The Relationship Between Fluidization Velocity and Segregation in Two-Component Fluidized Beds: A Preliminary Analysis

Experiments are presented that provide the initial and final fluidization velocity of binary mixtures at varying composition. Introducing just one parameter to account for their segregation level, the theoretical equations of the two characteristic velocities are derived. These equations are then employed to predict the concentration profile obtained by slowly defluidizing the bed down to the fixed stat

TOWARDS A THEORETICAL MODEL OF SEGREGATING FLUIDIZATION OF TWO-SOLID BEDS

Fluidization of beds of two dissimilar solids is modelled by reworking the fundamental equations of fluidization. The approach followed illustrates the relationship between bed suspension and component segregation, as determined by differences in solid density and size. The need for empirical parameters is drastically reduced so that a unique representation of all types of mixture behaviour seems possible

BUBBLE-FREE FLUIDIZATION OF PARTICLES IN THE VOIDS OF A PACKING OF COARSE SPHERES

Confining a bed of relatively fine particles in a packing of coarse spheres prevents the onset of bubbly flow past their point of incipient fluidization. To improve present representations of confined fluidization, experiments on several cuts of solids of various density are analysed and interpreted by adapting some fundamental relationships of the fluidization theory to the peculiar geometry provided by the confining environment

Experimental investigation of heat generation during granular flow in a rotating drum using infrared thermography

Granular flow is common in many industrial applications, and involves heat generation from frictional contacts and inelastic collisions between particles. The self-heating process is still poorly understood despite being intrinsic to many processes. This work, for the first time, explores this problem experimentally by quantifying the temperature rise of granular flows in a rotating drum with a robust methodology based on infrared thermography. Particles of four different materials (lead, steel, plastic and glass) are used in the experiments, at various rotation speeds and drum fill ratios. To assess the mechanical behaviour, the flow regime of every experiment was determined. It was inferred that particles with higher density tend to generate more heat. It was also revealed that increasing the rotation speed favours the temperature rise. At the same time, the fill ratio had the least influence on the thermal response of the particulate systems considered.his project is funded through Marie SKŁODOWSKA-CURIE Innovative Training Network MATHEGRAM, the People Programme (Marie SKŁODOWSKA-CURIE Actions) of the European Union's Horizon 2020 Programme H2020 under REA grant agreement No. 813202. Dr. Franci acknowledges the support from MCIN/AEI/10.13039/501100011033 and FEDER Una manera de hacer Europa for funding his work via project PID2021-122676NB-I00. Prof. Oñate acknowledges the Severo Ochoa Programme through the Grant CEX2018-000797-S funded by MCIN/AEI/10.13039/501100011033.Peer ReviewedPostprint (published version

Investigating the effect of sintering rate and solvent type on the liquid transport kinetics of α-alumina powder compacts

The ceramic materials' properties and the penetrating liquid both influence liquid transport into ceramic catalytic materials. Terahertz pulsed imaging (TPI) in combination with a flow cell was used to investigate the transport process of polar and less polar solvents into a range of α-alumina powder compacts. The TPI results show that the alumina samples with the largest heating rate (200 °C h−1) have the fastest water transport. The TPI results also reveal that 1-octanol takes much longer to transport through the alumina samples than water, as the viscosity of 1-octanol is much larger than that of water. Since 1-octanol is semi-transparent to terahertz radiation, it was possible to study the liquid transport process and the structural changes behind the liquid front, such as the change in the refractive index of the compact and the fill fraction of 1-octanol in the compact as a function of time

Numerical analysis of air effect on the powder flow dynamics in the FT4 Powder Rheometer

The FT4 powder rheometer of Freeman Technology is widely used nowadays in industry for characterisation of particle flow under dynamic conditions of shear strain rate. It measures the work (termed flow energy) required to penetrate a rotating impeller into a powder bed. However, little is known about its underlying powder mechanics, i.e. the relationship between the flow energy and the prevailing local shear stress. This has recently been studied, but only for very simple and ideal systems amenable to analysis by DEM. We analyse the effect of gas flow through the powder bed on the flow behaviour of cohesionless particles in FT4 by DEM-CFD simulation. The results show that the relative particle velocities induced by the mean shear speed, is of the same order as that produced by the root of granular temperature. The shear stress in both cases with and without gas flow could be quantified by the inertial number. The flow energy correlates well with the shear stress in front of the blade, and both increase with the inertial number and could be significantly reduced by the upward gas flow