Experimental Analysis of the Fluidization Process of Binary Mixtures of Solids

Abstract

The simultaneous treatment of dissimilar solids is encountered in a number of processes that exploit fluidization technology (granulation, combustion, pyrolysis, etc.), but a satisfactory description of multicomponent fluidization dynamics is far from being achieved even for the relatively simple case of binary fluidization.
This paper discusses the fluidization properties of two-component beds of solids differing either in particle density or diameter. It is shown that although the minimum fluidization velocity of the mixture can be calculated by fully theoretical equations, it has very little meaning if referred to a two-component particle system. Experiments on both kinds of mixtures demonstrate that the binary fluidization process occurs within a characteristic velocity range whose boundaries coincide with the “initial” and the “final fluidization velocity” of the particle mixture. Substitution of the conventional concept of u_mf by these parameters allows us to recognize that the fluidization dynamics of any binary mixture is determined by the initial arrangement of the fixed bed, as well as by the system composition and size or density ratio of its components.