Showing papers in "Powder Technology in 1998"

TL;DR: In this article, the authors considered the normal impact of elastic-perfectly plastic spheres, with and without interface adhesion, and presented an analytical solution for the coefficient of restitution which is expressed in terms of the impact velocity, the critical sticking velocity and the velocity below which the interaction is assumed to be elastic.

TL;DR: In this paper, the effect of shear history on the evolution of the polystyrene-alum floc size, density, and structure is investigated by small-angle light scattering during cycled-shear and tapered-Shear flocculation in a stirred tank using a Rushton impeller.

TL;DR: In this paper, the mixing/segregation properties of binary systems of different size but equal density are related to the visible bubble flow rate, the particle size ratio, and other parameters of minor influence.

TL;DR: An Eulerian/Lagrangian-type numerical simulation was performed on a two-dimensional fluidized bed in which the particle motion is restricted by parallel front and rear walls.

TL;DR: In this paper, the authors compared the results of the two-fluid model and the discrete particle model to predict flow patterns in the riser of a circulating fluidized bed.

TL;DR: In this paper, a multi-fiber optical reflection probe was uniquely calibrated in a downer to obtain quantitatively precise solids holdup, and an iteration procedure was utilized to modify the initial calibration curves.

TL;DR: In this article, a study of the agglomeration behavior of comminuted calcium carbonates having sizes ranging from 4 to 23 μm was performed and a single low viscosity binder was used and the mixer and conditions of mixing were kept constant.

TL;DR: In this article, a physically based model for the numerical prediction of wall-bounded particulate flows is presented, which is of great interest for the powder processing industries in order to support process development and optimisation.

TL;DR: In this article, it was shown that the measured pressure fluctuations are a result of slow and fast propagating pressure waves, which are unambiguously identified as compression waves, and the amplitude of upward moving pressure waves is linearly dependent on the distance to the bed surface.

TL;DR: In this paper, the applicability of a near-infrared reflectance spectroscopic method was tested for the determination of water during different unit operations performed in a fluidized bed granulator.

TL;DR: In this paper, a room temperature grinding of talc powder was conducted by a planetary ball mill using media balls of different sizes, and the grinding behavior of the talc sample was investigated by X-ray diffraction (XRD) and particle size distribution analyses.

TL;DR: In this paper, the change of porosity with time was found to be well described by a simple, empirical, exponential decay equation: e−e min e O −e min = exp (−N) where ϵ is the average granule porosity after N drum revolutions, ϵ 0 is the initial average porosity of the feed and ϵmin is the minimum porosity reached by the tumbling granules and k is the consolidation rate constant.

TL;DR: In this article, a distinct element model is used to study the hydrodynamics of large-particle fluidized beds and the bubble rise velocity, voidage variations, averaged particle/particulate and fluid velocities are compared with the other continuum theory based on two fluid models.

TL;DR: In this paper, the authors examined the agglomeration of a powder mixture which is commonly used to make granules containing enzyme in a high shear mixer granulator of the Lodige type.

TL;DR: In this article, the tensile strength of a powder is related to the interparticle force and to the free volume, which, in turn, are related to consolidation stress, and the relationship between stress and free volume is described by the state diagram that has been measured at zero shear for a set of cohesive powders (xerographic toners) with a range of concentrations of a flow control additive.

TL;DR: In this paper, a novel experimental setup was developed to perform in situ measurement and monitoring of the dust cake height, pressure drop, and the challenge aerosol concentration and size distribution.

TL;DR: In this paper, the axial development of these radial profiles and the influence of operating conditions on the profiles were examined, and the results showed that similar radial profiles of solids fraction exist in the HDCFB.

TL;DR: In this paper, the impact behavior of liquid-bound granules and pellets was studied using a simple but simple experimental technique, and the effect of varying binder content in a particular system cannot be predicted a priori.

TL;DR: In this paper, the influence of particle shape on particle size distributions measured with commercial particle-size analyzers has been investigated, and the results of a round robin that has been performed to investigate the influence on particle shape has been found to have a strong influence on the particle size distribution.

TL;DR: In this paper, a mathematical model to predict an equilibrium agglomerate size in the Geldart group C powders was derived based on the balance of the bed expansion force caused by bubbles and agglerate-to-agglomerate cohesive rupture force.

TL;DR: In this article, the dynamics of the bottom bed in small size circulating fluidized bed risers are significantly different from those of large size risers, and two types of circulating regimes are introduced: the exploding bubble bed for large risers and the circulating slugging bed for small risers.

TL;DR: In this article, the thermal decomposition process of anhydrous zinc acetate dihydrate was studied by differential thermal analysis (DTA) and thermal gravimetric analysis (TGA) and it was shown that the water of crystallization is removed at below 200 °C.

TL;DR: In this paper, a model is introduced which describes agglomerate growth as a function of time, and two stages of growth are discerned: fast growth by wetting of the powder particles by a droplet, which result in the formation of an initial aggregates, and a second stage of slower growth, which results from drainage of binder liquid from the initial aggregation to the outer layers of the growing aggregates.

TL;DR: In this article, a needle capacitance probe was used to obtain measurement of instantaneous solids concentration (e s ) in a small sampling volume of approximately 0.1 cm 3.

TL;DR: In this paper, the normal impact between two grinding balls is quantified in terms of collision force, contact radius, contact time, and collision energy, using expressions developed by previous investigators from the principles of continuum mechanics.

TL;DR: In this article, the S-shaped profile of axial pressure gradient characteristic of a circulating fluidized bed riser operating at fast fluidization conditions was determined by measurement of radial profiles of solids momentum and solids volume fraction.

TL;DR: In this paper, the authors investigated microencapsulated phase-change materials as heat transfer media in gas-fluidized beds, including shells of polymethylene-urea, cross-linked nylon, and gelatin and cores of octadecane and paraffin.

TL;DR: In this article, the elutriation of fine powders from a fluidized bed of a fine-coarse particle mixture was investigated in a transparent column with a diameter of 7.1 cm and a height of 102 cm at gas velocities from 0.3 to 0.9 m/s.

TL;DR: In this article, a new conceptual approach is proposed which is based on a comparison of the characteristic times for quiescent motion of particles in a bed and for the growth of sinter necks.

TL;DR: In this article, an experimental study of the packing of spherical particles with special reference to the effect of liquid addition was conducted, which showed that the properties of both particle and liquid affect the packing behavior significantly.