Microfiltration Equipment

All stirred experiments were stirred at 270 rpm (measured with a Philips PR 9115/00 stroboscope). A balance and stop watch were used to measure permeate volume. Experiments were conducted at a temperature of 25 1 C. 

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

Sales of microfiltration equipment and membranes are expected to rise from 1.9 billion worldwide in 2005 to 2.5 billion in 2008. The main applications are the production of sterilized water for the pharmaceutical and biotechnology industry. 

Fig. 28. Schematic representation of dead-end and cross-flow filtration with microfiltration membranes. The equipment used in dead-end filtration is simple, but retained particles plug the membranes rapidly. The equipment required for cross-flow filtration is more complex, but the membrane lifetime is...

Pretreatment For most membrane applications, particularly for RO and NF, pretreatment of the feed is essential. If pretreatment is inadequate, success will be transient. For most applications, pretreatment is location specific. Well water is easier to treat than surface water and that is particularly true for sea wells. A reducing (anaerobic) environment is preferred. If heavy metals are present in the feed even in small amounts, they may catalyze membrane degradation. If surface sources are treated, chlorination followed by thorough dechlorination is required for high-performance membranes [Riley in Baker et al., op. cit., p. 5-29]. It is normal to adjust pH and add antisealants to prevent deposition of carbonates and siillates on the membrane. Iron can be a major problem, and equipment selection to avoid iron contamination is required. Freshly precipitated iron oxide fouls membranes and reqiiires an expensive cleaning procedure to remove. Humic acid is another foulant, and if it is present, conventional flocculation and filtration are normally used to remove it. The same treatment is appropriate for other colloidal materials. Ultrafiltration or microfiltration are excellent pretreatments, but in general they are... 

In all of the above equations, is assumed to be constant and uniform throughout the flow field. In most items of bioprocess equipment, however, there is a spatial distribution of energy dissipation. The definition of an average or a maximum energy dissipation rate is notoriously difficult in the case of bioprocess equipment such as high pressure homogenisers, centrifuges, pumps and microfiltration units which all have complex flow fields. 

Membrane equipment for industrial scale operation of microfiltration, ultrafiltration and reverse osmosis is supplied in the form of modules. The area of membrane contained in these basic modules is in the range 1-20 m2. The modules may be connected together in series or in parallel to form a plant of the required performance. The four most common types of membrane modules are tubular, flat sheet, spiral wound and hollow fibre, as shown in Figures 8.9-8.12. 

Heavy wall tubing plain, coloured, striped tubing fabrications for instrumentation automotive push-pull cables industrial and process hydraulics and other fluids. .. Piping liners for glass-lined reactors, stainless steel reactors, glass equipment and mixers... Membranes, filter media, filter bags, cartridges, microfiltration membranes, vents and adsorbent products. .. 

The costs of the EPOC Water, Inc. (EPOC) microfiltration technology are affected by system flow rates, amount of recycle, contaminant type and concentration, reagent type and amount, and the type and size of dewatering equipment used (D11314U, p. 15). 

Sterilization can be accomplished by several means, including heat, chemicals, radiation (ultraviolet (UV) or y-ray), and microfiltration. Heat is widely used for the sterilization of media and fermentation equipment, while microfiltration, using polymeric microporous membranes, can be performed to sterilize the air and media that might contain heat-sensitive components. Among the various heating methods, moist heat (i.e., steam) is highly effective and very economical for performing the sterilization of fermentation set-ups. 

Microfiltration can be used to replace a clarifier in the chemical clarification of plating discharges. Compared to conventional equipment, it offers the advantages of continuous processing and significantly smaller space requirements. Figure Nine (9) illustrates a microfiltration installation. 

Microfiltration units can be configured as plate and frame flat sheet equipment, hollow fiber bundles, or spiral wound modules. The membranes are typically made of synthetic polymers such as Polyethersulfone (PES), Polyamide, Polypropylene, or cellulosic mats. Alternate materials include ceramics, stainless steel, and carbon. Each of these come with its own set of advantages and disadvantages. For instance, ceramic membranes are often recommended for the filtration of larger particles such as cells because of the wider lumen of the channels. However, it has been shown that spiral wound units can also be used for this purpose, provided appropriate spacers are used. 

Brou A, Ding L, Boulnois P, and Jaffrin M, Dynamic microfiltration of yeast suspensions using rotating disks equipped with vanes, J. Membr. Sci. 2002 197 269-282. 

MicrofQtration with 0.2 im ceramic membranes (HIC) yields average fluxes of 125-150 1/m h at temperatures from 40 to 70°C. Suspended solids and concentration of hydrocarbons are both reduced to less than 10 ppm in the permeate. By RO the COD is reduced to below 100 mg/1. Cleaning interval for the microfiltration installation is once a week. The feed to the microfiltration system has to be filtered over 100 pm screens to prevent clogging of the equipment. 

Fig. 6 Examples of downstream process equipment (A) filter press (B) rotary vaccum drum (C) microfiltration unit. (View this art in color at www.dekker.com.)...

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