(577g) Segregation of Flotsam Rich Binary Mixture of Solids in Continuous Liquid Fluidized Beds

Authors: 
Sai, P., Indian Institute of Technology Madras

The industrial applications of fluidization technology (coal gasification, power granulation etc.) involve solid mixture of particles of different size and/or density. This technology has different applications with different purposes. It enhances the reaction rate and improves the heat and mass transfer rates when used in mixing process industry. It can also be used in the mineral process industry to separate the minerals based on the physical properties of the solids. Among different classifiers, fluidized beds provide stable operation and sharp separation. Now researchers are more focused on the understanding of segregation phenomena by liquid fluidization of binary mixture of particles and to improve the efficiency of segregation of particles. In a solid-liquid fluidized bed of different sizes/or densities particles, the coarser particles tend to sink down and fine particles entrained out the column. The particle settles down to bottom called as jetsam the entrained particles called as flotsam. The difference in size/density of individual particles results in segregation and concentration of desired components.

The present study focuses on the experiments on segregation of binary mixture of solids in continuous liquid fluidized beds with flotsam rich binary mixture of solids with one size ratio and same density. The bed was operated between transport velocities of the individual particles. The variables include solids feed rate, feed pipe location and liquid superficial velocity. The measured variables include the entrainment rate of solids, discharge rate of solids and purity of the products. The fluidization behavior was observed through pressure drop measurement. With increasing the liquid velocity at different solid feed rates, the pressure drop profiles reach a maximum and goes to a minimum and then levels off. The entrainment rate of solids increases and discharge rate of solids decreases with increasing the liquid velocity. When the liquid velocity is near the transport velocity of coarser particles, the entrainment rate of solids is high and discharge rate of solids is zero as the particle to particle interaction is less and the holdup is minimum. When the liquid velocity is near the transport velocity of the fine particles, the purity of the top product is high and the bottom product is low. At higher liquid velocities, all the fine particles entrain out of the column and the purity of top product decreases and the purity of the bottom product increases.