Membranes sintered metal

Symmetric (where the pore size is uniform through the membrane example, polyolefins, fluoropolymers, nylons with porosity as high as 85% throughout membrane sintered metals with porosity 25-30%). 

A wide diversity of filter types exist— membranes, sintered metallic frits, 3D filters—and many types of materials are used. Likewise, particulates can be of widely different types soft microgels, hard microcrystals, biological cells, and aggregates... 

Inorganic membranes (29,36) are generaUy more stable than their polymeric counterparts. Mechanical property data have not been definitive for good comparisons. IndustriaUy, tube bundle and honeycomb constmctions predominate with surface areas 20 to 200 m. Cross-flow is generaUy the preferred mode of operation. Packing densities are greater than 1000 /m. Porous ceramics, sintered metal, and metal oxides on porous carbon support... 

Controlled removal of the template is especially important when zeolite based membranes are involved consisting of a continuous MFI layer on a ceramic or sintered metal support (ref. 14). In these novel composite ceramic membranes the formation of cracks during template removal would be detrimental. The unique properties (ref. 14) of metal-supported MFl-layer membranes prove that indeed crack formation can be essentially prevented. 

Experiments were conducted at the University of Magdeburg to examine the partial oxidation of ethane to ethylene by dosing oxygen into the fluidized bed of porous catalysts using immersed sintered metal and ceramic membranes. These studies were related to a DFG (German Research Association) research group (DFG-Nr. FOR 447/1-1) Membrane supported reaction engineering in the subproject Fluidized-bed membrane reactor . 

Asymmetrical flow-FFFA (A-Fl-FFF) was introduced by Wahlund and Giddings in 1987 [47]. The same system was independently suggested slightly earlier by Granger et al. [237,248], but their application of the technique suffered from a lack of a primary relaxation step preceding separation [47]. A-Fl-FFF is notable for a channel which has only one permeable wall so that the solvent can leave the channel only via the accumulation wall and thus generates a cross-flow. The permeable wall is usually a sintered metal plate or ceramic frit covered by an ultrafiltration membrane (see Fig. 20). 

In contrast to dense inorganic membranes, the rate of advances toward industrial-scale applications of porous inorganic membranes has been rapid in recent years. In the early periods of this century, microporous porcelain and sintered metals have been tested for microfiltration applications and, in the 1940s, microporous Vycor-type glass membranes became available. Then in the mid-1960s porous silver membranes were commercialized. These membranes, however, have not seen large scale applications in... 

The dynamic membranes originally developed by Union Carbide are protected by three core patents U.S, 3977967, 4078112, and 4412921 (Trulson and Litz, 1976 Bibeau, 1978 and Leung and Cacciola, 1983) and their foreign equivalents. Those patents cover a broad range of metal oxides such as zirconia, gamma alumina, magnesia>alumina spinel, tantalum oxide and silica as the membrane materials and carbon, alumina, aluminosilicates, sintered metals, fiberglass or paper as the potential porous support materials. However, their marketed product, trade named Ucarscp membranes, focused on dynamic membranes of hydrous zirconium oxide on porous carbon support. 

The MF membranes are usually made from natural or synthetic polymers such as cellulose acetate (CA), polyvinylidene difiuoride, polyamides, polysulfone, polycarbonate, polypropylene, and polytetrafiuoroethylene (FIFE) (13). Some of the newer MF membranes are ceramic membranes based on alumina, membranes formed during the anodizing of aluminium, and carbon membrane. Glass is being used as a membrane material. Zirconium oxide can also be deposited onto a porous carbon tube. Sintered metal membranes are fabricated from stainless steel, silver, gold, platinum, and nickel, in disks and tubes. The properties of membrane materials are directly reflected in their end applications. Some criteria for their selection are mechanical strength, temperature resistance, chemical compatibility, hydrophobility, hydrophilicity, permeability, permselectivity and the cost of membrane material as well as manufacturing process. 

As a general conclusion to this part dedicated to nanofiltration with ceramic membranes one can assume that the general behaviour of these membranes can be assimilated to the behaviour of electrically charged organic nanofiltration membranes. However some specificities exist with ceramic nanofilters due to a sintered metal oxide grains derived porous structure and an amphoteric character... 

Membrane symmetric or asymmetric microporous. Ceramic, sintered metals, or polymers with pores 0.2 to 1 pm. Symmetric polymers have a porosity of 60 to 85% asymmetric ceramic membranes, porosity 30 to 40%, are used for high pressure and higher temperature <200°C. 

