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

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

Amine‐Functionalized Mesoporous Silica Adsorbent for CO2 Capture in Confined‐Fluidized Bed: Study of the Breakthrough Adsorption Curves as a Function of Several Operating Variables

Carbon capture, utilization, and storage (CCUS) is one of the key promising technologies that can reduce GHG emissions from those industries that generate CO2 as part of their production processes. Compared to other effective CO2 capture methods, the adsorption technique offers the possibility of reducing the costs of the process by setting solid sorbent with a high capacity of adsorption and easy regeneration and, also, controlling the performance of gas‐solid contactor. In this work, an amine‐functionalized mesoporous sorbent was used to capture CO2 emissions in a confined‐fluidized bed. The adoption of a confined environment allows the establishment of a homogeneous expansion regime for the sorbent and allows to improve the exchange of matter and heat between gas and solid phase. The results illustrate how the different concentration of the solution adopted during the functionalization affects the adsorption capacity. That, measured as mg of CO2 per g of sorbent, was determined by breakthrough curves from continuous adsorption tests using different concentrations of CO2 in air. Mesoporous silica functionalized with a concentration of 20% of APTES proves to be the best viable option in terms of cost and ease of preparation, low temperature of regeneration, and effective use for CO2 capture

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