Numerical analysis of density wave in dense gas-solid flows in a vertical pipe

Abstract

Dense gas-solid flows in a vertical pipe are important relating to many industrial applications; for example, standpipe flows in circulating fluidized beds or vertical plug flows in pneumatic conveying systems. In such flows, particles do not disperse uniformly in the pipes but form clusters, or generate density waves. Experimental and numerical studies have been performed for small-scale standpipe flows, and a power law have been found in power spectra of the density waves. In the present work, we analyzed the density wave in an industrial-scale vertical pipe, and found the similar power law in it although the value of the exponent was different from that of the previous works for small-scale systems. We also performed a numerical simulation based on the discrete element method (DEM) coupled with CFD. The calculated value of the exponent agreed quantitatively with that in the corresponding experiment. The effect of the gas velocity on flow structure was also investigated.