Evolution and Flow of Vapors in a Fluidized Bed
Abstract
Vaporization of injected liquid is a key process in many industrial fluidized beds. In Fluid Cokers, for example, quicker vaporization would increase liquid product yield and reduce fouling. A new experimental method was developed to measure the vaporization rate by injecting liquid for a certain duration to reach a constant vaporization rate while monitoring changes in pressure and vapor composition in the exhaust pipe of the fluidization column. Three processes can delay vaporization in a fluidized bed: heat flux from hot-dry particles to wet particles, vapor saturation, and wet agglomerate formation. Operating a spray nozzle at a very high atomization gas flowrate eliminated agglomerate formation, and the heat flux limitation was predominant at bed temperatures well above the boiling point while vapor saturation was predominant at bed temperatures well below the boiling point. Finally, with a practical atomization gas flowrate, bed hydrodynamics and spray characteristics affect agglomerate formation and stability significantly.