Solids circulation in a spout‐fluid bed with draft tibe

Abstract

A 20 cm diameter semi-cylindrical spout-fluid bed with a draft tube has been used to study the effects of operating and geometric parameters on the solids circulation rates at ambient temperature. A new technique has been developed for measuring the solids fluxes with great accuracy. Solids circulation rate data have been found to be strongly influenced by both geometry and relative magnitude of spouting and auxiliary gas flowrates, as they in turn affect the flow of the gas-solid mixture inside the draft tube. The solids circulation rate was greatly enhanced when an auxiliary flow aerated the annular region and such enhancement has been found to be linearly dependent on the auxiliary flow contribution to the total gas flow and on the distance between the base of the draft tube and the inlet nozzle.On a utilisC un lit fluide a jaillissement semi-cylindrique de 20 cm de diarnktre muni d'un tube de circulation pour Ctudier les effets des parametres operatoires et geomitriques sur les vitesses de circulation des solides a la temperature arnbiante. Une nouvelle technique a Cte mise au point pour mesurer les flux de solides avec un grande exactitude. On a trouvi que les donnCes de vitesse de circulation des solides sont fortement influenctes a la fois par la geometrie et la grandeur relative du jaillissement et des debits gazeau auxiliaires, du fait que ceux-ci modifient leur tour I'Ccoulement du melange gaz-solides a I'interieur du tube de circulation. La vitesse de circulation des solides est largement amelioree lorsqu'un Ccouleinent auxiliaire &re la region annulaire et on a trouvC que cette amelioration est lineairement dependante de la contribution de I'ecoulement auxiliaire au debit gazeau total et de la distance entre la base du tube de circulation et de la tuyere d'entree.

Effect of the tube shape on gas and particle flow in spouted beds with a porous draft tube

“…Also, in this study particle velocity in annulus ( V PA ) was measured, and the solids circulation rate ( W S ) was calculated from the mass balance of particles in the annulus as shown in the following equation: V PA was determined by measurement of the average time for coloured tracer particles to descend the 50 mm section in the upper part of annulus region. Although the descending particle velocity in the annulus region has a radial distribution in the case of a conventional spouted bed without a draft tube (He et al, 1994; Tsuji et al, 1997; Olazar et al, 2001), this method is applicable roughly and taken for a spouted bed with a draft tube or a spout‐fluid bed with a draft tube unless the annulus region becomes fluidized (Berruti et al, 1988; Muir et al, 1990; Hadzismajlovic et al, 1992; Ji et al, 1998). According to Hadzismajlovic et al (1992), the particle velocity in the annulus is uniform except in the cone section.…”

Effects of Draft Tubes on Particle Velocity Profiles in Spouted Beds

“…Its H m becomes limited only by the energy of the gas stream entering the bottom of the draft tube [5,6]. Besides overcoming the bed height limitation, a draft tube spouted bed (DTSB) has several other advantages.…”

Minimum spouting velocity in a spout‐fluid bed with a draft tube

“…Comparing with conventional spouted bed with or without a draft tube, and spout‐fluid bed without a draft tube, there is relatively very limited information available on the hydrodynamic behaviour of DTSFB (Yang and Keairns, 1983; Berruti et al, 1988; Muir et al, 1990; Grbavcic et al, 1992; Xiao et al, 2002; Osorio‐Revilla et al, 2004). Minimum spouting velocity is one of the most important flow characteristics for proper design and operation of the spouted bed reactors.…”