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interparticle forces IN HIGH TEMPERATURE FLUIDIZATION OF GELDART A PARTICLES

China Particuology 2004年第3期2卷 113-118页

作者： Jamal Chaouki Biopro Research Centre Department of Chemical Engineering Ecole Polytechnique de Montreal C.P. 6079 succ. Centre-ville Montreal Quebec Canada H3C 3A7

Previous reports and current studies show that fluidization of some Geldart A particles is enhanced by increasing bed temperature. Both the averaged local particle concentration and the particle concentration in the dense phase decrease with increasing bed temperature, at constant superficial gas velocities. However, conventional models fail to predict these changes, because the role of interparticle forces is usually neglected at different bed temperatures. Here, the interparticle forces are analyzed to explore the mechanism of gas-solid fluidization at high temperatures. Indeed, as the temperature increases, the interparticle attractive forces decrease while the interparticle repulsive forces increase. Consequently, fluidization behaviors of some Geldart A particles seem to increasingly shift from typical Geldart A towards B with increasing temperature.

关键词： fluidization gas-solid flow structure high temperature interparticle forces

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Dry powder platform for pulmonary drug delivery

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Particuology 2008年第4期6卷 225-238页

作者： Derek Ivan Daniher Jesse Zhu Graduate Program in Biomedical Engineering Department of Chemical and Biochemical EngineeringThe University of Western OntarioLondonOntarioCanada

The phenomenon of particle interaction involved in pulmonary drug delivery belongs to a wide variety of disciplines of particle technology, in particular, fluidization. This paper reviews the basic concepts of pulmonary drug delivery with references to fluidization research, in particular, studies on Geldart group C powders. Dry powder inhaler device-formulation combination has been shown to be an effective method for delivering drugs to the lung for treatment of asthma, chronic obstructive pulmonary disease and cystic fibrosis. Even with advanced designs, however, delivery efficiency is still poor mainly due to powder dispersion problems which cause poor lung deposition and high dose variability. Drug particles used in current inhalers must be 1–5 μm in diameter for effective deposition in small-diameter airways and alveoli. These powders are very cohesive, have poor flowability, and are difficult to disperse into aerosol due to cohesion arising from van der Waals attraction. These problems are well known in fluidization research, much of which is highly relevant to pulmonary drug delivery.

关键词： Dry powder inhaler interparticle forces Aerosol Pulmonary drug delivery Carrier particle Fluidization

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Temperature influence on minimum fluidization velocity:Complexity,mechanism,and solutions

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Particuology 2024年第5期88卷 344-349页

作者： Qingjin Zhang Liangliang Fu Guangwen Xu Dingrong Bai Key Laboratory on Resources Chemicals and Material of Ministry of Education Shenyang University of Chemical TechnologyShenyang 110142China School of Materials Science and Engineering Shenyang University of TechnologyShenyang 110142China School of Chemical Engineering University of Science and Technology LiaoningAnshan 114051China

Fluidized-bed reactors are widely employed in various high-temperature industrial ***,it is crucial to understand the temperature effect on various fluidization phenomena,specifically the minimum fluidization velocity(U_(mf))that governs various aspects of fluidized bed *** this study,we comprehensively analyze U_(mf) data from the literature to unravel the complexity and underlying mechanisms of temperature influence on this critical *** research examines experimental data encompassing a wide range of temperatures,pressures,and solid *** analysis reveals that the influence of temperature on U_(mf) is fundamentally determined by the relative importance of hydrodynamic forces and interparticle forces within fluidized beds and is realized by three distinctive temperature-induced changes:gas properties,bed voidage,and physiochemical characteristics of *** this basis,an equation is derived to enable predictions of temperature influences on the minimum fluidization velocity under broad temperature conditions.

