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Abdelhamid Ajbar

Bio: Abdelhamid Ajbar is an academic researcher from King Saud University. The author has contributed to research in topics: Population & Fluidization. The author has an hindex of 16, co-authored 82 publications receiving 807 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a portable and hybrid solar-powered membrane distillation (SPMD) system for producing freshwater in remote arid and/or coastal areas like in Saudi Arabia is presented.

86 citations

Journal ArticleDOI
TL;DR: In this paper, the use of sound vibration as well as mixing of particles is investigated for improving the fluidizability of nano-powders. But the results of the experiments were limited to a limited range of bed operation owing to the high elutriation rates of the bed material.

51 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of the addition of small proportions of group A on the fluidization behavior of a group C powder were studied and the results showed that the addition substantially improved the fluidisation behavior of the bed even at low superficial gas velocities, leading to more uniform fluidization.
Abstract: The gas fluidization behaviour of fine cohesive powders, classified as Geldart group C, is known to be characterized by cracks and channels leading to severe non-homogeneities in the bed. Geldart group A particles, on the other hand, are known to show more homogeneous and regular fluidization behaviour. This paper studies the effects of the addition of small proportions of group A on the fluidization behaviour of a group C powder. Differential pressure fluctuations data at a sampling frequency of 200 Hz were recorded for two cases. In the first case, the bed contained only group C powder while in the second case small amounts of group A particles were added to the existing group C powder. Visual/image observations coupled with time series analysis showed that the addition of small proportions of group A particles substantially improved the fluidization behaviour of the bed even at low superficial gas velocities, leading to a more uniform fluidization. Evaluation of mean and standard deviations has shown the advantage of mixing the two powders as it allowed larger pressure fluctuations and smaller standard deviations. Power spectra, on the other hand, showed that unlike group C, for which fluctuations were small in magnitude and broadband in structure, the mixture showed stronger periodic behaviour as result of the attenuation of the small and rapid fluctuations caused by the flow of gas in the cracks and channels. Advanced methods such as the principal component analysis of the embedded trajectories allowed a quantitative comparison between the fluidization behaviour of the two systems.

35 citations

Journal ArticleDOI
TL;DR: In this paper, a bed collapse experiment was carried out in a pulsed-flow fluidized bed containing a widely used nano-powder that shows strong agglomeration behavior.

33 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used a hydrophone in an air-water bubble column to study the hydrodynamics of the unit, and measured measurements taken at different superficial gas velocities are processed using both spectral and chaos-based techniques in order to characterize the column flow regimes and to predict the transitions points.
Abstract: Passive acoustic sound, measured by a hydrophone in an air–water bubble column, is used to study the hydrodynamics of the unit. The recorded measurements taken at different superficial gas velocities are processed using both spectral and chaos-based techniques in order to characterize the column flow regimes and to predict the transitions points. These processing tools were supported by digital video imaging of bubbles motion inside the column. The results of data analysis indicate the applicability of passive sound measurements to identify flow regimes in the bubble column. In this regard the analysis of sound spectra gives a useful qualitative comparison of flow regimes. Chaos-based techniques, on the other hand, are more successful in predicting the transition points between the homogenous and the churn-turbulent flow regimes in the column. The critical gas velocities of the transition are associated with a marked change in some of the calculated chaotic invariants of sound pressures. The calculated superficial gas velocities of the critical points are also found to be consistent with experimental observations. Moreover, a useful visualization of the dynamics induced in the column by the alternation of small and large bubbles is possible through the inspection of phase-space trajectories reconstructed from time-series measurements. The shape and size of the trajectories are closely linked to the size distribution of bubbles, and they change as the flow moves from one regime to an other.

29 citations


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10 Mar 2020

2,024 citations

Journal ArticleDOI
TL;DR: The effects of anions, cations and functional groups on CO2 solubility and selectivity ofILs, as well as the studies on degradability of ILs are reviewed, and the recent developments on functionalized ILs, IL- based solvents, and IL-based membranes are discussed.
Abstract: The inherent structure tunability, good affinity with CO2, and nonvolatility of ionic liquids (ILs) drive their exploration and exploitation in CO2 separation field, and has attracted remarkable interest from both industries and academia. The aim of this Review is to give a detailed overview on the recent advances on IL-based materials, including pure ILs, IL-based solvents, and IL-based membranes for CO2 capture and separation from the viewpoint of molecule to engineering. The effects of anions, cations and functional groups on CO2 solubility and selectivity of ILs, as well as the studies on degradability of ILs are reviewed, and the recent developments on functionalized ILs, IL-based solvents, and IL-based membranes are also discussed. CO2 separation mechanism with IL-based solvents and IL-based membranes are explained by combining molecular simulation and experimental characterization. Taking into consideration of the applications and industrialization, the recent achievements and developments on the t...

613 citations

Journal ArticleDOI
TL;DR: The present review aims to summarize the recent advances in the fundamental and application understanding of ILs, and introduces the structures and properties of typical ILs.
Abstract: Ionic liquids (ILs) offer a wide range of promising applications because of their much enhanced properties. However, further development of such materials depends on the fundamental understanding of their hierarchical structures and behaviors, which requires multiscale strategies to provide coupling among various length scales. In this review, we first introduce the structures and properties of these typical ILs. Then, we introduce the multiscale modeling methods that have been applied to the ILs, covering from molecular scale (QM/MM), to mesoscale (CG, DPD), to macroscale (CFD for unit scale and thermodynamics COSMO-RS model and environmental assessment GD method for process scale). In the following section, we discuss in some detail their applications to the four scales of ILs, including molecular scale structures, mesoscale aggregates and dynamics, and unit scale reactor design and process design and optimization of typical IL applications. Finally, we address the concluding remarks of multiscale strat...

517 citations

Journal ArticleDOI
TL;DR: In this article, the general principles and applications of SLM are discussed, followed by the uphill transportation characteristic of SLMs. And the salient features of the supported liquid membrane (SLM) technique such as simultaneous extraction and stripping, low solvent inventory, process economy, high efficiency, less extractant consumption, and operating costs are discussed in detail.
Abstract: The present paper on the supported liquid membrane (SLM) deals with the general principles and applications, followed by the uphill transportation characteristic of SLM. The liquid-liquid extraction with supported liquid membrane is one of the best alternate and promising technologies for the extraction of metal ions from solutions over other hydrometallurgical separation processes. The salient features of the supported liquid membrane (SLM) technique such as simultaneous extraction and stripping, low solvent inventory, process economy, high efficiency, less extractant consumption, and operating costs are discussed in detail. The supported liquid membrane of hollow fiber type provides high interfacial surface area for achieving maximum metal flux. Also the use of different organic extractants for SLM has been discussed.

192 citations

Journal ArticleDOI
TL;DR: A comprehensive state‐of‐the‐art review on scCO2‐based processes focused on the formation and on the control of the physicochemical, structural and morphological properties of amorphous/crystalline pure drug nanoparticles.

164 citations