Ceramic disc filters

Figure 11.14 Ceramic disc filters c jillary pressure control (Outokumpu Mintech Oy, Espoo, Finland) Table 11.4 Vacuum filter productivity ...

The study of the influence of the reaction time for urea decomposition and the urea concentration in the urea method was performed on a-Al203 powder rather than a ceramic filter disc since the supply of the ceramic discs was limited. Experimental details have been reported elsewhere [11], To investigate the role of the reaction time, the urea/nickel molar ratio was fixed at a value of 1.3. The results are shown in Fig. 1. The precipitation amount of nickel precursor and the suspension pH both increased with reaction time. The amount of nickel precipitate sharply increased during the first 6 h reaction time and increased slowly after 6 h. This suggested that at least 6 h reaction time was needed to fix a reasonable amount of precursor on the support during the wet stage of the urea method. The nickel precipitate was identified By analysis as Ni3(N03)2(0H)4 in all cases. 

Figure 1.27 Schematic side view of a rotary disc vacuum filter [left) and photograph, with permission from Ceramec, of a multiple disc filter installation fitted with ceramic elements (right).

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,... 

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... 

This novel route involves the retention of colloidal dispersions of zeolites (silicalite-1 described here) onto the surface of macroporous ceramic substrates. Silicalite-1 colloids were synthesised as described by Schoemann [14]. These were characterised by SEM and filtered through ceramic alumina discs. 

Some a-Al203-based filter discs (Schumacher, Germany) were vacuum impregnated with a solution containing appropriate amounts of nickel nitrate and urea. After the excess solution was drained off, the discs were placed in a closed vessel and kept at 90 °C for a certain period, resulting in precipitation of nickel precursor by the slow hydrolysis of urea in the pores of the discs. After reaction, the filter discs were dried at 110 °C for a few hours and calcined at 450 °C for 4 h. Then the nickel-modified ceramic filter discs were obtained. For the conventional impregnation method, other steps and experimental conditions were identical to the preparation procedure with the urea method except for the absence of urea in the impregnation solution. 

Rotary disc vacuum filter, ceramic None 4C 9 0 8 21 1-700 5-20... 

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. 

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