粒子濡れ性に起因する乾式比重分離効率低下の改善

抄録

　It is generally known that the fluidized bed has liquid-like properties such as apparent density and viscosity. When objects are immersed in a fluidized bed, objects of smaller density than apparent density of the fluidized bed float, while those of larger density sink into the fluidized bed. Different density objects can be separated at the top and bottom of the fluidized bed by controlling the apparent density between the object densities. However, when the particles are fluidized by wet air, it will be difficult to make the particles to fluidize stably because of particles aggregation. In this case, FBMS (fluidized bed medium separation) efficiency will be also reduced. In this study, the particles of different wettability are employed to investigate the fluidization stability against the relative humidity of air. The fluidization of hydrophilic particles becomes unstable and the minimum fluidization velocity becomes large with increasing the relative humidity. This would be because particle aggregation caused by high humidity. On the other hand, in the case of hydrophobic particles, the fluidization is stable and the minimum fluidization velocity keeps constant even if the relative humidity is increased. The apparent density of fluidized bed is evaluated by floating and sinking of different density spheres and by measuring the fluidized bed height at different humidity. The apparent density keeps constant against the relative humidity in the case of hydrophobic particles, although it decreases with increasing the relative humidity in the case of hydrophilic particles. By employing hydrophobic particles, the apparent density is not affected by the relative humidity and it means that the FBMS can be carried out at high humidity.