Variable-angle and variable-curvature fluidizing bed for continuous processes involving changing particles
In a fluidized bed, a fluid stream passes through a bed of solid particles at a velocity high enough to effectively suspend those particles by way of the friction effects on their surfaces. Fluidized beds are widely-used as chemical reactors because they enable homogenous contact between solid and fluid reactants, while allowing mixing of both the fluid stream and the bed of solids. Fluidized beds require careful design to match their diameter and the fluid flow-rate to give the desired fluidizing velocity. For reactions in which the physical properties of the solid particles change, this velocity is not constant and changes as the reaction progresses. For continuous processes, this necessitates new design geometries where the reactor diameter progresses as a function of the progression in particle properties. This will result in a reactor where new particles are fed at the bottom, where the velocity is highest, and then graduate to lower-velocity zones as the reaction progresses and their density decreases. Such a reactor would have a vertical residence time profile. A constriction zone at the top of the reactor could be used as a means of increasing velocity to eject particles, after a desired residence time, through elutriation.