Hide/Show Apps

Characterization of local flow behaviour in conical spouted beds

Yeniçeri, Ali
Conical spouted beds are used in various physical and chemical applications such as drying, coating, and pyrolysis of waste plastic and biomass owing to their effective feature of gas-solid contact. To design and operate these units in high efficiency, a complete understanding of the phenomena and detailed investigation of local flow structure are of paramount importance. In this study, the effects of bed design parameters (unit size, conical angle, spouting gas-inlet diameter) and operational conditions (particle density, axial position) on bed local flow structure were investigated in detail. Experiments were performed in small and large conical spouted beds by using light and heavy particles with varying density (2460 kg/m3 ≤ ρp ≤ 6050 kg/m3). To observe the effects on local flow structure, an optical probe system was used. Additionally, an empirical correlation was proposed to predict the solids hold-up at the spout center (r = 0) for light and heavy particles. The investigated parameters caused significant changes in spout region while the annulus region was found to be unaffected. The particle velocity decreased and solids hold-up and particle flux increased from the bed bottom to the bed surface. Using larger gas-inlet diameter decreased the particle flux in the spout. An increase in cone angle caused a major decrease in particle flux. Introducing fluidizing gas through the conical section to the system caused minimal effect on particle flux, resulting in only 8% increase in the spout region. Particle velocity and solids hold-up did not significantly change in presence of fluidizing gas.