Woven structures collection

The filter structure consists of a stack of plates attached to a hollow shaft which are mounted inside a pressure vessel with each plate covered with a suitable filter medium. The slurry is fed under pressure into the vessel and the cake, which is retained by the filter medium, forms on the top of each plate whilst the filtrate passes through the hollow shaft further to the process. Filter sizes may vary but generally the maximum is 60 m area and designed for a 6 bar operating pressure. Each circular plate in the stack is constructed with radial ribs that are welded to the bottom and support a horizontal coarse mesh screen which is covered with a finer woven metal screen or filter cloth to retain the cake. The bottom of the plate slopes towards the hollow central shaft which lets the filtrate flow freely through circumferential holes and further down the shaft to the filtrate outlet. The clearance between the plates is maintained by special spacers with "o" rings to positively seal between the slurry that surrounds the plates and the shaft that collects the filtrate. The height of the spacers determine the clearance for cake build-up and may be replaced to meet various process conditions. 

Figure 23 Mammalian bone at different levels of resolution (a) Collagen fibril with associated mineral, (b) Woven bone (random collagen distribution), (c) Lamellar bone showing separate lamellae with collagen organized in domains with preferred orientation alternating in adjacent lamellae, (d) Woven bone with blood channels shown as dark spots, woven bone stippled, (e) Primary lamellar bone orientation indicated by dashes, (f) Haversian bone, a collection of haversian systems are shown as a longitudinal structure. Each system has concentric lamellae around a central blood channel. Darkened area represents an empty (eroded) portion of the section which will be reconstituted with new bone, (g) Alternation of woven and lamellar bone, (h) Various orientations of heavily mineralized (cortical, or compact) bone, (i) Trabecular, or cancellous, bone (Wainwright et aL, 1976) (reproduced by permission of Hodder Arnold from Mechanical Design in Organisms, 1976).

A variety of fabrics styles are employed in dust collection, these being chosen according to the physical forces that will be imposed by the filter and the quantity and abrasive nature of the dust being collected. As a consequence, for reverse air and pulsejet filters needlefelts are preferred whereas for shake filters both woven and needlefelt structures are used. By comparison for cartridge filters spunbonded, meltblown and electrospun fabrics are more likely to be found. 

Felt-fabric filter media (more particularly needle felts) have gained in importance in recent years. In the "needling" process the fibres are intimately matted together by the action of numerous needles with barbed hooks. These felts are often provided with a woven fabric reinforcement to give additional strength and dimensional stability to the felt. Thanks to their closely matted fibre texture with approximately uniform pore structure, felts attain higher collection efficiency in conjunction with lower pressure drop than woven filter fabrics. 

First, the collected used textiles are sorted according to their quality, the necessary criteria for which are condition, type of fibrous material, color, structure (woven fabric, knitwear, nonwoven), type of textile, and so forth. Normally, there is a division of more than 200 different fractions. Modern sorting plants convert several thousands of tons per year. 

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