Feeding, membrane technology

In order to maintain a definite contact area, soHd supports for the solvent membrane can be introduced (85). Those typically consist of hydrophobic polymeric films having pore sizes between 0.02 and 1 p.m. Figure 9c illustrates a hoUow fiber membrane where the feed solution flows around the fiber, the solvent—extractant phase is supported on the fiber wall, and the strip solution flows within the fiber. Supported membranes can also be used in conventional extraction where the supported phase is continuously fed and removed. This technique is known as dispersion-free solvent extraction (86,87). The level of research interest in membrane extraction is reflected by the fact that the 1990 International Solvent Extraction Conference (20) featured over 50 papers on this area, mainly as appHed to metals extraction. Pilot-scale studies of treatment of metal waste streams by Hquid membrane extraction have been reported (88). The developments in membrane technology have been reviewed (89). Despite the research interest and potential, membranes have yet to be appHed at an industrial production scale (90). 

The aqueous stream is at higher pressure than the strip gas (or vacuum) and fast diffusive transport of dissolved gases takes place. Gas transfer membrane technology is suitable for deaeration of boiler feed, building water, and other applications, and produces water with DO levels down to 1 ppb 02. 

Membrane technology for natural-gas separations is gaining broad acceptance and a number of major membrane-separation plants have come into operation in recent years. These include the Cakerawala production platform (CKP) that processes 700 MMScfd with a 37% C02 feed and a plant in Qadirpur, Pakistan that processes 500 MMscfd of 6.5 mole% C02 feed to 2% C02 pipeline specification [26]. Current plans are being made to double production at the CKP facility [27]. 

FIGURE 22 Two-step, two-stage membrane system to produce pure nitrogen and a concentrated propylene stream from a dilute feed gas. (Membrane Technology and Research, Inc.) [Baker, R. W., et al. (1998). J. Membrane Sci. 159, 55-62.]... 

Membrane technology is a mature industry and has been successfully applied in various food industries for separation of undesirable fractions from the valuable components of the feed streams. The industrial membranes are classified into various categories such as microfiltration, ultrafiltration, nanofiltration, reverse osmosis, and pervaporation. 

Recent research efforts brought about new and exciting developments in membrane technology, some with direct implications for the membrane filtration of beer. For example, Stopka et al. [21] reported flux enhancement in the microfiltration of a beer yeast suspension when using a ceramic membrane with a helically stamped surface. A relatively simple modification of the ceramic membrane surface resulted in modified hydrodynamic conditions and disturbance of the fouling layer. As compared with a regular, smooth ceramic membrane of the same nominal pore size, the stamped membrane leads to higher flux and lower power consumption per unit volume of permeate at the same velocity of the feed. 

FIGURE 21.10 EDBM setup for feed and bleed mode run. (Reprinted with permission from Kemperman, A.J.B., Ed. Handbook of Bipolar Membrane Technology, Twente University Press, Enschede, The Netherlands, 2000. Copyright 2000 Twente University Press, p. 183.)... 

One special property of the process waters discussed is the broad heterogeneity in concentration of the dissolved and dispersed molecules. This is due to different products manufactured using the same machine and also due to shut down and start-up periods. Several authors have shown that the concentrations of organic and inorganic compounds vary even tenfold in process waters [18,27,28]. This means that when using membrane technology the membranes should be resistant to big fluctuations in the feed stream. 

For an ideal system, all contaminants to be removed are separated by the membrane and exit in the concentrate stream. In reality, no membrane is perfect. The actual quantity of solute that passes through the membrane depends on the chemistry of solute on the feed, the nature of membrane material, and the operational conditions. Cell test, applications test, and pilot test can be used to evaluate membrane technology with a particular stream. 

Membrane technology is used to remove oil particles from industrial wastewater. The initial feed tank volnme is 8640 m /d and after treatment the retained volume is required to be 50% of the initial volume entering to the basin. If the observe rejected coefficient is... 

The separation of helium from natural gas is a potential application of membrane technology. Using a membrane with a He/CH. selectivity of 190 and a feed with only 0.82 percent He, half of the helium can be recovered in a single stage, giving a permeate 30 times richer than the feed, ... 

In membrane technology, processes consisting of more than one stage are known in gas permeation and for the production of boiler feed water from seawater. Furthermore, cascades will be necessary if organic mixtures are to be separated by membrane processes only. 

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