Slump velocity

The lift pipe design was tapered to a larger diameter at the top. This minimized the effects of erosion and catalyst attrition, and also prevented the instantaneous total collapse of circulations when the saltation concentration, or velocity, of solids is experienced (i.e. the slump velocity-that velocity below which particles drop out of the flowing gas stream). In a typical operation, 2 % to 4 % coke can be deposited on the catalyst in the reactor and burned in the regenerator. Catalyst circulation is generally not sufficient to remove all the heat of combustion. This facilitated the need for steam or pressurized water coils to be located in the regeneration zone to remove excess heat. 

Figure 43. Particle accumulation in slumped zone adjacent to active bed air velocity through active region = 151 cm/s air velocity through slumped region = 7.3 cm/s numbers above heater are heat transfer coefficient in W/m2 °C after 15-30 min. (From Glicksman etal., 1992.)...

Viscous flow models have been applied to a variety of problems ranging from slow creep deformations and mud flows to more rapid fluid types of mass movement. Morgenstem (1967) described an early viscous flow analysis in which the soil shear resistance consisted of a velocity-dependent viscous component in addition to Coulomb friction. In his analysis Morgenstem (1967) derived an equation for determining the velocity required to change a slump into a turbidity current as shown in Figure 11.20. This expression is given as follows... 

Velocity profiles for increasing values of time factor (atlbh. (After Morgenstern, N.R., Submarine slumping and the initiation of turbidity currents. In Richards A.R ed. Marine Geotechnique. University of Illinois Press, Champaign, IL, 189-220,1967. Reprinted with permission of Norbert Morgenstern.)... 

The velocity (Vo) of the material in flow at the fluid-air interface and the resulting sag or slump length (S) can be calculated for a fluid of index n ... 

The bulk velocity distribution in the active layer does not change with addition of fines and the bed behavior (e.g., rolling, slumping, etc.) remains unchanged with fines (Henein, 1980). 

In this article, landslide is used as a generic term to include all types of downslope movement of earth material, including types of movement that involve little or no true sliding. Thus, rock falls, debris flows, etc., are considered types of landslides. The classification system of Vames (1978) is used, which categorizes landslides by the type of material involved (soil or rock) and by the type of movement (falls, topples, slides, slumps, flows, or spreads). Other modifiers commonly are used to indicate velocity of movement, degree of internal disruption, state of activity, and moisture content. 

It has also been found that core slump could produce high velocities of the carrier steam inside pipes, making it possible the mechanical resuspension of deposited aerosols on surfaces from both volatile fission products and more refractory core materials. This phenomenon has not yet been considered in NELCOR. 

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