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JournalISSN: 0032-5910

Powder Technology 

About: Powder Technology is an academic journal. The journal publishes majorly in the area(s): Particle & Fluidized bed. It has an ISSN identifier of 0032-5910. Over the lifetime, 15665 publication(s) have been published receiving 393785 citation(s).

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Journal ArticleDOI
Abstract: The behaviour of solids fluidized by gases falls into four clearly recognizable groups, characterized by density difference (ϱs–ϱf) and mean particle size. The most easily recognizable features of the groups are: powders in group A exhibit dense phase expansion after minimum fluidization and prior to the commenment of bubbling; those in group B bubble at the minimum fluidization velocity; those in group C are difficult to fluidize at all and those in group D can form stable spouted beds. A numerical criterion which distinguishes between groups A and B has been devised and agrees well with published data. Generalizations concerning powders within a group can be made with reasonable confidence but conclusions drawn from observations made on a powder in one group should not in general be used to predict the behaviour of a powder in another group.

2,750 citations

Journal ArticleDOI
Abstract: Numerical simulation, in which the motion of individual particles was calculated, was performed of a two-dimensional gas-fluidized bed. Contact forces between particles are modeled by Cundall's Distinct Element Method (P.A. Cundall and O.D.L. Strack, Geotechnique, 29 (1979) 47), which expresses the forces with the use of a spring, dash-pot and friction slider. The gas was assumed to be inviscid and its flow was solved simultaneously with the motion of particles, taking into account the interaction between particles and gas. The simulation gives realistic pictures of particle motion. Formation of bubbles and slugs and the process of particle mixing were observed to occur in the same way as in experiments. The calculated pressure fluctuations compared well with measurements.

1,759 citations

Journal ArticleDOI
Abstract: Explicit equations are developed for the drag coefficient and for the terminal velocity of falling spherical and nonspherical particles. The goodness of fit of these equations to the reported experimental data is evaluated and is compared with that of other recently proposed equations. Accurate design charts for CD and ut are prepared and displayed for all particle sphericities.

1,382 citations

Journal ArticleDOI
Abstract: Lagrangian-type numerical simulation was carried out on plug flow of cohesionless, spherical particles conveyed in a horizontal pipe. The motion of individual particles contacting each other was calculated using the equations of motion and a modified Cundall model. Forces between particles were expressed by using the Hertzian contact theory. The Ergun Equation was applied to give the fluid force acting on particles in a moving or stationary bed. The flow patterns obtained in the present work appear to be realistic. The wave-like motion of the flow boundary reported previously by several other researchers was observed clearly in the simulation. Also, good agreement was obtained for the relation between the height of the stationary deposited layer and the plug flow velocity. Due to the limitations of computation time, only the case of large particles (ie. d > 10 mm) could be considered here.

1,343 citations

Journal ArticleDOI
Abstract: Wet agglomeration processes have traditionally been considered an empirical art, with great difficulties in predicting and explaining observed behaviour. Industry has faced a range of problems including large recycle ratios, poor product quality control, surging and even the total failure of scale up from laboratory to full scale production. However, in recent years there has been a rapid advancement in our understanding of the fundamental processes that control granulation behaviour and product properties. This review critically evaluates the current understanding of the three key areas of wet granulation processes: wetting and nucleation, consolidation and growth, and breakage and attrition. Particular emphasis is placed on the fact that there now exist theoretical models which predict or explain the majority of experimentally observed behaviour. Provided that the correct material properties and operating parameters are known, it is now possible to make useful predictions about how a material will granulate. The challenge that now faces us is to transfer these theoretical developments into industrial practice. Standard, reliable methods need to be developed to measure the formulation properties that control granulation behaviour, such as contact angle and dynamic yield strength. There also needs to be a better understanding of the flow patterns, mixing behaviour and impact velocities in different types of granulation equipment. (C) 2001 Elsevier Science B.V. All rights reserved.

1,016 citations

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