Membranes industrial applications

These predictions were made for 200 um membranes. Industrial application of this technology will require the use of membranes which are two orders of magnitude thinner. In order to use the model to predict facilitation factors for thinner membranes, it is necessary to determine whether the reaction equilibrium assumption still applies. The parameter (tanh )/ has a value of 0 if the system is diffusion limited and 1 if the facilitated transport system is reaction rate limited. At a thickness of Ipm, the value of (tanh X)/X is of the order 10 , which implies that the system is diffusion limited and that the simplified analytical model can be used to predict facilitation factors. If the solubility of HjS, the pressure and temperature dependence of the equilibrium constant and the diffusion coefficients are known, then F could be estimated at industrial conditions. 

Pervaporation is a relatively new process with elements in common with reverse osmosis and gas separation. In pervaporation, a liquid mixture contacts one side of a membrane, and the permeate is removed as a vapor from the other. Currendy, the only industrial application of pervaporation is the dehydration of organic solvents, in particular, the dehydration of 90—95% ethanol solutions, a difficult separation problem because an ethanol—water azeotrope forms at 95% ethanol. However, pervaporation processes are also being developed for the removal of dissolved organics from water and the separation of organic solvent mixtures. These applications are likely to become commercial after the year 2000. 

Z. Amjad, ed.. Reverse Osmosis Membrane Technology, Water Chemistry and Industrial Applications, Van Nostrand Reiohold, New York, 1993. 

Economics Microfiltratiou may be the triumph of the Lilliputians nonetheless, there are a few large-industrial applications. Dextrose plants are veiy large, and as membrane filtration displaces the precoat filters now standard in the industry, very large membrane microfiltratiou equipment will be built. 

Filtration is a fundamental unit operation that, within the context of this volume, separates suspended particle matter from water. Although industrial applications of this operation vary significantly, all filtration equipment operate by passing the solution or suspension through a porous membrane or medium, upon which the solid particles are retained on the medium s surface or within the pores of the medium, while the fluid, referred to as the filtrate, passes through. 

A limitation to the more widespread use of membrane separation processes is membrane fouling, as would be expected in the industrial application of such finely porous materials. Fouling results in a continuous decline in membrane penneation rate, an increased rejection of low molecular weight solutes and eventually blocking of flow channels. On start-up of a process, a reduction in membrane permeation rate to 30-10% of the pure water permeation rate after a few minutes of operation is common for ultrafiltration. Such a rapid decrease may be even more extreme for microfiltration. This is often followed by a more gradual... 

The ceramic membrane has a great potential and market. It represents a distinct class of inorganic membrane. In particular, metallic coated membranes have many industrial applications. The potential of ceramic membranes in separation, filtration and catalytic reactions has favoured research on synthesis, characterisation and property improvement of inorganic membranes because of their unique features compared with other types of membrane. Much attention has focused on inorganic membranes, which are superior to organic ones in thermal, chemical and mechanical stability and resistance to microbial degradation. 

Water Tube Steam Generators Steam generators for industrial applications may have internal boiler components such as drums, boiler bank, and membrane wall designed in one of several different arrangements. These arrangements are based on the position of the boiler drum and include the following ... 

New results of multiple membrane separation are presented, which showed a possible feasibility for industrial application in the near future The NF permeate obtained (membrane NF90) could meet specifications for water reuse in the textile industry... 

In this chapter, the focus is on how zeohte membranes can be appHed in the field of catalysis and to what extent this is successful. The latter is illustrated by reviewing some commonly studied zeohte membrane applications. Finally, the current hurdles that impede industrial application are discussed and some remarks... 

It is evident that zeoHte membranes can have added value in catalysis, but industrial applications are stiU lacking. Thus, the question remains what the major factors are that stand in the way of application. The following factors are considered troublesome and are discussed in more detail ... 

Ultrasound can thus be used to enhance kinetics, flow, and mass and heat transfer. The overall results are that organic synthetic reactions show increased rate (sometimes even from hours to minutes, up to 25 times faster), and/or increased yield (tens of percentages, sometimes even starting from 0% yield in nonsonicated conditions). In multiphase systems, gas-liquid and solid-liquid mass transfer has been observed to increase by 5- and 20-fold, respectively [35]. Membrane fluxes have been enhanced by up to a factor of 8 [56]. Despite these results, use of acoustics, and ultrasound in particular, in chemical industry is mainly limited to the fields of cleaning and decontamination [55]. One of the main barriers to industrial application of sonochemical processes is control and scale-up of ultrasound concepts into operable processes. Therefore, a better understanding is required of the relation between a cavitation coUapse and chemical reactivity, as weU as a better understanding and reproducibility of the influence of various design and operational parameters on the cavitation process. Also, rehable mathematical models and scale-up procedures need to be developed [35, 54, 55]. 

More recently, many workers have concentrated on controlling the size and shape of particles, with an eye on industrial applications, where such features must be well defined and controllable. Many shapes have been made, including fibres, spheres, plates, as well as membranes cast on... 

They may also be required in industrial applications where they become part of venting systems on fermenters, centrifuges, autoclaves and freeze-dryers. Certain types of filter (membrane filters) also have an important role in sterility testing, where they can be employed to trap and concentrate contaminating organisms from solutions under... 

Organic polymers are sometimes referred to as plastics (although, this should be confined to thermoplastic polymers), macromolecules or resins, though the latter is often used to describe raw polymeric material awaiting fabrication. Many polymers are used in various forms that are not associated with normal plastic materials. These include paints and coatings, elastomers (rubbers), adhesives, sealants (caulks), surfactants and also their use in various industrial applications, e.g., ion-exchange resins, membranes. 

As was noted above, functional fluoropolymers produced by copolymerization of fluoroolefins with functional PFAVE have several unique properties, with the main disadvantage of these materials being the extremely high cost of functional monomers and the resulting high cost of the functional polymers produced from them. The fact that they are so expensive limits their wider industrial application in other fields such as catalysis and membrane separation, except for chlorine-alkali electrolysis and fuel cells, where the only suitable materials are fully fluorinated polymers because of the extreme conditions associated with those processes. 

Block copolymers possess unique and novel properties for industrial applications. During the past 20 years, they have sparked much interest, and several of them have been commercialized and are available on the market. The most common uses of block copolymers are as thermoplastic elastomers, toughened thermoplastic resins, membranes, polymer blends, and surfactants. From a chemist s point of view, the most important advantage of block copolymers is the wide variability of their chemical structure. By choice of the repeating unit and the length and structure of both polymer blocks, a whole range of properties can be adjusted. 

Early examples of the industrial application of this process (e.g. in the 1970s, General Electric [2] used first-generation ion-exchange membranes and SPE technologies) were not successful, mainly because of stability and activity/performance problems with the GDE. 

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