Although coarse, uniformly sized particles are not amenable to fluidization, it has been found possible by use of either gases or liquids to impart a regular cycling motion to a bed of this type of material in which the solids are rapidly carried upward by the fluid in a central well-defined core within the bed. The particles move uniformly downward in the annular space surrounding the core, thus providing dense-phase countercurrent contact between the fluid and the solids. There is no wall separating the core from the annulus. This method is called the spouted-bed technique. The effect of column diameter, fluid inlet diameter, bed depth, and physical properties of solids and fluids on spouting behavior has been investigated. The minimum fluid velocity required for spouting has been correlated, and the flow pattern of the fluid and of the solids has been studied. The technique has been applied to the drying of wheat.

We reviewed 13 patients with a complex fracture-dislocation of the proximal interphalangeal joint of a finger and one patient with a complex fracture-dislocation of the interphalangeal joint of thumb. We had treated these injuries using a pins and rubbers traction system which had been modified to avoid friction of the pins against the bone during mobilisation of the joint in order to minimise the risk of osteolysis. A Michigan hand outcome questionnaire was used for subjective assessment. The active range of movement (AROM) of the proximal and distal interphalangeal joints and the grip strength were used for objective assessment. The mean follow-up was 34 months (12 to 49). The mean normalised Michigan hand outcome score was 84. The mean AROM of the proximal interphalangeal joint was 85 degrees and that of the distal interphalangeal joint 48 degrees. The mean grip strength was 92% of the uninvolved hand. Twelve patients have returned to their original occupations. There has been no radiological osteolysis or clinical osteomyelitis. This modified traction system has given acceptable results with a low rate of complications. It is light, cheap, effective and easy to apply.

Detailed studies of the air and solid flow patterns in a spouted wheat bed have been made in column sizes up to 2 ft. in diameter. Orifice size, cone angle, bed height and air flow were varied so as to establish their effect on these flow patterns. Air flow within the bed was obtained from pressure drop gradients, and solid flow was obtained from particle velocity measurements taken at the wall. Pressure drop, air flow distribution between spout and annulus, solid circulation rate and flow line data are summarized. A correlation is proposed which relates pressure drop and particle velocity at the top of the bed with superficial air velocity at air flows above minimum spouting. Particle velocity measurements in the spout were made from photographs, and were calculated approximately from the drag equation for a single particle.

A two‐region model of a spouted bed, postulating vertical plug flow of gas in the spout and dispersed plug flow along curved streamlines in the annulus, is proposed. The extent of axial dispersion is accounted for by a coefficient D which is an adjustable parameter of the model. Experimental support for the theory is provided by residence time‐distribution data obtained by using helium gas as tracer, covering a wide range of conditions. Values of the coefficient D, determined from a comparison between predicted and observed RTD curves, are generally higher than those reported for packed beds but much smaller than those for fluidized beds.

Stimulus-response experiments have been carried out, using helium gas as tracer, to measure the residence time distribution of gas in spouted beds. The data obtained, under a variety of experimental conditions, are compared against predictions from a two-region gas flow model. The model postulates plug flow of gas in the spout and axially-dispersed plug-flow in the annulus, the extent of axial dispersion being accounted for by a coefficient, D, which is an adjustable parameter of the model. The values of D thus determined were found to increase with gas flow rate, to be relatively insensitive to bed path, and to be much larger for beds of wheat than of polystyrene. hile considerable information exists on the bulk W distribution of gas between the spout and the annulus, smaller scale aspects of flow pattern such as axial or radial mixing, and any localized recirculation of gas, have received little attention. Detailed knowledge of gas flow behavior, though of minor consequence for a solids treatment process such as grain drying, could have an important effect on certain other types of processes like thermo-chemical deposition",P.S' vapor phase r e a~t i o n '~,~' and aerosol collection'O', for which the use of spouted beds has recently attracted attention. Thus, there is a growing need for knowing the gas flow pattern in greater detail. This paper presents the results of stimulus-response experiments carried out with the above objective in view, using helium gas as tracer. The RTD curves obtained for air-spouted beds of wheat and polystyrene granules in a 15 em diameter column are compared against predictions from a theoretical flow model. Deviations are interpreted in terms of an axial dispersion coefficient, and the values of this coefficient, obtained under different spouting conditions, are reported. Theoretical modelWe first present a theoretical model to describe the movement of tracer gas passing through a spouted bed. Since the residence time of gas in the high-velocity spout region is obviously much smaller than in the annulus, the general pattern of gas movement may be represented by a two-region model, with allowance for cross-flow of gas from one region (spout) to the other (annulus). Visual observation in a half-sectional column, using NOy gas as tracer showed gas flow in the upper part of the annulus to be directly upwards, with pronounced radial flow at lower levels (Figure 1). Under certain conditions, back-mixing of gas could On a &udik expkrimentalement les rhctions ? I nn stimulus, en utilisant le gaz hClium comme traceur, pour mesurer la distrubtion du temps de skjour d'un gaz dans les lits fluidisb avec giclage (spouted beds). On a compark les rksultats obtenus dans diffkrentes conditions expkrimentales avec les prkvisions d'un modhle d'koulement gazeux dam deux secteurs. Le modde postule un Ccoulement entravk du gaz dans la g i c k (spout) ainsi qu'un Ccoulement entravk et disperse en direction axiale dans l'anneau; le coefficient D, qui est un paramkre ajustable du modhle, tient compte du de...