Solids Mixing Processes

In the experimental measurement of the solids mixing process, the radioactive particles were released from the top center of the cylindrical bed column into the bed free surface under each operating condition. The detector outputs were sampled at 50-ms intervals. A sample result of the average number of counts at each detector level was plotted versus time in Fig. 9.21 for the 500-pm glass particles at u0 = 54.8 cm/s (Moslemian, 1987). 

Note that each of these approaches is used by mixer equipment manufacturers, and this suggests that more research and development are required to increase our understanding of solids mixing processes. 

Mixing of sohds is an important unit operation in the production of solids with consistent properties. A number of properties of the solid particles influence the mixing process, the design, and selection of mixing equipment. The second subsection elaborates on the theoiy of mixing, types of mixing equipment, and their operation. 

The process steps listed in Table I9-I can sometimes be used to promote mixing. However, they are primarily for funcI ions other than solids mixing. (Note precautions for pneumatic conveying and vibrating in Table I9-I.)... 

Suspended solids are often the process objective that requires a specific degree of uniformity. Five guides to better liquid/solid mixing are ... 

Solid mixed ionic-electronic conductors (MIECs) exhibit both ionic and electronic (electron-hole) conductivity. Naturally, in any material there are in principle nonzero electronic and ionic conductivities (a i, a,). It is customary to limit the use of the term MIEC to those materials in which a, and 0, 1 do not differ by more than two orders of magnitude. It is also customary to use the term MIEC if a, and Ogi are not too low (o, a i 10 S/cm). Obviously, there are no strict rules. There are processes where the minority carriers play an important role despite the fact that 0,70 1 exceeds those limits and a, aj,i< 10 S/cm. In MIECs, ion transport normally occurs via interstitial sites or by hopping into a vacant site or a more complex combination based on interstitial and vacant sites, and electronic (electron/hole) conductivity occurs via delocalized states in the conduction/valence band or via localized states by a thermally assisted hopping mechanism. With respect to their properties, MIECs have found wide applications in solid oxide fuel cells, batteries, smart windows, selective membranes, sensors, catalysis, and so on. 

In this section, mixing processes will be considered under three separate headings gases, liquids and solids. 

MR Bolhuis, CF Lerk. Film forming of tablet lubricants during the mixing process of solids. Acta Pharm Technol 23 13-20, 1977. 

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