粉体混合機内の粒子循環時間におよぼす粒径の影響 粒径差による分離現象と循環時間比

Abstract

To investigate the characteristics of the flow and the mixing and/or demixing of particles in the powder mixer, the relationship between the circulating time and the particle size for the cases of various combinations of binary components has been measured by using an optical method. A mechanical agitation type of mixer with a vibrating vessel has been employed, and six pairs of optical fiber made of plastics were inserted in the particle bed as a detector of the tracer concentration. The particle bed in the vessel during the mixing operation showed a fluid-like behavior in the limited region of the operating conditions, both for the impeller speed and frequency of vessel vibration. The larger particles in the smaller particle bed showed a smaller circulating time. On the other hand, the circulating time for the smaller particles in the larger particle bed showed the opposite tendency. A new parameter Θ defined as the ratio of the circulating time θ(NR) for the tracer particles at impeller speed NR and θO(NR) for the bulk particles at the same operating conditions has been introduced as an index of the segregating or demixing tendencies due to the difference in the particle size. The effects of the size ratio of the tracer and bulk particles, dPB/dPA and the size of bulk particles bed on the parameter Θ have been examined.