Analysis of Regime Transitions and Flow Instabilities in Vertical Conveying of Coarse Particles Using Different Solids Feeding Systems

Abstract

The transition between dense and dilute flow in vertical conveying of Geldart D particles were investigated for risers of different diameters using a spouted bed as a solid feeding system. The transition and choking velocities were identified by combining analyses of pressure gradient versus air velocity diagrams, pressure fluctuation signals and voidage values. Experimental data were used to evaluate the effect of particle and riser diameters on the pressure gradient, mean mixture voidage, the regime transition and choking velocities. The transition velocity from dilute to dense phase could be identified, as well as the onset of the choking condition, which appeared as the air velocity was further reduced. Data obtained in the same experimental apparatus facility using a screw conveyor and a gravitational system as solid feeding devices have been used as a reference to be compared to those obtained using the spouted bed feeder.

Kinetics of drying the titanium dioxide paste in the vortex dryer

“…The analysis of literature [5,6] showed that at present the choice of optimal and expedient type of drying apparatus for fine disperse paste is a complex task of the system analysis of processes and apparatuses of chemical technology. Almost such a choice is made on the basis of a quantitative or qualitative assessment of the conformity of known types of apparatus to the properties of the paste.…”

Effect of operating conditions and particle properties on performance of vertical air-lift

“…Costa et al [20] investigated the effect of particle diameter on voidage (ε) in vertical pneumatic conveying of glass spheres (1.00, 1.70, and 2.85 mm) using different solids feeding systems (spouted bed feeder, screw feeder, and gravitational feeder). The voidage decreased with decreasing transport air velocity and increasing particle diameter for all solids feeding systems but the dependence was more significant for the spouted bed feeder compared with the other feeding devices.…”

“…As the transport air velocity increases, the voidage becomes less dependent on the transport air velocity and the particle diameter and the difference in pressure drop between glass beads and zirconium oxide decreases. Since the voidage decreases faster with decreasing transport air velocity for larger particles [20], the gravitational pressure drop would exceed the frictional pressure drop at a higher transport air velocity for zirconium oxide than for glass beads. However, further measurements of voidage, solids velocity, and solids friction factor are required to verify this hypothesis and clarify the effects of particle properties on the pressure drop.…”

“…Analysis of the pressure fluctuations has been used as a tool for identifying the flow regime in both horizontal and vertical pneumatic conveying [20][21][22]. Costa et al [20] and Grbavcic et al [22] used standard deviation of local fluid static pressure plotted as a function of gas superficial velocity to determine the transition between dilute phase and slug flow regime in vertical pneumatic conveying of coarse particles.…”

“…Costa et al [20] and Grbavcic et al [22] used standard deviation of local fluid static pressure plotted as a function of gas superficial velocity to determine the transition between dilute phase and slug flow regime in vertical pneumatic conveying of coarse particles. In both studies, the transitional points were recognized from the change in slope of a linear relationship between the standard deviation of pressure drop and the transport air velocity.…”