Agitators, scale

Figure 5-31. Design procedure for agitator scale-up. By permission, Rautzen, R. R., ef a/., Chem. Engr., Oct. 25,1976, p. 119 [32].

Establish predetermined end points using a sedation and agitation scale (see Tables 4.4 and 4.5)... 

Riker, R.R. Fraser, G.L. Simmons, L.E. Wilkins, M.L. Validating the sedation-agitation scale with the bi.spcctral index and visual analog scale in adult ICU patients after cardiac surgery. Intensive Care Med. 2001, 27, 853-858. 

Benz, G.T. (2008), Piloting bioreactors for agitation scale-up, Chemical Engineering Progress, 104(2) 32-34. 

TATTERSON Fluid Mixing and Gas Dispersion in Agitated Tanks TATTERSON Scale-up of Industrial Mixing Processes VVILLIG Environmental TQM... 

This situation is most probable with fairly intense agitation and on the small scale. On the other hand, for ease of appHcation, it is often assumed that no oxygen is utilized. This is the so-called no-depletion model. In this case... 

Until recently most industrial scale, and even bench scale, bioreactors of this type were agitated by a set of Rushton turbines having about one-thind the diameter of the bioreactor (43) (Fig. 3). In this system, the air enters into the lower agitator and is dispersed from the back of the impeller blades by gas-fiUed or ventilated cavities (44). The presence of these cavities causes the power drawn by the agitator, ie, the power requited to drive it through the broth, to fall and this has important consequences for the performance of the bioreactor with respect to aeration (35). k a has been related to the power per unit volume, P/ U, in W/m and to the superficial air velocity, in m/s (20), where is the air flow rate per cross-sectional area of bioreactor. This relationship in water is... 

In the simplest case, the feed solution consists of a solvent A containing a consolute component C, which is brought into contact with a second solvent B. Eor efficient contact there must be a large interfacial area across which component C can transfer until equiHbrium is reached or closely approached. On the laboratory scale this can be achieved in a few minutes simply by hand agitation of the two Hquid phases in a stoppered flask or separatory fuimel. Under continuous flow conditions it is usually necessary to use mechanical agitation to promote coalescence of the phases. After sufficient time and agitation, the system approaches equiHbrium which can be expressed in terms of the extraction factor S for component C ... 

The earliest large-scale continuous industrial extraction equipment consisted of mixer—settlers and open-spray columns. The vertical stacking of a series of mixer—settlers was a feature of a patented column in 1935 (96) in which countercurrent flow occurred because of density difference between the phases, avoiding the necessity for interstage pumping. This was a precursor of the agitated column contactors which have been developed and commercialized since the late 1940s. There are several texts (1,2,6,97—98) and reviews (99—100) available that describe the various types of extractors. 

Commercial-scale operations are conducted in batch, fed-batch, or continuous culture systems. Fermentation vessels include the conventional baffled aerated tank, with or without impeller agitation, and the ak-lift tower fermentors in which ak is sparged into an annular space between the... 

The constant may depend on process variables such as temperature, rate of agitation or circulation, presence of impurities, and other variables. If sufficient data are available, such quantities may be separated from the constant by adding more terms ia a power-law correlation. The term is specific to the Operating equipment and generally is not transferrable from one equipment scale to another. The system-specific constants i and j are obtainable from experimental data and may be used ia scaleup, although j may vary considerably with mixing conditions. Illustration of the use of data from a commercial crystallizer to obtain the kinetic parameters i, andy is available (61). 

Dry Cleaning. In colorfastness to dry cleaning, ISO 105-D01 a specimen of the textile is placed in a cotton fabric bag together with stainless steel disks and agitated in perchloroethylene (30 min, 20°C) and the effect of the shade and the color of the solvent assessed using the grey scale. 

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