Mass transfer reactors

The use of immobilized cell reactors have shown improved biocatalyst stability, however, the specific rates of desulfurization have been much lower than for suspended cell (stirred) reactors. Mass transfer limitations have been significant resulting in lower rates. Thus, the activity is sacrificed to achieve stability. Further work in this area and improved immobilization matrices can help improve the activity along with the stability. 

Negligible and medium interaction regimes. Experiments were carried out with an aqueous 2.0 M DIPA solution at 25 °C in a stirred-cell reactor (see ref. [1]) and a 0.010 m diameter wetted wall column (used only in negligible interaction regime, see ref. [4,5]). Gas and liquid were continuously fed to the reactors mass transfer rates were obtained from gas-phase analyses except for CO2 in the wetted wall column where due to low C02 gas-phase conversion, a liquid-phase analysis had to be used [5]. In the negligible interaction regime some 27 experiments were carried out in both reactors. The selectivity factors were calculated from the measured H2S and CO2 mole fluxes and are plotted versus k... 

U. Ullah, S.P. Waldrum, C.J. Bennett and T. Truex, Monolithic reactors Mass transfer measure-ments under reacting condition.s, Chem. Eng. Sci. 47 2413 (1992). 

Ullah U., S.P. Waldram, C.J. Bemiett, and T. Tmex Monolithic reactors mass transfer measurements mider reacting conditions. Chem. Eng. Sci., 47, 9, 1992. 

S.P. Waldram, U. Ullah, C.J. Bennet, T. Tmex, Monolithic Reactors Mass Transfer Measurements Under Reacting Conditions, Chem.Eng.Sci.,47,No9-ll, 2431-2418, (1992). 

Reactor Elementary zones of reactor Mass transfer, heat exchange, diffusion, etc. 

These reactors are simple to construct, provide good control of solids retention time, and consume less power than other reactors. Mass transfer correlations of the usual fonn, Sh as a function of Re and Sc, are available (e.g Machon and Linek, 1974). In a more recent study, Fr has been used as a corresponding... 

Moo-Young, M., and Blanch, H.W. (1981), Design of biochemical reactors mass transfer criteria for simple and complex systems, Advances in Biochemical Engineering, 19 1-69. 

Van Landeg m.h. " TluTtiphase Reactors Mass transfer and modeling". Chem.Engng.Sci. 35 (1980) 1912-1942. 

Ullah U, Waldram SP, Bennett CJ, Truex T. Monolithic reactors Mass transfer measurements under reacting conditions. Chemical Engineering Science 1992 47 2413-2418. 

THE PROBLEM A batch laboratory reactor with an electrolyte volume of 700 cm and an electrode area of 30 cm is used to deposit a divalent metal from an aqueous solution in a potentiostatic mode. Initial concentration of the metal is O.lkmol/m. The reactor mass transfer coefficient has been measured as 3.3 x 10" m/s. Hydrogen evolution occurs as a parallel reaction according to the equation % = H p [ — ], where kn = 1.30 X 10" A/m and = 12 If the metal deposition is operated at its limiting current density at an electrode potential of —0.9 V (SCE), determine how conversion, total current density, and current efficiency vary with time, in a potentiostatic mode. What will be the current efficiency at the final... 

CFD has become a standard tool for analyzing flow patterns in various situations related to chemical engineering. In many cases related to multiphase reactors, mass transfer limits overall chemical reaction. In these cases the accurate calculation of local mass transfer rates is of utmost importance. This is best done with the population balance approach, where local properties are used to model bubble or droplet breakage and coalescence phenomena. It has been proven that these rigorous models along with other multiphase and chemistry related models can be implemented in the CFD code, and solved simultaneously with the fluid flows. 

Mechanically agitated slurry reactors Mass transfer... 

Types of loop reactors Mass transfer Trickle bed reactors (TBRs)... 

Bubbles play an important role in many industrial and natural systems. A few examples include chemical reactors, mass transfer operations, froth flotation, and aeration systems. In some situations, buoyancy is the main cause of bubble motion. However, in low-gravity environments, more subtle effects such as surface tension gradients may be the primary mechanism for bubble motion. In turbulent flows, bubbles tend to follow the motion of the surrounding liquid. These examples may give some impression of the scope of the subject that we will attempt to address in this chapter. 

In common multiphase reactors mass transfer resistances frequently lead to a decrease of the effective reaction rate compared to the chemical (intrinsic) rate. In addition, many multiphase reactions like oxidations or hydrogenations are highly exothermic. Consequently, heat removal may also be important. 

Radial Dispersion of Mass In contrast to axial dispersion in a tubular fixed bed reactor, mass transfer in the radial direction should be maximized to prevent... 

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