The liquids used were 4 in kind, i.e., water, kerosene, turbine-oil and transformer-oil, whose properties are shown in Table 1.
The experimental apparatus employed is shown in Fig. 2. The standard gas-pipes of the sizes, 1 1/2'', 1 1/4'', 1'', and 3/4'' were used for the overflow pipes. Uchida et al. had reported the results of their researches on the same subject, but their conclusion was not always in accord with our experimental results as shown in Fig. 1. Therefore we studied how the coefficient of discharge, C, in Eq. (2) would vary with the change in the head, the liquid properties and the size of the overflow pipes, in order to obtain a more general equation for C.
The overflow was found to become unsteady at the head, when h=D/3; and in the case of the quiet steady-overflow when (h/D)<1/3, the value of C varied from 0.2 to 0.83.
Experimentally we obtained Fig. 3, from which we determined
C=Q/2/3·bh·√2gh=(h/b)-0.97(D²pq/σ)^-0.68/0.0072(μ/μ_w)^0.08(σ_w/σ)^0.61+1.06{(h/b)-0.97(D²pq/σ)^-0.68} (7),
as the general equation for C.
The actual volume rate of discharge. Q_Exp., showed good agreement with the volume rate calculated from Eq. (7), Q_Calc., as shown in Fig. 10.

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The purpose of this study is to obtain data available for the design of a continuous fluidized-bed-type leaching equipment.
Concerning the leaching of the extractable material from the sphere of a solid particle, theoretical analyses have been developed, taking into consideration the diffusion in the solid particle as well as in the film of the fluid.
When the concentration of solution contained in a solid particle is uniform, or when the leaching interface can be assumed to exist in the solid particle, the following equations will be applicable, -Eqs. (4) and (10) for the distribution of the concentration of solute in solid phase, Eqs. (7) and (16) for the rate of solute leaving the surface of the solid particle due to diffusion, Eqs. (5) and (14) for the mass of extractable material remaining unextracted, Eqs. (6) and (15) for the nonleached fraction, and Eqs. (8) and (17) for the concentration of solute on the surface of the particle.
Based on the diffusion in the film of fluid and in the solid phase, and on the assumption that solid particles are completely mixed in the bed, theoretical equations representing the longitudinal distribution of the concentration of solute in the leaching operation by a single-stage fluidized bed have been derived, -e. g., Eqs. (19)-(23) and Eq. (27).
Experiments on the dissolution of solid particles in fluidized bed have been performed in order to compare the results with those of the theoretical curves obtained from Eq. (19).
In Figs. 9 and 10 are illustrated graphical solutions for determining the number of stages necessary for a multistage-fluidized-bed-type extractor, when the diffusion in the film of the fluid is controlling.

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In our previous paper, the mechanism of heat transfer to solid particles in the stirred bed was investigated, assuming that the effective thermal conductivity was constant in the radial direction of the bed and there existed thermal resistance at the wall of the tank. However, when the ratio (R_i/R₀) became larger, the assumption that the effective thermal conductivity was constant in the radial direction did not hold. To explain the phenomenon, the bed was divided into two sections, viz., Section-I where the impeller blades passed through, and Section-II where they did not. (See Fig. 3.) The solid particles in Section-I were mixed much more thoroughly by the impeller than those in Section-II so that the effective thermal conductivity in Section-I might be supposed to be practically infinite. On this assumption Eq. (5) expressing the temperature in the bed was obtained.
The experiments were carried out in the apparatus shown in Fig. 1. Three kinds of impellers used are also shown in Fig. 2. The material used was sand ranging in size from 20 to 150 mesh.
The experimental results were analyzed by Eq. (10) or (11) and the effective thermal conductivities in Section-II were obtained. These were expressed by Eq. (18) where k ⁰ is the thermal conductivity in the quiescent bed and (k )_t is the themal conductivity caused by lateral mixing of solid particles. The value (k )_t could be expressed by Eqs. (20) and (21). The temperature profile of the bed was calculated by Eq. (5) and was found to agree well with the observed temperature profile of the bed. (See Fig. 6.)

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[in Japanese]

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