Solid/liquid separation cartridge filters

Figure 4.15. Solid-liquid separation in industrial scale using centrifugation in continuous mode (A) or passage of the suspension through manifolds such as those shown in (B) mounted with filter cartridges (C) designed for tangential or cross-flow of liquid suspension. Panel A NIH Fredrick facility, with permission Panels B and C Milipore, MA, with permission.

Howard, G.W. and Nickolaus, N., 1986, Cartridge Filters, in Solid/Liquid separation equ ment scale-up, D.B.Purchas and RJ.Wakeman, (Eds.) Uplands Press, Croydon. 

The most common of the distinct phase separation processes given in Table 1.1 are the solid/fluid ones solid/gas separations being exemplified by the treatment of process and boiler exhausts in baghouses, and by the panels used in building air conditioning solid/liquid separations cover the enormous range of filter types from the simple cartridge filter to the complex machines such as the rotary pressure... 

Filter. A filter is used in some cases when coagulation and sedimentation do not completely separate the solids from the liquid waste in areas where sand and sandstone formations are susceptible to plugging. Filters with a series of metal screens coated with diatomaceous earth or cartridge filters are typically used.27 Where limestone formations with high solution porosity are used for injection, filtration is usually not required. 

In the filtration process, a liquid containing suspended solids is passed through a porous medium. The solids are trapped against the medium, and the separation of solids from liquids results. For large solid particles, a thick barrier such as sand may be used for smaller particles, a fine filter such as a filter cloth is preferable. Fluid passage may be induced by gravity, positive pressure, or a r acuum. A few of the more popular filter fypes are the plate and frame filter press, and shell and leaf and cartridge filters. 

The driving force for filtration in pressure filters is usually the liquid pressure developed by pumping or by the force of gas pressure in the suspension feed vessel. Alternatively, or in addition, the liquid may be squeezed through and out of the cake by the mechanical action of an inflatable membrane, a piston or a porous medium pressed on top of the cake. Pressure filtration is, therefore, defined here as any means of surface filtration where the liquid is driven through the medium by either hydraulic or mechanical pressure, greater than atmospheric. The solids are deposited on top of the filter medium (as in all surface filters), with the possible exception of some cartridge filters which also use a certain amount of depth filtration. In this chapter, the suspension is assumed to approach the medium at 90° and this excludes the so-called dynamic fUter/thickeners or cross-flow filters (also driven by pressure) which are dealt with in a separate chapter (11). 

The usual objective of clarifying filtration is to separate solids at a very low concentration fi om a liquid stream. The liquid may be drinking (potable) water, wine, beer, oil, etc. and it is usually the liquid which is the valuable product. The techniques used in clarification processes include deep-bed, precoat, candle and cartridge filtration all of which involve capture of particles inside the porous mass of the filter. Such techniques produce clearer filtrates than those obtained in clarification by sedimentation. The filtration techniques listed are ofiioa complementary they are eirqrloyed for similar duties, but usually operate over different conditions of feed flow rate, feed concentration and process economics. These operating conditions are summarised in Table 6.1. 

Filter chamber. The filter cartridges in the filter chamber have two functions— first, to coalesce fine liquid droplets into larger ones that are subsequently separated in the mist extractor chamber, and second, to filter out all remaining solid particles that have not been removed in the inlet chamber. 

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