Particle size treatment processes

The initial sample is called the primary, or gross sample and may be a single increment drawn from the target population, or a composite of several increments. In many cases the gross sample cannot be analyzed without further treatment. Processing the gross sample may be used to reduce the sample s particle size, to transfer the sample into a more readily analyzable form, or to improve its homogeneity. 

Condensation of metal vapors followed by deposition on cooler surfaces yields metal powders as does decomposition of metal hydrides. Vacuum treatment of metal hydrides gives powders of fine particle size. Reaction of a metal haHde and molten magnesium, known as the KroU process, is used for titanium and zirconium. This results in a sponge-like product. 

In alloy steels, particularly if these have been slowly cooled after rolling, the carbides in the as-roUed condition tend to be massive and are difficult to dissolve on subsequent austenitization. The carbide size is subject to wide variations, depending on the rolling and slow cooling. Here, again, normalizing tends to estabUsh a more uniform and finer carbide particle size that faciUtates subsequent heat treatment. Although an expense, this process provides more uniform quaUty in the finished product. 

Most surface waters contain varying amounts of suspended solids, including silt, clay, bacteria, and vimses and it is necessary to remove these before to distribution to the domestic or industrial consumer. Suspended soHds not only affect the acceptabiUty of the water but also interfere with disinfection. The principal treatment processes are sedimentation (qv) and filtration (qv). Sedimentation alone is rarely adequate for the clarification of turbid waters and is of htde or no value for the removal of such very fine particles as clay, bacteria, etc. Table 1 shows the effect of particle size on the sedimentation rate of a soHd having a specific gravity of 2.65 in water at 20°C. 

Following wet processing, fine particle size kaolins may be calcined, ie, heat treated at about 1000°C. This treatment converts the kaolin to an amorphous pigment of significantly higher brightness and opacity (8). Properties of the various types of kaolins used in paper are shown in Table 2. 

The control of processes involving the treatment of solids generally requires means for careful samphng and analysis of solids and slurries at various points in an operation. Unlike liquids, particulate solids are not homogeneous. The composition of individual particles will vaiy with particle size and particle density. It follows that care must be... 

The processing of diatomite is unique, since its particle-size control is effected by calcination treatments and air classification. 

Tantalum powder with a smaller particle size compared with that obtained by the regular process was obtained by thermal treatment at 700-950°C of a mixture containing KTaF6, NH4F and sodium [581]. Eighty three percent of the tantalum powder obtained appears to be smaller than 200 mesh. 

In the polymer industry, post-reaction product treatment processes such as liquid-solid separation, drying, precipitation, particle size control, and polymer purification are very complex and costly. Future polymer plants should be designed such that process equipment can be easily and quickly converted to making new products at minimal cost and with... 

Table 1 shows that the physicochemical properties of the support material were modified by the pre-treatment process. The particle sizes. Dp, which are summarized in the Table 1 were calculated from the X-ray diffraction patterns of prepared catalysts and a commercial catalyst(30 wt% Pt-Ru/C E-TEK) by using Scherrer s equation. To avoid the interference from other peaks, (220) peak was used. All the prepared catalysts show the particle sizes of the range from 2.0 to 2.8nm. It can be thought that these values are in the acceptable range for the proper electrode performance[7]. For the prepared catalysts, notable differences are inter-metal distances(X[nm]) compared to commercial one. Due to their larger surface areas of support materials, active metals are apart from each other more than 2 3 times distance than commercial catalyst. Pt-Ru/SRaw has the longest inter-metal distances. 

The filter-cake formed in this process, however, is highly dispersible to the produced fluid and thus is effectively removed by placing the well on production. No acid treatment or other removal techniques are required. The primary bridging agent in this fluid is a sized calcium carbonate with particle sizes capable of initiating bridging in pore diameters in excess of 100 p. 

Manufacturing processes afford azo pigments with, for instance, certain defined physical forms. Thermal treatment usually increases the particle size, reduces the tinctorial strength, and may improve the hiding power of a pigment. Reversal of... 

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