移動層における軸方向粒子混合について

抄録

It is believed to be very important to know the behaviours of particles in a moving bed, when designing an apparatus in which a moving bed is used; particulary so when a severe requirement is made of the apparatus as to the particle holding time.
The authors carried out observations and measurements with regard to the mixing degree of particles in a moving bed, by using tracer particles.
The apparatus used in the experiments is shown in Figs. 1 and 2. Solid particles used were steel balls, silica alumina balls and Soma sand, whose properties are listed in Tables 1 and 2.
Experimental methods employed were as follows. Tracer particles were added on to the top of the bed, and then the concentration of the tracer particles was measured at the bottom of the bed. Concentration curves of tracer particles at the bottom were as shown in Figs. 36, and coefficients of axial mixing of particles were calculated from these curves and Eq. (7).
As it was observed that there was a difference between the velocity of the particles lying in monolayer on the tube wall and that of the particles in the bed core (particles in bed except for the particles in monolayer on the tube wall), the experimental results shown in Table 3 may be summarized as follows:-
1. The concept of the axial mixing coefficient of solid particles, E_sx, is introduced on the assumption that the solid particles in bed may be regarded as to be in a homogenous phase. The axial Peclet number of particles in the bed core, (N_Pe=D_pu_c/E_sx), in a moving bed approaches 150 or so for Froude number, (N_Fr=u_c²/gD_p), 10^-310^-5. The mixing degree of particles calculated by N_Pe=150 agrees well with the experimentally observed data, as shown in Fig. 11.
2. The values of u_c/u_m and u_w/u_m are 1.1 and 0.85, respectively, and are independent of u_m for D_p/D_T =0.110.06, as shown in Fig. 9, where u_w is the velocity of monolayer particles on the tube wall, u_c is that of particles in the bed core and u_m is average velocity of particles in bed.