Ceramic Foam Filters

The lowest balance point temperature was measured with a combination of platinum and cerium fuel additives with a platinum treated ceramic foam filter placed... 

Potassium- and strontium-substituted praseodymium manganate Pro,7Sro,2Ko,iMn03 perovskite-type catalysts were explored in supported form on ceramic foam filters for soot oxidation in typical conditions of a diesel engine [55]. Compared to bare soot oxidation reaction, the soot oxidation in the presence of these catalysts corresponded to a decrease of the Tinitiai value by 150 °C and Tfinai value by 100 °C. Besides the activity, another advantage of the system is the very good thermal stability. 

Teraoka, Y., and Labhsetwar, N. (2013) Bench scale experiments of diesel soot oxidation using Pro,7Sro.2Ko.iMn03 perovskite type catalyst coated on ceramic foam filters. Top. Catal, 56 (18), 457-461. 

We have also acquired some samples of ceramic foam filters of veiy high gas permeability and we are currently attempting to acquire some ceramic honeycomb catalysts of the type used in certain wood stoves and related applications. We plan to try out these later. 

Ceramic foam filters are widely used for the filtration of A1 alloys from oxide films, and they also purify A1 from gases and intermetallic inclusions due to their big surface area. Usually, they have the shape of torque bricks with a height of 50 mm and sides of 200 mm, 230 mm, 325 mm, 400 mm, 525 mm, and 585 mm, but sometimes they have a cylindrical shape. The filtration box may be with or without preheating. The main characteristic of ceramic foam filters is the number of pores per inch (ppi). Filters with 20, 30, 40, 50, and 60 ppi are used in aluminium cast houses. The most common are filters with 30 and 40 ppi. Filters with 60 ppi are used for the filtration of special alloys. 

With the system studied, NO, reduction up to 20% was measured. This reduction could possibly be optimised using the right filter geometry, for example with a ceramic foam. 

We designate as composite (combined) such systems as are formed by combination of growth and addition systems. As a rule, such systems are produced both by the addition of individual elements and through growth of the individual elements (e.g. pore formation or foaming). Composite systems are, for exemple, ceramics, foam glass, fabrics, Gouch filters, membrane filters, most construction materials, metallic or polymeric cakes, etc. 

The second technique is based on a filter to capture the soot particulates. Common filters are wall flow monoliths or ceramic foams. Cordierite wall flow monoliths are probably currently the most used particulate traps. They can capture diesel particulates with an efficiency of 99%. At normal diesel engine exhaust gas temperatures, the captured soot is not reactive enough to prevent build up on the filter, with an intolerable high pressure drop over the exhaust system as a result. The oxidation rate of the soot should, therefore, be increased which can be achieved by increasing the temperature of the filter, resulting in higher fuel consumption and thus making this solution unfavourable. The other possibility is catalytic oxidation of the collected soot. Several catalytic systems will be discussed. 

The liquid state of the catalyst might also result in higher particulate capture by materials that are normally poor soot filters, for example ceramic foams. The micro porous structure can retain the molten salt, while the surface is covered with liquid catalyst, causing the soot particulates to stick. 

For successful application, a technology has to be developed to bring the soot into contact with the catalyst without losing the catalyst during operation. Ceramic foams impregnated with a molten salt or dedicated catalyst/filter systems are thought to be promising candidates for this application. 

Fig. 19. Microstructure of a SiC foam ceramic for filters and other applications [283]...

Catalyzed ceramic foam as a catalytic diesel particulate filter is an application different from other tems discussed in this paper. Here high temperattoe resistance and low bulk density are important, but tortuous flow paths together with open porosity are key features. As with conventional monolithic catdysts, cordierite foams have been used because of the very low thermal coefficient of e q)ansion [40-45]... 

Thick media cartridges can then be made by fixing a layer of plastic foam to a perforated core. A major alternative use is the formation of coarse ceramic foams, as discs, to be used as filters in the removal of contaminants from molten metal. 

Ceramic Filter. The ceramic filter collects, volatilizes, and destroys particulates and condensible organics emitted from industrial process streams, such as paint spray, lost foam casting, condensible organics, tenter frames, and cured rubber... 

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. 

To overcome this challenge, other filter designs and construction materials were tested, such as packed-bed filters [41], foam ceramic filters [39, 42—44], sintered ceramic filters [18, 45, 46], candle-type filters made from metal or ceramics [22, 47], or honeycomb structures made from steel [48]. Among the construction materials, the performance of high-temperature ceramics, such as SiC, Zr02, or SiC>2, was investigated [18, 45, 46, 49],... 

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