Showing papers in "Powder Technology in 1982"

TL;DR: In this article, the authors derived limiting conditions which result in a classification of powders which is equivalent to the definition given by Geldart [1], and defined the separation of powder group B from powder group A by the unimportance of cohesion forces on fluidization behavior in the case of powder groups B and C.

TL;DR: In this paper, it was shown that such a slip-voidage relation leads to a limiting envelope of lines of constant voidage on coordinates of volumetric particle flux versus fluid velocity.

TL;DR: In this article, the authors investigated the effect of particle size distribution on bed expansion of fine powders in high aspect ratio fluid beds, an expanded top bed and a circulating system, and found that changes in slope of the expansion curve were associated with regime changes, and can prove useful for the analysis of large diameter fluid beds.

TL;DR: In this article, the Ergun equation was used to predict the minimum fluidizing velocity of sand, ash, and alumina at operating temperatures up to 950 °C, and the transition between behaviour characteristic of Group B and D material types has been observed when the operating Remf value passes through ∼ 12.5 and Ar ∼ 26000.

TL;DR: In this paper, the specific rates of breakage of quartz have been studied in three tumbling ball mills, two of 195 mm i.d. and one of 0.6 m i. d., as a function of fractional ball and powder loading.

TL;DR: In this paper, the shape and size of the stagnant zones have been observed during steady-state discharge of coarse granular media (dp ⩾ 1.0 mm) from flat-bottomed bins and shallow convergent hoppers.

TL;DR: In this article, a rheological explanation of the influence of various slurry fluidity conditions on the specific rates of breakage is presented, which has proved useful in both the identification of suitable chemicals for increasing breakage rates in coal and in the plant scale implementation of dense slurry grinding systems.

TL;DR: In this article, the authors measured the void heights at an orifice in the distributor plate of a three-dimensional fluidized bed when the orifice was surrounded by other similar bubbling orifices.

TL;DR: In this article, a review of the use of low molecular weight anionic polymers as grinding additives for wet grinding of minerals is presented, and an experimental procedure is given for testing additives in a laboratory ball mill and rod mill circuits.

TL;DR: In this article, the authors propose an extension of the generally accepted two-stage compaction process to a four-stage process for agglomerated materials, and describe the mechanisms of compaction for two different spray-dried ceramic powders, a wall-tile granulate and a ferrite granulate.

TL;DR: In this paper, a new method is developed for the conversion of the distribution of measurements made on sections or projected areas to the particle mesh size distribution, which can be applied to particles of irregular shape.

TL;DR: The Fourier method of particle profile representation is presented and discussed in this paper, where rotationally invariant size and shape terms are derived from the Fourier Particle Profile representation.

TL;DR: In this paper, the authors developed a model for electrostatically augmented cyclone separators, which assumes that turbulence promotes complete radial mixing within each of three regions: the entrance region, the downflow region and the core (or upflow) region.

TL;DR: In this paper, a Faraday cage was designed and built for the purpose of measuring electrostatic charges and charge distribution on solid particles in the freeboard of a fluidized bed and a cylindrical probe was used to determine particle concentration via charge collection.

TL;DR: The influence of pressure on the behavior of different particles fluidized by nitrogen was experimentally investigated in this article, where the powders used were mostly in Geldart's group B and the pressure was varied in the range 100 to 3500 kPa.

TL;DR: In this paper, a series of five nickel electrodes 228 μm in diameter measured particle interactions with the wall along the flow path and the charge and currents transferred were measured by an electrometer-based recording system.

TL;DR: In this article, the authors developed a model to describe purely material effects, allowing for fast and slow breakage of feed material, for batch and continuous operation, in a ball mill with two distinct assumptions: (a) that fast-breaking material produces only fast breaking material, and (b) slow-breaking produces only slow breaking material.

TL;DR: In this article, a direct shear tester equipped with a press loading system has been employed to measure the failure properties of granular materials and cohesive powders, and a yield locus for such materials can be obtained from one shear test by a continuous line.

TL;DR: In this paper, a mathematical model was developed for a ball-and-race mill based on specific rates of breakage and primary fragment distributions, including internal classification of particles falling back into the race and external classification due to the built-on classifier.

TL;DR: In this article, the authors present an analytical description for the progeny size distribution of irregularly shaped particles crushed singly by slow compression and show that the size distribution is truncated log-normal.

TL;DR: In this article, it has been shown that producing an ordered mixture at 0 or 84% relative humidity results in significantly less segregation of the carrier particles, and this finding has application as a simple method of minimizing ordered unit segregation during a mixing operation.

TL;DR: In this article, the influence of a chemical dispersant on the hydrocycloning of a copper ore slurry and a slurry mixture of copper and magnetic iron ores was investigated.

TL;DR: In this paper, the phase boundary controlled rate equation or the nucIeigrowth one was used to study the kinetics of decomposition of BaC03 (1050 to I 170 ) and SrCO (900 to 1000 ) as a function of sample mass and processing pressure.

TL;DR: In this paper, the authors proposed a new method of graphical display of grinding data as straightline plots, the intercepts of which are breakage distribution functions, which is shown to be highly accurate, is not restricted to short grinding time data and is not subjected to any restrictive interrelationship between breakage-rate constants and breakage distributions.

TL;DR: In this article, the scale-up of breakage parameters measured in the Hardgrove mill to large mill diameters, using a simulation model for continuous milling, is discussed.

TL;DR: In this article, the equations of continuity and momentum balance for a cohesionless Coulomb powder discharging from a wedge-shaped hopper are solved by an iterative procedure, which generates series solutions in inverse cubic powers of distance from the vertex of the hopper.

TL;DR: In this article, a common property of direct-compression (DC) tabletting vehicles used in the pharmaceutical industry is high intra-granular porosity, which leads to increased interparticulate friction on compaction and subsequently an increased extent of bonding compared with the parent crystals.

TL;DR: In this paper, a relation between these variables (eqn. 4) makes the determination of the latter easier, and only one empirical constant for each material class has to be determined.

TL;DR: In this paper, the authors measured the tensile strength of a powder bed by means of the swing method measuring instrument, which has been developed by the authors, and the effects on the void fraction and the moisture content have been investigated.