Ceramic filter media

Gillot, J. and D. Garccra. 1984. New ceramic filter media for cross-flow microfiltration and ultrafiltration. Paper presented at Filtra 84 Conference, 2-4 October 1984, Paris. 

Ceramic filter media are manufactured from crushed and screened quartz or chamotte, which is then thoroughly mixed with a binder (for example, with silicate glass) and sintered. Quartz media are resistant to concentrated mineral acids but not resistant to low-concentration alkalies or neutral water solutions of salts. Chamotte media are resistant to dilute and concentrated mineral acids and water solutions of their salts, but have poor resistance to alkali liquids. 

The rough surface of ceramic filter media promotes adsorption of particles and bridging. Sintering of chamotte with a binder results in large blocks from which filter media of any desired shape can be obtained. Using synthetic polymers as binders, ceramic filter media that do not contain plugged pores are obtained. 

J. Gillot, G. Brinkman, and D. Gareera, New Ceramic Filter Media for Cross-Flow Mierofiltration and Ultrafiltration, S.C.T. Ceramic Membranes, Tarbes, France. 

High temperature filter systems (using a ceramic filter medium) These are available on the market but not currently applied in the foundry industry... 

When the pressure rises to the permissible maximum, the cartridge must be opened and the element replaced. Micronic elements of the fiber type cannot be cleaned and are so priced that they can be discarded or the filter medium replaced economically. Stone elements usually must be cleaned, a process best accomplished bv the manufacturer of the porous ceramic or in accordance with the manufacturer s directions. The user can clean stainless-steel elements by chemical treatment. 

The filter medium can be fibrous, such as cloth granular, such as sand a rigid solid, such as a screen or a mat, such as a felt pad. It can be in the shape of a tube, sheet, bed, fluidized bed, or any other desired form. The material can be natural or man-made fibers, granules, cloth, felt, paper, metal, ceramic, glass, or plastic. It is not surprising that filters are manufactured in an infinite variety of types, sizes, shapes, and materials. 

The cooled syngas is filtered using ceramic filters. About 50% of the cooled syngas is then recycled to the top of the gasifier to act as the quenching medium for the gas. The remainder is washed to remove halides and NH3 and then sent to the downstream AGR system. 

Use Dyeing mordant, water purification, waterproofing fabrics, manufacture of lakes, filtering medium, chemicals (aluminum salts), lubricating compositions, manufacture of glass, sizing paper, ceramic glaze, antacid. 

Use Rubber filler ceramics, glass, refractories absorbent for crude oil spills manufacture of permanently dry resins and resinous compositions paints, varnishes, and paper (filler) animal and vegetable oils (bleaching agent) odor absorbent filter medium catalyst and catalyst carrier anticaking agent in foods. 

In cross-flow flltration, the wastewater flows under pressure at a fairly high velocity tangentially or across the filter medium. A thin layer of solids form on the surface of the medium, but the high liquid velocity keeps the layer from building up. At the same time, the liquid permeates the membrane producing a clear filtrate. Filter media may be ceramic, metal (e.g., sintered stainless steel or porous alumina), or a polymer membrane (cellulose acetate, polyamide, and polyacrylonitrile) with pores small enough to exclude most suspended particles. Examples of cross filtration are microfiltration with pore sizes ranging from 0.1 to 5 pm and ultrafiltration with pore sizes from 1 pm down to about 0,001 pm. 

Modem developm ts aimed at avoiding such effects involve the use of high-porority, smaD-pore ceramic filters wdiich use the inherently high capillary pressure of such materials to avoid gas entry into the medium. This materially reduces the cost of con ression power in filters dewatered by conqiressed air. 

Continuous layer filtration involves filtering the sugar syrup through a layer of activated carbon. Several types of filters are used, such as pressure leaf filters with metal frames on which a filter cloth that may be cotton, polyamide, or wire mesh is fixed rotary leaf filters or bed filters in which the filtering medium is a ceramic or sintered plate, wire mesh, or finely perforated metal plate. The latter filters are usually coated with a layer of filter aid that may be a diatomaceous earth. A suspension of active carbon in water or liquor is passed through the filter until a uniform layer of active carbon bed 10 to 15 mm thick builds up. The filter is then ready for filtration of the liquor that must flow to the filter at a uniform rate to avoid breaking the layer. 

The capillary disc filter looks like any other standard rotary vacuum disc filter, as can be seen in Figure 3.25, but the filter medium is a finely porous ceramic disc, which draws filtrate through the disc material by capillary action, under the applied vacuum. The filter discs are made of sintered alumina with uniform micropores less than 1 pm in size, which allows only liquid to flow through it. Despite an almost absolute vacuum, no air penetrates the filter material. The disc material is inert,... 

Ceramic powders can be sintered into a wide variety of porous shapes for use as filter elements. In the form of porous pottery, ceramics were one of the earliest materials used for filtration. Porous ceramic filters for use as cartridges are generally in the form of a plain cylinder with a thick wall, the thickness of which provides the depth of filter medium for retention of the solids in a filtration process. As far as tubular elements are concerned, these are either plain cylinders (i.e. open at both ends) or flanged candles (i.e. candles with a flange on the open end for fixing in the cartridge housing or to the tube plate of a candle filter). 

Originally implying a thin, microporous or semi-permeable plastic sheet, the term membrane is now applied to any filter medium that is capable of removing particles below 0.1 am. The membrane represents probably the fastest growing part of the filtration media market (especially if ceramic membranes for hot gas filtration are included). 

An interesting extension of the range of vacuum filters is the capillary disc filter (Figure 4.26). This is a continuously operating, capillary action, ceramic dewatering filter, which eliminates the need for separate filter cloths. The filter medium is a disc, formed from two circles of sintered alumina, joined at their circumferences. The filter has several such discs mounted on a central horizontal shaft. The medium is practically inert in most solutions, and may be used in a broad range of water-based and solvent-based slurries. In operation, as the microporous ceramic discs rotate through... 

Ceramic filter candles have a greater tolerance to temperatures above 1000°C. They combine high burst strength and thermal shock resistance with high permeability, high filtration efficiency and corrosion resistance, in a rigid silicon carbide medium. They remove and/or recycle catalysts from any catalytic reaction system... 

Backwashable cartridge filters are available in a variety of designs using metal screens, permeable ceramic, or consolidated sand as a filter medium. Filters of this type are simple and lightweight hke the disposable cartridge filters, but they have the additional advantage of being backwashable. The media used in backwashable filters typically provide filtration of particles between 10 and 75 pm. 

Filtered-Particle Inspection. Solids containing extensive inteiconnected porosity, eg, sintered metallic or fired ceramic bodies formed of particles that ate typically of 0.15-mm (100-mesh) screen size, are not inspectable by normal Hquid penetrant methods. The preferred test medium consists of a suspension of dyed soHd particles, which may be contained in a Hquid vehicle dyed with a different color. Test indications can form wherever suspensions can enter cracks and other discontinuities open to the surface and be absorbed in porous material along interior crack walls. The soHd particles that form test indications ate removed by filtration along the line of the crack at the surface where they form color or fluorescent indications visible under near-ultraviolet light (1,3). 

Silver membranes have been used as filters to collect clays or soils in a dispersion medium and then as an XRD substrate. In a typical analysis for mineral contents, a clay or soil is dispersed in water and vacuum filtered on the membrane. The silver membrane in this case has an advantage over ceramic membranes in that the XRD patterns of the minerals are distinctively different from that of silver. In conuast, the i>attems of the... 

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