Agitation requirement

Agitated reactor (possibly with catalyst particles) Catalytic and noncatalytic Reactions, polymerizations (special agitator required) High transport rates, convenient to operate, easy variation of parameters, most versatile Catalyst erosion... 

The power requirements for agitation will depend on the degree of agitation required and will range from about 0.2 kW/m3 for moderate mixing to 2 kW/m3 for intense mixing. 

Upon determination of design settling velocity, one must choose the scale of agitation required using Table 5 (9), which serves as the suspension products equivalent of Table 3. 

As homogeneous suspension in nonaerated stirred vessels can hardly be achieved, even with very high stirrer speeds, mainly Nc, needed for complete suspension, is of interest for the design purposes. This value, by definition, is characterized by the just-suspended criterion, i.e., the state where only a small fraction of the solids remains at the bottom of the reactor for one second at maximum (Einenkel, 1979). Zwietering (1958) proposed the following correlation to predict Nc, the minimum rotational speed of agitation required for the complete suspension ... 

The power in aerated slurry reactors in regime c can be calculated using Equation (3.3). In general, relations summarized by Baldi (1986) can be used for the calculation of power consumption. The most widely used correlation for the minimum rotational speed of agitation required for complete suspension of solids is that of Zweitering (Equation (3.6)). The most versatile... 

FIG. 14.17 Agitation requirements to redisperse settled solids. (From Oldshue, J.Y., Fluid Mixing Technology, McGraw-Hill, New York, 1983, p. 234.)... 

Disadvantages Draft tube subject to fouling if liquid level is too low. Internal beffles. supports, mixer, and so on clutter up internals. Internal agitator requires maintenance. 

Agitator power requirements for ungassed systems Agitator requirements for gas-liquid dispersions Temperature tank diameter Volume of reactor contents Superficial gas velocity... 

The design firm normally generates procurement specifications. These specifications will include definition of all major components such as materials of construction, agitator requirements, nozzles, etc. Major equipment for API processing is similar to fine chemical production and can include reactors, centrifuges, condensers, heat exchangers, distillation columns, extractors, absorption equipment, chromatography equipment, dryers, blenders, crystallizers, mills, etc. These components wiU normally require validation [installation... 

Radial flow impellers are significantly more energy demanding for solid suspension compared to axial flow ones. However, since a = 1.3./ js so that a relatively large, low speed agitator requires the least power. Once again DIT ratios > should be avoided for the Rushton turbine. With a low clea-... 

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