Fluidized particle formulation

General Principles of Particle Formulation in Spray Fluidized Beds... 

The previous discussion pointed out that various material properties have a more or less strong influence on particle formulation in spray fluidized beds. Process conditions, such as the spraying rate, gas temperature, or the mass flow rate of the fluidization gas, can also very significantly affect the properties of the resulting particles. This aspect will be illustrated in the present section by means of selected examples. 

Chapter 5 Understanding and preventing structural changes during drying of gels Chapter 6 Morphology and properties of spray-dried particles Chapter 7 Particle formulation in spray fluidized beds... 

In the preceding chapters we first considered the primary forces acting on a fluidized particle in a bed in equilibrium, and then the elastic forces between particles that come into play under non-equilibrium conditions. These two effects provide closure for the particle bed model, formulated in terms of the particle-and fluid-phase conservation equations for mass and momentum. Up to now, applications have focused on the stability of the state of homogeneous particle suspension, in particular for gas-fluidized systems for which the condition that particle density is much greater than fluid density enables the particle-phase equations to be decoupled and treated independently. The analysis has involved solely the linearized forms of these equations, and has led to a stability criterion that broadly characterizes fluidized systems according to three manifestations of the fluidized state always stable - the usual case for liquids always unstable - the usual case for gases and transitional behaviour - involving a switch, at a critical fluid flux, from the stable to the unstable condition. This characterization has... 

The one-dimensional particle bed model has been formulated in terms of the primary fluid-particle interaction forces, which alone may be considered to support a fluidized particle under steady-state equilibrium conditions, together with particle-phase elasticity, which provides a force proportional to void fraction gradient (or particle concentration gradient) and so comes into play under non-equilibrium conditions. Only axial components of these interactions have been considered so far. Generalizing these considerations to encompass lateral force components is a straightforward matter, but, as we now see, calls for some modification in the constitutive relation for drag in order to unify the axial and lateral constitutive expressions. The following derivations are expressed in terms of volumetric particle concentration a rather than void fraction e a= - . 

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