Agitation equipment selection

For scale-up procedure, refer to Figure 5-31, w hich outlines the steps involved in selecting commercial or industrial mechanical agitation equipment when based on test data. 

Equipment selection is important, as is also the proper operation of the contacting devices. It is generally recognized that high shear is the primary cause of droplet haze and subsequent emulsion and crud formation. Thus, the type and amount of agitation (shear) must be optimized for mass transfer while minimizing emulsion and crud formation. Table 7.5 indicates items of information that may be required in analysis of crud formation problems in a plant [32]. 

Figure 7-9. Agitator flow patterns, (a) Axial or radial impellers without baffles produce vortex, (b) Off-center location reduces the vortex, (c) Axial impeller with baffles, (d) Radial impeller with baffles. (Source Walas, S. M., Chemical Process Equipment—Selection and Design, Butterworths Series in Chemical Engineering, 1988.)...

The processing equipment used to conduct solvent extraction of metals is the same as that used in conventional liquid-liquid extraction.1 1 The most common choices have been mixer-settlers, columns with agitated internals, and static mixers. Some advantages and disadvantages of several classes of equipment are summarized in Table 8.5-1. Many of the practical aspects of equipment selection are diicussed by Pratt and Hanson5 and by Ritcey and Ashbrook. ... 

The thermal duty here is the opposite of solidification operations. The indirect heat-transfer equipment suitable for one operation is not suitable for the other because of the material-handling rather than the thermal aspects. Whether the temperature of transformation is a definite or a ranging one is of little importance in the selection of equipment for fusion. The burden is much agitated, but the beds are deep. 

Pai+icle size enlargement equipment can be classified into several groups, with advantages, disadvantages, and applications summarized in Table 20-36. Comparisons of bed-agitation intensity, compaction pressures, and product bulk density for selected agglomeration processes are highlighted above in Fig. 20-71. 

The reactor volume is taken as the volume of the reactor physically occupied by the reacting fluids. It does not include the volume occupied by agitation devices, heat exchange equipment, or head-room above liquids. One may arbitrarily select the temperature, pressure, and even the state of aggregation (gas or liquid) at which the volumetric flow rate to the reactor will be measured. For design calculations it is usually convenient to choose the reference conditions as those that prevail at the the inlet to the reactor. However, it is easy to convert to any other basis if the pressure-volume-temperature behavior of the system is known. Since the reference volumetric flow rate is arbitrary, care must be taken to specify precisely the reference conditions in order to allow for proper interpretation of the resultant space time. Unless an explicit statement is made to the contrary, we will choose our reference state as that prevailing at the reactor inlet and emphasize this choice by the use of the subscript zero. Henceforth,... 

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