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Flow regime liquid-solid mass transfer

Snider and Perona3 measured Ksas, the volumetric liquid-solid mass-transfer coefficient, for the case of hydrogenation of a-methyl styrene on 3-mm alumina spheres coated with palladium catalyst. The results were obtained in the bubble-flow regime. The measurements of Ks, the liquid-solid mass-transfer coefficient in a nonreacting system, were first reported by Mochizuki and Matsui.20 They... [Pg.261]

The modeling and design of a three-phase reactor requires the knowledge of several hydrodynamic (e.g., flow regime, pressure drop, holdups of various phases, etc.) and transport (e.g., degree of backmixing in each phase, gas-liquid, liquid-solid mass transfer, fluid-reactor wall heat transfer, etc.) parameters. During the past decade, extensive research efforts have been made in order to improve our know-how in these areas. Chapters 6 to 8 present a unified review of the reported studies on these aspects for a variety of fixed bed columns (i.e., co-current downflow, co-current upflow, and counter-current flow). Chapter 9 presents a similar survey for three-phase fluidized columns. [Pg.382]

A description of the flow phenomena in this type of process is very complicated and is outside the scope of this book (see reviews by Shah 1979, and Shah and Sharma, 1987). Phenomena that have been studied include the various flow regimes, liquid and gas hold-ups, pressure drop, the distribution of liquid and gas flows, effective solids wetting, axial mixing, etc.. However, it is important to remenber that for chemical reactor development one can measure, separately, the mass transfer and the integral performance of the three-phase system on a small scale, using the same solid particles that are going to be used on the larger scale. [Pg.120]

Model application in the pulsing-flow regime The mass transfer coefficient in the liquid-solid film is evaluated by means of the Dhai wadkar and Sylvester correlation (eq.3.433), and is found to be 0.45 s. Then, the several parameters of the model eq. (5.379) are shown in Table 5.18. [Pg.475]

The second section presents a review of studies concerning counter-currently and co-currently down-flow conditions in fixed bed gas-liquid-solid reactors operating at elevated pressures. The various consequences induced by the presence of elevated pressures are detailed for Trickle Bed Reactors (TBR). Hydrodynamic parameters including flow regimes, two-phase pressure drop and liquid hold-up are examined. The scarce mass transfer data such gas-liquid interfacial area, liquid-side and gas-side mass transfer coefficients are reported. [Pg.243]

The hydrodynamics control the mass transfer rate from gas to liquid and the same from liquid to the solid, often catalytic, particles. In concurrently operated columns not only the gas-continuous flow regime is used for operation as with countercurrent flow, but also the pulsing flow regime and the dispersed bubble flow regime (2). Many chemical reactors perform at the border be-... [Pg.393]

Hydraulic design aims at the realization of an intensive heat and mass transfer. For two-phase gas-liquid or gas-solid systems, the choice is between different regimes, such as dispersed bubbly flow, slug flow, churn-turbulent flow, dense-phase transport, dilute-phase transport, etc. [Pg.47]

The solids and the fluid have similar densities in liquid fluidization. The consequence is that most liquidized beds operate in the particulate regime where there is a smooth transition from incipient fluidization to pneumatic transport without bubble formation or slugging. They typically operate at near isothermal conditions and have good mass transfer between the liquid and the suspended solids. As a first approximation, the solid phase is well mixed and the liquid phase is in piston flow. There may also be a gas phase. Typical applications are in cell culture, including wastewater treatment. The specialized literature gives details. [Pg.421]

Conventional trickle bed reactors work under steady state conditions, whereby components in the. liquid, mostly via gas-to-liquid mass transfer are converted by the solid catalyst. Such a process is highly non-linear and thus it is questionable whether steady operation will provide an optimal conversion and selectivity in particular. Operation in the dynamic mode will provide an extra parameter to optimise the production. Trickle beds happen to show just naturally a dynamic flow regime in which gas/liquid discontinuities occur the pulsing flow regime. [Pg.439]

Consider two-dimensional steady-state mass transfer in the liquid phase external to a solid sphere at high Schmidt numbers. The particle, which contains mobile reactant A, dissolves into the passing fluid stream, where A undergoes nth-order irreversible homogeneous chemical reaction with another reactant in the liquid phase. The flow regime is laminar, and heat effects associated with the reaction are very weak. Boundary layer approximations are invoked to obtain a locally flat description of this problem. [Pg.273]

Answer For boundary layer mass transfer across solid-liquid interfaces, = I and y =. In the creeping flow regime, z = - This problem is analogous to one where the solid sphere is stationary and a hquid flows past the submerged object at low Reynolds numbers. [Pg.355]

I-power dependence of the dimensionless mass transfer coefficient on Re reveals fbat the flow regime is laminar. Turbulent mass transfer across high-shear no-slip interfaces also scales as Shaverage Sc, but the exponent of Re in this correlation is somewhere between 0.8 and 1. AU of these dimensionless scaling laws for interphase mass transfer are summarized in Table 12-1 for solid-liquid and gas-Uquid interfaces. [Pg.368]

Chemical reactors, particularly for continuous processes, are often custom designed to involve multiple phases (e.g., vapor, liquid, reacting solid, and solid catalyst), different geometries (e.g., stirred tanks, tubular flows, converging and diverging nozzles, spiral flows, and membrane transport), and various regimes of momentum, heat, and mass transfer (e.g., viscous flow, turbulent flow, conduction, radiation, di sion, and dispersion). There... [Pg.205]


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See also in sourсe #XX -- [ Pg.216 , Pg.217 , Pg.218 , Pg.219 , Pg.261 , Pg.262 , Pg.263 , Pg.264 , Pg.297 ]




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