In stirred tank reactors

Baldyga, J. and Bourne, J.R., 1992. Interactions between mixing on various scales in stirred tank reactors. Chemical Engineering Science, 47, 1839-1848. 

Bourne, J.R. and Dell Ava, P., 1987. Micro- and macromixing in stirred tank reactors of different sizes. Chemical Engineering Research and Design, 65, 180-186. 

Bourne, J.R. and Yu, S., 1994. Investigation of micromixing in stirred tank reactors using parallel reactions. Industrial and Engineering Chemistry Research, 33, 41-55. 

Kinetics c/c0 in piston flow reactor Si, Sc o c/c0 in stirred tank reactor St,... 

This chapter develops the techniques needed to analyze multiple and complex reactions in stirred tank reactors. Physical properties may be variable. Also treated is the common industrial practice of using reactor combinations, such as a stirred tank in series with a tubular reactor, to accomplish the overall reaction. 

This set of first-order ODEs is easier to solve than the algebraic equations where all the time derivatives are zero. The initial conditions are that a ut = no, bout = bo,... at t = 0. The long-time solution to these ODEs will satisfy Equations (4.1) provided that a steady-state solution exists and is accessible from the assumed initial conditions. There may be no steady state. Recall the chemical oscillators of Chapter 2. Stirred tank reactors can also exhibit oscillations or more complex behavior known as chaos. It is also possible that the reactor has multiple steady states, some of which are unstable. Multiple steady states are fairly common in stirred tank reactors when the reaction exotherm is large. The method of false transients will go to a steady state that is stable but may not be desirable. Stirred tank reactors sometimes have one steady state where there is no reaction and another steady state where the reaction runs away. Think of the reaction A B —> C. The stable steady states may give all A or all C, and a control system is needed to stabilize operation at a middle steady state that gives reasonable amounts of B. This situation arises mainly in nonisothermal systems and is discussed in Chapter 5. 

Andersson, B. (2003) Important factors in bubble coalescence modeling in stirred tank reactors. 6th International Conference on Gas liquid and Gas-Liquid -Solid Reactor Engineering, 2003, Vancouver. 

The main part of the report describes the results of systematic investigations into the hydrodynamic stress on particles in stirred tanks, reactors with dominating boundary-layer flow, shake flasks, viscosimeters, bubble columns and gas-operated loop reactors. These results for model and biological particle systems permit fundamental conclusions on particle stress and the dimensions and selection of suitable bioreactors according to the criterion of particle stress. 

Shear Sensitivity Studies in Stirred Tank Reactor Configurations. . 163... 

Influence of the mode of operation on process performance. The mode of operation of stirred-tank reactors can also significantly affect reactor performance. The history of concentrations will be changed by the time policy of reactant(s) addition to the reaction mixture. In view of our very limited possibility of controlling of temperature in stirred-tank reactors, the temperature-time dependencies for different policies of dosing will also be different. For example, the result of nitration depends upon the method of addition of nitric acid to aromatics, and the choice which phase is dispersed and which is continuous. Consequently, if the reaction is concentration- or temperature-sensitive the result will be dependent on the mode of operation (see Example 5.3.1.5). 

STABLE OPERATING CONDITIONS IN STIRRED TANK REACTORS... 

Stable Operating Conditions in Stirred Tank Reactors... 

Incubation temperature and medium pH are also important regarding proteolytic activity of baculovirus infected insect cell cultures. Cruz et al. [25] have shown that the highest proteolytic activity was obtained at the normal culture conditions, 27 °C and pH 6.5. This could then be considered a drawback when the production of protease sensitive particles Hke HIV-CLPs and HIV-VLPs is envisaged [5]. The pH of Sf9 cells has been reported to reach a minimum of 5.9 in serum-free media under uncontrolled pH conditions in stirred tank reactors... 

Baculovirus binding to insect cells is receptor-mediated [60]. From the work of Dee and Shuler it seems that the post-attachment steps occur much faster than attachment and thus the limiting step is the rate of attachment [61]. Another interesting result from the Dee and Shuler report that could have a great impact on bioreaction operational parameter specification is the observation that even in attached cultures, i.e. with baculovirus transport limited by diffusion, the rate of the diffusion of the baculovirus is 10-fold higher than the rate of attachment. This suggests that the overall rate of infection is, in suspension systems fike in stirred tank reactors, independent... 

Bulk Polymerization. Monomer and polymer (with traces of initiator) are the only constituents in bulk polymerizations. Obviously, the monomer must be soluble in the polymer for this type of process to effectively proceed. Bulk polymerization, also called mass or block polymerization, can occur in stirred-tank reactors, or can be unstirred, in which instance it is called quiescent bulk polymerization. The primary difficulty with bulk polymerizations is that as the polymerization proceeds and more polymer is formed, the viscosity increases, thermal conductivity decreases, and heat removal becomes difficult. 

