Systems solid-liquid agitated

Nagata S, Yamaguchi J, Yabuta S, Harada M. (1960) Mass transfer in solid-liquid agitation systems. Soc. Chem. Eng. Jpn., 24 618-624. 

The pulp-water systems encountered in the agitation of paper stock represent a highly specialized case of solid-liquid agitation, discussed in a few papers (CIO, K5, 04), which will not be reviewed here. Lamont (L2) discusses the operation of pachuca tanks, used for ore-leaching operations, in which agitation results from air introduced at the tank bottom. 

G. Highly agitated systems solid particles, drops, and bubbles continuous phase coefficient [E] Use arithmetic concentration difference. Use when gravitational forces overcome by agitation. Up to 60% deviation. Correlation prediction is low (Ref. 118). (PA, ar.k) = power dissipated by agitator per unit volume liquid. [79][83]p.231 [91] p. 452... 

Mixing of fluids is necessary in many chemical processes. It may include mixing of liquid vith liquid, gas with liquid, or solids with liquid. Agitation of these fluid masses does not necessarily imply any significant amount of actual intimate and homogeneous distribution of the fluids or particles, and for this reason mixing requires a definition of degree and/or purpose to properly define the desired state of the system. 

Mass transfer between a liquid and suspended solids in mechanically agitated systems has been widely studied, and a number of important investigations will be referred to in Section V,D,2. 

Morris (M9) has recently reviewed a number of studies of mass transfer across the gas-liquid interface in mechanically agitated systems containing suspended solid particles. These studies [Hixon and Gaden (H7), Eckenfelder... 

Hixson, A. W. and Baum, S. J. Ind. Eng. Chem. 33 (1941) 478, 1433. Agitation mass transfer coefficients in liquid-solid agitated systems. Agitation heat and mass transfer coefficients in liquid-solid systems. 

Agitation for a desired level of solids suspension is based on an overall appearance of the solid-liquid system. Results of the empirical correlations have been summarized for most types of solids-suspension scale-up cases... 

Tao BY. Optimization via the simplex method. Chem Eng 1988 95(2) 85. Lewis E. Gates, Jerry R. Morton, Phillip L. Fondy. Selecting agitator system to suspend solids in liquid. Chem Eng 1976 144-150. 

Agitated vessels (liquid-solid systems) Below the off-bottom particle suspension state, the total solid-liquid interfacial area is not completely or efficiently utilized. Thus, the mass transfer coefficient strongly depends on the rotational speed below the critical rotational speed needed for complete suspension, and weakly depends on rotational speed above the critical value. With respect to solid-liquid reactions, the rate of the reaction increases only slowly for rotational speed above the critical value for two-phase systems where the sohd-liquid mass transfer controls the whole rate. When the reaction is the ratecontrolling step, the overall rate does not increase at all beyond this critical speed, i.e. when all the surface area is available to reaction. The same holds for gas-liquid-solid systems and the corresponding critical rotational speed. 

It is not known how the presence of solid particles affects the fluid dynamic regime in an agitated vessel hence, it is necessary to assume that solid-liquid systems behave similarly to one-liquid-phase systems as described in Section II. Obviously this assumption will be best for systems in which the solids are small, are not very different in density from the liquid, are present in low concentration, and do not affect the Newtonian characteristics of the liquid. 

In connection with solid-liquid systems agitated so as to achieve interphase mass transfer or heterogeneous chemical reaction it may be noted that various workers have begun to consider the combined fluid dynamic, mass-transfer, and chemical kinetic problem in which a fluid moves past a solid with which it reacts chemically. The paper by Acrivos and Chambr6 (Al) is an example of this approach. 

Additional work on the suspension of solid particles in agitated systems has been reported by Oyama and Endoh (013), on suspension of sands and resin particles, in baffled vessels 5.5, 6.7, and 10.8 in. in diameter. These authors used a 3.6-in. vaned disk, and 2.6- and 3.6-in. flat-blade turbines. A light beam passed through the vessel onto a photoelectric tube was used to monitor the particle concentration in a horizontal plane at a height about of the total liquid height. At low speeds the particles tended to congregate near the vessel bottom. As the... 

Different values of the constant and exponent r were used for different system geometries and operating conditions. Thus, for the turbine agitators at a Reynolds number less than 7400, was 0.00058 and r was 1.4. For the turbine agitators at a Reynolds number above 7400, was 0.62 and r was 0.62. For the propellers, over a range of Reynolds numbers from 3300 to 330,000, was 0.0043, and r was 1.0. In every case, the Schmidt number exponent s was 0.5. Although these equations fit the data fairly well, there is a scatter of the individual points. Hence, for any particular solid-liquid combination at constant temperature in a... 

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