Filtration ceramic filters

The small particles are reported to be very harmful for human health [98]. To remove particulate emissions from diesel engines, diesel particulate filters (DPF) are used. Filter systems can be metallic and ceramic with a large number of parallel channels. In applications to passenger cars, only ceramic filters are used. The channels in the filter are alternatively open and closed. Consequently, the exhaust gas is forced to flow through the porous walls of the honeycomb structure. The solid particles are deposited in the pores. Depending on the porosity of the filter material, these filters can attain filtration efficiencies up to 97%. The soot deposits in the particulate filter induce a steady rise in flow resistance. For this reason, the particulate filter must be regenerated at certain intervals, which can be achieved in the passive or active process [46]. 

The separation method targets recovery of the aqueous phase from oil/water mixtures of microbial reactions by filtration through a ceramic filter module [154], The invention particularly referred to a two-phase system resulting from a process used for production of 2,6-naphthalenedicarboxylic acid using S. paucimobilis AK2M16 (PERM P-13996). The aqueous phase is said to be recovered free of microbial cells and oil. Although, it is mentioned that the reaction product can be recovered readily in high yield, the need for an additional unit operation looks obvious. 

High-temperature gas cleaning (in particular, gas filtration using metal or ceramic filters and also the removal of especially sulfur species)... 

Pall Process Filtration Ceramic Candle Filter 1000°C (max.) 99.99% Supported both sides clay bonded silicon carbide filter... 

Examples of computer reconstructed DPF porous media are given in Fig. 5 and encompass all currently available filtration media extruded ceramic filters (including reaction formed media as cordierite and grain-sintered media as SiC), fibrous filters, foams and sintered metal powder/wiremesh. 

The honeycomb configuration of ceramic filters offers a high surface area per unit volume, thereby permitting a compact filter size [12]. The absolute filtration surface area depends on cell size, filter volume, and the plugging pattern, all of which are design parameters whose optimization, as will be shown shortly, calls for trade-offs in pressure drop, filtration efficiency, mechanical durability, thermal integrity, and space availability. 

Heidenreich S and Scheibner B. Hot gas filtration with ceramic filters Experiences and new developments. Filtr. Sep. 2002 May 22-25. Heidenreich S and Wolters C. Hot gas filter contributes to IGCC power plant s reliable operation. Filtr. Sep. 2004 June 22-25. Larbot A, Bertrand M, Marre S, and Prouzet E. Performances of ceramic filters for air purification. Sep. Purif. Technol. 2003 32 81-85. DeFriend KA and Barron AR. A simple approach to hierarchical ceramic ultrafiltration membranes. J. Membr. Sci. 2003 212 29-38. Endo Y, Chen D-R, and Pui DYH. Collection efficiency of sintered ceramic filters made of submicron spheres. Filtr. Sep. 2002 March 43-47. Sakol D and Konieczny K. Application of coagulation and conventional filtration in raw water pre-treatment before microfiltration membranes. Desalination 2004 162 61-73. 

The ceramic filter showed good filtration efficiency, with stable pressure drop. However, after more than 1200 hours of trouble free operation suddenly two ceramic candles broke. The difficulty to detect a relatively small failure in a hot gas filter was then noticed in practice even though no serious damage was caused. 

For particle cleanup cyclones, impact separators, fabric and fiber filters, granular beds, and electrostatic percipitators for low-temperature gas cleaning have been widely used in the industry. However, for hot gas filtration with ceramic filters, the long-term durability, alkali corrosion, cleanability, thermal shock, and particulate penetration into filter media has been recognized as major concerns. Traditional bag filters are sensitive to high ten erature and hot particles, electrostatic percipitators have a relatively high cost of installation in smaller plants and multi-cyclone cleaners are not sufficiently efficient to meet the new purification demands. 

OperationaUy, there are several ways to start up the system (1) ibuprofen and lysine can be mixed in a separate tank/transfer vessel and then added or (2) the contents of the system at the end of one run can be saved for the next. It was decided to charge a slurry of diastereomers to be separated to the dissolver at the beginning. The slurry in the dissolver was continuously filtered via a ceramic crossflow filter of 0.2 p,m pore size. The supersaturated permeate was transferred to the crystallizer. Simultaneously, the slurry in the crystallizer could be filtered via another ceramic filter, and the clear saturated (with respect to S-ibu-S-lys) permeate filtrate could be sent to the dissolver. Both permeates would be kept at the same rate to maintain the volumes in both the dissolver and crystallizer. However, fluidized bed operation was clearly more convenient. Table 7-3 summarizes the results of two kilogram-scale experiments. As shown in the table, the final optical purity of S-ibu-S-lys is greater than 98%, starting with 50% S-ibu-S-lys and 50% R-ibu-S-lys in the dissolver. 

