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

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

Comparison of cohesive powder flowability measured by Schulze Shear Cell, Raining Bed Method, Sevilla Powder Tester and new Ball Indentation Method

Poor powder flow leads to many problems during manufacturing and can lead to inaccurate dosing and off-specification products. Powder flowability is commonly assessed under relatively high applied loads using shear cells by characterising the unconfined yield strength at a range of applied loads. For applied stresses below 1 kPa, it becomes increasingly difficult to obtain reliable values of the unconfined yield strength. The bulk cohesion and tensile strength of the powder are then obtained by extrapolating the yield locus to zero and negative loads, respectively. However, the reliability of this approximation for a given material is not known. To overcome this limitation, techniques such as the Raining Bed Method, Sevilla Powder Tester and the newly-developed Ball Indentation Method may be used. In this paper, we report our measurement results of the tensile strength of glass beads, α-lactose monohydrate and various sizes of fluid catalytic cracking powders determined by the Sevilla Powder Tester and Raining Bed Method and compare them with those inferred from the Schulze Shear Cell. The results of the latter are also compared with those of the Ball Indentation Method. The outcome suggests that in the case of shear cell tests, the extrapolation of the yield locus to lower or negative loads is unsafe. The ball indentation method enables the characterisation of highly cohesive powders at very low compressive loads; however extrapolation to negative loads is still not reliable. In contrast, the Sevilla Powder Tester and Raining Bed Methods are able to characterise the tensile strength directly, but high bulk cohesion poses difficulties as the internal bed failure needs to be analysed in order to reliably estimate the tensile strength. These methods provide a better understanding of powder flow behaviour at low stresses, thus enabling a greater control of manufacturing processes

Extension of the model of binary fluidization to beds confined in a packing of coarse spheres

The prediction of the minimum fluidization velocity of beds of Geldart's group B particles confined in a packed bed of coarse spheres can be achieved by extending to this peculiar type of systems the theory developed for modelling the behaviour of segregating beds of simultaneously fluidized solids. The approach is based on separate force balances on the fluid and the fine solids, capable to account for the peculiar nature of solid-solid interaction in a confined fluidized bed. Its validation is fulfilled by an extended investigation conducted in two columns (5 and 10 cm OD) packed with a fixed bed of 4.1 mm lead shots or 11 mm glass beads. The effect of particle size on the fluidization regime is investigated by comparing the results provided by experiments in which various cuts of glass ballotini, ranging from 100 to nearly 600 μm, are fluidized in two packings of fixed spheres; possible differences of behaviour due to particle density are analysed by series of experiments employing particles of ceramics, zirconium oxide, steel and bronze of the same diameter. The results obtained confirm the effectiveness of the approach followed, in which an important role is played by the indirect interaction between the two solid phases

The influence of operating temperature on the dense phase properties of bubbling fluidized beds of solids

The paper analyses the dependence on process temperature of parameters that characterize the dense phase of a freely bubbling bed. Application of the bed collapse technique to beds of FCC, silica sand, and corundum in experiments covering a temperature field ranging from room level up to 700 jC demonstrates that the increase of interparticle forces at superambient temperatures leads to significant modifications of the fluidization dynamics. These include clear changes of the particulate phase voidage and dense phase velocity as well as of bubble hold-up. Changes induced in the partition of the total gas flow rate and, consequently, in the characteristics of the bubble phase of the fluidized bed are also discussed

Segregating fluidization of two-solid beds:development of the approach based on the fluidization velocity interval

Dottorato di Ricerca in: Dottorato di Ricerca in Ingegneria Chimica e dei Materiali, Ciclo XXIII, a.a.2009-2010Università della Calabri