Spouting minimum velocity

As in the case of fluidization, there is a gas velocity below which spouting does not occur. The earliest and best known relationship to predict the minimum spouting velocity u s is that due to Mathur and Gishler (1955)... 

The minimum spouting velocity is determined, as a function of the geometrical parameters of the particle-reactor system [8] ... 

Reynolds number at the minimum spouting velocity time and average cycle time (s) gas velocity and gas velocity at the minimum spouting (ms-1)... 

Spouting cannot be maintained once the bed height exceeds a certain level, coim monly known as maximum spoutable bed depth, Hm. At Hm, the spout starts to collapse and the bed starts to change from a spouted bed to a fluidized bed. As indicated in Eq. (9.67), the minimum spouting velocity increases with an increase in the bed height. Consequently, (7msp achieves its maximum at Hm. The maximum value of the minimum spouting velocity can be related to the minimum fluidization velocity by... 

Minimum Spouting Velocity and Pressure Drop in Spouted Beds. Can. J. Chem. Eng.,... 

Thus, the minimum spouting velocity for a given material, column size, inlet size, and bed depth can be obtained by combining Eqs. (7)-(10). Calculation by this method is valid for H/D greater than 1, Rem of 10-100, and Di/Dc less than 0.1. 

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

In summaxy, then, the simplest and most reliable method for estimating the minimum spouting velocity for common materials over a wide range of practical conditions is by use of Eq. (3), provided that in the case of mixed-size particles the reciprocal mean diameter is employed. The equation has been validated for column diameters up to 2 ft, not only for wheat but also for a coarse grade of ammonium nitrate (12), but industrial data for larger units have unfortunately not been released. 

Investigator Type of correlation Phases involved Mathur and Gishler [21] Minimum spouting velocity prediction Gas-solid... 

For fine grains (Ar < 10 ), the bed becomes unstable and may pulsate with a frequency at a low amplitude. It is found that the dryer height H and separator diameter also affect the minimum spouting velocity. These effects are included in the correlation... 

At a depth just above the maximum spoutable, a spouted bed changes into a fluidized state. Therefore, if the minimum fluidization velocity for a solid material is known, its maximum spoutable bed depth in a given column can be estimated by substituting for u s ir> the minimum spouting velocity equation. A general expression for the maximum spoutable bed depth is given as follows ... 

According to Epstein and Grace (1997), the Mathur-Gishler equation shown below remains the simplest equation to estimate the minimum spouting velocity, good to 15% for cylindrical vessels up to about 0.5 m. For Z) < 0.5 m... 

The maximum value of the minimum spouting velocity, occurs when the bed height is at the maximum spoutable bed depth or... 

A comprehensive review of correlations proposed for the minimum spouting velocity can be found in Mathur and Epstein (1974). A general correlation for the minimum spouting velocity was also suggested by Littman and Morgan (1983). 

The minimum spouting velocity has been shown by King and Harrison (1980) to decrease markedly with increasing pressure up to 20 bar. A modified version of the Mathus and Gishler correlation, shown in Eq. (1), was proposed by King and Harrison (1980) as... 

For single particle size in a rectangular spouted bed, Anabtawi et al. (1992) showed that the minimum spouting velocity had little difference compared to that in cylindrical beds predictable within the variations from different correlations available for cylindrical beds. A dimensionless correlation for predicting the minimum spouting velocity in a rectangular spouted bed with a mixture of binary particle sizes was recently proposed by Anabtawi (1998). 

AP2-3 = pressure drop between 2 and 3 (see Fig. 5) Hmft = minimum spouting velocity... 

Anabtawi MZ. Minimum spouting velocity for binary mixture of particles in rectangular spouted beds. Can J Chem Eng 76 132-136, 1998. 

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