Waste Minimization and Disposal. CFF systems minimize disposal costs (e.g., when ceramic filters are used) whereas in diatomaceous (DE) pre-coat filtration substantial waste disposal costs may be incurred, particularly if the DE is contaminated with toxic organics. Currently, in many applications, DE is disposed of in landfills. In future, however, this option may become less available forcing the industry to use cross-flow microfiltration technology or adopt other waste minimization measures. 

Table 11 shows the performance of polymeric and ceramic filters for the separation and concentration of yeast and E-coli suspensions. The ceramic filters, due to their superior mechanical resistance, can be backpulsed to reduce flux decline during concentration. This is illustrated in Fig. 19 for the filtration of yeast suspension with 0.45 pm microporous cellulose triacetate membrane. Polymeric membranes can be backwashed at pressures up to about 3 bar. The data in Fig. 20 show the flux improvement with backpulsing using 0.2 pm microporous alumina membrane. ... 

Table 12 shows the typical LRV values obtained using a polymeric and ceramic microfilter. Sterile filtration requires 100% bacteria retention by the membrane, whereas in many industrial bacteria removal applications the presence of a small quantity of bacteria in the filtrate may be acceptable. For example, drinking water obtained by microfiltration may contain nominal counts of bacteria in the filtrate which is then treated with a disinfectant such as chlorine or ozone. The use of ceramic filters may allow the user to combine the sterile filtration with steam sterilization in a single operation. This process can be repeated many times without changing filters due to their long service life (5 years or longer). 

Air filtration with ceramic filter, spring loaded, steam sterilizable Peristaltic pumps for low delivery capacity and sterile operation O-ring packings for piping and reactor parts... 

S. Heidenreich, and B. Scheibner, Hot Gas Filtration with Ceramic Filters Experiences and New Developments, Fillr. andSeparat., 39, 22-5 (2002). 

Inclusions in steel can arise from slag entrapment, the erosion of fiimace or ladle linings or refractories, or from deoxidation. Filtration is now widely used to reduce the presence of inclusions. The introduction of ceramic filters has even enabled simplifications to be made in the design of running and gating systems. Various tj es of filters are shown in Figure 2.27. 

Heidenreich S and Scheibner B. Hot gas filtration with ceramic filters Experiences and new developments. Filtr. Separat. 2002 39 22-25. 

Simeone, E Nacken, M., Haag, W. et al. (2011) Filtration performance at high temperatures and analysis of ceramic filter elements during biomass gasification. Biomass and Bioenergy, 35, S87-S104. 

Zhang, W Park, B. C., Chang, Y. K., Chang, H. N., Yu, X. J., Yuan, Q. (1998). Factors affecting membrane fouling in filtration of Saccharomyces cerevisiae in an internal ceramic filter bioreactor. Bioprocess Engineering, 18, 317—322. 

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. 

Filters for Molten Metal Inclusions in molten metals, such as oxide skins, mold sand particles, inoculation reaction byproducts or furnace slags, can be efficiently removed by filtering through pressed cellular, extruded cellular, or foam ceramic filters manufactured from high-temperature-resistant, chemically inert alumina, and also mullite, silicon carbide, and stabilized zirconia. Alumina is particularly useful when filtering liquid aluminum alloys in the range of 750-850 °C, and copper-based alloys at 1000-1200°C (Matthews, 1996). These ceramic filters are designed for use in either batch or in-mold filtration ... 

For in-mold filtration, the ceramic filter is placed across one of the channels of the mold. Since, in this design, the melt is filtered immediately before solidifying inside the mold, the cleaning efficiency is very high. 

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). 

Metal fibre felts are manufactured with a three dimensional textile-like surface and can withstand heavy dust load and high air flow speeds. They are used where temperatures range from 300 to tiOO C for low pressure-high volume and high pressure-low volume reverse air cleaning. Ceramic filter elements made from ceramic fibres with inorganic reinforcement are used in extreme conditions for continuous operating temperatures up to OOti C. Filtration efficiency can be in the order of 99.99% with a maximum pressure drop of lOOmbar. 

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... 

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