关键词： High-temperature gas-solids fluidized beds Minimum fluidization velocity Hydrodynamic forces interparticle forces Bed voidage

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Understanding the forces acting in self-assembly and the implications for constructing three-dimensional （3D） supercrystals

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Nano Research 2015年第8期8卷 2445-2466页

作者： Chenyu wang1 Carrie Siu Jun Zhang Jiye Fang Department of Chemistry State University of New York at Binghamton Binghamton New York 13902 USA Materials Science and Engineering Program State University of New York at Binghamton Binghamton New York 13902 USA State Key Laboratory of Heavy Oil Processing College of Chemical Engineering China University of Petroleum Qingdao 266580 China

The assembly of nanocrystals into ordered structures called supercrystals or superstructures has become a pivotal frontier owing to numerous useful applications such as correlating the arrangements of atoms in macroscopic crystals and tuning the collective properties to meet the demands of various applications. In this article, recent progress in the preparation of three-dimensional superlattices of nanocrystals is outlined, with a particular emphasis on the driving forces and evolutionary routes beyond orderly assembly. First, the leading or repulsive forces that internally and externally govern the formation of three-dimensional supercrystals are systematically identified and discussed with respect to their origins and functions in three-dimensional self-organization. Then a synoptic introduction of commonly applied means of nanocrystal self-assembly based on growth scenarios such as droplet evaporation and a liquid/liquid interface is presented with specific cases and detailed analyses. Finally, the existing challenges and prospects for this field are briefly highlighted.

关键词： interparticle forces superlattices supercrystals three-dimensional self-assembly

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EFFECTS OF GAS TYPE AND TEMPERATURE ON FINE PARTICLE FLUIDIZATION

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China Particuology 2006年第3期4卷 114-121页

作者： Chunbao Xu J.-X. Zhu Department of Chemical Engineering Lakehead University Thunder Bay Ontario P7B 5E1 Canada powder Technology Research Centre Department of Chemical & Biochemical Engineering The University of Western Ontario London Ontario N6A 5B9 Canada

The influence of gas type （helium and argon） and bed temperature （77-473 K） on the fluidization behaviour of Geldart groups C and A particles was investigated. For both types of particles tested, i.e., Al2O3 （4.8μm） and glass beads （39 μm）, the fluidization quality in different gases shows the following priority sequence： Ar 〉 He. In the same gaseous atmosphere, the particles when fluidized at an elevated temperature usually show larger bed voidages, higher bed pressure drops, and a lower Umf for the group A powder, all indicating an enhancement in fluidization quality. Possible mechanisms governing the operations of gas type and temperature in influencing the fluidization behaviours of fine particles have been discussed with respect to the changes in both gas properties and interparticle forces （on the basis of the London-van der Waals theory）. Gas viscosity （varying significantly with gas-type and temperature） proves to be the key parameter that influences the bed pressure drops and Umf in fluidization of fine particles, while the interparticle forces （also varying with gas-type and temperature） may play an important role in fine-particle fluidization by affecting the expansion behaviour of the particle-bed.

关键词： fluidization fine particles gas type temperature interparticle forces

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EFFECTS OF GAS TYPE AND TEMPERATURE ON FINE PARTICLE FLUIDIZATION

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Particuology 2006年第Z1期 114-121页

作者： Chunbao Xu1,* and J.-X. Zhu2 1Department of Chemical Engineering, Lakehead University, Thunder Bay, Ontario, P7B 5E1, Canada 2Powder Technology Research Centre, Department of Chemical & Biochemical Engineering, The University of Western Ontario, London, Ontario, N6A 5B9, Canada

The influence of gas type (helium and argon) and bed temperature (77?473 K) on the fluidization behav- iour of Geldart groups C and A particles was investigated. For both types of particles tested, i.e., Al2O3 (4.8 μm) and glass beads (39 μm), the fluidization quality in different gases shows the following priority sequence: Ar > He. In the same gaseous atmosphere, the particles when fluidized at an elevated temperature usually show larger bed voidages, higher bed pressure drops, and a lower umf for the group A powder, all indicating an enhancement in fluidization quality. Possible mechanisms governing the operations of gas type and temperature in influencing the fluidization behaviours of fine par- ticles have been discussed with respect to the changes in both gas properties and interparticle forces (on the basis of the London-van der Waals theory). Gas viscosity (varying significantly with gas-type and temperature) proves to be the key parameter that influences the bed pressure drops and umf in fluidization of fine particles, while the interparticle forces (also varying with gas-type and temperature) may play an important role in fine-particle fluidization by affecting the ex- pansion behaviour of the particle-bed.

关键词： fluidization fine particles gas type temperature interparticle forces

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