Particle cycle times in a spouted bed of polydisperse particles

Self Cite

A new experimental technique for measuring particle cycle times, times of occurrence of particles at different levels, and particle velocities in the spout of a spouted bed is described. A magnetized marker particle and search coil or coils are employed together with a microprocessor system for ease of data collection and processing. The magnetic particles have the same diameter, density and similar surface texture to bed particles to ensure proper representation.Data is presented on distributions of cycle time and particle velocity and implied particle mass circulation rates at different levels in a spouted bed. Comparisons are made with photographic and laser-doppler anemometry techniques.On dCcrit une nouvelle technique expkrimentale pour mesurer la duree du cycle des particules, les temps d'apparition des particules ti diffkrentes hauteurs et la vitesse des particules dans le bec d'un lit << spoute B. On utilise une particule d'un marqueur magnktique, une ou des bobines de repkrage, un systeme de microprocesseur pour faciliter I'acquisition et le traitement des donnees. Les particules magnetiques ont le m h e diametre, la m h e densite et la mkme texture de surface que les particules du lit afin d'assurer une reprksentation juste.On prksente des donnkes sur les distributions des durees de cycle et les vitesses des particules et des donnies calculees de debits massiques de particules a diffkrentes niveaux dans le lit <( spout6 >>. Des comparaisons sont Ctablies avec les techniques d'anCmomCtrie laser-doppler et des techniques photographiques.

Section: Equipmentsupporting

confidence: 75%

“…Particle trajectories in the spout and annulus and cycle times have been studied using photography on half-section beds (Robinson and Waldie, 1978;Suciu and Patrascu, 1977). In one of the earliest studies Becker ( 196 I ) timed the appearances on the annulus surface of a single marked particle to obtain particle cycle times.…”

Section: Introductionmentioning

confidence: 99%

“…Particle trajectories in the spout and annulus and cycle times have been studied using photography on half-section beds (Robinson and Waldie, 1978;Suciu and Patrascu, 1977). However, to obtain reliable signals the marked particle had to be made substantially larger and heavier than the other particles in the bed, being 9.5 mm diameter and weighing 0.926 g. Judging from cine-photographic studies by Robinson and Waldie ( 1978) of different sized particles present simultaneously in a spouted bed, it seems likely that such a large particle would not fully represent the behaviour of the predominantly smaller particles in the bed. Mann and Crosby (1975) measured cycle times in a spouted bed with draft tube using a rnagnetised particle and a coil around the top of the draft tube.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Measurement of particle movement in a spouted bed using a new microprocessor based technique

Waldie¹,

Wilkinson²

1986

Self Cite

“…This is corroborated by observations that the more massive component has been found to congregate at the upper inner part of the annulus (Piccinini et al, 1977;Cook and Bridgwater, 1978). Robinson and Waldie (1978) studied segregation in the annulus of a half-section spouted bed by the measurement of cycle time distributions. Larger particles were found to have larger cycle times, but all measurements were taken at the transparent front wall of the half-section bed.…”

Section: Interparticle Percolation In the Annulusmentioning

confidence: 56%

Particle residence times in the continuous spouting of mixtures

Cook

Bridgwater

1985

A magnetic labelling technique has been used to examine particle residence time distributions in a continuous spouted bed. For a single particle species, the nearly perfect mixing observed found by others is confirmed. For a binary particle system, perfect mixing of each component is found, but the mean residence times are not equal. The ratio of mean residence times is found to be dependent on the fountain height and bed depth; the influence of some of the underlying physical mechanisms in the fountain, free surface and outlet regions can be seen.

“…As reported by several workers (Cook and Bridgwater, 1978;Robinson and Waldie, 1978;McNab and Bridgwater, 1979), segregation between particles of different densities or diameters is likely to occur in spouted beds. In those in which the solid is continuously fed in and removed, the initial overflow is composed of a mixture rich in fine particles, whatever, the gas flow rate.…”

Section: Overflow Discharge Compositionmentioning

confidence: 63%

Thick coatings by thermo‐chemical deposition in spouted beds

Piccinini

Rovero

1983

Spouted beds are an established way of coating nuclear fuel microspheres with pyrolytic carbon or silicon carbide by high‐temperature thermochemical reactions. In recent years, similar coatings have aroused particular interest as bio‐compatible materials. This paper describes the differences between these two applications, and the changes that must be made to the coating process and furnace to control both the overall surface of the bed material and its increase in volume. It is shown that a satisfactory control can be achieved by continuous feeding of small particles, followed by the continuous withdrawal of variously coated particles. Experiments on two columns with internal diameter of 0.08 and 0.14 m, respectively, showed that segregation phenomena may occur, depending on the flow dynamics, and that the way in which a steady state is brought about will depend on the position of the discharge pipe in the bed. Les lits “spoutés” constituent un moyen courant pour recouvrir des microsphères de combustible nucléaire de carbone pyrolytique ou de carbure de silicum, en employant des réactions thermochimiques à température élevée. Durant les dernières années, les recouvrements du type précité ont suscité un intérět particulier en raison de leur biocompatibilité.