Solid mixing measures

Westphalen D, Glicksman L. Lateral solids mixing measurements in circulating fluidized beds. Powder Technol 82 153-168, 1995. 

Rhodes et al. (1991) conducted RTD measurements to study longitudinal solids mixing in a circulating fluidized-bed riser by pulse-injection of a sodium chloride tracer. 

Vazquez and Calvelo (1983b) presented a model for the prediction of the minimum residence time in a fluidized bed freezer which can then be equated to the required freezing time. The model is defined in terms of a longitudinal dispersion coefficient D, which is a measure of the degree of solids mixing within the bed in the direction of flow (and has the dimensions of a diffusivity, and hence units of m s ), a dimensionless time T... 

For gas velocities ranging 4.1 to 6.3 m/s, the measured axial solids dispersion coefficients Ds varied from 0.39 to 0.91 m2/s for dilute solid suspension, while for the whole fast bed, in the same gas velocity range, Ds was 0.22 to 1.67 m2/s. Axial solid dispersion coefficient generally increases with both gas velocity and solids circulation rate. Milne and Berruti (1991) have also given their own model for solids mixing. 

Next we shall describe some of the objectives used in sample pre-treatment. The objective of these procedures is to reduce the volume of the samples. Portioning, evaporation concentration, chemical separation, absorption and so forth are techniques used alone or in an appropriate combination for liquid samples. Drying, sieving, pulverisation, mixing, reduction, ashing and so forth are techniques used alone or in an appropriate combination, for preparing samples of solids for measurement. 

For most solids mixing problems, the measure of central tendency and measure of variation will be of greatest use. Therefore these will be defined and tests of significance given for them. Measures of skewness or peakedness can be found elsewhere (H5) if the occasion demands. 

Fig. 38. Relation between degree of mixing and number of revolutions for various conditions of baffling. 20 cm. X 40 cm. horizontal cylinder rotating at 25 rpm. Black and white particles of about 1.3 mm. diameter mixed. Degree of mixing measured photometrically. Total weight of solid is 8 kg. h = height of baffle plate, R = radius of cylinder (04).

A new chapter on membrane separations has been added, and the order of the chapters on multicomponent distillation, extraction, drying, and crystallization has been made more logical. The discussion of particulate solids has been shortened and two former chapters on properties and handling of solids and of solids mixing have been combined into one. New material has been added on flow measurement, dispersion operations, supercritical extraction, pressure-swing adsorption, crystallization techniques, crossflow filtration, sedimentation, and many other topics. The treatment of dimensional analysis has been condensed and moved from the appendixes to Chapter 1. 

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). 

Frequencies in cm [55] [56] [57] [11] Strongly coupled with the ring puckering for the deuterated isotopomer. Strong mixing between CH rock and CC stretch for the deuterated isotopomer. Taken from solid state measurements, wavenumbers should be considered only approximate. 

The thermodynamic behaviour of polymer solutions has been the subject of extensive study, partly because of the importance of surface coatings such as lacquers and paints, and partly because it is essential to understand the behaviour of polymers in solution in order to quantitatively characterize the polymers and copolymers. Furthermore, it is also not possible to understand the behaviour of polymer-polymer systems (blends and alloys) without some understanding of polymer-solvent systems. There is a close relationship between the way in which amorphous solids mix and the behaviour of polymers in solution polymer solutions are much more amenable to experimental measurements. 

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