Agitation rate

Because PEA is such an important fragrance material this simple, essentially one-step process has been exhaustively studied to optimize reaction conditions and purification procedures. Because of the high reactivity of the iatermediates and the tendency toward polymer formation, critical factors such as throughput, temperature, molar ratios of reactants, addition rates, reactor materials and design, and agitation rate must be carefully balanced to provide an economical product with acceptable odor properties. 

Saturation of the oil with hydrogen is maintained by agitation. The rate of reaction depends on agitation and catalyst concentration. Beyond a certain agitation rate, resistance to mass transfer is eliminated and the rate oecomes independent of pressure. The effect of catalyst concentration also reaches hmiting values. The effects of pressure and temperature on the rate are indicated by Fig. 23-34 and of catalyst concentration by Fig. 23-35. Reaction time is related to temperature, catalyst concentration, and IV in Table 23-13. 

Thus, a plot of IjN against t is a straight line (Figure 6.13) and is independent of the agitation rate. Perikinetie motion is generally thought to apply to partieles of less than ea. 1-10 pm, depending on the partiele-fluid motion. 

A plot of In A against t thus yields a straight line (Figure 6.14) the slope of which depends on agitation rate. 

Carbon dioxide gas diluted with nitrogen is passed continuously across the surface of an agitated aqueous lime solution. Clouds of crystals first appear just beneath the gas-liquid interface, although soon disperse into the bulk liquid phase. This indicates that crystallization occurs predominantly at the gas-liquid interface due to the localized high supersaturation produced by the mass transfer limited chemical reaction. The transient mean size of crystals obtained as a function of agitation rate is shown in Figure 8.16. 

The data plotted in the figure clearly support the predicted positive dependence of crystal size on agitation rate. Precipitation in the crystal film both enhances mass transfer and depletes bulk solute concentration. Thus, in the clear film model plotted by broken lines, bulk crystal sizes are initially slightly smaller than those predicted by the crystal film model but quickly become much larger due to increased yield. Taken together, these data imply that while the initial mean crystal growth rate and mixing rate dependence of size are... 

Figure 8.16 Measured dependence ofCtiCO crystal size on agitation rate Jones etai, I992h)...

Table 2.3. Effect of agitation rate on baker s yeast production...

Agitation rate, rpm DO, mg/1 Optical density, absorbance, A520 nm Cell dry weight, mg/ml Protein concentration, mg/1 Sugar concentration, g/1... 

The power per unit volume is constant. From power consumptions in a bench-scale bioreactor, the necessary agitation rate is calculated for the scale up ratio, using Equation (13.2.1). The choice of criterion is dependent on what type of fermentation process has been studied. The following equation expresses relations for the impeller size and agitation rate in small and large bioreactors. 

The agitation rate is proportional to impeller diameter to the power of 2/3. 

In a mixed agitated vessel with high agitation rate, at the centre of the vessel a vortex often forms. To prevent a central vortex in tanks less than 3 m in diameter, four baffles each with a baffle width of 15-20 cm are necessary. A basic assumption is to select a ratio of liquid height to tank diameter from 2 1 to 6 1. 

For constant power input based on geometric similarity of the vessels, agitation rate is calculated. 

The bioreactor will be scaled up by a factor of 125. It is necessary to discuss the effect of operating variables resulting from constant power per unit volume, agitation rate, and speed tip velocity, NRe. The data for a small-scale bioreactor are a 100 litres fermenter with 187.5 rpm and... 

Since we assumed power per unit volume is constant, it is possible (NIDI)] may not be equal with Now calculate the agitation rate for a large vessel. 

Tlie power for laminar flow is proportional to agitation rate, N2, and if the flow is turbulent the power is proportional to N3Dt2. Let us assume the mass transfer coefficients remain constant (Kha unchanged) ... 

Westerterp et al. (W5) measured interfacial areas in mechanically agitated gas-liquid contactors. The existence of two regions was demonstrated At agitation rates below a certain minimum value, interfacial areas are unaffected by agitation and depend only on nominal gas velocity and the type of gas distributor, whereas at higher agitation rates, the interfacial areas are... 

At agitation rates above some minimum agitation rate. 

For chemical reaction-rate constants greater than 10 sec-1, NT increases linearly with the total bubble surface area, i.e., linearly with the gas holdup. In other words, the agitation rate only affects the total bubble surface area and has almost no effect on the rate of absorption per unit area. This result is in accordance with the work of Calderbank and Moo-Young (C4), discussed in Section II. 

A shaker tube equipped with a 1200-atm. rupture-disk assembly was used by the submitters. The checkers used a 1270-ml. stainless steel rocking autoclave fitted with a thermocouple well that extended into the reaction mixture and a stainless steel 5000-p.s.i. rupture disk. The agitation rate was 58 cycles per second. Attempts to use a magnetically stirred autoclave were unsuccessful. 

This constant was a function of particle size, agitation rate, and the surface properties of the particles, and its functional form suggested that the probability of coalescence was proportional to the surface area per unit volume of the... 

The coalescence constant required experimental correlation with the agitation rate and the surface free energies of the polymer particles. 

Fig. 6 shows a fed batch fermentation of sweet sorghum juice (SSJ) by Bacillus aryabhattai in 3 L fermentor under cultivating condition with agitation rate at 200 rpm, air rate of 1.5 1/min, at 30° C and feeding time at 18 and 24 hr during log phase of the culture. It was found that the cell could continuously produce both biomass and PHAs. Maximum cells were obtained at about 14.20 g/1 at 54 hr when PHAs content reached 4.84 g/1 after 66 hr (Tanamool et al., 2011). In addition, in Table 2, fed batch fermentation by A, latus was used for the production of PHAs (Yamane et al, 1996 Wang Lee, 1997). It could yield high productivity with the use of cheap carbon sources. 

Control rule-1. To achieve fermention of excellent quality, keep (a) the agitation rate in the first scaling episode (growth phase) > 37 units and (b) the duration of the first episode in the air flowrate < 25 h. 

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