Fluidization of Wet Brown Coal Particles with Wide Particle Size Distribution

Abstract

Though the amount of brown coal resources in the world is abundant, and its moisture content is often high (more than 30%, wet basis). Thus, fluidized bed drying systems, using superheated steam for fluidizing gas, has been developed as a large capacity and low energy consumption drying technology. Brown coal particles used in fluidized beds are classified into B particles according to Geldart’s classification. However, particle properties, size, density and cohesiveness change with moisture content. Therefore, it is important to know the influence of moisture content on its fluidization characteristics. In this work, experiments were carried out to evaluate the effect of moisture content and particle size distribution on fluidization characteristics by using a fluidized bed cold model. For fluidization characteristics, minimum fluidization velocity, minimum complete fluidization velocity and minimum complete mixing velocity were measured. As a result, a quantitative relationship between the particle size distribution and fluidization characteristics was obtained. Also, a quantitative relationship between moisture content and fluidization characteristics was obtained by introducing an angle of repose as an index of cohesiveness.