The Effects of Thermally Induced Interparticle Forces on the Expansion and Bubbling Behaviour of a Fluidized Bed

The paper addresses the transition to the bubbling regime of solid beds belonging to Geldart’s group A, from ambient temperature to 500°C. The analysis of the influence exerted by operating temperature on the variables that characterize both the homogeneous expansion of the bed and the onset of a steady bubbling regime is conducted on the fluidization map of the fluidized bed, namely the voidage velocity diagram into which results of the fluidization and bed collapse experiments are merged. The results obtained show that at elevated temperatures the ability of the fluidized bed to preserve the homogeneous fluidization regime is extended to unusually high voidage levels. Even past the appearance of a steady bubble flow, the dense phase voidage exhibits a residual dependence on interparticle forces induced by high temperature

The Variation of the Bubble Phase Properties of a FCC Fluidized Bed at High Temperature

Some important characteristics of the bubbling regime, relevant to a cut of FCC catalyst with an average size of 110 mm were investigated at 100, 400 and 700 °C. This was achieved by imploying data of bed collapse tests as well as images of the bubble eruption at the free surface of the bed by varying fluidization velocities and bed aspect ratios. The results show that a smoother regime of fluidization is observed at superambient temperature

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

The Fluidization Pattern of Density-Segregating Two-Solid Beds

An experimental work is presented meant to clarify the specific role played by density differences between components in the segregating fluidization process of two-solid beds. The overall behaviour of such systems is characterized by substituting the traditional concept of “minimum fluidization velocity” of the binary mixture with the “velocity interval of fluidization” of the bed, which is limited by its “initial” and “final” fluidization velocity”. The dependence of these characteristic velocities on parameters such as component densities and mixture composition is illustrated by several series of experiments. The experimental results are analysed in the light of the fundamental theory, so as to establish quantitative relationships for their prediction. The evolution of the axial profile of component concentration at varying fluidization velocity is also discussed

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

The Italian auditing legal regime between domestic legal system and European reforms

Nel presente lavoro si fornisce una descrizione della disciplina della revisione dei conti come delineata dal D. Lgs. 39/2010 - ponendo particolare attenzione alle evoluzioni che deriveranno dall'attuazione della riforma europea del 2014. L'analisi si basa, in particolare, sulla valutazione del ruolo che il revisore svolge nei problemi di agency nel contesto societario e del c.d. modello del gatekeeping - sottolineando le interconnessioni esistenti tra le due funzioni -. A conclusione del lavoro, si traggono alcune valutazioni, in termini di efficacia ed efficienza, riguardo al sistema vigente, ipotizzando alcune possibili riforme future.In this dissertation, the Author describes the Italian legal regime of auditing, as laid down in Legislative Decree No. 39 of 2010 with a specific reference to European overhaul enacted in 2014. Such analysis is grounded on a preliminary evaluation of the role that the auditing plays in the corporate agency relations and the gatekeeping model (and, most notably, the strong ties between them). Given the foregoing, some conclusions are drawn both with regard to the effectiveness of the current regulatory system and envisioning some proposals for reform

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

Adsorption of CO2 on amine-modified silica particles in a confined-fluidized bed

To reduce the anthropogenic CO2 emissions produced from fossil fuel burning plants, the application of carbon capture and storage (CCS) is necessary and development of a more efficient and economically feasible CO2 capture process is essential as an alternative to the conventional amine scrubbing process which uses aqueous amine solutions. CO2 capture can be enhanced by improving both the gas–solid contact efficiency and by tuning a specific high-performance sorbent. The aim of this research is to investigate the adsorption of CO2 using impregnated mesoporous silica in a “confined-fluidized bed”. This non-conventional fluidized bed (sometimes also termed the “packed-fluidized bed”) seems suitable for improving the efficiency of gas–solid processes for which the bypass effect of the gas–solid contact caused by bubbling represents a major drawback. Results, expressed as grams of CO2 adsorbed per kilogram of material, are discussed in terms of amine load in the sorbent, breakthrough time and fraction of bed utilized. The stability of the materials after regeneration cycles is also discussed. The results obtained confirm that the confinement of the bed allows exploiting fluidization technology in adsorption operations. The operating velocity can be fixed at a value at which the thermal effects also connected to the operation are kept under control