CFD–DEM study of gas–solid flow characteristics in a fluidized bed with different diameter of coarse particles

Abstract

Fluidized bed is the main reactor for the heating and gasification of coal, biomass, and other solid fuels. The diameter, density, and shape of the particles significantly affects the gas–solid​ two-phase flow process. Based on the numerical method combining computational fluid dynamics and discrete element method (CFD–DEM), this paper mainly performs numerical simulation on the gas–solid two-phase flow process of coarse particles under different inlet mass flow rates with diameters of 2.5 mm, 3.0 mm, and 3.5 mm, respectively. The high-speed photographic experiments were carried out to validate the numerical results successfully. The effects of particle diameter on bubble morphology have been compared, such as bed height and initial bed mass change rate. The maximum value of the bed height reached gradually decreases as the particle diameter increases. Two typical C-shaped bubbles were found above the large bubbles during the fluidization processes, which further improve the uniformity of mixing. Slugging appears as the width of the bubbles in the fluidized bed is close to the width of the fluidized bed, which has great effects on the mass and heat transfer. This study could serve as reference for further optimal design of fluidized bed, especially for biomass or chemical looping combustion application with coarse particles.

Keywords

• CFD–DEM
• Fluidized bed
• Gas–solid two-phase flow
• Geldart Group D particles