Wires knitting

Mesh beds of knitted wire mesh, plastic, or glass fibers are used for the removal of Hquid particulates and mist. They will also remove soHd particles, but win plug rapidly unless irrigated or flushed with a particle-dissolving solvent. 

Fiber Bed Alist Filtration. In-depth fiber bed filters are used for the collection of Hquid droplets, fogs, and mists. Horizontal pads of knitted metal wire (or plastic fibers), 100—150 mm thick, and gas updow are used for Hquid entrainment removal. Pressure drop is 250—500 Pa (1.9—3.8 mm Hg). 

Knitted wire mesh serves as an effective entrainment separator when it cannot easily be foiiled by sohds in the liquor. The mesh is available in woven metal wire of most alloys and is installed as a blanket across the top of the evaporator (Fig. ll-122d) or in a monitor of reduced diameter atop the vapor head. These separators have low-pressure drops, usually on the order of 13 mm [ M in) of water, and collection efficiency is above 99.8 percent in the range of vapor velocities from 2.5 to 6 iti/s (8 to 20 ft/s) [Carpenter and Othmer, Am. nsi. Chem. 

Filters for mists and droplets have more open area than those used for dry parhcles. If a filter is made of many fine, closely spaced fibers, it will become wet due to the collected liquid. Such wethng will lead to mathng of the fibers, retenhon of more liquid, and eventual blocking of the fiter. Therefore, instead of fine, closely spaced fibers, the usual wet filtrahon system is composed of either knitted wire or wire mesh packed into a pad. A looser filtrahon medium results in a filter with a lower pressure drop than that of the filters used for dry parhculates. The reported pressure drop across wire mesh mist eliminators is 1-2 cm of water at face velocihes of 5 m sec T The essenhal collechon mechanisms employed for filtrahon of droplets and mists are inertial impachon and, to a lesser extent, direct intercephon. 

A stationary separator element of knitted small diameter wire or plastic material is formed of wire 0.003 in. to 0.016 in. (or larger) diameter into a pad of 4 inches, 6 inches or 12 inches thick and serves as the impingement surface for liquid particle separation. Solid particles can be separated, but they must be flushed from the mesh to prevent plugging. Although several trade name units are available they basically perform on the same principle, and have very close physical characteristics. Carpenter [4] presented basic perform.ance data for mesh units. Figure 4-15 shows a qpical eliminator pad. 

There are several types of mesh available, and these are identified by mesh thickness, density, wire diameter and weave pattern. Table 4-9 identifies most of the commercial material now available. The knitted pads are available in any material that can be formed into the necessary weaves, this includes stainless steels, monel, nickel, copper, aluminum, carbon steel, tantalum, Hastelloy, Saran, polyethylene, fluoropolymer, and glass multi-filament. 

Multistrand wire, close-knit in two layers, holds stable liquid film by surface tension. Falling films of liquid form expansive contact surface with rising vapor layers. 

Preliminary Sizing for ACS Industries Series Woven X/S Knitted Wire Mesh Structured Packing... 

Figure 9-48. ACS maximum vapor velocity correction for L/G for woven/knitted wire mesh structured packing. Used by permission of ACS Industries, Inc., Separation Technology Division, Bull. B-129 (1992).

Impingement separators, 246, 257 Chevron style, 248, 255 Efficiencies, 246 Knitted wire mesh, 246 York-vane efficiencies, 248 Inertial centrifugal separators, 266, 268 Kinetic energy, pump system, 187 Lamella plate classifiers, 239 Line sizing work sheet, 107... 

A large variety of hose constructions are produced by the rubber industry for a wide range of applications. To contain transported liquids, usually under pressure, it is necessary to reinforce the hose construction with fabric, yam or short fibres to constrain expansion of the rubber. Although hand-built construction using fabric still represents a proportion of the production, it is also very common to use yams either braided or knitted directly onto the hose liner. For heavy duty purposes it is also necessary to use wire, in a braided form, to either reinforce or protect the hose from external damage. Use of short fibres as reinforcement represents a small proportion of hose production and requires specialised dies for extrusion to orientate the fibres circumferentially. 

The company also manufactures a complete line of filters, feed-thru capacitors, variable ceramic capacitors, RFI shields, and knitted wire gaskets... 

A second type of impingement separation device is a knitted wire mesh pad. The primary mechanism of separation in the knitted wire mesh is impingement. It also utilizes centrifugal and gravitational force in the collection of small liquid particles. 

During 1954 and 1955, the research department of Black, Sivalls Bryson, Inc., made a very comprehensive study of various types and arrangements of knitted wire mesh and vane type mist extractors. Many tests were conducted under closely controlled conditions Samples of droplets passing through mist extractors were carefully collected and their diameter measured with the use of microscopic photographing equipment. 

The tests showed the knitted wire mesh has high gas and liquid handling capacities. It was also found to increase in removal efficiency with increased gas velocities when small droplets were involved, until the pad approached a flooding condition. As the flooding velocity-is approached, considerable liquid is held up within the pad between the wire. Since the area left for gas flow is decreased by the presence of the liquid, the gas velocity increases until large droplets are torn away from the back side of the pad and carried from the separator with the gas velocity. 

Aimes all droplets greater than 10 microns in diameter were removed by the knitted wire mesh pads within the capacity limitations. However, a few droplets as large as 20 microns in diameter were allowed to pass through the unit. This is not a serious limitation since it would lake 90,000 of these droplets in each standard cubic foot of gas passing... 

Impingement type mist extractor exemplified by knitted wire mesh pads are widely used in oilfield liquid and gas separation equipment. Their liquid and gas handling capacities are good with high liquid droplet removal efficiencies with small gas pressure drop. 

In the middle of the pack, the gauzes consist of warp knitted gauzes with lower voidage and possibly smaller diameter wire. 

The catalyst typically consists of several woven or knitted wire gauze sheets with a composition of about 90% platinum, 5% to 10% rhodium and up to 5% palladium. The primary functions of rhodium are to add mechanical strength to the gauze and to improve yield. The palladium is present to replace a portion of the more expensive rhodium91,104. Figure 9.1 shows that conversion efficiency does not improve if more than 5% rhodium is present in the catalyst144. 

The steam may be purified by Droplet Separation techniques such as knitted wire mesh demister pads, wave plate separators and fiber pad separators using PTFE fibers. It can also be purified by scrubbing devices such as packed columns, venturi scrubbers, and irrigated sieve plates. Sometimes a combination of Droplet Separators and Scrubbers are used because AN emissions from neutralizers are very difficult to remove due to the very fine particles103. 

The atoms of metals exhibit metallic bonding, in that the valence electrons of the metal atoms form a pool of electrons. This pool of electrons is shared by all the atoms and therefore serves to knit them together. Because these electrons are free to move, metals are excellent conductors of electricity. Other qualities of metals, including malleability, the ability to be hammered into forms, and ductility, the ability to be drawn into wires are facilitated by the flexibility of this sea of electrons. 

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