Numerical investigations of a pseudo-2D spout fluidized bed with draft plates using a scaled discrete particle model

Abstract

Spout fluidized beds are often utilized for the gas–solid operations involving physical and/or chemical transformations such as drying, coating, granulation, combustion, gasification, etc. This is because these beds combine advantages of both spouted and fluidized beds. Following the spout fluidized bed development, several geometrical modifications have been proposed to optimize the bed performance. One of the modifications includes a draft tube insertion inside the bed, which results in improved performance by providing a restriction on particle cross flow. Moreover, the draft tube insertion leads to a stable spouting at lower flow rates, due to the reduced inlet gas bypassing (from spout to the annulus).In this work, a discrete particle model (DPM) with a sub-grid scale (SGS) turbulence model was used to simulate the bed dynamics and analyze the effects of the draft plates and particles physical properties by considering two regimes namely, the spouting-with-aeration and fluidized bed-spouting-with-aeration (dispersed spout), which are of interest from an industrial point of view. The obtained results were compared with our experimental data (Sutkar et al., 2013b) from particle image velocimetry (PIV) and digital image analysis (DIA). Furthermore, an alternative simulation approach has been used to simulate dynamics of the industrial scale gas–solid contactors consisting very large particles with reduced total computational time by changing the physical properties of the particles to maintain constant Archimedes and Reynolds numbers. The obtained results were compared with the experimental data, as well as with simulation data obtained with the original physical properties.