Showing papers in "Powder Technology in 1999"

TL;DR: In this paper, the Hosokawa powder tester and Copley tap density volumeter were used to assess the flowability of porous and non-porous powders in which particle size changes as a result of controlling the percentage of fine components in the mixtures.

TL;DR: In this article, a theoretical model is proposed to define the failure criterion on an individual grain subjected to an arbitrary set of contact forces, and the model is implemented in a two-dimensional computer simulation code based on the molecular dynamics method to study the crushing mechanisms of grains inside a granular material under œdometric compression.

TL;DR: In this article, a selection of widely used correlations have been critically evaluated for estimating the drag coefficient of non-spherical particles in incompressible viscous fluids, including cylinders, needles, cones, prisms, discs, rectangular, parallelepiped and cubes.

TL;DR: In this paper, an overview is given on available measuring techniques for industrial routine measurements, mainly temperature and pressure drop measurements, and also some advanced techniques which are either still under development or which are particularly intended for academic investigations of basic fluidization phenomena.

TL;DR: In this article, the importance of stirred media mills in various industries and in research is steadily increasing, and the comminution process in these mills is determined mainly by the number of stress events in the grinding chamber and by the intensity acting at these stress events.

TL;DR: In this article, the authors report granular dynamics simulations of a dense spherical agglomerate consisting of a random polydisperse system of autoadhesive particles impacting orthogonally with a target wall.

TL;DR: In this paper, the effect of the antisolvent precipitation (SAS) process parameters on morphology, particle size and particle size distribution have been studied for the system tetracycline/N-methylpyrrolidone.

TL;DR: In this paper, the authors present results on organic crystals' jet milling in terms of specific energy consumption with an adaptation of the correlation proposed by Sarma, showing that, within the operating energy range and above a critical energy value, the creation of specific surface area corresponds to an increase of fine particles production.

TL;DR: In this paper, a model of force balance is developed according to the analysis of forces acting on an agglomerate of cohesive particles in a fluidized bed, where the parameters in the model are estimated.

TL;DR: In this paper, the axial distribution of slurry concentration followed the classical sedimentation-dispersion model, while the effects of gas velocity on axial solids distribution were found to be minimal over the range of gas velocities investigated.

TL;DR: In this paper, the point of zero charge (pzc) of oxides can be evaluated from the mass titration method described by Schwarz et al. The present paper proposes and validates some simplifications of this method, indicates the capabilities and limits of the simplified method and gives some applications.

TL;DR: In this paper, a shape separator and an aspirator were used for the classification of electronic scrap and its impact on the separation of personal computer (PC) scrap and printed circuit board (PCB) scrap.

TL;DR: In this paper, the effects of impact velocity and surface energy on the mechanical strength of agglomerate materials under impact have been investigated by means of computer simulation using Distinct Element Analysis (DEA).

TL;DR: Based on the motion of the grinding media in stirred media mills with disc stirrer different grinding mechanisms are possible: product particles can be stressed by grinding media which are accelerated from the stirrer shaft towards the grinding chamber wall (A), which are pressed against the chamber wall because of the centrifugal acceleration (B), and which move in tangential direction with high velocities and collide with grinding media with lower velocity (C). The importance of the three different Grinding mechanisms can be determined by evaluating the respective stress intensity and the respective number of stress events per unit time as discussed by the authors

TL;DR: In this paper, a new flow mode diagram is developed for the purpose of selecting a suitable flow mode for a particular material, based on experimental results and theoretical analysis, which can be classified into three groups (PC1, PC2 and PC3), characterised simply by loose-poured bulk density and median particle diameter.

TL;DR: The main steps of characterisation of particle morphology by image analysis, i.e., visualisation, image treatment, shape quantification, for routine use in powder technology are reviewed and illustrated by examples.

TL;DR: In this article, an analysis of the vortex motion in vertical or steeply inclined screw or auger conveyors is presented, which is characterised by the tangential component of the absolute grain velocity being substantially constant with the radial position of a point on the blade.

TL;DR: In this paper, Xie and Geldart [H.-Y. Xie, D.Geldart, Powder Technol. 90 (1997) 149] proposed 4 mm i.d. probes as a panacea for all practical situations encountered, and the results reported in this paper are obtained using a transducer with an internal volume of 1500 mm3.

TL;DR: In this paper, the authors measured bubble diameters in a bubble column, which was operating in the homogeneous regime with air and aqueous isopropanol solutions, using the theory for the conservation of the bubble size distribution function.

TL;DR: In this article, supercritical antisolvent precipitation has been applied to the production of zinc acetate with the aim of evaluating the applicability of this new process to the synthesis of controlled size nanoparticles of catalyst precursors.

TL;DR: In this paper, the influence of the solid (limestone) concentration and of the concentration of sodium polyacrylate on the apparent viscosity and the grinding efficiency of high-speed stirred ball mills was investigated.

TL;DR: In this paper, the authors used image analysis to determine the mixing rates of solids in a rotating drum using image analysis programming and showed that the mixing dynamics follow a constant rate until a completely mixed state is encountered.

TL;DR: The specific liberation effect at the disintegration of rock by electrical pulses is due to the locality of the explosive plasma streamers at the interface of mineral components of the ore aggregates with different permittivities and electrical conductivities.

TL;DR: In this article, a large-scale pneumatic cannon has been designed, constructed and tested for the adjustment of intensive stressing conditions, e.g., impact and double impact, single and multiple stressing, velocity and energy.

TL;DR: In this paper, the authors developed correlations for better prediction of solids holdups at the dense and dilute regions of circulating fluidized bed risers based on experimental data from the literature and their laboratory.

TL;DR: In this paper, the dynamics of the collision of two elastic spheres in a viscous fluid is investigated for particle Reynolds numbers ranging from 5 to 300, and the interactive behavior of these particles is examined both experimentally and theoretically.

TL;DR: In this article, the same approach was applied to gas fluidized beds of fine particles, showing that the equilibrium mixture remains stable, even in the absence of mixing forces, even under a particular combination of solids and fluid volume fractions, and the conditions corresponding to segregation potential free mixtures can be theoretically predicted from the physical properties of the system.

TL;DR: In this article, an experimental investigation of the horizontal transport of solid particles by viscous Newtonian fluids has been conducted and the experimental results show that pressure gradients of the order of 2 kPa/m are required to transport significant quantities of sand in laminar flow.

TL;DR: In this paper, the effects of system pressure, aeration rates in the two chambers of the loop seal, and particle size could be investigated, and the results showed that the solids flow rate increases with aeration rate as well as the system pressure.

TL;DR: In this article, the authors investigate the specific link between pozzolanic reaction and glassy materials and show that the reaction is a complex dissolution-precipitation reaction involving multiple parameters.