Process Design and Development 11, 339-343 (1972). 

Thomas, D.G. and Watson, J.S., "Reduction of Concentration Polarization of Dynamically Formed Hyperfiltration Membranes by Detached Turbulence Promoters", I EC Process Design and Develop., 1968, T, July, 397. 

Cmcial factors in designing membrane reactors are (1) high area for high mass transfer, (2) membranes that have a high permeabihty to only one species, (3) membranes that are catalytic, and (4) membranes that have no holes that leak reactants from one compartment to the other. With any process the reactor wiU not function properly if aU these criteria are not met, and for oxidation reactions ary leaks between compartments can be disastrous. 

The process design principles of SLM, non-dispersive extraction, and hybrid hquid membrane systems need to be understood through bench scale experiments using feed solution of practical relevance. While the economic analysis of an ELM process can be performed from small scale experiments, such an analysis is difficult for other LM systems. In particular, availability and cost of hollow fiber membranes for commercial application are not known apriori. A simple rule of thumb for cost scale-up may not be apphcable in the case of an HE membrane. Yet we feel that the pilot plant tests would be adequate to make realistic cost benefit analysis of a liquid membrane process, since the volume of production in )8-lactam antibiotic industries is usually low. 

Once process design is complete and each of the process steps characterized, the process is ready for scale-up to pilot or manufacturing scale. A spreadsheet template for scale-up calculations is important and provides a mass balance of buffer volumes, column volumes, priming volumes, product volumes, and waste volumes as well as the tank size and column size. Product volumes can be expressed relative to column volume or can be calculated from a constant concentration, depending on the process step. In addition, starting volumes and titers of conditioned medium as well as step yields and gel or membrane capacity are necessary to cal-... 

We have another purpose in studying the temperature dependence of the rate of aggregation. It may be expected that the close approach of vesicles is the first stage in their fusion. The process of membrane fusion is known to be sensitive to temperature (14,15,16). In order to elucidate the temperature dependence of the rate of fusion per se, we have first to determine the temperature dependence of the process of close approach. We provide here light-scattering measurements which were designed to test our predictions for the aggregation of sonicated... 

Membrane processes offer an alternative approach to natural gas dehydration and are being developed by a number of companies. Membranes with intrinsic selectivities for water from methane of more than 500 are easily obtained, but because of concentration polarization effects, actual selectivities are typically about 200. Two possible process designs are shown in Figure 8.33. In the first... 

Electrodialysis equipment and process design The performance of electrodialysis in practical applications is not only a function of membrane properties but is also determined by the equipment and overall process design. As far as the stack design is concerned there are two major concepts used on a large scale. One is the sheet-flow concept, which is illustrated in Figure 5.3 and the other is the so-called tortuous path concept, which is illustrated in Figure 5.5. 

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