Spouting Enhancement by Addition of Small Quantities of Liquid to Gas-Spouted Beds

Abstract

L'ajout d'eau liquide à des lits de particules de polystyrène de plus de 3 mm de diamètre améliore le jaillissement en causant une diminution de la vitesse de jaillissement minimale. Alors que le degré d'amélioration est du point de vue quantitatif comparable à ce que nous avons indiqué antérieurement pour des lits fl uidisés à larges particules hydrophobes légères, le mécanisme est différent. L'amélioration du jaillissement se produit parce que le liquide s'agglomère à l'interface jet-espace annulaire, formant un tube d'aspiration quasi imperméable effi cace, ce qui a pour effet d'accroître la vitesse du gaz en haut du jet.

Experimental study of hydrodynamics and thermal behavior of a pseudo‐2D spout‐fluidized bed with liquid injection

“…Continued liquid injection results in saturation of the liquid inside the bed with enhanced particle displacement only in the spout with particle lump formation, which can clearly be observed close to the bed wall in the annulus Figure l. This may be due to the reduced minimum fluidization and spouting velocity . Also, for the nonporous particles, the added liquid occupies a certain space between the particles, which causes an increase in the interstitial gas velocity.…”

“…4 and 5. Further, Nagahashi et al studied the effect of water addition in a half cylindrical spouted bed with and without draft tube for polystyrene particles ( d p = 6 mm) and compared the results with previous experiments performed on fluidized beds. Their results revealed that injection of liquid in a spouted bed leads to a lower minimum spouting velocity.…”

Analysis of pressure fluctuations during water evaporation in spouted bed

“…The spouting enhancement of polystyrene beads based on minimum spouting velocity lubricating with water addition was attributed (Nagahashi et al, 2006) to a lubricating effect of the liquid on the bed particle motion. Also, the authors refer to liquid congregation at spout-annulus interface, forming an effective nearly impermeable draft tube and increasing air velocity in the spout.…”

“…This regime was observed for several conditions and was called incoherent spouting. When liquid is fed onto the inert bodies, it causes a lubricating effect and according to Nagahashi et al (2006) liquid congregation at spout-annulus interface is observed, forming an effective nearly impermeable draft tube. This may cause the channelling of air in spout, eliminating the formation of bubbles.…”

“…Although it is well known that the hydrodynamics of SBs is markedly affected by the liquid presence (Schneider and Bridgewater, 1993;Reyes et al, 1998;Passos et al, 2000;Spitzner Neto et al, 2001, 2002Nagahashi et al, 2006), most researches did not consider the bed structure. Recently, many researchers have focused their attention to the use of pressure fluctuations signals, PFS, for gas-solid or gas-liquid-solid systems characterization (Fan et al, 1983;Bai et al, 1999).…”