Spouting vessel

The spouting vessel is conunonly either cylindrical or conical in shape (Fig. 2). With the former it is preferable to have a short conical base tapering down to the inlet orifice, so that the solids in the annulus can easily slide into the gas jet region without forming any dead zone at the base. Most of the work outside the Soviet Union has been carried out in this type of vessel, while spouting in conical vessels has received particular attention in the Soviet Union, and has been extensively discussed in a book by Romankov and Rashkovskaya (R4). The general discussion of spouted bed behavior in this review is in the context of a cylindrical column. 

Spouted beds are used for coarse particles that do not fluidize well. A single, high velocity gas jet is introduced under the center of a static particulate bed. This jet entrains and conveys a stream of particles up through the bed into the vessel freeboard where the jet expands, loses velocity, and allows the particles to be disentrained. The particles fall back into the bed and gradually move downward with the peripheral mass until reentrained. Particle-gas mixing is less uniform than in a fluid bed. 

Stirring rods. These are made from glass rod 3-5 mm in diameter, cut into suitable lengths. Both ends should be rounded by heating in the Bunsen or blowpipe flame. The length of the stirring rod should be suitable for the size and the shape of the vessel for which it is employed, e.g. for use with a beaker provided with a spout, it should project 3-5 cm beyond the lip when in a resting position. 

If the fluid enters the vessel at one central point, as indicated in Figure 23.3, rather than at many points spaced across a circular distributor, as in Figure 23.1, the action is different as us increases a spouted bed results rather than a fluidized bed. A spouted bed is characterized by a high-velocity spout of gas moving up the center of the bed, carrying particles to the top. This action induces particle circulation, with particle motion toward the wall and downward around the spout and toward the center. The particles in a spouted bed are relatively large and uniformly sized. 

It has been claimed that the magnitude of this stress in some blood vessels is similar to the shear stress at the nozzle of the famous water fountain in Lake Geneva. The fountain spouts 500 litres of water per second with a mean velocity of 200 km/hr which reaches a height of about 140 m the shear stress at the nozzle is about 40 dynes/cm . 

A typical spouted bed has a substantial depth, which in the case of a cylindrical vessel is usually at least of the order of two column diameters, measured from the inlet orifice to the surface of the annulus. If the bed is much shallower, the system becomes hydrodynamically different from true spouting. The situation in this respect is similar to that for gas-fluidized beds, where the generally formulated principles of fluidization are not applicable to very shallow beds. 

Minimum Spouting Velocity Correlations for Conical Vessels (Spouting Fluid-Air)... 

J Iukhlenov and Gorshtein (M16), who also worked with conical vessels, argued that the ratio between the peak pressure drop and the pressure drop at steady spouting should bear a relationship to the geometry of the system, and to the properties of the gas and the solids. Starting with dimensional analysis, they proposed the following empirical correlation ... 

On the basis of experimental results obtained in conical vessels using several sohd materials, Mukhlenov and Gorshtein (M16) reached the conclusion that in a given bed, the spout voidage is substantially constant over the height of the spout. Their explanation of this observed behavior is based on the assumptions that ... 

---