Agitated cell reactor

The agitated cell reactor consists of two chambers, one for the liquid phase and another for the gas-phase, which can both be independently mixed by two mixers. In this reactor the mass-transfer area can be varied independently of the gas flow rate by installing various porous plates with a defined number of holes, i. e. a defined contact area gas-liquid, between the two chambers. The value of kL can then be determined from the measurement of kLa. 

Agitated cell reactor or Agitated tube reactor (ACR or ATR)... 

AM Technology [33] is offering three types of equipment, namely agitated cell reactor, agitated tubular reactor (ATR) and variable-channel reactor (VCR). These may be viewed as a number of stirred tank reactors connected in series. 

Figure 5.12 Agitated cell reactor. Source Reprinted from Ref [35] 2012 with permission from The Institution of Chemical Engineers.

For slower reactions a different kind of constant power reactor is used, known as the agitated cell reactor. The agitated cell reactor (ACR) shown in Figure 5.42 is a form of constant power reactor where the product flows through a series of agitated cells. The concept adapts a well-rooted meso-scaled technique of the continuously stirred tank reactor to the constant power notion for greater increase in process control and stability. 

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 ... 

For example, Beltran and Alvarez (1996) successfully applied a semi-batch agitated cell for the determination of kL k,a, and the rate constants of synthetic dyes, which react very fast with molecular ozone (direct reaction, kD = 5 105 to 1 108 L mol-1 s l). In conventional stirred tank reactors operated in the semi-batch mode the mass transfer coefficient for ozone kLa(03) was determined from an instantaneous reaction of ozone and 4-nitrophenol (Beltran et al., 1992 a) as well as ozone and resorchinol (l,3-c//hydroxybenzene) or phloroglucinol... 

Immobilized Cell Reactors An immobilization technique consists of attaching the cells to a gel matrix. A high cell concentration can be obtained. Agitation, cell separation and recycling are not needed. Immobilized cells can be used in fixed-bed and fluidized-bed reactors. The substrate solution flows continuously through the reactor, while the immobilized cells convert the sugar to ethanol. A maximum ethanol productivity of 53.8g/l was achieved at a dilution rate of 4.6 h 1 and an initial glucose concentration of 127 g/1. 

Manufacture is either by reaction of molten sodium with methyl alcohol or by the reaction of methyl alcohol with sodium amalgam obtained from the electrolysis of brine in a Castner mercury cell (78). Both these methods produce a solution of sodium methylate in methanol and the product is offered in two forms a 30% solution in methanol, and a soHd, which is a dry, free-flowing white powder obtained by evaporating the methanol. The direct production of dry sodium methylate has been carried out by the introduction of methanol vapors to molten sodium in a heavy duty agitating reactor. The sohd is supphed in polyethylene bags contained in airtight dmms filled in a nitrogen atmosphere. 

For many laboratoiy studies, a suitable reactor is a cell with independent agitation of each phase and an undisturbed interface of known area, like the item shown in Fig. 23-29d, Whether a rate process is controlled by a mass-transfer rate or a chemical reaction rate sometimes can be identified by simple parameters. When agitation is sufficient to produce a homogeneous dispersion and the rate varies with further increases of agitation, mass-transfer rates are likely to be significant. The effect of change in temperature is a major criterion-, a rise of 10°C (18°F) normally raises the rate of a chemical reaction by a factor of 2 to 3, but the mass-transfer rate by much less. There may be instances, however, where the combined effect on chemical equilibrium, diffusivity, viscosity, and surface tension also may give a comparable enhancement. 

Reactions of cell growth or those using immobilized enzymes are instances of gas-liquid-solid reactions. In principle, accordingly, any of the types of reactors described in Section 8.3 could be employed as fermentors. Mostly, however, mechanically agitated tanks are the type adopted. Aeration supplies additional agitation as well as metabolic need, and moreover sweeps away C02 and noxious byproducts. 

The high shear stress around an agitation impeller is not acceptable for cell cultures or other sensitive materials in stirred (bio) reactors (Kato et. al., 2003 Michell et al., 1999). In these cases in which the solid phase is sensitive to high shear stress, shaking vessels can be used. The main types are the reciprocally and rotational shaking vessels. For these cases, see Kato et al. (2003). 

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