Liquid atomization into gas–solid fluidized beds—A review spanning the micro- to macro-scale

Abstract

Fluid catalytic cracking, olefin polymerization, granulation and coating inject liquid into gas–solid fluidized beds. Liquid injection forms bridges between particles, which forms agglomerates. Both liquid bridges and liquid evaporation disturb bed hydrodynamics, mass and heat transfer, process performance, and fluidized bed stability. Characterizing these phenomena from the particle and droplet scale (micro) to the level of the gross internal solids circulation (macro scale) increases the confidence deriving kinetic rate expressions as well as scaling-up. This review article focuses on spray atomization and describes various technologies that analyze and characterize these processes. Researchers have published work with nozzles ranging from 1.6-25mm in diameter and generally rely on the Weber number and Reynolds number to achieve the desired droplet diameter and droplet velocity. Although thermal stability is a criterion to maximize yield and selectivity, atomizing liquid at the nozzle tip introduces substantial heterogeneity that propagates throughout reactor, and thus compromises performance.