Correlations are available for mixing times in stirred-tank reactors with several types of stirrers. One of these, for the standard Rushton turbine with baffles [13], is shown in Figure 7.9, in which the product of the stirrer speed N (s ) and the mixing time t (s) is plotted against the Reynolds number on log-log coordinates. For (Re) above approximately 5000, the product N t (-) approaches a constant value of about 30. 

On occasion, solid particles - such as catalyst particles, immobilized enzymes, or even solid reactant particles - must be suspended in liquid in stirred-tank reactors. In such cases, it becomes necessary to estimate the dimension and speed of the stirrer required for suspending solid particles. The following empirical equation [15] gives the minimum critical stirrer speed (s ) to suspend the particles. 

Many parameters affect the mass transfer between two phases. As we discussed above, the concentration gradient between the two phases is the driving force for the transfer and this, together with the over-all mass transfer coefficient, determines the mass transfer rate. The influence of process parameters (e. g. flow rates, energy input) and physical parameters (e. g. density, viscosity, surface tension) as well as reactor geometry are summed up in the mass transfer coefficient. The important parameters for Kta in stirred tank reactors are ... 

Ozonation experiments to determine kLa from such an instantaneous reaction should preferably be conducted in a so-called agitated cell in which both phases are perfectly mixed and the transfer area is determined by the geometry of the constructed interface between the gas and the liquid in the system (see Figure B 2-5 Levenspiel and Godfrey, 1974). The method has also been used in stirred tank reactors (Sotelo et al., 1990 Sotelo et al. 1991 Beltran and Gonzales 1991), but these reactors have two drawbacks ... 

Plazl, I., Leskovsek, S. and Koloini, T., Hydrolysis of sucrose by conventional and microwave-heating in stirred-tank reactor, Chem. Eng. J. Biochem. Eng. J., 1995, 59, 253. 

The effect of reaction conditions (temperature, pressure, H2 flow, C02 and/or propane flow, LHSV) and catalyst design on reaction rates and selectivites were determined. Comparative studies were performed either continuously with precious-metal fixed-bed catalysts in a trickle-bed reactor, or batchwise in stirred-tank reactors with supported nickel or precious metal on activated carbon catalysts. Reaction products were analyzed by capillary gas chromatography with regard to product composition, by titration to determine iodine and acid value, and by elemental analysis. 

F. (1988) Calculation of the maximum temperature in stirred tank reactors... 

A reaction A——>P is to be performed in a PFR. The reaction follows first-order kinetics, and at 50 °C in the batch mode, the conversion reaches 99% in 60 seconds. Pure plug flow behavior is assumed. The flow velocity should be 1 m s"1 and the overall heat transfer coefficient 1000Wm 2 K"1. (Why is it higher than in stirred tank reactors ). The maximum temperature difference with the cooling system is 50 K. 

Villerrmaux, J., Falk, L. and Fournier, M. C. (1990). Potentialuse of a new parallel reaction system to characterize micromixing in stirred tank reactors. 

S3] A process for the oligomerization of ethylene for the production of linear a-olefins had to be developed in stirred tank reactor assuming isothermal conditions and was executed in the kinetic regime. The latter was assured by increasing the rotational speed of the impeller until the rate of reaction did not increase further. The autoclave reactor was heated by an external blanket and supplied with cooling water circulation through an internal coil. 

Stirred tanks are typically used for the thermochemical pretreatment. To simulate flow of corn stover slurries in stirred tanks, the rheologic properties of these suspensions must be known. The corn stover slurries in stirred tank reactors typically range from 10 to 40% solids (3). 

Various combinations of bioreactors and operation mode have been used for the production of mAbs in several systems of expression, as shown in Chapter 9. All cells utilized for the production of mAbs grow in suspension. Those that did not initially have this capacity have been adapted (as is the case for CHO and BHK) (Butler, 2005). This results in a large number of options for production systems. Cells with this characteristic are easily cultivated in stirred-tank reactors, which have been scaled up to a volume of 10 000 L (Chu and Robinson, 2001 Kretzmer, 2002). This kind of bioreactor provides excellent homogeneity, facility for the implementation of control techniques, and the principles of scaling up are relatively well known. Other kinds of bioreactors for the production of mAbs are also available, such as air-lift, with volumes up to 1000 L, and also fixed-bed bioreactors (Moro et al., 1994 Irving et al., 1996 Kretzmer, 2002). 

Few comprehensive studies have appeared concerning the influence of solids on k a in stirred tank reactors. Oguz et al. [87] measured k a in various slurries in a baffled 14.5 cm diameter stirred-tank reactor. Water and three organic liquids ( -butanol, 1-tetradecene and 1,2,4-trimcthylbenzcnc) were used as liquid phases. The particles applied varied in density from 2070 to 4720 kg m 3 and average particle sizes from 80 pm to below 1 pm. The observed cflccts of the particles on k a appear at first sight to be confusingly different for different slurry systems (sec Fig. 9). However, if the increase in apparent slurry viscosity due to the presence... 

Figure 3.2 Three typical stirrers used in stirred tank reactors. Many other types are known.

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