Hydraulic permeability, A 70 to 10,000 g/s-m. MPa. Pressure 0.3 to 0.5 MPa for ceramic. Capacity/unit 0.001 to 1 L/s. Liquid permeate flux 0.001 to 0.2 L/s-m with the permeate flux through ceramic membranes 2 to 3 times higher than through symmetric polymeric or sintered metal membranes and 5 to 10 times higher than through asymmetric polymeric membranes because ceramic operates at higher pressure. 

In membrane-separation processes, a feed consisting of a mixture of two or more components is partially separated by means of a semipermeable membrane through which one species moves faster than the others. That part of the feed that passes through the membrane is called the permeate, while the portion that does not pass is called the retentate. The membranes may be thin layers of a rigid material such as porous glass or sintered metal, but more often they are flexible films of synthetic polymers prepared to have high permeability for certain types of molecules. 

Fig 3 A sandwich-type reagent degasser. A, B, plastic blocks D. sintered metal disk M, microporous membrane and G, engraved groove [12]. 

It is often found that the sintered metal and porous ceramic supports that have been used for many academic membrane studies are very expensive, sometimes even exceeding the cost of the palladium alloy membrane by several fold. This situation cannot be accepted for commercial membrane modules, especially when a large membrane area of up to several hundred to several thousand square meters is required. Some of the least expensive membrane supports include tension springs for tubular membranes and woven wire mesh for planar membranes, but even these supports can be costly, and further development of exceptionally low cost membrane supports is needed. 

The most common methods for manufacturing thin metal membranes include rolled foil, drawn tubes, and films deposited onto porous substrates (ceramic or sintered metal). Usually, electroless plating or electrolytic plating are the methods used to deposit the permselective metal onto the porous substrates although vapor deposition methods have been the subject of much research effort However, to date, vapor deposition methods have not proven to be a superior membrane fabrication method. There are pros and cons to each of these methods, but commercial membrane modules have only succeeded using rolled foil and drawn tubular membranes. 

This is difficult to achieve in practice, but it is always a good practice to comparatively evaluate candidate supports for thickness, porosity, and tortuosity. Support materials that have been used include porous ceramics, porous metal such as sintered metal, metal screens, metal mesh, and slotted metal plates. Metal mesh has been demonstrated to offer favorable performance and attractive cost The thin Pd-40Cu membranes shown in Fig. 5.4 have been supported on a 70 x 70 mesh the impressions on the membrane surface are caused by the underlying support When evaluating the acceptable pore diameter for the membrane support, a general rule is that the pores or openings in the support should not be greater than about four times the membrane thickness. If the membrane is very... 

The effect of increased membrane permeability is depicted in Fig. 5.14. The material properties considered now correspond to that of a sintered metallic macrofiltration membrane (Bq = 8.6 x 10" m, mean ipor = 100 pm). In this calculation, the same total flow rate and the same Fts/Fss ratio was applied as in Fig. 5.13. As can be seen, both profiles of the axial and radial velocity differ significantly at different axial positions (Fig. 5.14). 

Huang Y, Dittmeyer R (2006) Preparation and characterization of composite palladium membranes on sinter-metal supports with a ceramic barrier against intermetallic diffusion. J Membr Sci 282 296-310... 

Mineral membranes are obtained by sintering metal powders or stainless steel filaments with diameters between 1.5 and 80 pm [17—19]. They can be more expensive than ceramic membranes, and are hmited in selection by their pore size range. Organo-mineral membranes are hybrid membranes, e.g., UF organo-mineral membranes are composed of a polymeric matrix (mosdy PS) in which zirconia grains are dispersed finely as a filler material. The organo-mineral membranes have a considerably higher flux than traditional polymeric membranes. 

In vented cells the sintered metal is cut to the final plate size and, after conduction tabs are welded, the cell is put together in a similar way to the pocket plate cells except that the separator is a thin sheet of low-resistance, small-pore plastic often with a second layer to prevent oxygen transport. These membranes may be cellophane and a non-woven polyamide respectively. 

If directional characteristics are considered, the membrane may be either isotropic or anisotropic. Examples of anisotropic membranes are cellular membranes including axonal membranes composed of different layers [21]. It has been pointed out that sandstones [22] and other rocks, sintered metals, sintered glass and unglazed ceramic bodies may be anisotropic with respect to permeability. In the following, we shall consider the case of uncharged membrane or capillary. 

Cartridge filters are used widely throu out process industries in the clarification of liquids. The media used include yams, papers, felts, binder-fi ee and resin-bonded fibres, synthetic fibres, woven wire, sintered metal powders and fibres, ceramics, etc. The inclusion of membraneous materials. Chapter 10, in cartridge constructions has extended the range of application of these ubiquitous dements so that partides firom approximate 500 pm down to 0.1 pm are separated. 

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