Ultrafiltration economics

Kirkman, A. G. Gratzl, J. S. Edwards, L. L. Kraft lignin recovery by ultrafiltration economic feasibility and impact on the kraft recovery system. Tappi J. 1986, 69(5), 110-114. 

Whey has been used ia some substitute dairy products but aot as a source of proteia. Whey proteias have beea used ia dairy substitutes only siace the commercialisation of ultrafiltration (qv) technology. Membranes are used that retain proteia and permit water, lactose, and some minerals to pass through as permeate. Proteia coaceatrates are available from both acid and sweet whey and ia coaceatratioas of 35—80 wt % proteia. Whey proteia isolates are commercially available having proteia >90 wt%. The cost of these isolates is too high, however, to make them economical for substitute dairy foods. 

Large Plants The economics of microfiltration units costing about ilO " is treated under ultrafiltration. When ceramic membranes are used, the cost optimum may shift energy consumption upward to as much as 10 kWh/m. ... 

Nonselective membranes can assist enantioselective processes, providing essential nonchiral separation characteristics and thus making a chiral separation based on enantioselectivity outside the membrane technically and economically feasible. For this purpose several configurations can be applied (i) liquid-liquid extraction based on hollow-fiber membrane fractionation (ii) liquid- membrane fractionation and (iii) micellar-enhanced ultrafiltration (MEUF). 

Cross-flow is the usual case where cake compressibility is a problem. Cross-flow microfiltration is much the same as cross-flow ultrafiltration in principle. In practice, the devices are often different. As with UF, spiral-wound membranes provide the most economical configuration for many large-scale installations. However, capillary devices and cassettes are widely employed, especially at smaller scale. A detailed description of cross-flow microfiltration had been given by Murkes and Carlsson [Crossflow Filtration, Wiley, New York (1988)]. 

The basis of ultrafiltration is that a liquor is passed through a membrane many times until the required concentration of the permeate is attained. Fouling of the membrane can be a problem and regular cleaning and disinfection of the membrane is recommended. Ultrafiltration of poly(vinyl alcohol) and starch sizes offers economic advantages over... 

The ultrafiltration of the microemulsion is a very useful operation for separating water and oil in these mixtures [117-120]. Because of the limited availability of solvent stable membranes, most of the work pubHshed so far was performed using ceramic membranes, which show a high adsorption of surfactant at the membrane surface and comparably low rejection rates of reverse micelles. Using electro ultrafiltration, where the concentration polarisation phenomenon of the reverse micelles (using the ionic surfactant AOT) at the membrane surface is depressed by asymmetric high voltage electrical fields, the rejection rates can be increased,but not to economical values [121,122]. 

Because of the broad differences between ultrafiltration equipment, the performance of one device cannot be used to predict the performance of another. Comparisons can only be made on an economic basis and only when the performance of each is known,... 

In the dairy industry the high content of minerals in cow milk (Table IX) restricts the commercial utilization of its main by-products, that is, whey and ultrafiltration permeates. The discovery that desalted whey could be used in baby food production as an economic alternative to the more expensive skim... 

Figure 6.20 Purchase price in 2003 US dollars for ultrafiltration plants as a function of plant capacity. Data of Rogers corrected for inflation [20]. Reprinted from Synthetic Membrane Processes, A.N. Rogers, Economics of the Application of Membrane Processes, p. 454, G. Belfort (ed.), Copyright 1984, with permission from Elsevier...

Oil-water emulsions are widely used in metal machining operations to provide lubrication and cooling. Although recycling of the fluids is widely practiced, spent waste streams are produced. Using ultrafiltration to recover the oil component and allow safe discharge of the water makes good economic sense, and... 

Many reseachers have previously studied the use of ultrafiltration to recycle cellulase during saccharification (5-22). However, much of this previous work involved either purified cellulosic substrates, such as Solka-Floc, which are not representative of feedstocks in large-scale operations, or lignocellulosic substrates at concentrations that would be much too low to be economical in a full-scale process. 

Ultrafiltration, which uses selective membranes to separate materials on the basis of different molecular sizes, has become a valuable separation tool for a wide variety of industrial processes, particularly in the separation of dispersed colloids or suspended solids. In many cases where a high degree of separation is desired, a batch ultrafiltration process is used because it is the most economical in terms of membrane area. 

The selection of the most suitable enzyme for a certain purpose mainly depends on its biocatalytic characteristics. Once a correct choice has been made, it is important to minimize the expenses associated with the enzyme use, as the economic feasibility of enzymatic processes is likely to depend on the cost of the enzyme production. In this context, several authors showed that the performance of various peroxidase processes was independent of enzyme purity [1,2], even suggesting that the crude enzyme was protected from inactivation [3, 4]. Microfiltration and subsequent ultrafiltration stages are sufficient to separate biomass and concentrate the enzyme for an economically viable operation [2, 5]. 

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