Mixing time, measurement

Figure 10.3 Mixing time measured in SCISR and STR (PW pure water GW solution of...

From some of the data in this study, it was possible to estimate the influence of impeller type on mixing time. Table IV shows the estimated relative mixing times, with all other factors held constant. It is seen that impeller type has at most about a fourfold influence on the mixing times measured in this study. 

Approximate Mixing Time Measurement with Colorimetric Methods... 

After performing the decolorization technique to provide qualitative understanding of the mixing behavior, the method of mixing time measurement must be... 

Figure 4-15 Typical mixing time measurement probe positions.

All methods also assume that the liquid is well mixed. This can be checked by comparing the 90% mixing time (measured by the methods described earlier, but see Section 4-7.10) to the measured 90% mass transfer time (= 2.3/kLa). If the liquid is not well mixed, an interlinked zone model (see, e.g., Figme 4-30... 

Liquid-phase mixing time measurements can be made using the techniques described in the single-phase mixing section. Again the probes must be protected from interference from the gas bubbles. 

Otomo, N., W. Bujalski, and A. W. Nienow (1993). Mixing time measurements for an aerated, single- and double-impeller stirred vessel by using a conductivity technique, Proc. 1993 Institution of Chemical Engineers Research Event, Birmingham, Jan., pp. 669-671. 

All velocity measurements were carried out for a bath depth of //l = 80 x 10 " m although the mixing time measurements were done for H = 100 x 10 m. This difference did not cause any problem because the flow patterns for //l = 80x10 m and 100 X 10 m were nearly the same. 

Table 11-5 shows the mixing times for different sizes of reaetors used in penieillin fermentation with H/D = 2.5. The measured mixing time is eompared witli tlie ealeulated mixing time from Equation 11-102. The observed differenees in the measured and ealeulated t may be explained by the following ... 

Using an alternative approaeh to determine kineties, induetion time measurements were made in a reeent study of the well-mixed bateh preeipitation of... 

Several experimental techniques may be used, such as acid/base titration, electrical conductivity measurement, temperature measurement, or measurement of optical properties such as refractive index, light absorption, and so on. In each case, it is necessary to specify the manner of tracer addition, the position and number of recording stations, the sample volume of the detection system, and the criteria used in locating the end-point. Each of these factors will influence the measured value of mixing time, and therefore care must be exercised in comparing results from different investigations. 

There is a single assumption in these measurements--namely that the antibody only quenches free ligand. This has been demonstrated specifically by flow cytometry in experiments which show that there is no quenching of ligand on the cell (3). The kinetic analysis depends on rapid interaction of ligand and antibody, which in these experiments is essentially within the mixing time. 

A similar experiment was conducted using N-299 carbon black. In this case the premastication was limited to 3 min of mixing time. The average batch temperature measured after this mixing operation was 309°F. Each experiment was performed in duplicate the average of two mixes is shown in Figure 16.6. The viscosity of the final control compound was similar to that of the premasticated mbber. 

This homogeneous reaction is instantaneous and mixing is limited. As a consequence, at steady state, by measuring the required volume to complete the discoloring of iodine, it is possible to determine the global mixing time very easily. 

A related experiment TOCSY (Total Correlation Spectroscopy) gives similar information and is relatively more sensitive than the REIAY. On the other hand, intensity of cross peak in a NOESY spectrum with a short mixing time is a measure of internuclear distance (less than 4A). It depends on the correlation time and varies as . It is positive for small molecules with short correlation time (o r <<1) and is negative for macromolecules with long correlation time (wr >>l) and goes through zero for molecules with 1 Relaxation effects should be taken into consideration for quantitative interpretation of NOE intensities, however. 

The effectiveness of a number of crude oil dispersants, measured using a variety of evaluation procedures, indicates that temperature effects result from changing viscosity, dispersants are most effective at a salinity of approximately 40 ppt (parts per thousand), and concentration of dispersant is critical to effectiveness. The mixing time has little effect on performance, and a calibration procedure for laboratory dispersant effectiveness must include contact with water in a manner analogous to the extraction procedure otherwise, effectiveness may be inflated [587]. Compensation for the coloration produced by the dispersant alone is important only for some dispersants. 

Water content and viscosity measurements in certain systems show a correlation to emulsion stability [597]. The viscosity provides a more reliable measure of emulsion stability, but measurements of the water content are more convenient. Mixing time, agent amount, settling time, and mixing energy impact the effectiveness of an emulsifier. 

The temperature of the reaction mix was measured by a stainless steel-sheathed thermocouple inserted through the reactor cap. Heating up and cooling down times were small compared with the total reaction time. In all cases the free space in the reactor was flushed with nitrogen before sealing, and the reaction proceeded under a small initial nitrogen pressure. 

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